2013年2月19日火曜日

M1 Corticospinal Mirror Neurons and Their Role in Movement Suppression during Action Observation


Ganesh Vigneswaran, Roland Philipp, Roger N. Lemon, Alexander Kraskov
Current Biology, Volume 23, Issue 3, 236-243, 03 January 2013

一次運動野に、他者の運動を観察している際に「活動が抑制されるニューロン」と「促進されるニューロン」が存在する(後者の活動も自分で運動をしている時に比べると少ない)。一次運動野は行動観察時に自分の運動を抑制するのに関わっているのでは?

こうやって少しずつでもミラーニューロンのメカニカルな理解が進むのは本当に重要なことだと思う。

Evidence is accumulating that neurons in primary motor cortex (M1) respond during action observation [1,2], a property first shown for mirror neurons in monkey premotor cortex [3]. We now show for the first time that the discharge of a major class of M1 output neuron, the pyramidal tract neuron (PTN), is modulated during observation of precision grip by a human experimenter. We recorded 132 PTNs in the hand area of two adult macaques, of which 65 (49%) showed mirror-like activity. Many (38 of 65) increased their discharge during observation (facilitation-type mirror neuron), but a substantial number (27 of 65) exhibited reduced discharge or stopped firing (suppression-type). Simultaneous recordings from arm, hand, and digit muscles confirmed the complete absence of detectable muscle activity during observation. We compared the discharge of the same population of neurons during active grasp by the monkeys. We found that facilitation neurons were only half as active for action observation as for action execution, and that suppression neurons reversed their activity pattern and were actually facilitated during execution. Thus, although many M1 output neurons are active during action observation, M1 direct input to spinal circuitry is either reduced or abolished and may not be sufficient to produce overt muscle activity.

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