EEG

Extracted Attributes

• Full Name

  Electroencephalography

• Amplitude Range

  20 to 100 μV

• Frequency Range

  1 to 30 Hz (standard human range)

• Beta Wave Frequency

  13–30 Hz

• Temporal Resolution

  Millisecond-range

• Alpha Wave Frequency

  8–13 Hz

• Delta Wave Frequency

  0.5–4 Hz

• Theta Wave Frequency

  4–7 Hz

• Primary Signal Source

  Postsynaptic potentials of pyramidal neurons

• Standard Electrode System

  International 10–20 system

Timeline

• Richard Caton performs the first known neurophysiologic recordings of electrical activity in animals. (Source: NCBI (Web Search))

  1875-01-01

• German psychiatrist Hans Berger pioneers the first EEG recordings in humans. (Source: NCBI (Web Search))

  1924-01-01

• Bryan Johnson discusses using Kernel's EEG technology to track brain activity during high-dose 5-MeO-DMT sessions. (Source: Document ee8d91a3-7a9e-4ab7-a219-26100b6be97d)

  2024-01-01

Electroencephalography

Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The bio signals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex. It is typically non-invasive, with the EEG electrodes placed along the scalp (commonly called "scalp EEG") using the International 10–20 system, or variations of it. Electrocorticography, involving surgical placement of electrodes, is sometimes called "intracranial EEG". EEG is widely used both as a clinical diagnostic tool, particularly in epilepsy, and as a research tool in neuroscience. Clinical interpretation of EEG recordings is performed by visual inspection of the tracing, which is the standard method. Quantitative EEG analysis may be used as an adjunct in specific clinical settings. Visual interpretation of EEG is subject to inter-rater and intra-rater variability. Voltage fluctuations measured by the EEG bio amplifier and electrodes allow the evaluation of normal brain activity. As the electrical activity monitored by EEG originates in neurons in the underlying brain tissue, the recordings made by the electrodes on the surface of the scalp vary in accordance with their orientation and distance to the source of the activity. Furthermore, the value recorded is distorted by intermediary tissues and bones, which act in a manner akin to resistors and capacitors in an electrical circuit. This means that not all neurons will contribute equally to an EEG signal, with an EEG predominately reflecting the activity of cortical neurons near the electrodes on the scalp. Deep structures within the brain further away from the electrodes will not contribute directly to an EEG; these include the base of the cortical gyrus, medial walls of the major lobes, hippocampus, thalamus, and brain stem. A healthy human EEG will show certain patterns of activity that correlate with how awake a person is. The range of frequencies one observes are between 1 and 30 Hz, and amplitudes will vary between 20 and 100 μV. The observed frequencies are subdivided into various groups: alpha (8–13 Hz), beta (13–30 Hz), delta (0.5–4 Hz), and theta (4–7 Hz). Alpha waves are observed when a person is in a state of relaxed wakefulness and are mostly prominent over the parietal and occipital sites. During intense mental activity, beta waves are more prominent in frontal areas as well as other regions. If a relaxed person is told to open their eyes, one observes alpha activity decreasing and an increase in beta activity. Theta and delta waves are not generally seen in wakefulness – if they are, it is a sign of brain dysfunction. EEG can detect abnormal electrical discharges such as sharp waves, spikes, or spike-and-wave complexes, as observable in people with epilepsy; thus, it is often used to inform medical diagnosis. EEG can detect the onset and spatio-temporal (location and time) evolution of seizures and the presence of status epilepticus. It is also used to help diagnose sleep disorders, depth of anesthesia, coma, encephalopathies, cerebral hypoxia after cardiac arrest, and brain death. EEG used to be a first-line method of diagnosis for tumors, stroke, and other focal brain disorders, but this use has decreased with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Despite its limited spatial resolution, EEG continues to be a valuable tool for research and diagnosis. It is one of the few mobile techniques available and offers millisecond-range temporal resolution, which is not possible with CT, PET, or MRI. Derivatives of the EEG technique include evoked potentials (EP), which involves averaging the EEG activity time-locked to the presentation of a stimulus of some sort (visual, somatosensory, or auditory). Event-related potentials (ERPs) refer to averaged EEG responses that are time-locked to more complex processing of stimuli; this technique is used in cognitive science, cognitive psychology, and psychophysiological research.

Web Search Results

• Electroencephalography - Wikipedia

  EEG can detect abnormal electrical discharges such as sharp waves, spikes, or spike-and-wave complexes, as observable in people with epilepsy; thus, it is often used to inform medical diagnosis. EEG can detect the onset and spatio-temporal (location and time) evolution of seizures and the presence of status epilepticus. It is also used to help diagnose sleep disorders, depth of anesthesia, coma, encephalopathies, cerebral hypoxia after cardiac arrest, and brain death. EEG used to be a first-line method of diagnosis for tumors, stroke, and other focal brain disorders, but this use has decreased with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Despite its limited spatial resolution, EEG continues to be a [...] EEG is the gold standard "Gold standard (test)") diagnostic procedure to confirm epilepsy. The sensitivity of a routine EEG to detect interictal epileptiform discharges at epilepsy centers has been reported to be in the range of 29–55%. Given the low to moderate sensitivity, a routine EEG (typically with a duration of 20–30 minutes) can be normal in people that have epilepsy. When an EEG shows interictal epileptiform discharges (e.g. sharp waves, spikes, spike-and-wave, etc.) it is confirmatory of epilepsy in nearly all cases (high specificity), however up to 3.5% of the general population may have epileptiform abnormalities in an EEG without ever having had a seizure (low false positive rate) or with a very low risk of developing epilepsy in the future. [...] One second of EEG signal The EEG is typically described in terms of (1) rhythmic activity and (2) transients. The rhythmic activity is divided into bands by frequency. To some degree, these frequency bands are a matter of nomenclature (i.e., any rhythmic activity between 8–12 Hz can be described as "alpha"), but these designations arose because rhythmic activity within a certain frequency range was noted to have a certain distribution over the scalp or a certain biological significance. Frequency bands are usually extracted using spectral methods (for instance Welch) as implemented for instance in freely available EEG software such as EEGLAB or the Neurophysiological Biomarker Toolbox. Computational processing of the EEG is often named quantitative electroencephalography (qEEG).

• Modern applications of EEG in neurological and cognitive research

  Electroencephalography (EEG) offers real-time insights into brain functionality by measuring the electrical signals generated in the brain, which is crucial for modern cognitive and neurological research. As a non-invasive method with high temporal resolution, EEG facilitates the understanding of complex cognitive and neurological processes. It has been employed to investigate various domains and disorders such as cognitive load, epilepsy, sleep patterns, Alzheimer’s disease, schizophrenia, and the neural correlations of attention and memory.

• Electroencephalogram (EEG) | Johns Hopkins Medicine

  Skip to Main Content Johns Hopkins Medicine An anatomical model of a brain sits atop test results. An anatomical model of a brain sits atop test results. An anatomical model of a brain sits atop test results. # Electroencephalogram (EEG) ## What is an EEG? An EEG is a test that detects abnormalities in your brain waves, or in the electrical activity of your brain. During an EEG, electrodes are pasted onto your scalp. These are small metal disks with thin wires. They detect tiny electrical charges that result from the activity of your brain cells. The charges are amplified and appear as a graph on a computer screen. Or the recording may be printed out on paper. Your healthcare provider then interprets the reading. [...] The test can also be used to diagnose other disorders that influence brain activity. These may include Alzheimer disease, certain psychoses, and a sleep disorder called narcolepsy. An EEG may also be used to determine the overall electrical activity of the brain. For example, it may be used to evaluate trauma, drug intoxication, or the extent of brain damage in a person who is in a coma. Depending on where the injury is, an EEG is one test of many to help decide brain death in critically ill patients. An EEG may also be used to monitor blood flow in the brain or neck's blood vessels during surgery. There may be other reasons for your provider to advise an EEG. ## What are the risks of an EEG? [...] During an EEG, your provider typically looks at about 100 pages, or computer screens, of activity. They pay special attention to the basic waveform. But your provider also looks at brief bursts of energy and responses to stimuli, such as flashing lights. You may also have tests called evoked potential studies. These studies measure electrical activity in your brain in response to stimulation of sight, sound, or touch. ANerv_20140331_v0_001 ## Why might I need an EEG? An EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG. People with lesions on their brain, which can result from tumors or stroke, may have very slow EEG waves. It depends on the size and the location of the lesion.

• Introduction - Electroencephalography (EEG): An Introductory ... - NCBI

  The first known neurophysiologic recordings of animals were performed by Richard Caton in 1875. The advent of recording the electrical activity of human beings took another half century to occur. Hans Berger, a German psychiatrist, pioneered the EEG in humans in 1924. The EEG is an electrophysiological technique for the recording of electrical activity arising from the human brain. Given its exquisite temporal sensitivity, the main utility of EEG is in the evaluation of dynamic cerebral functioning. EEG is particularly useful for evaluating patients with suspected seizures, epilepsy, and unusual spells. With certain exceptions, practically all patients with epilepsy will demonstrate characteristic EEG alterations during an epileptic seizure (ictal, or during-seizure, recordings). Most [...] The EEG is thought to be primarily generated by cortical pyramidal neurons in the cerebral cortex that are oriented perpendicularly to the brain's surface. The neural activity detectable by the EEG is the summation of the excitatory and inhibitory postsynaptic potentials of relatively large groups of neurons firing synchronously. Conventional scalp or cortical surface–recorded EEG is unable to register the momentary local field potential changes arising from neuronal action potentials. Please see Appendix 1 for further details on neurophysiologic principles underlying the EEG. [...] A typical EEG display graphs voltages on the vertical domain and time on the horizontal domain, providing a near real-time display of ongoing cerebral activity (Figure 1). With digital recording and review, the interpreter can change several aspects of the EEG display for convenience and intelligibility of the data. The interpreter is able to adjust the sensitivity (also known as [aka] “gain”) of the recording, in microvolts per millimeter, to either increase or reduce the display height of waveforms. One may also alter the amount of time displayed, which is sometimes referred to as an epoch and used to be known as “paper speed.” Shorter intervals can be viewed with a few seconds on a computer screen, a distinct advantage for viewing very brief EEG events such as epileptiform spikes.

• Electroencephalogram (EEG): What It Is, Procedure & Results

  Image content: This image is available to view online. View image online ( An EEG (electroencephalogram) measures the electrical activity in your brain. Healthcare providers often use this test to diagnose conditions like epilepsy. Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy Providers may use the term EEG to describe the test itself and what it shows. During this test, a technician places small, metal disks (electrodes) on your scalp. The electrodes connect to a machine that records the electrical signals your brain cells (neurons) use to communicate. Tracking these signals shows how well different parts of your brain are working. [...] Gray gradient Gray gradient Gray gradient Gray gradient Cleveland Clinic logo Search Search # Electroencephalogram (EEG) An EEG (electroencephalogram) is a test that tracks your brain’s electrical signals. It checks for epilepsy or other brain conditions. It’s painless, safe and can be done while you’re awake or asleep. Your provider will use the results to help guide a diagnosis and treatment. Advertisement Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy ## What Is an Electroencephalogram (EEG)? Person with scalp electrodes connected to an EEG recording brainwave signals from a brain Image content: This image is available to view online.

• Instance Of

  Q4167410