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.