[show abstract][hide abstract] ABSTRACT: Objective: Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects the corpus callosum (CC), which plays a key role in interhemispheric coupling in high-demand conditions. Using 3D callosal measurements and a letter-matching paradigm, this 2-part study investigated the neural substrate of interhemispheric coupling in individuals with AD or amnestic mild cognitive impairment (a-MCI) and age-matched healthy individuals (HC). Method: Thirty-three right-handed participants were MRI scanned to measure the volume of the CC in 5 sections. In Study 1, AD, a-MCI, and HC individuals performed a low-demand perceptual letter shape-matching task (e.g., A-A); in Study 2, a-MCI and HC individuals performed a "case-sensitive" letter-matching task (Study 2A) and a "load-sensitive" letter-matching task (Study 2B). Results: The results showed a positive correlation between Response Times and the midbody of the CC at the lowest cognitive demand level (Study 1) in participants with AD, and the total CC, midbody, caudal body, and isthmus of the CC at high cognitive demand levels (Study 2A) in normal aging. The volume of the anterior part of the CC was significantly negatively correlated with the interhemispheric behavioral indices for the a-MCI group (Study 1 and Study 2B). Conclusion: This study provides evidence that interhemispheric coupling may constitute a flexible mechanism that can improve the brain's ability to meet processing demands for low cognitive demand in AD and for high cognitive demand in normal aging. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
[show abstract][hide abstract] ABSTRACT: Backgrounds: Evidence exists that the observation of actions performed by others enhance word retrieval and can be used in aphasia rehabilitation to treat naming impairments. Aim: The aim of the present study was to assess to what extent action observation treatment may improve verb retrieval in chronic aphasics. Design: This was an observational study. Setting: Patients were recruited from the Neurorehabilitation Centre of Ancona Hospital. Population: Six aphasic patients underwent an intensive language training to improve verb naming. Methods:Language evaluation was carried out before and after the treatment. A rehabilitation therapy based on observation of actions was administered daily to each patient for two consecutive weeks. Four different rehabilitation procedures were adopted: 1) "observation of action performed by the examiner"; 2) "observation and then execution of action"; 3) "observation of videoclips of actions"; and, as a control condition; 4) "observation of action and execution of meaningless movement". Results: In four participants, a significant improvement in verb retrieval was found for the three experimental procedures (χ2 (3)=75.212, P<0.0001), with respect to the control condition. No significant improvement was observed in the two patients with severe deficits in verb semantics (χ2 (3)=0.592, P=0.892). Conclusions: Action observation therapy may become a useful intervention strategy to promote verb retrieval in aphasic patients. Clinical Rehabilitation Impact: The observation of videoclips of actions may be an efficacious alternative approach to traditional rehabilitation programs for lexical deficits. This finding endorses the planning of innovative low-cost interventions in language rehabilitation.
European journal of physical and rehabilitation medicine 03/2013; · 2.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: The exact anatomical localization of right hemisphere lesions that lead to left spatial neglect is still debated. The effect of confounding factors such as acute diaschisis and hypoperfusion, visual field defects, and lesion size may account for conflicting results that have been reported in the literature. Here, we present a comprehensive anatomical investigation of the gray- and white matter lesion correlates of left spatial neglect, which was run in a sample 58 patients with subacute or chronic vascular strokes in the territory of the right middle cerebral artery. Standard voxel-based correlates confirmed the role played by lesions in the posterior parietal cortex (supramarginal gyrus, angular gyrus, and temporal-parietal junction), in the frontal cortex (frontal eye field, middle and inferior frontal gyrus), and in the underlying parietal-frontal white matter. Using a new diffusion tensor imaging-based atlas of the human brain, we were able to run, for the first time, a detailed analysis of the lesion involvement of subcortical white matter pathways. The results of this analysis revealed that, among the different pathways linking parietal with frontal areas, damage to the second branch of the superior longitudinal fasciculus (SLF II) was the best predictor of left spatial neglect. The group study also revealed a subsample of patients with neglect due to focal lesion in the lateral-dorsal portion of the thalamus, which connects the premotor cortex with the inferior parietal lobule. The relevance of fronto-parietal disconnection was further supported by complete in vivo tractography dissection of white matter pathways in 2 patients, one with and the other without signs of neglect. These 2 patients were studied both in the acute phase and 1 year after stroke and were perfectly matched for age, handedness, stroke onset, lesion size, and for cortical lesion involvement. Taken together, the results of the present study support the hypothesis that anatomical disconnections leading to a functional breakdown of parietal-frontal networks are an important pathophysiological factor leading to chronic left spatial neglect. Here, we propose that different loci of SLF disconnection on the rostro-caudal axis can also be associated with disconnection of short-range white matter pathways within the frontal or parietal areas. Such different local disconnection patterns can play a role in the important clinical variability of the neglect syndrome.
[show abstract][hide abstract] ABSTRACT: Spatial reasoning has a relevant role in mathematics and helps daily computational activities. It is widely assumed that in cultures with left-to-right reading, numbers are organized along the mental equivalent of a ruler, the mental number line, with small magnitudes located to the left of larger ones. Patients with right brain damage can disregard smaller numbers while mentally setting the midpoint of number intervals. This has been interpreted as a sign of spatial neglect for numbers on the left side of the mental number line and taken as a strong argument for the intrinsic left-to-right organization of the mental number line. Here, we put forward the understanding of this cognitive disability by discovering that patients with right brain damage disregard smaller numbers both when these are mapped on the left side of the mental number line and on the right side of an imagined clock face. This shows that the right hemisphere supports the representation of small numerical magnitudes independently from their mapping on the left or the right side of a spatial-mental layout. In addition, the study of the anatomical correlates through voxel-based lesion-symptom mapping and the mapping of lesion peaks on the diffusion tensor imaging-based reconstruction of white matter pathways showed that the rightward bias in the imagined clock-face was correlated with lesions of high-level middle temporal visual areas that code stimuli in object-centred spatial coordinates, i.e. stimuli that, like a clock face, have an inherent left and right side. In contrast, bias towards higher numbers on the mental number line was linked to white matter damage in the frontal component of the parietal-frontal number network. These anatomical findings show that the human brain does not represent the mental number line as an object with an inherent left and right side. We conclude that the bias towards higher numbers in the mental bisection of number intervals does not depend on left side spatial, imagery or object-centred neglect and that it rather depends on disruption of an abstract non-spatial representation of small numerical magnitudes.
[show abstract][hide abstract] ABSTRACT: In previous studies, we investigated a group of subjects who had suffered from a severe non missile traumatic brain injury (nmTBI) without macroscopic focal lesions and we found brain atrophy involving the hippocampus, fornix, corpus callosum, optic chiasm, and optic radiations. Memory test scores correlated mainly with fornix volumes [37,38]. In the present study, we re-examined 11 of these nmTBI subjects approximately 8 yr later. High-spatial resolution T1 weighted magnetic resonance images of the brain (1mm(3)) and standardised memory tests were performed once more in order to compare brain morphology and memory performance originally assessed 3-13 months after head injury (first study) and after 8-10 yr (present study). An overall improvement of memory test performance was demonstrated in the latest assessment, indicating that cognitive recovery in severe nmTBI subjects had not been completed within 3-13 months post-injury. It is notable that the volumes of the fornix and the hippocampus were reduced significantly from normal controls, but these volumes do not differ appreciatively between nmTBI subjects at first (after ∼1 yr) and at second (after ∼8 yr) scans. On the contrary, a clear reduction in the volume of the corpus callosus can be observed after ∼1 yr and a further significant reduction is evident after ∼8 yr, indicating that the neural degeneration in severe nmTBI continues long after the head trauma and relates to specific structures and not to the overall brain.
Brain research bulletin 03/2012; 87(4-5):373-82. · 2.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: A number of studies have shown that modulating cortical activity by means of transcranial direct current stimulation (tDCS) affects the performance of both healthy and brain-damaged subjects. In this study, we investigated the potential of tDCS for the recovery of apraxia of speech in 3 patients with stroke-induced aphasia. Over 2 weeks, three aphasic subjects participated in a randomized double-blinded experiment involving intensive language training for their articulatory difficulties in two tDCS conditions. Each subject participated in five consecutive daily sessions of anodic tDCS (20 min, 1 mA) and sham stimulation over the left inferior frontal gyrus (referred to as Broca's area) while they performed a repetition task. By the end of each week, a significant improvement was found in both conditions. However, all three subjects showed greater response accuracy in the anodic than in the sham condition. Moreover, results for transfer of treatment effects, although different across subjects, indicate a generalization of the recovery at the language test. Subjects 2 and 3 showed a significant improvement in oral production tasks, such as word repetition and reading, while Subjects 1 and 2 had an unexpected significant recovery in written naming and word writing under dictation tasks. At three follow-ups (1 week, 1 and 2 months after the end of treatment), response accuracy was still significantly better in the anodic than in sham condition, suggesting a long-term effect on the recovery of their articulatory gestures.
Behavioural brain research 08/2011; 225(2):498-504. · 3.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: Detailed cytoarchitectonic studies of the human cerebral cortex appeared during the first quarter of the 20th century. The incorporation of the cytoarchitectonic map by Brodmann (1909) in the Talairach proportional stereotaxic space (Talairach and Tournoux, 1988) has established the Brodmann numerical nomenclature as the basis for describing the cortical location of structural and functional findings obtained with modern neuroimaging. In experimental anatomical and physiological investigations of the macaque monkey performed during the last 50 years, the numerical architectonic nomenclature used to describe findings in the prefrontal cortex has been largely based on the map by Walker (1940). Unfortunately, the map by Walker was not based on a comparative investigation of the cytoarchitecture of the human and macaque monkey prefrontal cortex and, as a result, the nomenclature and the criteria for demarcating areas in the two primate species are not always consistent. These discrepancies are a major obstacle in the ability to compare experimental findings from nonhuman primates with results obtained in functional and structural neuroimaging of the human brain. The present article outlines these discrepancies in the classical maps and describes comparative investigations of the cytoarchitecture of the prefrontal cortex of the macaque monkey and human (Petrides and Pandya, 1994, 1999, 2002a) in order to resolve these discrepancies and enable easy translation of experimental research in the monkey to findings in the human brain obtained with modern neuroimaging.
[show abstract][hide abstract] ABSTRACT: One dimension of understanding the functions of the prefrontal cortex is knowledge of cortical connectivity. We have surveyed three aspects of prefrontal cortical connections: local projections (within the frontal lobe), the termination patterns of long association (post-Rolandic) projections, and the trajectories of major fiber pathways. The local connections appear to be organized in relation to dorsal (hippocampal origin) and ventral (paleocortical origin) architectonic trends. According to the proposal of a dual origin of the cerebral cortex, cortical areas can be traced as originating from archicortex (hippocampus) on the one hand, and paleocortex, on the other hand, in a stepwise manner (e.g., Sanides, 1969; Pandya and Yeterian, 1985). Prefrontal areas within each trend are connected with less architectonically differentiated areas, and also with more differentiated areas. Such organization may allow for the systematic exchange of information within each architectonic trend. The long connections of the prefrontal cortex with post-Rolandic regions seem to be organized preferentially in relation to dorsal and ventral prefrontal architectonic trends. Prefrontal areas are connected with post-Rolandic auditory, visual and somatosensory association areas, and with multimodal and paralimbic regions. This long connectivity likely works in conjunction with local connections to serve prefrontal cortical functions. The afferent and efferent connections of the prefrontal cortex with post-Rolandic regions are conveyed by specific long association pathways. These pathways as well appear to be organized in relation to dorsal and ventral prefrontal architectonic trends. Finally, although prefrontal areas have preferential connections in relation to dual architectonic trends, it is clear that there are interconnections between and among areas in each trend, which may provide a substrate for the overall integrative function of the prefrontal cortex. Prefrontal corticocortical connectivity may help to elucidate both region-specific and integrative perspectives on the functions of the prefrontal cortex.
[show abstract][hide abstract] ABSTRACT: This study tested the hypothesis of electroencephalographic reactivity (EEG-R) as a reliable tool for the prognostic evaluation of consciousness recovery in post-acute brain injury.
EEG was recorded in 50 unconscious patients. All patients had a GCS ≤8 and LCF score ≤2. They suffered from traumatic brain injury, cerebrovascular disease or anoxia. EEG was classified according to Synek classification (1988) as benign, malignant and 'uncertain significance'. EEG-R to painful stimuli was tested.
Twenty per cent of patients fulfilled the criteria for benign prognosis, 38% for malignant prognosis, while 42% of them were included in the 'uncertain' category, preventing them from stating a prognosis. EEG-R was detected in 48% of patients classified 'uncertain' and 92% of them recovered consciousness within 5 months from EEG recording. Multivariable analysis indicates that an unconscious patient admitted to the Rehabilitation Unit within 2 months from brain injury, with a LCF score equal to 2 and the presence of EEG-R has a probability of recovery of consciousness higher than 97%.
EEG-R is a good positive factor for the prognosis of recovery of consciousness in the post-acute phase of brain injury, with a high specificity (88.9%). Nevertheless, its absence is not invariably associated with a poor prognosis.
[show abstract][hide abstract] ABSTRACT: A number of studies have shown that modulating cortical activity by means of transcranial direct current stimulation (tDCS) affects performances of both healthy and brain-damaged subjects. In this study, we investigated the potential of tDCS to enhance associative verbal learning in 10 healthy individuals and to improve word retrieval deficits in three patients with stroke-induced aphasia. In healthy individuals, tDCS (20 min, 1 mA) was applied over Wernicke's area (position CP5 of the International 10-20 EEG System) while they learned 20 new "words" (legal nonwords arbitrarily assigned to 20 different pictures). The healthy subjects participated in a randomized counterbalanced double-blind procedure in which they were subjected to one session of anodic tDCS over left Wernicke's area, one sham session over this location and one session of anodic tDCS stimulating the right occipito-parietal area. Each experimental session was performed during a different week (over three consecutive weeks) with 6 days of intersession interval. Over 2 weeks, three aphasic subjects participated in a randomized double-blind experiment involving intensive language training for their anomic difficulties in two tDCS conditions. Each subject participated in five consecutive daily sessions of anodic tDCS (20 min, 1 mA) and sham stimulation over Wernicke's area while they performed a picture-naming task. By the end of each week, anodic tDCS had significantly improved their accuracy on the picture-naming task. Both normal subjects and aphasic patients also had shorter naming latencies during anodic tDCS than during sham condition. At two follow-ups (1 and 3 weeks after the end of treatment), performed only in two aphasic subjects, response accuracy and reaction times were still significantly better in the anodic than in the sham condition, suggesting a long-term effect on recovery of their anomic disturbances.
Journal of Cognitive Neuroscience 10/2010; 23(9):2309-23. · 4.49 Impact Factor
[show abstract][hide abstract] ABSTRACT: The pervasiveness of word-finding difficulties in aphasia has motivated several theories regarding management of the deficit and its effectiveness. Recently, the hypothesis was advanced that instead of simply accompanying speech gestures participate in language production by increasing the semantic activation of words grounded in sensory-motor features, hence facilitating retrieval of the word form. Based on this assumption, several studies have developed rehabilitation therapies in which the use of gestures reinforces word recovery. Until now, however, no studies have investigated the beneficial effects of gesture observation in word retrieval. Here, we report whether a different modality of accessing action-motor representation interacts with language by promoting long lasting recovery of verb retrieval deficits in aphasic patients. Six aphasic participants with a selective deficit in verb retrieval participated in an intensive rehabilitation training that included three daily sessions over two consecutive weeks. Each session corresponded to a different rehabilitation procedure: (1) "action observation", (2) "action observation and execution", and (3) "action observation and meaningless movement". In the four participants with lexical phonologically based disturbances, significant improvement of verb retrieval was found only with "action observation" and "action observation and execution". No significant differences were present between the two procedures. Moreover, the follow-up testing revealed long-term verb recovery that was still present two months after the two treatments ended. In support of a multimodal representation of action, these findings univocally demonstrate that gestures interact with the speech production system, inducing long-lasting modification at the lexical level in patients with cerebral damage.
[show abstract][hide abstract] ABSTRACT: Left unilateral neglect is frequently reported after right hemispheric lesions of the middle cerebral artery (MCA) damaging the parietal-frontal cortical-subcortical network subserving space representation and awareness. However, accumulating evidence shows that neglect can also follow lesions of the posterior cerebral artery (PCA) that do not directly affect this parietal-frontal network. Surgical studies in the monkeys have demonstrated that complete callosal resection combined with lesion of the right optic tract entirely deprives the right hemisphere of visual inputs from the left hemispace provoking severe left unilateral neglect. Here, through the detailed study of two patients we show, for the first time, that PCA lesions selectively affecting the splenium of the corpus callosum and the adjacent right primary visual cortex provoke severe neglect selectively restricted to the visual domain. No trace of personal, motor or representational-imagery neglect was found. Also at variance with previous case studies in which neglect followed lesion of the trunk or the genu of the corpus callosum, no restriction of neglect to tasks performed with the right hand, no left hemispatial limb akinesia, no tactile extinction for the left hand and no tactile anomia for stimuli explored with the left hand were observed. These findings demonstrate that brain lesions depriving intact parietal and frontal attentional areas from specific sensory inputs can yield spatial neglect limited to specific sensory modalities or sectors of space.
Experimental Brain Research 04/2010; 206(2):209-17. · 2.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: Humans map numbers upon a mental number line (MNL) on which small integers are placed to the left of larger ones [1-9]. Here, we show that human adults systematically shift the subjective midpoints of number intervals away from the borders separating contiguous tens along the MNL. Number intervals are erroneously bisected further to the right the closer they are to the left starting point of the tens and further to the left the closer they are to the right endpoint of the tens. Similarly, right-brain-damaged patients neglecting the left side of the MNL [10-12] show enhanced pathological rightward deviation in the bisection of number intervals located toward the left starting point of the tens and reduced deviation for intervals located toward the right endpoint of the tens. These data disclose the effects that the recursive grouping of symbolic decimal numerals within the tens has brought on the phylogenetically and ontogenetically foregoing spatial representation of magnitudes [13-16].
Current biology: CB 04/2009; 19(8):682-7. · 10.99 Impact Factor
[show abstract][hide abstract] ABSTRACT: Seminal case reports collected during the middle part of the XX century, designated the parietal lobe as the principal area of damage in patients suffering from contralesional spatial neglect (Brain WC. Visual disorientation with special reference to lesions of the right cerebral hemisphere. Brain 1941;64:224-72; Paterson A, Zangwill O. Disorders of visual space perception associated with lesions of the right cerebral hemisphere. Brain 1944;67:331-58; McFie J, Piercy MF, Zangwill O. Visual spatial agnosia associated with lesions of the right hemisphere. Brain 1950;73:167-90). Based on this evidence, textbooks of neurology have traditionally referred to neglect as a "parietal sign". This view found complete accomplishment in the 1986 group study by Vallar and Perani, who confirmed that the inferior parietal lobe was the area most frequently involved in neglect patients with lesions confined to the cerebral cortex and lesions involving subcortical gray matter nuclei. In the same study, it was found that lesions limited to subcortical white matter were rarely associated with neglect. Here, we reconsider recent accumulating evidence, gathered from investigations in animals and human patients, supporting the partially different view that damage involvement of long-range white matter bundles connecting the parietal to the frontal lobe, importantly influence the occurrence and severity of spatial neglect. These findings do not dispute the role of the parietal and frontal cortex in spatial attention and space-related behaviour, but call for a reappraisal of the respective roles of disruption of white matter connections and damage of gray matter cortical modules in the pathophysiology of neglect. Disentangling the connectional and modular anatomical correlates of neglect may be crucial to better understand the pathophysiology of this syndrome, to explain the manifold clinical dissociations often encountered in clinical practice and to increase the impact of behavioural and pharmacological interventions. In this review, we focus on the role of within-hemisphere white-matter disconnection. The role of interhemispheric disconnection, perhaps the oldest connectionist theory of neglect (Geschwind N. Disconnexion syndromes in animals and man - part II. Brain 1965;88:585-644), was extensively treated elsewhere (Bartolomeo P, Thiebaut de Schotten M, Doricchi F. Left unilateral neglect as a disconnection syndrome, Cerebral Cortex 2007;45:3127-48). We first summarise the structure of long-range white matter connections within the cerebral hemispheres and sketch a brief historical review of the original findings suggesting the role of intrahemispheric disconnection to neglect. We then revisit some of the current functional interpretation of the neglect syndrome in the light of disconnectionist approach and review evidences favouring or disfavouring a purely disconnectionist interpretation of the syndrome. Finally, we address the issue of diagnostic criteria to be used in future anatomo-clinical studies aiming at investigating the role of white matter and gray matter dysfunctions in spatial neglect.