[Symptomatology of fronto-temporal dementia]

Behavioral changes in patients with FTD can be interpreted by considering damage to the frontal lobes themselves and considering the interaction between the frontal lobes and other neural systems such as the posterior association cortices, the limbic system, and basal ganglia. Loss of insight and apathy primarily result from frontal lobes involvement. The latter is probably correlated with the severity of medial frontal-anterior cingulate involvement. Stimulus-bound behavior such as imitation behavior, utilization behavior and environmental dependency syndrome is caused by an imbalance between the activities of the frontal and parietal lobes. Frontal lobe damage, particularly damage to the medial frontal area, result in liberation of the parietal lobe activity, leaving the patient subject to any stimuli from the external environment. Disinhibition such as antisocial behavior is produced by an imbalance between the activities of the frontal and limbic lobes. Namely, loss of control of the frontal lobe, especially the orbitofrontal area, over the limbic system results in acts led by instinctive desires and uncontrolled by reason. Stereotypic behavior is due to an imbalance between the activities of the frontal cortex and basal ganglia. These behaviors range from simple stereotypies to complex repeated actions such as roaming, clock-watching or adherence to a strict daily timetable.