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 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 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.

scholarly journals Differential cortical microstructural maturation in the preterm human brain with diffusion kurtosis and tensor imaging

2019 ◽  
Vol 116 (10) ◽  
pp. 4681-4688 ◽  
Author(s):  
Minhui Ouyang ◽  
Tina Jeon ◽  
Aristeidis Sotiras ◽  
Qinmu Peng ◽  
Virendra Mishra ◽  
...  
Keyword(s):  
Human Brain ◽  
Diffusion Tensor ◽  
Cortical Plate ◽  
Diffusion Kurtosis Imaging ◽  
Third Trimester ◽  
Microstructural Changes ◽  
The Third ◽  
Cortical Regions ◽  
Non Gaussian ◽  
Diffusion Kurtosis

During the third trimester, the human brain undergoes rapid cellular and molecular processes that reshape the structural architecture of the cerebral cortex. Knowledge of cortical differentiation obtained predominantly from histological studies is limited in localized and small cortical regions. How cortical microstructure is differentiated across cortical regions in this critical period is unknown. In this study, the cortical microstructural architecture across the entire cortex was delineated with non-Gaussian diffusion kurtosis imaging as well as conventional diffusion tensor imaging of 89 preterm neonates aged 31–42 postmenstrual weeks. The temporal changes of cortical mean kurtosis (MK) or fractional anisotropy (FA) were heterogeneous across the cortical regions. Cortical MK decreases were observed throughout the studied age period, while cortical FA decrease reached its plateau around 37 weeks. More rapid decreases in MK were found in the primary visual region, while faster FA declines were observed in the prefrontal cortex. We found that distinctive cortical microstructural changes were coupled with microstructural maturation of associated white matter tracts. Both cortical MK and FA measurements predicted the postmenstrual age of preterm infants accurately. This study revealed a differential 4D spatiotemporal cytoarchitectural signature inferred by non-Gaussian diffusion barriers inside the cortical plate during the third trimester. The cytoarchitectural processes, including dendritic arborization and neuronal density decreases, were inferred by regional cortical FA and MK measurements. The presented findings suggest that cortical MK and FA measurements could be used as effective imaging markers for cortical microstructural changes in typical and potentially atypical brain development.

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 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 Transcranial magnetic stimulation of the occipital cortex interferes with foot movements in blind individuals

2021 ◽  
Author(s):  
Tsuyoshi Ikegami ◽  
Masaya Hirashima ◽  
Eiichi Naito ◽  
Satoshi Hirose
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Motor Function ◽  
Cognitive Functions ◽  
Magnetic Stimulation ◽  
Visual Loss ◽  
Occipital Cortex ◽  
Congenitally Blind ◽  
Blind Individuals ◽  
Motor Production

Plasticity after visual loss is a remarkable characteristic of the brain. Previous studies in blind individuals have shown that the occipital cortex, which corresponds to the visual cortex in sighted individuals, can be reorganized and repurposed for nonvisual perception and cognitive functions. To our knowledge, however, no studies have directly examined its involvement in motor production. Here we show that a rhythmic foot movement performed by acquired blind participants can be disrupted by transcranial magnetic stimulation (TMS) to their primary and secondary visual cortex (V1/V2). Variability of this foot movement increased when we applied TMS to the acquired blind participants. This effect of TMS was absent for both sighted and congenitally blind participants. These results suggest that the visual cortex of blind individuals is involved in motor production, but its involvement requires prior visual experience. Our finding indicates that functional repurposing of the visual cortex may not be restricted to perception and cognitive functions, but also extended to motor function. Motor function may emerge in the visual cortex of blind individuals as a consequence of the reorganization of the visuomotor network, which has been developed before visual loss.

scholarly journals Reduced Left Lateralization of Language in Congenitally Blind Individuals

2017 ◽  
Vol 29 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Connor Lane ◽  
Shipra Kanjlia ◽  
Hilary Richardson ◽  
Anne Fulton ◽  
Akira Omaki ◽  
...  
Keyword(s):  
Language Processing ◽  
Reading Ability ◽  
Sentence Comprehension ◽  
Memory Task ◽  
Developmental Factors ◽  
Two Samples ◽  
Congenitally Blind ◽  
Cortical Regions ◽  
Blind Individuals ◽  
Language Network

Language processing depends on a left-lateralized network of frontotemporal cortical regions. This network is remarkably consistent across individuals and cultures. However, there is also evidence that developmental factors, such as delayed exposure to language, can modify this network. Recently, it has been found that, in congenitally blind individuals, the typical frontotemporal language network expands to include parts of “visual” cortices. Here, we report that blindness is also associated with reduced left lateralization in frontotemporal language areas. We analyzed fMRI data from two samples of congenitally blind adults (n = 19 and n = 13) and one sample of congenitally blind children (n = 20). Laterality indices were computed for sentence comprehension relative to three different control conditions: solving math equations (Experiment 1), a memory task with nonwords (Experiment 2), and a “does this come next?” task with music (Experiment 3). Across experiments and participant samples, the frontotemporal language network was less left-lateralized in congenitally blind than in sighted individuals. Reduction in left lateralization was not related to Braille reading ability or amount of occipital plasticity. Notably, we observed a positive correlation between the lateralization of frontotemporal cortex and that of language-responsive occipital areas in blind individuals. Blind individuals with right-lateralized language responses in frontotemporal cortices also had right-lateralized occipital responses to language. Together, these results reveal a modified neurobiology of language in blindness. Our findings suggest that, despite its usual consistency across people, the neurobiology of language can be modified by nonlinguistic experiences.

scholarly journals Neuroplasticity: Insights from Patients Harboring Gliomas

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Nathan W. Kong ◽  
William R. Gibb ◽  
Matthew C. Tate
Keyword(s):  
Diffusion Tensor ◽  
Current Knowledge ◽  
Human Subjects ◽  
Functional Anatomy ◽  
Neurologic Injury ◽  
Adaptive Mechanisms ◽  
Plastic Potential ◽  
Cortical Regions ◽  
The Brain

Neuroplasticity is the ability of the brain to reorganize itself during normal development and in response to illness. Recent advances in neuroimaging and direct cortical stimulation in human subjects have given neuroscientists a window into the timing and functional anatomy of brain networks underlying this dynamic process. This review will discuss the current knowledge about the mechanisms underlying neuroplasticity, with a particular emphasis on reorganization following CNS pathology. First, traditional mechanisms of neuroplasticity, most relevant to learning and memory, will be addressed, followed by a review of adaptive mechanisms in response to pathology, particularly the recruitment of perilesional cortical regions and unmasking of latent connections. Next, we discuss the utility and limitations of various investigative techniques, such as direct electrocortical stimulation (DES), functional magnetic resonance imaging (fMRI), corticocortical evoked potential (CCEP), and diffusion tensor imaging (DTI). Finally, the clinical utility of these results will be highlighted as well as possible future studies aimed at better understanding of the plastic potential of the brain with the ultimate goal of improving quality of life for patients with neurologic injury.

Sign in / Sign up

Export Citation Format

Share Document