Event-related potential

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Event-related potentials (ERPs) are small, transient voltages generated in the brain in response to specific sensory, cognitive, or motor events or stimuli, recorded noninvasively from the scalp using electroencephalography (EEG) techniques.^[1] These potentials reflect the summed postsynaptic activity of large populations of cortical pyramidal neurons and are derived by averaging EEG signals time-locked to repeated presentations of the eliciting event, which enhances signal-to-noise ratio by reducing background brain activity.^[2] ERPs provide high temporal resolution on the order of milliseconds, allowing researchers to track the rapid unfolding of neural processing from early sensory responses to later cognitive evaluations.^[3] The history of ERPs traces back to early observations of brain electrical activity in the 19th century, with foundational work by Richard Caton in the 1870s demonstrating electrical currents in animal brains, followed by Hans Berger's invention of human EEG in 1929.^[1] The modern ERP technique emerged in the 1960s through the development of signal averaging methods, which enabled the extraction of stimulus-locked responses from noisy EEG data; a landmark discovery was the P300 component by Sutton et al. in 1965, linked to decision-making and attention.^[3] Subsequent advancements, including digital computing and multichannel recordings, have solidified ERPs as a cornerstone of cognitive neuroscience since the 1970s, with key contributions from researchers like Steven Hillyard on attentional modulation of sensory components.^[3] ERPs are characterized by distinct waveform components, each associated with specific stages of information processing, such as the early sensory N1 (around 100 ms post-stimulus, reflecting initial perceptual analysis), the mismatch negativity (MMN, 100–250 ms, indicating automatic detection of deviant stimuli), and the later P300 (250–400 ms, involved in context updating and attention).^[2] Other prominent components include the N400 (300–600 ms, sensitive to semantic incongruities in language processing) and the late positive potential (LPP, linked to emotional evaluation).^[2] These components vary in polarity (positive or negative deflection), latency, scalp distribution, and eliciting conditions, providing a temporal map of brain function.^[1] Applications of ERPs span cognitive, clinical, and developmental neuroscience, offering insights into perception, attention, memory, and language without relying on overt behavior, which is particularly advantageous for studying infants, patients with communication disorders, or those with altered consciousness.^[3] In clinical settings, ERPs serve as biomarkers for disorders like schizophrenia (e.g., reduced P300 amplitude)^[1], Alzheimer's disease (e.g., attenuated N400)^[3], and autism (e.g., atypical MMN)^[4], aiding diagnosis and tracking disease progression. Recent methodological improvements, such as portable EEG systems and advanced analysis techniques, have expanded their use in real-world and longitudinal studies, complementing imaging methods like fMRI by emphasizing temporal dynamics over spatial localization.^[2]

Fundamentals

Definition and characteristics

Event-related potentials (ERPs) are averaged electrical potentials recorded from the scalp that reflect the brain's synchronized neural activity in response to specific sensory, cognitive, or motor events. These potentials are time-locked to the onset of the stimulus or event, allowing for the measurement of transient brain responses that are otherwise obscured in ongoing electroencephalographic (EEG) activity. ERPs provide a direct index of neural processing with high temporal fidelity, capturing the timing of cognitive and perceptual operations on the order of milliseconds.^[1]^[5] Key characteristics of ERPs include their millisecond temporal precision, which enables the dissection of rapid neural events, and their recording via noninvasive scalp electrodes as part of EEG setups. Amplitudes typically range from 1 to 20 microvolts, making them subtle signals that require averaging across multiple trials to isolate from background noise. ERP waveforms consist of a series of positive (P) and negative (N) voltage deflections relative to a prestimulus baseline period, with polarity, latency, and scalp distribution used to describe their morphology. These potentials are influenced by factors such as stimulus characteristics, attentional states, and task demands, which can modulate their amplitude and timing.^[1]^[6]^[7]^[8] Physiologically, ERPs arise primarily from the summation of postsynaptic potentials in synchronously active pyramidal neurons within the cerebral cortex, reflecting coordinated excitatory and inhibitory processes across neural populations. This cortical origin distinguishes ERPs from subcortical contributions, which are less prominent in scalp recordings due to volume conduction effects. The reliance on synchronous activity underscores why ERPs are sensitive to disruptions in neural timing, such as those seen in various neurological conditions.^[1]^[6]^[5]

Relation to EEG and brain activity

Electroencephalography (EEG) measures continuous fluctuations in electrical voltage on the scalp, which originate from ionic currents flowing through the dendrites of synchronously active pyramidal neurons in the cerebral cortex. These fluctuations reflect the summed postsynaptic potentials generated by millions of neurons, primarily in superficial cortical layers, and are transmitted to the scalp via volume conduction through the head's tissues, including the skull and scalp. Event-related potentials (ERPs) represent a specific subset of this EEG activity, consisting of the portions that are time-locked and phase-synchronized to discrete sensory, cognitive, or motor events, thereby isolating them from the ongoing background neural noise.^[3] The extraction of ERPs from raw EEG signals relies on their temporal alignment to repeated stimulus presentations or events, as the event-locked components are typically too weak—on the order of microvolts—to be discernible amid the larger amplitude of spontaneous EEG activity without processing. By time-locking EEG epochs to the onset of events and averaging across multiple trials (often hundreds), the consistent phase-locked responses add constructively, while random, non-synchronized EEG variations cancel out, enhancing the signal-to-noise ratio. This process underscores that ERPs are not standalone signals but derived measures embedded within the broader EEG, requiring precise synchronization to reveal underlying brain responses to specific stimuli.^[1] ERPs are predominantly generated by cortical neural sources, such as the primary visual cortex for responses to visual stimuli, where synchronous activation of neuronal populations produces detectable scalp potentials. These signals propagate through volume conduction, where the electrical fields spread non-invasively across conductive tissues like cerebrospinal fluid, skull, and scalp, resulting in smoothed and attenuated recordings at the electrodes. To infer the locations of these neural generators, dipole modeling is commonly employed, treating active neural ensembles as equivalent current dipoles whose orientations and positions are estimated by fitting the observed scalp topography; for instance, equivalent dipole analysis has localized auditory ERP sources to supratemporal cortical areas. More advanced distributed source models, such as eLORETA, further refine this by estimating current density across the entire cortical surface without assuming a fixed number of dipoles, improving localization accuracy when integrated with realistic head models derived from MRI.^[9] In contrast to spontaneous EEG, which encompasses ongoing oscillatory rhythms like alpha waves (8-12 Hz) that are not tied to specific events and reflect intrinsic brain states, ERPs capture evoked, phase-locked activity that is directly elicited by and synchronized to external or internal events. Spontaneous EEG includes both phase-locked (evoked) and non-phase-locked (induced) components, but standard ERP analysis focuses exclusively on the former, filtering out asynchronous oscillations that do not align across trials. This distinction highlights ERPs' utility in probing deterministic neural responses, whereas spontaneous EEG better characterizes the brain's baseline dynamics and variability.^[3]

History

Early discoveries

The discovery of electroencephalography (EEG) in the 1920s by Hans Berger marked the pre-ERP era, where spontaneous brain electrical activity was recorded from the human scalp without synchronization to specific events or stimuli. Berger's initial recordings, starting in 1924 and first published in 1929, revealed rhythmic oscillations such as alpha waves but lacked the temporal alignment necessary to isolate responses to discrete events, limiting insights into stimulus-driven brain activity.^[10]^[11] Early ERP-like observations emerged in the late 1930s through studies of evoked responses to sensory stimuli. In 1935–1936, Hallowell Davis and Pauline Davis recorded the first unambiguous sensory ERPs from awake humans, publishing findings in 1939 on auditory evoked potentials elicited by clicks, which demonstrated small, time-locked voltage changes amid ongoing EEG noise. These manual recordings highlighted the potential for event-synchronized brain signals but were obscured by background activity without advanced extraction methods. Advancements in the 1950s focused on techniques to enhance evoked response visibility. George Dawson pioneered superimposition methods in the late 1940s, manually aligning and overlaying multiple EEG traces to reveal averaged somatosensory and visual evoked potentials, as detailed in his 1951 and 1954 publications. This analog approach improved signal detection for weak responses to stimuli like electrical nerve shocks or light flashes, establishing the foundation for quantitative ERP analysis without digital tools. A key milestone in the 1960s was the introduction of computer-based averaging, which enabled precise extraction of ERPs from noisy EEG data. Robert Galambos and colleagues published the first computer-averaged ERP waveforms in 1962, using digital summation to isolate auditory responses in humans and animals, dramatically increasing signal-to-noise ratios. Concurrently, W. Grey Walter identified the contingent negative variation (CNV) in 1964, a slow negative shift preceding expected stimuli in a warning-imperative paradigm, representing an early cognitive ERP component linked to anticipation and motor preparation. In 1965, Samuel Sutton and colleagues discovered the P300 component, a positive deflection around 300 ms post-stimulus associated with decision-making and attention to rare events.^[12]

Key developments and researchers

In the 1970s, Emanuel Donchin played a pivotal role in standardizing event-related potential (ERP) techniques and establishing their utility in cognitive neuroscience. His research focused on the P300 component, demonstrating its sensitivity to subjective probability and decision-making processes, which helped transition ERPs from mere physiological signals to tools for probing higher-order cognition.^[13] Donchin's work on endogenous ERP components, including advancements in signal processing and averaging, facilitated the widespread adoption of ERPs for studying information processing stages.^[14] During the 1980s and 1990s, ERP research expanded through integrations with cognitive psychology, notably in attention studies led by Michael Posner, who employed ERPs to map attentional networks and their developmental trajectories.^[15] Steven Hillyard advanced understanding of selective attention by identifying early ERP modulations, such as enhanced negativity to attended stimuli, revealing sensory gain mechanisms in visual and auditory processing.^[16] Concurrently, Marta Kutas pioneered the study of language-related components, discovering the N400 in 1980 as an index of semantic integration and expectancy violations during sentence comprehension.^[17] This era also saw the development of event-related fields (ERFs) using magnetoencephalography (MEG), providing complementary spatiotemporal insights into ERP generators as MEG technology matured.^[18] Key figures like Hillyard, Kutas, and Donchin not only refined ERP methodologies but also influenced nomenclature and experimental paradigms, solidifying ERPs as a cornerstone of cognitive neuroscience.^[19] From the 2000s onward, technological advancements included high-density electrode arrays, enabling improved spatial resolution for source localization in ERP studies, as exemplified by systems supporting up to 256 channels.^[20] The introduction of open-source software like EEGLAB in 2004 democratized ERP analysis, offering tools for independent component analysis and event-related spectral perturbations under a MATLAB framework.^[21] These innovations propelled applications in developmental neuroscience, where ERPs have illuminated early cognitive milestones, such as face processing and executive function maturation in infants and children.^[22]

Methodology

Data acquisition and recording

Data acquisition for event-related potentials (ERPs) begins with the precise placement of electrodes on the scalp to capture neural activity. The standard International 10-20 system is widely used, positioning electrodes at 10% or 20% intervals along the skull's perimeter relative to anatomical landmarks such as the nasion and inion, ensuring consistent and replicable recordings across studies.^[23] For higher spatial resolution in ERP research, high-density arrays with 64 to 256 channels are employed, often following extensions like the 10-10 or 5% systems to better map topographic distributions.^[24] A reference electrode is typically placed on the mastoid or earlobe, with a ground electrode on the forehead or mastoid to minimize noise, and all electrode impedances must be checked and maintained below 5 kΩ to ensure signal quality and reduce artifacts from poor contact.^[25] Hardware components are critical for faithful amplification and digitization of the low-amplitude EEG signals underlying ERPs. EEG amplifiers feature high input impedance (greater than 10 GΩ) to avoid loading the scalp potentials, coupled with a common-mode rejection ratio exceeding 100 dB to suppress environmental noise.^[26] Sampling rates of at least 500 Hz are standard to adequately capture ERP components up to 30 Hz without aliasing, achieved through anti-aliasing low-pass filters set just below half the sampling frequency (e.g., a 250 Hz cutoff for 500 Hz sampling).^[27] Analog-to-digital conversion uses at least 12-bit resolution to preserve the microvolt-level signals.^[26] In the experimental paradigm, ERPs are elicited by presenting repeated stimuli to evoke time-locked brain responses, such as in the oddball task where infrequent target stimuli (e.g., 20% probability) are interspersed among frequent standards to generate components like the P300.^[26] Precise synchronization between stimulus onset and EEG recording is ensured via trigger pulses sent from the presentation software to the EEG system, typically with jitter less than 1 ms, to align epochs accurately.^[25] Artifact minimization is prioritized by instructing participants to minimize blinks and movements, and by recording electrooculogram (EOG) channels above and below the eyes to detect and later correct ocular artifacts.^[26] Initial preprocessing steps prepare the raw EEG data for ERP extraction while preserving signal integrity. A bandpass filter of 0.1-30 Hz is commonly applied to remove slow drifts and high-frequency noise, using non-causal offline filters like FIR to avoid distortion.^[28] Noisy trials are rejected based on amplitude thresholds, such as ±100-200 μV at any electrode, to exclude those contaminated by artifacts like muscle activity or blinks, ensuring at least 20-30 artifact-free trials per condition for reliable averaging.^[26]

Signal processing and averaging

Extracting event-related potentials (ERPs) from raw electroencephalographic (EEG) data requires segmenting the continuous recordings into discrete time-locked epochs and applying computational techniques to enhance the signal while suppressing noise. Epoching involves dividing the EEG data into short segments, typically spanning from 200 ms before to 800 ms after the onset of a stimulus or event of interest, allowing analysis of brain responses aligned to specific triggers.^[29] This process ensures that transient neural activity evoked by the event is isolated for further processing, with epoch lengths chosen to capture the duration of the expected ERP components without introducing excessive unrelated background activity.^[3] Baseline correction is a critical preprocessing step performed during or immediately after epoching to normalize the voltage levels and remove slow drifts unrelated to the event. It subtracts the mean voltage over a prestimulus baseline period, commonly the 100-200 ms interval immediately before stimulus onset, from each epoch to center the ERP waveform around zero and account for pre-event brain state variations.^[29] This correction mitigates offsets caused by electrode drifts or slow fluctuations, improving the reliability of subsequent amplitude measurements.^[3] Noise reduction techniques are essential prior to averaging, as EEG signals contain substantial ongoing brain activity and artifacts that can obscure the ERP. Trial rejection identifies and discards epochs contaminated by large artifacts, such as eye blinks or muscle movements, often using amplitude thresholds (e.g., exceeding ±100 μV) to exclude outliers and preserve data quality.^[30] Baseline subtraction further aids noise mitigation by removing low-frequency drifts, while optional bandpass filtering, such as a low-pass filter at 40 Hz, attenuates high-frequency noise without distorting the primary ERP frequencies, which typically range from 0.1 to 30 Hz.^[29] The core method for ERP extraction is signal averaging across multiple epochs, which enhances the event-locked response by exploiting the fact that the ERP is phase-locked to the stimulus while background EEG noise averages to zero over sufficient trials. The standard averaging formula is given by:

\text{ERP}(t) = \frac{1}{N} \sum_{i=1}^{N} \left[ \text{EEG}_i(t) - \text{baseline} \right]

where N is the number of accepted trials, \text{EEG}_i(t) is the voltage at time t for the i-th trial, and baseline is the mean prestimulus voltage. This technique, pioneered in the mid-20th century, reduces noise variance proportionally to $1/\sqrt{N}, typically requiring 20-100 trials for reliable ERPs depending on signal strength.^[31] Advanced techniques build on basic averaging to further improve signal quality. Weighted averaging assigns variable weights to individual trials based on their signal-to-noise ratio or reliability, rather than equal weights, to emphasize cleaner epochs and enhance overall ERP fidelity, particularly useful when trial quality varies.^[32] Independent component analysis (ICA) provides a powerful approach for artifact removal by decomposing the EEG into statistically independent components, allowing ocular or muscular artifacts to be identified and subtracted without rejecting entire trials, thus maximizing usable data. Additionally, baseline drift correction addresses residual slow-wave artifacts through techniques like polynomial fitting or high-pass filtering applied post-epoching, ensuring stable ERP baselines across sessions.^[30]

Component identification and nomenclature

Event-related potential (ERP) components are identified and named based on their polarity, peak latency, and sometimes topographic distribution over the scalp. Polarity is denoted by "P" for positive deflections and "N" for negative ones, with latency approximated in milliseconds post-stimulus onset (e.g., N100 for a negative peak around 100 ms). Topographic labels, drawn from the international 10-20 system, may be appended to indicate scalp location, such as Pz for the parietal midline site (e.g., P300 at Pz). This nomenclature facilitates consistent reference across studies, though exact latencies can vary with stimulus type, task demands, and individual factors. Components emerge from averaged EEG epochs aligned to stimuli, revealing time-locked brain responses otherwise obscured by background noise.^[33] Early sensory components reflect initial perceptual processing. The N1 (or N100) is a negative deflection peaking 50-150 ms post-stimulus, primarily over auditory or visual cortices, indexing basic sensory feature detection and early attention modulation.^[33] It is modulated by stimulus intensity and novelty, with larger amplitudes for abrupt onsets. The P1 (or P50), an earlier positive wave around 50-100 ms, arises from primary sensory areas and supports sensory gating, filtering irrelevant inputs to prioritize relevant stimuli.^[33] Cognitive components capture higher-order processing. The mismatch negativity (MMN) is a negative fronto-central wave (100-250 ms) elicited automatically by deviant stimuli in a repetitive sequence, reflecting pre-attentive change detection without focused attention.^[33] It originates from superior temporal gyrus and is sensitive to auditory or visual irregularities.^[33] The P300, a broad positive centro-parietal peak around 300 ms in oddball tasks, signals context updating and resource allocation, with subcomponents P3a (frontal, novelty detection) and P3b (parietal, target evaluation).^[33] The N400, a posterior negative wave peaking near 400 ms, indexes semantic integration difficulties, such as incongruent words in sentences, and is prominent in language tasks.^[33] Late components involve prolonged or anticipatory activity. The late positive potential (LPP) is a sustained positive deflection starting 300-800 ms post-stimulus, maximal over parietal sites, associated with enhanced attention to emotionally arousing content.^[34] It reflects motivated processing and can be modulated by emotion regulation strategies.^[34] The contingent negative variation (CNV) is a slow negative build-up (500-2000 ms) between a warning and imperative stimulus, frontally distributed, indicating anticipatory attention and motor preparation.^[35] It comprises early (orienting) and late (response readiness) phases.^[35]

Strengths and Limitations

Temporal and spatial resolution

Event-related potentials (ERPs) provide exceptional temporal resolution, allowing researchers to measure brain electrical activity with millisecond precision, often down to 1 ms increments depending on the sampling rate of the recording system.^[36] This high fidelity enables the tracking of rapid cognitive processes, such as early perceptual stages occurring in 50 ms intervals following stimulus onset. For instance, components like the N1 wave, which reflects initial sensory processing, can be resolved within approximately 100 ms post-stimulus.^[37] The temporal accuracy stems from the direct recording of postsynaptic potentials, which unfold over tens to hundreds of milliseconds, making ERPs ideal for dissecting the sequence of neural events in cognition.^[38] In contrast, the spatial resolution of ERPs is relatively coarse, typically limited to 3-4 cm on the scalp surface due to the blurring effects of volume conduction through the skull and tissues.^[39] This limitation arises from the inverse problem in electroencephalography (EEG), where multiple neural sources can produce similar scalp distributions, preventing precise localization of brain activity without additional modeling.^[36] Studies indicate that effective resolution may extend to 5-9 cm in some cases, influenced by factors such as cortical folding and the orientation of active neural populations.^[40] As a result, ERPs excel at revealing broad topographic patterns, such as frontal versus parietal maxima, but struggle to pinpoint subcortical or deeply embedded generators.^[41] Several factors modulate the resolution of ERPs. For temporal fidelity, the sampling rate must adhere to the Nyquist theorem, requiring at least twice the frequency of the highest neural signal component (typically 200-500 Hz for ERPs) to avoid aliasing and preserve millisecond-scale details.^[42] Spatial resolution improves with higher electrode density; for example, systems with 128 or more channels can better delineate scalp fields compared to the standard 10-20 montage, though source localization still demands computational models like dipole fitting or beamforming.^[43] These trade-offs highlight ERPs' strength in time-domain analysis over precise anatomical mapping, distinguishing them from techniques with superior spatial but poorer temporal capabilities.^[36]

Invasiveness, portability, and cost

Event-related potentials (ERPs) are recorded using electroencephalography (EEG), a completely non-invasive technique that involves placing electrodes on the scalp to measure electrical activity without requiring surgery or penetration of the skin. This method causes minimal discomfort, typically limited to the application of conductive gel or paste to ensure good electrode contact, and poses no significant health risks. ERPs are safe for participants of all ages, including infants and the elderly, as well as individuals with clinical disorders such as autism, schizophrenia, or Parkinson's disease, making it suitable for diverse populations without the need for sedation.^[44]^[45]^[44] The portability of ERP systems has been enhanced by advancements in wireless and lightweight EEG hardware, allowing recordings in mobile or natural environments beyond traditional laboratory settings. Wireless EEG devices, such as those with active electrodes and scalable amplifiers, enable unconstrained participant movement during tasks, facilitating field studies in clinics, schools, hospitals, or everyday contexts like ambulatory monitoring. These systems support ERP research by capturing event-related brain responses in ecologically valid scenarios, with over 110 high-impact studies demonstrating their utility across various applications and channel configurations.^[44]^[46]^[46] ERP measurement is economically advantageous, with basic EEG equipment for research costing between $15,000 and $100,000, and disposable supplies like electrodes adding only $1–$3 per session, far lower than techniques like MRI or MEG that require multimillion-dollar installations and ongoing maintenance. Open-source software tools, such as the ERPLAB Toolbox integrated with EEGLAB, further reduce expenses by providing free platforms for data analysis without proprietary licensing fees, though skilled expertise is needed for effective implementation. Ethically, ERPs involve no exposure to radiation or invasive procedures, promoting high participant compliance and minimizing risks, which aligns with principles of beneficence and non-maleficence in research involving vulnerable groups.^[44]^[47]^[48]

Comparisons to other techniques

Event-related potentials (ERPs) offer distinct advantages over behavioral measures by providing direct, online neural data that precedes and informs overt responses, allowing researchers to track cognitive processes in real time with millisecond precision.^[49] For instance, the error-related negativity (ERN), an early ERP component peaking around 50-80 ms post-response, detects conflict monitoring and error detection before conscious awareness or behavioral correction, enabling dissociation of automatic neural processes that behavioral metrics alone cannot reveal.^[49]^[50] This temporal sensitivity is particularly valuable in social cognitive research, where ERPs can isolate early automatic responses (e.g., initial face encoding via N170) from later evaluative stages, independent of participants' behavioral performance.^[49] In comparison to functional magnetic resonance imaging (fMRI), ERPs excel in temporal resolution, capturing neural events on the order of milliseconds rather than the seconds required for fMRI's hemodynamic response.^[2] Conversely, fMRI provides superior spatial resolution, localizing activity to millimeters, while ERPs are limited to centimeters due to volume conduction across the scalp.^[2]^[51] Unlike fMRI, which indirectly measures blood oxygenation level-dependent changes, ERPs directly reflect postsynaptic neural activity, avoiding confounds from vascular variability.^[2] ERPs and magnetoencephalography (MEG) share comparable high temporal resolution for tracking dynamic brain processes, both achieving millisecond-scale precision.^[2] However, MEG signals are less susceptible to distortion by the skull and scalp, offering better source localization than ERPs, which suffer from electrical field smearing.^[52] MEG systems, requiring superconducting sensors and shielded rooms, are significantly more expensive and less portable than ERP setups, limiting their use in diverse clinical or field settings.^[53] As a non-invasive alternative to invasive techniques like electrocorticography (ECoG), ERPs enable broad accessibility without surgical risks, using scalp electrodes to record averaged neural responses.^[2] Yet, ERPs exhibit lower signal-to-noise ratios due to attenuation through skull and tissue, whereas ECoG provides higher-fidelity recordings directly from the cortical surface.^[54] This trade-off positions ERPs as a practical first-line tool for initial investigations, with invasive methods reserved for precise, high-resolution needs in specialized contexts.^[55]

Applications

Clinical diagnostics and assessments

Event-related potentials (ERPs) play a crucial role in clinical diagnostics for neurological disorders, particularly through specialized evoked potentials that assess sensory pathway integrity. The auditory brainstem response (ABR), an early ERP component elicited by auditory stimuli, is widely used to diagnose hearing loss, especially in infants and non-verbal patients, by measuring neural synchrony from the auditory nerve to the brainstem; absent or prolonged wave latencies indicate peripheral or central auditory deficits.^[56] Similarly, visual evoked potentials (VEPs), which capture cortical responses to visual stimuli, aid in detecting optic nerve damage, such as in optic neuritis or demyelinating diseases, where delayed P100 peak latencies signal conduction delays along the visual pathway.^[57] These techniques provide objective, non-invasive measures of sensory function when behavioral testing is unreliable.^[58] In psychiatric diagnostics, ERPs reveal attentional and cognitive impairments characteristic of disorders like schizophrenia. Reductions in P300 amplitude, an endogenous ERP component reflecting attention and working memory updating, are consistently observed in schizophrenia patients, correlating with attention deficits and disease severity; this attenuation is evident in oddball paradigms and persists across illness stages.^[59] Mismatch negativity (MMN), a pre-attentive ERP indexing automatic deviance detection, shows alterations in individuals at clinical high risk for psychosis, with reduced MMN amplitudes predicting transition to full psychosis and serving as a biomarker for early intervention.^[60] For developmental assessments, ERPs help evaluate neurodevelopmental conditions such as autism spectrum disorder (ASD). In ASD, the N170 component, associated with face processing, exhibits reduced amplitude and delayed latency to facial stimuli, indicating atypical perceptual expertise for social cues like faces compared to objects.^[61] ERPs also serve as prognostic tools in critical care settings. During neurosurgery, intraoperative monitoring of somatosensory and motor ERPs detects real-time changes in neural conduction, allowing surgeons to adjust procedures and prevent permanent deficits in spinal or brain operations.^[62] For coma outcome prediction, middle-latency auditory evoked potentials (MLAERPs), including components like Pa and Nb, predict awakening and functional recovery; preserved MLAERPs in post-anoxic coma correlate with favorable outcomes, enhancing prognostic accuracy beyond clinical exams.^[63]

Cognitive and neuroscience research

Event-related potentials (ERPs) have been instrumental in elucidating the temporal dynamics of cognitive processes in healthy individuals, providing millisecond-level insights into neural mechanisms underlying perception, attention, memory, and higher-order functions. By averaging EEG signals time-locked to stimuli or responses, researchers isolate components that reflect stages of information processing, from early sensory encoding to evaluative decision-making.^[64] This approach allows for the examination of how neural activity supports adaptive behavior in controlled experimental settings, revealing patterns of activation that correlate with task performance and cognitive efficiency.^[65] In studies of attention and perception, the N2/P3 complex emerges as a key marker in selective attention tasks, where the N2 component, peaking around 200-300 ms post-stimulus, indexes conflict detection and inhibitory control during target discrimination.^[66] The subsequent P3, a positive deflection at 300-600 ms, reflects attentional resource allocation and context updating, with larger amplitudes for attended stimuli in oddball paradigms.^[67] Similarly, the lateralized readiness potential (LRP), a slow negative shift contralateral to the responding hand starting about 800 ms before movement, tracks motor preparation and response selection, dissociating central decision processes from peripheral execution in choice reaction time tasks. For memory and learning, ERPs reveal dissociable neural signatures of recognition processes, such as the FN400, a frontal negativity at 300-500 ms elicited by familiar but not recollected items, supporting models of familiarity-based retrieval without episodic detail.^[68] In decision-making, the error-related negativity (ERN), a frontocentral negativity peaking 50-100 ms after erroneous responses, signals performance monitoring and adaptive adjustments, linking anterior cingulate activity to reinforcement learning. These components highlight how ERPs capture the rapid feedback loops that refine learning through error detection and memory consolidation. Language processing elicits the N400, a widespread negativity at 300-500 ms to semantic anomalies, such as unexpected word endings in sentences, indicating integrative access to lexical meaning and contextual prediction. In emotion research, the late positive complex (LPC), a sustained positivity from 400-800 ms over parietal sites, amplifies for arousing stimuli like threatening images, reflecting enhanced motivational salience and sustained attentional engagement. Cross-disciplinary applications enhance ERP interpretation through integration with functional magnetic resonance imaging (fMRI) for source estimation, constraining dipole models to activated brain regions and improving localization of components like the P3 to temporoparietal junctions. Developmental studies further utilize ERPs to track component maturation, showing progressive reduction in P3 latency and increase in amplitude from childhood to adulthood, paralleling prefrontal development and cognitive control refinement.^[69] Emerging applications as of 2025 include the integration of ERPs in brain-computer interfaces for medical rehabilitation and secure user authentication, enabling real-time decoding of neural intent.^[70]^[71]

Experimental design considerations

In event-related potential (ERP) studies, the number of trials per condition is a critical factor for achieving adequate signal-to-noise ratio (SNR), as ERPs are derived from averaging multiple epochs to extract weak neural signals from background EEG noise. A minimum of 20-30 artifact-free trials per condition is typically recommended to ensure reliable SNR, though this can vary based on component size and noise levels; for example, smaller effects like the feedback-related negativity may require at least 20 trials for non-clinical samples. The SNR improves with the square root of the number of trials (N), following the relation \text{SNR} \propto \sqrt{N}, because noise averages out randomly while the signal adds coherently. Power analysis should guide trial numbers by considering expected effect sizes; for instance, simulations show that 16 trials per condition can yield high power (>0.8) for effects of at least 3 μV in within-subject designs, but larger samples enhance detection of smaller effects common in cognitive research. Paradigm design in ERP experiments must balance stimulus presentation to minimize confounds while maximizing data quality. Event-related designs, where stimuli from different conditions are presented in a randomized or jittered sequence, are preferred for isolating transient responses to specific events, allowing precise time-locking without overlap from sustained activity. In contrast, blocked designs group similar stimuli into contiguous sequences, which can enhance SNR for sustained processes but risk anticipatory effects or adaptation. Counterbalancing is essential in within-subject designs—where each participant experiences all conditions—to control for order effects, such as by using Latin square or randomized orders across participants. Between-subject factors, assigning participants to different conditions, reduce carryover but require larger samples to account for inter-individual variability; within-subject approaches are often favored in ERP for their power efficiency. Statistical analysis of ERPs typically involves quantifying peak amplitudes and latencies within predefined time windows for components of interest, followed by inferential tests. Mean or peak amplitude measures capture effect magnitudes, while latency indices reflect processing speed differences; these are often analyzed using repeated-measures ANOVA to assess condition or group effects on waveforms or extracted metrics. For spatiotemporal analyses across multiple electrodes and time points, corrections for multiple comparisons are necessary to control family-wise error rates, such as through cluster-based permutation tests or the global field power (GFP), which summarizes variance across channels without requiring electrode-specific adjustments and preserves power. Key challenges in ERP experimental design include habituation effects, where repeated stimulus exposure diminishes neural responses over trials, potentially confounding condition comparisons if not randomized or monitored via trial binning. Individual variability in component latencies also poses issues, as trial-to-trial or between-subject shifts can smear peaks in averaged waveforms, reducing apparent amplitudes and necessitating techniques like latency correction or single-trial analyses to maintain sensitivity.

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We have conducted behavioral, developmental, and patient studies using functional magnetic resonance imaging (fMRI), event related potentials (ERP) ...
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Event-related brain potentials in the study of visual selective attention
ERP modulations during spatial attention point toward a mechanism of gain control over information flow in extrastriate visual cortical pathways, starting about ...
[15]
Thirty years and counting: Finding meaning in the N400 component ...
We overview the discovery, characterization, and evolving use of the N400, an event-related brain potential response linked to meaning processing.
[16]
EEG and MEG: Relevance to Neuroscience - ScienceDirect.com
Dec 4, 2013 · Many EEG/MEG studies in the field of neurocognition concern time-locked-evoked or event-related potentials (ERPs) or magnetic fields (ERFs), ...
[17]
[PDF] Event-related potentials (ERPs) and cognitive processing - MedEd
As objective signs of cognitive operations, abnormal ERP waveforms have diagnostic significance for information-processing disorders associated with ...
[18]
[PDF] The five percent electrode system for high-resolution EEG and ERP ...
Abstract. Objective: A system for electrode placement is described. It is designed for studies on topography and source analysis of spontaneous and.
[19]
EEGLAB: an open source toolbox for analysis of single-trial EEG ...
Mar 15, 2004 · We have developed a toolbox and graphic user interface, EEGLAB, running under the crossplatform MATLAB environment (The Mathworks, Inc.) for processing ...
[20]
Use of Event-Related Potentials in the Study of Typical and Atypical ...
In this paper we focus our attention on one particular tool – the recording of the event-related potential (ERP).
[21]
[PDF] Guidelines for Standard Electrode Position Nomenclature
This system provides a consistent and replicable method of recording EEG with 21 electrodes placed at relative distances (10% or 20%) between cranial landmarks ...
[22]
The five percent electrode system for high-resolution EEG and ERP ...
A system for electrode placement is described. It is designed for studies on topography and source analysis of spontaneous and evoked EEG activity.
[23]
Electroencephalography (EEG) and Event-Related Potentials ... - NIH
Many EEG researchers utilize an event-related potential (ERP) experimental design, in which a large number of time-locked experimental trials are averaged ...
[24]
(PDF) Guidelines for Using Human Event-Related Potentials to ...
Event-related potentials (ERPs) recorded from the human scalp can provide important information about how the human brain normally processes information.
[25]
How to decide which EEG amplifier best fits your research
Aug 25, 2022 · For example, to properly record Event Related Potentials within a frequency range between 1 Hz and 50 Hz, a sampling rate >250 – 500 Hz should ...Missing: anti- | Show results with:anti-
[26]
Optimal Filters for ERP Research II: Recommended Settings for ...
We have previously recommended a bandpass of 0.1–30 Hz for most cognitive and affective studies (Luck, 2014). In most of these cases, little or no justification ...
[27]
Guidelines for using human event‐related potentials to study ...
Mar 19, 2003 · Event-related potentials (ERPs) recorded from the human scalp can provide important information about how the human brain normally processes information.
[28]
[PDF] Chapter 4: Averaging, Artifact Rejection, and Artifact Correction
Because ERPs are embedded in a larger EEG signal, almost all ERP studies rely on some sort of averaging procedure to minimize the. EEG noise, and the averaging ...
[29]
Tribute to George Duncan Dawson - PMC - NIH
In 1951, the physiologist George Duncan Dawson presented his work with the averaging of the signal in the evoked potentials (EPs), opening a new stage in the ...
[30]
Weighted averaging of evoked potentials - ADS
Weighted averages of brain evoked potentials (EPs) are obtained by weighting each single EP sweep prior to averaging. These weights are shown to maximize ...
[31]
https://pmc.ncbi.nlm.nih.gov/articles/PMC9648911/
[32]
The late positive potential: a neurophysiological marker for emotion ...
The late positive potential (LPP) is an ERP that reflects facilitated attention to emotional stimuli (Cuthbert, Schupp, Bradley, Birbaumer, & Lang, 2000 ...
[33]
Contingent negative variation: a biomarker of abnormal attention in ...
Contingent negative variation (CNV) is a negative cortical wave that precedes a pre‐cued imperative stimulus requiring a quick motor response.
[34]
https://pmc.ncbi.nlm.nih.gov/articles/PMC3019134/
[35]
https://pmc.ncbi.nlm.nih.gov/articles/PMC7982797/
[36]
[PDF] Best Practices for Event-Related Potential Research in Clinical ...
This is what gives the ERP technique such excellent temporal resolution. Postsynaptic potentials last tens to hundreds of milliseconds and may be occurring ...
[37]
Improved Spatial Resolution of Electroencephalogram Using ...
Jun 8, 2020 · Since EEG is considered to have spatial resolution of 3.0 to 4.0 cm [15–17], we tested at a higher spatial resolution for comparison.
[38]
Spatial and temporal resolutions of EEG: Is it really black and white ...
Such volume–conduction-induced mixture is the main cause of the poor spatial resolution of scalp EEG (around 5 to 9 cm, Nunez et al., 1994; Babiloni et al., ...
[39]
[PDF] 1 Interpreting Event-Related Brain Potentials
Here we restrict discussion to event-related brain potentials (ERPs), which are small changes in the electrical activity of the brain that are recorded from ...
[40]
ERP CORE: An open resource for human event-related potential ...
Jan 15, 2021 · Event-related potentials (ERPs) are noninvasive measures of human brain activity that index a range of sensory, cognitive, affective, ...
[41]
Very high density EEG elucidates spatiotemporal aspects of early ...
Nov 24, 2017 · We compared “super-Nyquist” density EEG (“SND”) with Nyquist density (“ND”) arrays for assessing the spatiotemporal aspects of early visual processing.
[42]
Best Practices for Event-Related Potential Research in Clinical ... - NIH
Practically speaking, ERPs are inexpensive compared to other neuroscience techniques (including the magnetic cousin of EEG, magnetoencephalography [MEG]), with ...
[43]
ERP evidence of preserved early memory function in term infants ...
Aug 16, 2016 · ERPs are noninvasive and do not require sedation or behavioral responses from infants, making them an ideal mode for studying newborns. One ...Missing: safe | Show results with:safe
[44]
Wireless EEG: A survey of systems and studies - ScienceDirect.com
Apr 1, 2023 · this paper first provides a list of 48 wireless EEG devices along with a number of important—sometimes difficult-to-obtain—features and ...
[45]
https://www.nature.com/articles/pr2016169
[46]
ERPLAB Toolbox - ERP Info
Mar 25, 2023 · ERPLAB Toolbox is a free, open-source Matlab package for analyzing ERP data. It is tightly integrated with EEGLAB Toolbox, extending EEGLAB's capabilities.
[47]
ERP approaches for social cognitive and affective neuroscience - PMC
Another major advantage of ERPs over traditional behavioral measures, as mentioned previously, is the ability to measure psychological processes independently ...
[48]
Error awareness and the error-related negativity: evaluating the first ...
In the cognitive neuroscience of error processing, the discovery of an event-related brain potential (ERP) whose amplitude is different depending on the success ...
[49]
Brain Imaging Techniques and Their Applications in Decision ... - NIH
Event-related potentials (ERPs) are associated with specific stimuli or thoughts. ... In contrast, fMRI has high spatial resolution and a comprehensive ...
[50]
Brain Computer Interfaces, a Review - PMC - PubMed Central
The advantage of MEG is that magnetic fields are less distorted by the skull and scalp than electric fields [48]. Magnetic fields are detected by ...
[51]
Detecting large‐scale networks in the human brain using high ... - NIH
However, applications of MEG for large‐scale studies remain limited, mainly because MEG is not portable and has high maintenance costs.
[52]
Temporal alignment of electrocorticographic recordings for upper ...
The signals obtained using these electrodes generally have higher SNR, a wider bandwidth, and higher spatial resolution when compared to electroencephalography ...
[53]
Improved P300 speller performance using electrocorticography ...
Mar 5, 2013 · Recent studies have suggested that electrocorticography (ECoG) signals could be used in BCI communication due to its increased signal-to-noise ...
[54]
Auditory Brainstem Response - StatPearls - NCBI Bookshelf
Jan 12, 2023 · ... ABR can be used to monitor for developing hearing loss.[10] In addition to hearing loss, ABR can be used to diagnose vestibular schwannomas ...Continuing Education Activity · Introduction · Indications · Technique or Treatment
[55]
Visual Evoked Potential - StatPearls - NCBI Bookshelf
VEPs are the expression of the electrical activity of the visual pathways up to the optic nerve to the calcarine cortex.
[56]
Electrophysiological assessment of optic nerve disease | Eye - Nature
Nov 8, 2004 · The visual-evoked cortical potential (VEP) is an important electrophysiological test in the investigation of suspected optic nerve disease.
[57]
P300 reduction and prolongation with illness duration in schizophrenia
Mar 1, 2000 · Background: The P300 component of the auditory event-related potential (ERP) is both reduced in amplitude and delayed in schizophrenia.Missing: seminal | Show results with:seminal
[58]
Mismatch negativity (MMN) as a tool for translational investigations ...
In CHR study, reduction of double deviant (duration and frequency) MMN significantly predicted the time to psychosis onset (Perez et al., 2014). Because ...
[59]
Atypicality of the N170 Event-Related Potential in Autism Spectrum ...
Autism spectrum disorder (ASD) is associated with impaired face processing. The N170 event-related potential (ERP) has been considered a promising neural marker ...
[60]
Complex event-related potentials (P300 and CNV) and MSLT in the ...
The P300 and contingent negative variation (CNV) evoked potential (EP) paradigms were performed by 12 untreated narcoleptics and controls immediately prior ...
[61]
Intraoperative Neurophysiological Monitoring - StatPearls - NCBI - NIH
Intraoperative neurophysiological monitoring (IONM) helps assess the integrity of neural structures and consciousness during surgical procedures.
[62]
Predictive value of sensory and cognitive evoked potentials for ...
The estimated probability of awakening rose to 87% when N100 was present and to 89.9% when middle-latency evoked potentials (MLAEPs) were present. It was 13.7% ...
[63]
Cognitive flexibility and N2/P3 event-related brain potentials - Nature
Jun 17, 2020 · Event-related brain potentials (ERPs) served as primary outcomes, which were measured to reveal whether the neural networks for resolving ...
[64]
Electrophysiological correlates of selective attention: A lifespan ...
Jan 31, 2008 · The most prominent ERP components observed in studies of selective attention using the auditory oddball paradigm are N1, P2, N2 and P3, with ...Discussion · Methods · Eeg Data Reduction And...
[65]
The N2-P3 complex of the evoked potential and human performance
May 1, 1988 · The N2-P3 complex reflects processes of stimulus evaluation, perceptual resource allocation, and decision making that proceed in parallel.
[66]
Predictive validity of the N2 and P3 ERP components to executive ...
Feb 20, 2014 · SEM analyses found that both the N2 difference waveform and P3b (thought to be electrophysiological correlates of response conflict/inhibition ...
[67]
The FN400 indexes familiarity-based recognition of faces - PMC - NIH
Separate event-related brain potential (ERP) components have been hypothesized to index familiarity and recollection processes that support recognition memory.Missing: seminal | Show results with:seminal
[68]
Maturation of action monitoring from adolescence to adulthood
This study investigated the development of the frontal lobe action-monitoring system from late childhood and adolescence to early adulthood using ERP markers ...Missing: seminal | Show results with:seminal