... Pinel (2000) notes that it shares with the basal ganglia motor system, the fact that , "It is not entirely clear exactly which structures should be included in them, or even whether it is appropriate to view them as unitary systems" [p74]. That said however, continued research in this area, involving increasingly sophisticated techniques and ever more ingenious experimental paradigms, has resulted in a growing sophistication of our understanding of the structures and circuits implicated. As noted previously, it was Papez was the first to suggest the existence of such a system. His conceptualization implicated the four basic structures of the hypothalamus (and mamillary bodies), the anterior thalamic nucleus, the cingulate gyrus and the hippocampus. Extending this conceptualization, MacLean incorporated inter alia, the structures of the orbito-frontal cortex, the para-hippocampal gyrus, the amygdala, the medial thalamic nucleus, the septum, the olfactory cortex, the insula, and the fornix. MacLean (1985) ...

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