Project 5 - Premotor Interactions in Motoric Choices: The behavioral act of reaching typically begins with a coordinated eye-head gaze shift. As gaze turns, one or the other hand reaches out to an available target. When multiple potential targets are present, we have observed previously that the direction of the initial gaze shift (right or left), the hand used (right or left), and the target taken (right or left) all are correlated with one another. Here we will study the neural interactions between the head and arm representations of the ventral premotor cortex (PMv) that underlie these correlations. We will test the general hypothesis that the PMv participates in mediating these correlations between gaze, hand and target with four Specific Aims. First, we will test the hypothesis that requiring the monkey to lateralize each of these three variables?gaze, hand and target?to one side or the other, biases the monkey's choices of the other two variables. Second, the hypotheses that gaze direction biases choices of which hand to use, and alternatively that hand preference biases choices of gaze direction, will be examined by inactivation or stimulation of the superior colliculus or M1 upper extremity representation, respectively. Third, the hypothesis that the lateral head representation in PMv participates in control of the head movement component of coordinated eye-head gaze shifts will be tested by recording PMv neurons during both an 8-direction target-acquisition task and a lateralized choice task. We will determine whether variation in PMv neuron activity during the choice task can be attributed simply to effector selectivity, directional tuning and kinematic relationships of the neuron, or whether choice-related discharge is present as well. Fourth, the hypothesis that neural interactions between the PMv head and arm representations participate in mediating gaze/hand and gaze/target correlations will be examined by recording local field potentials and single neuron activity simultaneously in the PMv head and arm representations, by recording in one while microstimulating the other, and by recording in one while inactivating the other. By examining interactions that underlie correlations between the simple choices of which way to look, which hand to use, and which food morsel to take, these studies will complement other programmatic studies of cortico-subcortical interactions in decision making and gaze control.
