Impairment of eyeblink classical conditioning in progressive supranuclear palsy

In a previous study we showed that learning in eyeblink classical conditioning (EBCC) is normal in Parkinson's disease (PD) and that the serial reaction time task (SRTT) is only marginally impaired. Since pathological lesions are more widespread in the atypical parkinsonian disorder of progressive supranuclear palsy (PSP) than in PD, we hypothesized that PSP patients may show more profound deficits in the EBCC and SRTT learning tasks. We therefore investigated EBCC with a delay and two trace paradigms, an SRTT and the California Verbal Learning Test (CVLT) in eight patients with PSP and an age-matched control group. In all EBCC paradigms, we found a significant difference between groups with no significant learning in PSP patients. In the SRTT, implicit learning may have been impaired, but verbal and manual sequence recall were only marginally impaired. Verbal memory was significantly worse in PSP patients than in the control group. Our study shows a dissociated pattern of learning abilities in PSP, where the EBCC as a measure of implicit learning is impaired, the explicit sequence detection in the SRTT is relatively preserved, and the verbal memory impaired. We hypothesize that the PSP patients' deficits in EBCC learning may be due to lesions of deep cerebellar nuclei. There may be a clinical role for EBCC in distinguishing PD and PSP patients.