In neuroscience, the N100 or N1 is a large, negative-going evoked potential measured by electroencephalography (its equivalent in magnetoencephalography is the M100); it peaks in adults between 80 and 120 milliseconds after the onset of a stimulus, and is distributed mostly over the fronto-central region of the scalp.
Specifically, it has been found to be sensitive to things such as the predictability of an auditory stimulus, and special features of speech sounds such as voice onset time.
The N100 plays a role in recognizing the difference and categorizing these sounds: speech stimuli with a short 0 to +30 ms voice onset time evoke a single N100 response but those with a longer (+30 ms and longer) evoked two N100 peaks and these are linked to the consonant release and vocal cord vibration onset.
[29] Another top-down influence upon N100 has been suggested to be efference copies from a person's intended movements so that the stimulation that results from them are not processed.
[33] The N100 may be used to test for abnormalities in the auditory system where verbal or behavioral responses cannot be used,[36] such with individuals in coma; in such cases, it can help predict the probability of recovery.
[39] High density mapping of the location of the generators of M100 is being researched as a means of presurgical neuromapping needed for neurosurgery.
[40] Many cognitive or other mental impairments are associated with changes in the N100 response, including the following: The N100 is 10 to 20% larger than normal when the auditory stimulus is synchronized with the diastolic phase of the cardiac blood pressure pulse.
[45] The Mismatch negativity (MMN) is an evoked potential that occurs at roughly the same time as N100 in response to rare auditory events.
It differs from the N100 in that: Though this suggests that they are separate processes, arguments have been made that this is not necessarily so and that they are created by the "relative activation of multiple cortical areas contributing to both of these 'components'".
[54] New techniques, such as event-related beam-forming with magnetoencephalography, allow sufficiently accurate location of M100 sources to be clinically useful for preparing surgery upon the brain.