What's at the top in the top-down control of action? Script-sharing and 'top-top' control of action in cognitive experiments.

The distinction between bottom-up and top-down control of action has been central in cognitive psychology, and, subsequently, in functional neuroimaging. While the model has proven successful in describing central mechanisms in cognitive experiments, it has serious shortcomings in explaining how top-down control is established. In particular, questions as to what is at the top in top-down control lead us to a controlling homunculus located in a mythical brain region with outputs and no inputs. Based on a discussion of recent brain imaging experiments, we argue for the need to factor the interaction between the experimenter and the experimental participant into a realistic understanding of top-down control. We suggest these interactions involve a 'sharing of scripts' for perception and action that may be described as 'top-top processes.' We thereby expand the understanding of the homunculus to include elements of social cognition. This conceptual reconfiguration may grant some sort of asylum for a--not very omnipotent--homunculus. Copyright 2004 Springer-Verlag