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The neural correlates of coloured music: A functional MRI investigation of auditory-visual synaesthesia
Abstract
In auditory-visual synaesthesia, all kinds of sound can induce additional visual experiences. To identify the brain regions mainly involved in this form of synaesthesia, functional magnetic resonance imaging (fMRI) has been used during non-linguistic sound perception (chords and pure tones) in synaesthetes and non-synaesthetes. Synaesthetes showed increased activation in the left inferior parietal cortex (IPC), an area involved in multimodal integration, feature binding and attention guidance. No significant group-differences could be detected in area V4, which is known to be related to colour vision and form processing. The results support the idea of the parietal cortex acting as sensory nexus area in auditory-visual synaesthesia, and as a common neural correlate for different types of synaesthesia.
... Knowledge about the neurophysiological processes in AV synesthesia is relatively sparse due to the small number of accessible subjects. Yet, parietal involvement in AV synesthesia has been demonstrated in multiple functional studies using fMRI [Neufeld et al., 2012a[Neufeld et al., , 2012b or electroencephalography (EEG) [J€ ancke and Langer, 2011]. Moreover, the parietal lobe has turned out to be strongly interconnected to other brain regions, even during RS [J€ ancke and Langer, 2011]. ...
... The Juelich Histological and the Harvard-Oxford cortical atlases (http://fsl.fmrib.ox.ac.uk/fsl/ fslwiki/Atlases; implemented in fMRIB software library: http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FSL) were used for a more detailed specification of brain regions. The ROIs for the left and right V4 were derived from an fMRI study performed with AV synesthetes [Neufeld et al., 2012a]. Based on previous work [Esterman et al., 2006;J€ ancke and Langer, 2011;Neufeld et al., 2012b] and to increase the power of our analysis, we selected a single medial ROI in the superior parietal lobe showing the highest mean current density across all subjects. ...
... To investigate AV synesthesia on a global scale, we also evaluated undirected connectivity between 29 ROIs (Table I). The selected ROIs were chosen according to previous studies in AV synesthesia showing the involvement of primary and secondary auditory- [Beeli et al., 2008;J€ ancke and Langer, 2011;J€ ancke et al., 2012]; primary and secondary visual- [Beeli et al., 2008;J€ ancke et al., 2012;Neufeld et al., 2012b]; parietal- [J€ ancke and Langer, 2011;Neufeld et al., 2012aNeufeld et al., , 2012b; and frontal brain areas [Beeli et al., 2008;Dovern et al., 2012]. As a consequence of sLORETAs smoothing parameter [Pascual-Marqui, 2002] and to guarantee that individual ROIs indeed reflected distinct functional areas, we set a minimum of 1.5 cm as inter-ROI distance. ...
Auditory-visual (AV) synesthesia is a rare phenomenon in which an auditory stimulus induces a “concurrent” color sensation. Current neurophysiological models of synesthesia mainly hypothesize “hyperconnected” and “hyperactivated” brains, but differ in the directionality of signal transmission. The two-stage model proposes bottom-up signal transmission from inducer- to concurrent- to higher-order brain areas, whereas the disinhibited feedback model postulates top-down signal transmission from inducer- to higher-order- to concurrent brain areas. To test the different models of synesthesia, we estimated local current density, directed and undirected connectivity patterns in the intracranial space during two minutes of resting-state (RS) EEG in 11 AV synesthetes and 11 non-synesthetes. AV synesthetes demonstrated increased parietal theta, alpha and lower beta current density compared to non-synesthetes. Further, AV synesthetes were characterized by increased top-down signal transmission from the superior parietal lobe to the left color processing area V4 in the upper beta frequency band. Analyses of undirected connectivity revealed a global, synesthesia-specific hyperconnectivity in the alpha frequency band.
The involvement of the superior parietal lobe even during rest is a strong indicator for its key role in AV synesthesia. By demonstrating top-down signal transmission in AV synesthetes, we provide direct support for the disinhibited feedback model of synesthesia. Finally, we suggest that synesthesia is a consequence of global hyperconnectivity.
... We shall also report in this section the results of four more studies on different types of synesthesia Frontiers in Human Neuroscience www.frontiersin.org Bor et al., 2007;Tang et al., 2008;Jones et al., 2011;Neufeld et al., 2012a). We did not include here three other fMRI studies that tested groups of synesthetes and controls but did not report the statistical comparison between both groups ( Table 1, first section: Nunn et al., 2002;Gray et al., 2006;Rich et al., 2006). ...
... Note that classical statistical models may not be appropriate when comparing one subject to a group: the results critically depend on the construction of the group and may require very large control groups (e.g., Nocchi et al., 2008). Tang et al. (2008) and Neufeld et al. (2012a) compared nonsynesthetes to, respectively, a group of 10 synesthetes with number form and a group of 14 tone-color synesthetes, but they did not include any control stimulus. Tang et al. (2008) focused on interaction effects for different tasks that all involved synesthetic stimuli. ...
... When contrasting numbers that evoked number lines to baseline in the group of synesthetes alone (they did not report the comparison with controls), these stimuli did not evoke any significant response in the posterior intraparietal sulcus (IPS), the region previously argued to be involved in spatial processing (Hubbard et al., 2005b). Neufeld et al. (2012a) measured a stronger activation to tones for synesthetes compared to controls in the left inferior parietal cortex (they performed conservative voxelwise statistics with additional cluster extent threshold), but this activation lacked specificity (tones were contrasted against baseline). Rouw and Scholte (2010) had also reported a significant cluster in the parietal cortex. ...
Synesthesia refers to additional sensations experienced by some people for specific stimulations, such as the systematic arbitrary association of colors to letters for the most studied type. Here, we review all the studies (based mostly on functional and structural magnetic resonance imaging) that have searched for the neural correlates of this subjective experience, as well as structural differences related to synesthesia. Most differences claimed for synesthetes are unsupported, due mainly to low statistical power, statistical errors, and methodological limitations. Our critical review therefore casts some doubts on whether any neural correlate of the synesthetic experience has been established yet. Rather than being a neurological condition (i.e., a structural or functional brain anomaly), synesthesia could be reconsidered as a special kind of childhood memory, whose signature in the brain may be out of reach with present brain imaging techniques.
... Coloured-hearing synesthesia (CHS) is a perceptual phenomenon in which auditory stimuli cause additional colour experiences. To date, different forms of CHS have been reported, comprising tone-colour [1,2], spoken word-colour [1], music-colour [3], or general auditorycolour synesthesia [4]. The common denominator of all these synesthesia variants is a close relationship between auditory and visual perceptual representations. ...
... Whereas visual inputs into the auditory cortex have been described in humans [15,[37][38][39], non-human primates [40,41], and ferrets [42], a modulation of the auditory cortex may also be mediated by thalamo-cortical interactions [43] and/or feedback loops from multisensory brain areas to the auditory cortex [5], or even by multimodal response properties of neurons situated in the primary auditory cortex and posterior belt areas [44]. The few brain-imaging [3,15,35,45,46] and electrophysiological [1,36,47] studies dedicated to investigate the neural underpinnings of CHS have reported conflicting findings with respect to brain responses in the auditory cortex. In fact, some authors provided evidence for a modulation of auditory-related brain regions in CH synesthetes [1,15,35,36], whereas others could not confirm this finding [3,[45][46][47]. ...
... The few brain-imaging [3,15,35,45,46] and electrophysiological [1,36,47] studies dedicated to investigate the neural underpinnings of CHS have reported conflicting findings with respect to brain responses in the auditory cortex. In fact, some authors provided evidence for a modulation of auditory-related brain regions in CH synesthetes [1,15,35,36], whereas others could not confirm this finding [3,[45][46][47]. ...
Background
Coloured-hearing (CH) synesthesia is a perceptual phenomenon in which an acoustic stimulus (the inducer) initiates a concurrent colour perception (the concurrent). Individuals with CH synesthesia "see" colours when hearing tones, words, or music; this specific phenomenon suggesting a close relationship between auditory and visual representations. To date, it is still unknown whether the perception of colours is associated with a modulation of brain functions in the inducing brain area, namely in the auditory-related cortex and associated brain areas. In addition, there is an on-going debate as to whether attention to the inducer is necessarily required for eliciting a visual concurrent, or whether the latter can emerge in a pre-attentive fashion.
Results
By using the EEG technique in the context of a pre-attentive mismatch negativity (MMN) paradigm, we show that the binding of tones and colours in CH synesthetes is associated with increased MMN amplitudes in response to deviant tones supposed to induce novel concurrent colour perceptions. Most notably, the increased MMN amplitudes we revealed in the CH synesthetes were associated with stronger intracerebral current densities originating from the auditory cortex, parietal cortex, and ventral visual areas.
Conclusions
The automatic binding of tones and colours in CH synesthetes is accompanied by an early pre-attentive process recruiting the auditory cortex, inferior and superior parietal lobules, as well as ventral occipital areas.
... We focused the analysis on three seeds of interest to calculate the connectivity: the left inferior parietal cortex (IPC) and the bilateral auditory cortex (AC). The areas of interest were defined functionally in our previous study using a standard GLM (general linear model) analysis (Neufeld et al., 2012). The analysis method employed here was introduced previously by Rissman, Gazzaley, and D'Esposito (2004) and allows analysis of the functional connectivity of predefined brain areas in relation to a specific cognitive process in the whole brain. ...
... analysis revealed one significant cluster in the inferior parietal cortex (IPC) for the main effect "group" (this area exhibited stronger activation for auditory stimulation in synesthetes compared to the controls) and two clusters in the right and left auditory cortex (AC) for the main effect "stimulation". The results of this analysis are presented and discussed extensively in Neufeld et al. (2012). The seed areas were defined for the whole group of subjects as a sphere with a 5 mm radius around the center of mass of the previously detected clusters: the left and right AC (lAC, xyz . ...
... Recent research underlines the importance of this area in multimodal sensory perception (Bushara, Grafman, & Hallett, 2001;Calvert, 2001;Macaluso, George, Dolan, Spence, & Driver, 2004;Szycik, Jansma, & Münte, 2009). Furthermore, it has also been identified as a major hub for processing synesthetic perception (Neufeld et al., 2012;Rouw & Scholte, 2007van Leeuwen et al., 2010;Weiss & Fink, 2009;Weiss et al., 2005). Thus, in accordance with the disinhibited feedback model of synesthesia (Grossenbacher & Lovelace, 2001), this area may play a crucial role as a "pathway convergence site" in synesthesia and as the origin of the disinhibited feedback. ...
In synesthesia, certain stimuli to one sensory modality lead to sensory perception in another unstimulated modality. In addition to other models, a two-stage model is discussed to explain this phenomenon, which combines two previously formulated hypotheses regarding synesthesia: direct cross-activation and hyperbinding. The direct cross-activation model postulates that direct connections between sensory-specific areas are responsible for co-activation and synesthetic perception. The hyperbinding hypothesis suggests that the inducing stimulus and the synesthetic sensation are coupled by a sensory nexus area, which may be located in the parietal cortex. This latter hypothesis is compatible with the disinhibited feedback model, which suggests unusual feedback from multimodal convergence areas as the cause of synesthesia. In this study, the relevance of these models was tested in a group (n=14) of auditory-visual synesthetes by performing a functional connectivity analysis on functional magnetic resonance imaging (fMRI) data. Different simple and complex sounds were used as stimuli, and functionally defined seed areas in the bilateral auditory cortex (AC) and the left inferior parietal cortex (IPC) were used for the connectivity calculations. We found no differences in the connectivity of the AC and the visual areas between synesthetes and controls. The main finding of the study was stronger connectivity of the left IPC with the left primary auditory and right primary visual cortex in the group of auditory-visual synesthetes. The results support the model of disinhibited feedback as a cause of synesthetic perception but do not suggest direct cross-activation.
... The next section compares the results of eight neuroimaging studies (Table 1) conducted on synaesthetes with forms of coloured-hearing to examine the evidence for the presence of disinhibited feedback or hyperconnectivity. The studies comprise three functional studies (Goller, Otten, & Ward, 2009;Jäncke, Rogenmoser, Meyer, & Elmer, 2012;Neufeld et al., 2012a) and five structural studies (Banissy et al., 2012;Hänggi, Beeli, Oechslin, & Jäncke, 2008;Zamm et al., 2013;Jäncke & Langer, 2011;Neufeld et al., 2012b). ...
... The detection of difference in the very early stages of processing may have been effected by a large proportion of lower synaesthetes in the group. One important finding is the identification of the role of the parietal cortex (Neufeld et al., 2012a(Neufeld et al., , 2012bJäncke and Langer, 2011) as a potential hub in both the disinhibited feedback and hyperconnectivity/hyperbinding theories. ...
This review provides a commentary on coloured-hearing arising on hearing music: music-colour synaesthesia. Although traditionally explained by the hyperconnectivity theory (Ramachandran & Hubbard, 2001a) and the disinhibited feedback theory (Grossenbacher & Lovelace, 2001) as a purely perceptual phenomenon, the review of eight coloured-hearing neuroimaging studies shows that it may not be assumed that these explanations are directly translatable to music-colour synaesthesia. The concept of 'ideaesthesia' (Nikolić, 2009) and the role of conceptual and semantic inducers challenge the likelihood of a single mechanism underlying the cause of synaesthesia and argue for a move away from a purely sensory to sensory explanation. Finally, music-colour synaesthesia forms a challenge for established philosophical theories and the position of synaesthesia is considered within the larger context of musical qualia.
... The next section compares the results of eight neuroimaging studies (Table 1) conducted on synaesthetes with forms of coloured-hearing to examine the evidence for the presence of disinhibited feedback or hyperconnectivity. The studies comprise three functional studies (Goller, Otten, & Ward, 2009;Jäncke, Rogenmoser, Meyer, & Elmer, 2012;Neufeld et al., 2012a) and five structural studies (Banissy et al., 2012;Hänggi, Beeli, Oechslin, & Jäncke, 2008;Zamm et al., 2013;Jäncke & Langer, 2011;Neufeld et al., 2012b). ...
... The detection of difference in the very early stages of processing may have been effected by a large proportion of lower synaesthetes in the group. One important finding is the identification of the role of the parietal cortex (Neufeld et al., 2012a(Neufeld et al., , 2012bJäncke and Langer, 2011) as a potential hub in both the disinhibited feedback and hyperconnectivity/hyperbinding theories. ...
This review provides a commentary on coloured-hearing arising on hearing music: music-colour synaesthesia. Although traditionally explained by the hyperconnectivity theory (Ramachandran & Hubbard, 2001a) and the disinhibited feedback theory (Grossenbacher & Lovelace, 2001) as a purely perceptual phenomenon, the review of eight coloured-hearing neuroimaging studies shows that it may not be assumed that these explanations are directly translatable to music-colour synaesthesia. The concept of ‘ideaesthesia’ (Nikolić, 2009) and the role of conceptual and semantic inducers challenge the likelihood of a single mechanism underlying the cause of synaesthesia and argue for a move away from a purely sensory to sensory explanation. Finally, music-colour synaesthesia forms a challenge for established philosophical theories and the position of synaesthesia is considered within the larger context of musical qualia.
Key words: synaesthesia/synesthesia; ideaesthesia; concept; music-colour/color; chromesthesia; qualia
... However, the researchers found no advantage for synesthetes in digit span tests, and they argued that the memory advantage for synesthetes was not extraordinary, because their findings of memory advantage only were within one standard deviation above the mean of a comparison sample of typical individuals. Neufeld et al. (2012) conducted an imaging study of 14 auditory-visual synesthetes while the synesthetes were listening to music chords and pure tones. The researchers reported that synesthetes showed increased activation in the left inferior parietal cortex. ...
... This is a brain area known to be involved with feature binding. However, counter to the claim by Terhune et al. (2011) that brain activation in area V4 was involved in synesthesia, Neufeld et al. (2012) found no difference in brain activation in region V4 for synesthetes compared with typical controls. Neufeld et al. (2011) concluded that the inferior parietal cortex acts as a sensory integration hub, noting that evidence suggests this region has many roles, including mediating audiovisual integration, multimodality processing of objects, object processing, mental imagery, and non-synesthetic feature binding. ...
... The literature is not very consistent, however: For example, not all studies of grapheme-color synesthesia report activity in color area V4 for synesthesia . One of the most common findings is excess activity in parietal regions for synesthetes, independent of the specific synesthetic subtype (e.g., Van Leeuwen et al., 2010;Rouw et al., 2011;Neufeld et al., 2012a). Thus, the results may imply a particularly important role of parietal cortex in mediating phenomenal synesthetic experiences. ...
... On the other hand, physiological investigations of synesthesia have discovered the important role of the parietal cortex (Van Leeuwen et al., 2010;Rouw et al., 2011;Neufeld et al., 2012a) and of relating individual differences in synesthetic experiences to the directions of effective connectivity (Van Leeuwen et al., 2011). ...
Synesthesia is a phenomenon in which additional perceptual experiences are elicited by sensory stimuli or cognitive concepts. Synesthetes possess a unique type of phenomenal experiences not directly triggered by sensory stimulation. Therefore, for better understanding of consciousness it is relevant to identify the mental and physiological processes that subserve synesthetic experience. In the present work we suggest several reasons why synesthesia has merit for research on consciousness. We first review the research on the dynamic and rapidly growing field of the studies of synesthesia. We particularly draw attention to the role of semantics in synesthesia, which is important for establishing synesthetic associations in the brain. We then propose that the interplay between semantics and sensory input in synesthesia can be helpful for the study of the neural correlates of consciousness, especially when making use of ambiguous stimuli for inducing synesthesia. Finally, synesthesia-related alterations of brain networks and functional connectivity can be of merit for the study of consciousness.
... The neuronal mechanisms underlying synesthesia still remain to be clarified. In GCS, there is evidence of the involvement of visual, parietal, and frontal brain areas (Rouw et al., 2011), whereas involvement of the parietal cortex has also been found in sequence-space (Tang et al., 2008) and (language-unrelated) auditory-visual synesthesia (Neufeld et al., 2012a). that co-occurrence of AS and synesthesia might increase the likelihood of savantism. ...
... Increased activation in associative cortex regions involved in higher order sensory processing has been found in ASC individuals in the visual domain (Samson et al., 2012), while increased functional connectivity between frontal areas (Noonan et al., 2009) and between posterior cingulate and medial temporal cortex (Monk et al., 2009) has been found using fMRI. In synesthesia, the parietal cortex especially has been found to be hyperactivated in different types of synesthesia (Tang et al., 2008;Rouw et al., 2011;Neufeld et al., 2012a) and this region has also been found to be more strongly connected to the sensory areas involved in inducer-and concurrent processing (van Leeuwen et al., 2011;Sinke et al., 2012;Neufeld et al., 2012b), supporting the idea of top-down modulation of sensory areas by this higher-order associative region. It has been suggested in the socalled two-stage model that a combination of both increased local connectivity between sensory brain reagions and modulation of these connections by higher-order areas may be a mechanism of synesthesia Hubbard, 2007). ...
There is increasing evidence from case reports that synesthesia is more common in individuals with autism spectrum conditions (ASC). Further, genes related to synesthesia have also been found to be linked to ASC and, similar to synaesthetes, individuals with ASC show altered brain connectivity and unusual brain activation during sensory processing. However, up to now a systematic investigation of whether synesthesia is more common in ASC patients is missing. The aim of the current pilot study was to test this hypothesis by investigating a group of patients diagnosed with Asperger Syndrome (AS) using questionnaires and standard consistency tests in order to classify them as grapheme-color synaesthetes. The results indicate that there are indeed many more grapheme-color synaesthetes among AS patients. This finding is discussed in relation to different theories regarding the development of synesthesia as well as altered sensory processing in autism.
... Synesthesia is a conditioned reflex that automatically and continuously triggers the production of other sensations when stimulated by one particular sensation [26]. Li et al. [27] reported that stimuli in the form of light and sound could trigger people's synesthetic experiences; thus, aural stimuli (particularly music) can trigger sensations of color, texture, or shape. ...
To promote creative aging, this study designed an interactive device (called FEEL2) and a complementary activity for older adults to experience the synesthesia of color and music. We implemented two iterations of a four-stage approach according to action research methodology. Through this approach, the design of FEEL2 and the accompanying activity was refined on the basis of the feedback and experiences of older adult participants. According to the participants, FEEL2 and the complementary activity enabled them to experience the synesthesia of color and music, apply new media, work both individually and in groups, in addition to being user-friendly, thus developing their potential in artistic creation. Furthermore, this activity allowed them to view their later life more positively, and increase contact with their friends and family. Accordingly, FEEL2 is a suitable tool for helping older adults to experience synesthesia and thus age creatively. Artistic activities are seen as effective ways to promote creative aging, this study provided empirical support for the intervention of the design profession in this field.
... It is a short questionnaire consisting of ten questions that can be answered by both musicians and non-musicians with various degrees of musical experience. The test has been used in different contexts and domains, for example, as a measure of musical expertise [12][13][14]. It has given rise to a significant number of related publications with considerable prevalence in music psychology literature. ...
Quality of life and mental health are topics under discussion in the university environment that pose new educational challenges. Public policy in Chile establishes the need to track students who are starting university and who could find themselves at possible academic risk (Law 20. 903). These transition processes experienced by students therefore need to be guided to improve the students’ quality of life. Using a mixed design, the present study analyzes the association between musical sophistication (Ollen, 2006), students’ well-being, and the performance of first-year students training to be music teachers (n = 25). The Ollen Musical Sophistication questionnaire and the Spanish version of the PERMA-profiler, a questionnaire for assessing well-being, were applied. In order to obtain detailed information about learning processes and educational needs, seven interviews were conducted. Results indicate a negative correlation between musical sophistication on the one hand and negative emotions (anxiety and anger) and loneliness on the other. This is reflected in less consistent academic performance, difficulties in identity development, and reduced motivation to face new challenges besides musical learning. We concluded that knowledge and observation of students’ previous musical experience is crucial for understanding and supporting the educational transition process and well-being of student music teachers.
... The intensity of pleasure experienced from music listening suggests a relation with dopamine reward system of the brain, and neural activity in surrounding limbic regions, indicative of emotional arousal [137][138][139] . Right amygdala showed an increased rs-FC with SI and SLOC in both hemispheres after listening to music, which are parietal areas of somatosensory functions and occipital areas involved in visual mental imagery 140 , and therefore, we suggest that music may engage visual imagery in healthy controls as seen in previous studies 141 . We found increased rs-FC of the AnG with the LG, possibly secondary to visual memory and visuo-limbic processes engaged after listening to music 142 . ...
Listening to self-chosen, pleasant and relaxing music reduces pain in fibromyalgia (FM), a chronic centralized pain condition. However, the neural correlates of this effect are fairly unknown. In our study, we wished to investigate the neural correlates of music-induced analgesia (MIA) in FM patients. To do this, we studied 20 FM patients and 20 matched healthy controls (HC) acquiring rs-fMRI with a 3T MRI scanner, and pain data before and after two 5-min auditory conditions: music and noise. We performed resting state functional connectivity (rs-FC) seed-based correlation analyses (SCA) using pain and analgesia-related ROIs to determine the effects before and after the music intervention in FM and HC, and its correlation with pain reports. We found significant differences in baseline rs-FC between FM and HC. Both groups showed changes in rs-FC after the music condition. FM patients reported MIA that was significantly correlated with rs-FC decrease between the angular gyrus, posterior cingulate cortex and precuneus, and rs-FC increase between amygdala and middle frontal gyrus. These areas are related to autobiographical and limbic processes, and auditory attention, suggesting MIA may arise as a consequence of top-down modulation, probably originated by distraction, relaxation, positive emotion, or a combination of these mechanisms.
... Synesthetic experiences involving one modality might favor a better performance in another modality through a stronger association between the modalities. A neurological study found an increased activation in the left inferior parietal cortex (IPC) of the auditory-visual synesthetes when compared to the non-synesthetes [47]. As IPC is responsible for multimodal integration and feature binding, the researchers believed that the auditory-visual synesthetes had a more enhanced sensory integration ability than the non-synesthetes. ...
How perceptual limits can be reduced has long been examined by psychologists. This study investigated whether visual cues, blindfolding, visual-auditory synesthetic experience, and musical training could facilitate a smaller frequency difference limen (FDL) in a gliding frequency discrimination test. Ninety university students, with no visual or auditory impairment, were recruited for this one-between (blindfolded/visual cues) and one-within (control/experimental session) designed study. Their FDLs were tested by an alternative forced-choice task (gliding upwards/gliding downwards/no change) and two questionnaires (Vividness of Mental Imagery Questionnaire and Projector–Associator Test) were used to assess their tendency to synesthesia. The participants provided with visual cues and with musical training showed a significantly smaller FDL; on the other hand, being blindfolded or having a synesthetic experience before could not significantly reduce the FDL. However, no pattern was found between the perception of the gliding upwards and gliding downwards frequencies. Overall, the current study suggests that the inter-sensory perception can be enhanced through the training and facilitation of visual–auditory interaction under the multiple resource model. Future studies are recommended in order to verify the effects of music practice on auditory percepts, and the different mechanisms between perceiving gliding upwards and downwards frequencies.
... AVS is an important investigated form of synesthesia. For instance, sounds (music or single tones) may elicit additional visual experiences, such as colors, forms, and textures Neufeld et al., 2012a). Page et al. (1982) observed that sudden unexpected sounds induced phosphenes (light flashes) in patients with optic neuropathy. ...
Based on a brief overview of the various aspects of schizophrenia reported by numerous studies, here we hypothesize that schizophrenia may originate (and in part be performed) from visual areas. In other words, it seems that a normal visual system or at least an evanescent visual perception may be an essential prerequisite for the development of schizophrenia as well as of various types of hallucinations. Our study focuses on auditory and visual hallucinations, as they are the most prominent features of schizophrenic hallucinations (and also the most studied types of hallucinations). Here, we evaluate the possible key role of the visual system in the development of schizophrenia.
... Synesthetic experience involving one modality might favor a better performance in another modality through a stronger association between modalities. A neurological study found an increased activation in the left inferior parietal cortex (IPC) of the auditory-visual synesthetes when compared to the non-synesthetes [43]. Since this area is responsible for multimodal integration and feature binding, the researchers believed that the auditory-visual synesthetes had an enhanced sensory integration ability than did the nonsynesthetes. ...
How perceptual limits can be overcome has long been examined by psychologists. This study investigated whether visual cues, blindfolding, visual-auditory synesthetic experience and music training could facilitate a smaller frequency difference limen (FDL) in a gliding frequency discrimination test. It was hoped that the auditory limits could be overcome through visual facilitation, visual deprivation, involuntary cross-modal sensory experience or music practice. Ninety university students, with no visual or auditory impairment, were recruited for this one-between (blindfold/visual cue) and one-within (control/experimental session) designed study. A MATLAB program was prepared to test their FDL by an alternative forced-choice task (gliding upwards/gliding downwards/no change) and two questionnaires (Vividness of Mental Imagery Questionnaire & Projector-Associator Test) were used to assess their tendency to synesthesia. Participants with music training showed a significantly smaller FDL; on the other hand, being blindfolded, being provided with visual cues or having synesthetic experience before could not significantly reduce the FDL. However, the result showed a trend of reduced FDLs through blindfolding. This indicated that visual deprivation might slightly expand the limits in auditory perception. Overall, current study suggests that the inter-sensory perception can be enhanced through training but not though reallocating cognitive resources to certain modalities. Future studies are recommended to verify the effects of music practice on other perceptual limits.
... Studies have shown that this region, especially the left inferior parietal cortex (IPC), plays a role in binding of cross-modal stimulations (e.g. audio-visual) [24], as represented by the Bouba-Kiki effect which maps vocal speech sounds onto visual shapes [25]. In addition, this region plays also shown to play a pivotal role in relating visual inputs to emotions [26]. ...
Sound is a sensory stimulant ubiquitously found throughout our environment. Humans have evolved a system that effectively and automatically converts sound sensory inputs into emotions. Although different emotional responses to sounds with different frequency characteristics are empirically recognized, there is a paucity of studies addressing different emotional responses to these sounds and the underlying neural mechanisms. In this study, we examined effects of pure tone (PT) and white noise (WN) inputs at ordinary loudness levels on emotional responses. We found that WN stimuli produced more aversive responses than PT stimuli. This difference was endorsed by larger late posterior positivity (LPP). In a source localization study, we found increased neural activity in the parietal lobe prior to LPP. These findings show that WN stimuli produce aversive perceptions compared with PT stimuli, at typical loudness levels. In addition, different emotional responses were processed in a similar manner as visual stimulations, as reflected by increased LPP activation. Various emotional effects of WN and PT stimuli, at ordinary loudness levels, could expand our understanding of adverse effects of noise as well as favorable effects associated with music.
... This is the case of musical inducers, which are a combination of pitch, tonality, rhythm, timbre, emotion, etc. Specific synesthesias for specific dimensions of music have been described (e.g. timbre-color association: Menouti et al., 2014), and, in other cases, the neural basis of color-hearing synesthesias has been investigated by the analysis of chords and pure tones (Neufeld et al., 2012) and a combination of pure tones and verbal stimuli (Nunn et al., 2002). This kind of auditory stimulation implies symbolic components, syllable stress, and rhythm, together with voice pitch and other elements which add complexity to the inducer. ...
Kinetic inducers and concurrents are infrequent. Nonetheless, the association between music (sound) and dance (movement) occurs naturally, and sometimes involuntarily. Curiously, dance-as a complex symbolic language of the body which we use to express our emotions-acts as an inducer of color synesthesias. The neuroscientific analysis of this complex language, which exhibits multiple components (auditory, kinetic, proprioceptive, symbolic, emotional) and of its relationship with synesthesia poses relevant questions about a) the nature of musical inducers, b) the mechanisms behind the acquisition of complex motor skills, c) procedural and vicarious learning, and d) the neurofunctional differences between voluntary and induced movement. In this paper I will revise the neuroscientific literature about dance and propose a structured analysis of dance-to-color synesthesia in order to understand the neurophysiological basis of the synesthetic brain from a new perspective.
... AVS is an important investigated form of synesthesia. For instance, sounds (music or single tones) may elicit additional visual experiences, such as colors, forms, and textures Neufeld et al., 2012a). Page et al. (1982) observed that sudden unexpected sounds induced phosphenes (light flashes) in patients with optic neuropathy. ...
Today, there is an increased interest in research on lysergic acid diethylamide (LSD) because it may offer new opportunities in psychotherapy under controlled settings. The more we know about how a drug works in the brain, the more opportunities there will be to exploit it in medicine. Here, based on our previously published papers and investigations, we suggest that LSD-induced visual hallucinations/phosphenes may be due to the transient enhancement of bioluminescent photons in the early retinotopic visual system in blind as well as healthy people.
... Brett et al., 2002). For this BOLD signal change (parameter estimate) extraction, we used a sphere with a 10 mm radius centered on the local maximum coordinates of the clusters of interest (see Table 1 for the cluster coordinates of the main effect of Emotion; for a similar procedure within auditory neuroimaging, see, e.g., Neufeld et al., 2012;Schulze et al., 2010). Subsequently, we conducted paired t-tests between stimulus categories on the mean signal change and retained the results that survived Bonferroni correction. ...
Music is often used to regulate emotions and mood. Typically, music conveys and induces emotions even when one does not attend to them. Studies on the neural substrates of musical emotions have, however, only examined brain activity when subjects have focused on the emotional content of the music. Here we address with functional magnetic resonance imaging (fMRI) the neural processing of happy, sad, and fearful music with a paradigm in which 56 subjects were instructed to either classify the emotions (explicit condition) or pay attention to the number of instruments playing (implicit condition) in 4-sec music clips. In the implicit vs. explicit condition, stimuli activated bilaterally the inferior parietal lobule, premotor cortex, caudate, and ventromedial frontal areas. The cortical dorsomedial prefrontal and occipital areas activated during explicit processing were those previously shown to be associated with the cognitive processing of music and emotion recognition and regulation. Moreover, happiness in music was associated with activity in the bilateral auditory cortex, left parahippocampal gyrus, and supplementary motor area, whereas the negative emotions of sadness and fear corresponded with activation of the left anterior cingulate and middle frontal gyrus and down-regulation of the orbitofrontal cortex. Our study demonstrates for the first time in healthy subjects the neural underpinnings of the implicit processing of brief musical emotions, particularly in frontoparietal, dorsolateral prefrontal, and striatal areas of the brain.
... However, Rouw and Scholte [14] found significant activation by synesthetic colors in the right, not the left, fusiform gyrus. Neufeld and col- leagues [15] measured significant activation related to synesthesia only on the left side, but this time in the parietal cortex. Published studies have, in fact, not provided yet any clear-cut picture of the neural bases of grapheme-color synesthesia [16, 17]. ...
Grapheme-color synesthesia, the idiosyncratic, arbitrary association of colors to letters or numbers, develops in childhood once reading is mastered. Because language processing is strongly left-lateralized in most individuals, we hypothesized that grapheme-color synesthesia could be left-lateralized as well. We used synesthetic versions of the Stroop test with colored letters and numbers presented either in the right or the left visual field of thirty-four synesthetes. Interference by synesthetic colors was stronger for stimuli in the right hemifield (first experiment, color naming task). Synesthetes were also faster in the right hemifield when naming the synesthetic color of graphemes (second experiment). Overall, the lateralization effect was 7 ms (the 95% confidence interval was [1.5 12] ms), a delay compatible with an additional callosal transfer for stimuli presented in the left hemifield. Though weak, this effect suggests that the association of synesthetic colors to graphemes may be preferentially processed in the left hemisphere. We speculate that this left-lateralization could be a landmark of synesthetic grapheme-color associations, if not found for color associations learnt by non-synesthete adults.
... A integração audiovisual está presente em diversas situações do cotidiano (Koelewijn, Bronkhorst e Theeuwes, 2010 (Caznok, 2008). Sinestesia se refere à percepção de determinados estímulos que resultam automaticamente em uma sensação adicional (concorrente) (Neufeld et al., 2012). Esta sensação adicional não pode ser suprimida voluntariamente. ...
Tanto o sistema auditivo, como o sistema visual, ambos localizados em regioes bem proximas no cerebro, codificam frequencias (sonoras e luminosas) que entram em nosso sistema sensorial, no caso a visao e a audicao, em informacoes para o cerebro, dando-nos condicoes de saber com o que estamos nos relacionando.
A substituicao sensorial e empregada para suprir a perda de uma modalidade sensorial, convertendo a informacao do sentido prejudicado por outro sentido nao acometido.
A integracao audiovisual e um tema pouco abordado na literatura musical. Nos estudos sobre musica e neurociencias este tem sido um assunto constante. Os aportes destes estudos trazem diversas hipoteses que se referem a sinestesia audiovisual, percepcao de objetos pela audicao musical, manifestacao da linguagem e percepcao de emocoes pela visualizacao da performance musical. Dessa forma, o proposito deste artigo e apresentar algumas desses aportes e discutir de que forma elas podem auxiliar os musicos, professores de musica e musicoterapeutas na sua pratica de trabalho e na formulacao de novas hipoteses de pesquisa.
... Over the decades, the term has inspired a long series of definitions and controversies (see Jewanski, Simner, Day, & Ward, 2011;Marks, 2011;Simner, 2012), suggesting that the word itself acts as something of a placeholder with which to characterize the process (or processes) that underlie surprising reports of associations between two apparently disjoint sensations, categories, or sensory dimensions. The term has been used to describe disparate cases, from those where individuals give consistent reports of seeing colors when hearing sounds (e.g., Howells, 1944;Mudge, 1920;Neufeld et al., 2012;Ward, Huckstep, & Tsakanikos, 2006;Zigler, 1930) or feeling shapes when tasting foods (Cytowic & Wood, 1982) to more singular cases of famous writers and composers who appear to have created exceptional musical combinations or metaphors (see Harrison, 2001, for a review; although see also Dann, 1998). It has also been used to explain the more general connections that the majority of people appear to make between "unlike stimuli" (Collier, 1996, p. 4)-say, high-pitched sounds and bright colors, speech sounds and shapes (Köhler, 1929), or the flavor of certain foods and the notion of sharpness (see Gal, Wheeler, & Shiv, 2007;Marks, 1982;Rader & Tellegen, 1987;Spence, Ngo, Percival, & Smith, 2013;Williams, 1976). ...
High pitch sounds are almost universally considered as brighter and ‘higher’ in space than low pitch ones. This tendency to map sensory dimensions in a seemingly arbitrary way across audition, vision and other modalities has lead many to consider that we are all ‘weakly synaesthetic’ (e.g., Eagleman, 2009; Cohen, in press). Here we defend ‘the separatist view’ and argue that these cases are likely to form distinct kinds of phenomena despite their superficial similarities with synaesthesia. Ultimately, we provide a general definition of crossmodal correspondences as acquired, malleable, relative, and transitive pairings between sensory dimensions and integrate them as a kind of functional multisensory interaction.
... Grapheme-color synesthesia (GCS), in which achromatic letters, words or numbers are perceived in specific colors, has been extensively investigated and is believed to be one of the most common types (Simner et al., 2006). In auditory-visual synesthesia, sounds (e.g., music or single tones) can induce additional visual experiences, such as colors, forms, and textures (Ward et al., 2006;Neufeld et al., 2012a). Usually synesthetes have multiple types of synesthesia, suggesting a more global perceptual alteration underlying synesthesia rather than a specific one that only affects specific stimuli in two sensory modalities. ...
Synesthesia entails a special kind of sensory perception, where stimulation in one sensory modality leads to an internally generated perceptual experience of another, not stimulated sensory modality. This phenomenon can be viewed as an abnormal multisensory integration process as here the synesthetic percept is aberrantly fused with the stimulated modality. Indeed, recent synesthesia research has focused on multimodal processing even outside of the specific synesthesia-inducing context and has revealed changed multimodal integration, thus suggesting perceptual alterations at a global level. Here, we focused on audio–visual processing in synesthesia using a semantic classification task in combination with visually or auditory–visually presented animated and in animated objects in an audio–visual congruent and incongruent manner. Fourteen subjects with auditory-visual and/or grapheme-color synesthesia and 14 control subjects participated in the experiment. During presentation of the stimuli, event-related potentials were recorded from 32 electrodes. The analysis of reaction times and error rates revealed no group differences with best performance for audio-visually congruent stimulation indicating the well-known multimodal facilitation effect. We found enhanced amplitude of the N1 component over occipital electrode sites for synesthetes compared to controls. The differences occurred irrespective of the experimental condition and therefore suggest a global influence on early sensory processing in synesthetes.
... Over the decades, the term has inspired a long series of definitions and controversies (see Jewanski, Simner, Day, & Ward, 2011;Marks, 2011;Simner, 2012), suggesting that the word itself acts as something of a placeholder with which to characterize the process (or processes) that underlie surprising reports of associations between two apparently disjoint sensations, categories, or sensory dimensions. The term has been used to describe disparate cases, from those where individuals give consistent reports of seeing colors when hearing sounds (e.g., Howells, 1944;Mudge, 1920;Neufeld et al., 2012;Ward, Huckstep, & Tsakanikos, 2006;Zigler, 1930) or feeling shapes when tasting foods (Cytowic & Wood, 1982) to more singular cases of famous writers and composers who appear to have created exceptional musical combinations or metaphors (see Harrison, 2001, for a review; although see also Dann, 1998). It has also been used to explain the more general connections that the majority of people appear to make between "unlike stimuli" (Collier, 1996, p. 4)-say, high-pitched sounds and bright colors, speech sounds and shapes (Köhler, 1929), or the flavor of certain foods and the notion of sharpness (see Gal, Wheeler, & Shiv, 2007;Marks, 1982;Rader & Tellegen, 1987;Spence, Ngo, Percival, & Smith, 2013;Williams, 1976). ...
A little over a decade ago, Martino and Marks (Current Directions in Psychological Science 10:61-65, 2001) put forward the influential claim that cases of intuitive matchings between stimuli in different sensory modalities should be considered as a weak form of synesthesia. Over the intervening years, many other researchers have agreed-at the very least, implicitly-with this position (e.g., Bien, ten Oever, Goebel, & Sack NeuroImage 59:663-672, 2012; Eagleman Cortex 45:1266-1277, 2009; Esterman, Verstynen, Ivry, & Robertson Journal of Cognitive Neuroscience 18:1570-1576, 2006; Ludwig, Adachi, & Matzuzawa Proceedings of the National Academy of Sciences of the United States of America 108:20661-20665, 2011; Mulvenna & Walsh Trends in Cognitive Sciences 10:350-352, 2006; Sagiv & Ward 2006; Zellner, McGarry, Mattern-McClory, & Abreu Chemical Senses 33:211-222:2008). Here, though, we defend the separatist view, arguing that these cases are likely to form distinct kinds of phenomena despite their superficial similarities. We believe that crossmodal correspondences should be studied in their own right and not assimilated, either in terms of the name used or in terms of the explanation given, to synesthesia. To conflate these two phenomena is both inappropriate and potentially misleading. Below, we critically evaluate the evidence concerning the descriptive and constitutive features of crossmodal correspondences and synesthesia and highlight how they differ. Ultimately, we wish to provide a general definition of crossmodal correspondences as acquired, malleable, relative, and transitive pairings between sensory dimensions and to provide a framework in which to integrate the nonsystematic cataloguing of new cases of crossmodal correspondences, a tendency that has increased in recent years.
... Ces prédictions ont été testées principalement par les méthodes d'imagerie par résonance magnétique, structurale et fonctionnelle (IRMf), avec des résultats contrastés. Les études les plus populaires sont celles qui ont effectivement montré l'activation des centres de la couleur chez des synesthètes [20][21][22], mais des études similaires [12,[23][24][25] n'ont pas reproduit ces résultats basés sur des inférences statistiques discutables [12]. Un même manque de consensus concerne la présence [22] ou l'absence [12,24,26] de connexions surnuméraires pouvant expliquer les couleurs synesthésiques. ...
Synesthetes, a small fraction of the population, experience systematic, additional associations. For example, they may arbitrarily associate a specific color to each letter or number. Synesthesia has offered for the last ten years to cognitive science a unique opportunity to study the neural bases of subjective experience, drawing on individual differences just like in neuropsychology, but with healthy people. Here we review the current knowledge and propose a new theory, the "palimpsest hypothesis", a variant of the recycling hypothesis for reading. The neural development of written language expertise (a recent cultural invention acquired without any genetic modification) requires indeed the recycling of brain regions predisposed to expertise acquisition into reading regions. The palimpsest hypothesis supposes that for synesthetes recycling involves neuronal networks that were already specialized for color perception. Synesthetic colors would be the remains of this former expertise.
© 2012 médecine/sciences – Inserm / SRMS.
... Involvement of the inferior temporal cortex also occurs (Paulesu et al., 1995;Sperling et al., 2006). Different studies have also found activation of parietal cortex in synesthesia (Neufeld et al., 2011;van Leeuwen, Petersson, & Hagoort, 2010;Weiss, Zilles, & Fink, 2005). Rouw and Scholte (2007) found increased structural connectivity in the left superior parietal cortex with diffusion tensor imaging (DTI), and Weiss and Fink (2009) found morphological changes in the intraparietal sulcus with voxel-based morphometry (VBM). ...
Despite some principal similarities, there is no systematic comparison between the different types of synesthesia (genuine, acquired and drug-induced). This comprehensive review compares the three principal types of synesthesia and focuses on their phenomenological features and their relation to different etiological models. Implications of this comparison for the validity of the different etiological models are discussed. Comparison of the three forms of synesthesia show many more differences than similarities. This is in contrast to their representation in the literature, where they are discussed in many respects as being virtually similar. Noteworthy is the much broader spectrum and intensity with the typical drug-induced synesthesias compared to genuine and acquired synesthesias. A major implication of the phenomenological comparison in regard to the etiological models is that genuine and acquired synesthesias point to morphological substrates, while drug-induced synesthesia appears to be based on functional changes of brain activity.
Synaesthesia is a condition where people experience unusual sensory or cognitive sensations in response to apparently unrelated stimuli. This paper presents two experiments which aimed to examine whether Virtual Reality (VR) technology can be used to recreate the synaesthetic experience. There is a lack of research in this area, with most studies focussing primarily on synaesthetic colors. Experiment 1 aimed to build on previous research by using not only a traditional color-picker but also VR to capture a more nuanced picture of synaesthetic perception. A multiple case study design was used to examine the experiences of six participants in detail. Data gathering took place via Zoom. During the initial data-gathering session, participants used a color-picker to provide grapheme-color associations. After this session, some of the participants’ synaesthetic experiences were recreated using a VR-by-proxy approach. Results indicated that VR is capable of capturing elements of synaesthetic perception that other methods have been unable to, such as texture, small degrees of movement, and 3D structure. Experiment 2 expanded upon these findings by moving beyond the VR-by-proxy approach and asking three participants to recreate their own audiovisual synaesthetic associations in the VR environment. Inductive Thematic Analysis was used to analyze the results of this experiment. The potential of expanding this technique to other forms of perceptual diversity is discussed.
Non-arbitrary mapping between the sound of a word and its meaning, termed sound symbolism, is commonly studied through crossmodal correspondences between sounds and visual shapes, e.g., auditory pseudowords, like 'mohloh' and 'kehteh', are matched to rounded and pointed visual shapes, respectively. Here, we used functional magnetic resonance imaging (fMRI) during a crossmodal matching task to investigate the hypotheses that sound symbolism (1) involves language processing; (2) depends on multisensory integration; (3) reflects embodiment of speech in hand movements. These hypotheses lead to corresponding neuroanatomical predictions of crossmodal congruency effects in (1) the language network; (2) areas mediating multisensory processing, including visual and auditory cortex; (3) regions responsible for sensorimotor control of the hand and mouth. Right-handed participants (n = 22) encountered audiovisual stimuli comprising a simultaneously presented visual shape (rounded or pointed) and an auditory pseudoword ('mohloh' or 'kehteh') and indicated via a right-hand keypress whether the stimuli matched or not. Reaction times were faster for congruent than incongruent stimuli. Univariate analysis showed that activity was greater for the congruent compared to the incongruent condition in the left primary and association auditory cortex, and left anterior fusiform/parahippocampal gyri. Multivoxel pattern analysis revealed higher classification accuracy for the audiovisual stimuli when congruent than when incongruent, in the pars opercularis of the left inferior frontal (Broca's area), the left supramarginal, and the right mid-occipital gyri. These findings, considered in relation to the neuroanatomical predictions, support the first two hypotheses and suggest that sound symbolism involves both language processing and multisensory integration.
Creative metaphor has been of central interest to the cognitive linguistic research community in recent years. However, little is known about what propels people to use metaphor in a creative way. In this Element, the authors identify and explore some of the clues that synaesthesia may provide to help us better understand the factors that drive creativity, with a particular focus on creative metaphor. They identify the factors that seem to trigger the production of creative metaphor in synaesthetes, and explore what this can tell us about creativity in the population more generally. Their findings provide insights into the nature of creativity as it relates to metaphor, emotion and embodied experience. They argue that the production of creative metaphor arises from strong affective reactions to sensory and emotional stimuli and that there is an embodied symbiotic relationship between sensory experiences, embodiment, emotion, hyperbole, empathy, metaphor and creativity.
Résumé Ces dernières années, l’étude de la synesthésie a pris de l’ampleur au sein de la communauté scientifique. Cet article passe en revue certains aspects essentiels de la synesthésie. Après une description de ce phénomène, nous nous intéressons à son objectivation et à ses origines développementales. Ensuite, grâce aux données issues de divers articles, nous tentons de déterminer si l’acquisition d’associations synesthésiques s’arrête un jour et si des personnes qui ne sont pas synesthètes peuvent apprendre à le devenir. Nous discutons aussi des bénéfices cognitifs éventuels de la synesthésie et de ce que peut apporter l’étude de ce phénomène à la compréhension plus générale de la cognition.
Synaesthesia is a multimodal phenomenon in which the activation of one sensory modality leads to an involuntary additional experience in another sensory modality. To date, normal multisensory processing has hardly been investigated in synaesthetes. In the present study we examine processes of audiovisual separation in synaesthesia by using a simultaneity judgement task. Subjects were asked to indicate whether an acoustic and a visual stimulus occurred simultaneously or not. Stimulus onset asynchronies (SOA) as well as the temporal order of the stimuli were systematically varied. Our results demonstrate that synaesthetes are better in separating auditory and visual events than control subjects, but only when vision leads.
Cambridge Core - Cognition - Metaphors in the Mind - by Jeannette Littlemore
Music and color synesthesia is a stimulus in the acoustic modality will consistently and automatically trigger concurrent percepts in the visual modality. In this paper, we study the music and color synesthesia with visual saliency information in the emotional level by the eye tracking technique. We organize an experiment, letting participants look at four different color combinations on the screen when listen to the music with eight emotions. And the eye tracker is adopted to catch the eye movement of participants during the experiments. From the metrics of the total fixation time and the scan paths, we obtain the relations between music and colors in the emotional level by this objective way. Besides, a questionnaire about the music and color synaesthesia is provided for participants to fill in. So that we can compare the objective and subjective cognition styles.
La synesthésie est un phénomène fascinant qui offre une opportunité privilégiée d'étudier chez les sujets sains les bases neurales de l'expérience subjective. Les synesthètes graphème-couleur (1 à 5 % de la population – qui ignorent le plus souvent l'être) associent arbitrairement et systématiquement une couleur spécifique à chaque lettre ou chiffre. Ce travail de thèse se focalise sur ces synesthésies et explore l'implication, dans l'expérience subjective de couleurs synesthésiques, des régions corticales qui sont actives lors de la perception des couleurs ‘réelles'. Dans une étude préalable réalisé par l'équipe d'accueil utilisant l'Imagerie par Résonance Magnétique (IRM) fonctionnelle, une telle implication des ‘aires de la couleur' n'a pas été observée (Hupé et al. 2012). Une analyse statistique ‘classique' (univariée) du traitement des données mesurées était utilisée.Cette thèse vise à déterminer si les couleurs synesthésiques reposent sur les réseaux neuronaux des couleurs réelles en utilisant une technique d'analyse statistique multivariée (MultiVoxel Pattern Analysis – MVPA). A la différence de l'analyse univariée elle se base sur des ensembles de voxels (les pixels en 3D qui composent les images acquises) et prend en compte leurs motifs d'activation correspondant spécifiquement à l'encodage d'une information donnée par le cerveau. Cet encodage est réalisé au niveau neuronal et l'IRMf en donne une quantification non-invasive et indirecte au travers des répercutions hémodynamiques induites par l'activation neuronale. Cette modélisation multivariée des données fait des MVPA une approche particulièrement adaptée à la mesure d'informations encodées finement de manière distribuée. Le but de ce travail est d'explorer son efficacité pour l'étude des synesthésies graphème-couleur où l'analyse classique n'a pas fourni de résultats robustes. En pratique, elle nécessite cependant l'utilisation de protocoles spécifiques, la maîtrise des nombreux paramètres qui influent radicalement sur son fonctionnement et l'utilisation conjointe de l'analyse univariée. Dans une première étape de cette thèse, nous avons évalué différents aspects méthodologiques qu'il est important de maîtriser afin d'obtenir des résultats robustes et une analyse fiable.Ensuite, nous avons comparé le traitement des couleurs réelles et synesthésiques chez deux groupes de 20 synesthètes et non synesthètes. Nous avons trouvé que le traitement des couleurs synesthésiques ne repose pas sur les réseaux neuronaux de traitement de la couleur réelle. Cela peut signifier que les bases neuronales des couleurs synesthésiques ne se situent ni dans les aires visuelles rétinotopiques ni dans les aires de l'expertise visuelle (les aires de la ‘voie ventrale'). Cela peut également signifier que, bien que ces aires soient impliquées, ce ne sont pas les réseaux neuronaux de traitement des couleurs réelles qui sont activés lors de la perception de couleurs synesthésique. D'un point de vue méthodologique, il est possible que les signaux mesurés par l'IRMf ne permettent pas d'observer ce codage partagé. Ces résultats posent donc la question des limites de l'interprétation des signaux mesurés en IRMf très indirectement liés à l'activité neuronale. L'identification des réseaux neuronaux impliqués dans l'expérience subjective des couleurs synesthésiques reste donc une problématique ouverte.
These last few years, the study of synaesthesia gained in importance in the scientific community. In this article, we present some essential aspects of synaesthesia. After describing this phenomenon, we discuss how to measure it in an objective way and what are its developmental origins. Then, based on data from various articles, we try to determine if the acquisition of synaesthetic associations stops one day and if non-synaesthete people can learn to become synaesthetes. We also discuss the possible cognitive benefits of synaesthesia and how the study of this phenomenon contributes to the more general comprehension of cognition.
Operatic performance has a long and well-established history as a large-scale performance encompassing elements of music, theatre and design. Staging of such productions is an intricate process involving many parties both on the stage and behind the scenes. This paper discusses multimodal and multimedia technologies and techniques that can assist this practice. We look particularly at the conductor, as the controller of temporal progression, leading the various components as a cohesive unit. For this reason, a particular focus is upon the development of methods to communicate cues and information for lighting, visual stimuli and haptic feedback. Previous work that has informed the design of this system is also discussed. The paper concludes with the project’s current status and impact.
Synesthesia is a fascinating phenomenon that offers the opportunity to study the neural bases of subjective experiences in healthy subjects. Grapheme-color synesthetes (1 to 5 % of the population – who do not know it most of the time) arbitrarily and systematically associate a specific color to letters or digits. This PhD thesis work focuses on this type of synesthesia and explores whether common neural networks are involved both in “real” color perception and synesthetic color experience. In a previous study from the host team using functional Magnetic Resonance Imaging (MRI), no implication of “color areas” where found (Hupé et al., 2012). A standard (univariate) statistical analysis of the data processing was used. This PhD thesis aims at determining if synesthetic colors involve real color neural networks with the use of a multivariate statistical technique (Multivoxel Pattern Analysis – MVPA). Unlike univariate analysis it uses sets of voxels (the pixels in 3D forming the images) and take into account their patterns of activation linked to the encoding of specific information in the brain. This encoding is performed at the neuronal level and fMRI indirectly and non-invasively quantifies it through hemodynamic variations induced by the neuronal activity. MVPA is a particularly adapted approach to measure fine grained and distributed information encoding. The goal of the thesis is to explore its efficiency for the study of grapheme-color synesthesia for which standard analyses failed. In practice, it requires the use of specific protocols, mastering numerous parameters influencing the results and the joint use of univariate analysis. In the first step of this thesis, we evaluated different methodological aspects to optimize the processing chain in order to obtain robust and reliable results. Then, we compared the neural processing of real colors and synesthetic colors in 2 groups of synesthetes (n=20) and non synesthetes (n=20). We found that synesthetic colors processing does not share common neural networks with real color processing. This suggests that the neural bases of synesthetic colors are not localized in the retinotopic visual areas or in the visual expertise areas (the “ventral pathway” areas). This may also suggest that, although those areas are involved, different neural networks are implicated in real color and synesthetic color perception. These results raise the question of the limits of the interpretation of the signal measured by fMRI, indirectly linked to the neuronal activity. The identification of the neural networks involved in the subjective experience of synesthetic colors remains an open issue.
INTRODUCTION. Synesthesia is a neural phenomenon in which stimulation in one sensory or cognitive stream leads to associated experiences in a second, unstimulated stream. These activations occur involuntarily, automatically and consistently over time. AIM. To estimate the relative frequency of the different modalities of the phenomenon in a Spanish sample. SUBJECTS AND METHODS. Study performed in educational (55.04%), labor (20.54%) and digital contexts (24.4%) using the Synesthesia Questionnaire created by Artecitta Foundation. RESULTS. The analysis of the responses given by 803 participants suggests that 13.95% of the sample experience any synesthesia. The analysis of the relative frequencies shows that the most frequent modality is spatial sequence synesthesia (44.6%). 33.9% see colors when listening to sounds and/or music, 25.9% associate colors to temporal concepts, 20.5% assign gender and personality to letters and numbers, 10.7% experience grapheme-color synesthesia and 5.4% feel a specific flavor when hearing words. CONCLUSIONS. These data suggest that the presence of synesthesia in the Spanish sample under study is high, and that the investigation of the phenomenon and its different modalities needs to be approached on the basis of the current knowledge about its phenomenological variability and its genetic and neurophysiologic characteristics. Likewise, the results are useful to adjust the questionnaire items and increase their discriminative power.
In synesthesia, experiences in one domain evoke additional experiences in another, as when musical notes or letters of the alphabet evoke colors. Both the domains and their pairings are diverse. Indeed, Day's (2013) recently tabulated 60 types of synesthesia, each referring to a different combination of inducing and induced domains. The domains conjoined through synesthesia may belong to different sense modalities, as in music-color synesthesia, but may also belong to the same modality: In grapheme-color synesthesia, seeing printed letters or numbers evokes color experiences.
In music-color and grapheme-color synesthesia, the inducing stimuli are perceptual, reflecting culture-specific categories (notes of the Western musical scale, letters of the alphabet) learned by synesthetes and non-synesthetes alike. Synesthesia may be triggered not only by sounds, tastes, smells, and pains, but also by more complex signals: words(e.g., Simner, 2007), emotional states (e.g., Ward, 2004), and even personalities (e.g., Novich et al., 2011). Analogously, the domains of synesthetic responses too can range widely. The composer Rimsky-Korsakoff “saw” the key of D-major as golden (Myers, 1914), while a grapheme-personification synesthete reported, “Ts are generally crabbed, ungenerous creatures” (Calkins, 1893; p. 454). Other phenomena, however, such as cross-modally evoked images or memories, are not typically considered examples of synesthesia.
In this article, we briefly describe half a dozen illustrative cases that border on traditional forms of synesthesia: cross-modal correspondence, cross-modal imagery, sensory (cross-modal) autobiographical memory, empathic perception, hallucination, and the Doppler illusion. Do any or all of the six constitute forms of synesthesia? The answer depends, we suggest, on the framework for characterizing synesthesia. Consequently, after describing the six phenomena, we sketch three frameworks that differ in how they characterize these phenomena relative to prototypical forms of synesthesia. Several investigators, taking different perspectives and coming to different conclusions, have already considered possible relations to synesthesia in three of the six: cross-modal correspondence (Martino and Marks, 2001; Deroy and Spence, 2013); cross-modal imagery (Craver-Lemley and Reeves, 2013; Spence and Deroy, 2013); and empathic perception (Fitzgibbon et al., 2010; Rothen and Meier, 2013).
Absolute pitch (AP) and synesthesia are two uncommon cognitive traits that reflect increased neuronal connectivity and have been anecdotally reported to occur together in an individual. Here we systematically evaluate the occurrence of synesthesia in a population of 768 subjects with documented AP. Out of these 768 subjects, 151 (20.1%) reported synesthesia, most commonly with color. These self-reports of synesthesia were validated in a subset of 21 study subjects, using an established methodology. We further carried out combined linkage analysis of 53 multiplex families with AP and 36 multiplex families with synesthesia. We observed a peak NPL LOD = 4.68 on chromosome 6q, as well as evidence of linkage on chromosome 2, using a dominant model. These data establish the close phenotypic and genetic relationship between AP and synesthesia. The chromosome 6 linkage region contains 73 genes; several leading candidate genes involved in neurodevelopment were investigated by exon resequencing. However, further studies will be required to definitively establish the identity of the causative gene(s) in the region.
Grapheme-color synesthesia is a condition in which letters are perceived with an additional color dimension. To identify brain regions involved in this type of synesthesia and to analyze functional connectivity of these areas, 18 grapheme-color synesthetes and 18 matched controls were stimulated with letters and pseudo-letters presented in black and color in an event-related fMRI experiment. Based on the activation-differences between synesthetes and non-synesthetic controls regions of interest were defined. In a second analysis step functional connectivity was calculated using beta series correlation analysis for these seed regions. First we identified one seed region in the left inferior parietal (IPL) cortex (BA7) showing activation differences between grapheme-color synesthetes and controls. Furthermore, we found activation differences in brain areas involved in processing of letters and pseudo-letters, in particular the right IPL cortex (BA7), but also two more clusters in the right hemispheric BA 18 and BA 40. Functional connectivity analysis revealed an increased connectivity between the left IPL seed region and primary/secondary visual areas (BA 18) in synesthetes. Also the right BA 7 showed a stronger connectivity with primary/secondary visual areas (BA 18) in grapheme-color synesthetes. The results of this study support the idea that the parietal lobe plays an important role in synesthetic experience. The data suggest furthermore that the information flow in grapheme-color synesthetes was already modulated at the level of the primary visual cortex which is different than previously thought. Therefore, the current models of grapheme-color synesthesia have to be refined as the unusual communication flow in synesthetes is not restricted to V4, fusiform cortex and the parietal lobe but rather involves a more extended network.
It has been suggested that synaesthesia is the result of a hyper-sensitive multimodal binding-mechanism. To address the question whether multi-modal integration is altered in synaesthetes in general, grapheme-colour and auditory-visual synaesthetes were studied using the double-flash illusion. This illusion is induced by a single light flash presented together with multiple beep sounds, which is then perceived as multiple flashes. By varying the separation of auditory and visual stimuli, the hypothesis of a widened temporal window of audio-visual integration in synaesthetes was tested. As hypothesised, the results show differences between synaesthetes and controls concerning multisensory integration, but surprisingly other than expected synaesthetes perceive a reduced number of illusions and have a smaller time-window of audio-visual integration compared to controls. This indicates that they do not have a hyper-sensitive binding mechanism. On the contrary, synaesthetes seem to integrate even less than controls between vision and audition.
We investigated grapheme--colour synaesthesia and found that: (1) The induced colours led to perceptual grouping and pop-out, (2) a grapheme rendered invisible through `crowding' or lateral masking induced synaesthetic colours --- a form of blindsight --- and (3) peripherally presented graphemes did not induce colours even when they were clearly visible. Taken collectively, these and other experiments prove conclusively that synaesthesia is a genuine perceptual phenomenon, not an effect based on memory associations from childhood or on vague metaphorical speech. We identify different subtypes of number--colour synaesthesia and propose that they are caused by hyperconnectivity between colour and number areas at different stages in processing; lower synaesthetes may have cross-wiring (or cross-activation) within the fusiform gyrus, whereas higher synaesthetes may have cross-activation in the angular gyrus. This hyperconnectivity might be caused by a genetic mutation that causes defective pruning of connections between brain maps. The mutation may further be expressed selectively (due to transcription factors) in the fusiform or angular gyri, and this may explain the existence of different forms of synaesthesia. If expressed very diffusely, there may be extensive cross-wiring between brain regions that represent abstract concepts, which would explain the link between creativity, metaphor and synaesthesia (and the higher incidence of synaesthesia among artists and poets). Also, hyperconnectivity between the sensory cortex and amygdala would explain the heightened aversion synaesthetes experience when seeing numbers printed in the `wrong' colour. Lastly, kindling (induced hyperconnectivity in the temporal lobes of temporal lobe epilepsy [TLE] patients) may explain the purp...
An automated coordinate-based system to retrieve brain labels from the 1988 Talairach Atlas, called the Talairach Daemon (TD), was previously introduced [Lancaster et al., 1997]. In the present study, the TD system and its 3-D database of labels for the 1988 Talairach atlas were tested for labeling of functional activation foci. TD system labels were compared with author-designated labels of activation coordinates from over 250 published functional brain-mapping studies and with manual atlas-derived labels from an expert group using a subset of these activation coordinates. Automated labeling by the TD system compared well with authors' labels, with a 70% or greater label match averaged over all locations. Author-label matching improved to greater than 90% within a search range of +/-5 mm for most sites. An adaptive grey matter (GM) range-search utility was evaluated using individual activations from the M1 mouth region (30 subjects, 52 sites). It provided an 87% label match to Brodmann area labels (BA 4 & BA 6) within a search range of +/-5 mm. Using the adaptive GM range search, the TD system's overall match with authors' labels (90%) was better than that of the expert group (80%). When used in concert with authors' deeper knowledge of an experiment, the TD system provides consistent and comprehensive labels for brain activation foci. Additional suggested applications of the TD system include interactive labeling, anatomical grouping of activation foci, lesion-deficit analysis, and neuroanatomy education. (C) 2000 Wiley-Liss, Inc.
Music researchers have regularly employed simple meas- ures, such as years of private lessons taken, as indicators of participants' musical sophistication levels. The aim of this study was to test 29 self-administrable indicators of musical sophistication in order to determine their ability to explain the variance in experts' subjective ratings—used as the criterion variable. Furthermore, a model was devel- oped and tested to classify participants as being more or less musically sophisticated. The author developed a 36-item questionnaire and admin- istered it to a sample of 633 adult volunteers who belonged to various music-related groups (e.g., music courses, per- forming ensembles). Group leaders provided sophistica- tion ratings of the respondents. Bivariate correlations re- vealed that the indicator most strongly associated with the experts' ratings (r = .54) asked respondents to select one of six self-descriptive titles (nonmusician through profes- sional); the popular indicator, years of private lessons, ranked tenth (r = .40). The results of the logistic regres- sion analysis indicated an overall significant model (chi- square < .001) with 7 of the 29 indicators significant at the .05 level. The model is able to accurately classify respon- dents as more or less musically sophisticated approxi- mately 82% of the time.
Investigations of the functional organization of human auditory cortex typically examine responses to different sound categories. An alternative approach is to characterize sounds with respect to their amount of variation in the time and frequency domains (i.e., spectral and temporal complexity). Although the vast majority of published studies examine contrasts between discrete sound categories, an alternative complexity-based taxonomy can be evaluated through meta-analysis. In a quantitative meta-analysis of 58 auditory neuroimaging studies, we examined the evidence supporting current models of functional specialization for auditory processing using grouping criteria based on either categories or spectro-temporal complexity. Consistent with current models, analyses based on typical sound categories revealed hierarchical auditory organization and left-lateralized responses to speech sounds, with high speech sensitivity in the left anterior superior temporal cortex. Classification of contrasts based on spectro-temporal complexity, on the other hand, revealed a striking within-hemisphere dissociation in which caudo-lateral temporal regions in auditory cortex showed greater sensitivity to spectral changes, while anterior superior temporal cortical areas were more sensitive to temporal variation, consistent with recent findings in animal models. The meta-analysis thus suggests that spectro-temporal acoustic complexity represents a useful alternative taxonomy to investigate the functional organization of human auditory cortex.
Synesthesia provides an elegant model to investigate neural mechanisms underlying individual differences in subjective experience in humans. In grapheme-color synesthesia, written letters induce color sensations, accompanied by activation of color area V4. Competing hypotheses suggest that enhanced V4 activity during synesthesia is either induced by direct bottom-up cross-activation from grapheme processing areas within the fusiform gyrus, or indirectly via higher-order parietal areas. Synesthetes differ in the way synesthetic color is perceived: "projector" synesthetes experience color externally colocalized with a presented grapheme, whereas "associators" report an internally evoked association. Using dynamic causal modeling for fMRI, we show that V4 cross-activation during synesthesia was induced via a bottom-up pathway (within fusiform gyrus) in projector synesthetes, but via a top-down pathway (via parietal lobe) in associators. These findings show how altered coupling within the same network of active regions leads to differences in subjective experience. Our findings reconcile the two most influential cross-activation accounts of synesthesia.
Background:
In synaesthesia, sensations in a particular modality cause additional experiences in a second, unstimulated modality (e.g., letters elicit colour). Understanding how synaesthesia is mediated in the brain can help to understand normal processes of perceptual awareness and multisensory integration. In several neuroimaging studies, enhanced brain activity for grapheme-colour synaesthesia has been found in ventral-occipital areas that are also involved in real colour processing. Our question was whether the neural correlates of synaesthetically induced colour and real colour experience are truly shared.
Methodology/principal findings:
First, in a free viewing functional magnetic resonance imaging (fMRI) experiment, we located main effects of synaesthesia in left superior parietal lobule and in colour related areas. In the left superior parietal lobe, individual differences between synaesthetes (projector-associator distinction) also influenced brain activity, confirming the importance of the left superior parietal lobe for synaesthesia. Next, we applied a repetition suppression paradigm in fMRI, in which a decrease in the BOLD (blood-oxygenated-level-dependent) response is generally observed for repeated stimuli. We hypothesized that synaesthetically induced colours would lead to a reduction in BOLD response for subsequently presented real colours, if the neural correlates were overlapping. We did find BOLD suppression effects induced by synaesthesia, but not within the colour areas.
Conclusions/significance:
Because synaesthetically induced colours were not able to suppress BOLD effects for real colour, we conclude that the neural correlates of synaesthetic colour experience and real colour experience are not fully shared. We propose that synaesthetic colour experiences are mediated by higher-order visual pathways that lie beyond the scope of classical, ventral-occipital visual areas. Feedback from these areas, in which the left parietal cortex is likely to play an important role, may induce V4 activation and the percept of synaesthetic colour.
Little is known about how the properties of our private mental world relate to the physical and functional properties of our brain. Studying synesthesia, where a particular experience evokes a separate additional sensory experience, offers the unique opportunity to study phenomenological experiences as a stable trait in healthy subjects. A common form of synesthesia is grapheme-color synesthesia, where a particular letter or number evokes a particular color experience. We studied the neural basis of qualitative different properties of the synesthetic experience by using individual differences in grapheme-color synesthesia. Specifically, the synesthetic color can be experienced "in the mind" (associator synesthetes) or "in the outside world" (projector synesthetes). Gray matter structure and functioning (imaged using voxel-based morphometry and functional magnetic resonance imaging, respectively) were examined in grapheme-color synesthetes (N = 42, 16 projectors and 26 associators) and nonsynesthetes. Results indicated partly shared mechanisms for all grapheme-color synesthetes, particularly in posterior superior parietal lobe, which is involved in the integration of sensory information. In addition, the nature of synesthetic experience was found to be mediated by distinct neural mechanisms. The outside-world experience is related to brain areas involved in perceiving and acting in the outside world (visual cortex, auditory cortex, motor cortex) as well as frontal brain areas. In contrast, the in-the-mind experience is related to the hippocampus and parahippocampal gyrus, known for their role in memory. Thus, the different subjective experiences are related to distinct neural mechanisms. Moreover, the properties of subjective experiences are in accordance with functional properties of the mediating brain mechanisms.
In synaesthesia, stimulation of a sensory modality triggers abnormal additional perceptions. Voxel-based morphometry (VBM) was used in 18 grapheme-colour synaesthetes to investigate the neuro-anatomical basis of their abnormal perceptions. More specifically, we tested the hypothesis that in synaesthesia altered connectivity in temporo-occipital and parietal areas may be associated with grey matter (GM) changes. The data reveal increased GM volumes in fusiform and intraparietal cortices. These findings are consistent with the two-stage model of grapheme-colour synaesthesia implying cross-activation at the level of the fusiform gyrus (FG) and 'hyperbinding' at the level of the parietal cortex. The observed structural differences in grapheme-colour synaesthetes with abnormal additional perceptions may also shed some light on the neural bases of abnormal perceptions in neurological and psychiatric disorders.
In auditory–visual synesthesia, sounds automatically elicit conscious and reliable visual experiences. It is presently unknown whether this reflects early or late processes in the brain. It is also unknown whether adult audiovisual synesthesia resembles auditory-induced visual illusions that can sometimes occur in the general population or whether it resembles the electrophysiological deflection over occipital sites that has been noted in infancy and has been likened to synesthesia. Electrical brain activity was recorded from adult synesthetes and control participants who were played brief tones and required to monitor for an infrequent auditory target. The synesthetes were instructed to attend either to the auditory or to the visual (i.e., synesthetic) dimension of the tone, whereas the controls attended to the auditory dimension alone. There were clear differences between synesthetes and controls that emerged early (100 msec after tone onset). These differences tended to lie in deflections of the auditory-evoked potential (e.g., the auditory N1, P2, and N2) rather than the presence of an additional posterior deflection. The differences occurred irrespective of what the synesthetes attended to (although attention had a late effect). The results suggest that differences between synesthetes and others occur early in time, and that synesthesia is qualitatively different from similar effects found in infants and certain auditory-induced visual illusions in adults. In addition, we report two novel cases of synesthesia in which colors elicit sounds, and vice versa.
Reviews colored-hearing synesthesia, in which sounds induce visual images (photisms). Colored hearing manifests correlations between dimensions of auditory and visual experience. Two general findings are that (a) the brightness of photisms varies with the brightness (density) of the inducing sounds and (b) the size of photisms varies with the size (volume) of the inducing sounds. In colored hearing produced by speech sounds, the induced hues and brightnesses can be related to the formant structures of the vowels. Synesthetes align dimensions on different modalities in ways that are qualitatively similar to the ways that nonsynesthetes align them (e.g., in phonetic symbolism). Synesthesia appears to be a cross-modal manifestation of connotative meaning in a pure sensory form; its inflexibility (compared to language) makes synesthesia less significant in adulthood than in childhood. (31/2 p ref)
In a small proportion of the normal population, stimulation in one modality can lead to perceptual experience in another, a phenomenon known as synaesthesia. In the most common form of synaesthesia, hearing a word can result in the experience of colour. We have used the technique of PET, which detects brain activity as changes of regional cerebral blood flow (rCBF), to study the physiology of colour-word synaesthesia in a group of six synaesthete women. During rCBF measurements synaesthetes and six controls were blindfolded and were presented with spoken words or pure tones. Auditory word, but not tone, stimulation triggered synaesthesia in synaesthetes. In both groups word stimulation compared with tone stimulation activated the classical language areas of the perisylvian regions. In synaesthetes, a number of additional visual associative areas, including the posterior inferior temporal cortex and the parieto-occipital junctions, were activated. The former has been implicated in the integration of colour with shape and in verbal tasks which require attention to visual features of objects to which words refer. Synaesthetes also showed activations in the right prefrontal cortex, insula and superior temporal gyrus. By contrast, no significant activity was detected in relatively lower visual areas, including areas V1, V2 and V4. These results suggest that colour-word synaesthesia may result from the activity of brain areas concerned with language and visual feature integration. In the case of colour-word synaesthesia, conscious visual experience appears to occur without activation of the primary visual cortex.
We used a colour Mondrian--an abstract scene with no recognizable objects--and its achromatic version to image the change in blood oxygenation in the brains of 12 human subjects, with the aim of learning more about the position and variability of the colour centre in the human brain. The results showed a consistent association of colour stimulation with activation of an area that is distinct from the primary visual areas, and lies in the ventral occipitotemporal cortex; we refer to it as human V4. The position of human V4, as defined on functional grounds, varies between individuals in absolute terms but is invariably found on the lateral aspect of the collateral sulcus on the fusiform gyrus. There was no indication of lingual gyral activation. In further studies designed to reveal the topographic map within V4, we stimulated the superior and inferior visual fields separately, using the same stimuli. We found that human V4 contains a representation of both the superior and inferior visual fields. In addition, there appears to be retinotopic organization of V4 with the superior visual field being represented more medially on the fusiform gyrus and the inferior field more laterally, the two areas abutting on one another. We find no evidence that suggests the existence of a separate representation of the inferior hemifield for colour in more dorsolateral regions of the occipital lobe.
Modern brain imaging techniques have now made it possible to study the neural sites and mechanisms underlying crossmodal processing in the human brain. This paper reviews positron emission tomography, functional magnetic resonance imaging (fMRI), event-related potential and magnetoencephalographic studies of crossmodal matching, the crossmodal integration of content and spatial information, and crossmodal learning. These investigations are beginning to produce some consistent findings regarding the neuronal networks involved in these distinct crossmodal operations. Increasingly, specific roles are being defined for the superior temporal sulcus, the inferior parietal sulcus, regions of frontal cortex, the insula cortex and claustrum. The precise network of brain areas implicated in any one study, however, seems to be heavily dependent on the experimental paradigms used, the nature of the information being combined and the particular combination of modalities under investigation. The different analytic strategies adopted by different groups may also be a significant factor contributing to the variability in findings. In this paper, we demonstrate the impact of computing intersections, conjunctions and interaction effects on the identification of audiovisual integration sites using existing fMRI data from our own laboratory. This exercise highlights the potential value of using statistical interaction effects to model electrophysiological responses to crossmodal stimuli in order to identify possible sites of multisensory integration in the human brain.
In 'colored-hearing' synesthesia, individuals report color experiences when they hear spoken words. If the synesthetic color experience resembles that of normal color perception, one would predict activation of parts of the visual system specialized for such perception, namely the human 'color center', referred to as either V4 or V8. Using functional magnetic resonance imaging (fMRI), we here locate the region activated by speech in synesthetes to area V4/V8 in the left hemisphere, and demonstrate overlap with V4/V8 activation in normal controls in response to color. No activity was detected in areas V1 or V2, suggesting that activity in primary visual cortex is not necessary for such experience. Control subjects showed no activity in V4/V8 when imagining colors in response to spoken words, despite overtraining on word-color associations similar to those spontaneously reported by synesthetes.
We review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect.
The world is experienced as a unified whole, but sensory systems do not deliver it to the brain in this way. Signals from different sensory modalities are initially registered in separate brain areas — even within a modality, features of the sensory mosaic such as colour, size, shape and motion are fragmented and registered in specialized areas of the cortex. How does this information become bound together in experience? Findings from the study of abnormal binding — for example, after stroke — and unusual binding — as in synaesthesia — might help us to understand the cognitive and neural mechanisms that contribute to solving this 'binding problem'.
We studied the functional organization of human posterior parietal and frontal cortex using functional magnetic resonance imaging (fMRI) to map preparatory signals for attending, looking, and pointing to a peripheral visual location. The human frontal eye field and two separate regions in the intraparietal sulcus were similarly recruited in all conditions, suggesting an attentional role that generalizes across response effectors. However, the preparation of a pointing movement selectively activated a different group of regions, suggesting a stronger role in motor planning. These regions were lateralized to the left hemisphere, activated by preparation of movements of either hand, and included the inferior and superior parietal lobule, precuneus, and posterior superior temporal sulcus, plus the dorsal premotor and anterior cingulate cortex anteriorly. Surface-based registration of macaque cortical areas onto the map of fMRI responses suggests a relatively good spatial correspondence between human and macaque parietal areas. In contrast, large interspecies differences were noted in the topography of frontal areas.
Many areas of the visual cortex are activated when blind people are stimulated naturally through other sensory modalities (e.g., haptically; Sadato et al., 1996). While this extraneous activation of visual areas via other senses in normal blind people might have functional value (Kauffman et al., 2002; Lessard et al., 1998), it does not lead to conscious visual experiences. On the other hand, electrical stimulation of the primary visual cortex in the blind does produce illusory visual phosphenes (Brindley and Lewin, 1968). Here we provide the first evidence that high-level visual areas not only retain their specificity for particular visual characteristics in people who have been blind for long periods, but that activation of these areas can lead to visual sensations. We used fMRI to demonstrate activity in visual cortical areas specifically related to illusory colored and spatially located visual percepts in a synesthetic man who has been completely blind for 10 years. No such differential activations were seen in late-blind or sighted non-synesthetic controls; neither were these areas activated during color-imagery in the late-blind synesthete, implying that this subject's synesthesia is truly a perceptual experience.
In some individuals, a visually presented letter or number automatically evokes the perception of a specific color, an experience known as color-grapheme synesthesia. It has been suggested that parietal binding mechanisms play a role in the phenomenon. We used a noninvasive stimulation technique, transcranial magnetic stimulation (TMS), to determine whether the posterior parietal lobe is critical for the integration of color and shape in color-grapheme synesthesia, as it appears to be for normal color-shape binding. Using a color-naming task with colored letters that were either congruent or incongruent with the synesthetic photism, we demonstrate that inhibition of the right posterior parietal lobe with repetitive TMS transiently attenuates synesthetic binding. These findings suggest that synesthesia (the induction of color from shape) relies on similar mechanisms as found in normal perception (where the perception of color is induced by wavelength).
We review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect.
Two experiments tested the effect that synaesthesia has on the processing of digits for a single participant, a 22-year-old female college student, who experiences colour mental images (photisms) for digits, music, sounds, etc. The experiments used Stroop-type materials that were digits in the colours of her photisms for two tasks: colour naming and digit naming. For colour naming, the hypothesis was that when the colour of the actual print of the digit mismatched the colour of the participant's digit photism, colour naming times would be slower than when the print and digit photism matched, or when the digit was in black print. For digit naming, it was predicted that naming the digit corresponding to a coloured circle (that corresponded to one of her photisms for digits) would take longer than naming digits printed in any colour. ANOVAs and Tukey tests supported these hypotheses (P Document Type: Research Article DOI: http://dx.doi.org/10.1080/026432999380951 Publication date: March 1, 1999 (document).ready(function() { var shortdescription = (".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } (".shortdescription a").click(function() { (".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher In this Subject: Anatomy & Physiology By this author: Mills, Carol Bergfeld ; Boteler, Edith Howell ; Oliver, Glenda K. GA_googleFillSlot("Horizontal_banner_bottom");
The experience of colour is a core element of human vision. Colours provide important symbolic and contextual information not conveyed by form alone. Moreover, the experience of colour can arise without external stimulation. For many people, visual memories are rich with colour imagery. In the unusual phenomenon of grapheme-colour synaesthesia, achromatic forms such as letters, words and numbers elicit vivid experiences of colour. Few studies, however, have examined the neural correlates of such internally generated colour experiences. We used functional magnetic resonance imaging (fMRI) to compare patterns of cortical activity for the perception of external coloured stimuli and internally generated colours in a group of grapheme-colour synaesthetes and matched non-synaesthetic controls. In a voluntary colour imagery task, both synaesthetes and non-synaesthetes made colour judgements on objects presented as grey scale photographs. In a synaesthetic colour task, we presented letters that elicited synaesthetic colours, and asked participants to perform a localisation task. We assessed the neural activity underpinning these two different forms of colour experience that occur in the absence of chromatic sensory input. In both synaesthetes and non-synaesthetes, voluntary colour imagery activated the colour-selective area, V4, in the right hemisphere. In contrast, the synaesthetic colour task resulted in unique activity for synaesthetes in the left medial lingual gyrus, an area previously implicated in tasks involving colour knowledge. Our data suggest that internally generated colour experiences recruit brain regions specialised for colour perception, with striking differences between voluntary colour imagery and synaesthetically induced colours.
Synaesthesia is a condition in which the input of one sensory modality triggers extraordinary additional experiences. On an explicit level, subjects affected by this condition normally report unidirectional experiences. In grapheme-colour synaesthesia for example, the letter A printed in black may trigger a red colour experience but not vice versa. However on an implicit level, at least for some types of synaesthesia, bidirectional activation is possible. In this study we tested whether bidirectional implicit activation is mediated by the same brain areas as explicit synaesthetic experiences. Specifically, we demonstrated suppression of implicit bidirectional activation with the application of transcranial magnetic stimulation over parieto-occipital brain areas. Our findings indicate that parieto-occipital regions are not only involved in explicit but also implicit synaesthetic binding.
Grapheme-color synesthesia is a neurological phenomenon in which letters and numbers (graphemes) consistently evoke particular colors (e.g. A may be experienced as red). The cross-activation theory proposes that synesthesia arises as a result of cross-activation between posterior temporal grapheme areas (PTGA) and color processing area V4, while the disinhibited feedback theory proposes that synesthesia arises from disinhibition of pre-existing feedback connections. Here we used magnetoencephalography (MEG) to test whether V4 and PTGA activate nearly simultaneously, as predicted by the cross-activation theory, or whether V4 activation occurs only after the initial stages of grapheme processing, as predicted by the disinhibited feedback theory. Using our high-resolution MEG source imaging technique (VESTAL), PTGA and V4 regions of interest (ROIs) were separately defined, and activity in response to the presentation of achromatic graphemes was measured. Activation levels in PTGA did not significantly differ between synesthetes and controls (suggesting similar grapheme processing mechanisms), whereas activation in V4 was significantly greater in synesthetes. In synesthetes, PTGA activation exceeded baseline levels beginning 105-109ms, and V4 activation did so 5ms later, suggesting nearly simultaneous activation of these areas. Results are discussed in the context of an updated version of the cross-activation model, the cascaded cross-tuning model of grapheme-color synesthesia.
In previous research the inheritance patterns of synaesthesia (eg experiencing colours from graphemes) has been studied and it was concluded that synaesthesia is most likely to be the outcome of a single gene passed on the X chromosome in a dominant fashion. In addition, it has been reported that the female-male ratio of synaesthetes is as high as 6:1 and the families of synaesthetes contain more female than male members. This raises the possibility that the gene may be associated with lethality in males. In this study we replicate and extend previous research by investigating the female-male ratio and inheritance patterns in a large sample of synaesthetic families (N = 85). We were able to verify the authenticity of grapheme-colour associates in at least one proband from each family using internal consistency. As before, our results show a female-male bias and are broadly consistent with an X-linked dominant mode of inheritance. However, there was no evidence of male lethality (eg synaesthetes are just as likely to give birth to sons as to daughters). Moreover, our female-male ratio of synaesthetes within families was 2:1--considerably lower than previous estimates. We speculate that men may be more reluctant to disclose synaesthesia than women (indeed, our female-male ratio based on self-referral was 3.7: 1). Finally, we discuss how the genotype may give rise to the phenotype in terms of changes in synaptogenesis or plasticity extending into childhood, to be subsequently shaped by the environment.
Grapheme-color synesthetes perceive particular colors when seeing a letter, word or number (grapheme). Functional neuroimaging studies have provided some evidence in favor of a neural basis for this type of synesthesia. Most of these studies have reported extra activations in the fusiform gyrus, which is known to be involved in color, letter and word processing. The present study examined different neuroanatomical features (i.e. cortical thickness, cortical volume and cortical surface area) in a sample of 48 subjects (24 grapheme-color synesthetes and 24 control subjects), and revealed increased cortical thickness, volume and surface area in the right and left fusiform gyrus and in adjacent regions, such as the lingual gyrus and the calcarine cortex, in grapheme-color synesthetes. In addition, we set out to analyze structural connectivity based on fractional anisotropy (FA) measurements in a subsample of 28 subjects (14 synesthetes and 14 control subjects). In contrast to the findings of a recent neuroanatomical study using modern diffusion tensor imaging measurement techniques, we did not detect any statistically significant difference in FA between synesthetes and non-synesthetes in the fusiform gyri. Our study thus supports the hypothesis of local anatomical differences in cortical characteristics in the vicinity of the V4 complex. The observed altered brain anatomy in grapheme-color synesthetes might be the anatomical basis for this particular form of synesthesia but it is also possible that the detected effects are a consequence (rather than the primary cause) of the life-long experience of grapheme-color synesthesia.
Developmental synaesthesia is typically characterised by the consistency of synaesthetic pairings, in that stimuli tend to generate the same synaesthetic responses over time (e.g., if A is red, it is always red). Although studies have illustrated consistency over many months and even several years, little is known about the longevity of reports outside the practical time-constraints of laboratory testing. Here we provide the first objective empirical evidence of synaesthetic consistency spanning from the 1970s to the current day (27 years) and use this longevity to identify the likely roots of such cross-modal associations.
A case of 'chromatic-lexical' (colour-word) synaesthesia is described, and its genuineness confirmed using the criterion of stable cross-modality imagery across time. The synaesthesia could not be accounted for by a memory hypothesis, nor was it associated with any psychiatric condition. Further analysis did not identify any semantic relationship between real words and colours, but the colours of nonwords were determined by the colours of the individual letters. Numbers also had their own stable colours. The experience of synaesthesia was triggered by other auditory stimuli, but most strongly by words. Cortical electrophysiological recording failed to reveal any abnormalities. An unusual organisation of modalities in the brain is postulated to account for the phenomenon.
Cortico-cortical projections for visual processing that originate from the striate cortex are organized into two streams. The dorsal stream projects to the parietal region and the ventral stream to the inferior temporal region. One hypothesis is that the dorsal stream processes visual spatial information, and the ventral stream processes visual object information. Although recognition of human faces or common objects has been shown preferentially to activate the ventral stream, the issue of when such processing starts to engage the ventral or the dorsal stream is not clear. The question explored in this study is whether processing of visual form per se without evoking the brain mechanisms that are associated with recognition of human faces or common objects is sufficient to activate the ventral stream more significantly relative to the condition when only visual spatial processing is involved. Functional magnetic resonance images were acquired while subjects performed a delayed comparison task in which either visual spatial or visual form information was processed. Cortical areas that were preferentially activated in visual spatial or visual form processing showed not only ventral-dorsal segregation, but also hemispheric laterality. The results extended previous findings by showing that preferential activation in the ventral pathway is not contingent upon such powerful stimuli as faces and common objects. Processing of simple visual form information is cause enough for such activation to be observed. A strong left hemisphere dominance in visual form recognition was also revealed. The observed laterality may be a reflection that the left hemisphere is more important in symbolic and/or semantic coding of visual form information.
We have used the technique of functional magnetic resonance imaging (fMRI) and a variety of colour paradigms to activate the human brain regions selective for colour. We show here that the region defined previously [Lueck et al. (1989) Nature, 340, 386-389; Zeki et al. (1991) J. Neurosci., 11, 641-649; McKeefry & Zeki (1997) Brain, 120, 2229-2242] as the human colour centre consists of two subdivisions, a posterior one, which we call V4 and an anterior one, which we refer to as V4alpha, the two together being part of the V4-complex. The posterior area is retinotopically organized while the anterior is not. We discuss our new findings in the context of previous studies of the cortical colour processing system in humans and monkeys. Our new insight into the organization of the colour centre in the human brain may also account for the variability in both severity and degree of recovery from lesions producing cerebral colour blindness (achromatopsia).
An automated coordinate-based system to retrieve brain labels from the 1988 Talairach Atlas, called the Talairach Daemon (TD), was previously introduced [Lancaster et al., 1997]. In the present study, the TD system and its 3-D database of labels for the 1988 Talairach atlas were tested for labeling of functional activation foci. TD system labels were compared with author-designated labels of activation coordinates from over 250 published functional brain-mapping studies and with manual atlas-derived labels from an expert group using a subset of these activation coordinates. Automated labeling by the TD system compared well with authors' labels, with a 70% or greater label match averaged over all locations. Author-label matching improved to greater than 90% within a search range of +/-5 mm for most sites. An adaptive grey matter (GM) range-search utility was evaluated using individual activations from the M1 mouth region (30 subjects, 52 sites). It provided an 87% label match to Brodmann area labels (BA 4 & BA 6) within a search range of +/-5 mm. Using the adaptive GM range search, the TD system's overall match with authors' labels (90%) was better than that of the expert group (80%). When used in concert with authors' deeper knowledge of an experiment, the TD system provides consistent and comprehensive labels for brain activation foci. Additional suggested applications of the TD system include interactive labeling, anatomical grouping of activation foci, lesion-deficit analysis, and neuroanatomy education.
Extrastriate area V4 is crucial for intermediate form vision and visual attention in nonhuman primates. Human neuroimaging suggests that an area in the lingual sulcus/fusiform gyrus may correspond to ventral V4 (V4v). We studied a human neurological patient, AR, with a putative V4v lesion. The lesion does not affect early visual processing (luminance, orientation, and motion perception). However, it does impair hue perception, intermediate form vision, and visual attention in the upper contralateral visual field. Form deficits occur during discrimination of illusory borders, Glass patterns, curvature, and non-Cartesian patterns. Attention deficits occur during discrimination of the relative positions of object parts, detection of low-salience targets, and orientation discrimination in the presence of distractors. This pattern of deficits is consistent with the known properties of area V4 in nonhuman primates, indicating that AR's lesion affects a cortical region functionally homologous to macaque V4.
Synesthesia is a conscious experience of systematically induced sensory attributes that are not experienced by most people under comparable conditions. Recent findings from cognitive psychology, functional brain imaging and electrophysiology have shed considerable light on the nature of synesthesia and its neurocognitive underpinnings. These cognitive and physiological findings are discussed with respect to a neuroanatomical framework comprising hierarchically organized cortical sensory pathways. We advance a neurobiological theory of synesthesia that fits within this neuroanatomical framework.
One of the major controversies in cognitive neuroscience is whether the primary visual cortex and nearby areas are involved in visual mental imagery. In an fMRI study we examined the brain activity of 10 healthy subjects under different task conditions: in the perception condition subjects saw complex geometrical shapes and had to decide whether other highlighted stimuli fell inside or outside the figure. In the imagery condition subjects saw only the highlighted stimuli and were instructed to imagine the previously studied geometrical shapes to solve the same task. Although the behavioral data show a distance effect that would be expected based on topographically organized mental images, the functional imaging data do not show increased activity in the primary visual cortex in the imagery condition. In the occipital cortex a slightly increased activity was found only in the visual association cortex (BA 19), whereas the highest activation was observed in the parietal cortex (BA 7 and 40). The results of the study do not support the assumption that the primary visual cortex is involved in visual mental imagery, but rather that a network of spatial subsystems and higher visual areas appears to be involved.
It has been suggested that internally generated visual perception involves the primary visual cortex V1. To test this hypothesis, a functional MRI study was conducted with a female subject with orthographic color-word synesthesia. This subject was selected as she reported clear involuntary visualization of auditorily presented verbal material. Hearing a word resulted in seeing the word in a particular color. fMRI scans were acquired while the subject performed two verbal tasks (passive listening to words and verbal fluency). Significant activity was detected in primary visual cortex, in the absence of external visual stimulation. This finding provides evidence for a role of modulatory feedback connections between associative and primary visual areas in visual experience without direct visual stimulation.
The organization of macaque posterior parietal cortex (PPC) reflects its functional specialization in integrating polymodal sensory information for object recognition and manipulation. Neuropsychological and recent human imaging studies imply equivalencies between human and macaque PPC, and in particular, the cortex buried in the intraparietal sulcus (IPS). Using functional MRI, we tested the hypothesis that an area in human anterior intraparietal cortex is activated when healthy subjects perform a crossmodal visuo-tactile delayed matching-to-sample task with objects. Tactile or visual object presentation (encoding and recognition) both significantly activated anterior intraparietal cortex. As hypothesized, neural activity in this area was further enhanced when subjects transferred object information between modalities (crossmodal matching). Based on both the observed functional properties and the anatomical location, we suggest that this area in anterior IPS is the human equivalent of macaque area AIP.
A recent study has put forward a physiologically plausible population model that implements a parts-based shape-coding scheme for macaque visual area V4.
We used functional magnetic resonance imaging (fMRI) to assess the maximal degree of shared neural processing in visual mental imagery and visual perception. Participants either visualized or saw faint drawings of simple objects, and then judged specific aspects of the drawings (which could only be evaluated properly if they used the correct stimulus). The results document that visual imagery and visual perception draw on most of the same neural machinery. However, although the vast majority of activated voxels were activated during both conditions, the spatial overlap was neither complete nor uniform; the overlap was much more pronounced in frontal and parietal regions than in temporal and occipital regions. This finding may indicate that cognitive control processes function comparably in both imagery and perception, whereas at least some sensory processes may be engaged differently by visual imagery and perception.
In the macaque, the posterior parietal cortex (PPC) integrates multimodal sensory information for planning and coordinating complex movements. In particular, the areas around the intraparietal sulcus (IPS) serve as an interface between the sensory and motor systems to allow for coordinated movements in space. Because recent imaging studies suggest a comparable functional and anatomical organization of human and monkey IPS, we hypothesized that in humans, as in macaques, the medial intraparietal cortex (area MIP) subserves visuomotor transformations. To test this hypothesis, changes of neural activity were measured using functional magnetic resonance imaging (fMRI) while healthy subjects performed a joystick paradigm similar to the ones previously employed in macaques for studying area MIP. As hypothesized, visuomotor coordinate transformation subserving goal-directed hand movements activated superior parietal cortex with the local maximum of increased neural activity lying in the medial wall of IPS. Compared to the respective visuomotor control conditions, goal-directed hand movements under predominantly proprioceptive control activated a more anterior part of medial IPS, whereas posterior medial IPS was more responsive to visually guided hand movements. Contrasting the two coordinate transformation conditions, changing the modality of movement guidance (visual/proprioceptive) did not significantly alter the BOLD signal within IPS but demonstrated differential recruitment of modality specific areas such as V5/MT and sensorimotor cortex/area 5, respectively. The data suggest that the human medial intraparietal cortex subserves visuomotor transformation processes to control goal-directed hand movements independently from the modality-specific processing of visual or proprioceptive information.
Grapheme-color synesthetes experience specific colors associated with specific number or letter characters. To determine the neural locus of this condition, we compared behavioral and fMRI responses in six grapheme-color synesthetes to control subjects. In our behavioral experiments, we found that a subject's synesthetic experience can aid in texture segregation (experiment 1) and reduce the effects of crowding (experiment 2). For synesthetes, graphemes produced larger fMRI responses in color-selective area human V4 than for control subjects (experiment 3). Importantly, we found a correlation within subjects between the behavioral and fMRI results; subjects with better performance on the behavioral experiments showed larger fMRI responses in early retinotopic visual areas (V1, V2, V3, and hV4). These results suggest that grapheme-color synesthesia is the result of cross-activation between grapheme-selective and color-selective brain areas. The correlation between the behavioral and fMRI results suggests that grapheme-color synesthetes may constitute a heterogeneous group.
Correlating the activation foci identified in functional imaging studies of the human brain with structural (e.g., cytoarchitectonic) information on the activated areas is a major methodological challenge for neuroscience research. We here present a new approach to make use of three-dimensional probabilistic cytoarchitectonic maps, as obtained from the analysis of human post-mortem brains, for correlating microscopical, anatomical and functional imaging data of the cerebral cortex. We introduce a new, MATLAB based toolbox for the SPM2 software package which enables the integration of probabilistic cytoarchitectonic maps and results of functional imaging studies. The toolbox includes the functionality for the construction of summary maps combining probability of several cortical areas by finding the most probable assignment of each voxel to one of these areas. Its main feature is to provide several measures defining the degree of correspondence between architectonic areas and functional foci. The software, together with the presently available probability maps, is available as open source software to the neuroimaging community. This new toolbox provides an easy-to-use tool for the integrated analysis of functional and anatomical data in a common reference space.