Visual cortex activation in late-onset, Braille naive blind individuals: An fMRI study during semantic and phonological tasks with heard words

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.

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Dissociating Cortical Regions Activated by Semantic and Phonological Tasks: A fMRI Study in Blind and Sighted People

Journal of Neurophysiology ◽

10.1152/jn.00279.2003 ◽

2003 ◽

Vol 90 (3) ◽

pp. 1965-1982 ◽

Cited By ~ 110

Author(s):

H. Burton ◽

J. B. Diamond ◽

K. B. McDermott

Keyword(s):

Visual Cortex ◽

Language Processing ◽

Semantic Processing ◽

Late Onset ◽

Inferior Frontal Gyrus ◽

Imaging Study ◽

Cortical Activation ◽

Blind People ◽

Semantic Task ◽

Blind Individuals

Previous neuroimaging studies of language processing in blind individuals described cortical activation of primary (V1) and higher tier visual areas, irrespective of the age of blindness onset. Specifically, participants were given nouns and asked to generate an associated verb. These results confirmed the presence of adaptations in the visual cortex of blind people and suggested that these responses represented linguistic operations. The present functional magnetic resonance imaging study attempted to further characterize these responses as being preferential for semantic or phonological processing. Three groups of participants (sighted, earlyonset, and late-onset blind) heard lists of related words and attended to either a common meaning (semantic task) or common rhyme (phonological task) that linked the words. In all three groups, the semantic task elicited stronger activity in the left anterior inferior frontal gyrus and the phonological task evoked stronger activity bilaterally in the inferior parietal cortex and posterior aspects of the left inferior frontal gyrus. Only blind individuals showed activity in occipital, temporal, and parietal components of visual cortex. The spatial extent of visual cortex activity was greatest in early blind, who exhibited activation in all ventral and dorsal visual cortex subdivisions (V1 through MT) for both tasks. Preferential activation appeared for the semantic task. Late blind individuals exhibited responses in ventral and dorsal V1, ventral V2, VP and V8, but only for the semantic task. Our findings support prior evidence of visual cortex activity in blind people engaged in auditory language processing and suggest that this activity may be related to semantic processing.

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fMRI study on the hue selectivity of neurons in human visual cortex

Neuroscience Research ◽

10.1016/j.neures.2009.09.065 ◽

2009 ◽

Vol 65 ◽

pp. S44

Author(s):

Ichiro Kuriki ◽

Pei Sun ◽

Ken-ichi Ueno ◽

Keiji Tanaka ◽

Kang Cheng

Keyword(s):

Visual Cortex ◽

Human Visual Cortex ◽

Fmri Study

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A critical period for number-related plasticity in the visual cortex of blind individuals

Journal of Vision ◽

10.1167/17.10.644 ◽

2017 ◽

Vol 17 (10) ◽

pp. 644

Author(s):

Shipra Kanjlia ◽

Lisa Feigenson ◽

Marina Bedny

Keyword(s):

Visual Cortex ◽

Critical Period ◽

Blind Individuals

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

10.1101/449009 ◽

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.

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

Cerebral Cortex ◽

10.1093/cercor/bhy151 ◽

2018 ◽

Vol 29 (7) ◽

pp. 2859-2875 ◽

Cited By ~ 3

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.

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Psychophysiology and Imaging of Visual Cortical Functions in the Blind: A Review

Behavioural Neurology ◽

10.1155/2008/917492 ◽

2008 ◽

Vol 20 (3-4) ◽

pp. 71-81 ◽

Cited By ~ 2

Author(s):

Stephanie L. Simon-Dack ◽

P. Dennis Rodriguez ◽

Wolfgang A. Teder-Sälejärvi

Keyword(s):

Visual Cortex ◽

Transcranial Magnetic Stimulation ◽

Visual Information ◽

Magnetic Stimulation ◽

Late Onset ◽

Event Related Potentials ◽

Cortical Activation ◽

Future Research ◽

Related Potentials ◽

Visual Cortical

Imaging, transcranial magnetic stimulation, and psychophysiological recordings of the congenitally blind have confirmed functional activation of the visual cortex but have not extensively explained the functional significance of these activation patterns in detail. This review systematically examines research on the role of the visual cortex in processing spatial and non-visual information, highlighting research on individuals with early and late onset blindness. Here, we concentrate on the methods utilized in studying visual cortical activation in early blind participants, including positron emissions tomography (PET), functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and electrophysiological data, specifically event-related potentials (ERPs). This paper summarizes and discusses findings of these studies. We hypothesize how mechanisms of cortical plasticity are expressed in congenitally in comparison to adventitiously blind and short-term visually deprived sighted participants and discuss potential approaches for further investigation of these mechanisms in future research.

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A dynamic fMRI study of illusory double-flash effect on human visual cortex

Experimental Brain Research ◽

10.1007/s00221-005-0304-7 ◽

2005 ◽

Vol 172 (1) ◽

pp. 57-66 ◽

Cited By ~ 16

Author(s):

Nanyin Zhang ◽

Wei Chen

Keyword(s):

Visual Cortex ◽

Human Visual Cortex ◽

Fmri Study ◽

Double Flash

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Abnormal neural activity in partially remitted late-onset depression: An fMRI study of one-back working memory task

Psychiatry Research Neuroimaging ◽

10.1016/j.pscychresns.2012.04.010 ◽

2013 ◽

Vol 213 (2) ◽

pp. 133-141 ◽

Cited By ~ 7

Author(s):

Tien-Wen Lee ◽

Ho-Ling Liu ◽

Yau-Yau Wai ◽

Han-Jung Ko ◽

Shwu-Hua Lee

Keyword(s):

Working Memory ◽

Neural Activity ◽

Late Onset ◽

Memory Task ◽

Fmri Study

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Neuronal populations in the occipital cortex of the blind synchronize to the temporal dynamics of speech

eLife ◽

10.7554/elife.31640 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 9

Author(s):

Markus Johannes Van Ackeren ◽

Francesca M Barbero ◽

Stefania Mattioni ◽

Roberto Bottini ◽

Olivier Collignon

Keyword(s):

Visual Cortex ◽

Speech Processing ◽

Speech Intelligibility ◽

Temporal Dynamics ◽

Occipital Cortex ◽

Sensory Inputs ◽

Neuronal Populations ◽

Acoustic Fluctuations ◽

Blind Individuals ◽

Theta Range

The occipital cortex of early blind individuals (EB) activates during speech processing, challenging the notion of a hard-wired neurobiology of language. But, at what stage of speech processing do occipital regions participate in EB? Here we demonstrate that parieto-occipital regions in EB enhance their synchronization to acoustic fluctuations in human speech in the theta-range (corresponding to syllabic rate), irrespective of speech intelligibility. Crucially, enhanced synchronization to the intelligibility of speech was selectively observed in primary visual cortex in EB, suggesting that this region is at the interface between speech perception and comprehension. Moreover, EB showed overall enhanced functional connectivity between temporal and occipital cortices that are sensitive to speech intelligibility and altered directionality when compared to the sighted group. These findings suggest that the occipital cortex of the blind adopts an architecture that allows the tracking of speech material, and therefore does not fully abstract from the reorganized sensory inputs it receives.

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