scholarly journals Regions of visual cortex responding to tactile stimulation in an individual with longstanding low vision are not causally involved in tactile processing performance

2021 ◽  
Author(s):  
Edward H Silson ◽  
Andre D Gouws ◽  
Gordon E Legge ◽  
Antony B Morland
Keyword(s):  
Visual Cortex ◽  
Visual Processing ◽  
Tactile Stimulation ◽  
Low Vision ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Somatosensory Cortices ◽  
Congenitally Blind ◽  
Causal Nature ◽  
Blind Individuals ◽  
Stimulation Of

Braille reading and other tactile discrimination tasks recruit the visual cortex of both blind and normally sighted individuals undergoing short-term visual deprivation. Prior functional magnetic resonance imaging (fMRI) work in patient S, a visually impaired adult with the rare ability to read both highly magnified print visually and Braille by touch, found that foveal representations of S's visual cortex were recruited during tactile perception, whereas peripheral regions were recruited during visual perception. Here, we test the causal nature of tactile responses in the visual cortex of S by combining tactile and visual psychophysics with repetitive transcranial magnetic stimulation (rTMS). First, we replicate this prior fMRI work in S. Second, we demonstrate that transient disruption of S's foveal visual cortex has no measurable impact on S's tactile processing performance compared to that of healthy controls - a pattern not predicted by the fMRI results. Third, stimulation of foveal visual cortex maximally disrupted visual processing performance in both S and controls, suggesting the possibility of preserved visual function within S's foveal cortex. Finally, stimulation of somatosensory cortex induced the expected disruption to tactile processing performance in both S and controls. These data suggest that tactile responses in S's foveal representation reflect unmasking of latent connections between visual and somatosensory cortices and not behaviourally relevant cross-modal plasticity. Unlike studies in congenitally blind individuals, it is possible that the absence of complete visual loss in S has limited the degree of causally impactful cross-modal reorganisation.

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 Mental Imagery Follows Similar Cortical Reorganization as Perception: Intra-Modal and Cross-Modal Plasticity in Congenitally Blind

2018 ◽  
Vol 29 (7) ◽  
pp. 2859-2875 ◽  
Author(s):  
A W de Borst ◽  
B de Gelder
Keyword(s):  
Visual Cortex ◽  
Mental Imagery ◽  
Cortical Plasticity ◽  
Tactile Perception ◽  
Cortical Reorganization ◽  
Area V4 ◽  
Congenitally Blind ◽  
Early Visual Cortex ◽  
Blind Individuals ◽  
Discriminative Patterns

Abstract Cortical plasticity in congenitally blind individuals leads to cross-modal activation of the visual cortex and may lead to superior perceptual processing in the intact sensory domains. Although mental imagery is often defined as a quasi-perceptual experience, it is unknown whether it follows similar cortical reorganization as perception in blind individuals. In this study, we show that auditory versus tactile perception evokes similar intra-modal discriminative patterns in congenitally blind compared with sighted participants. These results indicate that cortical plasticity following visual deprivation does not influence broad intra-modal organization of auditory and tactile perception as measured by our task. Furthermore, not only the blind, but also the sighted participants showed cross-modal discriminative patterns for perception modality in the visual cortex. During mental imagery, both groups showed similar decoding accuracies for imagery modality in the intra-modal primary sensory cortices. However, no cross-modal discriminative information for imagery modality was found in early visual cortex of blind participants, in contrast to the sighted participants. We did find evidence of cross-modal activation of higher visual areas in blind participants, including the representation of specific-imagined auditory features in visual area V4.

scholarly journals Development of visual category selectivity in ventral visual cortex does not require visual experience

2017 ◽  
Vol 114 (22) ◽  
pp. E4501-E4510 ◽  
Author(s):  
Job van den Hurk ◽  
Marc Van Baelen ◽  
Hans P. Op de Beeck
Keyword(s):  
Visual Cortex ◽  
Auditory Cortex ◽  
Visual Processing ◽  
Visual Experience ◽  
Temporal Cortex ◽  
Primary Auditory Cortex ◽  
Extrastriate Cortex ◽  
Striking Similarity ◽  
Visual Responses ◽  
Blind Individuals

To what extent does functional brain organization rely on sensory input? Here, we show that for the penultimate visual-processing region, ventral-temporal cortex (VTC), visual experience is not the origin of its fundamental organizational property, category selectivity. In the fMRI study reported here, we presented 14 congenitally blind participants with face-, body-, scene-, and object-related natural sounds and presented 20 healthy controls with both auditory and visual stimuli from these categories. Using macroanatomical alignment, response mapping, and surface-based multivoxel pattern analysis, we demonstrated that VTC in blind individuals shows robust discriminatory responses elicited by the four categories and that these patterns of activity in blind subjects could successfully predict the visual categories in sighted controls. These findings were confirmed in a subset of blind participants born without eyes and thus deprived from all light perception since conception. The sounds also could be decoded in primary visual and primary auditory cortex, but these regions did not sustain generalization across modalities. Surprisingly, although not as strong as visual responses, selectivity for auditory stimulation in visual cortex was stronger in blind individuals than in controls. The opposite was observed in primary auditory cortex. Overall, we demonstrated a striking similarity in the cortical response layout of VTC in blind individuals and sighted controls, demonstrating that the overall category-selective map in extrastriate cortex develops independently from visual experience.

scholarly journals Naturalistic audio-movies reveal common spatial organization across “visual” cortices of different blind individuals

2021 ◽  
Author(s):  
Elizabeth Musz ◽  
Rita Loiotile ◽  
Janice Chen ◽  
Marina Bedny
Keyword(s):  
Visual Cortex ◽  
Visual Information ◽  
Spatial Organization ◽  
Activity Patterns ◽  
Auditory Stimuli ◽  
Spatial Activity ◽  
Pattern Similarity ◽  
Congenitally Blind ◽  
Visual Cortices ◽  
Blind Individuals

AbstractOccipital cortices of different sighted people contain analogous maps of visual information (e.g., foveal vs. peripheral space). In congenital blindness, “visual” cortices enhance responses to nonvisual stimuli. Do deafferented visual cortices of different blind people represent common informational maps? We leverage a naturalistic stimulus paradigm and inter-subject pattern similarity analysis to address this question. Blindfolded sighted (S, n=22) and congenitally blind (CB, n=22) participants listened to three auditory excerpts from movies; a naturalistic spoken narrative; and matched degraded auditory stimuli (i.e., shuffled sentences and backwards speech) while undergoing fMRI scanning. In a parcel-based whole brain analysis, we measured the spatial activity patterns evoked by each unique, ten-second segment of each auditory clip. We then compared each subject’s spatial pattern to that of all other subjects in the same group (CB or S) within and across segments. In both blind and sighted groups, segments of meaningful auditory stimuli produced distinctive patterns of activity that were shared across individuals. Crucially, only in the CB group, this segment-specific, cross-subject pattern similarity effect emerged in visual cortex, but only for meaningful naturalistic stimuli and not backwards speech. These results suggest that spatial activity patterns within deafferented visual cortices encode meaningful, segment-level information contained in naturalistic auditory stimuli, and that these representations are spatially organized in a similar fashion across blind individuals.Significance StatementRecent neuroimaging studies show that the so-called “visual” cortices activate during non-visual tasks in people who are born blind. Do the visual cortices of people who are born blind develop similar representational maps? While congenitally blind individuals listened to naturalistic auditory stimuli (i.e., sound clips from movies), distinct timepoints within each stimulus elicited unique spatial activity patterns in visual cortex, and these patterns were shared across different people. These findings suggest that in blindness, the visual cortices encode meaningful information embedded in naturalistic auditory signals in a spatially distributed manner, and that a common representational map can emerge in visual cortex independent of visual experience.

scholarly journals Spoken language comprehension activates the primary visual cortex

2020 ◽  
Author(s):  
Anna Seydell-Greenwald ◽  
Xiaoying Wang ◽  
Elissa Newport ◽  
Yanchao Bi ◽  
Ella Striem-Amit
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Plasticity ◽  
Spoken Language ◽  
Functional Change ◽  
Congenitally Blind ◽  
Intact Brain ◽  
Speech Control ◽  
Language Activation ◽  
Blind Individuals

AbstractCurrent accounts of neural plasticity emphasize the role of connectivity and conserved function in determining a neural tissue’s functional role even after atypical early experiences. However, in apparent conflict with this view, studies of congenitally blind individuals have also suggested that language activates primary visual cortex, with no evidence of major changes in anatomical connectivity that could explain this apparent drastic functional change in what is typically a low-level visual area. To reconcile what appears to be unprecedented functional reorganization in V1 with known accounts of plasticity limitations, we tested whether primary visual cortex also responds to spoken language in sighted individuals. We found that primary visual cortex was activated by comprehensible speech as compared to a reversed speech control task, in a left-lateralized and focal manner, in sighted individuals. Importantly, left V1 activation was also significant and comparable for abstract and concrete words, precluding a visual imagery account of such activation. Together these findings suggest that primary visual cortex responds to verbal information in the typically developed brain, potentially to predict visual input. This capability might be the basis for the strong V1 language activation observed in people born blind, re-affirming the notion that plasticity is guided by pre-existing connectivity and abilities in the intact brain.

scholarly journals Adaptive Changes in Early and Late Blind: A fMRI Study of Braille Reading

2002 ◽  
Vol 87 (1) ◽  
pp. 589-607 ◽  
Author(s):  
H. Burton ◽  
A. Z. Snyder ◽  
T. E. Conturo ◽  
E. Akbudak ◽  
J. M. Ollinger ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Language Processing ◽  
Tactile Stimulation ◽  
Primary Motor Cortex ◽  
Late Onset ◽  
Inferior Frontal Gyrus ◽  
Temporal Cortex ◽  
Somatosensory System ◽  
Occipital Cortex ◽  
Blind Individuals

Braille reading depends on remarkable adaptations that connect the somatosensory system to language. We hypothesized that the pattern of cortical activations in blind individuals reading Braille would reflect these adaptations. Activations in visual (occipital-temporal), frontal-language, and somatosensory cortex in blind individuals reading Braille were examined for evidence of differences relative to previously reported studies of sighted subjects reading print or receiving tactile stimulation. Nine congenitally blind and seven late-onset blind subjects were studied with fMRI as they covertly performed verb generation in response to reading Braille embossed nouns. The control task was reading the nonlexical Braille string “######”. This study emphasized image analysis in individual subjects rather than pooled data. Group differences were examined by comparing magnitudes and spatial extent of activated regions first determined to be significant using the general linear model. The major adaptive change was robust activation of visual cortex despite the complete absence of vision in all subjects. This included foci in peri-calcarine, lingual, cuneus and fusiform cortex, and in the lateral and superior occipital gyri encompassing primary (V1), secondary (V2), and higher tier (VP, V4v, LO and possibly V3A) visual areas previously identified in sighted subjects. Subjects who never had vision differed from late blind subjects in showing even greater activity in occipital-temporal cortex, provisionally corresponding to V5/MT and V8. In addition, the early blind had stronger activation of occipital cortex located contralateral to the hand used for reading Braille. Responses in frontal and parietal cortex were nearly identical in both subject groups. There was no evidence of modifications in frontal cortex language areas (inferior frontal gyrus and dorsolateral prefrontal cortex). Surprisingly, there was also no evidence of an adaptive expansion of the somatosensory or primary motor cortex dedicated to the Braille reading finger(s). Lack of evidence for an expected enlargement of the somatosensory representation may have resulted from balanced tactile stimulation and gross motor demands during Braille reading of nouns and the control fields. Extensive engagement of visual cortex without vision is discussed in reference to the special demands of Braille reading. It is argued that these responses may represent critical language processing mechanisms normally present in visual cortex.

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.

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