Affiliations: Department of Medical Neurobiology, Institute for
Medical Research Israel-Canada (IMRIC) and Interdisciplinary Center for Neural
Computation (ICNC), Hebrew University of Jerusalem, Jerusalem, Israel | Neurobiology Department, Life Science Institute and
Interdisciplinary Center for Neural Computation, Hebrew University, Jerusalem,
Israel | Department of Neurobiology, Weizmann Institute of
Science, Rehovot, Israel
Note: [] Corresponding author: Amir Amedi, Department of Medicine
Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and
Interdisciplinary Center for Neural Computation (ICNC), Hebrew University of
Jerusalem, Jerusalem 91220, Israel. Tel.: +972 2 675 7259; Fax: +972 2 675
8602; E-mail: [email protected]; Website: http://brain.huji.ac.il
Abstract: Purpose: Recent studies show evidence of multisensory representation
in the functionally normal visual cortex, but this idea remains controversial.
Occipital cortex activation is often claimed to be a reflection of mental
visual imagery processes triggered by other modalities. However, if the
occipital cortex is genuinely active during touch, this might be the basis for
the massive cross-modal plasticity observed in the congenitally blind. Methods: To address these issues, we used fMRI to compare patterns of
activation evoked by a tactile object recognition (TOR) task (right or left
hand) in 8 sighted and 8 congenitally blind subjects, with several other
control tasks. Results: TOR robustly activated object selective regions
in the lateral occipital complex (LOC/LOtv) in the blind (similar to the
patterns of activation found in the sighted), indicating that object
identification per se (i.e. in the absence of visual imagery) is sufficient to
evoke responses in the LOC/LOtv. Importantly, there was negligible occipital
activation for hand movements (imitating object palpations) in the occipital
cortex, in both groups. Moreover, in both groups, TOR activation in the
LOC/LOtv was bilateral, regardless of the palpating hand (similar to the lack
of strong visual field preference in the LOC/LOtv for viewed objects). Finally,
the most prominent enhancement in TOR activation in the congenitally blind
(compared to their sighted peers) was found in the posterior occipital cortex. Conclusions: These findings suggest that visual imagery is not an
obligatory condition for object activation in visual cortex. It also
demonstrates the massive plasticity in visual cortex of the blind for tactile
object recognition that involves both the ventral and dorsal occipital areas,
probably to support the high demand for this function in the blind.
