Pyramidal tract neurons (PTNs) within macaque rostral ventral premotor cortex (F5) and primary motor cortex (M1) provide direct input to spinal circuitry and are critical for skilled movement control. Contrary to initial hypotheses, they can also be active during action observation, in the absence of any movement. A population-level understanding of this phenomenon is currently lacking. We recorded from single neurons, including identified PTNs, in M1 (n=187), and area F5 (n=115) as two adult male macaques executed, observed, or withheld (NoGo) reach-to-grasp actions. F5 maintained a similar representation of grasping actions during both execution and observation. In contrast, although many individual M1 neurons were active during observation, M1 population activity was distinct from execution, and more closely aligned to NoGo activity, suggesting this activity contributes to withholding of self-movement. M1 and its outputs may dissociate the initiation of movement from the representation of grasp in order to flexibly guide behaviour.
Matlab codes and data to reproduce Figures 5-7 and Figure 9 are publicly available at https://github.com/sjjerjian/grasp-mirror-neurons.
- Alexander Kraskov
- Steven Jack Jerjian
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: All procedures were designed to minimize discomfort and pain of the animals and were approved by the local Animal Ethics and Welfare Committee and carried out in accordance with the UK Animals (Scientific Procedures) Act (Project Licence 708254). Experiments involved two adult purpose-bred male monkeys (Macaca mulatta, M48 and M49, weighing 12.0kg and 10.5kg, respectively). The monkeys were single-housed based on veterinary advice, in a unit with other rhesus monkeys, with natural light and access to an exercise pen and forage area. Both monkeys gained weight regularly throughout the procedure.
- Jörn Diedrichsen, University of Western Ontario, Canada
© 2020, Jerjian et al.
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