Abstract
While substantial task-related neural activity has been observed during motor tasks in rodent primary motor cortex and premotor cortex, the long-term stability of these responses in healthy rats is uncertain, limiting the interpretability of longitudinal changes in the specific patterns of neural activity associated with learning or motor recovery following injury. This study examined the stability of task-related neural activity associated with execution of two distinct reaching tasks in healthy rodents. A novel automated rodent behavioral apparatus was constructed and rats were trained to perform a reaching task combining a ‘gross’ lever press and a ‘fine’ pellet retrieval. In each animal, two chronic microelectrode arrays were implanted in motor cortex spanning the caudal forelimb area (rodent primary motor cortex) and the rostral forelimb area (rodent premotor cortex). We recorded multiunit spiking and local field potential activity from 10 days to 7–10 weeks post-implantation to characterize the patterns of neural activity observed during each task component and analyzed the consistency of channel-specific task-related neural activity. Task-related changes in neural activity were observed on the majority of channels. While the task-related changes in multi-unit spiking and local field potential spectral power were consistent over several weeks, spectral power changes were more stable, despite the trade-off of decreased spatial and temporal resolution. These results show that neural activity in rodent primary and premotor cortex is associated with specific phases of reaching movements with stable patterns of task-related activity across time, establishing the relevance of the rodent for future studies designed to examine changes in task-related neural activity during recovery from focal cortical lesions.
Highlights
MethodsAll procedures were approved by the University of Kansas Medical Center Institutional Animal Care and Use Committee in compliance with The Guide for the Care and Use of Laboratory Animals (Eighth Edition, The National Academies Press, 2011)
An important challenge in neuroscience is determining how the brain controls skilled forelimb movements, a topic that has important implications for motor recovery following brain injuries as well as the development of neuroprosthetic systems
To examine the neural correlates of gross and fine reaching movements, five Long-Evans rats (Rattus norvegicus) were trained to perform a novel complex reaching task utilizing a custom-designed automated behavior box while neural recordings were made from rostral forelimb area (RFA) and caudal forelimb area (CFA)
Summary
All procedures were approved by the University of Kansas Medical Center Institutional Animal Care and Use Committee in compliance with The Guide for the Care and Use of Laboratory Animals (Eighth Edition, The National Academies Press, 2011). Stability of neural correlates of rat reaching and grasping the front and back panels This placement allowed rodents to reach through the slits with the forepaw positioned towards the side of the box, while restricting the ability of rodents to reach through the slits with their opposite forepaw. The position of the lever could be adjusted, allowing the lever to pass through the slit for temporary placement inside of the box to aid in the initial shaping of behavior. A depression was made on the shelf 24 mm outside of the inside edge of the box and aligned to the inside edge of the vertical slit to ensure the consistent position of the food pellet in each trial. An LED light was used to allow us to synchronize neural activity, behavioral performance, and videos recorded from additional external video camera
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