Figure 5.

Simplified model of impairment of information flow between the prefrontal and oculomotor loops. Top, In the normal situation, there is mixing in the associative areas of striatum (green) permitting the prefrontal loop to influence the oculomotor loop. Middle, Parkinsonian on state: degraded interloop transfer through medium spiny neuron overactivity. Bottom, Parkinsonian off state: extreme abnormality of MSN activity results in complete failure of interloop information transfer, leaving the two loops isolated. DLPFC, Dorsolateral prefrontal cortex; VL, ventrolateral thalamus; FEF, frontal eye field; SEF, supplementary eye field; SNr, substantia nigra pars reticulata; Oc thal, oculomotor thalamus.