Effects of Attention on Orientation-Tuning Functions of Single Neurons in Macaque Cortical Area V4

TLDR

The study examined how attention affected the orientation tuning of 262 isolated neurons in extrastriate area V4 and 135 neurons in area V1 of two rhesus monkeys. The researchers recorded neuronal responses during a delayed match‑to‑sample task in which monkeys attended or ignored stimuli presented in the receptive field, enabling orientation‑tuning curves to be constructed from attended versus unattended states and fitted with Gaussians across twelve orientations. Attention increased V4 and V1 neuronal responses (median 26 % and 8 % respectively) without altering orientation‑tuning width, consistent with a multiplicative scaling of driven responses and no systematic change in undriven activity.

Abstract

We examined how attention affected the orientation tuning of 262 isolated neurons in extrastriate area V4 and 135 neurons in area V1 of two rhesus monkeys. The animals were trained to perform a delayed match-to-sample task in which oriented stimuli were presented in the receptive field of the neuron being recorded. On some trials the animals were instructed to pay attention to those stimuli, and on other trials they were instructed to pay attention to other stimuli outside the receptive field. In this way, orientation-tuning curves could be constructed from neuronal responses collected in two behavioral states: one in which those stimuli were attended by the animal and one in which those stimuli were ignored by the animal. We fit Gaussians to the neuronal responses to twelve different orientations for each behavioral state. Although attention enhanced the responses of V4 neurons (median 26% increase) and V1 neurons (median 8% increase), selectivity, as measured by the width of its orientation-tuning curve, was not systematically altered by attention. The effects of attention were consistent with a multiplicative scaling of the driven response to all orientations. We also found that attention did not cause systematic changes in the undriven activity of the neurons.