Eiichi Iwai

Neuronal activity in visual, auditory and polysensory areas in the monkey temporal cortex during visual fixation task

The activity of 252 neurons in the inferotemporal visual area TEO, the superior temporal auditory area (AA), and the superior temporal polysensory area (STP) during the performance of a visual spot-fixation task and two variations, blink and tone tests, was examined in two behaving monkeys. A considerable number of not only TEO cells (45%) but also AA (29%) and STP (34%) cells were activated during the spot-fixation task, but unresponsive to the blanking of the spot during the fixation stage in the blink test. In addition, it was found that the activity of a third of the TEO, AA and STP cells which fired during the task-start stage in the spot-fixation task was modulated by cross-interaction between spot and tone simultaneously presented in the tone test: among these, the spot-induced activity of all TEO cells was enhanced by the tone, whereas the spot-induced activity of all AA and STP cells was suppressed by the tone. These findings are discussed in relation to the process of attending selectively to a fixation-spot.

Neuronal activity in monkey visual areas V1, V2, V4, and TEO during fixation task

We analyzed 577 neurons recorded from visual areas V1, V2, V4, and the inferotemporal area (TEO) of macaque monkeys, which performed a visual fixation task and a spot-off-on (blink) test during the fixation period. Among these neurons, 35% were defined as task-related cells, because they gave responses at the task-start, fixation, or task-end periods but were unresponsive to the spot blink, which was physically identical to these stimuli. Blink-responsive cells accounted for 29% and task-unresponsive cells for 30% of the neurons. The task-related response was large and frequent in V4 (34%) and TEO (41%), but small and less frequent in V1 (31%) and V2 (27%). Other observations further demonstrated nonsensory activities in these areas: In some cells, response to the fixation spot was inhibitory, whereas light stimulation on the fovea was excitatory; some V1 and V2 cells had color-irrelevant responses, and some cells responded to the spot-off only when the monkey regarded it as a task-end cue.