P300 (neuroscience)

It is considered to be an endogenous potential, as its occurrence links not to the physical attributes of a stimulus, but to a person's reaction to it.

The presence, magnitude, topography and timing of this signal are often used as metrics of cognitive function in decision-making processes.

While the neural substrates of this ERP component still remain hazy, the reproducibility and ubiquity of this signal makes it a common choice for psychological tests in both the clinic and laboratory.

They also found that the ERP responses to the numbers, but not to the light flashes, contained a large positivity that peaked around 300 ms after the stimulus appeared.

Another important finding from these studies is that this late positive complex was observed for both the clicks and flashes, indicating that the physical type of the stimulus (auditory or visual) did not matter.

The P3a has been associated with brain activity related to the engagement of attention (especially the orienting, involuntary shifts to changes in the environment), and the processing of novelty.

In a proposed "guilty knowledge test"[12] a subject is interrogated via the oddball paradigm much as they would be in a typical lie-detector situation.

This practice has recently enjoyed increased legal permissibility while conventional polygraphy has seen its use diminish, in part owing to the unconscious and uncontrollable aspects of the P300.

The technique relies on reproducible elicitation of the P300 wave, central to the idea of a Memory and Encoding Related Multifaceted Electroencephalographic Response (MERMER) developed by Dr. Lawrence Farwell.

The P300 waveform can also be evoked in nearly all subjects with little variation in measurement techniques, which may help simplify interface designs and permit greater usability.

One negative characteristic of the P300 is that the amplitude of the waveform requires averaging of multiple recordings to isolate the signal.

[14] The algorithm proposed by Farwell and Donchin[16] provides an example of a simple BCI that relies on the unconscious decision making processes of the P300 to drive a computer.

[14] Scientific research often relies on measurement of the P300 to examine event related potentials, especially with regard to decision making.

P300 latency and amplitude trajectories across the lifespan as obtained from the cross-sectional dataset . Dots represent scores from individual participants. From From P300 Development across the Lifespan: A Systematic Review and Meta-Analysis . [ 1 ] The latency and amplitude of the P300 response may vary as a function of age.
The P300 response of different healthy subjects in a two-tone auditory oddball paradigm. The plots show the average response to oddball (red) and standard (blue) trials and their difference (black). From Surprise response as a probe for compressed memory states . [ 2 ] These examples show the significant individual variability in amplitude, latency and waveform shape across different subjects.
The P300 response as a function of the oddball probability. From Surprise response as a probe for compressed memory states . [ 2 ] The ERP shows a larger P300 response magnitude to oddball stimuli and a lower P300 response to standard stimuli as the oddball probability decreases.