scholarly journals Increased BOLD Variability in the Parietal Cortex and Enhanced Parieto-Occipital Connectivity during Tactile Perception in Congenitally Blind Individuals

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Andrea Leo ◽  
Giulio Bernardi ◽  
Giacomo Handjaras ◽  
Daniela Bonino ◽  
Emiliano Ricciardi ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Information Integration ◽  
Occipital Cortex ◽  
Processing Efficiency ◽  
Neural Integration ◽  
Multimodal Information ◽  
Congenitally Blind ◽  
Cortical Regions ◽  
Blind Individuals

Previous studies in early blind individuals posited a possible role of parieto-occipital connections in conveying nonvisual information to the visual occipital cortex. As a consequence of blindness, parietal areas would thus become able to integrate a greater amount of multimodal information than in sighted individuals. To verify this hypothesis, we compared fMRI-measured BOLD signal temporal variability, an index of efficiency in functional information integration, in congenitally blind and sighted individuals during tactile spatial discrimination and motion perception tasks. In both tasks, the BOLD variability analysis revealed many cortical regions with a significantly greater variability in the blind as compared to sighted individuals, with an overlapping cluster located in the left inferior parietal/anterior intraparietal cortex. A functional connectivity analysis using this region as seed showed stronger correlations in both tasks with occipital areas in the blind as compared to sighted individuals. As BOLD variability reflects neural integration and processing efficiency, these cross-modal plastic changes in the parietal cortex, even if described in a limited sample, reinforce the hypothesis that this region may play an important role in processing nonvisual information in blind subjects and act as a hub in the cortico-cortical pathway from somatosensory cortex to the reorganized occipital areas.

scholarly journals Thalamocortical Connectivity and Microstructural Changes in Congenital and Late Blindness

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
N. H. Reislev ◽  
T. B. Dyrby ◽  
H. R. Siebner ◽  
H. Lundell ◽  
M. Ptito ◽  
...  
Keyword(s):  
Diffusion Tensor ◽  
Current Knowledge ◽  
Occipital Cortex ◽  
Ample Evidence ◽  
Microstructural Changes ◽  
Congenitally Blind ◽  
Thalamocortical Network ◽  
Cortical Regions ◽  
Corticocortical Projections ◽  
Blind Individuals

There is ample evidence that the occipital cortex of congenitally blind individuals processes nonvisual information. It remains a debate whether the cross-modal activation of the occipital cortex is mediated through the modulation of preexisting corticocortical projections or the reorganisation of thalamocortical connectivity. Current knowledge on this topic largely stems from anatomical studies in animal models. The aim of this study was to test whether purported changes in thalamocortical connectivity in blindness can be revealed by tractography based on diffusion-weighted magnetic resonance imaging. To assess the thalamocortical network, we used a clustering method based on the thalamic white matter projections towards predefined cortical regions. Five thalamic clusters were obtained in each group representing their cortical projections. Although we did not find differences in the thalamocortical network between congenitally blind individuals, late blind individuals, and normal sighted controls, diffusion tensor imaging (DTI) indices revealed significant microstructural changes within thalamic clusters of both blind groups. Furthermore, we find a significant decrease in fractional anisotropy (FA) in occipital and temporal thalamocortical projections in both blind groups that were not captured at the network level. This suggests that plastic microstructural changes have taken place, but not in a degree to be reflected in the tractography-based thalamocortical network.

scholarly journals Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

2015 ◽  
Vol 27 (8) ◽  
pp. 1633-1647 ◽  
Author(s):  
Ben Deen ◽  
Rebecca Saxe ◽  
Marina Bedny
Keyword(s):  
Working Memory ◽  
Functional Connectivity ◽  
Sentence Comprehension ◽  
Memory Load ◽  
Memory Task ◽  
Occipital Cortex ◽  
Memory Systems ◽  
Functional Responses ◽  
Congenitally Blind ◽  
Blind Individuals

In congenital blindness, the occipital cortex responds to a range of nonvisual inputs, including tactile, auditory, and linguistic stimuli. Are these changes in functional responses to stimuli accompanied by altered interactions with nonvisual functional networks? To answer this question, we introduce a data-driven method that searches across cortex for functional connectivity differences across groups. Replicating prior work, we find increased fronto-occipital functional connectivity in congenitally blind relative to blindfolded sighted participants. We demonstrate that this heightened connectivity extends over most of occipital cortex but is specific to a subset of regions in the inferior, dorsal, and medial frontal lobe. To assess the functional profile of these frontal areas, we used an n-back working memory task and a sentence comprehension task. We find that, among prefrontal areas with overconnectivity to occipital cortex, one left inferior frontal region responds to language over music. By contrast, the majority of these regions responded to working memory load but not language. These results suggest that in blindness occipital cortex interacts more with working memory systems and raise new questions about the function and mechanism of occipital plasticity.

scholarly journals Changes in thalamocortical connectivity as a potential mechanism of cross-modal plasticity in congenitally blind individuals

2018 ◽  
Author(s):  
Theo Marins ◽  
Maite Russo ◽  
Erika Rodrigues ◽  
jorge Moll ◽  
Daniel Felix ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Cortical Thickness ◽  
Visual Information ◽  
Brain Plasticity ◽  
Temporal Cortex ◽  
Occipital Cortex ◽  
Brain Structures ◽  
Congenitally Blind ◽  
Blind Individuals ◽  
Neuroimaging Techniques

ABSTRACTEvidence of cross-modal plasticity in blind individuals has been reported over the past decades showing that non-visual information is carried and processed by classical “visual” brain structures. This feature of the blind brain makes it a pivotal model to explore the limits and mechanisms of brain plasticity. However, despite recent efforts, the structural underpinnings that could explain cross-modal plasticity in congenitally blind individuals remain unclear. Using advanced neuroimaging techniques, we mapped the thalamocortical connectivity and assessed cortical thickness and integrity of white matter of congenitally blind individuals and sighted controls to test the hypothesis that aberrant thalamocortical pattern of connectivity can pave the way for cross-modal plasticity. We described a direct occipital takeover by the temporal projections from the thalamus, which would carry non-visual information (e.g. auditory) to the visual cortex in congenitally blinds. In addition, the amount of thalamo-occipital connectivity correlated with the cortical thickness of primary visual cortex (V1), supporting a probably common (or related) reorganization phenomena. Our results suggest that aberrant thalamocortical connectivity as one possible mechanism of cross-modal plasticity in blinds, with potential impact on cortical thickness of V1.SIGNIFICANT STATEMENTCongenitally blind individuals often develop greater abilities on spared sensory modalities, such as increased acuity in auditory discrimination and voice recognition, when compared to sighted controls. These functional gains have been shown to rely on ‘visual’ cortical areas of the blind brain, characterizing the phenomenon of cross-modal plasticity. However, its anatomical underpinnings in humans have been unsuccessfully pursued for decades. Recent advances of non-invasive neuroimaging techniques allowed us to test the hypothesis of abnormal thalamocortical connectivity in congenitally blinds. Our results showed an expansion of the thalamic connections to the temporal cortex over those that project to the occipital cortex, which may explain, the cross-talk between the visual and auditory systems in congenitally blind individuals.

Working memory training in congenitally blind individuals results in an integration of occipital cortex in functional networks

2018 ◽  
Vol 348 ◽  
pp. 31-41 ◽  
Author(s):  
Helene Gudi-Mindermann ◽  
Johanna M. Rimmele ◽  
Guido Nolte ◽  
Patrick Bruns ◽  
Andreas K. Engel ◽  
...  
Keyword(s):  
Working Memory ◽  
Occipital Cortex ◽  
Working Memory Training ◽  
Memory Training ◽  
Functional Networks ◽  
Congenitally Blind ◽  
Blind Individuals

scholarly journals A distinctive neural nexus in blind individuals supports Braille reading

2021 ◽  
Author(s):  
Ruxue WANG ◽  
Jiangtao GONG ◽  
Chenying ZHAO ◽  
Yingqing XU ◽  
Bo HONG
Keyword(s):  
Visual Cortex ◽  
Functional Connectivity ◽  
Frontal Cortex ◽  
Reading Proficiency ◽  
Occipital Cortex ◽  
Resting State Functional Connectivity ◽  
Crossmodal Plasticity ◽  
Blind Individuals ◽  
Language Areas

In the absence of visual input, occipital 'visual' cortex of blind people has been found to be engaged in non-visual higher cognitive tasks. Although the increased functional connectivity between 'visual' cortex and frontal cortex in the blind has been observed, the specific organization and functional role of this connectivity change remain to be elucidated. Here, we tested resting-state functional connectivity for primary 'visual' cortex (V1) and higher-tier lateral occipital cortex (LOC) in people with acquired blindness, and found an enhanced connectivity between the LOC but not V1 and typical frontal language areas - the inferior frontal cortex (IFC). In fact, the left-lateralized LOC-IFC connectivity strength predicted blind individuals' natural Braille reading proficiency. Furthermore, an increased bidirectional information flow between the left LOC and IFC was observed during a natural Braille reading task. In particular, the task-relevant modulation of the top-down communication from left IFC to LOC was significantly stronger than that of the bottom-up communication. Altogether, our study identified a distinctive neural nexus, LOC-IFC connection, and its behavioral significance in the acquired blind, revealing the neural correlates of the crossmodal plasticity in their 'visual' cortex underlying natural Braille reading.

Body Movement and Verbal Encoding in the Congenitally Blind

1974 ◽  
Vol 39 (1) ◽  
pp. 279-293 ◽  
Author(s):  
Thomas Blass ◽  
Norbert Freedman ◽  
Irving Steingart
Keyword(s):  
Motor Activity ◽  
Verbal Fluency ◽  
Body Movement ◽  
Hand Movements ◽  
Complex Sentences ◽  
Sensory Experiences ◽  
Congenitally Blind ◽  
Continuous Body ◽  
Blind Individuals

The purpose of the study was to examine the prevalence of object- and body-focused hand movements of the congenitally blind individuals engaged in an encoding task and to determine the relation of these movements to verbal performance. Ten Ss participated in a 5-min. videotaped monologue. The video portion was coded for hand movements using Freedman's categories of analysis. The audio portion was scored for grammatical complexity according to a system developed by Steingart and Freedman. It was found that: (1) Blind Ss engaged only in body-focused movements; object-focused movements were almost completely absent. (2) Blind Ss displayed significantly greater amounts of body-focused (primarily finger-to-hand) movements than a group of sighted Ss observed in a previous study. (3) There was a correlation of .51 between finger-to-hand movements and verbal fluency and a correlation of –.53 between body-touching and verbal fluency. (4) Ss with a prevalence of finger-to-hand movements showed significantly greater language skill at encoding complex sentences which portray descriptions of patterned, interrelationships among experiences, while Ss with a predominance of continuous body touching gave a less skillful language product in this regard. The findings indicate the central role of motor activity in ongoing thought construction. They also indicate that for the blind, finger-to-hand motions contribute to the evocation of sensory experiences as a necessary pre-condition for linguistic representation.

scholarly journals “Visual” Cortices of Congenitally Blind Adults Respond to Executive Demands Authors

2018 ◽  
Author(s):  
Rita E. Loiotile ◽  
Marina Bedny
Keyword(s):  
Visual Cortex ◽  
Executive Control ◽  
Alternative Hypothesis ◽  
Human Cortex ◽  
Cortex Area ◽  
Congenitally Blind ◽  
Visual Cortices ◽  
Underlying Mechanisms ◽  
Blind Individuals

AbstractHow functionally flexible is human cortex? In congenitally blind individuals, “visual” cortices are active during auditory and tactile tasks. The cognitive role of these responses and the underlying mechanisms remain uncertain. A dominant view is that, in blindness, “visual” cortices process information from low-level auditory and somatosensory systems. An alternative hypothesis is that higher-cognitive fronto-parietal systems take over “visual” cortices. We report that, in congenitally blind individuals, right-lateralized “visual” cortex responds to executiveload in a go/no-go task. These right-lateralized occipital cortices of blind, but not sighted, individuals mirrored the executive-function pattern observed in fronto-parietal systems. In blindness, the same “visual” cortex area, at rest, also increases its synchronization with prefrontal executive control regions and decreases its synchronization with auditory and sensorimotor cortices. These results support the hypothesis of top-down fronto-parietal takeover of “visual” cortices, and suggest that human cortex is highly flexible at birth.

scholarly journals A thalamocortical pathway for fast rerouting of tactile information to occipital cortex in congenital blindness

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Franziska Müller ◽  
Guiomar Niso ◽  
Soheila Samiee ◽  
Maurice Ptito ◽  
Sylvain Baillet ◽  
...  
Keyword(s):  
Animal Studies ◽  
Tactile Stimulation ◽  
Occipital Cortex ◽  
Alpha Band ◽  
Response Latencies ◽  
Tactile Information ◽  
Congenitally Blind ◽  
Blind Individuals ◽  
Subcortical Pathway ◽  
Blind Humans

AbstractIn congenitally blind individuals, the occipital cortex responds to various nonvisual inputs. Some animal studies raise the possibility that a subcortical pathway allows fast re-routing of tactile information to the occipital cortex, but this has not been shown in humans. Here we show using magnetoencephalography (MEG) that tactile stimulation produces occipital cortex activations, starting as early as 35 ms in congenitally blind individuals, but not in blindfolded sighted controls. Given our measured thalamic response latencies of 20 ms and a mean estimated lateral geniculate nucleus to primary visual cortex transfer time of 15 ms, we claim that this early occipital response is mediated by a direct thalamo-cortical pathway. We also observed stronger directed connectivity in the alpha band range from posterior thalamus to occipital cortex in congenitally blind participants. Our results strongly suggest the contribution of a fast thalamo-cortical pathway in the cross-modal activation of the occipital cortex in congenitally blind humans.

scholarly journals Cerebral cortex activation during the Sternberg verbal working memory task

2020 ◽  
pp. 40-48
Author(s):  
I.S. Bakulin ◽  
A.H. Zabirova ◽  
P.N. Kopnin ◽  
D.O. Sinitsyn ◽  
A.G. Poydasheva ◽  
...  
Keyword(s):  
Working Memory ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Temporal Dynamics ◽  
Memory Task ◽  
Occipital Cortex ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal ◽  
Sternberg Task

Despite intensive study, the data regarding functional role of specific brain regions in the working memory processes still remain controversial. The study was aimed to determine the activation of cerebral cortex regions at different stages of the working memory task (information encoding, maintenance and retrieval). Functional magnetic resonance imaging (fMRI) with the modified Sternberg task was applied to 19 healthy volunteers. The objective of the task was to memorize and retain in memory the sequence of 7 letters with the subsequent comparison of one letter with the sequence. Activation was analyzed during three periods of the task compared to the rest period, as well as temporal dynamics of changes in BOLD signal intensity in three regions: left dorsolateral prefrontal, left posterior parietal and left occipital cortex. According to the results, significant activation of the regions in prefrontal and posterior parietal cortex was observed during all periods of the task (p < 0.05), but there were changes in its localization and lateralization. The activation pattern during the maintenance period corresponded to the fronto-parietal control network components. According to the analysis of temporal dynamics of changes in BOLD signal intensity, the most prominent activation of the dorsolateral prefrontal cortex and parietal cortex was observed in the end of the encoding period, during the maintenance period and in the beginning of the retrieval period, which confirmed the role of those areas in the working memory processes. The maximum of occipital cortex activation was observed during encoding period. The study confirmed the functional role of the dorsolateral prefrontal cortex and posterior parietal cortex in the working memory mechanisms during all stages of the Sternberg task.

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