The no-go P3a event-related potential (ERP) is a measure of attentional engagement and the P3b is a measure of context updating. The aim of this study was to compare ERP topographies: (i) to Paced Auditory Serial Addition Test (PASAT) results, (ii) of visual and auditory P3a and P3b of patients with primary progressive multiple sclerosis (PPMS) versus patients with secondary-progressive multiple sclerosis (SPMS) and (iii) of both progressive subtypes to healthy controls.
Thirty subjects (10 PPMS, 10 SPMS and 10 age-matched controls) completed visual and auditory no-go P3a and P3b tasks whilst data were recorded from a 128-scalp channel electroencephalography (EEG) array. Data from scalp channels were converted into continuous interpolated images (incorporating the entire scalp and time). Topographical differences and correlations were then tested using statistical parametric mapping.
For the patients with multiple sclerosis (MS), PASAT score correlated significantly with parietal regions in the auditory P3b, auditory P3a and visual P3b conditions, and with central regions in the visual P3a condition. Patients with PPMS had significantly lower amplitude than patients with SPMS in the auditory P3b condition over the parietal area. The control group had greater amplitude than the patients with MS in all the P3 tasks, with the exception of the auditory P3b.
These data suggest that PASAT performance and P3 ERPs correlate for MS progressive subtypes and that PPMS and SPMS differ in electrophysiological responses during auditory P3b tasks.