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Uncovering phonological and orthographic selectivity across the reading network using fMRI-RA
Abstract
Reading has been shown to rely on a dorsal brain circuit involving the temporoparietal cortex (TPC) for grapheme-to-phoneme conversion of novel words (Pugh et al., 2001), and a ventral stream involving left occipitotemporal cortex (OTC) (in particular in the so-called “visual word form area”, VWFA) for visual identification of familiar words. In addition, portions of the inferior frontal cortex (IFC) have been posited to be an output of the dorsal reading pathway involved in phonology. While this dorsal versus ventral dichotomy for phonological and orthographic processing of words is widely accepted, it is not known if these brain areas are actually strictly sensitive to orthographic or phonological information. Using an fMRI rapid adaptation technique we probed the selectivity of the TPC, OTC, and IFC to orthographic and phonological features during single word reading. We found in two independent experiments using different task conditions in adult normal readers, that the TPC is exclusively sensitive to phonology and the VWFA in the OTC is exclusively sensitive to orthography. The dorsal IFC (BA 44), however, showed orthographic but not phonological selectivity. These results support the theory that reading involves a specific phonological-based temporoparietal region and a specific orthographic-based ventral occipitotemporal region. The dorsal IFC, however, was not sensitive to phonological processing, suggesting a more complex role for this region.
... Two routes, the phonological and the lexical, are responsible for the acquisition and development of reading [1][2][3][4]. Proficient reading is only reached when decoding is automatized and when cognitive and metacognitive mechanisms are available to enable the understanding of the decoded material [5][6][7]. The phonological route uses the grapheme-phoneme conversion process, translating letters or groups of letters into phonemes, through the application of grapheme-phonemic rules. ...
... In contrast, in the lexical route, pronunciation is not constructed segment by segment, but retrieved as a whole from the orthographic lexicon. However, the lexical route is used only when the item to be read has its orthographic representation pre-stored in the orthographic lexicon, that is, it was acquired through the phonological route [1][2][3][5][6][7]. Thus, development and automating of decoding process is fundamental for literacy [5][6][7]. ...
... However, the lexical route is used only when the item to be read has its orthographic representation pre-stored in the orthographic lexicon, that is, it was acquired through the phonological route [1][2][3][5][6][7]. Thus, development and automating of decoding process is fundamental for literacy [5][6][7]. ...
Decoding skills are crucial for literacy development and they tend to be acquired early in transparent languages, such as Brazilian Portuguese. It is essential to better understand which variables may affect the decoding process. In this study, we investigated the processes of decoding as a function of age of children who are exposed to a transparent language. To this end, we examined the effects of grade, stimulus type and stimulus extension on the decoding accuracy of children between the ages of six and 10 years who are monolingual speakers of Brazilian Portuguese. The study included 250 children, enrolled from the first to the fifth grade. A list of words and pseudowords of variable length was created, based on Brazilian Portuguese structure. Children assessment was conducted using the computer program E-prime® which was used to present the stimuli. The stimuli were programmed to appear on the screen in a random order and children were instructed to read them. The results indicate two important moments for decoding: the acquisition and the mastery of decoding skills. Additionally, the results highlight an important effect of the extent and type of stimuli and how it interacts with the school progress. Moreover, data indicate the multifactorial nature of decoding acquisition and the different interactions between variables that can influence this process. We discuss medium- and long-term implications of it, and possible individual and collective actions which can improve this process.
... In addition to associating letters with sounds, readers also draw upon their visual experiences to represent orthographic units with the help of the left ventral occipitotemporal cortex, theorized as the "visual word form area" or VWFA (Dehaene & Cohen, 2011;McCandliss et al., 2003). Through the retrieval of orthographic whole-word representations, frequently encountered words are processed without the need for phonological processing (Glezer et al., 2016;Ludersdorfer et al., 2015). Functional specialization within this area emerges 6 NEUROIMAGING STUDIES OF PHONOLOGY AND WORD READING: A REVIEW with early reading acquisition. ...
... Young readers use more of the left temporo-parietal circuit involved with phonology-based reading, whereas adults use more whole-word recognition processes (Martin et al., 2015;Sela et al., 2014;Shaywitz et al., 2007). In their meta-analysis of reading and neuroimaging, Martin et al. (2015) show how, with advanced literacy in adults, there is greater activation in the occipitotemporal cortex when compared to children, who show significantly more activation in the left superior temporal gyrus, suggesting that for emergent readers, grapheme-to-phoneme mapping is fundamental (Glezer et al., 2016). Longitudinal studies have provided insights into reading network development (Horowitz-Kraus et al., 2015;Marosi et al., 1997). ...
... The dorsal route is involved in word decoding (Fiez & Petersen, 1998;Jobard et al., 2011) and access to phonemes (Wu et al., 2012), phonological decision-making (Rumsey et al., 1997) and phonological output (Taylor, et al. 2012). The ventral route is a memory-based word form area supporting fluent word identification (Pugh et al., 2001;Glezer et al., 2016). The ventral route is engaged with orthographic representations, how words are represented by letter strings, and is finely tuned to read whole words (Glezer et al., 2016). ...
With the advancement in brain research, neuroscience researchers have been able to collectively inform our understanding of reading-related processes. Despite an extensive body of literature, many educators are not aware of specific neuroimaging findings related to phonological processing and word reading. Therefore, this integrative review seeks to disseminate this information to an audience of educators. Findings discussed in this review include early reading development, the reading network, and developing models of the reading processes from a neuroscience perspective. This integrative review will contribute to educators' understanding of brain connectivity in relation to phonological processing and word reading ability. An enhanced understanding of neural connectivity and reading will lay the foundation for a deeper dialogue among reading theory, policy, classroom instruction, and brain research.
... In addition to associating letters with sounds, readers also draw upon their visual experiences to represent orthographic units with the help of the left ventral occipitotemporal cortex, theorized as the "visual word form area" or VWFA (Dehaene & Cohen, 2011;McCandliss et al., 2003). Through the retrieval of orthographic whole-word representations, frequently encountered words are processed without the need for phonological processing (Glezer et al., 2016;Ludersdorfer et al., 2015). Functional specialization within the VWFA emerges with early reading acquisition. ...
... The dorsal route is critical for extracting relations between orthography, phonological form, morphological, and lexical-semantic dimensions of print. The ventral route is a memory-based word form area supporting fluent word identification (Pugh et al., 2001;Glezer et al., 2016). The dorsal route is 7 involved in word decoding (Fiez & Petersen, 1998;Jobard et al., 2003) and access to phonemes (Wu et al., 2012), phonological decision-making (Rumsey et al., 1997) and phonological output (Taylor, et al. 2012). ...
... The dorsal route is 7 involved in word decoding (Fiez & Petersen, 1998;Jobard et al., 2003) and access to phonemes (Wu et al., 2012), phonological decision-making (Rumsey et al., 1997) and phonological output (Taylor, et al. 2012). The ventral route is engaged with orthographic representations, how words are represented by letter strings, and is finely tuned to read whole words (Glezer et al., 2016). ...
With advancement in brain research, neuroscience researchers have collectively informed our understanding of reading-related processes. Despite an extensive body of literature, many educators are not aware of specific neuroimaging findings related to phonological processing and word reading. Therefore, the study builds on this body of research by exploring the connection between the brain and reading scores. Quantitative EEG and standardized academic achievement analyses were performed on 60 school-aged children. Intrahemispheric coherence analysis at rest were conducted across the sample of participants and several coherence networks were extracted and compared to standardized reading achievement scores. Specifically, networks that included Brodmann area 44 and 45 (Brocas Area-associated with reading) whose coherence values were significantly correlated with standardized reading scores were examined. Results indicate total of five coherence networks across the two brain hemispheres, that are correlated with reading achievement scores in children. In addition to Brodmann area 44 and 45, these coherence networks include BAs in the left frontoparietal lobe, right occipitotemporal lobe, left temporoparietal lobe, and the right occipital lobe. This dissertation seeks to disseminate this information to an audience of educators. Findings discussed in this dissertation include the QEEG coherence patterns specifically associated with letter word identification, reading fluency, passage comprehension, and broad reading scores measured by the Woodcock Johnson III Test of Achievement contributing to educators' understanding of brain connectivity in relation to reading performance.
... By virtue of their inherent orthographic similarity, embedded words and a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 semantic processing underlying word recognition. For example, using an fMRI repetition suppression paradigm similar to that adopted here, Glezer et al. [36] showed that the left IFG was associated with release of fMRI repetition suppression (i.e. an absence of suppression due to change) for homophones and different words as compared to repeated words, indicating a sensitivity to orthography in the left IFG. Another fMRI study by Purcell, Jiang, & Eden [37] also found that the left IFG is sensitive to orthography and works together with left vOT during reading and spelling. ...
... The same contrast was also used to define the ROI of left IFG for 10 out of 11 observers, and the Word > Fixation contrast was used to identify the left IFG for the last observer who did not show any activation in the left IFG using the Word > Scrambled image contrast. The left IFG was constrained to correspond the location of the left IFG which was known for orthographic processing [36,37]. ...
... ± 5.4, y = 3.9 ± 5.7, z = 28.5 ± 3.3 (Table 2). This result was consistent with the location of the left IFG from the whole-brain analyses (Table 1) and also close to the location reported in previous studies [36,37]. Fig 3B shows the BOLD percent signal change in the left IFG from Experiment 1. Similar to the VWFA, a two-way repeated measures ANVOA was performed, and the results revealed a main effect of embeddedness, F(1, 10) = 6.11, p = 0.033. ...
Lexical embedding is common in all languages and elicits mutual orthographic interference between an embedded word and its carrier. The neural basis of such interference remains unknown. We employed a novel fMRI prime-target embedded word paradigm to test for involvement of a visual word form area (VWFA) in left ventral occipitotemporal cortex in co-activation of embedded words and their carriers. Based on the results of related fMRI studies we predicted either enhancement or suppression of fMRI responses to embedded words initially viewed as primes, and repeated in the context of target carrier words. Our results clearly showed enhancement of fMRI responses in the VWFA to embedded-carrier word pairs as compared to unrelated prime-target pairs. In contrast to non-visual language-related areas (e.g., left inferior frontal gyrus), enhanced fMRI responses did not occur in the VWFA when embedded-carrier word pairs were restricted to the left visual hemifield. Our finding of fMRI enhancement in the VWFA is novel evidence of its involvement in representational rivalry between orthographically similar words, and the co-activation of embedded words and their carriers.
... These studies provide evidence for a hierarchical organization in the ventral visual OT pathway for visual word form, leading to the proposal that, running posteriorly to anteriorly along this pathway, neurons are tuned to increasingly complex word features, namely from oriented bars, to letters, bigrams, and finally to quadragrams (Cohen and Dehaene, 2004;Vinckier et al., 2007). Glezer et al. (2009Glezer et al. ( , 2015Glezer et al. ( , 2016 provided evidence that an area within the ventral OT (vOT) region, the so-called visual word form area (VWFA), appears to function like an orthographic lexicon. Neurons in this part of the brain seem to be specialized to process written words we have learned, and not novel words. ...
... However, the exact nature of the representations processed in these areas during word reading is still unclear. Recently, Glezer et al. (2016) showed that a region within the TPC appears to be finely tuned to phonological features during single word reading in typical hearing readers, and that this same region shows weak selectivity to phonological features in people with dyslexia (Glezer et al., 2018). These findings suggest that a region within the TPC does indeed engage in phonological processing during word reading, and moreover, that it shows altered tuning in hearing people with reading difficulties. ...
... Furthermore, as the technique exploits adaptation effects at the neuronal level, its spatial resolution is not limited by the voxel resolution (Krekelberg et al., 2006). Glezer et al. (2009Glezer et al. ( , 2015Glezer et al. ( , 2016 recently showed that this technique can be used to probe neuronal tuning for single-word reading at a level beyond what is possible by comparing the average BOLD-contrast level response to individually presented stimuli. ...
... Among those regions, the left dorsal brain circuit including the temporoparietal cortex and dorsal inferior frontal gyrus is widely considered to be core regions for phonological processing of alphabetic words (Hickok, 2012;Zuk et al., 2018;Oron et al., 2016;Vigneau et al., 2006). The left temporoparietal cortex (i.e., the posterior superior temporal gyrus and supramarginal gyrus) is thought to be responsible for grapheme-to-phoneme conversion in alphabetic word reading (Glezer et al., 2016;Price, 2012;Pugh et al., 2001). In contrast, the left ventral inferior frontal gyrus and the inferior and middle temporal gyrus are thought to be related to semantic processing during word reading (Binder et al., 2009;Booth et al., 2006;Gesa et al., 2016;Jana & Gesa, 2019;Katzev et al., 2013;Miozzo et al., 2017;Price, 2000;Pugh et al., 2005). ...
... Within the left temporoparietal cortex, our study found that only the left posterior STG showed significant correlation between the neural DSM and rating-based phonological DSM, neither the left STG nor the left SMG showed significant correlations with the modelbased phonological DSM. The left temporoparietal cortex is thought to be responsible for grapheme-to-phoneme conversion (Glezer et al., 2016;Price, 2012;Pugh et al., 2001). Because reading Chinese characters relative to alphabetic words relies less on grapheme-tophoneme conversion Tan et al., 2005), the left temporoparietal cortex has been found to be less involved in phonological processing of Chinese characters (Bolger et al., 2005;Brennan et al., 2013;Cao et al., 2009;Oberhuber et al., 2016;Tan et al., 2003Tan et al., , 2005Wu et al., 2012;Zhu et al., 2014). ...
Previous studies have revealed that phonological processing of Chinese characters elicited activation in the left prefrontal cortex, bilateral parietal cortex, and occipitotemporal regions. However, it is controversial what role the left middle frontal gyrus plays in Chinese character reading, and whether the core regions (e.g., the left superior temporal gyrus and supramarginal gyrus) for phonological processing of alphabetic languages are also involved in Chinese character reading. To address these questions, the present study used both univariate and multivariate analysis (i.e., representational similarity analysis, RSA) to explore neural representations of phonological information during Chinese character reading. Participants were scanned while performing a reading aloud task. Univariate activation analysis revealed a widely distributed network for word reading, including the bilateral inferior frontal gyrus, middle frontal gyrus, lateral temporal cortex, and occipitotemporal cortex. More importantly, RSA showed that the left prefrontal (i.e., the left middle frontal gyrus and left inferior frontal gyrus) and bilateral occipitotemporal areas (i.e., the left inferior and middle temporal gyrus and bilateral fusiform gyrus) represented phonological information of Chinese characters. These results confirmed the importance of the left middle frontal gyrus and regions in ventral pathway in representing phonological information of Chinese characters.
... It was hypothesized that the connections between the left inferior parietal lobe, which encloses the angular gyrus, which has been assumed to integrate orthography and phonology [218] and the fusiform gyrus may be impaired in dyslexic readers. The function of the fusiform gyrus may also be impaired in dyslexic readers, and the left fusiform gyrus may have a weaker modulatory effect on the left inferior parietal lobule (containing the angular gyrus, the inferior parietal sulcus, and the supramarginal gyrus) in children with reading difficulties compared to controls [258][259][260][261]. This may be interpreted as a deficit in integrateing graphemes and phonemes. ...
... The VWFA and the inferior frontal gyrus were more strongly activated by words that were orthographically different, but phonologically identical, than by words that were orthographically and phonologically identical. The authors concluded that the temporoparietal cortex is involved in phonological processing, and that the VWFA was involved in orthographic processing [261]. ...
It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which readers have difficulty associating graphemes with their corresponding phonemes. In contrast, the magnocellular theory of dyslexia assumes that DD is a visual disorder caused by dysfunctional magnocellular neural pathways. The review explores arguments for and against these theories. Recent results have shown that DD is caused by (1) a reduced ability to simultaneously recognize sequences of letters that make up words, (2) longer fixation times required to simultaneously recognize strings of letters, and (3) amplitudes of saccades that do not match the number of simultaneously recognized letters. It was shown that pseudowords that could not be recognized simultaneously were recognized almost without errors when the fixation time was extended. However, there is an individual maximum number of letters that each reader with DD can recognize simultaneously. Findings on the neurobiological basis of temporal summation have shown that a necessary prolongation of fixation times is due to impaired processing mechanisms of the visual system, presumably involving magnocells and parvocells. An area in the mid-fusiform gyrus also appears to play a significant role in the ability to simultaneously recognize words and pseudowords. The results also contradict the assumption that DD is due to a lack of eye movement control. The present research does not support the assumption that DD is caused by a phonological disorder but shows that DD is due to a visual processing dysfunction.
... The left OT area, including the middle occipital gyrus (MOG), inferior temporal gyrus (ITG) and fusiform gyrus, has been consistently found to show reduced activation in individuals with DD across morpho-syllabic and alphabetic languages (Bolger et al., 2008;Cao et al., 2020;Centanni et al., 2019;Chyl et al., 2019;Paz-Alonso et al., 2018). This region is associated with visuo-orthographic processing during reading (Glezer et al., 2016;Glezer et al., 2019). The left inferior frontal cortex is further subdivided into the inferior frontal gyrus (IFG) and the precentral gyrus (Richlan, 2014). ...
... The main reason was that there was no structural alteration but only functional reduction at this area. The OT area is a key region for orthographic recognition during visual word processing (Glezer et al., 2009;Glezer et al., 2016;Hirshorn et al., 2016;Nobre et al., 1994) and was reported to be impaired in Table 8. Multimodal structural and functional abnormalities in individuals with DD in morpho-syllabic languages. ...
Brain abnormalities in the reading network have been repeatedly reported in individuals with developmental dyslexia (DD); however, it is still not totally understood where and why the structural and functional abnormalities are consistent/inconsistent across languages. In the current multimodal meta-analysis, we found convergent structural and functional alterations in the left superior temporal gyrus across languages, suggesting a neural signature of DD. We found greater reduction in grey matter volume and brain activation in the left inferior frontal gyrus in morpho-syllabic languages (e.g. Chinese) than in alphabetic languages, and greater reduction in brain activation in the left middle temporal gyrus and fusiform gyrus in alphabetic languages than in morpho-syllabic languages. These language differences are explained as consequences of being DD while learning a specific language. In addition, we also found brain regions that showed increased grey matter volume and brain activation, presumably suggesting compensations and brain regions that showed inconsistent alterations in brain structure and function. Our study provides important insights about the etiology of DD from a cross-linguistic perspective with considerations of consistency/inconsistency between structural and functional alterations.
... Temporal activations were observed in the blind subjects only during spoken words processing but were not active during reading ( Fig 2 and Fig. 4 ). In the sighted population, MTG/STG region is involved in phonological and semantic processing ( Price, 2012, Glezer et al., 2016 and multimodal integration of linguistic stimuli ( Hickok & Poeppel, 2007 ). The temporal cortex was also shown to be involved in phonological and semantic processing of spoken stimuli in the blind ( Burton et al., 2003, Arnaud et al., 2013. ...
... The left vOT was repeatedly shown to be active during Braille reading Friston, 1998 , Sadato et al., 1998 ) displaying evidence for orthographic repetition suppression ( R ączy et al., 2019 ) similar to that observed in the sighted population ( Glezer et al., 2016 ). This was considered a proof for selective specialization for written language processing and an argument for assigning the role of orthographic representation storage to this region. ...
All writing systems represent units of spoken language. Studies on the neural correlates of reading in different languages show that this skill relies on access to brain areas dedicated to speech processing. Speech-reading convergence onto a common perisylvian network is therefore considered universal among different writing systems. Using fMRI, we test whether this holds true also for tactile Braille reading in the blind. The neural networks for Braille and visual reading overlapped in the left ventral occipitotemporal (vOT) cortex. Even though we showed similar perisylvian specialization for speech in both groups, blind subjects did not engage this speech system for reading. In contrast to the sighted, speech-reading convergence in the blind was absent in the perisylvian network. Instead, the blind engaged vOT not only in reading but also in speech processing. The involvement of the vOT in speech processing and its engagement in reading in the blind suggests that vOT is included in a modality independent language network in the blind, also evidenced by functional connectivity results. The analysis of individual speech-reading convergence suggests that there may be segregated neuronal populations in the vOT for speech processing and reading in the blind.
... In fact, when MacSweeney, Brammer, Waters, and Goswami (2009) compared subsets of deaf and hearing participants who performed similarly on a rhyme judgment task (using picture, rather than word stimuli), no activation differences within parietal cortex were observed between groups. Glezer et al. (2016) found that for typical hearing readers, a region within the TPC is finely tuned to phonological representations when they are reading single words, but this region shows only weak selectivity to phonology in skilled deaf readers (Glezer et al., 2018). Glezer et al. (2018) functionally localized a region within TPC that was active when deaf readers made phonological decisions about words (rhyme judgments) and then used the rapid adaptation paradigm to determine whether homophones ( pane-pain) showed the same degree of adaptation as repeated words (pain-pain), as found in hearing readers. ...
... The fMRI-RA study by Glezer et al. (2018) revealed that skilled deaf readers exhibited the same response profile in left IFC as typical hearing readers from Glezer et al. (2016). Both groups showed selectivity to whole written words with no adaptation for homophones, which indicates that this region is more responsive to orthographic than to phonological structure. ...
Recent neuroimaging and electrophysiological evidence reveal how the reading system successfully adapts when phonological codes are relatively coarse-grained due to reduced auditory input during development. New evidence suggests that the optimal end-state for the reading system may differ for deaf versus hearing adults and indicates that certain neural patterns that are maladaptive for hearing readers may be beneficial for deaf readers. This chapter focuses on deaf adults who are signers and have achieved reading success. Although the left-hemisphere dominant reading circuit is largely similar, skilled deaf readers exhibit a more bilateral neural response to written words and sentences compared to their hearing peers, as measured by event-related potentials and functional magnetic resonance imaging. Skilled deaf readers may also rely more on neural regions involved in semantic processing compared to hearing readers. Overall, emerging evidence indicates that the neural markers for reading skill may differ for deaf and hearing adults.
... Familiar versus unfamiliar recognition is of interest in the field of face processing, and its expert role in the visual system [22,46,47]. The holistic and features segmentation approaches have been ...
... Familiar versus unfamiliar recognition is of interest in the field of face processing, and its expert role in the visual system [22,46,47]. The holistic and features segmentation approaches have been described for both face and word recognition, suggesting the need for more research in terms of holistic versus feature perspective in the visual process as a continuum (and not only in isolated steps such as the perceptual, attentional or decisional one). ...
Face recognition is a crucial subject for public health, as socialization is one of the main characteristics for full citizenship. However, good recognizers would be distinguished, not only by the number of faces they discriminate but also by the number of rejected stimuli as unfamiliar. When it comes to face recognition, it is important to remember that position, to some extent, would not entail a high cognitive cost, unlike other processes in similar areas of the brain. The aim of this paper was to examine participant’s recognition profiles according to face position. For this reason, a recognition task was carried out by employing the Karolinska Directed Emotional Faces. Reaction times and accuracy were employed as dependent variables and a cluster analysis was carried out. A total of two profiles were identified in participants’ performance, which differ in position in terms of reaction times but not accuracy. The results can be described as follows: first, it is possible to identify performance profiles in visual recognition of faces that differ in position in terms of reaction times, not accuracy; secondly, results suggest a bias towards the left. At the applied level, this could be of interest with a view to conducting training programs in face recognition.
... Ces résultats font penser aux données rapportées chez les lecteurs dyslexiques, pour lesquels le déficit phonologique semble être prédominant Saksida et al., 2016). Cloutman, 2013;Cohen and Dehaene, 2009;Glezer et al., 2016;Pugh et al., 2001; (Riesenhuber and Poggioa, 1999). Pour la reconnaissance des lettres, une des premières étapes de traitement est l'identification des traits et de l'orientation des traits les composant. ...
... ). La voie ventrale est sollicitée pour le traitement orthographique et lexical alors que la voie dorsale est majoritairement sollicitée pour le traitement phonologique ainsi que le traitement de stimuli nécessitant un grand nombre de ressources attentionnelles (e.g. mots présentés dans un format inhabituel)(Glezer et al., 2016; mais voir Zhao et al., 2016). Dans les premières années d'apprentissage de la lecture il a été observé que les lecteurs sollicitent en majorité la voie dorsale pour l'apprentissage des correspondances lettres-sons et pour les processus attentionnels nécessaires durant la lecture.Une fois ces correspondances acquises, la voie dorsale serait sollicitée pour traiter les pseudomots ou des mots présentés dans un format dégradé (e.g. ...
Les patients souffrant de schizophrénie présentent des symptômes cliniques ainsi que des déficits cognitifs. Il a été récemment proposé que les déficits de lecture des patients fassent partie de ces déficits. L’objectif de ce travail de thèse était d’évaluer les capacités de reconnaissance visuelle des mots chez les patients souffrant de schizophrénie, au moyen d'une évaluation diagnostique des processus cognitifs dans une approche comportementale et électrophysiologique (enregistrement des potentiels évoqués). Les résultats indiquent une préservation de la spécialisation de l’aire de la forme visuelle des mots pour traiter les mots écrits chez les patients. De plus, les processus cognitifs impliqués dans le traitement orthographique des suites de lettres semblent également préservés. En revanche, les processus cognitifs impliqués dans le traitement phonologique semblent altérés chez les patients souffrant de schizophrénie.
... The neuroanatomical circuits associated with processing these four types of information in single-word reading have been systematically linked to functionally separable brain regions (e.g., Price, 2012;Welcome and Joanisse, 2012). While sublexical and orthographic processes are mainly associated with activation in left inferior and middle occipital gyri (IOG and MOG, respectively) and a left ventral occipito-temporal circuit (vOT), phonological and lexico-semantic processes appear to additionally recruit left inferior parietal, lateral temporal and bilateral frontal systems (e.g., Jobard et al., 2003;Price, 2012;Welcome and Joanisse, 2012;Schurz et al., 2014;Braun et al., 2015;McNorgan et al., 2015;Cavalli et al., 2016;Glezer et al., 2016). ...
... In contrast to sublexical, orthographic and phonological processing, we observed age-related differences only at the lexicosemantic processing stage in the (right) IFG. The role of the IFG for language-related processes has among others been attributed to phonological output (Taylor et al., 2013), grapheme-phoneme-conversion (Jobard et al., 2003), orthographic selectivity (Glezer et al., 2016) as well as semantic processing (e.g., Poldrack et al., 1999;Binder et al., 2009) and has been shown to be functionally connected to vOT (Schurz et al., 2014). Since no age-related differences in IFG were detected for orthographic and phonological processing and since the engagement of especially the right IFG in semantic tasks has been ascribed to the involvement of executive functions (Vigneau et al., 2009), the overrecruitment of this region might indicate the involvement of executive control functions in support of successful word recognition in the elderly. ...
Reading is not only one of the most appreciated leisure activities of the elderly but it clearly helps older people to maintain functional independence, which has a significant impact on life quality. Yet, very little is known about how aging affects the neural circuits of the processes that underlie skilled reading. Therefore, the aim of the present study was to systematically investigate the neural correlates of sublexical, orthographic, phonological and lexico-semantic processing in the aging brain. Using functional magnetic resonance imaging, we recorded brain activity of younger (N = 20; 22-35 years) and older (N = 38; 65-76 years) adults during letter identification, visual lexical decision, phonological decision and semantic categorization. Older and younger adults recruited an identical set of reading-related brain regions suggesting that the general architecture of the reading network is preserved across the lifespan. However, we also observed age-related differences in brain activity in the subcomponents of the reading network. Age-related differences were most prominent during phonological and orthographic processing possibly due to a failure of older adults to inhibit non-optimal reading strategies. Neural effects of aging were also observed outside reading-related circuits, especially in frontal midline regions. These regions might be involved because of their important role in memory, attention and executive control functions and their potential role in resting state networks.
... Calculating word onsets: Word onsets of stimuli (first word in a sentence or a scrambled word list) were identified using AlignTool 8,9 . ...
Several studies have shown that the visual word form area (VWFA) contains lexical representations for written words (Glezer et al., Neuron, 2009; Kronbichler et al., Neuroimage, 2004; Lochy et al., PNAS, 2018). However, it is unclear how the VWFA develops such representations. One possibility is that the VWFA receives a top-down 'teaching signal' from auditory lexical representations as words are read, such as from an auditory word form area (AWFA) in the anterior superior temporal gyrus, which has recently been argued to be the auditory analogue of the VWFA, with lexical representations for auditory words (DeWitt & Rauschecker, PNAS, 2012; Damera et al., Soc Neurobiol Lang, 2019). Here, we tested this hypothesis by measuring activation in and functional connectivity (FC) between individually-defined (N=18) AWFA and VWFA ROI during the processing of visual and auditory words. Supporting our hypothesis, we found that the VWFA responded selectively to auditory words (whereas the AWFA did not respond to written words), and strong FC between AWFA and VWFA for auditory, but not written words. In addition, we re-analyzed MEG data from a large database (MOUS; Schoffelen et al., Sci Data, 2019) and used beamforming to calculate signal coherence between AWFA and VWFA, defined as spherical ROI around average coordinates from the literature. This analysis identified significant coherence between the VWFA and AWFA starting 300 ms after auditory word onset. These results support a model in which the AWFA provides a teaching signal to develop the written word lexicon in the VWFA.
... How visual words are processed in the brain is a fundamental question in cognitive neuroscience of language. Extensive neuroimaging research has consistently identified the crucial involvement of the left ventral occipitotemporal cortex regardless of the writing systems in visual word processing (Dong et al., 2021;Feng et al., 2020;Glezer et al., 2016;Li et al., 2019;Ludersdorfer et al., 2016;Martin et al., 2016;Richlan, 2014). Regarding the function of the left ventral occipitemporal cortex, Dehaene and colleagues proposed the visual word form area (VWFA) hypothesis, which claims that the left middle fusiform gyrus is specialized for orthographic processing (Cohen et al., 2000). ...
As a key area in word reading, the left ventral occipitotemporal cortex is proposed for abstract orthographic processing, and its middle part has even been labeled as the visual word form area. Because the definition of the VWFA largely varies and the reading task differs across studies, the function of the left ventral occipitotemporal cortex in word reading is continuingly debated on whether this region is specific for orthographic processing or be involved in an interactive framework. By using representational similarity analysis (RSA), this study examined information representation in the VWFA at the individual level and the modulatory effect of reading task. Twenty-four subjects were scanned while performing the explicit (i.e., the naming task) and implicit (i.e., the perceptual task) reading tasks. Activation analysis showed that the naming task elicited greater activation in regions related to phonological processing (e.g., the bilateral prefrontal cortex and temporoparietal cortex), while the perceptual task recruited greater activation in visual cortex and default mode network (e.g., the bilateral middle frontal gyrus, angular gyrus, and the right middle temporal gyrus). More importantly, RSA also showed that task modulated information representation in the bilateral anterior occipitotemporal cortex and VWFA. Specifically, ROI-based RSA revealed enhanced orthographic and phonological representations in the bilateral anterior fusiform cortex and VWFA in the naming task relative to the perceptual task. These results suggest that lexical representation in the VWFA is influenced by the demand of phonological processing, which supports the interactive account of the VWFA.
... In addition, the left OTC contains a specific portion in the fusiform gyrus named Visual Word Form Area that has been found to respond specifically to word and word-like stimuli. The left STC, on the other hand, is a central area that represents phonological information (Boets et al., 2013;Glezer et al., 2016), including lexical tone-the supramarginal phoneme in tonal languages such as Chinese Si et al., 2017). The left STC is functionally and structurally connected to the left OTC, which can be shaped by learning grapho-phonological mappings (Thiebaut de Schotten et al., 2014;Stevens et al., 2017). ...
Conquering print-sound mappings (e.g., grapheme-phoneme correspondence rules) is vital for developing fluent reading skills. In neuroimaging research, this ability can be indexed by activation differences between audiovisual congruent against incongruent conditions in brain areas such as the left superior temporal cortex. In line with it, individuals with dyslexia have difficulty in tasks requiring print-sound processing, accompanied by a reduced neural integration. However, existing evidence is almost restricted to alphabetic languages. Whether and how multisensory processing of print and sound is impaired in Chinese dyslexia remains underexplored. In this study, we applied a passive audiovisual integration paradigm with functional magnetic resonance imaging to investigate the possible dysfunctions in processing character-sound (opaque; semantics can be automatically accessed) and pinyin-sound associations (transparent; no particular meaning can be confirmed) in Chinese dyslexic children. Unexpectedly, the dyslexic group did not show reduced neural integration compared with typically developing readers in either character or pinyin experiment. However, the results revealed atypical correlations between neural integration and different reading abilities in dyslexia. Specifically, while the neural integration in the left inferior frontal cortex in processing character-sound pairs correlated with silent reading comprehension in both children with and without dyslexia, it was associated with morphological awareness (semantic-related) in controls but with rapid naming (phonological-related) in dyslexics. This result indicates Chinese dyslexic children may not use the same grapho-semantic processing strategy as their typical peers do. As for pinyin-sound processing, while a stronger neural integration in the direction of "congruent > incongruent" in the left occipito-temporal cortex and bilateral superior temporal cortices was associated with better oral reading fluency in Xia et al. Print-Sound Integration in Chinese Dyslexia the control group, an opposite pattern was found in dyslexia. This finding may reflect dyslexia's dysfunctional recruitment of the regions in grapho-phonological processing, which further impedes character learning.
... The left STG is the central area representing phonological information (Boets et al., 2013;Glezer et al., 2016) and is involved in visual phonological processing in Chinese children and adults (Cao et al., 2010). Its activation and connectivity change after learning visual-sound mappings (Dehaene et al., 2010;Li, Xu, et al., 2020;Thiebaut de Schotten et al., 2014), which can further scaffold later reading development (Wang, Joanisse, et al., 2020). ...
Effortless print-sound integration is essential to reading development, and the superior temporal cortex (STC) is the most critical brain region. However, to date, the conclusion is almost restricted to alphabetic orthographies. To examine the neural basis in non-alphabetic languages and its relationship with reading abilities, we conducted a functional magnetic resonance imaging study in typically developing Chinese children. Two neuroimaging-based indicators of audiovisual processing—additive enhancement (higher activation in the congruent than the average activation of unimodal conditions) and neural integration (different activations between the congruent versus incongruent conditions)—were used to investigate character-sounds (opaque) and pinyin-sounds (transparent) processing. We found additive enhancement in bilateral STCs processing both character and pinyin stimulations. Moreover, the neural integrations in the left STC for the two scripts were strongly correlated. In terms of differentiation, first, areas beyond the STCs showed additive enhancement in processing pinyin-sounds. Second, while the bilateral STCs, left inferior/middle frontal and parietal regions manifested a striking neural integration (incongruent > congruent) for character-sounds, no significant clusters were revealed for pinyin-sounds. Finally, the neural integration in the left middle frontal gyrus for characters was specifically associated with silent reading comprehension proficiency, indicating automatic semantic processing during implicit character-sound integration. In contrast, the neural integration in the left STC for pinyin was specifically associated with oral reading fluency that relies on grapho-phonological mapping. To summarize, this study revealed both script-universal and script-specific neurofunctional substrates of print-sound integration as well as their processing- and region-dependent associations with reading abilities in typical Chinese children.
... Akin to sentence-level comprehension, single words comprehension is also associated with the left supramarginal gyrus (Baldo et al. 2018). Using fMRI in healthy adult readers, the sensitivity of this network was disentangled whereby the parieto-temporal cortex responded to phonology and the VWFA in the occipital-temporal cortex to orthography (Glezer et al. 2016). Current models suggest a delicate temporo-parietal and frontal network to be involved in single word comprehension that links lexical concepts (anterior temporal) lemma and lexicalsyntactic information (posterior temporal), phoneme-to-motor transfer (parietalfrontal), top-down and executive modulation (frontal) (e.g. ...
Stroke significantly impacts quality of life. However, the long-term cognitive evolution in stroke is poorly predictable at the individual level. There is an urgent need for a better prediction of long-term symptoms based on acute clinical neuroimaging data. Previous works have demonstrated a strong relationship between the location of white matter disconnections and clinical symptoms. However, rendering the entire space of possible disconnections-deficit associations optimally surveyable will allow for a systematic association between brain disconnections and cognitive-behavioural measures at the individual level. Here we present the most comprehensive framework, a composite morphospace to predict neuropsychological scores one year after stroke. Linking the latent disconnectome morphospace to neuropsychological outcomes yields biological insights available as the first comprehensive atlas of disconnectome-deficit relations across 86 neuropsychological scores. Out-of-sample prediction derived from this atlas achieved average accuracy over 80%, which is higher than any other framework. Our novel predictive framework is available as an interactive web application, the disconnectome symptoms discoverer (http://disconnectomestudio.bcblab.com), to provide the foundations for a new and practical approach to modelling cognition in stroke. Our atlas and web application will reduce the burden of cognitive deficits on patients, their families, and wider society while also helping to tailor personalized treatment programs and discover new targets for treatments. We expect the range of assessments and the predictive power of our framework to increase even further through future crowdsourcing.
... The traditional reading network is supported by functional magnetic resonance imaging (fMRI) (e.g. Glezer et al. 2016) and diffusion magnetic resonance imaging (dMRI) studies (e.g. Vandermosten et al. 2012) revealing that in adult readers dorsal temporal parietal regions are sensitive to phonology and ventral occipital temporal regions to orthography. ...
The visual word form area (VWFA) plays a significant role in the development of reading skills. However, the developmental course and anatomical properties of the VWFA have only limitedly been investigated. The aim of the current longitudinal MRI study was to investigate dynamic, bidirectional relations between reading, and the structure of the left fusiform gyrus at the early-to-advanced reading stage. More specifically, by means of bivariate correlations and a cross-lagged panel model (CLPM), the interrelations between the size of the left fusiform gyrus and reading skills (an average score of a word and pseudo-word reading task) were studied in a longitudinal cohort of 43 Flemish children (29M, 14F) with variable reading skills in grade 2 (the early stage of reading) and grade 5 (the advanced stage of reading) of primary school. Results revealed that better reading skills at grade 2 lead to a larger size of the left fusiform gyrus at grade 5, whereas there are no directional effects between the size of the left fusiform gyrus at grade 2 and reading skills at grade 5. Hence, according to our results, there is behavior-driven brain plasticity and no brain-driven reading change between the early and advanced stage of reading. Together with pre-reading brain studies showing predictive relations to later reading scores, our results suggest that the direction of brain–behavioral influences changes throughout the course of reading development.
... (Hsiao et al., 2007;Lee et al., 2007), 也与 fMRI 研究 中发现的汉字阅读中双侧梭状回的参与激活一致(Booth et al., 2006;Liu et al., 2008;Krafnick et al., 2016;Mo et al., 2015)。例如, 在 Wang 等人(2011)而汉字具有形旁表义的独特性, 从而研究者可以直 接 操 纵 汉 字 形 旁 来 探 讨 了 词 汇 阅 读 的 神 经 机 制Yang et al., 2011Yang et al., , 2012 Wang et al., 词汇加工(Glezer et al., 2009)以及语音研究(Glezer et al., 2016)中得到了应用, 能很好的研究刺激特性 ...
... The VWFA receives signals from early visual cortex; is sensitive to image properties that are ubiquitous across visual cortex, such as image contrast (Kay & Yeatman 2017); and is modulated by selective spatial attention to particular locations in the visual field (White et al. 2019c). However, the VWFA is also sensitive to linguistic properties of written words, such as the sounds represented by the letters (Glezer et al. 2016(Glezer et al. , 2019McCandliss et al. 2003). Moreover, top-down signals activate the VWFA during many speech perception tasks , Pugh et al. 2013. ...
The scientific study of reading has a rich history that spans disciplines from vision science to linguistics, psychology, cognitive neuroscience, neurology, and education. The study of reading can elucidate important general mechanisms in spatial vision, attentional control, object recognition, and perceptual learning, as well as the principles of plasticity and cortical topography. However, literacy also prompts the development of specific neural circuits to process a unique and artificial stimulus. In this review, we describe the sequence of operations that transforms visual features into language, how the key neural circuits are sculpted by experience during development, and what goes awry in children for whom learning to read is a struggle.
Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
... The dorsal stream's role in reading encompasses controlling both the direction of eye movements and visual attention, and also the translation from graphemes (visual letters) to phonemes (letter sounds), a process known as grapheme to phoneme conversion, which is specifically associated with activity in the supramarginal gyrus (Glezer et al., 2016;Oberhuber et al., 2016;Aguilar et al., 2018). The ventral and dorsal streams thereby offer two alternative routes to word readingthe ventral route is involved in recognition of known word forms and the dorsal route is involved in "assembled phonology," i.e., decoding a word based on its constituent letters. ...
Alexia refers to a reading disorder caused by some form of acquired brain pathology, most commonly a stroke or tumor, in a previously literate subject. In neuropsychology, a distinction is made between central alexia (commonly seen in aphasia) and peripheral alexia (a perceptual or attentional deficit). The prototypical peripheral alexia is alexia without agraphia (pure alexia), where patients can write but are impaired in reading words and letters. Pure alexia is associated with damage to the left ventral occipitotemporal cortex (vOT) or its connections. Hemianopic alexia is associated with less extensive occipital damage and is caused by a visual field defect, which creates problems reading longer words and passages of text. Reading impairment can also arise due to attentional deficits, most commonly following right hemisphere or bilateral lesions. Studying patients with alexia, along with functional imaging studies of normal readers, has improved our understanding of the neurobiological processes involved in reading. A key question is whether an area in the left ventral occipitotemporal cortex is specialized for or selectively involved in word processing, or whether reading relies on tuning of more general purpose perceptual areas. Reading deficits may also be observed in dementia and traumatic brain injury, but often with less consistent deficit patterns than in patients with focal lesions.
... In addition, Glezer et al. (2016) recently found that for typical hearing readers, a region within the temporal-parietal cortex is finely tuned to phonological representations when reading single words. However, this region showed only weak selectivity to phonology in skilled deaf readers (Glezer et al., 2018). ...
Deaf individuals have unique sensory and linguistic experiences that influence how they read and become skilled readers. This review presents our current understanding of the neurocognitive underpinnings of reading skill in deaf adults. Key behavioural and neuroimaging studies are integrated to build a profile of skilled adult deaf readers and to examine how changes in visual attention and reduced access to auditory input and phonology shape how they read both words and sentences. Crucially, the behaviours, processes, and neural circuity of deaf readers are compared to those of hearing readers with similar reading ability to help identify alternative pathways to reading success. Overall, sensitivity to orthographic and semantic information is comparable for skilled deaf and hearing readers, but deaf readers rely less on phonology and show greater engagement of the right hemisphere in visual word processing. During sentence reading, deaf readers process visual word forms more efficiently and may have a greater reliance on and altered connectivity to semantic information compared to their hearing peers. These findings highlight the plasticity of the reading system and point to alternative pathways to reading success.
... The traditional reading network is supported by fMRI (e.g. Glezer et al., 2016) and dMRI studies (e.g. Vandermosten et al., 2012) revealing that in adult readers dorsal temporal parietal regions are sensitive to phonology and ventral occipital temporal regions to orthography. ...
The visual word form area (VWFA) plays a significant role in the development of reading skills. However, the developmental course and anatomical properties of the VWFA have only limitedly been investigated. The aim of the current longitudinal MRI study was to investigate dynamic, bidirectional relations between reading and the structure of the left fusiform gyrus at the early-to-advanced reading stage. More specifically, by means of bivariate correlations and a cross-lagged panel model (CLPM), the interrelations between the size of the left fusiform gyrus and reading skills (a composite score of a word and pseudo-word reading task) were studied in a longitudinal cohort of 43 Flemish children (29M, 14F) with variable reading skills in grade 2 (the early stage of reading) and grade 5 (the advanced stage of reading) of primary school. Results revealed that better reading skills at grade 2 lead to a larger size of the left fusiform gyrus at grade 5, whereas there are no directional effects between the size of the left fusiform gyrus at grade 2 and reading skills at grade 5. Hence, according to our results there is behavior-driven brain plasticity and no brain-driven reading change between the early and advanced stage of reading. Together with pre-reading brain studies showing predictive relations to later reading scores, our results suggest that the direction of brain-behavioral influences changes throughout the course of reading development.
... The most consistent finding across neuroimaging studies in the literature of RD is reduced activation in the OT areas (Hu et al., 2010;Paulesu et al., 2001;Richlan et al., 2011). The left ventral occipitotemporal cortex is considered to be a key region for orthographic processing, as the "visual word form area" (VWFA) is located in this region (Glezer et al., 2016). The left OT cortex starts to show specialization for orthographic processing as reading acquisition increases (Brem et al., 2010;Pleisch et al., 2019a,b). ...
Deficits have been documented in visuo-orthographic processing as well as phonological retrieval/manipulation during visual word reading in individuals with reading disability (RD); however, the relationship between these deficits remains unclear. Previously, we found that during word reading, visuo-orthographic deficit appears to be a neural signature of RD, but deficits in phonological retrieval/manipulation appears to be a consequence of being RD (Cao, et al., 2020). Therefore, in the current study, we directly tested the hypothesis that during visual word reading, deficit in phonological retrieval/manipulation may result from weakened input from visuo-orthographic regions, and that this relationship tends to be universal across languages. We conducted a dynamic causal modelling analysis of fMRI data from Chinese-English bilingual children (9-11 years, N=78) with or without RD during a visual word rhyming judgment task. We found a weaker connection from the left inferior temporal gyrus (ITG) to the left dorsal inferior frontal gyrus (dIFG) in children with RD and reading controls than the connection found in age controls for both Chinese and English. This finding suggests that the phonological deficit at the dIFG may result from weak input from the visuo-orthographic region and this connection appears to be responsive to reading level rather than RD, because the reading-control children were similar to children with RD. We also found that the left ITG was selectively connected with language-specific regions (i.e., the left inferior parietal lobe (IPL) for Chinese and the left ventral inferior frontal gyrus (vIFG) for English) depending on the language being processed; however, this language selectivity was reduced in children with RD, suggesting that decreased language specialization is associated with RD. Using a double control design, our study suggests that during reading, the visuo-orthographic deficit of RD constrains the development of the connection from orthography to phonology and to other language-specific processing due to distorted quantity and quality of reading.
... Dorsal areas such as the posterior parietal cortex are responsible for the direction of visuospatial attention and eye movements, and damage to temporoparietal cortex can cause attentional reading impairments (e.g., neglect alexia; Ptak et al., 2012;Boukrina et al., 2020). In addition, the dorsal stream (particularly the supramarginal gyrus) is associated with the translation of graphemes to phonemes (Aguilar et al., 2018;Glezer et al., 2016;Oberhuber et al., 2016). In this way, the anatomical dissociation between dorsal and ventral visual streams may correspond to the neuropsychological dual routes for reading: the dorsal route underlying the "sublexical" or decoding style of reading, and the ventral route underlying "lexical" reading. ...
Alexia refers to an impairment in reading caused by injury to the brain in patients who could read normally before their brain injury. Alexia is most commonly observed following stroke, but may arise as a consequence of other brain disorders too. The reading impairment will have a different presentation depending on which parts of the brain are affected. Central alexias are reading impairments that are related to more widespread language problems, while peripheral alexia refers to reading impairment caused by perceptual or attentional deficits. The study of acquired reading disorders has been central in the development of cognitive models of the reading system. We present the main cognitive models of reading, and the central cognitive and clinical aspects of the main forms of alexia.
... Their prior experience with print supports increased brain activation (Sela, Izzetoglu, Izzetoglu, & Onaral, 2014). Thus, readers draw on prior print experiences for orthographic processing, involving the visual representation of words or groups of letters (Dehaene & Cohen, 2011;Fischer-Baum, Bruggemann, Gallego, Li, & Tamez, 2017) to support rapid identification of familiar words without phonological processing (Glezer et al., 2016), facilitating fluent reading and comprehension. ...
In this position article, the authors explore a confluence of evidence that supports the understanding that multiple factors, various processes, and multiple sources of information inform reading. The authors open by briefly describing concerns related to how some scholars and media reporters have characterized the simple view of reading and narrowly applied that model to teaching young readers. The authors then explore a confluence of complexity across (a) theoretical models of reading based on empirical research, (b) emerging information related to the brain and reading, and (c) research findings based on close observations of young learners. Finally, the authors argue that reductive and singular models of reading fail to not only honor the individuality of young readers but also to recognize the systemic changes needed in schools and communities to equitably serve all students.
... This supports the idea that complete left lateralisation of written language is rarely observed. Most neuroimaging findings show that different regions in both cerebral hemispheres related to the visual and auditory systems are necessary for skilled reading (Glezer et al. 2016). In particular, the bilingual group in our study exhibited greater right hemisphere activity than monolinguals, which has been found to be consistent across bilingual tasks and language pairs (Hull and Vaid 2007;Hervais-Adelman et al. 2015;Fu et al. 2017;Ghazi-Saidi and Ansaldo 2017;Yang et al. 2018;Cargnelutti et al. 2019). ...
Approximately half the world’s population can speak more than one language. In this selective review, we consider whether there is an advantage to bilingualism and whether the bilingual brain is different in terms of both executive functioning and lexical decision-making. We focus on two functional MRI studies from our lab where task performance and brain activation from late proficient bilinguals when using their first (L1) and second (L2) language are compared to matched monolinguals. In Study One, monolinguals produced greater activation than bilinguals during Stroop performance, regardless of task demands. During interference, monolinguals showed more posterior brain activation relative to bilinguals and during response conflict, monolinguals showed greater activation in the anterior cingulate and prefrontal regions. In Study Two, bilinguals recruited more extensive networks when processing L2 than L1 and when compared to monolinguals. Bilinguals also showed weaker lateralisation, particularly in the temporal lobe, during both L1 and L2 lexical decisions. Taken together, learning a second language late confers a benefit to executive functioning but at the expense of decreased cortical efficiency. Research is now required to determine the extent of plasticity in both language- and non-language dedicated areas, and how this plasticity is modulated by experience throughout the lifespan.
... Indeed, recent fMRI studies (Bouhali, Bézagu, Dehaene, &, 2019;Lerma-Usabiaga, Carreiras, & Paz-Alonso, 2018;White, Palmer, Boynton, & Yeatman, 2019) have shown that the VWFA comprises two functionally distinct orthographic areas: one mesial and posterior that is sensitive to grapheme complexity, word length, and to phonological demands (sublexical processing), and another more lateral and anterior region that is sensitive to lexicality and word frequency (lexical processing). Indeed, the anterior portion of the VWFA contains neurons tightly tuned to whole-word orthographic representations (e.g., Thesen et al., 2012;Vinckier et al., 2007), which differentiate whole words (Strother, Zhou, Coros, & Vilis, 2017), regardless of whether they are fully different (e.g., boat vs. fish) or differ by just one letter (e.g., pole vs. poke; Glezer, Jian, & Riesenhuber, 2009) even if they are homophones (e.g., poll vs. pole; Glezer, Eden, Jiang, Luetje, Napoliello, Kim, & Riesenhuber, 2016). This evidence suggests that this region is the neural underpinning of holistic, lexical (whole-word) orthographic representations (Bouhali et al. 2019;Lerma-Usabiaga et al., 2018;White et al., 2019). ...
Holistic processing of visual words (i.e., obligatory encoding of/attending to all letters of a word) could be a marker of expert word recognition. In the present study, we thus examined for the first time whether there is a direct relation between the word-composite effect (i.e., all parts of a visual word are fully processed when observers perform a task on a word part) and fast access to the orthographic lexicon by visual word experts (i.e., fluent adult readers). We adopted an individual differences approach and used the word-frequency effect (i.e., faster recognition of high- than low-frequency words) in an independent lexical decision task as a proxy of fast access to lexical orthographic representations. Fluent readers with larger word-composite effect showed smaller word-frequency effect. This correlation was mainly driven by an association between a larger composite effect and faster lexical decision on low-frequency words, probably because these lexical representations are less stable and integrated/unitized, hence allowing differentiating among fluent readers. We thus showed that holistic processing of visual words is indeed related to higher efficiency in visual word recognition by skilled readers.
... Schurz et al., 2010). Similarly, the IFG was not only activated by lexico-semantic categorization (Glezer et al., 2016;Montant et al., 2011) and this was true when differences in withinscanner performance were taken into account to partial out potential differences in task demands. Thus, the present data support the idea of an interactive network account of visual word processing. ...
The reading system can be broken down into four basic subcomponents in charge of prelexical, orthographic,
phonological, and lexico-semantic processes. These processes need to jointly work together to become a fluent and efficient reader. Using functional magnetic resonance imaging (fMRI), we systematically analyzed differ- ences in neural activation patterns of these four basic subcomponents in children (N = 41, 9–13 years) using tasks specifically tapping each component (letter identification, orthographic decision, phonological decision, and semantic categorization). Regions of interest (ROI) were selected based on a meta-analysis of child reading and included the left ventral occipito-temporal cortex (vOT), left posterior parietal cortex (PPC), left inferior frontal gyrus (IFG), and bilateral supplementary motor area (SMA). Compared to a visual baseline task, en- hanced activation in vOT and IFG was observed for all tasks with very little differences between tasks. Activity in the dorsal PPC system was confined to prelexical and phonological processing. Activity in the SMA was found in orthographic, phonological, and lexico-semantic tasks. Our results are consistent with the idea of an early en- gagement of the vOT accompanied by executive control functions in the frontal system, including the bilateral SMA.
... Crosshair locations depict a) overlapping activation in the rTPJ for EWs in both the reflexive and voluntary tasks, b) unique activation in the rIFG for the conjunction between EWs and reflexive attention, and c) unique activation in the IPS for the conjunction between EWs and voluntary attention. involvement in lexical and sublexical reading, as recent research has suggested that the VWFA is exclusively sensitive to orthographic stimuli (i.e., real words) and that VWFA activation for pseudowords is due to their ability to evoke representations of orthographically similar real words (see Glezer et al., 2009;Glezer et al., 2015,Glezer et al., 2016 for an examination of the VWFA sensitivity using fMRI rapid adaptation; see also Hirshorn et al., 2016 for work with direct neural recordings and electrical brain stimulation). ...
Recent research has shown a relationship between reading and attention, however the neuroanatomical overlap of these two processes has remained relatively unexplored. Therefore, we sought to investigate the overlapping neural mechanisms of spatial attention and reading using functional magnetic resonance imaging. Participants performed two attentional orienting tasks (reflexive and voluntary), and two overt word-reading tasks (lexical and sublexical). We hypothesized that there would be greater unique activation overlap of reflexive attention with lexical reading, and of voluntary attention with sublexical reading. Results indicated that lexical reading had greater overlapping activation in reflexive orienting areas compared to sublexical reading, suggesting that lexical reading may employ more automatic attentional mechanisms. In contrast, sublexical reading had greater overlapping activation with voluntary attention areas compared to lexical reading, suggesting that phonetic decoding may rely more heavily on voluntary attention. This research broadens our understanding of the neural overlap that underlies the relationship between reading and spatial attention.
... English was used as the language for rapid number naming. The visual-verbal task requirements of the KD test involve the conversion of graphemic, or symbolic, depictions of numbers to their phonologic, or vocalized, representations (12,13). Further complexity may arise for non-native language speakers if the subject's native language does not use Arabic numerals or if speakers have unique non-reading eye behaviour approaches for task completion. ...
Objective: To determine if native English speakers (NES) perform differently compared to non-native English speakers (NNES) on a sideline-focused rapid number naming task. A secondary aim was to characterize objective differences in eye movement behaviour between cohorts.
Background: The King-Devick (KD) test is a rapid number-naming task in which numbers are read from left-to-right. This performance measure adds vision-based assessment to sideline concussion testing. Reading strategies differ by language. Concussion may also impact language and attention. Both factors may affect test performance.
Methods: Twenty-seven healthy NNES and healthy NES performed a computerized KD test under high-resolution video-oculography. NNES also performed a Bilingual Dominance Scale (BDS) questionnaire to weight linguistic preferences (i.e., reliance on non-English language(s)).
Results: Inter-saccadic intervals were significantly longer in NNES (346.3 ± 78.3 ms vs. 286.1 ± 49.7 ms, p = 0.001), as were KD test times (54.4 ± 15.1 s vs. 43.8 ± 8.6 s, p = 0.002). Higher BDS scores, reflecting higher native language dominance, were associated with longer inter-saccadic intervals in NNES.
Conclusion: These findings have direct implications for the assessment of athlete performance on vision-based and other verbal sideline concussion tests; these results are particularly important given the international scope of sport. Pre-season baseline scores are essential to evaluation in the event of concussion, and performance of sideline tests in the athlete’s native language should be considered to optimize both baseline and post-injury test accuracy.
... Although it is unclear how exactly phonological processes might relate to the pitch-elevation crossmodal correspondence, phonology does involve crossmodal re-coding of visual into auditory representations (Goswami 1993(Goswami , 2008; thus, it is possible that similar neural processes might underlie the audiovisual correspondence between pitch and elevation. Arguing against a relationship between phonology and crossmodal correspondence in the case of the right parietal site is that activations related to phonological processing are predominantly left hemispheric (Glezer et al., 2016;Zhang et al., 2017). Thus, given that the potential relationship to phonology was not predicted, and further since the right parietal cluster active on the congruency contrast was also sensitive to the interaction effect between the congruency type of a particular trial and its immediate predecessor, this relationship requires further experimental evaluation. ...
Crossmodal correspondences refer to associations between otherwise unrelated stimulus features in different sensory modalities. For example, high and low auditory pitches are associated with high and low visuospatial elevation, respectively. The neural mechanisms underlying crossmodal correspondences are currently unknown. Here, we used functional magnetic resonance imaging (fMRI) to investigate the neural basis of the pitch-elevation correspondence. Pitch-elevation congruency effects were observed bilaterally in the inferior frontal and insular cortex, the right frontal eye field and right inferior parietal cortex. Independent functional localizers failed to provide strong evidence for any of three proposed mechanisms for crossmodal correspondences: semantic mediation, magnitude estimation, and multisensory integration. Instead, pitch-elevation congruency effects overlapped with areas selective for visually presented non-word strings relative to sentences, and with regions sensitive to audiovisual asynchrony. Taken together with the prior literature, the observed congruency effects are most consistent with mediation by multisensory attention.
... Recent research led by cognitive scientist Maximillian Riesenhuber at Georgetown University has revealed just how quickly we turn commonly used words back into images or pictures making the reading process faster and more fluid. We 'see' commonly-used words rather than 'read' them (Riesenhuber, 2016). Our alphabets are the result of a four-thousand-year evolution as we moved from image to text (Fang, 2015). ...
This paper explores the potential of Generative Sketchnoting as a visual framework for faster problem framing and leaner high-level concept development.
... At the same time, neither are frontostriatal networks exclusively devoted to these language functions. Indeed, several of their constituting hubs have been implicated in fluency (Ardila et al., 2016), phonology (Tettamanti et al., 2005), and orthographic processing (Glezer et al., 2016). In sum, while these circuits and the three subdomains reviewed are critically linked, they do not stand in a one-to-one relationship. ...
Within the language domain, movement disorders triggered by frontostriatal damage are characterized by deficits in action verbs, motor-language coupling, and syntax. However, these impairments have not been jointly interpreted under a unifying rationale or integratively assessed in terms of possible clinical implications. To bridge these gaps, here we introduce the “disrupted motor grounding hypothesis”, a new framework to conceive such impairments as disturbances of embodied mechanisms (high-order domains based on the recycling of functionally germane sensorimotor circuits). We focus on two relevant lesion models: Parkinson's and Huntington's disease. First, we describe the physiopathology of both conditions as models of progressive frontostriatal impairment. Then, we summarize works assessing action language, motor-language coupling, and syntax in samples at early and preclinical disease stages. To conclude, we discuss the implications of the evidence for neurolinguistic modeling, identify key issues to be addressed in future research, and discuss potential clinical implications. In brief, our work seeks to open new theoretical and translational avenues for embodied cognition research.
... Schurz et al., 2010). Similarly, the IFG was not only activated by lexico-semantic categorization (Glezer et al., 2016;Montant et al., 2011) and this was true when differences in withinscanner performance were taken into account to partial out potential differences in task demands. Thus, the present data support the idea of an interactive network account of visual word processing. ...
The reading system can be broken down into four basic subcomponents in charge of prelexical, orthographic, phonological, and lexico-semantic processes. These processes need to jointly work together to become a fluent and efficient reader. Using functional magnetic resonance imaging (fMRI), we systematically analyzed differences in neural activation patterns of these four basic subcomponents in children (N=41, 9–13 years) using tasks specifically tapping each component (letter identification, orthographic decision, phonological decision, and semantic categorization). Regions of interest (ROI) were selected based on a meta-analysis of child reading and included the left ventral occipito-temporal cortex (vOT), left posterior parietal cortex (PPC), left inferior frontal gyrus (IFG), and bilateral supplementary motor area (SMA). Compared to a visual baseline task, enhanced activation in vOT and the IFG was observed for all tasks with very little differences between tasks. Activity in the dorsal PPC system was confined to prelexical and phonological processing. Activity in the SMA was found in orthographic, phonological, and lexico-semantic tasks. Our results are consistent with the idea of an early engagement of the vOT accompanied by executive control functions in the frontal system, including the bilateral SMA.
... Arguably, the phonology-related activations in the VWFA in the above studies could be attributed to top-down modulation of orthographic processing by phonology, but may not necessarily result from phonological processing per se (Dehaene and Cohen, 2011). Although studies using rapid adaptation (Glezer et al. 2009(Glezer et al. , 2015(Glezer et al. , 2016 or MVPA Nestor et al. 2013;Rothlein and Rapp, 2014;Baeck et al. 2015) hold the promise of pinpointing the neural representation in the fusiform region, these studies did not separately manipulate orthographic similarity and phonological similarity. Chinese language is a particularly good orthography for this purpose because it has complex visual structure and irregular grapheme-to-phoneme correspondence, which allow for the selection of stimuli whose phonological and orthographic similarities are essentially uncorrelated. ...
Mental and neural representations of words are at the core of understanding the cognitive and neural mechanisms of reading. Despite extensive studies, the nature of visual word representation remains highly controversial due to methodological limitations. In particular, it is unclear whether the fusiform cortex contains only abstract orthographic representation, or represents both lower and higher level orthography as well as phonology. Using representational similarity analysis, we integrated behavioral ratings, computational models of reading and visual object recognition, and neuroimaging data to examine the nature of visual word representations in the fusiform cortex. Our results provided clear evidence that the middle and anterior fusiform represented both phonological and orthographic information. Whereas lower level orthographic information was represented at every stage of the ventral visual stream, abstract orthographic information was increasingly represented along the posterior-to-anterior axis. Furthermore, the left and right hemispheres were tuned to high- and low-frequency orthographic information, respectively. These results help to resolve the long-standing debates regarding the role of the fusiform in reading, and have significant implications for the development of psychological, neural, and computational theories of reading.
The existence of a neural representation for whole words (i.e., a lexicon) is a common feature of many models of speech processing. Prior studies have provided evidence for a visual lexicon containing representations of whole written words in an area of the ventral visual stream known as the “Visual Word Form Area” (VWFA). Similar experimental support for an auditory lexicon containing representations of spoken words has yet to be shown. Using fMRI rapid adaptation techniques, we provide evidence for an auditory lexicon in the “Auditory Word Form Area” (AWFA) in the human left anterior superior temporal gyrus that contains representations highly selective for individual spoken words. Furthermore, we show that familiarization with novel auditory words sharpens the selectivity of their representations in the AWFA. These findings reveal strong parallels in how the brain represents written and spoken words, showing convergent processing strategies across modalities in the visual and auditory ventral streams.
Learning to read impacts the way the ventral occipitotemporal cortex (VOT) reorganizes. The postulated underlying mechanism of neuronal recycling was recently revisited. Neuroimaging data showed that voxels weakly specialized for visual processing keep their initial category selectivity (i.e., object or face processing) while acquiring an additional and stronger responsivity to written words. Here, we examined a large and diverse group of six-year-olds prior to formal literacy training (N = 72) using various data analysis techniques (univariate, multivariate, rapid adaptation) and types of stimuli (print, false fonts, houses, faces) to further explore how VOT changes and adapts to the novel skill of reading. We found that among several visual stimuli categories only print activated a wide network of language related areas outside of the bilateral visual cortex, and the level of reading skill was related to the strength of this activation, showing the development of the reading circuit. Rapid adaptation was not directly related to the level of reading skill in the young children studied here, but it clearly revealed the emergence of the reading network in readers. Most importantly, we found that the reorganization of the VOT is not in fact an "invasion" by reading acquisition-voxels previously activated for faces started to respond more for print, while at the same time keeping their previous function. We can thus conclude that the revised hypothesis of neuronal recycling is supported by our data.
Introduction
According to the strong version of the orthographic depth hypothesis, in languages with transparent letter-sound mappings (shallow orthographies) the reading of both familiar words and unfamiliar nonwords may be accomplished by a sublexical pathway that relies on serial grapheme-to-phoneme conversion. However, in languages such as English characterized by inconsistent letter-sound relationships (deep orthographies), word reading is mediated by a lexical-semantic pathway that relies on mappings between word-specific orthographic, semantic, and phonological representations, whereas the sublexical pathway is used primarily to read nonwords.
Methods
In this study, we used functional magnetic resonance imaging to elucidate neural substrates of reading in Czech, a language characterized by a shallo worthography. Specifically, we contrasted patterns of brain activation and connectivity during word and nonword reading to determine whether similar or different neural mechanisms are involved. Neural correlates were measured as differences in simple whole-brain voxel-wise activation, and differences in visual word form area (VWFA) task-related connectivity were computed on the group level from data of 24 young subject. Trial-to-trial reading reaction times were used as a measure of task difficulty, and these effects were subtracted from the activation and connectivity effects in order to eliminate difference in cognitive effort which is naturally higher for nonwords and may mask the true lexicality effects.
Results
We observed pattern of activity well described in the literature mostly derived from data of English speakers – nonword reading (as compared to word reading) activated the sublexical pathway to a greater extent whereas word reading was associated with greater activation of semantic networks. VWFA connectivity analysis also revealed stronger connectivity to a component of the sublexical pathway - left inferior frontal gyrus (IFG), for nonword compared to word reading.
Discussion
These converging results suggest that the brain mechanism of skilled reading in shallow orthography languages are similar to those engaged when reading in languages with a deep orthography and are supported by a universal dual-pathway neural architecture.
The existence of a neural representation for whole words (i.e., a lexicon) is a common feature of many models of speech processing. Prior studies have provided evidence for a visual lexicon containing representations of whole written words in an area of the ventral visual stream known as the “Visual Word Form Area” (VWFA). Similar experimental support for an auditory lexicon containing representations of spoken words has yet to be shown. Using fMRI rapid adaptation techniques, we provide evidence for an auditory lexicon in the “Auditory Word Form Area” (AWFA) in the human left anterior superior temporal gyrus that contains representations highly selective for individual spoken words. Furthermore, we show that familiarization with novel auditory words sharpens the selectivity of their representations in the AWFA. These findings reveal strong parallels in how the brain represents written and spoken words, showing convergent processing strategies across modalities in the visual and auditory ventral streams.
Highlights
Individual auditory word form areas (AWFA) were defined via an auditory localizer
The AWFA shows tuning for individual real words but not untrained pseudowords
The AWFA develops tuning for individual pseudowords after training
Literacy represents an incredible accomplishment of modern human societies. Literacy exemplifies the human brain's impressive capacity for experience‐dependent plasticity. Literacy is grounded in circuits that evolved for component processes such as spoken language and visual recognition. This chapter provides an overview of the literate brain's reading circuitry, a description of how these circuits are sculpted by education, and discussion of the major differences in children with dyslexia. Before embarking on this, it is important to consider the methods used to investigate brain structure and function. The first major insights into the neurobiology of literacy were made based on post mortem brain dissections. The understanding of the neurobiological underpinnings of developmental dyslexia still evolving.
Brain abnormalities in the reading network have been repeatedly reported in individuals with developmental dyslexia (DD); however, it is still not totally understood where the structural and functional abnormalities are consistent/inconsistent across languages. In the current multimodal meta-analysis, we found convergent structural and functional alterations in the left superior temporal gyrus across languages, suggesting a neural signature of DD. We found greater reduction in grey matter volume and brain activation in the left inferior frontal gyrus in morpho-syllabic languages (e.g. Chinese) than in alphabetic languages, and greater reduction in brain activation in the left middle temporal gyrus and fusiform gyrus in alphabetic languages than in morpho-syllabic languages. These language differences are explained as consequences of being DD while learning a specific language. In addition, we also found brain regions that showed increased grey matter volume and brain activation, presumably suggesting compensations and brain regions that showed inconsistent alterations in brain structure and function. Our study provides important insights about the etiology of DD from a cross-linguistic perspective with considerations of consistency/inconsistency between structural and functional alterations.
Typical readers rely on two brain pathways for word processing in the left hemisphere: temporo-parietal cortex (TPC) and inferior frontal cortex (IFC), thought to subserve phonological decoding, and occipito-temporal cortex (OTC), including the “visual word form area” (VWFA), thought to subserve orthographic processing. How these regions are affected in developmental dyslexia has been a topic of intense research. We employed fMRI rapid adaptation (fMRI-RA) in adults with low reading skills to examine in independently-defined functional regions of interest (ROIs) phonological selectivity to written words in left TPC and IFC, and to orthographic selectivity to written words in OTC. Consistent with the phonological deficit hypothesis of dyslexia, we found responsivity but not selectivity to phonology, as accessed by written words, in the posterior superior temporal gyrus (pSTG) of the TPC. On the other hand, we found orthographic selectivity in the VWFA of the OTC. We also found selectivity to orthographic and not phonological processing in the IFG, a finding previously reported for typical readers. Together our results demonstrate that in adults with poor reading skills, selectivity to phonology is compromised in pSTG, while selectivity to orthography in the VWFA remains unaffected at this level of processing.
Our recent work has shown that the visual word form area (VWFA) in the left occipitotemporal cortex contains an orthographic lexicon based on neuronal representations highly selective for individual written real words (RWs) and that learning novel words selectively increases neural specificity in the VWFA. But, how quickly does this change in neural tuning occur and how much training is required for new words to be codified in the VWFA? Here, we present evidence that plasticity in the VWFA from broad to tight tuning can be obtained in a short time span, with no explicit training, and with comparatively few exposures, further strengthening the case for a highly plastic visual lexicon in the VWFA and for localist representations in the visual processing hierarchy.
Previous studies of patients with phonological and surface alexia have demonstrated a double dissociation between the reading of pseudo words and words with atypical spelling-to-sound relationships. A corresponding double dissociation in the neuronal activation patterns for pseudo words and exception words has not, however, been consistently demonstrated in normal subjects. Motivated by the literature on acquired alexia, the present study contrasted pseudo words to exception words and explored how neuronal interactions within the reading system are influenced by word type. Functional magnetic resonance imaging was used to measure neuronal responses during reading in 22 healthy volunteers. The direct comparison of reading pseudo words and exception words revealed a double dissociation within the left frontal cortex. Pseudo words preferentially increased left dorsal premotor activation, whereas exception words preferentially increased left pars triangularis activation. Critically, these areas correspond to those previously associated with phonological and semantic processing, respectively. Word-type dependent interactions between brain areas were then investigated using dynamic causal modeling. This revealed that increased activation in the dorsal premotor cortex for pseudo words was associated with a selective increase in effective connectivity from the posterior fusiform gyrus. In contrast, increased activation in the pars triangularis for exception words was associated with a selective increase in effective connectivity from the anterior fusiform gyrus. The present investigation is the first to identify distinct neuronal mechanisms for semantic and phonological contributions to reading. &
The nature of orthographic representations in the human brain is still subject of much debate. Recent reports have claimed that the visual word form area (VWFA) in left occipitotemporal cortex contains an orthographic lexicon based on neuronal representations highly selective for individual written real words (RWs). This theory predicts that learning novel words should selectively increase neural specificity for these words in the VWFA. We trained subjects to recognize novel pseudowords (PWs) and used fMRI rapid adaptation to compare neural selectivity with RWs, untrained PWs (UTPWs), and trained PWs (TPWs). Before training, PWs elicited broadly tuned responses, whereas responses to RWs indicated tight tuning. After training, TPW responses resembled those of RWs, whereas UTPWs continued to show broad tuning. This change in selectivity was specific to the VWFA. Therefore, word learning appears to selectively increase neuronal specificity for the new words in the VWFA, thereby adding these words to the brain's visual dictionary.
Copyright © 2015 the authors 0270-6474/15/354965-08$15.00/0.
fMRI studies using a region-of-interest approach have revealed that the ventral portion of the left occipito-temporal cortex, which is specialized for orthographic processing of visually presented words (and includes the so-called “visual word form area”, VWFA), is characterized by a posterior-to-anterior gradient of increasing selectivity for words in typically reading adults, adolescents, and children (e.g. Brem et al. 2006 and Brem et al. 2009). Similarly, the left inferior frontal cortex (IFC) has been shown to exhibit a medial-to-lateral gradient of print selectivity in typically reading adults (Vinckier et al., 2007). Functional brain imaging studies of dyslexia have reported relative underactivity in left hemisphere occipito-temporal and inferior frontal regions using whole-brain analyses during word processing tasks. Hence, the question arises whether gradient sensitivities in these regions are altered in dyslexia. Indeed, a region-of-interest analysis revealed the gradient-specific functional specialization in the occipito-temporal cortex to be disrupted in dyslexic children (van der Mark et al., 2009). Building on these studies, we here (1) investigate if a word-selective gradient exists in the inferior frontal cortex in addition to the occipito-temporal cortex in normally reading children, (2) compare typically reading with dyslexic children, and (3) examine functional connections between these regions in both groups. We replicated the previously reported anterior-to-posterior gradient of increasing selectivity for words in the left occipito-temporal cortex in typically reading children, and its absence in the dyslexic children. Our novel finding is the detection of a pattern of increasing selectivity for words along the medial-to-lateral axis of the left inferior frontal cortex in typically reading children and evidence of functional connectivity between the most lateral aspect of this area and the anterior aspects of the occipito-temporal cortex. We report absence of an IFC gradient and connectivity between the lateral aspect of the IFC and the anterior occipito-temporal cortex in the dyslexic children. Together, our results provide insights into the source of the anomalies reported in previous studies of dyslexia and add to the growing evidence of an orthographic role of IFC in reading.
We used quantitative, coordinate-based meta-analysis to objectively synthesize age-related commonalities and differences in brain activation patterns reported in 40 functional magnetic resonance imaging (fMRI) studies of reading in children and adults. Twenty fMRI studies with adults (age means: 23–34 years) were matched to 20 studies with children (age means: 7–12 years). The separate meta-analyses of these two sets showed a pattern of reading-related brain activation common to children and adults in left ventral occipito-temporal (OT), inferior frontal, and posterior parietal regions. The direct statistical comparison between the two meta-analytic maps of children and adults revealed higher convergence in studies with children in left superior temporal and bilateral supplementary motor regions. In contrast, higher convergence in studies with adults was identified in bilateral posterior OT/cerebellar and left dorsal precentral regions. The results are discussed in relation to current neuroanatomical models of reading and tentative functional interpretations of reading-related activation clusters in children and adults are provided. Hum Brain Mapp, 2015. © 2014 Wiley Periodicals, Inc.
Developmental dyslexia has been the focus of much functional anatomical research. The main trust of this work is that typical developmental dyslexics have a dysfunction of the phonological and orthography to phonology conversion systems, in which the left occipito-temporal cortex has a crucial role. It remains to be seen whether there is a systematic co-occurrence of dysfunctional patterns of different functional systems perhaps converging on the same brain regions associated with the reading deficit. Such evidence would be relevant for theories like, for example, the magnocellular/attentional or the motor/cerebellar ones, which postulate a more basic and anatomically distributed disorder in dyslexia. We addressed this issue with a meta-analysis of all the imaging literature published until September 2013 using a combination of hierarchical clustering and activation likelihood estimates. The clustering analysis on 2360 peaks identified 193 clusters, 92 of which proved significant for spatial extent. Following binomial tests on the clusters, we found left hemispheric network specific for normal controls (i.d. of reduced involvement in dyslexics) involving the left inferior frontal, premotor, supramarginal cortices and the left infero-temporal and fusiform region: these were specific for reading and the visual-to-phonology processes. There was also a more dorsal left fronto-parietal network: these clusters included peaks from tasks involving phonological manipulation, but also motoric or visuo-spatial perception/attention. No cluster was identified in area V5 for no task, nor in cerebellar clusters either. We conclude that the available literature demonstrates a specific lack of activation of the left occipitotemporal cortex in dyslexics that is specific for reading and reading-like behaviours and for visuo-phonological tasks. Additional deficits may be associated with altered functionality of dorsal fronto-parietal cortex.
Over the last 20 years, reading has been the focus of much research using functional imaging. A formal assessment of the implications of this work for a more general understanding of reading processes is still lacking. We performed a new meta-analysis based on an optimized hierarchical clustering algorithm which automatically groups activation peaks into clusters; the functional role of the clusters was assessed on the basis of statistical criteria. We considered the literature from 1992 to 2008, focussing exclusively on experiments based on single words or pseudowords from the following four classes of tasks: reading, lexical decision, phonological decision and semantic tasks. Our analysis was restricted to alphabetic orthographies and was based on 35 studies. We identified three networks: (1) a difficulty modulated network including Broca's area and attention-related brain regions; (2) a word-related network, primarily involving regions of the left temporal lobe and of the anterior fusiform region, known to participate to semantic processes; (3) a pseudoword-related network in the basal occipito-temporal regions and in the left inferior parietal cortex. These subnetworks constitute the basis upon which a plausible functional model of reading is proposed, where orthographic, phonological, and semantic processes are recruited to compute the phonology of a written stimulus based on cooperative and competitive mechanisms. The results of this meta-analysis held face validity when compared with the results of literature published until mid 2010, the time of completion of data collection.
Strong evidence exists for a key role of the human ventral occipitotemporal cortex (vOT) in reading, yet there have been conflicting reports about the specificity of this area in orthographic versus nonorthographic processing. We suggest that the inconsistencies in the literature can be explained by the method used to identify regions that respond to words. Here we provide evidence that the "visual word form area" (VWFA) shows word selectivity when identified at the individual subject level, but that intersubject variability in the location and size of the VWFA causes this selectivity to be washed out if defining the VWFA at the group level or based on coordinates from the literature. Our findings confirm the existence of a word-selective region in vOT while providing an explanation for why other studies have found a lack of word specificity in vOT.
Despite a large body of research, extant findings on the functional role of left inferior frontal gyrus (LIFG) in phonological and semantic fluency are still controversial. Based on cross-study comparisons, a recent meta-analysis of neuroimaging results suggests that posterior-dorsal (Brodmann area, BA, 44) and anterior-ventral parts (BA 45) of LIFG contribute differentially to processes of phonologically and semantically cued word retrieval, respectively. In contrast, a subsequent functional magnetic resonance imaging experiment failed to validate the proposed dissociation using a within-subjects design. In particular, no evidence for a specific role of BA 45 in semantic fluency was found. Here, we resolve this apparent controversy by showing that the conflicting findings can be accounted for when considering the influence of task demands and individual ability on resulting functional magnetic resonance imaging activation patterns. By comparing phonological versus semantic fluency, higher activation was robustly observed in BA 44. For the opposite comparison, higher activation was found in dorsal BA 45; however, this was more pronounced in posterior-dorsal parts of BA 45 for low-performing subjects and was only apparent in anterior-dorsal parts of BA 45 under high demands on controlled semantic retrieval. Our results thus disclose important determinants for detecting a functional segregation of LIFG in verbal fluency that also have implications for the controversial findings in previous lesion studies. Moreover, the present parcellation of dorsal BA 45 corresponds well with anatomical evidence suggesting a subdivision into an anterior (45A) and posterior part (45B) and may therefore represent evidence for its functional significance in humans.
White matter tissue properties are highly correlated with reading proficiency; we would like to have a model that relates
the dynamics of an individual’s white matter development to their acquisition of skilled reading. The development of cerebral
white matter involves multiple biological processes, and the balance between these processes differs between individuals.
Cross-sectional measures of white matter mask the interplay between these processes and their connection to an individual’s
cognitive development. Hence, we performed a longitudinal study to measure white-matter development (diffusion-weighted imaging)
and reading development (behavioral testing) in individual children (age 7–15 y). The pattern of white-matter development
differed significantly among children. In the left arcuate and left inferior longitudinal fasciculus, children with above-average
reading skills initially had low fractional anisotropy (FA) that increased over the 3-y period, whereas children with below-average
reading skills had higher initial FA that declined over time. We describe a dual-process model of white matter development
comprising biological processes with opposing effects on FA, such as axonal myelination and pruning, to explain the pattern
of results.
The authors examined the regularity effect on reading aloud as a function of left-to-right phonemic position of irregularity in low-frequency exception words. Ss named 96 low-frequency exception words categorized into 5 conditions on the basis of the position (1st through 5th) of their 1st irregular grapheme-to-phoneme correspondence (GPC). Latencies and error rates for these words were compared with the rates for 96 matched GPC regular controls. Results showed that the cost of irregularity decreased monotonically over the 5 positions of irregularity. This result is offered as evidence for dual-route models of reading and against parallel distributed processing models of reading. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Reading in many alphabetic writing systems depends on both item-specific knowledge used to read irregular words (sew, yacht) and generative spelling-sound knowledge used to read pseudowords (tew, yash). Research into the neural basis of these abilities has been directed largely by cognitive accounts proposed by the dual-route cascaded and triangle models of reading. We develop a framework that enables predictions for neural activity to be derived from cognitive models of reading using 2 principles: (a) the extent to which a model component or brain region is engaged by a stimulus and (b) how much effort is exerted in processing that stimulus. To evaluate the derived predictions, we conducted a meta-analysis of 36 neuroimaging studies of reading using the quantitative activation likelihood estimation technique. Reliable clusters of activity are localized during word versus pseudoword and irregular versus regular word reading and demonstrate a great deal of convergence between the functional organization of the reading system put forward by cognitive models and the neural systems activated during reading tasks. Specifically, left-hemisphere activation clusters are revealed reflecting orthographic analysis (occipitotemporal cortex), lexical and/or semantic processing (anterior fusiform, middle temporal gyrus), spelling-sound conversion (inferior parietal cortex), and phonological output resolution (inferior frontal gyrus). Our framework and results establish that cognitive models of reading are relevant for interpreting neuroimaging studies and that neuroscientific studies can provide data relevant for advancing cognitive models. This article thus provides a firm empirical foundation from which to improve integration between cognitive and neural accounts of the reading process. (PsycINFO Database Record (c) 2012 APA, all rights reserved).
We present behavioral and anatomical evidence for a multi-component reading system in which
different components are differentially weighted depending on culture-specific demands of orthography.
Italian orthography is consistent, enabling reliable conversion of graphemes to phonemes to
yield correct pronunciation of the word. English orthography is inconsistent, complicating mapping
of letters to word sounds. In behavioral studies, Italian students showed faster word and non-word
reading than English students. In two PET studies, Italians showed greater activation in left superior
temporal regions associated with phoneme processing. In contrast, English readers showed greater
activations, particularly for non-words, in left posterior inferior temporal gyrus and anterior inferior
frontal gyrus, areas associated with word retrieval during both reading and naming tasks.
Diffusion tensor imaging tractography is a structural magnetic resonance imaging technique allowing reconstruction and assessment of the integrity of three dimensional white matter tracts, as indexed by their fractional anisotropy. It is assumed that the left arcuate fasciculus plays a crucial role for reading development, as it connects two regions of the reading network, the left temporoparietal region and the left inferior frontal gyrus, for which atypical functional activation and lower fractional anisotropy values have been reported in dyslexic readers. In addition, we explored the potential role of the left inferior fronto-occipital fasciculus, which might connect a third region of the reading network, the left ventral occipitotemporal region with the left inferior frontal gyrus. In the present study, 20 adults with dyslexia and 20 typical reading adults were scanned using diffusion tensor imaging, and the bilateral arcuate fasciculus and the left inferior fronto-occipital fasciculus were delineated. Group comparisons show a significantly reduced fractional anisotropy in the left arcuate fasciculus of adults with dyslexia, in particular in the segment that directly connects posterior temporal and frontal areas. This fractional anisotropy reduction might reflect a lower degree of myelination in the dyslexic sample, as it co-occurred with a group difference in radial diffusivity. In contrast, no significant group differences in fractional anisotropy were found in the right arcuate fasciculus or in the left inferior fronto-occipital fasciculus. Correlational analyses (controlled for reading status) demonstrated a specific relation between performance on phoneme awareness and speech perception and the integrity of left arcuate fasciculus as indexed by fractional anisotropy, and between orthographic processing and fractional anisotropy values in left inferior fronto-occipital fasciculus. The present study reveals structural anomalies in the left arcuate fasciculus in adults with dyslexia. This finding corroborates current hypotheses of dyslexia as a disorder of network connections. In addition, our study demonstrates a correlational double dissociation, which might reflect neuroanatomical correlates of the dual route reading model: the left arcuate fasciculus seems to sustain the dorsal phonological route underlying grapheme-phoneme decoding, while the left inferior fronto-occipital fasciculus seems to sustain the ventral orthographic route underlying reading by direct word access.
In the present study, we used event-related functional magnetic resonance imaging (fMRI) to explore the different roles of the posterior inferior frontal gyrus (pIFG) in Chinese character form judgment between literate and illiterate subjects. Using event-related fMRI, 24 healthy right-handed Chinese subjects (12 literates and 12 illiterates) were asked to perform Chinese character and figure form judgment tasks. The blood oxygen level-dependent (BOLD) differences in pIFG were examined with general linear modeling (GLM). We found differences in reaction times and accuracy between subjects as they performed these tasks. These behavioral differences reflect the different cognitive demands of character form judgment for literate and illiterate individuals. The results showed differences in the BOLD response patterns in the pIFG between the two discrimination tasks and the two subject groups. A comparison of the character and figure tasks showed that literate and illiterate subjects had similar BOLD responses in the inferior frontal gyrus. However, differences in behavioral performance suggest that the pIFG plays a different role in Chinese character form judgment for each subject group. In literate subjects, the left pIFG mediated access to phonology in achieving Chinese character form judgment, whereas the right pIFG participated in the processing of the orthography of Chinese characters. In illiterate subjects, the bilateral frontal gyrus participated in the visual-spatial processing of Chinese characters to achieve form judgment.
Task-based neuroimaging studies face the challenge of developing tasks capable of equivalently probing reading networks across different age groups. Resting-state fMRI, which requires no specific task, circumvents these difficulties. Here, in 25 children (8-14 years) and 25 adults (21-46 years), we examined the extent to which individual differences in reading competence can be related to resting-state functional connectivity (RSFC) of regions implicated in reading. In both age groups, reading standard scores correlated positively with RSFC between the left precentral gyrus and other motor regions, and between Broca's and Wernicke's areas. This suggests that, regardless of age group, stronger coupling among motor regions, as well as between language/speech regions, subserves better reading, presumably reflecting automatized articulation. We also observed divergent RSFC-behavior relationships in children and adults, particularly those anchored in the left fusiform gyrus (FFG) (the visual word form area). In adults, but not children, better reading performance was associated with stronger positive correlations between FFG and phonology-related regions (Broca's area and the left inferior parietal lobule), and with stronger negative relationships between FFG and regions of the "task-negative" default network. These results suggest that both positive RSFC (functional coupling) between reading regions and negative RSFC (functional segregation) between a reading region and default network regions are important for automatized reading, characteristic of adult readers. Together, our task-independent RSFC findings highlight the importance of appreciating developmental changes in the neural correlates of reading competence, and suggest that RSFC may serve to facilitate the identification of reading disorders in different age groups.
The ventral occipitotemporal cortex (vOT) is involved in the perception of visually presented objects and written words. The Interactive Account of vOT function is based on the premise that perception involves the synthesis of bottom-up sensory input with top-down predictions that are generated automatically from prior experience. We propose that vOT integrates visuospatial features abstracted from sensory inputs with higher level associations such as speech sounds, actions and meanings. In this context, specialization for orthography emerges from regional interactions without assuming that vOT is selectively tuned to orthographic features. We discuss how the Interactive Account explains left vOT responses during normal reading and developmental dyslexia; and how it accounts for the behavioural consequences of left vOT damage.
We examined the evidence from functional imaging studies for predominance of a phonological left temporo-parietal (TP) dysfunction in dyslexic children and predominance of a visual-orthographic left occipito-temporal (OT) dysfunction in dyslexic adults. Separate meta-analyses of 9 studies with children (age means: 9-11 years) and of 9 studies with adults (age means: 18-30 years) and statistical comparison of these meta-analytic maps did find support for a dysfunction of a left ventral OT region in both children and adults. The findings on a possible predominance of a left TP dysfunction in children were inconclusive. Contrary to expectation, underactivation in superior temporal regions was only found for adults, but not for children. For children, underactivation was found in bilateral inferior parietal regions, but this abnormality was no longer present when foci identified by higher dyslexic task-negative activation (i.e., deactivation in response to reading compared to baseline) were excluded. These meta-analytic results are consistent with recent findings speaking for an early engagement of left OT regions in reading development and for an early failure of such an engagement in dyslexia.
Although interactivity is considered a fundamental principle of cognitive (and computational) models of reading, it has received far less attention in neural models of reading that instead focus on serial stages of feed-forward processing from visual input to orthographic processing to accessing the corresponding phonological and semantic information. In particular, the left ventral occipito-temporal (vOT) cortex is proposed to be the first stage where visual word recognition occurs prior to accessing nonvisual information such as semantics and phonology. We used functional magnetic resonance imaging (fMRI) to investigate whether there is evidence that activation in vOT is influenced top-down by the interaction of visual and nonvisual properties of the stimuli during visual word recognition tasks. Participants performed two different types of lexical decision tasks that focused on either visual or nonvisual properties of the word or word-like stimuli. The design allowed us to investigate how vOT activation during visual word recognition was influenced by a task change to the same stimuli and by a stimulus change during the same task. We found both stimulus- and task-driven modulation of vOT activation that can only be explained by top-down processing of nonvisual aspects of the task and stimuli. Our results are consistent with the hypothesis that vOT acts as an interface linking visual form with nonvisual processing in both bottom up and top down directions. Such interactive processing at the neural level is in agreement with cognitive and computational models of reading but challenges some of the assumptions made by current neuro-anatomical models of reading.
Tracing the connections from brain functions to children's cognitive development and education is a major goal of modern neuroscience. We performed the first meta-analysis of functional magnetic resonance imaging (fMRI) data obtained over the past decade (1999-2008) on more than 800 children and adolescents in three core systems of cognitive development and school learning: numerical abilities, reading, and executive functions (i.e. cognitive control). We ran Activation Likelihood Estimation (ALE) meta-analyses to obtain regions of reliable activity across all the studies. The results indicate that, unlike results usually reported for adults, children primarily engage the frontal cortex when solving numerical tasks. With age, there may be a shift from reliance on the frontal cortex to reliance on the parietal cortex. In contrast, the frontal, temporo-parietal and occipito-temporal regions at work during reading in children are very similar to those reported in adults. The executive frontal regions are also consistent with the imaging literature on cognitive control in adults, but the developmental comparison between children and adolescents demonstrates a key role of the anterior insular cortex (AIC) with an additional right AIC involvement in adolescents.
Developmental dyslexia is a severe reading disorder, which is characterized by dysfluent reading and impaired automaticity of visual word processing. Adults with dyslexia show functional deficits in several brain regions including the so-called "Visual Word Form Area" (VWFA), which is implicated in visual word processing and located within the larger left occipitotemporal VWF-System. The present study examines functional connections of the left occipitotemporal VWF-System with other major language areas in children with dyslexia. Functional connectivity MRI was used to assess connectivity of the VWF-System in 18 children with dyslexia and 24 age-matched controls (age 9.7-12.5 years) using five neighboring left occipitotemporal regions of interest (ROIs) during a continuous reading task requiring phonological and orthographic processing. First, the results revealed a focal origin of connectivity from the VWF-System, in that mainly the VWFA was functionally connected with typical left frontal and parietal language areas in control children. Adjacent posterior and anterior VWF-System ROIs did not show such connectivity, confirming the special role that the VWFA plays in word processing. Second, we detected a significant disruption of functional connectivity between the VWFA and left inferior frontal and left inferior parietal language areas in the children with dyslexia. The current findings add to our understanding of dyslexia by showing that functional disconnection of the left occipitotemporal system is limited to the small VWFA region crucial for automatic visual word processing, and emerges early during reading acquisition in children with dyslexia, along with deficits in orthographic and phonological processing of visual word forms.
Resting-state functional connectivity (RSFC) approaches offer a novel tool to delineate distinct functional networks in the brain. In the present functional magnetic resonance imaging (fMRI) study, we elucidated patterns of RSFC associated with 6 regions of interest selected primarily from a meta-analysis on word reading (Bolger DJ, Perfetti CA, Schneider W. 2005. Cross-cultural effect on the brain revisited: universal structures plus writing system variation. Hum Brain Mapp. 25: 92-104). In 25 native adult readers of English, patterns of positive RSFC were consistent with patterns of task-based activity and functional connectivity associated with word reading. Moreover, conjunction analyses highlighted the posterior left inferior frontal gyrus and the posterior left middle temporal gyrus (post-LMTG) as potentially important loci of functional interaction among 5 of the 6 reading networks. The significance of the post-LMTG has typically been unappreciated in task-based studies on unimpaired readers but is frequently reported to be a locus of hypoactivity in dyslexic readers and exhibits intervention-induced changes of activity in dyslexic children. Finally, patterns of negative RSFC included not only regions of the so-called default mode network but also regions involved in effortful controlled processes, which may not be required once reading becomes automatized. In conclusion, the current study supports the utility of resting-state fMRI for investigating reading networks and has direct relevance for the understanding of reading disorders such as dyslexia.
Developmental dyslexia has been associated with a dysfunction of a brain region in the left inferior occipitotemporal cortex, called the "visual word-form area" (VWFA). In adult normal readers, the VWFA is specialized for print processing and sensitive to the orthographic familiarity of letter strings. However, it is still unclear whether these two levels of occipitotemporal specialization are affected in developmental dyslexia. Specifically, we investigated whether (a) these two levels of specialization are impaired in dyslexic children with only a few years of reading experience and (b) whether this impairment is confined to the left inferior occipitotemporal VWFA, or extends to adjacent regions of the "VWF-system" with its posterior-anterior gradient of print specialization. Using fMRI, we measured brain activity in 18 dyslexic and 24 age-matched control children (age 9.7-12.5 years) while they indicated if visual stimuli (real words, pseudohomophones, pseudowords and false-fonts) sounded like a real word. Five adjacent regions of interest (ROIs) in the bilateral occipitotemporal cortex covered the full anterior-posterior extent of the VWF-system. We found that control and dyslexic children activated the same main areas within the reading network. However, a gradient of print specificity (higher anterior activity to letter strings but higher posterior activity to false-fonts) as well as a constant sensitivity to orthographic familiarity (higher activity for unfamiliar than familiar word-forms) along the VWF-system could only be detected in controls. In conclusion, analyzing responses and specialization profiles along the left VWF-system reveals that children with dyslexia show impaired specialization for both print and orthography.
A rhyming and short-term memory task with visually presented letters were used to study brain activity in five compensated adult developmental dyslexics. Their only cognitive difficulty was in phonological processing, manifest in a wide range of tasks including spoonerisms, phonemic fluency and digit naming speed. PET scans showed that for the dyslexics, a subset only of the brain regions normally involved in phonological processing was activated: Broca's area during the rhyming task, temporo-parietal cortex during the short- term memory task. In contrast to normal controls these areas were not activated in concert. Furthermore the left insula was never activated. We propose that the defective phonological system of these dyslexics is due to weak connectivity between anterior and posterior language areas. This could be due to a dysfunctional left insula which may normally act as an anatomical bridge between Broca's area, superior temporal and inferior parietal cortex. The independent activation of the posterior and anterior speech areas in dyslexics supports the notion that representations of unsegmented and segmented phonology are functionally and anatomically separate.
Pronunciation (of irregular/inconsistent words and of pseudowords) and lexical decision-making tasks were used with 15O PET to examine the neural correlates of phonological and orthographic processing in 14 healthy right-handed men (aged 18-40 years). Relative to a visual-fixation control task, all four experimental tasks elicited a left-lateralized stream of activation involving the lingual and fusiform gyri, perirolandic cortex, thalamus and anterior cingulate. Both pronunciation tasks activated the left superior temporal gyrus, with significantly greater activation seen there during phonological (pseudoword) than during orthographic (real word) pronunciation. The left inferior frontal cortex was activated by both decision-making tasks; more intense and widespread activation was seen there during phonological, than during orthographic, decision making, with the activation during phonological decision-making extending into the left insula. Correlations of reference voxels in the left superior temporal gyrus and left inferior frontal region with the rest of the brain were highly similar for the phonological and orthographic versions of each task type. These results are consistent with connectionist models of reading, which hypothesize that both real words and pseudowords are processed within a common neural network.
This review discusses how neuroimaging can contribute to our understanding of a fundamental aspect of skilled reading: the ability to pronounce a visually presented word. One contribution of neuroimaging is that it provides a tool for localizing brain regions that are active during word reading. To assess the extent to which similar results are obtained across studies, a quantitative review of nine neuroimaging investigations of word reading was conducted. Across these studies, the results converge to reveal a set of areas active during word reading, including left-lateralized regions in occipital and occipitotemporal cortex, the left frontal operculum, bilateral regions within the cerebellum, primary motor cortex, and the superior and middle temporal cortex, and medial regions in the supplementary motor area and anterior cingulate. Beyond localization, the challenge is to use neuroimaging as a tool for understanding how reading is accomplished. Central to this challenge will be the integration of neuroimaging results with information from other methodologies. To illustrate this point, this review will highlight the importance of spelling-to-sound consistency in the transformation from orthographic (word form) to phonological (word sound) representations, and then explore results from three neuroimaging studies in which the spelling-to-sound consistency of the stimuli was deliberately varied. Emphasis is placed on the pattern of activation observed within the left frontal cortex, because the results provide an example of the issues and benefits involved in relating neuroimaging results to behavioral results in normal and brain damaged subjects, and to theoretical models of reading.
Recognition of a specific visual target among equally familiar distracters requires neural mechanisms for tracking items in working memory. Event-related functional magnetic resonance imaging revealed evidence for two such mechanisms: (i) Enhanced neural responses, primarily in the frontal cortex, were associated with the target and were maintained across repetitions of the target. (ii) Reduced responses, primarily in the extrastriate visual cortex, were associated with stimulus repetition, regardless of whether the stimulus was a target or a distracter. These complementary neural mechanisms track the status of familiar items in working memory, allowing for the efficient recognition of a currently relevant object and rejection of irrelevant distracters.
The purpose of this study was to examine changes in regional cerebral blood flow (rCBF) using positron emission tomography (PET) during overt word and nonword reading tasks to determine structures involved in semantic processing. Ten young, healthy, right-handed subjects were scanned 12 times, twice in each of six specific conditions. Blood flow was measured by ¹⁵O-water using standard PET imaging technology. The rCBFs during different cognitive conditions were compared by using analysis of covariance (SPM94), which resulted in three-dimensional maps of those brain regions more active in one condition relative to another. When the subjects read aloud words with difficult or unusual grapheme-phoneme translations (i.e., third-order approximation to English or irregularly spelled real words), increases in activation were seen in the inferior frontal cortex. When subjects were reading aloud regular and irregular words (which had important semantic components relative to nonwords), activation of the fusiform gyrus was seen. These data are broadly consistent with brain regions generally associated with reading based on other neuropsychological paradigms, and they emphasize the multicomponent aspects of this complex cognitive process. Hum. Brain Mapping 5:84–92, 1997. © 1997 Wiley-Liss Inc.
In recent years, significant progress has been made in the study of reading and read- ing disability with the use of functional neuroimaging techniques. There is substan- tial converging evidence that skilled word recognition requires the development of a highly integrated cortical system that includes left hemisphere dorsal, ventral, and anterior subsystems. This article highlights key findings regarding the functional role of these regions during skilled reading, the developmental trajectory toward this ma- ture reading circuitry in normally developing children, deviations from this trajectory in populations with reading disabilities, and the ways in which successful reading remediation alters the brain organization for reading. We present one possible inter- pretation of these findings and report some recent findings from our lab that continue to refine our understanding of the functional properties of each component region an