Action selection in a possible model of striatal medium spiny neuron dysfunction: behavioral and EEG data in a patient with benign hereditary chorea.

Chaining or cascading of different actions and responses is necessary to accomplish a goal. Yet, little is known about the functional neuroanatomical-electrophysiological mechanisms mediating these processes. Computational models suggest that medium spiny neurons (MSNs) play an important role in action cascading, but this assumption has hardly been tested relating neuroanatomical and electrophysiological parameters in a human model of circumscribed MSN dysfunction. As a possible human model of circumscribed MSN dysfunction, we investigate benign hereditary chorea in a case-control study applying bootstrap statistics. To investigate these mechanisms, we used a stop-change paradigm, where we apply mathematical constraints to describe the degree of how task goals are activated with more or less overlap during action cascading. We record event-related potentials and analyze neural synchronization processes. The results show that MSN dysfunctions lead to deficits in action cascading processes only when two response options seek simultaneous access to response selection resources. Attentional selection processes are not affected, but processes reflecting the transition between stimulus evaluation and responding are affected. The results underline computational models of MSN functioning and show that dysfunction in these networks leads to a more parallel and hence inefficient response selection.