N200 (neuroscience)

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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. [1] 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).

Contents

History

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) [2] 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. Additionally, there is the no-go N200, which is elicited on no-go trials in go/no-go tasks. [3] More generally, the N2 component has been described in tasks that reflect stimulus identification, [4] attentional shifts, [4] inhibition of motor responses, overcoming stereotypical responses or conflict monitoring, [5] maintenance of context information, [5] response selection timing, [6] and detection of novelty or mismatch. [1]

Main paradigms

The N200 is seen in a variety of experimental paradigms. A commonly used experimental design is the Eriksen flanker task. 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. [7] 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.

In the study of language

Since the go/no-go paradigm with N200 can be used to indicate the timing of information noting, it is a good candidate to examine the order of language processing and production. Schmitt et al. (2000) [8] utilized the occurrence of N200 in the go/no-go paradigm to determine the timing of semantic and phonological information processing. Participants were presented with a series of pictures. In one trial instance, the participant was asked to respond (by pressing a button) or not to make a respond based on the semantic feature of the picture - whether the picture depicted an animal or a non-animal object; in the paralleled instance, the participant made a response or no response based upon whether the name of the pictured item began with a vowel or consonant (phonology-dependent). EEG of the participants were analyzed, and the researchers found that the peak latency of the N200 occurred earlier when the response was contingent on semantic information than on phonological information. Thus, they were able to conclude that semantic information becomes available earlier than phonological information in language processing. Researchers have also been able to show that some forms of knowledge are available from written words as quickly as 160 ms by capitalizing on the go/nogo paradigm associated with N200 to . [9] [10]

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 P3a 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. [7] [11] 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. [1] Although the N200 is primarily distributed over anterior brain regions, posterior distributions have been reported in visual attention paradigms, such as visual search. [1]

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 prepotent response very quickly. The N2 amplitude is also reduced over right frontal electrodes sites in ADHD children. [5] 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. [5]

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.

ComponentN2a or Auditory MMNN2bN2c
General Location:Frontocentral/AnteriorFrontocentral/AnteriorPosterior
Co-component:----Observed along with frontal P3a componentObserved along with P3b component
Attention:Attention not required in repetitive stimulus presentationRequires conscious stimulus attentionRequires 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, [1] frontal and superior temporal cortex. [4] ----
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. [4] 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. [4] Automatic novelty sensing process. [4] Related to response inhibition, response conflict, and error monitoring. Sensitive to detection of perceptual novelty or attentional deviation. Overriding a prepotent response system. Deviation from a mentally-stored expectation of the standard stimulus. [4] Represents visual attention or degree of attention that is needed for processing of stimuli context and features within the visual cortex of the brain. [1]

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. [1]

However, the theory of the N200 as a response-inhibition mechanism has been debated by Donkers and van Boxtel (2004). [12] 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

Related Research Articles

<span class="mw-page-title-main">Neurolinguistics</span> Neuroscience and linguistics-related studies

Neurolinguistics is the study of neural mechanisms in the human brain that control the comprehension, production, and acquisition of language. As an interdisciplinary field, neurolinguistics draws methods and theories from fields such as neuroscience, linguistics, cognitive science, communication disorders and neuropsychology. Researchers are drawn to the field from a variety of backgrounds, bringing along a variety of experimental techniques as well as widely varying theoretical perspectives. Much work in neurolinguistics is informed by models in psycholinguistics and theoretical linguistics, and is focused on investigating how the brain can implement the processes that theoretical and psycholinguistics propose are necessary in producing and comprehending language. Neurolinguists study the physiological mechanisms by which the brain processes information related to language, and evaluate linguistic and psycholinguistic theories, using aphasiology, brain imaging, electrophysiology, and computer modeling.

<span class="mw-page-title-main">Event-related potential</span> Brain response that is the direct result of a specific sensory, cognitive, or motor event

An event-related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, or motor event. More formally, it is any stereotyped electrophysiological response to a stimulus. The study of the brain in this way provides a noninvasive means of evaluating brain functioning.

The N400 is a component of time-locked EEG signals known as event-related potentials (ERP). It is a negative-going deflection that peaks around 400 milliseconds post-stimulus onset, although it can extend from 250-500 ms, and is typically maximal over centro-parietal electrode sites. The N400 is part of the normal brain response to words and other meaningful stimuli, including visual and auditory words, sign language signs, pictures, faces, environmental sounds, and smells.

<span class="mw-page-title-main">P300 (neuroscience)</span> Event-related potential

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.

The mismatch negativity (MMN) or mismatch field (MMF) is a component of the event-related potential (ERP) 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 has most frequently been studied for hearing and for vision, in which case it is abbreviated to vMMN. The (v)MMN occurs after an infrequent change in a repetitive sequence of stimuli For example, a rare deviant (d) stimulus can be interspersed among a series of frequent standard (s) stimuli. In hearing, a deviant sound can differ from the standards in one or more perceptual features such as pitch, duration, loudness, or location. The MMN can be elicited regardless of whether someone is paying attention to the sequence. During auditory sequences, a person can be reading or watching a silent subtitled movie, yet still show a clear MMN. In the case of visual stimuli, the MMN occurs after an infrequent change in a repetitive sequence of images.

<span class="mw-page-title-main">Negative priming</span> Initial stimulus inhibits response to subsequent stimulus

Negative priming is an implicit memory effect in which prior exposure to a stimulus unfavorably influences the response to the same stimulus. It falls under the category of priming, which refers to the change in the response towards a stimulus due to a subconscious memory effect. Negative priming describes the slow and error-prone reaction to a stimulus that is previously ignored. For example, a subject may be imagined trying to pick a red pen from a pen holder. The red pen becomes the target of attention, so the subject responds by moving their hand towards it. At this time, they mentally block out all other pens as distractors to aid in closing in on just the red pen. After repeatedly picking the red pen over the others, switching to the blue pen results in a momentary delay picking the pen out. The slow reaction due to the change of the distractor stimulus to target stimulus is called the negative priming effect.

The contingent negative variation (CNV) is a negative slow surface potential, as measured by electroencephalography (EEG), that occurs during the period between a warning stimulus or signal and an imperative ("go") stimulus. The CNV was one of the first event-related potential (ERP) components to be described. The CNV component was first described by W. Grey Walter and colleagues in an article published in Nature in 1964. The importance of this finding was that it was one of the first studies which showed that consistent patterns of the amplitude of electric responses could be obtained from the large background noise which occurs in EEG recordings and that this activity could be related to a cognitive process such as expectancy.

The P600 is an event-related potential (ERP) component, or peak in electrical brain activity measured by electroencephalography (EEG). It is a language-relevant ERP component and is thought to be elicited by hearing or reading grammatical errors and other syntactic anomalies. Therefore, it is a common topic of study in neurolinguistic experiments investigating sentence processing in the human brain.

The early left anterior negativity is an event-related potential in electroencephalography (EEG), or component of brain activity that occurs in response to a certain kind of stimulus. It is characterized by a negative-going wave that peaks around 200 milliseconds or less after the onset of a stimulus, and most often occurs in response to linguistic stimuli that violate word-category or phrase structure rules. As such, it is frequently a topic of study in neurolinguistics experiments, specifically in areas such as sentence processing. While it is frequently used in language research, there is no evidence yet that it is necessarily a language-specific phenomenon.

In neuroscience, the lateralized readiness potential (LRP) 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 activity of the brain that happens when a person gets ready to move one arm, leg, or foot. It is a special form of bereitschaftspotential. LRPs are recorded using electroencephalography (EEG) and have numerous applications in cognitive neuroscience.

Difference due to memory (Dm) 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. It is mainly discussed as an event-related potential (ERP) effect that appears in studies employing a subsequent memory paradigm, in which ERPs are recorded when a participant is studying a list of materials and trials are sorted as a function of whether they go on to be remembered or not in the test phase. For meaningful study material, such as words or line drawings, items that are subsequently remembered typically elicit a more positive waveform during the study phase. This difference typically occurs in the range of 400–800 milliseconds (ms) and is generally greatest over centro-parietal recording sites, although these characteristics are modulated by many factors.

The P3a, or novelty P3, is a component of time-locked (EEG) signals known as event-related potentials (ERP). 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. The P3a has been associated with brain activity related to the engagement of attention and the processing of novelty.

In neuroscience, the visual P200 or P2 is a waveform component or feature of the event-related potential (ERP) 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. The P2 component, also known as the P200, is so named because it is a positive going electrical potential that peaks at about 200 milliseconds after the onset of some external stimulus. This component is often distributed around the centro-frontal and the parieto-occipital areas of the scalp. It is generally found to be maximal around the vertex of the scalp, however there have been some topographical differences noted in ERP studies of the P2 in different experimental conditions.

<span class="mw-page-title-main">Visual N1</span>

The visual N1 is a visual evoked potential, a type of event-related electrical potential (ERP), 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 respect to an average mastoid reference. The "1" originally indicated that it was the first negative-going component, but it now better indexes the typical peak of this component, which is around 150 to 200 milliseconds post-stimulus. The N1 deflection may be detected at most recording sites, including the occipital, parietal, central, and frontal electrode sites. Although, the visual N1 is widely distributed over the entire scalp, it peaks earlier over frontal than posterior regions of the scalp, suggestive of distinct neural and/or cognitive correlates. The N1 is elicited by visual stimuli, and is part of the visual evoked potential – a series of voltage deflections observed in response to visual onsets, offsets, and changes. Both the right and left hemispheres generate an N1, but the laterality of the N1 depends on whether a stimulus is presented centrally, laterally, or bilaterally. When a stimulus is presented centrally, the N1 is bilateral. When presented laterally, the N1 is larger, earlier, and contralateral to the visual field of the stimulus. When two visual stimuli are presented, one in each visual field, the N1 is bilateral. In the latter case, the N1's asymmetrical skewedness is modulated by attention. Additionally, its amplitude is influenced by selective attention, and thus it has been used to study a variety of attentional processes.

Error-related negativity (ERN), sometimes referred to as the Ne, is a component of an event-related potential (ERP). ERPs are electrical activity in the brain as measured through electroencephalography (EEG) and time-locked to an external event or a response. A robust ERN component is observed after errors are committed during various choice tasks, even when the participant is not explicitly aware of making the error; however, in the case of unconscious errors the ERN is reduced. An ERN is also observed when non-human primates commit errors.

The late positive component or late positive complex (LPC) is a positive-going event-related brain potential (ERP) component that has been important in studies of explicit recognition memory. It is generally found to be largest over parietal scalp sites, beginning around 400–500 ms after the onset of a stimulus and lasting for a few hundred milliseconds. It is an important part of the ERP "old/new" effect, which may also include modulations of an earlier component similar to an N400. Similar positivities have sometimes been referred to as the P3b, P300, and P600. Here, we use the term "LPC" in reference to this late positive component.

The C1 and P1 are two human scalp-recorded event-related brain potential components, collected by means of a technique called electroencephalography (EEG). 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. It can be a negative-going component or a positive going component with its peak normally observed in the 65–90 ms range post-stimulus onset. The P1 is called the P1 because it is the first positive-going component and its peak is normally observed in around 100 ms. Both components are related to processing of visual stimuli and are under the category of potentials called visually evoked potentials (VEPs). Both components are theorized to be evoked within the visual cortices of the brain with C1 being linked to the primary visual cortex of the human brain and the P1 being linked to other visual areas. One of the primary distinctions between these two components is that, whereas the P1 can be modulated by attention, the C1 has been typically found to be invariable to different levels of attention.

<span class="mw-page-title-main">P3b</span>

The P3b is a subcomponent of the P300, an event-related potential (ERP) component that can be observed in human scalp recordings of brain electrical activity. The P3b is a positive-going amplitude peaking at around 300 ms, though the peak will vary in latency from 250 to 500 ms or later depending upon the task and on the individual subject response. Amplitudes are typically highest on the scalp over parietal brain areas.

The N170 is a component of the event-related potential (ERP) that reflects the neural processing of faces, familiar objects or words. Furthermore, the N170 is modulated by prediction error processes.

N2pc 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 vice versa. This characteristic makes it a useful tool for directly measuring the general direction of a person's attention with fine-grained temporal resolution.

References

  1. 1 2 3 4 5 6 7 Folstein, J. R., & Van Petten, C. (2008). Influence of cognitive control and mismatch on the N2 component of the ERP: A review. Psychophysiology, 45, 152-170.
  2. ↑ Sutton, S., Braren, M., & Zubin, J. (1965). Evoked-potential correlates of stimulus uncertainty. Science, 150, 1187-1188.
  3. ↑ Pfefferbaum, A., Ford, J. M., Weller, B. J., & Kopell, B. S. (1985). ERPs to response production and inhibition. Electroencephalography and Clinical Neurophysiology, 60, 423-434.
  4. 1 2 3 4 5 6 7 Patel, S. H., & Azzam, P. N. (2005). Characterization of N200 and P300: Selected studies of the event related potential. International Journal of Medical Sciences, 2, 147-154.
  5. 1 2 3 4 Azizian, A., Freitas, A. L., Parvaz, M. A., & Squires, N. K. (2006). Beware misleading cues: Perceptual similarity modulates the N2/P3 complex. Psychophysiology, 43, 253-260.
  6. ↑ Gajewski, P. D., Stoerig, P., & Falkenstein, M. (2008). ERP - Correlates of response selection in a response conflict paradigm. Brain Research, 1189, 127-134.
  7. 1 2 Heil, M., Osman, A., Wiegelmann, J., Rolke, B., & Henninghausen, E., (2000). N200 in the Eriksen-task: Inhibitory executive process?. Journal of Psychophysiology, 14, 218-225.
  8. ↑ Schmitt, B. M., Münte, T. F., & Kutas, M. (2000). Electrophysiological estimates of the time course of semantic and phonological encoding during implicit picture naming.Psychophysiology, 37, 473-484
  9. ↑ Amsel, B. D., Urbach, T. P., & Kutas, M. (2013). Alive and grasping: Stable and rapid semantic access to an object category but not object graspability. NeuroImage, 77, 1-13
  10. ↑ Hauk, O., Coutout, C., Holden, A., Chen, Y., 2012. The time-course of single-word reading: evidence from fast behavioral and brain responses. NeuroImage 60 (2), 1462–1477.
  11. ↑ Pfefferbaum, A., Ford, J. M., Weller, B. J., & Kopell, B. S. (1985). ERPs to response production and inhibition. Electroencephalography and Clinical Neurophysiology, 60, 423-434
  12. ↑ Donkers, F. C. L., & van Boxtel, G. J. M. (2004). The N2 in go/no-go tasks reflects conflict monitoring not response inhibition. Brain and Cognition, 56, 165-176
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