The proposed experiments investigate the neural mechanisms of rapid targeted responses of the limb and neck in the cat. Three groups of experiments are planned and are based on results obtained in the current period. First, we will ascertain the neural pathways that are responsible for transferring information from the target to the brain structures responsible for specifying trajectory parameters. This will be achieved by determining deficits in performance of a tracking task after reversible inactivation of several candidate pathways by injection of local anesthetics and other agents which block conduction or transmission of neural impulses. The primary question is to ascertain whether the processing of target information is mediated by the sensory cortical area or whether subcortical processing suffices. Each animal will serve as its own control and deficits produced by inactivation of different pathways will be compared in the same animal. Second, we will also define the changes in the preparation and execution of targeted responses following selective inactivation of two subregions of the motor cortex. [This part of the study, seeks to determine whether predictions deriving from our recent anatomical and physiological studies can be corroborated.] This experiment seeks principally to determine whether the prediction that the only rostral subregion of the arm area is concerned with response initiation. The third goal of the proposed work is to define the contributions of reticulospinal and other reticular neurons in the initiation and control of targeted neck and arm responses. Through single neuron recordings in the behaving animal we hope to ascertain the role of this neuronal system in the execution of the behaviors.
