N200 (neuroscience)
Encyclopedia
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).
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
).
Following the experiment by Sutton et al. (1965), subsequent research further manipulated stimulus uncertainty in an attempt to elicit a more robust N200. The N200 has been found in a variety of different experimental conditions, and is now thought to consist of several subcomponents. The N200 in response to attended or unattended deviant auditory stimuli, similar to what was originally seen in Sutton et al. (1965), is referred to as the mismatch negativity, or Mismatch negativity
. Additionally, there is the no-go N200, which is elicited on no-go trials in go/no-go tasks . More generally, the N2 component has been described in tasks that reflect stimulus identification , attentional shifts , inhibition of motor responses, overcoming stereotypical responses or conflict monitoring , maintenance of context information , response selection timing , and detection of novelty or mismatch .
. In this task, participants are shown an array of items (usually letters), with each letter corresponding to a left or right-handed response. For example, the letter 'A' could indicate a left-handed response, and the letter 'B' a right-handed response. It is the job of the participants to respond to the central item of the array, which is flanked by the same item on compatible trials (AAAAA) or a different item on incompatible trials (BBABB). The N200 is normally seen on incompatible trials.
Another task that has been utilized to elicit a N200 is the go/no-go task . This task presents participants with two different stimuli that indicate which hand to respond with (e.g. 'A' indicates a left-handed response and 'B' a right-handed response). The stimuli also vary on another dimension that indicates whether a response is necessary (e.g. small letter requires a response, large letter means do not respond). For example, a small 'A' would indicate a left-handed go, and a large 'B' would be a right-handed no-go. The go/no-go mapping is then reversed to test for differences (e.g. letter size would indicate the hand and letter identity the go/no-go). The N200 is most often seen on no-go trials.
Since the N200 can be used to determine the order of information extraction in the go/no-go task, it is a good candidate to examine language
processing and production. Schmitt et al. (2000) utilized the no-go N200 to determine the temporal processing of semantic and phonological
information. Participants completed a go/no-go task with semantics (determining whether a picture was an animal or object) mapped to response type and phonology (whether the pictured item began with a vowel or consonant) as the go/no-go. They found that the peak latency of the N200 occurred earlier when the response was contingent on semantic information than when it depended on phonological information. Thus, the researchers were able to conclude that semantic information becomes available before phonological information in language production.
and P3b
. The N200 component responds functionally much like the P3b
component in that stimulus probability can affect the amplitude of both. This is one reason why the P3 and the N2 are often researched together, since they are both sensitive to similar manipulations and represent a connection of mental mechanisms that work together to interpret the changing environment.
In the Eriksen flanker task
and go/no-go paradigm, the peak amplitude of the N200 increases for incompatible and for no-go trials respectively .This increase in amplitude has been hypothesized as the mental need to control incorrect response preparation. Latency is correlated with response time in the flanker task . Although the N200 is primarily distributed over anterior brain regions, posterior distributions have been reported in visual attention paradigms, such as visual search .
During a stop signal task the frontocentral N2 is sensitive to time pressure, in that when individuals are asked to respond as quickly as possible the amplitude of the N2 increases. This increase in amplitude is larger within individuals who have what is considered a fast stop signal reaction time and thus who are able to inhibit a preponent response very quickly. The N2 amplitude is also reduced over right frontal electrodes sites in ADHD children . The N2 latency during the stop signal task is longer in unsuccessful than successful trials suggesting that the mental process is taking too long to evaluate the stop signal and therefore not fully processing the signal enough to inhibit a motor response .
However, the theory of the N200 as a response-inhibition mechanism has been debated by Donkers and van Boxtel (2004) . They compared ERP recordings from a go/no-go task to a go/GO task, where the GO was a more forceful response to the go task. This experimental set-up allowed them to compare the no-go task, where some responses are inhibited and compete with one another, with the GO task, where responses just compete. Evidence of a N200 was present in both the no-go and GO task, so the researchers reasoned that the N200 does not represent response-inhibition, but rather conflict monitoring. However, it is still clear that the N200 represents some cognitive control function.
Event-related potential
An event-related potential is any measured brain response that is directly the result of a thought or perception. More formally, it is any stereotyped electrophysiological response to an internal or external stimulus....
(ERP) component. An ERP can be monitored using a non-invasive electroencephalography (EEG)
Electroencephalography
Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...
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).
History
The N2 component starts with the discovery of EEGEEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
which dates back as early as 1929 with Hans Berger
Hans Berger
Hans Berger was born in Neuses near Coburg, Bavaria, Germany. He is best known as the first to record human electroencephalograms in 1924, for which he invented the electroencephalogram , and the discoverer of the alpha wave rhythm known as "Berger's wave".- Biography :After attending...
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
Event-related potential
An event-related potential is any measured brain response that is directly the result of a thought or perception. More formally, it is any stereotyped electrophysiological response to an internal or external stimulus....
. 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
P300
The P300 wave is an event related potential elicited by infrequent, task-relevant stimuli. 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 the stimulus. More specifically, the P300 is thought to...
).
Following the experiment by Sutton et al. (1965), subsequent research further manipulated stimulus uncertainty in an attempt to elicit a more robust N200. The N200 has been found in a variety of different experimental conditions, and is now thought to consist of several subcomponents. The N200 in response to attended or unattended deviant auditory stimuli, similar to what was originally seen in Sutton et al. (1965), is referred to as the mismatch negativity, or Mismatch negativity
Mismatch negativity
The mismatch negativity or mismatch field is a component of the event-related potential to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but...
. Additionally, there is the no-go N200, which is elicited on no-go trials in go/no-go tasks . More generally, the N2 component has been described in tasks that reflect stimulus identification , attentional shifts , inhibition of motor responses, overcoming stereotypical responses or conflict monitoring , maintenance of context information , response selection timing , and detection of novelty or mismatch .
Main Paradigms
The N200 is seen in a variety of experimental paradigms. A commonly used experimental design is the Eriksen flanker taskEriksen flanker task
This term refers to a group of response inhibition tests used in cognitive psychology to assess the ability to supress responses that are inappropriate in a particular context. In the flanker paradigm, a directional response is made to a central target stimulus...
. In this task, participants are shown an array of items (usually letters), with each letter corresponding to a left or right-handed response. For example, the letter 'A' could indicate a left-handed response, and the letter 'B' a right-handed response. It is the job of the participants to respond to the central item of the array, which is flanked by the same item on compatible trials (AAAAA) or a different item on incompatible trials (BBABB). The N200 is normally seen on incompatible trials.
Another task that has been utilized to elicit a N200 is the go/no-go task . This task presents participants with two different stimuli that indicate which hand to respond with (e.g. 'A' indicates a left-handed response and 'B' a right-handed response). The stimuli also vary on another dimension that indicates whether a response is necessary (e.g. small letter requires a response, large letter means do not respond). For example, a small 'A' would indicate a left-handed go, and a large 'B' would be a right-handed no-go. The go/no-go mapping is then reversed to test for differences (e.g. letter size would indicate the hand and letter identity the go/no-go). The N200 is most often seen on no-go trials.
N200 in the Study of Language
Since the N200 can be used to determine the order of information extraction in the go/no-go task, it is a good candidate to examine language
Language
Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...
processing and production. Schmitt et al. (2000) utilized the no-go N200 to determine the temporal processing of semantic and phonological
Phonology
Phonology is, broadly speaking, the subdiscipline of linguistics concerned with the sounds of language. That is, it is the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use...
information. Participants completed a go/no-go task with semantics (determining whether a picture was an animal or object) mapped to response type and phonology (whether the pictured item began with a vowel or consonant) as the go/no-go. They found that the peak latency of the N200 occurred earlier when the response was contingent on semantic information than when it depended on phonological information. Thus, the researchers were able to conclude that semantic information becomes available before phonological information in language production.
Functional Sensitivity
The latency, amplitude, and distribution of the N200 are sensitive to several factors depending on the type of experiment. The N200 is often seen as part of a complex of components including the P3aP3a
The P3a, or novelty P3, is a component of time-locked signals known as event-related potentials . The P3a is a positive-going scalp-recorded brain potential that has a maximum amplitude over frontal/central electrode sites with a peak latency falling in the range of 250-280 ms...
and P3b
P3b
The P3b is a subcomponent of the P300, an event-related potential component that can be observed in human scalp recordings of brain electrical activity...
. The N200 component responds functionally much like the P3b
P3b
The P3b is a subcomponent of the P300, an event-related potential component that can be observed in human scalp recordings of brain electrical activity...
component in that stimulus probability can affect the amplitude of both. This is one reason why the P3 and the N2 are often researched together, since they are both sensitive to similar manipulations and represent a connection of mental mechanisms that work together to interpret the changing environment.
In the Eriksen flanker task
Eriksen flanker task
This term refers to a group of response inhibition tests used in cognitive psychology to assess the ability to supress responses that are inappropriate in a particular context. In the flanker paradigm, a directional response is made to a central target stimulus...
and go/no-go paradigm, the peak amplitude of the N200 increases for incompatible and for no-go trials respectively .This increase in amplitude has been hypothesized as the mental need to control incorrect response preparation. Latency is correlated with response time in the flanker task . Although the N200 is primarily distributed over anterior brain regions, posterior distributions have been reported in visual attention paradigms, such as visual search .
During a stop signal task the frontocentral N2 is sensitive to time pressure, in that when individuals are asked to respond as quickly as possible the amplitude of the N2 increases. This increase in amplitude is larger within individuals who have what is considered a fast stop signal reaction time and thus who are able to inhibit a preponent response very quickly. The N2 amplitude is also reduced over right frontal electrodes sites in ADHD children . The N2 latency during the stop signal task is longer in unsuccessful than successful trials suggesting that the mental process is taking too long to evaluate the stop signal and therefore not fully processing the signal enough to inhibit a motor response .
Component Characteristics
The N2 ERP component can be further divided into three different sub-components: N2a or auditory MMN, N2b, and N2c. Please refer to the outline table below for each sub-component and the outlined differences and similarities.| Component | N2a or Auditory MMN | N2b | N2c |
|---|---|---|---|
| General Location: | Frontocentral/Anterior | Frontocentral/Anterior | Posterior |
| Co-component: | ---- | Observed along with frontal P3a component | Observed along with P3b component |
| Attention: | Attention not required in repetitive stimulus presentation | Requires conscious stimulus attention | Requires conscious stimulus attention |
| Scalp Distribution: | Anterior scalp distribution for auditory stimuli. | Central scalp distribution for auditory and visual stimuli. | Posterior scalp distribution for visual stimuli. Frontal-central distribution for auditory stimuli |
| Neural Generator: | Auditory cortical region, frontal lobe, and possibly hippocampus. | Anterior cingulated cortex , frontal and superior temporal cortex . | ---- |
| Paradigms: | Auditory Oddball and Go-Nogo with no behavior response. | Oddball, Flanker, Go-Nogo, Stop Signal. | Oddball, Flanker, Go-Nogo, Stop Signal. |
| Latency: | Increase latency with increase in non-targets. Related to auditory processing duration . | Latency related to timing of mental access to properties of a stimulus. | Latency related to reaction time. |
| Amplitude: | Related to sensory auditory memory traces. | Larger for non-targets with no behavioral response. Sometimes called the 'no-go N2'. | Larger for targets. Much more prominent than N2b. |
| Probability: | ---- | Increase in amplitude when no-go trials with the non-targets are less probable or equal with largest effect at Fz. | Decreased in amplitude in trials with the high probable targets with largest effect at sites Fz and Cz. |
| Cognitive Representation: | Responsible for detection of novelty or mismatch to the attended stimuli. Believed to reflect disparity between the deviating stimulus and a sensory-memory representation of the standard stimulus. Analyze the characterization of auditory stimulus features in sensory memory . Automatic novelty sensing process . | Related to response inhibition, response conflict, and error monitoring. Sensitive to detection of perceptual novelty or attentional deviation. Overriding a preponent response system. Deviation from a mentally-stored expectation of the standard stimulus . | Represents visual attention or degree of attention that is needed for processing of stimuli context and features within the visual cortex of the brain . |
Theory/Sources
In go/no-go tasks, no-go trials require inhibition of a response when information indicating response hand is processed before the go/no-go information. Presence of an N200 on no-go trials suggests that the N200 reflects a cognitive control function, specifically an inhibitory response control mechanism .However, the theory of the N200 as a response-inhibition mechanism has been debated by Donkers and van Boxtel (2004) . They compared ERP recordings from a go/no-go task to a go/GO task, where the GO was a more forceful response to the go task. This experimental set-up allowed them to compare the no-go task, where some responses are inhibited and compete with one another, with the GO task, where responses just compete. Evidence of a N200 was present in both the no-go and GO task, so the researchers reasoned that the N200 does not represent response-inhibition, but rather conflict monitoring. However, it is still clear that the N200 represents some cognitive control function.
See also
- Somatosensory evoked potentialSomatosensory Evoked PotentialSomatosensory Evoked Potentials are a useful, noninvasive means of assessing somatosensory system functioning. By combining SEP recordings at different levels of the somatosensory pathways, it is possible to assess the transmission of the afferent volley from the periphery up to the cortex...
- C1 and P1C1 & P1 (Neuroscience)The C1 and P1 are two human scalp-recorded event-related brain potential components, collected by means of a technique called electroencephalography . The C1 is named so because it was the first component in a series of components found to respond to visual stimuli when it was first discovered...
- Visual N1Visual N1The Visual N1 is a visual evoked potential, a type of event-related electrical potential , that is produced in the brain and recorded on the scalp. The N1 is so named to reflect the polarity and typical timing of the component. The "N" indicates that the polarity of the component is negative with...
- Mismatch negativityMismatch negativityThe mismatch negativity or mismatch field is a component of the event-related potential to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but...
- N100
- N2pcN2pcN2pc refers to an ERP component linked to selective attention. The N2pc appears over visual cortex contralateral to the location in space to which subjects are attending; if subjects pay attention to the left side of the visual field, the N2pc appears in the right hemisphere of the brain, and...
- N170N170The N170 is a component of the event-related potential that reflects the neural processing of faces.When potentials evoked by images of faces are compared to those elicited by other visual stimuli, the former show increased negativity 130-200 ms after stimulus presentation...
- P200P200In neuroscience, the visual P200 or P2 is a waveform component or feature of the event-related potential measured at the human scalp. Like other potential changes measurable from the scalp, this effect is believed to reflect the post-synaptic activity of a specific neural process...
- N400
- P300 (neuroscience)P300 (neuroscience)The P300 wave is an event related potential elicited by infrequent, task-relevant stimuli. 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 the stimulus. More specifically, the P300 is thought to...
- P3aP3aThe P3a, or novelty P3, is a component of time-locked signals known as event-related potentials . The P3a is a positive-going scalp-recorded brain potential that has a maximum amplitude over frontal/central electrode sites with a peak latency falling in the range of 250-280 ms...
- P3bP3bThe P3b is a subcomponent of the P300, an event-related potential component that can be observed in human scalp recordings of brain electrical activity...
- Late Positive ComponentLate Positive ComponentThe LPC is a positive-going event-related brain potential component that has been important in studies of explicit recognition memory...
- Difference due to MemoryDifference due to MemoryDifference due to Memory indexes differences in neural activity during the study phase of an experiment for items that subsequently are remembered compared to items that are later forgotten...
- Contingent negative variationContingent negative variationThe contingent negative variation was one of the first event-related potential components to be described. The CNV component was first described by Dr. W. Grey Walter and colleagues in an article published in Nature in 1964...
- Error-related negativityError-related negativityError-related negativity , , is a component of an event-related potential . ERPs are electrical activity in the brain as measured through electroencephalography and time-locked to an external event...
- BereitschaftspotentialBereitschaftspotentialIn neurology, the Bereitschaftspotential or BP , also called the pre-motor potential or readiness potential , is a measure of activity in the motor cortex of the brain leading up to voluntary muscle movement. The BP is a manifestation of cortical contribution to the pre-motor planning of volitional...
- Lateralized readiness potentialLateralized readiness potentialIn neuroscience, the lateralized readiness potential is an event-related brain potential, or increase in electrical activity at the surface of the brain, that is thought to reflect the preparation of motor activity on a certain side of the body; in other words, it is a spike in the electrical...
- Early left anterior negativityEarly left anterior negativityThe early left anterior negativity is an event-related potential in electroencephalography , or component of brain activity that occurs in response to a certain kind of stimulus...
- P600P600The P600 is an event-related potential , or peak in electrical brain activity measured by electroencephalography . It is a language-relevant ERP and is thought to be elicited by hearing or reading grammatical errors and other syntactic anomalies...