Neurosci. Res.Suppl. 17: 236.
INTERACTIONS BETWEEN ADJACENT CELLS IN THE ANTERIOR INFEROTEMPORAL CORTEX OF THE MACAQUE: A CROSS-CORRELATION STUDY.
ICHIRO FUJITA1,2, MINAMI ITO2, KEIJI TANAKA2,3, AND KANG CHENG2
1: Precursory Research for Embryonic Science and Technologv, Research Development Corporation of Japan, 2: Laboratory for Neural Information Processing, Frontier Research Program, 3: Information Science Laboratory, RIKEN Institute, Hirosawa 2-1, Wako, Saitama 351-01, Japan
We have recently shown that the anterior two-thirds of the inferotemporal cortex (area TE) of the monkey is organized in a columnar fashion: cells responsive to similar object-features are arranged vertically throughout the thickness of the grey matter, and span 0.4 mm on average across the cortex. In this study we performed cross-correlation analysis of adjacent TE cells to assess functional interactions within a column. We made simultaneous recordings from a pair of cells with a single electrode in anesthetized (with nitrous oxide or isofluorane), immobilized monkeys (Macaca fuscata). The signal pick-up radius of electrodes similar to ours has been estimated to be 54 ~.m. Stimulus selectivity of one cell of the pairs was extensively analysed, while action potentials of both cells in the pairs were separately counted for analysis. Most cell pairs (96%) showed a peak in their cross-correlograms. The peak disappeared when correlograms were computed between spike trains of the same pair but from different stimulus presentations, indicating that the peak reflected functional connections between the pair, not coordination through the stimulus. In 75% of the cases, the peaks were symmetrical with respect to zero delay, which was indicative of mutual excitation or shared inputs. In the remaining cases, they were asymmetrical, suggesting excitation from one cell to another. The type of the peaks, either symmetrical or asymmetrical, remained unchanged during the recording periods up to 5 hrs. We suggest that similarity of neuronal selectivity within a TE column is due to common inputs from outside the column as well as synaptic interactions among constituent cells.