(2000) has remarked that "there is strong evidence that the cere- 

 bellum in humans is activated in anticipation of somatosensory 

 events, even when these events do not require overt responses." And 

 Masao Ito (1993) had noted several years earlier that the cerebellum 

 exercises control over both overt movement and thought in essen- 

 tially the same manner. Turning to the question of drive, creatures 

 able to respond appropriately to a variety of different internal im- 

 pulses must have a sufficiently differentiated control mechanism. In 

 our own species and others close to us, this control is provided by 

 the basal ganglia (indicated by SNpc, striatum, nucleus accum- 

 bens, globus palidus Internal, globus palidus External, substantia 

 nigra Pars reticulata, and subthalamic nucleus in fig. 2). 



But possession of these essentially autonomous mechanisms is not 

 sufficient to produce consciousness. Sverre Sjolander (1997) has de- 

 scribed the fragmentary nature of the typical snake's behavioral 

 mechanisms, and chronicled its ability to salvage a successful ex- 

 istence despite its various senses not functioning cooperatively. The 

 inability of those senses to get their act together is known as the 

 binding problem, and if that problem has not been overcome in a 

 species, consciousness appears to be impossible (Cartmill, 1996). I 

 have suggested (Cotterill, 1995; 1996; 1997) that the problem is 

 absent from our systems, and from those of species close to us, 

 because all nerve signals converge on the brain's muscle-directing 

 region (as distinct from the muscle-activating region, which in mam- 

 mals is known as the primary motor area, indicated by motor cor- 

 tex in fig. 2). That region (which comprises the premotor area and 

 the supplementary motor area — denoted by pma and sma, respec- 

 tively, in fig. 2) functions as the source of the feedback signals — 

 known as efference copy signals — dispatched around the above- 

 mentioned closed loop. Shigeo Kinomura, Jonas Larsson, Balazs 

 Gulyas and Per Roland (1996) have used positron emission tomog- 

 raphy to detect the activity in the loop's various components during 

 visual attention in humans. Another component in that loop is the 

 nucleus reticularis thalami. which Charles Yingling and James Skin- 

 ner (1977) have argued functions as a selective gate for signals 

 passing from the thalamus to the cerebral cortex. And the nucleus 

 reticularis thalami is itself under the control of the anterior cingulate 



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