Mechanisms of Cross-Modal Plasticity in Early-Blind Subjects

Lewis, Lindsay B.; Sàenz, Melissa; Fine, Ione

doi:10.1152/jn.00983.2009

Cited by 50 publications

(38 citation statements)

References 95 publications

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“…However these responses have tended to be smaller than those found in the studies described above (Hagen et al 2002; Blake et al 2004; Beauchamp et al 2007; van Kemenade et al 2014). Our finding of a weak suppressive effect of tactile stimulation in the no task condition has also previously been observed (Ricciardi et al 2007; Lewis et al 2010). (Interestingly, a variety of studies show suppression of hMT+ when subjects attend to an auditory motion stimulus Lewis et al 2000; Strnad et al 2013; Jiang et al 2014).…”

Section: Discussionsupporting

confidence: 90%

“…However a variety of studies have explicitly looked for, but failed to find, evidence of auditory motion responses in hMT+ (Lewis et al 2000; Saenz et al 2008; Bedny et al 2010; Lewis et al 2010; Alink et al 2012; Jiang et al 2014). Indeed, in an analysis closely analogous to that of Figure 5 it has been previously been shown by Saenz et al (Saenz et al 2008) that spurious auditory motion responses in hMT were elicited as a result of using group averaging methods to define hMT+.…”

Section: Discussionmentioning

confidence: 99%

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Re-examining overlap between tactile and visual motion responses within hMT + and STS

2015

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Here we examine overlap between tactile and visual motion BOLD responses within the human MT+ complex. Although several studies have reported tactile responses overlapping with hMT+, many used group average analyses, leaving it unclear whether these responses were restricted to sub-regions of hMT+. Moreover, previous studies either employed a tactile task or passive stimulation, leaving it unclear whether or not tactile responses in hMT+ are simply the consequence of visual imagery. Here we carried out a replication of one of the classic papers finding tactile responses in hMT+ (Hagen et al. 2002). We mapped MT and MST in individual subjects using visual field localizers. We then examined responses to tactile motion on the arm, either presented passively or in the presence of a visual task performed at fixation designed to minimize visualization of the concurrent tactile stimulation. To our surprise, without a visual task, we found only weak tactile motion responses in MT (6% of voxels showing tactile responses) and MST (2% of voxels). With an unrelated visual task designed to withdraw attention from the tactile modality, responses in MST reduced to almost nothing (<1% regions). Consistent with previous results, we did observe tactile responses in STS regions superior and anterior to hMT+. Despite the lack of individual overlap, group averaged responses produced strong spurious overlap between tactile and visual motion responses within hMT+ that resembled those observed in previous studies. The weak nature of tactile responses in hMT+ (and their abolition by withdrawal of attention) suggests that hMT+ may not serve as a supramodal motion processing module.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Re-examining overlap between tactile and visual motion responses within hMT + and STS

2015

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“…It has been shown that the process of synaptic pruning, which typically removes about 40% of the synaptic connections of visual cortex in early life (41), is limited in the case of early sensory deprivation. A decreased level of pruning might, at least in part, underlie the auditory-to-visual cross-modal plasticity in the early blind (42)(43)(44)(45): the absence of visual input during early development allows the synaptic connections to strengthen in blind individuals (46). This cross-modal plasticity predicts a stronger response in visual cortex of blind persons when auditory stimuli are processed and perhaps could explain why we observed a stronger selectivity for auditory stimuli in VTC of the congenitally blind participants.…”

Section: Discussionmentioning

confidence: 76%

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

Hurk

Baelen

Beeck

2017

Proc. Natl. Acad. Sci. U.S.A.

125

103

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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.ategory selectivity in human and primate visual cortex is a striking example of how the brain encodes the outer world. Mostly found on the lateral and ventral parts of the temporal lobe, several distinct macroscopic brain regions are known to have a preference for a particular category of visual objects, including faces [fusiform face area, occipital face area (1)], body parts [extrastriate body area (2), fusiform body area (3)], artificial objects [lateral occipital complex (4)], and scenes [parahippocampal place area (5)]. The exact computational mechanisms that drive these regions are still largely unknown: Do these regions operate as distinct functional modules (1, 6), or is category selectivity fully distributed across ventral-temporal cortex (VTC) (7), ora combination of both-do category-selective regions reflect peaks in a broad tuning map for visual object features (8)?A prominent question is whether this functional architecture develops independently of visual input or relies on visual experience during early infancy and the following years. As an example of the latter, a key hypothesis indicates that the global functional organization of VTC starts out as a protomap with a retinotopic layout (9-11). Through visual experience, regions within this protomap develop selectivity for the visual categories that often appear in the retinotopic region that is represented. According to this perspective, because faces most likely appear...

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“…Several studies have reported that the occipital cortex of CB responds quite indifferently to a variety of cognitive tasks, suggesting that some common factors (i.e., attentional) rather than specific cognitive processes may contribute to the unselective occipital activity observed in this population (5)(6)(7)(8). In contrast, other studies do suggest that distinct regions of the visually deprived occipital cortex may show functional specialization that is to some extent comparable to what is known in SI (9).…”

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confidence: 89%

Functional specialization for auditory–spatial processing in the occipital cortex of congenitally blind humans

Collignon

Vandewalle

Voss

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

293

243

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The study of the congenitally blind (CB) represents a unique opportunity to explore experience-dependant plasticity in a sensory region deprived of its natural inputs since birth. Although several studies have shown occipital regions of CB to be involved in nonvisual processing, whether the functional organization of the visual cortex observed in sighted individuals (SI) is maintained in the rewired occipital regions of the blind has only been recently investigated. In the present functional MRI study, we compared the brain activity of CB and SI processing either the spatial or the pitch properties of sounds carrying information in both domains (i.e., the same sounds were used in both tasks), using an adaptive procedure specifically designed to adjust for performance level. In addition to showing a substantial recruitment of the occipital cortex for sound processing in CB, we also demonstrate that auditory-spatial processing mainly recruits the right cuneus and the right middle occipital gyrus, two regions of the dorsal occipital stream known to be involved in visuospatial/motion processing in SI. Moreover, functional connectivity analyses revealed that these reorganized occipital regions are part of an extensive brain network including regions known to underlie audiovisual spatial abilities (i.e., intraparietal sulcus, superior frontal gyrus). We conclude that some regions of the right dorsal occipital stream do not require visual experience to develop a specialization for the processing of spatial information and to be functionally integrated in a preexisting brain network dedicated to this ability.blindness | cross-modal plasticity | ventral-dorsal auditory streams | modularity W hen the brain is deprived of its natural sensory inputs, it can rewire itself, showing an impressive range of plastic changes (1). Early visual deprivation thus provides an exceptional model to explore the role of sensory experience in shaping the functional architecture of the brain. Based on a number of studies comparing brain activity of congenitally blind (CB) and sighted individuals (SI), the current prevailing view is that visual deafferentation results in a reliable recruitment of the occipital cortex for nonvisual sensory processing to compensate for the challenging condition that is visual deprivation (2).Although such findings highlight the brain's remarkable ability to rewire its components, questions remain about the functional organization of the occipital cortex in CB. An important characteristic of the visual cortex in SI is domain specialization wherein specific functional activity has been found in anatomically identifiable regions (3, 4). Our main question was, therefore: does the occipital cortex of CB process the colonizing nonvisual stimuli in a global manner or does it do so using some functional modularity similar to what is observed in SI, with precise regions involved in specific cognitive functions?Several studies have reported that the occipital cortex of CB responds quite indifferently to a variety of cogn...

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Mechanisms of Cross-Modal Plasticity in Early-Blind Subjects

Cited by 50 publications

References 95 publications

Re-examining overlap between tactile and visual motion responses within hMT + and STS

Re-examining overlap between tactile and visual motion responses within hMT + and STS

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

Functional specialization for auditory–spatial processing in the occipital cortex of congenitally blind humans

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