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Exp Brain Res. 2012 Jan;216(1):135-44. doi: 10.1007/s00221-011-2917-3. Epub 2011 Nov 11.

Tuning of the excitability of transcortical cutaneous reflex pathways during mirror-like activity.

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Department of Cognitive Behavioral Physiology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuouku, Chiba 260-8670, Japan.


Voluntary contraction of a muscle generates electromyographic (EMG) activity in the homologous muscle on the opposite side (mirror-like activity), not only in pathological states and in infants but also in healthy adults. Few studies have examined whether the cutaneous reflexes during the preparatory period of a reaction time task are affected by mirror-like activity. In the present study, we investigated the modulation of the cutaneous reflexes in the left first interosseous (FDI) muscle in 9 healthy subjects while they performed a quick abduction of the right index finger during a reaction time task. Cutaneous reflexes were elicited by applying non-noxious electrical stimulation to the left index finger. We found that mirror-like activity occurred in the left FDI at approximately the onset of EMG activity in the right FDI. The excitatory E2 component was selectively increased at ~75 ms after the "Go" signal, which corresponded to the onset of mirror-like activity. The inhibitory I2 (~90 ms) component was tuned consistently into excitation after the "Go" signal. These findings suggest that long latency reflexes, possibly transcortical cutaneous reflexes, are finely tuned in relation to mirror-like activity.

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