Impaired temporal discrimination in Parkinson's disease: temporal processing of brief durations as an indicator of degeneration of dopaminergic neurons in the basal ganglia.

Recent findings suggest that temporal processing of brief durations is a function of dopaminergic neurotransmission in the basal ganglia. Furthermore, there is preliminary evidence of abnormal timing functions in patients suffering from idiopathic Parkinson's disease (PD). In the present study, temporal discrimination of intervals in the range of milliseconds was investigated in 20 PD patients and 20 healthy controls matched for sex and age. Temporal discrimination was significantly impaired in PD patients as compared to healthy controls. For PD patients, additional correlational analyses did not yield any significant relationship between performance on temporal processing and degree of motor impairment or illness duration. However, impairment in temporal processing was associated with dosage of L-dopa substitution and self-rated feelings of depression. The overall pattern of results suggests that deficits in temporal information processing observed in PD patients may represent a trait marker of vulnerability to decreasing levels of dopaminergic activity in the basal ganglia rather than a state-dependent indicator of the acute clinical symptomatology.