***Warning..... This is highly speculative****
My old advisor, Darryl Neill, used to talk about cortical and basal ganglia mechanisms as being involved in the "contemplation" of movement, and of course one could also use the term motor planning. The nucleus accumbens is a part of the circuitry that links prefrontal cortex with pallidal areas and thalamus. In view of the notion that prefrontal cortex is involved in planning and organization of behavior, I wonder if one of the roles of the accumbens is to feed information about the propensity for spending energy (or overcoming constraints) into the prefrontal cortex, and then cortical mechanisms utilize this information in formulating motor plans and response selection strategies. Thus, some of the behavioral effects of accumbens DA depletions represent the result of an alteration of prefrontal function due to a loss of this type of input.