P300 (neuroscience)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/11/P300_latency_and_amplitude_trajectories_across_the_lifespan_as_obtained_from_the_cross-sectional_dataset.png/220px-P300_latency_and_amplitude_trajectories_across_the_lifespan_as_obtained_from_the_cross-sectional_dataset.png)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/cc/P300_response_of_different_subjects.png/220px-P300_response_of_different_subjects.png)
The P300 (P3) wave is an event-related potential (ERP) component elicited in the process of decision making. 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. More specifically, the P300 is thought to reflect processes involved in stimulus evaluation or categorization.
It is usually elicited using the oddball paradigm, in which low-probability target items are mixed with high-probability non-target (or "standard") items. When recorded by electroencephalography (EEG), it surfaces as a positive deflection in voltage with a latency (delay between stimulus and response) of roughly 250 to 500 ms.[3] In the scientific literature a differentiation is often made in the P3, which is divided according to time: Early P3 window (300-400 ms) and Late P3 window (380-440 ms).[4]
The signal is typically measured most strongly by the electrodes covering the
History
Early observations of the P300 (more specifically, the component that would later be named the P3b) were reported in the mid-1960s. In 1964, researchers Chapman and Bragdon
In 1965, Sutton and colleagues published results from two experiments that further explored this late positivity. They presented subjects with either a cue that indicated whether the following stimulus would be a click or a flash, or a cue which required subjects to guess whether the following stimulus would be a click or a flash. They found that when subjects were required to guess what the following stimulus would be, the amplitude of the "late positive complex"[6] was larger than when they knew what the stimulus would be. In a second experiment, they presented two cue types. For one cue there was a 2 in 3 chance that the following stimulus would be a click and a 1 in 3 chance that the following stimulus would be a flash. The second cue type had probabilities that were the reverse of the first. They found that the amplitude of the positive complex was larger in response to the less probable stimuli, or the one that only had a 1 in 3 chance of appearing. 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.
In later studies published in 1967, Sutton and colleagues had subjects guess whether they would hear one click or two clicks.[7] They again observed a positivity around 300 ms after the second click occurred – or would have occurred, in the case of the single click. They also had subjects guess how long the interval between clicks might be, and in this case, the late positivity occurred 300 ms after the second click. This shows two important findings: first, that this late positivity occurred when uncertainty about the type of click was resolved, and second, that even an absence of a stimulus would elicit the late positive complex, if said stimulus was relevant to the task. These early studies encouraged the use of ERP methods to study cognition and provided a foundation for the extensive work on the P300 in the decades that followed.
P3a and P3b
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/21/P300_vs_oddballProbability.svg/220px-P300_vs_oddballProbability.svg.png)
The P3a, or novelty P3,[8] has a positive-going amplitude that displays maximum amplitude over frontal/central electrode sites and has a peak latency in the range of 250–280 ms. 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.[9]
The P3b has a positive-going amplitude (usually relative to a reference behind the ear or the average of two such references) that peaks at around 300 ms, and the peak will vary in latency from 250 to 500 ms or more, depending upon the task and the individual subject response.[3] Amplitudes are typically highest on the scalp over parietal brain areas.[3] The P3b has been a prominent tool used to study cognitive processes, especially psychology research on information processing. Generally speaking, improbable events will elicit a P3b, and the less probable the event, the larger the P3b amplitude.[10] This was shown to be true both for the overall probability and for the local probability.[2] However, in order to elicit a P3b, the improbable event must be related to the task at hand in some way (for example, the improbable event could be an infrequent target letter in a stream of letters, to which a subject might respond with a button press). The P3b can also be used to measure how demanding a task is on cognitive workload.[10]
Since the initial discovery of the P300, research has shown that the P300 has two subcomponents. The subcomponents are the novelty P3, or P3a, and the classic P300, which has since been renamed P3b.[11]
Applications
Since the mid-1980s, one of the most discussed uses of ERPs such as the P300 is related to
Applications in
Scientific research often relies on measurement of the P300 to examine event related potentials, especially with regard to decision making. Because cognitive impairment is often correlated with modifications in the P300, the waveform can be used as a measure for the efficacy of various treatments on cognitive function. Some have suggested its use as a clinical marker for precisely these reasons. There is a broad range of uses for the P300 in clinical research.[17]
Some research groups have performed fMRI combined to EEG in order to achieve inner-speech dictation and the approach of inner-speech recognition.[18][19][20]
The P300 wave obtained by visual stimulation is used to assess cognitive processes in humans, and the value of the latency and amplitude of the P300 wave can be a measure of the severity of dementia processes.[21] The analysis of P300 wave latency seems to be particularly useful in the diagnosis of mild cognitive impairment (MCI).[22]
See also
References
- PMID 24551055.
- ^ PMID 32012146.
- ^ PMID 17573239.
- PMID 12236331.
- S2CID 4156804.
- S2CID 39822117.
- S2CID 36787865.
- S2CID 17357823.
- ^ Polich, J. (2003). "Overview of P3a and P3b". In J. Polich (ed.). Detection of Change: Event-Related Potential and fMRI Findings. Boston: Kluwer Academic Press. pp. 83–98.
- ^ PMID 7280146.
- S2CID 4614708.
- PMID 11210899. Archived from the original(PDF) on 2016-03-17. Retrieved 2016-07-22.
- S2CID 24199528.
- ^ S2CID 84043.
- PMID 18571984.
- S2CID 4547500. Archived from the original(PDF) on 2017-02-05.
- S2CID 53176706.
- PMID 15496671.
- )
- )
- .
- .
External links
- P300+Event-Related+Potentials at the U.S. National Library of Medicine Medical Subject Headings (MeSH)