|Budget Amount *help
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2001: ¥2,700,000 (Direct Cost: ¥2,700,000)
Conventional lesion studies have suggested that the posterior inferotemporal cortex (area TEO) is more closely involved in pattern perception, whereas the anterior inferotemporal cortex (area TE) is mainly involved in visual memory in the monkey. However, recent neuron studies have shown that area TE neurons, as well as area TEO neurons, have pattern selectivity, and, more important, tend to prefer more complex patterns compared with area TEO neurons. Moreover, an anatomical finding suggests the participation of area TEO to visiual memory. Considering these findings, we reexamined the functions of the inferotemporal subdivisional areas. The main findings are as follows.
1)Lesion effects of gyral area TEO and anterior area TE were examined on simple and complex pattern discrimination tasks. In the simple pattern discrimination tasks, the TEO lesion produced significantly severer impairments than the anterior TE lesion. On the other hand, in the complex pattern discrimination tasks, no si
gnificant difference was found between the effects of the TEO and anterior TE lesions. These findings suggest that conventional lesion studies failed to observe significant pattern discrimination deficits following TE lesions because they employed rather simple patterns in the pattern discrimination tasks, and area TE participates in processing features of complex patterns.
2)Lesion effects of gyral area TEO, anterior area TE, and new TEO, in which the ventromedial portion of the posterior inferotemporal cortex was ablated adding to gyral TEO, were examined on a task in which monkeys had to select delayed matching-to-sample or nonmatching-to-sample strategy, depending on whether the sample objects were baited or not. The new TEO lesion as well as the anterior TE lesion produced significant impairments in this task but gyral TEO lesions did not. The present findings suggest the involvement of the posterior inferotemporal cortex, in particular, its ventromedial portion, in mediating recognition and association memory. Less