Attention in the ventral pathway?

Abstract

In real life, as opposed to laboratory experiments, multiple objects in the visual scene compete for attention, such that behaviourally relevant objects are processed at the expense of irrelevant objects. How this is achieved in terms of cortical activity is the topic of much current research, and the detailed map of visual areas in the macaque and their interconnections 1 Felleman D.J. Van Essen D.C. Distributed hierarchical processing in primate cerebral cortex. Cereb. Cortex. 1991; 1: 1-47 Crossref PubMed Scopus (5388) Google Scholar has aided greatly in the search for cortical regions that might have a role in visual attention. In a recent experiment, De Weerd and colleagues examined the possible role of two extrastriate visual areas, V4 and TEO, in attention 2 De Weerd P. et al. Loss of attentional stimulus selection after extrastriate cortical lesions in macaques. Nat. Neurosci. 1999; 2: 753-758 Crossref PubMed Scopus (132) Google Scholar . These two regions are part of the ‘ventral’ pathway through extrastriate cortex, which is important for object recognition in primates, although it has also been shown that responses of neurons in V4 and TEO are modulated by the attentional demands of many different visual task. De Weerd et al. tested directly the role of these areas in visual attention by making lesions in the cortex of two macaques, such that a lesion of V4 affected one quadrant of the visual field, a lesion of TEO affected another quadrant, with combined lesions of both areas affecting a third quadrant. The remaining quadrant was intact, thus serving as a control. The monkeys were trained on an orientation-discrimination task, and, in blocks of trials, were presented with grating stimuli away from the fixation point, in each of the visual quadrants in turn. In further blocks of trials, distractor discs surrounding the target grating were added to the visual display.