抄録
Extracellular recordings in inferotemporal (IT) cortex suggest that there are columnar organizations in terms of the optimal stimuli for individual neurons (Fujita, et al., 1992). This finding is consistent with optical imaging experiments showing that a visual stimulus elicits a localized activation of the spots in IT cortex (Wang, et al., 1996, 1998). However, it is also known that object selectivity of nearby cells is not necessarily the same. Thus, our understanding of columnar organizations in IT cortex is still partial. Here, we identified active spots revealed by optical imaging, and then recorded single unit activities and multiple unit activities (MUAs) from these spots. To quantify the similarity of object selectivity, we calculated correlation coefficients of responses to 100 object stimuli. We found that only 30% of pairs of nearby single units showed significant correlation in object selectivity. However, many pairs of MUAs (63%) showed significant correlation in object selectivity. The difference in number of significant pairs suggests (1) that there is a common property among single cells, and (2) that averaging of responses of individual cells, such as MUA, decreases cell-to-cell variability in object selectivity and disclose common property among cells within a spot. In fact, when all MUAs in a spot were averaged, single unit activity and the averaged MUA showed significant correlation in object selectivity in 63% of single cells within the spot. However, we could not find such significant correlation between the averaged MUA of a spot and single unit activity recorded from outside of the spot. [J Physiol Sci. 2006;56 Suppl:S88]
