Posture influences motor imagery: An fMRI study

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Posture influences motor imagery: An fMRI study
Floris P. de Lange,a,⁎,1 Rick C. Helmich,a,b,1 and Ivan Toni,a,c
aF.C. Donders Centre for Cognitive Neuroimaging, Radboud University Nijmegen, Kapittelweg 29, 6500 HB Nijmegen, The Netherlands bDepartment of Neurology, Radboud University Medical Centre Nijmegen, The Netherlands
cNijmegen Institute for Cognition and Information, Radboud University Nijmegen, The Netherlands 

NeuroImage 33 (2006) 609–617

Motor imagery is widely used to study cognitive aspects of the neural control of action. However, what is exactly simulated during motor imagery is still a matter of debate. On the one hand, it is conceivable that motor imagery is an embodied cognitive process, involving a simulation of movements of one’s own body. The alternative possibility is that, although motor imagery relies on knowledge of the motor processes, it does not entail an actual motor simulation that is influenced by the physical configuration of one’s own body. Here we discriminate between these two hypotheses, in the context of an established motor imagery task: laterality judgments of rotated hand drawings.
We found that reaction times of hand laterality judgments followed the biomechanical constraints of left or right hand movements. Crucially, the position of subjects’ own left and right arm influenced laterality judgments of left and right hands. In neural terms, hand laterality judgments activated a parieto-frontal network. The activity within this network increased with increasing biomechanical complexity of the imagined hand movements, even when the amount of stimulus rotation was identical. Moreover, activity in the intraparietal sulcus was modulated by subjects’ own hand position: a larger incongruence in orientation between the subjects’ hand and the stimulus hand led to a selective increase in intraparietal activity.
Our results indicate that motor imagery generates motor plans that depend on the current configuration of the limbs. This motor plan is calculated by a parieto-frontal network. Within this network, the posterior parietal cortex appears to incorporate proprioceptive information related to the current position of the body into the motor plan.

Keywords: fMRI; Mental rotation; Motor imagery; Action simulation; Embodied cognition

コメント：姿勢が運動イメージに影響を与えるのか？両手の位置(姿勢)を変える事でメンタルローテーション課題の反応時間と脳活動にどのような変化があるかをみた研究。結果は,現在の自己の手の位置に合った手の画像で反応時間が早くなり,対照的に自己の手の位置と異なる角度では反応時間は遅くなった.脳活動においては,反応時間が遅くなるにつれて運動イメージに関わる運動前野と頭頂葉の活性化が高まることが分かった.つまりは,生体力学的な複雑性の増加(難易度の増加,自己の手の位置と視覚刺激の手の向きの不一致の大きさ)に伴って活性化が高まったという結果.運動計画は前頭-頭頂ネットワークによって計算され、そのネットワーク内では後頭頂皮質は現在の身体位置に関する固有感覚情報を運動計画に組み込むと考えられる.

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