The activity of 330 hippocampal and inferotemporal cells was recorded while seated monkeys with fixed heads worked in a visual discrimination task. Monkeys had to move their eyes to one of five different positions to maintain gaze on an image. The image was then extinguished and the monkeys maintained a fixed gaze on the target position in darkness to obtain a reward. The five positions of image presentation were on a horizontal line, consisting of a centre position and lateral positions which were 10 and 20 degrees right and left of it.
Twenty-two per cent of single units recorded from the hippocampus showed statistically significant sensitivity to target position in complete darkness. A similar fraction (23%) was significantly affected by target position in the light. Position sensitivity was also found among cells recorded from the inferotemporal cortex. Eye position significantly influenced the activity of 19% of inferotemporal units in darkness and 28% of inferotemporal units in the light. Interestingly, the populations of cells showing position effect in the light and in darkness were independent.