On susceptibility weighted imaging sequences, this structure’s posterior portion normally resembles a swallow’s tail. On an axial view, this structure separates the red nucleus from the peduncle. This structure closely corresponds to the rodent A9 cell group. This structure both stimulates the direct pathway [emphasize] and inhibits the indirect pathway through projections that synapse onto the medium spiny neurons of the dorsal (*) striatum. MPTP destroys the cells in this structure’s pars compacta responsible for producing a molecule whose deficiency can cause cogwheel rigidity and a shuffling gait. The characteristic appearance of this portion of the basal ganglia results from high levels of neuromelanin. For 10 points, the depletion of what structure’s dopaminergic neurons characterizes Parkinson’s disease, and causes it to lose its “black” appearance? ■END■
ANSWER: substantia nigra [accept substantia nigra pars compacta or substantia nigra pars reticulata; prompt on basal ganglia until read]
<Itamar Naveh-Benjamin, Biology>
= Average correct buzz position