Flexible cue anchoring strategies enable stable head direction coding in both sighted and blind animals

Vision plays a crucial role in instructing the brain's spatial navigation systems. However, little is known about how vision loss affects the neuronal encoding of spatial information. Here, recording from head direction (HD) cells in the anterior dorsal nucleus of the thalamus in mice, we find stable and robust HD tuning in blind animals. In contrast, placing sighted animals in darkness significantly impairs HD cell tuning. We find that blind mice use olfactory cues to maintain stable HD tuning and that prior visual experience leads to refined HD cell tuning in blind adult mice compared to congenitally blind animals. Finally, in the absence of both visual and olfactory cues, the HD attractor network remains intact but the preferred firing direction of HD cells continuously drifts over time. We thus demonstrate remarkable flexibility in how the brain uses diverse sensory information to generate a stable directional representation of space.

Naturalistic stimuli reveal a critical period in visual cortex development: Evidence from adult-onset blindness

How do life experiences impact cortical function? In people who are born blind, the “visual” cortices are recruited for nonvisual tasks such as Braille reading and sound localization (e.g., Collignon et al., 2011; Sadato et al., 1996). The mechanisms of this recruitment are not known. Do visual cortices have a latent capacity to respond to nonvisual information that is equal throughout the lifespan? Alternatively, is there a sensitive period of heightened plasticity that makes visual cortex repurposing possible during childhood? To gain insight into these questions, we leveraged naturalistic auditory stimuli to quantify and compare cross-modal responses congenitally blind (CB, n=22), adult-onset blind (vision loss >18 years-of-age, AB, n=14) and sighted (n=22) individuals. Participants listened to auditory excerpts from movies; a spoken narrative; and matched meaningless auditory stimuli (i.e., shuffled sentences, backwards speech) during fMRI scanning. These rich naturalistic stimuli made it possible to simultaneous engage a broad range of cognitive domains. We correlated the voxel-wise timecourses of different participants within each group. For all groups, all stimulus conditions induced synchrony in auditory cortex and for all groups only the narrative stimuli synchronized responses in higher-cognitive fronto-parietal and temporal regions. Inter-subject synchrony in visual cortices was high in the CB group for the movie and narrative stimuli but not for meaningless auditory controls. In contrast, visual cortex synchrony was equally low among AB and sighted blindfolded participants. Even many years of blindness in adulthood fail to enable responses to naturalistic auditory information in visual cortices of people who had sight as children. These findings suggest that cross-modal responses in visual cortex of people born blind reflect the plasticity of developing visual cortex during a sensitive period.

Reading Modality Modifies Reading Network: Insights from Neural basis of Braille in Proficient Blind Readers

The neural basis of reading is highly consistent across a variety of languages and visual scripts. An unanswered question is whether the sensory modality of symbols influences the neural basis of reading. According to the modality-invariant view, reading depends on the same neural mechanisms regardless of the sensory input modality. Consistent with this idea, previous studies find that the visual word form area (VWFA) within the ventral occipitotemporal cortex (vOTC) is active when blind individuals read Braille by touch. However, connectivity-based theories of brain function suggest that the neural entry point of written symbols (touch vs. vision) may influence the neural architecture of reading. We compared the neural basis of the visual print (sighted n=15) and tactile Braille (congenitally blind n=19) in proficient readers using analogous reading and listening tasks. Written stimuli varied in word-likeness from real words to consonant strings and non-letter shape strings. Auditory stimuli consisted of words and backward speech sounds. Consistent with prior work, vOTC was active during Braille and visual reading. However, in sighted readers, visual print elicited a posterior/anterior vOTC word-form gradient: anterior vOTC preferred larger orthographic units (words), middle vOTC preferring consonant strings, and posterior vOTC responded to shapes (i.e., lower-level physical features). No such gradient was observed in blind readers of Braille. Consistent with connectivity predictions, in blind Braille readers, posterior parietal cortices (PPC) and parieto-occipital areas were recruited to a greater degree and PPC contained word-preferring patches. Lateralization of Braille in blind readers was predicted by laterality of spoken language, as well as by reading hand. These results suggested that the neural basis of reading is influenced by symbol modality and support connectivity-based views of cortical function.

Creating Tactile Educational Materials for the Visually Impaired and Blind Students Using AI Cloud Computing

There are 24.5 million visually impaired and blind (VIB) students who have limited access to educational materials due to cost or availability. Although advancement in technology is prevalent, providing individualized learning using technology remains a challenge without the proper tools or experience. The TacPic system was developed as an online platform to create tactile educational materials (TEM) based on the image inputs of users who do not have prior experience in tactile photo development or 3D printing. The TacPic system allows the users to simply upload images to a website and uses AI cloud computing on the Amazon Web Services platform. First, it segments and labels the images. Then, the text label is converted into braille words. Subsequently, surface rendering and consolidation of the image and text is performed, before it is converted into a single file that is ready for 3D printing. Currently, the types of TEM that can be created are tactile flashcards, tactile maps, and tactile peg puzzles, which can be developed within a few hours. This is in contrast to a development period of weeks using traditional methods. Furthermore, the tactile educational materials were tested by two VIB teachers and six VIB students. It was found that those who are congenitally blind need more time to identify the object and rely more on the braille labels compared to students who became blind at a later age. Teachers also suggested producing TEM that use simpler images, and TEM that are suitable for both sighted and VIB students. In conclusion, the researchers successfully developed a platform that allows more educators or parents to develop personalized and individualized TEM. In the future, further optimization of the algorithms to improve segmentation and the inclusion of other features, such as color, could be undertaken. Finally, new printing materials and methods are needed to improve printing efficiency.

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

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.

Consumers with vulnerabilities: in-store satisfaction of visually impaired and legally blind

Purpose The purpose of this paper, focusing on the visually impaired and legally blind consumer, is to explore the relationship between the perceived consumer vulnerability on customer satisfaction and the effect of satisfaction on the intention of repurchase and recommendation as the determinants of store loyalty in an apparel store context. Design/methodology/approach A survey was conducted on 216 visually impaired and legally blind consumers in the province of Manisa, Turkey, concerning their apparel shopping store experiences to examine how the perceived vulnerability influences visually impaired and legally blind consumers’ satisfaction, recommendation and repurchase intentions. The data were analyzed using structural equation modeling. Findings The results of the study revealed that as the visually impaired and legally blind consumers perceive themselves more vulnerable, they become more satisfied with the store, and that the more they are satisfied with the store, the more their intention to recommend that store and purchase intention from that store increases. However, the authors’ investigation showed no significant differences between the consumers who were born blind and who became blind later in their life. Originality/value The paper contributes to the literature by extending the understanding of visually impaired and legally blind consumers’ perceived vulnerability in the brick-and-mortar stores and demonstrates how it is related to satisfaction as a major driver of post-purchase intentions like recommendation and repurchase. It also exhibits the fact that blind consumers – both congenitally blind and subsequently blind – cope with this vulnerability through their own solutions to go on their lives, and they do not perceive themselves as vulnerable, as it is perceived by the able-bodied.

The effect of congenital blindness on resting-state functional connectivity revisited

Lower resting-state functional connectivity (RSFC) between ‘visual’ and non-‘visual’ neural circuits has been reported as a hallmark of congenital blindness. In sighted individuals, RSFC between visual and non-visual brain regions has been shown to increase during rest with eyes closed relative to rest with eyes open. To determine the role of visual experience on the modulation of RSFC by resting state condition—as well as to evaluate the effect of resting state condition on group differences in RSFC—, we compared RSFC between visual and somatosensory/auditory regions in congenitally blind individuals (n = 9) and sighted participants (n = 9) during eyes open and eyes closed conditions. In the sighted group, we replicated the increase of RSFC between visual and non-visual areas during rest with eyes closed relative to rest with eyes open. This was not the case in the congenitally blind group, resulting in a lower RSFC between ‘visual’ and non-‘visual’ circuits relative to sighted controls only in the eyes closed condition. These results indicate that visual experience is necessary for the modulation of RSFC by resting state condition and highlight the importance of considering whether sighted controls should be tested with eyes open or closed in studies of functional brain reorganization as a consequence of blindness.

Typical resting state activity of the brain requires visual input during an early sensitive period

Sensory deprivation, following a total loss of one sensory modality e.g. vision, has been demonstrated to result in intra- and cross-modal plasticity. It is yet not known to which extent intra- and cross-modal plasticity as a consequence of blindness reverse if sight is restored. Here, we used functional magnetic resonance imaging to acquire blood oxygen level dependent (BOLD) resting state activity during an eyes open and an eyes closed state in congenital cataract-reversal individuals, developmental cataract-reversal individuals, congenitally permanently blind individuals and sighted controls. The amplitude of low frequency fluctuations (ALFF) of the BOLD signal - a neural marker of spontaneous brain activity during rest - was analyzed. As has been shown before, in normally sighted controls we observed an increase in ALFF during rest with the eyes open compared to rest with eyes closed in visual association areas and in parietal cortex but a decrease in auditory and sensorimotor regions. In congenital cataract-reversal individuals, we found an increase of the amplitude of slow BOLD fluctuations in visual cortex during rest with eyes open compared to rest with eyes closed too but this increase was larger in amplitude than in normally sighted controls. At the same time, congenital cataract-reversal individuals lagged a similar increase in parietal regions and did not show the typical decrease of ALFF in auditory and sensorimotor cortex. Congenitally blind individuals displayed an overall higher amplitude in slow BOLD fluctuations in visual cortex compared to sighted individuals and compared to congenital cataract-reversal individuals in the eyes closed condition. Higher ALFF in visual cortex of congenital cataract-reversal individuals than in normally sighted controls during eyes open might indicate an altered excitatory-inhibitory balance of visual neural circuits. By contrast, the lower parietal increase and the missing downregulation in auditory and sensorimotor regions suggest a reduced influence of the visual system on multisensory and the remaining sensory systems after restoring sight in congenitally blind individuals. These results demonstrate a crucial dependence of multisensory neural networks on visual experience during a sensitive phase in human brain development.