, 2009 and Tkach et al , 2007) Monkeys were trained to perform p

, 2009 and Tkach et al., 2007). Monkeys were trained to perform planar movements in order to move a cursor to randomly positioned targets presented visually on a horizontal screen. During active performance the cursor’s position was dictated by the endpoint of a two-link exoskeletal robot moved by the monkey’s arm. The cursor movements and accompanying targets were recorded and subsequently replayed to the animal during the observation phase providing the same visual stimulation as active performance. We required the monkeys to voluntarily maintain the position of

their arm in a fixed posture during observation Lapatinib mouse to eliminate the effects of arm movements on the neural activity measured in MI. We found a tremendous amount of heterogeneity when examining the responses of individual neurons during active performance and observation. The firing rate profiles of some neurons exhibited noticeable differences under the two conditions (Figure 3A) while others modulated similarly in the two tasks (Figure 3B). Most surprising was a group of cells whose firing rate

was modulated during action observation but did not discharge in response to active movement of the limb (Figure 3C). While some neurons exhibited significant mutual information between spiking activity and cursor direction during active performance but not during observation (Figure 3D), a number of neurons showed significant mutual information during observation XAV-939 ic50 (Figure 3E), these and, in some cases, there was significant mutual information only during observation (Figure 3F). This analysis provided evidence that MI may be a member of this putative “mirror” neuron system. Mutual information estimates indicated that neural modulation led cursor movement for both voluntarily executed movement and passively observed cursor movement. This prospective activity during observation in MI is consistent

with a role in the mental rehearsal of action and is similar to other reports in both PMd (Cisek and Kalaska, 2004) and MI (Dushanova and Donoghue, 2010). However, the time lag between neural activity and movement tended to be shorter for observed cursor movements (approximately 50 ms, e.g., Figures 3E and 3F) compared to overt arm movements (approximately 125 ms, e.g., Figure 3D) meaning that the neural modulation occurred closer in time to the movement itself. This decrease in lag time may reflect the change in the dynamic properties of the task between active performance and observation. That is, during active performance the motor commands issued by MI are filtered by the motor plant (e.g., transmission, muscle recruitment, and inertial delays) causing the typical delay between activity in cortex and subsequent behavior.

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