Biology subjects

Jerjian, S. J.

Publications and source records attributed to Jerjian, S. J..

2 recordsLinked to original sources

bioRxiv2019

Movement initiation and grasp representation in premotor and primary motor cortex mirror neurons

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, but surprisingly, can also be active during passive action observation. We recorded from single neurons, including identified PTNs in the hand and arm area of primary motor cortex (M1) (n=189), and in premotor area F5 (n=115) of two adult male macaques, while they executed, observed, or simply withheld (NoGo) reach-to-grasp and hold actions. We found that F5 maintains a more sustained, similar representation of grasping actions during both execution and observation. In contrast, although some M1 neurons mirrored during the grasp and hold, M1 population activity during observation contained signatures of a withholding state. This suggests that M1 and its output may dissociates signals required for the initiation of movement from those associated with the representation of grasp in order to flexibly guide behaviour. Significance StatementVentral premotor cortex (area F5) maintains a similar representation of grasping actions during both execution and observation. Primary motor cortex and its outputs dissociate between movement and non-movement states.

bioinformatics↗

bioRxiv2019

Time-dependent modulation of spinal excitability during action observation in the macaque monkey

Neurons in the primate motor cortex, including identified pyramidal tract neurons projecting to the spinal cord, respond to the observation of others actions, yet this does not cause movement in the observer. Here, we investigated changes in spinal excitability during action observation by monitoring short latency electromyographic responses produced by single shocks delivered directly to the pyramidal tract. Responses in hand and digit muscles were recorded from two adult rhesus macaques while they performed, observed or withheld reach-to-grasp and hold actions. We found modest grasp-specific facilitation of hand muscle responses during hand shaping for grasp, which persisted when the grasp was predictable but obscured from the monkeys vision. We also found evidence of a more general inhibition before observed movement onset, and the size of this inhibition effect was comparable to the inhibition after an explicit NoGo signal. These results confirm that the spinal circuitry controlling hand muscles is modulated during action observation, and this may be driven by internal representations of actions. The relatively modest changes in spinal excitability during observation suggest net corticospinal outflow exerts only minor, sub-threshold changes on hand motoneuron pools, thereby preventing any overflow of mirror activity into overt movement.

animal behavior and cognition↗