Attentional modulation of parieto-occipital cortical responses: implications for hemispatial neglect

Functional magnetic resonance imaging (tMRI) was used to examine whether pr eattentive and attentive visual processing, the cognitive psychological dic hotomy on normal vision, indeed activate the parieto-occipital systems diff erentially as suggested by recent neuropsychological research. The activati on paradigms consisted of feature detection and discrimination of line orie ntation, and visual fixation, which corresponded to preattentive, attention -requiring, and baseline conditions, respectively. The detection Versus fix ation contrast revealed activation sites in the right lateral prefrontal co rtex and bilateral occipital lobes, whereas the discrimination versus fixat ion contrast showed broader bilateral activations extending from the occipi tal lobes through the parietal lobes, pl prefrontal cortex, thalamus. basal ganglia and upper brainstem. Ln the discrimination versus detection contra st, significant activations were observed in the right superior and inferio r parietal lobules as well as in the subcortical structures. These findings were consistently demonstrated both at intra- and inter-subject levels. Th e present study provides further evidence to delineate neural substrate for the two distinct modes of visual processing and helps us to understand the neuropsychological mechanism underlying visual attention disorders. (C) 20 00 Published by Elsevier Science B.V.