YAMAGUCHI Kiyoko Tokyo Metropolitan Institute for Neuroscience, Dept. of Behavioral Physiology, Research Scientist, 東京都神経科学総合研究所, 研究員 (10073090)
OSAWA Yasutaka Tokyo Metropolitan Institute for Neuroscience, Dept. of Behavioral Physiology, Research Scientist, 東京都神経科学総合研究所, 研究員 (40100135)
|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 2005 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 2004 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 2003 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 2002 : ¥1,700,000 (Direct Cost : ¥1,700,000)
To clarify roles of perirhinal cortex in memory and learning, especially in relational or configural ones, effects of perirhinal cortex lesion on delayed matching-to-sample tasks (DMS) with small (3 stimuli) and large (300 stimuli) sets of stimuli (DMS-S and DMS-L, respectively) and transverse patterning task (TPT) were examined using 6 macaque monkeys. Preoperatively, monkeys were trained on DMS-L and DMS-S. Postoperatively, DMS-S was first tested. Thereafter, DMS-L was given to the monkeys. Last, TPT and its control task, concurrent discrimination task (CDT), were trained. As a result, no impairment was seen in relearning of DMS-S or DMS-L or in their delay tests with 30, 60 and 120 sec. Perirhinal cortex lesion, however, produced a severe impairment in transverse patterning task without impairment in CDT. Our monkeys with perirhinal cortex lesion were not impaired in this task, despite that It is well-established that perirhinal cortex is critically involved in DMS-L. It might be possible that they resolved DMS-L by using their learned DMS-S strategy which remained intact.
The present results are sharply contrasted with our previous study demonstrating that monkey brain ischemia, which caused cell loss in the hippocampus, produced impairment in DMS-S, but not in DMS-L, TPT or CDT. It has been controversial whether TPT should be regarded as a configural task or as a relational one. However, perirhinal cortex lesion did not impair in DMS-S which might be regarded as a relational task, but in TPT. Thus, the present study suggests that perirhinal cortex might be involved in configural association, but not in relational association.