N200 (neuroscience)

The N200, or N2, is an event-related potential (ERP) component. An ERP can be monitored using a non-invasive electroencephalography (EEG) cap that is fitted over the scalp on human subjects. An EEG cap allows researchers and clinicians to monitor the minute electrical activity that reaches the surface of the scalp from post-synaptic potentials in neurons, which fluctuate in relation to cognitive processing. EEG provides millisecond-level temporal resolution and is therefore known as one of the most direct measures of covert mental operations in the brain. The N200 in particular is a negative-going wave that peaks 200-350ms post-stimulus and is found primarily over anterior scalp sites. Past research focused on the N200 as a mismatch detector, but it has also been found to reflect executive cognitive control functions, and has recently been used in the study of language (Folstein & Van Petten, 2008; Schmitt, Münte, & Kutas, 2000). The N2 component starts with the discovery of EEG which dates back as early as 1929 with Hans Berger demonstrating the ability to record electrical activity of the brain by simply placing electrodes over the scalp and then amplifying the signal. Later, in 1936, researcher Pauline and Hallowell Davis manipulated events in the environment and recorded the first known ERP's. One of the first experiments to find evidence of an N200 was by Sutton, Braren, and Zubin (1965) when examining the effects of stimulus uncertainty on sensory potentials. In their study, participants were presented with two types of paired stimuli. In the certain condition, a cue stimulus was presented that was predictive of the modality of the target stimulus, which was either clicks or light flashes. In the uncertain condition, the cue stimulus was not predictive and could be followed by either a click or a light flash. The researchers occasionally found a negativity that peaked on average 190ms post-stimulus in the uncertain condition (N200), in addition to a positivity 300ms post-stimulus (P300).