The role of the subiculum within the behavioural inhibition system.

This paper summarises the picture of the subiculum presented by Gray and McNaughton [Gray JA, McNaughton N. The neuropsychology of anxiety: an enquiry into the functions of the septo-hippocampal system. Oxford: Oxford University Press; 2000]. It is a key node in their "Behavioural Inhibition System" and, as such, is embedded within a hierarchy of structures controlling anxiety that is in parallel with a separate hierarchy controlling fear. It can nonetheless be viewed as operating in a fairly simple manner. It receives information about available goals from areas that plan motor action. This is filtered by earlier elements of the essentially unidirectional hippocampal circuit that essentially block familiar and unimportant information while passing to the subiculum important information. The function of the subiculum is to compare and integrate this goal information and produce output when conflict between incompatible goals is detected. This output prevents execution of the responses that would address the conflicting goals, increases the valence of affectively negative stimuli and associations and releases external exploration and internal rumination intended to resolve the conflict. These subicular outputs are held to be computationally simple but to have complex consequences both because of the complexity of the target areas and because, in many cases, processing is recursive. It can involve multiple passages of essentially the same information round loops such as the circuit of Papez--each pass refining the solution to the original problem of conflicting goals.