Compensatory
plasticity in congenitally blind humans
Brigitte Röder¹, Helen Neville², Frank Rösler¹
(D-Marburg, USA-Oregon)
¹Experimental and Biological Psychology, Philipps-University Marburg,
Germany
²Department of Psychology, University of Oregon, Eugene, U.S.
It has been argued that the complete loss of one sensory system, as in
congenitally blind individuals, has both positive and negative effects
on the functionality of other sensory systems. On the one hand it has
been suggested that sensory loss is followed by "sensory compensation",
i.e., that the intact modalities improve in order to counteract the lost
input. On the other hand crossmodal deficits have been considered, because
some functions may only fully develop, if different modalities get the
opportunity to interact during development. The latter has, for example,
been suggested for the development of spatial representations, because
vision has been shown to tune the spatial maps of other modalities. We
evaluated these hypotheses in a number of studies in which congenitally
blind participants were compared with sighted controls in a wide variety
of perceptual and higher cognitive tasks (including sensory discrimination,
spatial orienting, imagery, memory storage and retrieval, language comprehension
with a systematic variation of semantic and syntactic processing load)
and in which both behavioral data (speed and accuracy of performance)
and brain activation indices (event-related brain potentials of the EEG,
BOLD responses of the fMRI) were collected.
Our results suggest that blind people are able to compensate for the lack
of visual input and that these improvements concern not only perceptual
but also higher cognitive functions. Moreover, our findings indicate that
in the congenitally blind both polymodal and primarily "visual"
brain regions (as the striate and extrastriate cortex) are systematically
activated by non-visual input. This indicates that "visual"
brain regions are not atrophic in blind humans but rather seem to be systematically
activated by non-visual information processing tasks. For the time being
it is, however, unknown whether these brain areas are capable of regaining
visual functions if visual input is restored after a prolonged time of
congenital blindness.
Röder, B., &
Neville, H. J. (2002). Developmental Plasticity. In: J. Grafman &
I. Robertson (Eds.), Plasticity and rehabilitation. Handbook of Neuropsychology
(Vol. 9). Amsterdam: Elsevier, in press.