Fast stimulus sequences improve the efficiency of event-related potential P300 recordings

The P300 is an easily recorded component of the event-related potential (ERP). Yet, it is desirable to reduce the recording duration, for instance in patient examinations. A limiting factor is the time between stimuli that is necessary for the ERP to return to baseline. We explored whether this time could be reduced, despite an overlap of responses to successive stimuli, by presenting visual stimuli at a fast rate of 4.7 s(-1)using a standard oddball paradigm. Rare stimuli occurred at a probability of 14%. The P300 was isolated by subtracting the responses to the frequent stimuli from those to the rare stimuli, thereby eliminating the influence of response overlap. We compared the efficiency of fast stimulation to that of conventionally slow stimulation by assessing the signal-to-noise ratio of the P300 amplitude. Two presentation durations of individual stimuli, namely 53 ms and 93 ms, were tested. Not unexpectedly, P300 amplitudes were smaller for the fast sequence. However, the signal-to-noise ratio improved significantly by more than 50% due to the larger number of trials within a given time interval. When targeting a given signal-to-noise ratio, fast stimulation allows for a reduction in recording time of around 35%. Median peak times were 16-56 ms shorter for the fast stimulus sequence. Topography was comparable for fast and slow stimulation, suggesting a similar functional composition of the respective responses. Fast stimulation may thus be used to replace less efficient slow stimulation schemes in clinical diagnosis and for certain experimental questions.