Daniel-Robert Chebat

Navigation with a sensory substitution device in congenitally blind individuals.

Vision allows for obstacle detection and avoidance. The compensatory mechanisms involved in maintaining these functions in blind people using their remaining intact senses are poorly understood. We investigated the ability of congenitally blind participants to detect and avoid obstacles using the tongue display unit, a sensory substitution device that uses the tongue as a portal to the brain. We found that congenitally blind were better than sighted control participants in detecting and avoiding obstacles using the tongue display unit. Obstacles size and avoidance strategy had a significant effect on performance: large obstacles were better detected than small ones and step-around obstacles were better avoided than step-over ones. These data extend our earlier findings that when using a sensory substitution device, blind participants outperform sighted controls not only in a virtual navigation task but also during effective navigation within a human-sized obstacle course.

Tactile-'visual' acuity of the tongue in early blind individuals.

This study compares the ‘tactile–visual’ acuity of the tongue for 15 early blind participants with that of 24 age-matched and sex-matched sighted controls. Snellens tumbling E test was used to assess ‘visual’ acuity using the tongue display unit. The tongue display unit is a sensory substitution device that converts a visual stimulus grabbed by a camera into electro-tactile pulses delivered to the tongue via a grid made out of electrodes. No overall significant difference was found in thresholds between early blind (1/206) and sighted control (1/237) participants. We found, however, a larger proportion of early blind in the two highest visual acuity categories (1/150 and 1/90). These results extend earlier findings that it is possible to measure visual acuity in the blind individuals using the tongue. Moreover, our data demonstrate that a subgroup of early blind participants is more efficient than controls in conveying visual information through the tongue.

Increasing Accessibility to the Blind of Virtual Environments, Using a Virtual Mobility Aid Based On the "EyeCane": Feasibility Study

Virtual worlds and environments are becoming an increasingly central part of our lives, yet they are still far from accessible to the blind. This is especially unfortunate as such environments hold great potential for them for uses such as social interaction, online education and especially for use with familiarizing the visually impaired user with a real environment virtually from the comfort and safety of his own home before visiting it in the real world. We have implemented a simple algorithm to improve this situation using single-point depth information, enabling the blind to use a virtual cane, modeled on the “EyeCane” electronic travel aid, within any virtual environment with minimal pre-processing. Use of the Virtual-EyeCane, enables this experience to potentially be later used in real world environments with identical stimuli to those from the virtual environment. We show the fast-learned practical use of this algorithm for navigation in simple environments.

Does Age Attenuate the Impact of Pleasant Ambient Scent on Consumer Response

A large-scale field survey (n = 592) was conducted in a suburban shopping mall to assess the impact of pleasant ambient scent on consumer spending as a function of shopper age. A citrus scent was systematically emitted into the shopping mall (or not) over several weeks, and as shoppers were about to exit the mall, they were intercepted to complete a survey. In the survey, respondents reported the amount of expenditures in the mall that day as well as their perceptions of the mall and demographic characteristics, such as age. The results indicate that shoppers spent significantly more in the mall with the presence of the pleasant ambient scent, but this result was true only among younger shoppers. Theoretical and practical implications of the reduced impact of ambient scent on older persons are discussed.

Spatial navigation by congenitally blind individuals

Spatial navigation in the absence of vision has been investigated from a variety of perspectives and disciplines. These different approaches have progressed our understanding of spatial knowledge acquisition by blind individuals, including their abilities, strategies, and corresponding mental representations. In this review, we propose a framework for investigating differences in spatial knowledge acquisition by blind and sighted people consisting of three longitudinal models (i.e., convergent, cumulative, and persistent). Recent advances in neuroscience and technological devices have provided novel insights into the different neural mechanisms underlying spatial navigation by blind and sighted people and the potential for functional reorganization. Despite these advances, there is still a lack of consensus regarding the extent to which locomotion and wayfinding depend on amodal spatial representations. This challenge largely stems from methodological limitations such as heterogeneity in the blind population and terminological ambiguity related to the concept of cognitive maps. Coupled with an over‐reliance on potential technological solutions, the field has diffused into theoretical and applied branches that do not always communicate. Here, we review research on navigation by congenitally blind individuals with an emphasis on behavioral and neuroscientific evidence, as well as the potential of technological assistance. Throughout the article, we emphasize the need to disentangle strategy choice and performance when discussing the navigation abilities of the blind population. WIREs Cogn Sci 2016, 7:37–58. doi: 10.1002/wcs.1375 For further resources related to this article, please visit the WIREs website.

Navigation Using Sensory Substitution in Real and Virtual Mazes

Under certain specific conditions people who are blind have a perception of space that is equivalent to that of sighted individuals. However, in most cases their spatial perception is impaired. Is this simply due to their current lack of access to visual information or does the lack of visual information throughout development prevent the proper integration of the neural systems underlying spatial cognition? Sensory Substitution devices (SSDs) can transfer visual information via other senses and provide a unique tool to examine this question. We hypothesize that the use of our SSD (The EyeCane: a device that translates distance information into sounds and vibrations) can enable blind people to attain a similar performance level as the sighted in a spatial navigation task. We gave fifty-six participants training with the EyeCane. They navigated in real life-size mazes using the EyeCane SSD and in virtual renditions of the same mazes using a virtual-EyeCane. The participants were divided into four groups according to visual experience: congenitally blind, low vision & late blind, blindfolded sighted and sighted visual controls. We found that with the EyeCane participants made fewer errors in the maze, had fewer collisions, and completed the maze in less time on the last session compared to the first. By the third session, participants improved to the point where individual trials were no longer significantly different from the initial performance of the sighted visual group in terms of errors, time and collision.

The Effect of Extended Sensory Range via the EyeCane Sensory Substitution Device on the Characteristics of Visionless Virtual Navigation

Mobility training programs for helping the blind navigate through unknown places with a White-Cane significantly improve their mobility. However, what is the effect of new assistive technologies, offering more information to the blind user, on the underlying premises of these programs such as navigation patterns? We developed the virtual-EyeCane, a minimalistic sensory substitution device translating single-point-distance into auditory cues identical to the EyeCanes in the real world. We compared performance in virtual environments when using the virtual-EyeCane, a virtual-White-Cane, no device and visual navigation. We show that the characteristics of virtual-EyeCane navigation differ from navigation with a virtual-White-Cane or no device, and that virtual-EyeCane users complete more levels successfully, taking shorter paths and with less collisions than these groups, and we demonstrate the relative similarity of virtual-EyeCane and visual navigation patterns. This suggests that additional distance information indeed changes navigation patterns from virtual-White-Cane use, and brings them closer to visual navigation.

Development of the commissure of the superior colliculus in the hamster.

The development of the corpus callosum (CC) and the anterior commissure (CA) is well known in a wide variety of species. No study, however, has described the development of the commissure of the superior colliculus (CSC) from embryonic state to adulthood in mammals. In this study, by using the lipophylic tracer DiI, we investigated the ontogeny of this mesencephalic commissure in the hamster at various ages. The development of axonal terminals, growth cone morphologies, and axons branching were described for the superior colliculus (SC) contralateral to the tracer injection. The first CSC axons cross the midline at embryonic day 11 (E‐11) and grow further into the intermediate layers of the contralateral SC between E‐12 and E‐14. There is little axon growth therein between E‐14 and the day of birth (P‐0). Growth cones at the tip of these axons adopt complex morphologies at E‐12 and progressively simplify until P‐0. Pioneer axons are clearly visible between E‐14 and P‐1. These are followed by other axons progressively more numerous between P‐0 and P‐5. Axons do not show any branching until P‐2. Between P‐3 and P‐9, the axons progressively arborize in the intermediate layers. Some axons reach the superficial layers at P‐5, and they become more numerous around P‐11, and only a few axons remain therein by P‐21. Myelinated axons appear at P11 and are very dense at P‐21. Our results indicate that the CSC follows developmental schemes similar to those of the CC and the AC but that initial axon midline crossing occurs earlier. J. Comp. Neurol. 494:887–902, 2006.

Sensory Substitution and the Neural Correlates of Navigation in Blindness

This chapter reviews the most recent advances in sensory substitution and the neural correlates of navigation in congenital blindness . Studies have established the superior ability of congenitally blind (CB) participants with the aid of Sensory Substitution Devices (SSDs) to navigate new environments and detect the size and shape of obstacles in order to avoid them. These studies suggest that with training, CB can achieve a representation of space that is equivalent to that of the sighted. From a phenomenological point of view, sensation and perception provided by SSDs have been likened to real vision, but the question remains as to the subjective sensations (qualia) felt by users. We review recent theories on the phenomenological properties of sensory substitution and the recent literature on spatial abilities of participants using SSDs. From these different sources of research, we conclude that training-induced plastic changes enable task-specific brain activations. The recruitment of the primary visual cortex by nonvisual SSD stimulations and, the subsequent activations of associative visual cortices in the congenitally blind, suggest that the sensory information is treated in an amodal fashion; i.e.,: in terms of the task being performed rather than the sensory modality. These anatomical changes enable the embodiment of nonvisual information allowing SSD users to accomplish a multitude of “visual” tasks. We will emphasize here the abilities of CB individuals to navigate in real and virtual environments in spite of a large volumetric reduction in the posterior segment of the hippocampus , a key area involved in navigation . In addition, the superior behavioral performance of CB in a variety of sensory and cognitive tasks, combined with anatomical and functional MRI, underlines the susceptibility of the brain to training-induced plasticity.

The blind get a taste of vision

In sensory substitution a given sensory modality acquires the functional properties of a missing one. This phenomenon is due to a reorganization of the sensory systems that are deprived of their normal input through a process called cross-modal plasticity [1]. ‘Rewiring’ studies carried out on ferrets [2] and hamsters [3] provided strong support for these phenomena. For example, lesions of central retinal targets induce the formation of new and permanent retinofugal projections into non-visual thalamic sites such as the auditory nucleus [3]. Single neurons in the auditory cortex of these rewired animals respond to visual stimuli and some of them respond equally well to auditory as to visual stimuli. Moreover, those cells that respond to visual stimuli show properties (e.g., orientation selectivity, motion and direction sensitivity) similar to those encountered in the visual cortex of normal hamsters.