COLUMNAR ORGANIZATION IN INFERIOR TEMPORAL CORTEX OF AWAKE MONKEY.

Society for Neuroscience 1996
M.Kato, T.Uka and I.Fujita

  Area TE of the monkey inferior temporal cortex has columnar organization; i.e., neurons showing similar selectivities for visual features of objects are clustered in columns interspersed among columns of neurons with different stimulus selectivities.  Evidence of this was obtained by extracellular neuronal recording and by optical imaging.  However, both types of studies were performed in anesthetized monkeys;  the columnar organization has not been demonstrated in awake monkeys.
  A Japanese macaque monkey was trained to fixate on a small spot displayed on a color LCD monitor.  During each fixation period, 3-6 different visual stimuli were sequentially presented.  Five electrode guiding tubes were implanted perpendicularly to the lateral surface of area TE, which enabled repetitive access to nearly the same electrode tracks.  First we recorded extracellular neural activities in the monkey anesthetized with N2O/O2 in order to determine track-specific stimulus features and to examine neural responses to these stimuli in addition to a fixed set of 40 stimuli.  Two weeks later, neural responses to the same stimuli were examined along the tracks in the monkey performing the fixation task.
  We recorded 62 multiple and single unit activities in each of the anesthetized and awake conditions.  Correlation coefficients of normalized response magnitude were calculated among pairs of units in the same(CCs) and different(CCd) tracks.  The average CCs in the awake condition was 0.30 while the average CCd was near 0 in both the awake(-0.001) and the anesthetized (-0.002) condition.  In the anesthetized condition, the average CCs was small (0.14) but significantly larger (p<0.001) than the average CCd.  Twenty-seven percent of the CCsfs but only 2% of the CCdfs were larger than 0.5 in the awake condition.  These results indicate a stronger correlation among cells within a vertical track than among cells in different tracks, suggesting that the neurons in area TE in the awake monkey are organized into columns.  Supported by the Uehara Memorial Foundation.


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