The broad, long-term objectives of our research are to elucidate the nature of motor processing in the CNS 1) by demonstrating neural correlates of different levels of motor processing, and 2) by comparing different areas to clarify the different roles of these areas in motor control. The current proposal is based upon the results of our recent single cell recording study of rhesus monkeys performing visually-guided, delayed, tracking tasks. The activity of a significant number of cells in the supplementary motor area (SMA), motor cortex (MC) and putamen was related to the target or goal of the movement independent of the direction of limb movement and independent of the pattern of muscle activity. Our hypothesis is that this target-dependent activity is a neural representation of very high level motor processes involved in """"""""capturing"""""""" the target or goal of the movement. The goals of the present project are 1) to thoroughly characterize the nature of this high-level, target-dependent activity using a variety of paradigms, and 2) to examine the arcuate premotor area (APA) and rostral and caudal cingulate motor areas (CMAr and CMAc) in addition to the SMA and MC in order to compare and contrast these five precentral motor areas. Comparisons will be made with respect to the frequency of occurrence and timing of each type of cell activity observed. The activity of individual neurons in the SMA, APA, CMAr, CMAc and MC will be recorded in monkeys performing a variety of tasks that require them to make visually guided limb movements. These tasks are specifically designed to determine whether the activity of each cell is of the target-dependent variety, to rule out several alternative explanations for such activity, and to extend these findings to other tasks that also require the animal to capture the same visual target in quite different ways.
The specific aims are 1: To ascertain for each cell whether the activity of that cell is directional and, if so, whether that activity is related to the location of the target/goal of the movement (target-dependent activity) or to the direction of limb movement (limb-dependent activity). These paradigms will also attempt to rule out the possibility that any target-dependent activity that is observed is related to the preparation for, or execution of, saccadic eye movements. 2: To determine for each cell with target-dependent activity whether that activity is a neural correlate of spatial memory. 3: To determine for each cell with target-dependent activity whether that activity is a neural correlate of selective attention. 4: To determine whether target-dependent activity can be observed in tasks that require the animal to capture the same visual targets by using entirely different limb movements. Two different approaches will be used: 1) the animal will 'capture"""""""" the target by making relatively unconstrained reaching movements in 3-dimensional space to a touchscreen mounted on the video monitor, and 2) the animal will perform the standard tracking task using the hand ipsilateral to the recorded neuron.
|Crutcher, M D; Russo, G S; Ye, S et al. (2004) Target-, limb-, and context-dependent neural activity in the cingulate and supplementary motor areas of the monkey. Exp Brain Res 158:278-88|