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.

Enhanced Odorant Localization Abilities in Congenitally Blind but not in Late-Blind Individuals

Although often considered a nondominant sense for spatial perception, chemosensory perception can be used to localize the source of an event and potentially help us navigate through our environment. Would blind people who lack the dominant spatial sense—vision—develop enhanced spatial chemosensation or suffer from the lack of visual calibration on spatial chemosensory perception? To investigate this question, we tested odorant localization abilities across nostrils in blind people compared to sighted controls and if the time of vision loss onset modulates those abilities. We observed that congenitally blind individuals (10 subjects) outperformed sighted (20 subjects) and late-blind subjects (10 subjects) in a birhinal localization task using mixed olfactory-trigeminal stimuli. This advantage in congenitally blind people was selective to olfactory localization but not observed for odorant detection or identification. We, therefore, showed that congenital blindness but not blindness acquired late in life is linked to enhanced localization of chemosensory stimuli across nostrils, most probably of the trigeminal component. In addition to previous studies highlighting enhanced localization abilities in auditory and tactile modalities, our current results extend such enhanced abilities to chemosensory localization.

3D Pen Tactile Pictures Generated by Individuals with Visual Impairments

Introduction: Individuals with visual impairments acquire information about objects through touch and by use of auxiliary tactile pictures. The current study introduced a new three-dimensional (3D) printing pen technology as a research tool to allow individuals with visual impairments to convert tactile experiences to convex tactile pictures. Methods: Participants with visual impairments used a 3D pen to draw pictures of daily necessities. The actions and time related to the entire drawing activity were recorded on video. Results: We noted three behaviors during the use of 3D pen: drawing, touching the trace lines, and finding location points. The object-depiction angle, component-completeness description, and drawing-line presentation differed between subjects with congenital and those with acquired blindness. Discussion: Individuals with congenital blindness depicted objects mainly from an operational angle, and those with acquired blindness from the angle of the object when laid flat. When the components of an object were relatively complex, the subjects with congenital blindness only drew local features in contact with their bodies and with continuous line segments, and those with acquired blindness used discontinuous line segments. Participants were satisfied that the 3D printing pen could touch the drawing path in time and that they could use the “piling” feature to create positioning marks or planar expressions. Implications for practitioners: Students can be instructed to use 3D pens to draw (lines, planes, and objects) to enhance the communication between teachers and students and improve teaching efficiency. Regarding the design of tactile pictures, the parts that come in contact with the body during object use can be considered the reference features of the pictures. For large pictures, attention should be paid to the size ratio between the outline and components. For small pictures, one should consider how the operational feature details should be shown at approximately the original size.

Normal Olfactory Functional Connectivity Despite Lifelong Absence of Olfactory Experiences

Congenital blindness is associated with atypical morphology and functional connectivity within and from visual cortical regions; changes that are hypothesized to originate from a lifelong absence of visual input and could be regarded as a general (re) organization principle of sensory cortices. Challenging this is the fact that individuals with congenital anosmia (lifelong olfactory sensory loss) display little to no morphological changes in the primary olfactory cortex. To determine whether olfactory input from birth is essential to establish and maintain normal functional connectivity in olfactory processing regions, akin to the visual system, we assessed differences in functional connectivity within the olfactory cortex between individuals with congenital anosmia (n = 33) and matched controls (n = 33). Specifically, we assessed differences in connectivity between core olfactory processing regions as well as differences in regional homogeneity and homotopic connectivity within the primary olfactory cortex. In contrast to congenital blindness, none of the analyses indicated atypical connectivity in individuals with congenital anosmia. In fact, post-hoc Bayesian analysis provided support for an absence of group differences. These results suggest that a lifelong absence of olfactory experience has a limited impact on the functional connectivity in the olfactory cortex, a finding that indicates a clear difference between sensory modalities in how sensory cortical regions develop.