SHORT COMMUNICATION Preliminary evidence for correlation between PASAT performance and P3a and P3b amplitudes in progressive multiple sclerosis H. Kiiski a , R. Whelan a , R. Lonergan b , H. Nolan a , K. Kinsella b , M. Hutchinson b , N. Tubridy b and R. B. Reilly a a Trinity Centre for Bioengineering, Trinity College Dublin, College Green, Dublin, Ireland; and b Department of Neurology, St. VincentÕs University Hospital, Elm Park, Dublin, Ireland Keywords: attention, auditory event- related potentials, cogni- tion, multiple sclerosis, neuropsychology, visual event-related potentials Received 30 March 2010 Accepted 21 June 2010 Background: 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. Methods: Thirty subjects (10 PPMS, 10 SPMS and 10 age-matched controls) com- pleted 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. Results: For the patients with multiple sclerosis (MS), PASAT score correlated sig- nificantly 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 con- dition 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. Conclusions: 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. Introduction Cognitive impairment (CI) is common in multiple sclerosis (MS). CI in MS is often measured with the Paced Auditory Serial Attention Test (PASAT), a test of attention and working memory [1]. Patients with primary progressive MS (PPMS) experience disease progression from onset without major relapses or remission. Patients with secondary-progressive MS (SPMS) have initially relapsing–remitting disease course followed by disease progression. Some studies have found significant neuropsychological differences between the PPMS and SPMS (e.g. [2]) but some have found none (e.g., [3]). Both subtypes perform worse on the PASAT in comparison with controls [2]. In a two-stimulus oddball task, occasional target stimuli have to be detected in a train of frequent irrel- evant standard stimuli: a P3b event-related potential (ERP) component is typically observed, reflecting con- text updating. A no-go P3a can be elicited when third – non-novel repeated – stimulus is presented, signalling the engagement of attention [4]. In a previous study, there was no difference in visual P3b amplitude between patients with PPMS and SPMS. However, only one electrode was used, making topographical analyses impossible [5]. We previously employed a high-density EEG array [6,7] and reported significant differences between patients with relapsing–remitting MS (RRMS) and SPMS versus controls in both auditory and visual P3b and P3a. Patients with RRMS and SPMS differed only in visual P3a latency. The aim of this study was to investigate the topog- raphy of PASAT score and P3 amplitude correlations by employing 128 scalp electrodes. We also compared Correspondence: R. Whelan, Trinity Centre for Bioengineering, Trinity College Dublin, College Green, Dublin 2, Ireland (tel.: +353 1 8964214; fax: +353 1 679 5554; e-mail: robert. whelan@tcd.ie). 792 Ó 2010 The Author(s) European Journal of Neurology Ó 2010 EFNS European Journal of Neurology 2011, 18: 792–795 doi:10.1111/j.1468-1331.2010.03172.x