The P200 ERP Response in Mild Cognitive Impairment and the Aging Population

Evoked potential metrics extracted from an EEG exam can provide novel sources of information regarding brain function. While the P300 occurring around 300 ms post-stimulus has been extensively investigated in relation to mild cognitive impairment (MCI), with decreased amplitude and increased latency, the P200 response has not, particularly in an oddball-stimulus paradigm. This study compares the auditory P200 amplitudes between MCI (28 patients aged 74(8)) and non-MCI, (35 aged 72(4)). Data were collected in routine clinical evaluations where EEG with audio oddball ERPs were measured as part of a health screening exam from 2 clinics serving MCI patients and one clinic serving a non-MCI population as part of a wellness/preventative care program. We also investigated the disease course for 3 patients as case studies. The results revealed the P200 amplitudes to be significantly increased in the MCI compared to the non-MCI groups, alongside the expected reduction in P300, Trail Making, and reaction time. Moreover, the ratio of P200-to-P300 was also increased in the MCI groups even in cases where the P300 was strong. This trend continued for patients who were tracked from early-to-later stages in the case studies. While the pathophysiology of the P200 response in a 2-tone auditory oddball protocol is not well understood, this measure may help indicate signs of early MCI, particularly in cases where the P300 is still strong.