Associations between a cerebellar motor dysfunction scale and movement initiation and completion in olivopontocerebellar atrophy.

Correlations were drawn between subscores of a cerebellar motor dysfunction (CMD) scale and simple reaction time (RT) and movement time (MT) in patients diagnosed with olivopontocerebellar atrophy (OPCA). Poor performance on CMD subscores was correlated with long disease duration and lengthening of visual and auditory RT and MT, with the motor speed subscore showing the highest correlations. OPCA patients with severe cerebellar HMPAO uptake deficiency on single photon emission computed tomography scans had poorer performances on three of the four subscores (static equilibrium, dynamic equilibrium and nystagmus, and motor speed) than patients with mild deficiency. These results are discussed in terms of the role of cerebellar afferent/efferent pathways on different types of motor dysfunction in patients with cerebellar atrophy.

Exploratory drive, frontal lobe function and adipsia in aging.

Aging in animals in accompanied by a decrease in exploratory drive, as assessed by hole poking and spontaneous alternation tests. This decrease is caused either by increased fear of the novel testing environment (neophobia) or by apathy. Either cause may be related to dysfunction of prefrontal cortex-related pathways. The myelination of the prefrontal cortex appears late in ontogeny. In accordance to the last-in first-out principle, this brain region seems to be affected early during aging. It remains to be determined whether this decrease of exploratory behavior is reversible by behavioral intervention, by dietary changes or by the administration of psychotropic drugs. One hypothesis worth testing is whether the decrease in exploration is associated to the well-described adipsia in human aging, whose neurobiological basis has not yet been determined. It is possible to consider that the maladaptive response to thirst is responsible for some senescent changes in the brain and that reversal of adipsia by behavioral, dietary or pharmacological means improves the quality of life in the elderly.