Cortical interactions involved in the production of hand movements

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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 some cortical areas were added or expanded to increase the repertoire and complexity of hand movements. We currently have limited understanding of how the connections of these specialized cortical areas are organized within M1 and how they participate in the production of dextrous movements. Our LONG-TERM OBJECTIVE is to understand the role of cortical interactions for the generation of hand movements. Our previous experiments in capuchin monkeys (sapajus apella) 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 physiological interactions between distant sensorimotor cortical areas involved in hand movements and M1, 2) the dynamic range of modulatory effects from these distant areas during different phases of movement preparation and production and 3) pattern of cortical connections and interactions of M1 with additional areas of the parietal cortex. In AIM 1, we will use chronic electrode arrays in sedated monkeys to investigate the topographic organization of cortical interactions in M1 with invasive stimulation protocols. We will study how conditioning stimulation applied in a distant cortical area (i.e., premotor ventral (PMv) and premotor dorsal (PMd) or area 5) affect the discharge pattern and the outputs of subpopulations of neurons across M1. In AIM 2, we will use chronic electrode arrays in awake monkeys to deliver conditioning stimulation at different moments while monkeys perform various grasping movements. We will study how the stimulation affects the discharge pattern of subpopulations of neurons across M1. In AIM 3, we will use neuroanatomical tracing techniques to study the pattern of cortical connections of additional somatosensory areas of the parietal cortex with 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. These 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 will uniquely contribute to a vibrant field of research.