A neurophysiological and behavioral investigation of tactile spatial exploration for sighted and non-sighted adults (original) (raw)
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Proceedings of the …, 2011
In this work in progress we propose a new method for evaluating objectively the process of performing a tactile exploration with a visuo-tactile sensory substitution system. Both behavioral and neurophysiological cues are considered to evaluate the identification process of virtual objects and surrounding environments. Our experiments suggest that both sighted and visually impaired users integrated spatial information and developed similar behavioural and neurophysiological patterns. The proposed method could also serve as a tool to evaluate touch-based interfaces for application in orientation and mobility programs.
Journal of …, 2012
Campus C, Brayda L, De Carli F, Chellali R, Famà F, Bruzzo C, Lucagrossi L, Rodriguez G. Tactile exploration of virtual objects for blind and sighted people: the role of beta 1 EEG band in sensory substitution and supramodal mental mapping. The neural correlates of exploration and cognitive mapping in blindness remain elusive. The role of visuo-spatial pathways in blind vs. sighted subjects is still under debate. In this preliminary study, we investigate, as a possible estimation of the activity in the visuo-spatial pathways, the EEG patterns of blind and blindfolded-sighted subjects during the active tactile construction of cognitive maps from virtual objects compared with rest and passive tactile stimulation. Ten blind and ten matched, blindfolded-sighted subjects participated in the study. Events were defined as moments when the finger was only stimulated (passive stimulation) or the contour of a virtual object was touched (during active exploration). Event-related spectral power and coherence perturbations were evaluated within the beta 1 band (14 -18 Hz). They were then related to a subjective cognitive-load estimation required by the explorations [namely, perceived levels of difficulty (PLD)]. We found complementary cues for sensory substitution and spatial processing in both groups: both blind and sighted subjects showed, while exploring, late power decreases and early power increases, potentially associated with motor programming and touch, respectively. The latter involved occipital areas only for blind subjects (long-term plasticity) and only during active exploration, thus supporting tactileto-visual sensory substitution. In both groups, coherences emerged among the fronto-central, centro-parietal, and occipito-temporal derivations associated with visuo-spatial processing. This seems in accordance with mental map construction involving spatial processing, sensory-motor processing, and working memory. The observed involvement of the occipital regions suggests that a substitution process also occurs in sighted subjects. Only during explorations did coherence correlate positively with PLD for both groups and in derivations, which can be related to visuo-spatial processing, supporting the existence of supramodal spatial processing independently of vision capabilities. spatial processing; visuo-spatial pathways; cognitive mapping; virtual reality Address for reprint requests and other correspondence: C.
Do Blind Subjects Differ from Sighted Subjects When Exploring Virtual Tactile Maps?
Lecture Notes in Computer Science, 2014
The access to graphical information is difficult for individuals who are blind or visually impaired. Taking advantage of the residual sensory abilities such as touch is one way to solve this issue. However, it is not yet clear if blind subjects perceive new tacto-spatial information in the same way that sighted people do. In this work we code the discovery of unknown tactile virtual objects in terms of subjective and behavioral variables, which result to be independent on visual deprivation and dependent only on task difficulty. Our methodology can be employed in educational, orientation and mobility protocols.
Predicting Successful Tactile Mapping of Virtual Objects
IEEE Transactions on Haptics
Improving spatial ability of blind and visually impaired people is the main target of orientation and mobility (O&M) programs. In this study we use a minimalistic mouse-shaped haptic device to show a new approach aimed at evaluating devices providing tactile representations of virtual objects. We consider psychophysical, behavioural and subjective parameters to clarify under which circumstances mental representations of spaces (cognitive maps) can be efficiently constructed with touch by blindfolded sighted subjects. We study two complementary processes which determine map construction: low-level perception (in a passive stimulation task) and high-level information integration (in an active exploration task). We show that jointly considering a behavioural measure of information acquisition and a subjective measure of cognitive load can give an accurate prediction and a practical interpretation of mapping performance. Our simple TActile MOuse (TAMO) uses haptics to assess spatial ability: this may help individuals who are blind or visually impaired to be better evaluated by O&M practitioners or to evaluate their own performance.
Human Factors, 2009
Objective: Our goal was to determine the optimal elevation of tactile map symbols. Background: Tactile perception research predicts that symbol elevation (vertical height) and texture on tactile maps could influence their readability. However, although research has shown that elevation influences detection and discrimination thresholds for single tactile stimuli and that the physiological response of fingertip receptors varies with texture, little is known about the influence of these parameters on the identification of stimuli in the context of multiple symbols as found on tactile maps. Method: Sighted and visually impaired participants performed tactile symbol identification tasks. In Experiment 1, we measured the effect of elevation on identification accuracy. In Experiment 2, we measured the effect of elevation and symbol texture on identification speed. Results: Symbol elevation influenced both speed and accuracy of identification; thresholds were higher than those found in work on detection and discrimination but lower than on existing tactile maps. Furthermore, as predicted from existing knowledge of tactile perception, rough features were identified more quickly than smooth ones. Finally, visually impaired participants performed better than sighted ones. Conclusion: The symbol elevations necessary for identification (0.040 to 0.080 mm) are considerably lower than would be expected on the basis of existing tactile maps (generally 0.5 mm or higher) and design guidelines (0.4 mm). Application: Tactile map production costs could be reduced and map durability increased by reducing symbol elevation. Furthermore, legibility of maps could be improved by using rough features, which are read more easily, and smaller symbols, which reduce crowding of graphics.
Identification of Textured Tactile Pictures in Visually Impaired and Blindfolded Sighted Children
Frontiers in Psychology
A high level of variability in the capacity of visually impaired children to accurately identify tactile images is reported in the literature, with on average rather low percentages of correct naming responses. However, most of these studies used raised-line drawings as stimuli to be explored and named. The present experiment investigated whether blind children of 3 to 8 years of age would demonstrate a satisfactory ability to name the elements making up tactile images when tested in an experimental setting similar to their natural reading conditions. Textured tactile images taken from genuine illustrated tactile books for young children were used, and the participants received information about the title of the book or listened the text that accompanied each picture before exploration, as it would occur in a natural reading setting. The results showed that their naming scores were indeed higher than previously reported at equivalent ages and did not differ from those of age-matched sighted children. These scores were positively impacted by haptic practice in blind children and correlated with the use of some specific exploratory procedures. The blind children benefited from information provided before exploration, as did their sighted counterparts. However, only in the former did the condition in which full information was provided influence the way the children organized their exploration. The haptic identification scores increased with age regardless of visual status, with the exploration times decreasing in the blind children, while the reverse trend was observed in the sighted children. These results are discussed at the light of the image-mediation model of haptics, suggesting that during the age period considered in the present experiment, blind children would progressively learn to process haptic information directly, thus leading to a decrease of exploration times, while sighted children would learn to translate haptic information into a visual image used to retrieve semantic information, involving an increase of their exploration times.
Cognitive map formation in the blind is enhanced by three-dimensional tactile information
For blind individuals, tactile maps are useful tools to form cognitive maps through touch. However, they still experience challenges in cognitive map formation and independent navigation. Three-dimensional (3D) tactile information is thus increasingly being considered to convey enriched spatial information, but it remains unclear if it can facilitate cognitive map formation compared to traditional two-dimensional (2D) tactile information. Consequently, the present study investigated the impact of the type of sensory input (tactile vs. visual) on cognitive map formation. To do so, early blind (EB, n=13), late blind (LB, n=12), and sighted (SC, n=14) participants were tasked to learn the layouts of mazes produced with different sensory information (visual vs. tactile 2D vs. tactile 3D) and to infer routes from memory. Results show that EB only manifested stronger cognitive map formation with 3D mazes. LB performed equally well with 2D and 3D mazes, and SC manifested equivalent cogniti...