Basal Nuclei Circuit

CLOSE

Figure 18—45. Diagram of basal nuclei circuits for selecting/executing movements (green = excitatory; red = inhibitory; dotted outline = spontaneously active). Basal nuclei shown above facilitate desired movements and dampen unwanted movements. Voluntary movements initiated by the cerebral cortex involve thalamocortical circuits propelled by excitation from cerebellar nuclei. Particular regions of cerebral cortex project to three basal nuclei (accumbens, caudate & putamen) that collectively constitute the striatum. Via two pathways, the striatum controls spontaneously active neurons within basal nuclei that tonically inhibit thalamocortical movement circuits (also midbrain generated movements). A direct pathway facilitates desired movements, via inhibition of the endopeduncular nucleus (and substantia nigra reticulata). An indirect pathway suppresses unwanted movement (by inhibiting the globus pallidus which tonically inhibits endopeduncular and subthalamic nuclei). The cerebral cortex is able to suppress movements directly via input to the subthalamic nucleus, which enhances endopeduncular inhibition. The substantia nigra reticulata tonically inhibits the midbrain tectum, the red nucleus and reticular formation nuclei. Via dopamine release that targets excitatory/inhibitory dopamine receptors on striatal neurons, the substantia nigra compacta modulates the two striatal pathways, favoring movement.

Go Top