It is suggested that consciousness is primarily associated not with stimuli and perception, as commonly supposed, but with movement and responses. Consciousness of stimuli arises in situations in which possible movements are planned, or in which information must be actively acquired rather than passively registered, and may or may not require overt movements to be performed. By emphasizing response, this formulation provides a simple explanation for the perceived unity of consciousness: though stimuli can be diverse, with independent components, movements must necessarily be coordinated. Therefore, if we are to look for a ‘site’ for consciousness, it is likely to be in a region such as the anterior cingulate that is neurally close to the higher motor hierarchical levels, and also accessible both to real sensory feedback and also to virtual feedback derived through mechanisms of efference copy from actual or proposed motor commands. It is suggested that synchrony of arrival of such information may be an important prerequisite of this unity, and that on this basis such a ‘master node’ might be expected to be temporally ‘equidistant’ from each of these sources; this may well be true of the anterior cingulate, but no doubt also of other structures.
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