Abstract
Detecting changes in the visual environment is crucial for normal behavior and is a central element of most spatial attention tasks. The behavioral relevance of changes, and deciding which action should follow, also depends on the context. Here we investigated how neuronal activity in the caudate nucleus, one of the major input structures of basal ganglia, is related to the evaluation of stimulus changes during an attention task. We examined the responses of caudate neurons while a rhesus macaque performed a motion-change detection task. While fixating centrally, a spatial cue was flashed centered on the response field of the neuron or in the opposite hemifield. Two motion patches were then presented – one inside and one outside the neuron's response field. In some trials, the cued motion patch changed direction, and the monkey had to release the joystick within 700 ms to be rewarded. In other trials, the direction change happened at the non-cued location and the animal was rewarded for not releasing the joystick. We recorded from 83 medium spiny neurons in the caudate during the task. A subset of neurons showed significantly elevated activity time-locked to the motion-direction change, indicating the presence of a change-detection signal. This activity was not simply a visual response, because activity was significantly higher when the monkey responded correctly to the change by releasing the joystick (hits) than when he mistakenly failed to release (misses). Moreover, the modulation was correlated with reaction times – it started earlier when the animal responded more rapidly to the motion change. These results show that neurons in the caudate exhibit activity related to behaviorally relevant visual changes. The finding that this activity depends on the behavioral context and the animal's performance suggests that the caudate nucleus could form a functional bottleneck during spatial attention tasks.
Meeting abstract presented at VSS 2014