Knowledge Tree
Electroencephalography
Also known as: EEG
synthesized from dimensionsElectroencephalography (EEG) is a non-invasive neuroimaging technique used to measure the electrical activity and frequency of brain waves produced by synchronized groups of neurons EEG measures electrical activity. By monitoring these electrical signals, EEG provides a window into large-scale brain activity patterns EEG for large-scale activity, offering a critical tool for both clinical diagnostics and fundamental neuroscience research.
The technical execution of EEG involves the precise placement of electrodes on the scalp, often facilitated by digitizing electrode positions using systems such as Polhemus to ensure spatial accuracy digitizer for EEG electrodes. Data acquisition typically requires rigorous signal processing, with standard procedures involving bandpass filtering between 0.01 and 330 Hz at a sampling rate of 1,000 Hz EEG data filtering specs. Once collected, this data is analyzed using specialized software suites such as MNE MNE processes EEG and FieldTrip FieldTrip analyzes EEG.
In clinical and research settings, EEG is frequently paired with other modalities to enhance diagnostic or analytical power. For instance, it is used in conjunction with electromyography (EMG) to distinguish between various sleep stages by simultaneously assessing brain and muscle electrical activity sleep stages using EEG. Furthermore, in the study of consciousness, materialist frameworks utilize EEG alongside functional magnetic resonance imaging (fMRI) to identify and map brain networking areas materialists use EEG for consciousness.
A significant advancement in consciousness research is the Perturbational Complexity Index (PCI), which combines transcranial magnetic stimulation (TMS) with EEG to assess brain complexity PCI uses TMS and EEG. By measuring the EEG response to TMS-induced perturbations, the PCI provides a highly discriminative metric for evaluating states of consciousness PCI measures EEG response. Additionally, EEG serves as an ancillary method in pharmacological research, such as in studies investigating the effects of psychedelic drugs psychedelics studies employ EEG.
While EEG is valued for its high temporal resolution—making it particularly effective for observing rapid brain dynamics, such as those found in synergistic workspace frameworks EEG for workspace dynamics—it is constrained by its spatial limitations. Compared to intracranial electrophysiology, EEG offers lower spatiotemporal resolution intracranial surpasses EEG. Despite these physical constraints, EEG remains an indispensable, versatile methodology for mapping the electrical signatures of the human brain.
Model Perspectives (1)
openrouter/x-ai/grok-4.1-fast 75% confidence
Electroencephalography (EEG) measures the electrical activity and frequency of brain waves produced by groups of neurons, according to Paul C. Mocombe in the Biomedical Journal of Scientific & Technical Research EEG measures electrical activity. It is used alongside electromyography (EMG) to distinguish sleep stages by assessing brain and muscle electrical activity, as described in the Psychedelic Review sleep stages using EEG. EEG features in neuroscience studies on psychedelic drugs as an ancillary method after primary fMRI use, per Nature psychedelics studies employ EEG. In consciousness research, materialists employ EEG with fMRI to identify brain networking areas, claims Mocombe materialists use EEG for consciousness, and Yuri Saalmann notes it monitors large-scale brain activity patterns (Templeton World Charity Foundation) EEG for large-scale activity. The Perturbational Complexity Index (PCI), deemed highly discriminative for consciousness by eLife, combines transcranial magnetic stimulation (TMS) with EEG to assess brain complexity, as detailed by Lavazza and Massimini (Springer) PCI uses TMS and EEG and PCI measures EEG response. Software like MNE (Gramfort et al., NeuroImage) processes EEG data MNE processes EEG, FieldTrip (Oostenveld et al.) analyzes it FieldTrip analyzes EEG, and procedures involve digitizing electrode positions with Polhemus systems (Nature) digitizer for EEG electrodes. EEG offers lower spatiotemporal resolution than intracranial electrophysiology (PLOS ONE) intracranial surpasses EEG but high temporal resolution for frameworks like synergistic workspace (eLife) EEG for workspace dynamics. Data are typically bandpass filtered 0.01-330 Hz at 1,000 Hz sampling (Nature) EEG data filtering specs.
Facts (117)
Sources
Neuro-insights: a systematic review of neuromarketing perspectives ... frontiersin.org 64 facts
referenceHsu and Chen (2020) utilized EEG and questionnaires to study Dual process theory across pre-purchase, purchase, and post-purchase stages.
referenceZhao (2022) applied Service Dominant Logic (SDL) in a study using EEG, IRT, and questionnaires.
referenceGorin et al. (2022) utilized electroencephalography (EEG) to study brand association.
referenceXu et al. (2023) applied brand personality theory in a study using EEG, GSR, and questionnaires.
referenceZhang et al. (2021) utilized EEG (ERP) and IRT to study the Repetition Effect, Repetition Suppression, and Celebrity Effect across pre-purchase, purchase, and post-purchase stages, with a focus on affective responses.
referenceHakim et al. (2021) utilized EEG, machine learning (ML), and questionnaires to study ML models across pre-purchase and purchase stages.
referenceDavidson's influential approach-withdrawal motivation model was utilized in a 2022 study employing HR, GSR, EEG, and questionnaires to analyze neuromarketing perspectives.
referenceSavelli et al. (2022) utilized implicit priming tests, eye-tracking, electroencephalography (EEG), questionnaires, and focus groups to study communication strategies for the food and tourism industry.
claimLin, M. H., Cross, S. N., Jones, W. J., and Childers, T. L. (2018) applied electroencephalography (EEG) to consumer neuroscience research in the European Journal of Marketing.
referenceGarczarek-Bak et al. (2021) utilized electroencephalography (EEG), electrodermal activity (EDA), and eye-tracking (ET) to predict brand choice.
referenceLi et al. (2023b) utilized electroencephalography (EEG) to study destination advertisement effectiveness.
referenceCirović et al. (2024) utilized Aristotelian persuasion theory in a study combining EEG, eye-tracking (ET), and questionnaires.
referenceHakim et al. (2021) utilized electroencephalography (EEG) and machine learning (ML) to study food preference prediction.
claimResearchers argue that EEG sensors are more effective than galvanic skin response (GSR), photoplethysmography (PPG), and fMRI because EEG allows for insights into moment-by-moment changes in emotional expression.
claimThe compatibility of virtual reality (VR) technology with EEG recording systems allows researchers to create experimental experiences with a higher degree of ecological validity and control.
referenceSavelli et al. (2022) applied signaling theory in a study using implicit priming tests, eye-tracking, EEG, questionnaires, and focus groups.
referenceAdalarasu et al. (2025) utilized electroencephalography (EEG) to study advertisement endorsement.
claimMagnetoencephalography (MEG) is often considered to have excellent time resolution and to capture deeper neural activity better than Electroencephalography (EEG).
referenceWajid et al. (2021) utilized EEG and a moment-by-moment picture sort technique scale to study the SOR Model, Dual system Model, and Approach-avoidance Model across pre-purchase, purchase, and post-purchase stages, with a focus on affective responses.
referenceLee et al. (2007) demonstrated that techniques such as eye-tracking, fMRI, and EEG reveal neural triggers that influence consumer preferences and intentions.
referenceGorin et al. (2022) utilized semantic theory in a study using EEG and questionnaires.
claimIntegrating eye-tracking with electroencephalography (EEG) allows researchers to link visual attention to brain activity, helping identify which elements of a product or advertisement influence purchase intent.
referenceSimonetti et al. (2024) utilized electroencephalography (EEG) to study advertising effectiveness.
claimEEG captures event-related potentials (ERPs) that reflect emotional and cognitive responses, while fMRI identifies brain regions involved in reward processing, attention, and decision-making.
referenceMengual-Recuerda et al. (2021) utilized electroencephalography (EEG) and galvanic skin response (GSR) to study hospitality and gastronomy in tourism.
claimIntegrating multiple neuroimaging techniques, such as fMRI, EEG, and eye-tracking, allows researchers to simultaneously capture neural, physiological, and attentional data to provide a more holistic view of the consumer decision-making process.
claimSteady State Topography (SST) is a variant of electroencephalography (EEG) that measures the speed of information processing in the brain by detecting electrical potentials.
referenceKakaria et al. (2023b) applied SOR Theory in a study using EEG, VR, and questionnaires.
referenceZhao (2022) utilized electroencephalography (EEG) and implicit response testing to study product service system (PSS) design and development for value co-creation and conflict resolution.
claimMcInnes, A. N., Sung, B., and Hooshmand, R. (2023) provided a practical review of the value of electroencephalography (EEG) to consumer research, published in the International Journal of Market Research.
claimEEG and fMRI studies indicate that the prefrontal cortex shows increased activity during logical assessments, while the amygdala shows increased activity in response to emotional elements related to branding or perceived product value.
claimNeuroscientific techniques such as EEG, fMRI, and eye-tracking can evaluate consumer behavior across decision-making stages, including need recognition, evaluation, and post-purchase, by measuring real-time neural responses.
referenceIzadi et al. (2022) utilized electroencephalography (EEG) to study promotional strategies for sports marketing.
referenceHerrando et al. (2022) utilized galvanic skin response (GSR) and electroencephalography (EEG) to study online customer reviews.
referenceLi, S., Lyu, T., Park, S., and Choi, Y. (2023b) published 'Spillover effects in destination advertising: an electroencephalography study' in Annals of Tourism Research, volume 102, article 103623.
claimEEG has the highest temporal resolution among all neuroimaging techniques, capable of measuring electrical signals in sub-millisecond intervals.
referenceFondevila i Gascón et al. (2020) and Pozharliev et al. (2022a,b) utilized electrodermal activity (EDA), eye-tracking (ET), and electroencephalography (EEG) to study influencer marketing.
referenceWajid et al. (2021) utilized electroencephalography (EEG) to study social media marketing.
referenceBaldo et al. (2022) report that advertisement effectiveness is measured using Heart Rate (HR), Galvanic Skin Response (GSR), and Electroencephalography (EEG).
referencePanda et al. (2024) utilized electroencephalography (EEG) to study customer choice.
referencePozharliev et al. (2022a,b) utilized the Behavioral Activation System (BAS), Behavioral Inhibition System (BIS), dual coding theory, and the social media influencer value model (SMIV) in a study using eye-tracking (ET) and EEG.
referenceLi et al. (2023b) applied excitation transfer theory in a study using EEG.
referencePanda et al. (2024) published 'Spatial attention-enhanced EEG analysis for profiling consumer choices' in IEEE Access, which details a method for using EEG analysis to profile consumer choices.
claimMarketing and consumer research increasingly utilize neurometric techniques, including fMRI, EEG, MEG, SST, TMS, fNIRS, and PET, to understand consumer decision-making processes.
claimThe combination of Transcranial Magnetic Stimulation and electroencephalography (TMS-EEG) functions as an 'excitability probe,' where the EEG output reflects the excitability of the underlying cortex at the time the TMS pulse is delivered.
referenceHassani et al. (2022) utilized electroencephalography (EEG) to measure advertisement effectiveness.
claimAmbulatory EEG equipment can introduce measurement error, making virtual reality (VR) technology a viable alternative for creating real-life-like experiences in a neuroscience laboratory setting.
referenceXu et al. (2023) utilized electroencephalography (EEG) and galvanic skin response (GSR) to study brand personality.
referenceCosta-Feito, González-Fernández, Rodríguez-Santos, and Cervantes-Blanco (2023) performed a science mapping approach to analyze the use of electroencephalography (EEG) in consumer behavior and marketing research.
claimHsu and Chen (2020) utilized EEG (electroencephalography) to study the effects of subliminal advertising on hotel selection in a neuromarketing context.
referenceRecent neuromarketing research includes studies by Tan and Lee (2024) using fMRI and questionnaires; Ülker et al. (2025) using GSR, PPG, and questionnaires; Xu and Liu (2024) using EEG; Zhang et al. (2024) using fMRI and questionnaires to study consumer wellbeing; Adalarasu et al. (2025) using EEG and questionnaires to study emotional intelligence; Khubchandani and Raman (2025) using eye-tracking (ET) and questionnaires to study SOR Theory; Lopez-Navarro et al. (2025) using EEG, EDA, and questionnaires to study perception; Marques et al. (2025) using EDA and FEA to study the Elaboration Likelihood Model (ELM); Šola et al. (2025) using eye-tracking (ET) to study the Technology Acceptance Model (TAM); and Yu et al. (2025) using fNIRS to study anthropomorphism and pro-social behavior.
referenceHsu and Chen (2020) utilized electroencephalography (EEG) to study hotel selection and hospitality marketing.
claimGehring and Willoughby (2002) demonstrated that EEG studies can capture event-related potentials (ERPs), such as error-related negativity (ERN), which indicate post-purchase regret or dissatisfaction.
referenceAlvino et al. (2020) utilized EEG and questionnaires to study consumer behavior across pre-purchase, purchase, and post-purchase stages.
referenceZhang et al. (2021) utilized electroencephalography (EEG) and Item Response Theory (IRT) to study social networking services (SNS) marketing.
referenceKakaria et al. (2023b) utilized electroencephalography (EEG), virtual reality (VR), and questionnaires to study virtual reality applications.
referenceVela and Paredes (2023) and Li et al. (2023a) utilized electroencephalography (EEG) to study tourism.
referenceIzadi et al. (2022) applied SOR Theory in a study using EEG, questionnaires, and focus group discussions (FGDs).
referenceXu et al. (2023) provided EEG and GSR evidence regarding the neurophysiological mechanisms underlying brand personality consumer attraction.
referenceCirović et al. (2024) utilized electroencephalography (EEG) and eye-tracking (ET) to study environmentally sustainable marketing communication.
referenceAlvino et al. (2020) utilized electroencephalography (EEG) to study product experience via wine tasting.
claimEEG studies detect event-related potentials (ERPs), specifically the P300 and late positive potential (LPP), which serve as indicators of cognitive and emotional processing during consumer decision-making.
referenceHerrando et al. (2022) applied emotion contagion and the theory of arousal in a study using GSR, EEG, and questionnaires.
claimElectroencephalography (EEG) and functional magnetic resonance imaging (fMRI) reveal neural activity associated with attention, memory, and emotion.
What Neuroscience Tells Us About Consumer Desire - Baker Library library.hbs.edu Mar 26, 2012 8 facts
claimUma Karmarkar notes that advertisers have been successfully influencing human behavior and brain responses to some extent since long before the invention of EEG or fMRI technology.
claimNeuroscientists typically use either electroencephalography (EEG) or functional magnetic resonance imaging (fMRI) technology to track brain functions.
accountIn 2008, Frito-Lay hired a neuromarketing firm to analyze consumer responses to Cheetos, the top-selling brand of cheese puffs in the United States, using EEG technology.
claimEEG allows subjects to move around during testing, whereas fMRI requires subjects to lie very still inside a machine that exerts a strong magnetic field.
claimEEG technology is limited because the electrode cap sits on the surface of the head, preventing researchers from accessing deep areas of the brain.
claimElectroencephalography (EEG) measures fluctuations in electrical activity directly below the scalp resulting from neural activity.
claimEEG research determined that consumers respond strongly to the fact that eating Cheetos turns their fingers orange with residual cheese dust, indicating a sense of giddy subversion.
quoteThe August 2011 issue of Fast Company described how EEG patterns indicated 'a sense of giddy subversion that consumers enjoy over the messiness of the product' regarding Cheetos.
Adversarial testing of global neuronal workspace and ... - Nature nature.com Apr 30, 2025 7 facts
procedureThe researchers used a Polhemus Isotrack 3D digitizer system to collect the locations of head fiducials, head shape, 64 EEG electrode positions, and head position indicator (HPI) coil locations relative to anatomical landmarks.
referenceThe MNE software package is designed for processing MEG and EEG data, as described in Gramfort et al., NeuroImage 86, 446–460 (2014).
referenceEngemann and Gramfort (2015) describe automated model selection in covariance estimation and spatial whitening of MEG and EEG signals in NeuroImage 108, 328–342.
referenceMaris and Oostenveld (2007) describe nonparametric statistical testing methods for EEG and MEG data.
referenceMultivariate pattern analysis (MVPA) can be used to compare representational structures in time and space for MEG and EEG data.
procedureHead position on the MEG system was monitored using four HPI coils placed on the EEG cap, positioned next to the left and right mastoids and over the left and right frontal areas, measured at the start and end of each run and before and after each resting period.
measurementMEG and EEG data were bandpass filtered between 0.01 and 330 Hz and sampled at a rate of 1,000 Hz during acquisition.
Theories and Methods of Consciousness biomedres.us Jan 29, 2024 4 facts
referenceKim H, Hudetz A G, Lee J, Mashour G A, Lee U, et al. published 'Estimating the Integrated Information Measure Phi from High Density Electroencephalography during States of Consciousness in Humans' in Frontiers in Human Neuroscience in 2018.
claimMaterialists aim to identify the networking areas of the brain that produce conscious processes (contents and states of consciousness) using neuroscience techniques such as EEG, fMRI, and rMRI.
claimEvidence from recordings involves neuroscientists recording brain waves using sensitive electronic devices like electroencephalograms (EEGs), such as the observation that occipital alpha waves decrease when individuals see or imagine visual objects.
claimElectroencephalography (EEG) measures the electrical activity and frequency of brain waves produced by groups of neurons.
Exploring “lucid sleep” and altered states of consciousness using ... philosophymindscience.org Jan 7, 2025 3 facts
referenceFieldTrip is an open-source software package designed for the advanced analysis of MEG, EEG, and invasive electrophysiological data, as described by Oostenveld, Fries, Maris, and Schoffelen (2011).
referenceThe pilot study 'EEG correlates of consciousness during sleep' by Mason, L. I., Alexander, C. N., Travis, F. T., & Gackenbach, J. was published in Lucidity Letter (Volume 9) in 1990.
procedureIn the case series study, sleep was monitored using wearable EEGs and submental EMGs.
Global Versus Local Theories of Consciousness and the ... link.springer.com 3 facts
claimLavazza and Massimini claim that the perturbational complexity index (PCI) method could be adapted to organoids if transcranial magnetic stimulation (TMS) and electroencephalography (EEG) were replaced with more subtle measurement tools.
procedureThe perturbational complexity index (PCI) methodology uses transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG) recording to measure brain complexity.
claimThe Perturbational Complexity Index (PCI) utilizes Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG) as its primary tools for assessing consciousness in the human brain.
Physiology, Sleep Stages - StatPearls - NCBI Bookshelf - NIH ncbi.nlm.nih.gov 3 facts
procedurePolysomnography is a clinical sleep evaluation procedure that utilizes an electroencephalogram (EEG), electrooculogram, electromyogram, electrocardiogram, pulse oximetry, airflow, and respiratory effort monitoring.
claimDuring the wake stage, EEG recordings show beta waves (highest frequency, lowest amplitude) during eye-open wakefulness, while alpha waves are seen during quiet or relaxed wakefulness.
claimREM sleep is associated with dreaming and is characterized by beta waves on an EEG, which are similar to brain waves during wakefulness.
Protocol for testing global neuronal workspace and integrated ... journals.plos.org 3 facts
referenceThe paper 'FieldTrip: Open source software for advanced analysis of MEG, EEG, and invasive electrophysiological data' was published by Oostenveld R, Fries P, Maris E, and Schoffelen J-M in Computational Intelligence and Neuroscience in 2011 (Volume 2011, Article 156869, PMID 21253357).
claimIntracranial electrophysiology provides higher spatiotemporal resolution for measuring neuronal population spiking activity compared to fMRI, EEG, or ECoG.
procedureThe Cogitate research project tested predictions regarding consciousness theories in 250 subjects using fMRI, EEG, MEG, and implanted ECoG electrodes, employing several decoding analyses.
Quantum Theory of Consciousness - Scirp.org. scirp.org 3 facts
claimKoenig reported that brainwaves, specifically alpha (8-12 Hz), beta (12-30 Hz), and gamma (30-100 Hz) ranges, show similarity to Schumann resonances and a tendency for electroencephalogram (EEG) rhythms to become synchronous with Schumann resonance activity.
claimPobachenko et al. found that variations in electroencephalogram (EEG) readings were correlated with changes in the Schumann resonance across the daily cycle.
claimPersinger et al. found that the power within electroencephalogram (EEG) spectral profiles had repeated periods of coherence with the first three Schumann resonance frequencies (7-8 Hz, 13-14 Hz, and 19-20 Hz) in real time.
The New Field of Network Physiology: Building the Human ... frontiersin.org 2 facts
claimLi et al. (2020) utilize adaptive fractal and network analysis to distinguish epileptiform discharges from normal electroencephalograms.
claimLioi et al. (2017) show that directional connectivity in the electroencephalogram (EEG) can discriminate between wakefulness and non-rapid eye movement (NREM) sleep.
Conflicting States of Consciousness: Exploring Psilocin and Sleep psychedelicreview.com May 25, 2022 2 facts
procedureSleep stages are distinguished using electroencephalography (EEG) to measure electrical activity in the brain and electromyography (EMG) to measure electrical activity in the muscles.
quote“Definitely the most surprising result of this study was the effect on sleep homeostasis that we found, both in that it only occurred on a local level (in the LFP) and not in the EEG, and also that it manifested as a change in the rate of slow wave recovery, rather than initial amplitude, which is the typical consequence of increased sleep pressure after sleep deprivation.”
Why Sleep Matters: Consequences of Sleep Deficiency sleep.hms.harvard.edu 2 facts
claimContinual wakefulness beyond approximately 16 hours leads to measurable changes in brain activity, as recorded by an electroencephalogram (EEG), which correspond to lower alertness and a propensity to sleep.
claimSleep deprivation causes noticeable changes in brain activity as measured by an electroencephalogram (EEG), which correspond to lower alertness and a propensity to sleep.
Short- and long-term health consequences of sleep disruption dovepress.com May 19, 2017 2 facts
claimThe American Academy of Sleep Medicine's newer sleep classification system focuses on electroencephalogram (EEG) derivations and merges the historical Stages 3 and 4 into a single Stage N3.
claimInsomniacs exhibit increased EEG activity, abnormal hormone secretion, increased metabolic activity, and increased sympathetic nervous system activity throughout the day and night.
A Synergistic Workspace for Human Consciousness Revealed by ... elifesciences.org 2 facts
claimTime-resolved extensions of the synergistic workspace framework, such as those developed by Varley and colleagues, may clarify the dynamics of the synergistic workspace when combined with high temporal resolution neuroimaging like magnetoencephalography or electroencephalography.
claimThe Perturbational Complexity Index (PCI) is considered one of the most discriminative indices of consciousness available to date, as it measures the brain's EEG response to brief magnetic pulses.
Extent and Health Consequences of Chronic Sleep Loss and ... - NCBI ncbi.nlm.nih.gov 2 facts
claimEEG recordings of individuals with sleeping sickness in Gambia show periods of REM sleep occurring throughout the entire sleep-wake cycle, often without normal intermediate NREM periods.
referencePrinz et al. studied sleep, EEG, and mental function changes in senile dementia of the Alzheimer’s type, published in Neurobiology of Aging in 1982.
Neuroimaging in psychedelic drug development: past, present, and ... nature.com Sep 27, 2023 1 fact
claimNeuroscience studies on psychedelic drugs have primarily utilized functional Magnetic Resonance Imaging (fMRI), with ancillary research employing Magnetoencephalography (MEG) or Electroencephalography (EEG).
Marketing and Consumer Psychology - iResearchNet business-psychology.iresearchnet.com 1 fact
measurementA perfume brand increased online clicks by 300% by using a sensual advertisement that was tested via EEG to ensure it synced with brain pleasure pathways.
Physiology of Sleep - StatPearls - NCBI Bookshelf - NIH ncbi.nlm.nih.gov 1 fact
claimElectroencephalography (EEG) involves non-invasively placing electrodes across the scalp to measure voltage fluctuations and electrical activity within the brain.
Sleep Across the Lifespan: A Neurobehavioral Perspective link.springer.com Feb 5, 2025 1 fact
referenceGorgoni et al. (2020) analyzed the relationship between sleep electroencephalography (EEG) developmental trajectories and cognitive functioning in Sleep Medicine.
Global Workspace vs. Integrated Information: Testing… templetonworldcharity.org 1 fact
quoteYuri Saalmann states that the key goal of the project is to obtain data that informs theories of consciousness at a small scale, noting that previous human consciousness research using functional MRI or EEG techniques only monitored large-scale brain activity patterns.
Consciousness and AI - Open Encyclopedia of Cognitive Science oecs.mit.edu Feb 5, 2026 1 fact
claimMethods to test for consciousness in nonhuman animals and patients with brain damage typically rely on behavior or brain recordings, such as functional magnetic resonance imaging (fMRI) or electroencephalogram (EEG), according to Tim Bayne et al. (2024).
Sleep Deprivation: What It Is, Symptoms, Treatment & Stages my.clevelandclinic.org Aug 11, 2022 1 fact
procedureAn electroencephalogram (EEG) is a test that detects and records brain waves, allowing neurologists to examine brain activity for signs that may contribute to sleep problems.