Progression of P300 in a patient with bilateral hippocampal lesions

Objective To evaluate the effects of hippocampal damages on P300 of event-related potentials (ERPs). Methods ERPs were recorded over about 8 months using the auditory oddball paradigm in a patient with bilateral hippocampal lesions confirmed on brain magnetic resonance imaging. Findings were compared with those from clinical electroencephalography (periodic lateralized epileptiform discharges (PLEDs) or bilateral independent PLEDs (BIPLEDs)). The patient displayed no marked clinical symptoms aside from mild memory impairment during this time, and was able to fully perform the oddball task. Results Clearly identifiable P300 were present in all recordings. Furthermore, increases in the number of right PLEDs were significantly correlated with increases in P300 latency. Conclusions Two key results were apparent. First, the appearance of P300 in all ERP recordings supports the suggestion that the hippocampus is not indispensable for P300 generation. Second, the correlation between the number of PLEDs and P300 latency supports the suggestion that the hippocampus affect the components of P300 latency. Significance This case thus offers very suggestive evidence regarding the generation of P300.