words, invoking their meaning, and constructing the appropriate 

 context. But we must bear in mind that this is possible only if we 

 are sufficiently adept at using language. When learning to speak or 

 read, we had to concentrate on every phoneme, and subsequently 

 on every word. 



A vital factor in our ability to manipulate and modify sequences 

 of muscular movements — executed or merely imagined — is what 

 Alan Baddeley and Graham Hitch (1974) referred to as working 

 memory. The system has to be able to hold different possible courses 

 of action in a temporary memory, while their relative merits are 

 compared, and it must do so in relation to the prevailing external 

 and internal conditions. One could loosely compare this mechanism 

 with writing various alternatives on a blackboard, and then gradually 

 eliminating the less-promising candidates, until a single possibility 

 remained. Patricia Goldman-Rakic (1992) has made a strong case 

 for such working memory being located in the prefrontal cortex, 

 positioned at the very front of the brain. This region is known to 

 have connections with many other brain regions, so it is ideally 

 situated for the role of marshalling, organizing and coordinating the 

 patterns of nerve signals that dictate the various muscle-directing 

 scenarios. It is also significant that Joaquin Fuster (1985) has found 

 that the persistence time of neural signals is longer in the prefrontal 

 cortex than elsewhere. 



One should not overlook the multiplicity of our behavioral modes; 

 we underestimate the underlying complexity when we merely dis- 

 tinguish between consciousness and unconsciousness. The full in- 

 ventory comprises the following: we can act without thinking, think 

 without acting, act while thinking about that act, and act while think- 

 ing about something else. And although we might take it for granted, 

 it is worth contemplating the fact that thought always has the greater 

 priority; it is impossible to think about one thing, simultaneously do 

 something else, and focus one's attention on the latter. Our thoughts 

 are perforce always at center stage. 



What aspects of the system's anatomy and physiology permit such 

 a wealth of behavioral options? I suspect (Cotterill. 1998, 2001b) 

 that a major role is played by the heterogeneity of structure found 

 by Ann Graybiel and Clifton Ragsdale, Jr. (1978) in the striatum 



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