Late Blind Participants Research Articles

Adults' spatial scaling of tactile maps: Insights from studying sighted, early and late blind individuals.

The current study investigated spatial scaling of tactile maps among blind adults and blindfolded sighted controls. We were specifically interested in identifying spatial scaling strategies as well as effects of different scaling directions (up versus down) on participants' performance. To this aim, we asked late blind participants (with visual memory, Experiment 1) and early blind participants (without visual memory, Experiment 2) as well as sighted blindfolded controls to encode a map including a target and to place a response disc at the same spot on an empty, constant-sized referent space. Maps had five different sizes resulting in five scaling factors (1:3, 1:2, 1:1, 2:1, 3:1), allowing to investigate different scaling directions (up and down) in a single, comprehensive design. Accuracy and speed of learning about the target location as well as responding served as dependent variables. We hypothesized that participants who can use visual mental representations (i.e., late blind and blindfolded sighted participants) may adopt mental transformation scaling strategies. However, our results did not support this hypothesis. At the same time, we predicted the usage of relative distance scaling strategies in early blind participants, which was supported by our findings. Moreover, our results suggested that tactile maps can be scaled as accurately and even faster by blind participants than by sighted participants. Furthermore, irrespective of the visual status, participants of each visual status group gravitated their responses towards the center of the space. Overall, it seems that a lack of visual imagery does not impair early blind adults' spatial scaling ability but causes them to use a different strategy than sighted and late blind individuals.

Blindness influences emotional authenticity perception in voices: Behavioral and ERP evidence

The ability to distinguish spontaneous from volitional emotional expressions is an important social skill. How do blind individuals perceive emotional authenticity? Unlike sighted individuals, they cannot rely on facial and body language cues, relying instead on vocal cues alone. Here, we combined behavioral and ERP measures to investigate authenticity perception in laughter and crying in individuals with early- or late-blindness onset. Early-blind, late-blind, and sighted control participants (n = 17 per group, N = 51) completed authenticity and emotion discrimination tasks while EEG data were recorded. The stimuli consisted of laughs and cries that were either spontaneous or volitional. The ERP analysis focused on the N1, P2, and late positive potential (LPP). Behaviorally, early-blind participants showed intact authenticity perception, but late-blind participants performed worse than controls. There were no group differences in the emotion discrimination task. In brain responses, all groups were sensitive to laughter authenticity at the P2 stage, and to crying authenticity at the early LPP stage. Nevertheless, only early-blind participants were sensitive to crying authenticity at the N1 and middle LPP stages, and to laughter authenticity at the early LPP stage. Furthermore, early-blind and sighted participants were more sensitive than late-blind ones to crying authenticity at the P2 and late LPP stages.Altogether, these findings suggest that early blindness relates to facilitated brain processing of authenticity in voices, both at early sensory and late cognitive-evaluative stages. Late-onset blindness, in contrast, relates to decreased sensitivity to authenticity at behavioral and brain levels.

Piaget's 3-mountains task with impossible options: Sighted, blindfolded, early and late blind participants.

In Piaget's 3-mountains task, 3D objects - a cube, cone and sphere - sit on a square tabletop. They are portrayed in 2D pictures as elevations (projections to the sides) such as one with a square on the left, a triangle in the middle and a circle on the right. Three objects offer six elevations, of which four are possible and two impossible. The possibles are elevations from the sides of the table - front, left, right and rear. In the impossibles, an object in the corner of the table is shown in the middle of an elevation. Sighted, sighted-blindfolded, early- and late-blind adults judged the elevations as to side of the table or impossible. The results suggest similar spatial abilities across groups. The impossible options had mid-range accuracy for all groups, with reaction times like possible options. The sighted and blind participants may consider possible and impossible options sequentially, one item at a time.

Beyond the Cane: Describing Urban Scenes to Blind People for Mobility Tasks.

Blind people face difficulties with independent mobility, impacting employment prospects, social inclusion, and quality of life. Given the advancements in computer vision, with more efficient and effective automated information extraction from visual scenes, it is important to determine what information is worth conveying to blind travelers, especially since people have a limited capacity to receive and process sensory information. We aimed to investigate which objects in a street scene are useful to describe and how those objects should be described. Thirteen cane-using participants, five of whom were early blind, took part in two urban walking experiments. In the first experiment, participants were asked to voice their information needs in the form of questions to the experimenter. In the second experiment, participants were asked to score scene descriptions and navigation instructions, provided by the experimenter, in terms of their usefulness. The descriptions included a variety of objects with various annotations per object. Additionally, we asked participants to rank order the objects and the different descriptions per object in terms of priority and explain why the provided information is or is not useful to them. The results reveal differences between early and late blind participants. Late blind participants requested information more frequently and prioritized information about objects' locations. Our results illustrate how different factors, such as the level of detail, relative position, and what type of information is provided when describing an object, affected the usefulness of scene descriptions. Participants explained how they (indirectly) used information, but they were frequently unable to explain their ratings. The results distinguish between various types of travel information, underscore the importance of featuring these types at multiple levels of abstraction, and highlight gaps in current understanding of travel information needs. Elucidating the information needs of blind travelers is critical for the development of more useful assistive technologies.

English

BACKGROUND The objectives of the study were to assess and compare touch sensation of dominant and non-dominant hands among blind since birth, early onset blind & late onset blind participants using Moberg’s test and determine if the time of onset of blindness affected the touch sensation. METHODS 50 blind participants from various colleges in Mumbai were assessed. Detailed history about onset of blindness, motor dominance etc. of blind was asked. Participants were instructed to pick up objects (suggested by Moberg) one at a time, as fast as possible, and place them into a box using dominant and non-dominant hands alternatively. Kruskal Wallis Test was used for analysis. RESULTS Average values of Moberg’s test of dominant & non - dominant hands of blind since birth versus late onset blind were statistically significant and those of early onset blind versus late onset blind were statistically significant. Average values of Moberg’s test of blind since birth versus early onset blind were not statistically significant. Thus touch sensation was improved more in blind since birth & early onset blind compared to late onset blind participants. CONCLUSIONS Thus we conclude that in the absence of visual stimuli, touch sensation in blind since birth and early onset blind is improved compared to late onset blind participants. KEY WORDS Blind, Cross - Modal Synaptic Plasticity, Substitution of Sense. Moberg's Pick - up Test, Critical Period

Graphomotor memory in Exner\u2019s area enhances word learning in the blind

Handwriting is thought to impede vocabulary learning in sighted adults because the motor execution of writing interferes with efficient audiovisual processing during encoding. However, the motor memory of writing may facilitate adult word learning when visual sensory inputs are severely restricted. Using functional MRI, we show that late-blind participants, but not sighted participants, learned novel words by recruiting the left dorsal premotor cortex known as Exner’s writing area and its functional coupling with the left hippocampus. During later recall, the phonological and semantic contents of these words are represented in the activation patterns of the left hippocampus as well as in those of left frontotemporal language areas. These findings suggest that motor codes of handwriting help blind participants maintain word-form representations during learning and retrieval. We propose that such reliance on the motor system reflects a broad architecture of the cerebral language network which encompasses the limb motor system as a hardwired component.

Verbally Induced Olfactory Illusions Are Not Caused by Visual Processing: Evidence From Early and Late Blindness.

Olfactory perception is malleable and easily modulated by top-down processes such as those induced by visual and verbal information. A classic example of this is olfactory illusions where the perceived pleasantness of an odor is manipulated by the valence of a verbal label that is either visually or auditorily presented together with the odor. The mechanism behind this illusion is still unknown, and it is not clear if it is driven only by verbal information or if there is an interaction between language functions and visual mental imagery processes. One way to test this directly is to study early blind individuals who have little or no experience of visual information or visual mental imagery. Here, we did this by testing early blind, late blind, and sighted individuals in a classical paradigm where odors were presented with negative, neutral, and positive labels via speech. In contrast to our hypothesis—that the lack of visual imagery would render early blind individuals less susceptible to the olfactory illusion—early and late blind participants showed more amplified illusions than sighted. These findings demonstrate that the general mechanism underlying verbally induced olfactory illusions is not caused by visual processing and visual mental imagery per se.

Evaluation of Memory and Language Network in Children and Adolescents with Visual Impairment: A Combined Functional Connectivity and Voxel-based Morphometry Study

ABSTRACT Functional network changes associated with Braille reading are different in early blind (EB) and late blind (LB) participants. The objectives were to study the functional connectivity (of memory and language areas based on blood oxygen level-dependent [BOLD] mapping) and structural changes in EB and LB children and adolescents. A total of 110 participants (all right-handed) were recruited in two age groups of 6–12 years (children) and 13–19 years (adolescents) consisting of EB (n = 20), LB (n = 20), and sighted controls (SC, n = 15) in each group. Group differences were estimated between children and adolescent groups. Structural changes in visual cortex and medial temporal area, increased BOLD activations and altered functional connectivity in the primary visual cortex, inferior frontal gyrus, middle temporal gyrus, and hippocampus during Braille reading task were observed in adolescents as compared with children blind groups (pFDR corrected <0.05). Functional results were positively correlated with duration of Braille reading and age at onset in EB and LB groups (p ≤ 0.01). Visual, language, and learning memory networks were different in adolescents and children of both EB and LB groups, and also between EB and LB groups suggesting cross-modal plasticity. The functional and structural results revealed education dependent cross-modal plasticity in visually impaired participants. Memory and language network were affected more in the LB group than the EB group, and more in children than adolescents.

A quantitative analysis of the retinofugal projections in congenital and late-onset blindness

Vision loss early in life has dramatic consequences on the organization of the visual system and hence on structural plasticity of its remnant components. Most of the studies on the anatomical changes in the brain following visual deprivation have focused on the re-organization of the visual cortex and its afferent and efferent projections. In this study, we performed a quantitative analysis of the volume and size of the optic chiasm, optic nerve, optic tract and the lateral geniculate nucleus (LGN), the retino recipient thalamic nucleus. Analysis was carried out on structural T1-weighted MRIs from 22 congenitally blind (CB), 14 late blind (LB) and 29 age -and sex-matched sighted control (SC) subjects. We manually segmented the optic nerve, optic chiasm and optic tract, while LGN volumes were extracted using in-house software. We also measured voxel intensity of optic nerve, optic chiasm and optic tract. Mean volumes of the optic nerve, optic tract and optic chiasm were reduced by 50 to 60% in both CB and LB participants. No significant differences were found between the congenitally and late-onset blind participants for any of the measures. Our data further revealed reduced white matter voxel intensities in optic nerve, optic chiasm and optic tract in blind compared to sighted participants, suggesting decreased myelin content in the atrophied white matter. The LGN was reduced by 50% and 44% in CB and LB, respectively. In LB, optic nerve volume correlated negatively with the blindness duration index; no such correlation was found for optic chiasm, optic tract and LGN. The observation that despite the absence of visual input about half of the subcortical retinofugal projections are structurally preserved raises the question of their functional role. One possibility is that the surviving fibers play a role in the maintenance of circadian rhythms in the blind through the intrinsically photosensitive melanopsin-containing retinal ganglion cells.

Assessment of spatial reasoning in blind individuals using a haptic version of the Kohs Block Design Test

• Early blind individuals show difficulties in manipulating haptic spatial configurations. • Late blind and sighted individuals report efficient spatial reasoning capabilities. • Performance in spatial reasoning task is not related to duration of blindness. • Adapted neuropsychological tests are efficient tools to assess the cognitive functioning of blind people. Past research investigating the spatial abilities of visually impaired people, provided conflicting results. There is thus an urgent need to develop standardized tests for the evaluation of spatial cognition when vision is absent or disrupted. To this aim, we developed a haptic version of the Kohs Block Design Test and investigated the spatial non-verbal reasoning of early blind, late blind and sighted individuals. Participants reproduced 3D printed haptic configurations by assembling blocks with different textures, within a time limit. Results showed that early blind individuals reproduced fewer haptic designs than the other two groups correctly. Instead, the assembling time of the correct responses was similar among all groups. Moreover, blindness duration (in years) did not seem to affect the correctness of the performance: no significant correlation between the two variables was observed for early and late blind participants. Since only early blind individuals display difficulties in mentally representing the haptic configurations and manipulating multiple spatial information, we conclude that early visual deprivation may affect spatial reasoning capabilities. The present study adds new insights on the role of visual experience in the development of spatial skills and represents a first step in the adaptation of standardized tests for the assessment of spatial cognitive abilities in visually impaired people.

The Influence of the Encoding Modality on Spatial Navigation for Sighted and Late-Blind People.

People usually rely on sight to encode spatial information, becoming aware of other sensory cues when deprived of vision. In the absence of vision, it has been demonstrated that physical movements and spatial descriptions can effectively provide the spatial information that is necessary for the construction of an adequate spatial mental model. However, no study has previously compared the influence of these encoding modalities on complex movements such as human spatial navigation within real room-size environments. Thus, we investigated whether the encoding of a spatial layout through verbal cues - that is, spatial description - and motor cues - that is, physical exploration of the environment - differently affect spatial navigation within a real room-size environment, by testing blindfolded sighted (Experiment 1) and late-blind (Experiment 2) participants. Our results reveal that encoding the environment through physical movement is more effective than through verbal descriptions in supporting active navigation. Thus, our findings are in line with the studies claiming that the physical exploration of an environment enhances the development of a global spatial representation and improves spatial updating. From an applied perspective, the present results suggest that it might be possible to improve the experience for visually impaired people within a new environment by allowing them to explore it.

Impact of years of blindness on neural circuits underlying auditory spatial representation

Early visual deprivation impacts negatively on spatial bisection abilities. Recently, an early (50–90 ms) ERP response, selective for sound position in space, has been observed in the visual cortex of sighted individuals during the spatial but not the temporal bisection task.Here, we clarify the role of vision on spatial bisection abilities and neural correlates by studying late blind individuals. Results highlight that a shorter period of blindness is linked to a stronger contralateral activation in the visual cortex and a better performance during the spatial bisection task. Contrarily, not lateralized visual activation and lower performance are observed in individuals with a longer period of blindness.To conclude, the amount of time spent without vision may gradually impact on neural circuits underlying the construction of spatial representations in late blind participants. These findings suggest a key relationship between visual deprivation and auditory spatial abilities in humans.

Visual loss alters multisensory face maps in humans

Topographically organised responses to visual and tactile stimulation are aligned in the ventral intraparietal cortex. The critical biological importance of this region, which is thought to mediate visually guided defensive movements of the head and upper body, suggests that these maps might be hardwired from birth. Here, we investigated whether visual experience is necessary for the creation and positioning of these maps by assessing the representation of tactile stimulation in congenitally and totally blind participants, who had no visual experience, and late and totally blind participants. We used a single-subject approach to the analysis to focus on the potential individual differences in the functional neuroanatomy that might arise from different causes, durations and sensory experiences of visual impairment among participants. The overall results did not show any significant difference between congenitally and late blind participants; however, single-subject trends suggested that visual experience is not necessary to develop topographically organised maps in the intraparietal cortex, whilst losing vision disrupted topographic maps' integrity and organisation. These results discussed in terms of brain plasticity and sensitive periods.

The role of visual experience in the emergence of cross-modal correspondences

Cross-modal correspondences describe the widespread tendency for attributes in one sensory modality to be consistently matched to those in another modality. For example, high pitched sounds tend to be matched to spiky shapes, small sizes, and high elevations. However, the extent to which these correspondences depend on sensory experience (e.g. regularities in the perceived environment) remains controversial. Two recent studies involving blind participants have argued that visual experience is necessary for the emergence of correspondences, wherein such correspondences were present (although attenuated) in late blind individuals but absent in the early blind. Here, using a similar approach and a large sample of early and late blind participants (N = 59) and sighted controls (N = 63), we challenge this view. Examining five auditory-tactile correspondences, we show that only one requires visual experience to emerge (pitch-shape), two are independent of visual experience (pitch-size, pitch-weight), and two appear to emerge in response to blindness (pitch-texture, pitch-softness). These effects tended to be more pronounced in the early blind than late blind group, and the duration of vision loss among the late blind did not mediate the strength of these correspondences. Our results suggest that altered sensory input can affect cross-modal correspondences in a more complex manner than previously thought and cannot solely be explained by a reduction in visually-mediated environmental correlations. We propose roles of visual calibration, neuroplasticity and structurally-innate associations in accounting for our findings.

Anticipatory action planning in blind and sighted individuals

Several studies on visually guided reach-to-grasp movements have documented that how objects are grasped differs depending on the actions one intends to perform subsequently. However, no previous study has examined whether this differential grasping may also occur without visual input. In this study, we used motion capture technology to investigate the influence of visual feedback and prior visual experience on the modulation of kinematics by intention in sighted (in both full-vision and no-vision conditions), early-blind and late-blind participants. Results provide evidence of modulation of kinematics by intention to a similar degree under both full-vision and no-vision conditions. Moreover, they demonstrate that prior visual experience has little impact on the tailoring of grasping movements to intention. This suggests that sequential action planning does not depend on visual input, and may instead be ascribed to the function of multisensory-motor cortical network that operates and develops not only in light, but also in darkness.

Olfactory Performance in a Large Sample of Early-Blind and Late-Blind Individuals.

Previous examinations of olfactory sensitivity in blind people have produced contradictory findings. Thus, whether visual impairment is associated with increased olfactory abilities is unclear. In the present investigation, I aimed to resolve the existing questions via a relatively large-scale study comprising early-blind (N = 43), and late-blind (N = 41) and sighted (N = 84) individuals matched in terms of gender and age. To compare the results with those of previous studies, I combined data from a free odor identification test, extensive psychophysical testing (Sniffin' Sticks test), and self-assessed olfactory performance. The analyses revealed no significant effects of sight on olfactory threshold, odor discrimination, cued identification, or free identification scores; neither was the performance of the early-blind and late-blind participants significantly different. Additionally, the self-assessed olfactory abilities of the blind people were no different than those of the sighted people. These results suggest that sensory compensation in visually impaired is not pronounced with regards to olfactory abilities as measured by standardized smell tests.

V10. Learning to comprehend time-compressed speech affects premotor and cerebellar regions in late-blind and normally sighted subjects

Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables per second (syl/s), exceeding by far the maximum performance level of untrained listeners (ca. 8 syl/s). Previous findings (Dietrich et al., 2013, BMC Neuroscience) indicate that, in addition to the classical language zones (left inferior frontal gyrus, bilateral middle temporal gyrus), right visual cortex (V1), left supplementary motor area (SMA), and cerebellum contribute to the processing of accelerated speech in blind subjects. As an extension, the present training experiment using functional magnetic resonance imaging (fMRI) addresses the issue whether acquisition of ultra-fast (18 syl/s) speech perception skills induces central-visual hemodynamic activation in late-blind participants. Furthermore, we asked to what extent subjects with normal or residual vision can improve understanding of accelerated verbal utterances and whether differential training effects for sighted as compared to blind subjects can be demonstrated. To these ends, prior to and after a training period of ca. six months, fMRI was performed while subjects were listening to forward and time-reversed sentence utterances of a moderately fast (8 syl/s) or an ultra-fast syllable rate (18 syl/s). Eight participants, varying in the amount of residual visual functions, considerably improved their comprehension of ultra fast speech comprehension (pre-training: 9%, SD=13.4, post-training: 70%, SD=16.9; correct words in a sentence repetition task). Among other regions, left SMA, bilateral cerebellum, and right V1 showed a significant interaction (ANOVA) of the factors rate (8 vs. 18 syl/s) and stage (untrained vs. trained). After training, during the ultra-fast speech condition all subjects displayed an increase of hemodynamic activation in left SMA, and cerebellar activation was increased in five of eight participants. Training-induced hemodynamic activation of the central-visual system was only found in subjects with very low visual acuity. Thus, perceptual learning seems to involve SMA-cerebellar circuits, primarily known from motor learning tasks. It can be assumed that SMA and cerebellum contribute to a mechanism of time-critical processing that is required for the reconstruction of the syllabic structure ultra-fast speech during lexical encoding toward verbal working memory. Furthermore, in spite of similar behavioral performance, trained experts appear to use distinct strategies of ultra-fast speech processing depending on whether the occipital cortex is still deployed for visual processing (Fig. 1).

Evaluation of the attentional capacities and working memory of early and late blind persons

Although attentional processes and working memory seem to be significantly involved in the daily activities (particularly during navigating) of persons who are blind and who use these abilities to compensate for their lack of vision, few studies have investigated these mechanisms in this population. The aim of this study is to evaluate the selective, sustained and divided attention, attentional inhibition and switching and working memory of blind persons. Early blind, late blind and sighted participants completed neuropsychological tests that were designed or adapted to be achievable in the absence of vision. The results revealed that the early blind participants outperformed the sighted ones in selective, sustained and divided attention and working memory tests, and the late blind participants outperformed the sighted participants in selective, sustained and divided attention. However, no differences were found between the blind groups and the sighted group in the attentional inhibition and switching tests. Furthermore, no differences were found between the early and late blind participants in this set of tests. These results suggest that early and late blind persons can compensate for the lack of vision by an enhancement of the attentional and working memory capacities.

Pain Perception Is Increased in Congenital but Not Late Onset Blindness

There is now ample evidence that blind individuals outperform sighted individuals in various tasks involving the non-visual senses. In line with these results, we recently showed that visual deprivation from birth leads to an increased sensitivity to pain. As many studies have shown that congenitally and late blind individuals show differences in their degree of compensatory plasticity, we here address the question whether late blind individuals also show hypersensitivity to nociceptive stimulation. We therefore compared pain thresholds and responses to supra-threshold nociceptive stimuli in congenitally blind, late blind and normally sighted volunteers. Participants also filled in questionnaires measuring attention and anxiety towards pain in everyday life. Results show that late blind participants have pain thresholds and ratings of supra-threshold heat nociceptive stimuli similar to the normally sighted, whereas congenitally blind participants are hypersensitive to nociceptive thermal stimuli. Furthermore, results of the pain questionnaires did not allow to discriminate late blind from normal sighted participants, whereas congenitally blind individuals had a different pattern of responses. Taken together, these results suggest that enhanced sensitivity to pain following visual deprivation is likely due to neuroplastic changes related to the early loss of vision.

Visual experience influences the interactions between fingers and numbers

Though a clear interaction between finger and number representations has been demonstrated, what drives the development of this intertwining remains unclear. Here we tested early blind, late blind and sighted control participants in two counting tasks, each performed under three different conditions: a resting condition, a condition requiring hands movements and a condition requiring feet movements. In the resting condition, every sighted and late blind spontaneously used their fingers, while the majority of early blind did not. Sighted controls and late blind were moreover selectively disrupted by the interfering hand condition, while the early blind who did not use the finger-counting strategy remained unaffected by the interference conditions. These results therefore demonstrate that visual experience plays an important role in implementing the sensori-motor habits that drive the development of finger–number interactions.