Integrative and Molecular Approach to Brain Function
Proceedings of the Uehara Memorial Foundation Symposium on Integrative and Molecular Approach to Brain Function, Tokyo, 25-27 June 1996 : pp.147-155

Functional architecture and synaptic plasticity in the monkey inferior temporal cortex

Ichiro Fujita, Makoto Kato, Yusuke Murayama and Takanori Uka
Department of Cognitive Neuroscience, Osaka University Medical School, Osaka, Japan

Area TE of the inferior temporal cortex in the monkey has a columnar organization. Most neurons in the TE respond selectively to particular visual features of objects, and those with similar stimulus preferences are clustered in vertical arrays roughly 0.5 mm in width. Evidence for the columnar organization has been obtained in anesthetized monkeys, but is now extended by experiments in awake monkeys. Columns interact with each other via intra-areal horizontal axons which connect laterally displaced sites in the TE. High-frequency electrical stimulation of horizontal axons evokes long-term potentiation (LTP) of synaptic transmission efficacy mediated by this axon system. In the primary visual cortex, however, an identical stimulus protocol produced long-term depression in the same fiber system. The success of evoking LTP in the TE in vivo will allow us to investigate in future studies whether and how LTP affects stimulus selectivity of TE neurons and the functional columnar organization of this area. The results also suggest that visual cortical areas are diverse not only in their anatomical structures and receptive field properties, but also in their synaptic plasticity.