One of the reports Albert sent me ( “Choreic Syndrome after Cardiac Surgery – 1988” ) mentions that all 5 children suffered complete supranuclear ophthalmoplegia. Here is an extract of the wikipedia on the role of Basal ganglia and eye movement. In Clarisse’s case, she is not yet suffering from ophthalmoplegia.
One of the most intensively studied functions of the BG is their role in controlling eye movements. Eye movement is influenced by an extensive network of brain regions that converge on a midbrain area called the superior colliculus (SC). The SC is a layered structure whose layers form two-dimensional retinotopic maps of visual space. A “bump” of neural activity in the deep layers of the SC drives an eye movement directed toward the corresponding point in space.
The SC receives a strong inhibitory projection from the BG, originating in the substantia nigra pars reticulata (SNr). Neurons in the SNr usually fire continuously at high rates, but at the onset of an eye movement they “pause”, thereby releasing the SC from inhibition. Eye movements of all types are associated with “pausing” in the SNr; however, individual SNr neurons may be more strongly associated with some types of movements than others. Neurons in some parts of the caudate nucleus also show activity related to eye movements. Since the great majority of caudate cells fire at very low rates, this activity almost always shows up as an increase in firing rate. Thus, eye movements begin with activation in the caudate nucleus, which inhibits the SNr via the direct GABAergic projections, which in turn disinhibits the SC.