Event-related brain potential changes after Choto-san administration in stroke patients with mild cognitive impairments

Rationale. Few drugs have been reported to be effective for the treatment of vascular dementia. Choto-san is a herbal medicine expected to be effectivein this condition, but it is unclear how this drug modulates brain activities and cognitive functions. P3 event-related brain potentials (ERP) provide reliable electrophysiological indices for some aspects of cognitive functions. Objectives. We measured P3 ERP to assess the effect of Choto-san administration on stroke patients with mild cognitive impairments. Methods. Choto-san was given for 12 weeks to ten chronic stroke patients. P3 ERP were recorded before and after drug administration in a modified auditory oddball paradigm including occasional novel sounds using a high-density array EEG recording system. The reproducibility of ERP was also assessed in other ten stroke patients with a 12-week interval. Cognitive functions were assessed with the Mini Mental State Examination (MMSE) and verbal fluency test. Results. Twelve-week administration of Choto-san significantly improved MMSE and verbal fluency test scores. The reproducibility of P3 latency and amplitude to target and novel sounds was excellent. P3 latency to target sounds was shortened in association with reduced reaction time to the sounds after drug administration. Furthermore, P3 amplitude to novel sounds was enlarged and its topography shifted from central to frontal sites. Conclusions. These results indicate that Choto-san improves electrophysiological indices related to attention and decision making, in addition to neuropsychological test scores in stroke patients with mild cognitive impairments.