To select information relevant to our goals, we orient our attention
towards the objects present in our environment. Brain damage may impair these
mechanisms, thus provoking a unilateral
spatial neglect. About half of the patients with a lesion in the right
hemisphere suffer from neglect for the left side of space. They are unaware of
the left half of their environment, and have a poor functional outcome. My
research has tested several proposed explanations of neglect, and shown that
neither the loss of the left half of a cognitive representation of space, nor
the rightward shift of an egocentric frame of reference, nor an impairment in
producing arm movements toward the left can explain neglect. Instead, an
association of attentional deficits seems typical of unilateral neglect. These
deficits operate in a specific temporal sequence; an early attraction of
attention toward the right is followed by an impairment in redirecting
attention toward the left. My current research is trying to establish the
precise nature of these attentional deficits, as well as their neural bases.
Additional work on "higher level" visual processing concerns visual mental imagery, the faculty by
which we can imagine an object in its absence, and pure alexia, an acquired reading disorder by which patients lose
their ability to rapidly read words and resort to a slow, letter-by-letter
reading. My results on visual mental imagery challenged the current view that
imagery shares with vision mechanisms subserved by
early visual cortices. My research on pure alexia demonstrated the presence of
a deficit of letter identification and its relationship with word reading
problems, and highlighted the crucial role of the right hemisphere in
determining the characteristics of patients’ residual reading.