Parietal and premotor cortex regions are serious contenders for bringing motor intentions and motor responses into awareness. We used electrical stimulation in seven patients undergoing awake brain surgery. Stimulating the right inferior parietal regions triggered a strong intention and desire to move the contralateral hand, arm, or foot, whereas stimulating the left inferior parietal region provoked the intention to move the lips and to talk. When stimulation intensity was increased in parietal areas, participants believed they had really performed these movements, although no electromyographic activity was detected. Stimulation of the premotor region triggered overt mouth and contralateral limb movements. Yet, patients firmly denied that they had moved. Conscious intention and motor awareness thus arise from increased parietal activity before movement execution.
Movement intention after parietal cortex stimulation in humans.
by Michel Desmurget, Karen T. Reilly, Nathalie Richard, Alexandru Szathmari, Carmine Mottolese and Angela Sirigu
http://www.socialbehavior.uzh.ch/teaching/semsocialneurosciencespring09/desmurget_2008_science_intentionawareness.pdf
Premotor and parietal responsive sites shown after registration of the individual MR image to the MNI template. Left stimulations have been reported on the right hemisphere. Colored areas define the anatomical boundaries of BA 40 (yellow), BA 39 (orange), and BA 6 (blue).
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脳のある場所 A を刺激すると、手や腕や顔など、からだの一部が動く (Unconscious movement)。
脳の他の場所 B を刺激すると、手や腕や顔など、からだの一部を動かしたいという意思が電気刺激として生じる (Conscious motor intention)。その刺激が A に伝えられると、からだが動く。
B を強く刺激し、からだの一部を動かしたいという意思を大きく生じさせ、その意思を A に伝えないと、からだは動かないのに、あたかも動いたかのように感じる。脳は動いたと信じる。
「動きたいと感じること」と「動くこと」は、脳の別々の場所が司る、それぞれ別の現象であり、また、「動くこと」と「動いたと感じること」も別々のことなのだ。