The effect of cortical interactions on motor output by the primary motor cortex

点击翻译按钮获取中文摘要

The primate sensorimotor network is composed of several specialized cortical areas that can interact with the primary motor cortex (M1) to produce movements. During evolution, it appears that specialized cortical areas were added or expanded to support an increase of the repertoire and complexity of hand movements. We currently have limited understanding of how the connections among these specialized cortical areas are organized within M1 and how they participate in the production of motor outputs. Our LONG-TERM OBJECTIVE is to determine the role of cortical interactions in the generation of arm and hand movements. Our previous experiments in capuchin monkeys (Cebus) have shown that premotor areas and area 5 have preferential connections with largely segregated subregions in the hand representation of M1. These results change the way we view M1 and suggest that it is composed of several modules, each part of a specific cortical network. In this cycle of funding, we pursue our research on these exciting findings. Our SPECIFIC OBJECTIVES are to study 1) the topographic organization of cortical interactions of premotor areas and area 5 with M1, 2) the relative contribution of the different pathways through which cortical areas can modulate M1 outputs and 3) the cortical inputs and interactions of M1 with additional areas of the parietal cortex. In AIM 1, we will use chronic electrode arrays in awake monkeys to investigate the topographic organization of cortical interactions in M1 with paired-pulse stimulation protocols. In these protocols, a conditioning stimulus is applied in a cortical area prior to a test stimulus in M1 and the effect of the stimulation is quantified in EMG signals. We will study how stimulation of the premotor dorsal and ventral cortex (PMd and PMv) and area 5 specifically affect the outputs of subpopulations of neurons across M1. In AIM 2, in awake monkeys with chronic electrode arrays, we will use inactivation techniques to study how cortical areas use different parallel output pathways (corticocortical, corticorubral and corticoreticular) to modulate M1’s outputs and contribute to the production of hand movements. In AIM 3, we will use neuroanatomical tracing techniques to study the specific pattern of cortical inputs from multiple somatosensory areas of the parietal cortex to M1. In acute terminal preparations, we will study the general pattern of modulatory effects of these somatosensory areas on M1’s outputs with paired-pulse stimulation protocols. The projects take advantage of invasive approaches to address pressing gaps in our knowledge of cortical interactions that cannot be answered with non-invasive approaches such as transcranial magnetic stimulation (TMS) in humans. The data will greatly contribute to our understanding of the complex cortical network that supports hand movements in primates and uniquely contribute to a vibrant field of research with a wide interest.