17Following injury to motor cortex, reorganization occurs throughout spared brain regions and is 18 thought to underlie motor recovery. Unfortunately, the standard neurophysiological and 19 neuroanatomical measures of post-lesion plasticity are only indirectly related to observed 20 changes in motor execution. While substantial task-related neural activity has been observed 21 during motor tasks in rodent primary motor cortex and premotor cortex, the long-term stability of 22 these responses in healthy rats is uncertain, limiting the interpretability of longitudinal changes in 23 the specific patterns of neural activity during motor recovery following injury. This study 24 examined the stability of task-related neural activity associated with execution of reaching 25 movements in healthy rodents. Rats were trained to perform a novel reaching task combining a 26 'gross' lever press and a 'fine' pellet retrieval. In each animal, two chronic microelectrode arrays 27 were implanted in motor cortex spanning the caudal forelimb area (rodent primary motor cortex) 28 and the rostral forelimb area (rodent premotor cortex). We recorded multiunit spiking and local 29 field potential activity from 10 days to 7-10 weeks post-implantation to characterize the patterns 30 of neural activity observed during each task component and analyzed the consistency of channel-31 specific task-related neural activity. Task-related changes in neural activity were observed on the 32 majority of channels. While the task-related changes in multi-unit spiking and local field 33 potential spectral power were consistent over several weeks, spectral power changes were more 34 stable, despite the trade-off of decreased spatial and temporal resolution. These results show that 35 rodent primary and premotor cortex are both involved in reaching movements with stable 36 patterns of task-related activity across time, establishing the relevance of the rodent for future 37 studies designed to examine changes in task-related neural activity during recovery from focal 38 cortical lesions. 39
Introduction 40An important challenge in neuroscience is determining how the brain controls skilled 41 forelimb movements, a topic that has important implications for motor recovery following brain 42 injuries as well as the development of neuroprosthetic systems. Along with non-human primates, 43 rodents are valuable models for examining the neurophysiological basis of motor control. In 44 particular, rodents can learn to perform a wide variety of motor tasks, including: lever press/pull 45 movements with complex timing [1], 2D center-out joystick movements [2], single-pellet reach-46 to-grasp food retrievals [3, 4], and even control of brain-computer interface systems with neural 47 substantial task-related neural activity during the performance of a reaching task [7]. In part, this 63 may be due to the dense reciprocal connectivity between the two regions [13], which depending 64 on the relative timing of excitation in each area, allows RFA and CFA to modify the outpu...