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 (e.g., presentation of a visual stimulus) or a response (e.g. an error of commission). 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; [1] however, in the case of unconscious errors the ERN is reduced. [2] [3] An ERN is also observed when non-human primates commit errors. [4]
The ERN was first discovered in 1968 by Natalia Bekhtereva and was called "error detector". [5] [6] Later in 1990 ERN was developed by two independent research teams; Michael Falkenstein, J. Hohnsbein, J. Hoormann, & L. Blanke (1990) at the Institute for Work Physiology and Neurophysiology in Dortmund, Germany (who called it the "Ne"), and W.J. "Bill" Gehring, M.G.H. Coles, D.E. Meyer & E. Donchin (1990) at the University of Michigan, USA. [7] [8] The ERN was observed in response to errors committed by study participants during simple choice response tasks.
The ERN is a sharp negative going signal which begins about the same time an incorrect motor response begins, (response locked event-related potential), and typically peaks from 80 to 150 milliseconds (ms) after the erroneous response begins (or 40-80 ms after the onset of electromyographic activity). [9] [10] [11] [12] [13] [2] The ERN is the largest at frontal and central electrode sites. [2] A typical method for determining the average ERN amplitude for an individual involves calculating the peak-to-peak difference in voltage between the average of the most negative peaks 1-150 ms after response onset, and the average amplitude of positive peaks 100-0 ms before response onset. [14] For optimal resolution of the signal, reference electrodes are typically placed behind both ears using either hardware or arithmetically linked mastoid electrodes. [10]
Any paradigm in which mistakes are made during motor responses can be used to measure the ERN. Natural keyboarding is one such example where typing errors are shown to elicit ERN. [15] The most important feature of any ERN paradigm is obtaining a sufficient number of errors in the participant's responses, and the number of trials needed to obtain reliable scores can vary widely, which is particularly relevant for studies of individual differences. [16] Early experiments identifying the component used a variety of techniques, including word and tone identification, and categorical discrimination (e.g. are the following an animal?). [8] [17] [18] However, the majority of experimental paradigms that elicit ERN deflections have been a variant on the Eriksen "Flanker", [14] [19] and "Go/NoGo". [20] In addition to responses with the hands, the ERN can also be measured in paradigms where the task is performed with the feet [21] or with vocal responses as in the Stroop paradigm. [22]
A standard Flanker task involves discerning the central "target" letter from a string of distracting "flanker" letters which surround it. For example, congruous letter strings such as "SSSSS" or "HHHHH" and incongruous letter strings such as "HHSHH" or "SSHSS" may be presented on a computer screen. Each target letter would be assigned a key stroke response on a keyboard, such as "S" = right shift key and "H" = left shift key. Presentation of each letter string is brief, generally less than 100 ms, and central on the screen. Participants have approximately 2000 ms to respond before the next presentation. The most simple Go/NoGo tasks involve assigning a property of discernment to responding "Go" or not responding "NoGo." For example, again congruous letter strings such as "SSSSS" or "HHHHH" and incongruous letter strings such as "HHSHH" or "SSHSS" may be presented on a computer screen. The participant could be instructed to respond by pressing the space bar, only for congruous strings, and to not respond when presented with incongruous letter strings. More complicated Go/NoGo tasks are usually created when the ERN is the component of interest however, because in order to observe the robust negativity errors must be made. The classic Stroop paradigm involves a color-word task. Color words such as "red, yellow, orange, green" are presented centrally on a computer screen either in a color congruent with the word, ("red" in the color red) or in a color incongruent with the word ("red" in the color yellow). Participants may be asked to verbalize the color each word is written in. Incongruent and congruent presentations of the words can be manipulated to different rates, such as 25/75, 50/50, 30/70 etc. Studies of ERN across flanker, Stroop, and Go/NoGo tasks support convergent validity of ERN, but convergent validity of ERN difference scores is not supported, suggesting there might task-specific differences in ERN difference scores. [23]
The amplitude of the ERN is sensitive to the intent and motivation of participants. When a participant is instructed to strive for accuracy in responses, observed amplitudes are typically larger than when participants are instructed to strive for speed. [14] Monetary incentives typically result in larger amplitudes as well. [24] Latency of the ERN peak amplitude can also vary between subjects, and does so reliably in special populations such as those diagnosed with ADHD, who show shorter latencies. [25] Participants with clinically diagnosed Obsessive Compulsive Disorder have exhibited ERN deflections with increased amplitude, prolonged latency, and a more posterior topography compared to clinically normal participants. [26] [27] [28] ERN latency has been manipulated through rapid feedback, wherein participants who received rapid feedback regarding the incorrect response subsequently showed shorter ERN peak latencies. [29] Additionally, a heightened ERN amplitude during social situations has been linked to anxiety symptoms in both childhood and adulthood. [30] [31] [32]
Developmental studies have shown that the ERN emerges throughout childhood and adolescence becoming more negative in amplitude and with a more defined peak. [33] [34] The ERN appears to be modulated by the environment during childhood, with children who experience early adversity showing evidence of less negative ERN amplitudes. [34] [35]
Although it is difficult to localize the origin of an ERP signal, extensive empirical research indicates that the ERN is most likely generated in the Anterior cingulate cortex (ACC) area of the brain. This conclusion is supported by fMRI, [36] [37] and brain lesion research, [38] as well as dipole source modeling. [39] The Dorsolateral prefrontal cortex (DLPFC) may also be involved in the generation of the ERN to some degree, and it has been found that persons with higher levels of "absent-mindedness" have their ERN sourced more from that region. [40] [41]
There is some debate within the field about what the ERN reflects (see especially Burle, et al. [42] ) Some researchers maintain that the ERN is generated during the detection of or response to errors. [43] [44] Others argue that the ERN is generated by a comparison process [13] [42] or a conflict monitoring system, [45] [46] and not specific to errors. In contrast to the above cognitive theories, new models suggest that the ERN may reflect the motivational significance of a task [47] or perhaps the emotional reaction to making an error. [48] This later view is consistent with findings linking errors and the ERN to autonomic arousal [49] and defensive motivated states, [50] and with findings suggesting that the ERN is dissociable from cognitive factors, but not affective ones. [48] [51] Unfortunately, it is still unclear how to interpret differences in sizes of ERN, as both smaller and larger ERN have been interpreted as "better". [52]
A stimulus locked event-related potential is also observed following the presentation of negative feedback stimuli in a cognitive task indicating the outcome of a response, often referred to as the feedback ERN (fERN). [53] This has led some researchers to extend the error-detection account of the response ERN (rERN) to a generic error detection system. This position has been elaborated into a reinforcement learning account of the ERN, arguing that both the rERN and the fERN are products of prediction error signals carried by the dopamine system arriving in the anterior cingulate cortex indicating that events have gone worse than expected. [54] In this framework it is common to measure both the rERN and the fERN as the difference in voltage between correct and incorrect responses and feedback, respectively.
Debates about psychiatric disorders often become "chicken and egg" conundrums; a relationship complicated by an incomplete understanding of the functional significance of ERN [52] . The ERN has been proposed as a potential arbitrator of this argument. A body of empirical research has shown that the ERN reflects a "trait" level difference in individual error processing; especially concerning anxiety, rather than a "state" level difference. [24] [55] For example; most people who experience depression do not feel depressed all of the time. Instead, they have periods of depressive "states" which may be minor and unique to an extreme situation such as death of a loved one, loss of employment, or major injury. However a person who has a depressive "trait" will have experienced more than one minor depressive "state" and usually at least one major depressive state, any of which may not be unique to an obviously extreme situation. [56] In fact, there is some evidence, albeit weak, that people with depression show small ERNs. [57] [58] Scientists are exploring the use of the ERN and other ERP signals in identifying people at risk for psychiatric disorders in hopes of implementing early interventions. People with addictive behaviors such as smoking, [59] alcoholism, [60] and substance abuse [55] have also shown differential ERN responses compared to individuals without the same addictive behavior.
The ERN is often preceded by a small positive voltage deflection with a latency in the interval of -200 to -50 milliseconds in the response-locked ERP in channels over the scalp vertex, which is sometimes referred to as the "positive peak preceding the Ne" or "PNe", [61] but more generally thought to reflect the pre-movement positivity (PMP) described by Deecke et al. (1969). [62] The PMP is thought to reflect a "go signal" by which pre-SMA and SMA permit a motor response to be carried out. [63] PMP is smaller before error motor responses than it is before correct motor responses, suggesting that it may be an important signal for discriminating erroneous from correct actions. Additionally, PMP is smaller in people who make more mistakes during the Flankers task and may have clinical utility in accident prone populations, such as youths with ADHD. [64]
The ERN is often followed by a positivity, known as the error-related positivity or Pe. The Pe is a positive deflection with a centro-parietal distribution. When elicited, the Pe can occur 200-500ms after making an incorrect response, following the error negativity (Ne, ERN), but is not evident on all error trials. [13] In particular, the Pe is dependent on awareness or ability to detect errors. [1] Pe is basically the same as the P300 wave associated with conscious sensations. [65] : 128 Additionally, Vocat et al. (2008) [66] established the Ne and Pe not only have different topographical distributions, but have different generators. Source localization indicates that the Ne has a dipole in the anterior cingulate cortex and the Pe has a dipole in the posterior cingulate cortex. The Pe amplitude reflects the perception of the error, meaning with more awareness of the error, the amplitude of the Pe is larger. Falkenstein and colleagues (2000) have shown that the Pe is elicited on uncorrected trials and false alarm trials, suggesting it is not directly related to error correction. It thus seems to be related to error monitoring, albeit with different neural and cognitive roots from the error-related processing reflected in the Ne.
If the Pe reflects conscious error processing, then it might be expected to be different for people with deficits in conflict monitoring, such as ADHD and OCD. Whether this is true remains controversial. Some studies do indicate these conditions are associated with different Pe responses, [67] [68] whereas other studies have not replicated those findings. [69] [70] The Pe has also been used to evaluate error processing in patients with severe brain traumatic injury. In a study using a variation of the Stroop task, patients with severe traumatic brain injury associated with deficits in error processing were found to show a significantly smaller Pe on error trials when compared against the healthy controls. [71]
Some researchers argue that error-related negativity or error-related positivity is in fact, reward-related positivity. Reward-related positivity is also referred to as reward positivity, or RewP. [72] It has been suggested that ERP data is depicting neural positivity to rewards (aka reward positivity) rather than neural negativity to loss (aka error-related negativity). Thus, this shift in how we conceptualize neural responses to gains/losses allows us to further understand the underlying neural processes.
In the human brain, the anterior cingulate cortex (ACC) is the frontal part of the cingulate cortex that resembles a "collar" surrounding the frontal part of the corpus callosum. It consists of Brodmann areas 24, 32, and 33.
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.
Affective neuroscience is the study of how the brain processes emotions. This field combines neuroscience with the psychological study of personality, emotion, and mood. The basis of emotions and what emotions are remains an issue of debate within the field of affective neuroscience.
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.
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.
In cognitive psychology, the Eriksen flanker task is a set of response inhibition tests used to assess the ability to suppress responses that are inappropriate in a particular context. The target is flanked by non-target stimuli which correspond either to the same directional response as the target, to the opposite response, or to neither. The task is named for American psychologists Barbara. A. Eriksen & Charles W. Eriksen, who first published the task in 1974, and for the flanker stimuli that surround the target. In the tests, a directional response is assigned to a central target stimulus. Various forms of the task are used to measure information processing and selective attention.
In neuroscience, the N100 or N1 is a large, negative-going evoked potential measured by electroencephalography ; 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. It is elicited by any unpredictable stimulus in the absence of task demands. It is often referred to with the following P200 evoked potential as the "N100-P200" or "N1-P2" complex. While most research focuses on auditory stimuli, the N100 also occurs for visual, olfactory, heat, pain, balance, respiration blocking, and somatosensory stimuli.
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.
Somatosensory evoked potential is the electrical activity of the brain that results from the stimulation of touch. SEP tests measure that activity and 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. SEP components include a series of positive and negative deflections that can be elicited by virtually any sensory stimuli. For example, SEPs can be obtained in response to a brief mechanical impact on the fingertip or to air puffs. However, SEPs are most commonly elicited by bipolar transcutaneous electrical stimulation applied on the skin over the trajectory of peripheral nerves of the upper limb or lower limb, and then recorded from the scalp. In general, somatosensory stimuli evoke early cortical components, generated in the contralateral primary somatosensory cortex (S1), related to the processing of the physical stimulus attributes. About 100 ms after stimulus application, additional cortical regions are activated, such as the secondary somatosensory cortex (S2), and the posterior parietal and frontal cortices, marked by a parietal P100 and bilateral frontal N140. SEPs are routinely used in neurology today to confirm and localize sensory abnormalities, to identify silent lesions and to monitor changes during surgical procedures.
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 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.
The oddball paradigm is an experimental design used within psychology research. Presentations of sequences of repetitive stimuli are infrequently interrupted by a deviant stimulus. The reaction of the participant to this "oddball" stimulus is recorded.
Meditation and its effect on brain activity and the central nervous system became a focus of collaborative research in neuroscience, psychology and neurobiology during the latter half of the 20th century. Research on meditation sought to define and characterize various practices. The effects of meditation on the brain can be broken up into two categories: state changes and trait changes, respectively alterations in brain activities during the act of meditating and changes that are the outcome of long-term practice.
William "Bill" Gehring is a psychologist, and in 2014 is the Arthur F. Thurnau Professor of Psychology at the University of Michigan in Ann Arbor, Michigan. He researches Event Related Potentials and is one of the discoverers of the Error Related Negativity. He has made contributions to the field of cognitive neuroscience through his studies on the electrophysiological markers of obsessive-compulsive disorder.
Mindfulness has been defined in modern psychological terms as "paying attention to relevant aspects of experience in a nonjudgmental manner", and maintaining attention on present moment experience with an attitude of openness and acceptance. Meditation is a platform used to achieve mindfulness. Both practices, mindfulness and meditation, have been "directly inspired from the Buddhist tradition" and have been widely promoted by Jon Kabat-Zinn. Mindfulness meditation has been shown to have a positive impact on several psychiatric problems such as depression and therefore has formed the basis of mindfulness programs such as mindfulness-based cognitive therapy, mindfulness-based stress reduction and mindfulness-based pain management. The applications of mindfulness meditation are well established, however the mechanisms that underlie this practice are yet to be fully understood. Many tests and studies on soldiers with PTSD have shown tremendous positive results in decreasing stress levels and being able to cope with problems of the past, paving the way for more tests and studies to normalize and accept mindful based meditation and research, not only for soldiers with PTSD, but numerous mental inabilities or disabilities.
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