Tactile Exploration of Virtual Objects for Blind and Sighted People: the Role of Beta 1 Eeg Band in Sensory Substitution and Supra-modal Mental Mapping 2 3

45 The neural correlates of exploration and cognitive mapping in blindness remain elusive. The role of 46 visuo-spatial pathways in blind versus sighted subjects is still under debate. In this preliminary study we 47 investigate, as a possible estimation of the activity in the visuo-spatial pathways, the EEG patterns of 48 blind and blindfolded sighted subjects during the active tactile construction of cognitive maps from 49 virtual objects as compared to rest and passive tactile stimulation. 50 10 blind and 10 matched blindfolded sighted subjects participated in the study. Events were defined as 51 moments when the finger was only stimulated (passive stimulation) or the contour of a virtual object was 52 touched (during active exploration). Event-related spectral power and coherence perturbations were 53 evaluated within the beta 1 band (14-18 Hz). They were then related to a subjective cognitive-load 54 estimation required by the explorations (Perceived Levels of Difficulty). We found complementary cues 55 for sensory substitution and spatial processing in both groups: both blind and sighted subjects showed, 56 while exploring, late power decreases and early power increases, potentially associated with motor 57 programming and touch, respectively. The latter involved occipital areas only for blind subjects (long58 term plasticity) and only during active exploration, thus supporting tactile-to-visual sensory substitution. 59 In both groups, coherences emerged among the fronto-central, centro-parietal and occipito-temporal 60 derivations associated with visuo-spatial processing. This seems in accordance with mental map 61 construction involving spatial processing, sensory-motor processing and working memory. The observed 62 involvement of the occipital regions suggests that a substitution process also occurs in sighted subjects. 63 Only during explorations, coherence correlated positively with Perceived Levels of Difficulty for both 64 groups and in derivations which can be related to visuo-spatial processing, supporting the existence of 65 supra-modal spatial processing independently of vision capabilities. 66 67