Abstract
Neurons in monkey area V2 represent border ownership (BOS)(Zhou et al., J Neurosci 20:6594,2000). Here we examined the hypothesis that this representation provides a structure for “top-down” selective attention. Predictions are: BOS is represented independently of attention, BOS and top-down selection signals converge in single cells, attentional enhancement is stronger on the BOS side of the receptive field (Craft et al., this meeting). A monkey (Macaca Mulatta) was trained to discriminate between square and trapezoid, and to perform this task for one of 3 simultaneously presented figures, as specified by preceding cue. The edge of one figure was placed in the receptive field of the cell under study, and BOS selectivity was measured by placing the figure on one or the other side of the receptive field. The influence of attention was determined by comparing trials in which this figure was cued with trials in which one of the other figures was cued. Two configurations were studied. In experiment 1, the 3 figures were spatially separated. Of 191 cells tested, 123 showed a main effect of BOS, 67 showed a main effect of attention; 68 cells (36%) showed both main effects and/or interaction of the two. Attentional enhancement was stronger on the BOS side of the receptive field. In experiment 2, two figures overlapped and the occluding edge was centered in the receptive field. In this test correct BOS assignment was critical for the performance in the task. Of 95 cells, 52 showed a main effect of BOS, 44 showed a main effect of the side of attention; 46 cells (48%) showed both main effects and/or interaction of the two. In 27 of these, the preferred BOS side was also the side of the attentional enhancement and the mean degree of enhancement was 87%; in 19, attentional enhancement was on the opposite side, and the mean degree of enhancement was 31%. Thus, overall, the attentional enhancement was significantly stronger on the preferred BOS side. We conclude that V2 provides a structure for selective attention.
Supported by NIH grant EY 02966