抄録
Neurons with similar response specificity cluster in columns in cerebral cortices. This structure is considered to be a universal characteristic of cortical areas. However, modular organizations such as columns are not fully characterized in higher association cortices, including monkey inferior temporal (IT) cortex. In the present study, we used intrinsic signal imaging and voltage sensitive dye imaging to explore modular organizations in IT, and extracellular recordings to understand functional structures at cellular levels in IT cortex. Intrinsic signal imaging revealed that object images activate multiple spots in IT cortex. Each spot (diameter, 0.5+/-0.13 mm) was specific to a particular visual feature included in the object images. On the other hand, voltage sensitive dye imaging revealed that a region 5-10 times larger than the spots was specifically activated by a set of the object images. Taking into account that intrinsic signals emphasize spiking activity and that voltage sensitive dye signals emphasize synaptic potentials, these results suggest that there are modules in different scales that are distinguished by measures of neural activity. In addition to these results, extracellular recordings from individual cells showed that object selectivity of nearby cells within a spot was similar enough to distinguish cells in one spots from the other. Among the cells in a spot, however, object selectivity was not exactly the same. Based on these results, we proposed that there is a hierarchical modular organization where levels of the hierarchy are different in scales and probably in stimulus selectivity. [Jpn J Physiol 54 Suppl:S48 (2004)]
