Progressive supranuclear palsy: Altered sensory processing leads to degraded cognition

We studied the latencies, amplitudes, and scalp distributions of the early and late components of the event- related brain potential (ERP) in patients with progressive supranuclear palsy (PSP) and matched normal controls. In separate choice reaction time (RT) tasks, the subjects pressed buttons to visual stimuli presented randomly at probabilities of either 20/80 or 50/50. Compared with normal controls, PSP patients had significantly reduced amplitudes and increased latencies for both the visual P2 and P300 components at all levels of probability. RTs and percent errors were significantly greater in the patients compared with controls. Neither the amplitude nor latency of the visual N1 component was significantly altered in these patients. There were no significant group differences in the distribution of electrical activity over the scalp for any of these ERP components, a finding which suggests that the neural structures responsible for generating these potentials were intact in these patients. The decreased ERP component amplitudes and increased ERP component latencies, combined with intact scalp distributions and increased RTs and error rates, present a pattern of results suggesting that the stimulus identification or categorization processes in these patients are significantly degraded.