Instruct: Given a question, retrieve passages that can help answer the question.
Query: How are brain waves measured?
Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical activity of the brain. It is typically noninvasive, with the electrodes placed along the scalp, although invasive electrodes are sometimes used such as in electrocorticography. EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain.[1] In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a period of time,[1] as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus either on event-related potentials or on the spectral content of EEG. The former investigates potential fluctuations time locked to an event like stimulus onset or button press. The latter analyses the type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals in the frequency domain.
In a 2003 interview, Dale explained that he had “always been interested in using quantitative modeling methods and simulations to answer biological questions,” and that as a Harvard student he had been “interested in approaching connectionist neural networks from a more biological angle.” When he went to UCSD to continue his graduate work his interest “shifted to learning how to test models of how the brain works. Ideally you'd like to test your models not in anesthetized animals and brain slices, but by measuring brain activity in humans non-invasively. I wanted to study normal people doing normal tasks. That was what brought me to imaging. My goal was to see what kind of things we can measure non-invasively that can be quantitatively related to the models we want to build...I wanted to know what exactly we are measuring, how can you model it, and how can you relate the signal to what is going on in the brain physiologically...at a level that say you could measure invasively and that you could relate to parameters of quantitative models.” His thesis work at UCSD, he said, “was on the EEG and MEG forward and inverse problems, and how to use anatomical information to constrain the solutions. It is clear that if you only use EEG or MEG measures, the spatial precision is not good enough to make inferences at a scale that's most useful to neuroscience. That led us into trying to use information with higher spatial resolution to constrain or bias our estimations of the signal sources in the brain.”
Blast and ballistic pressure waves have physical similarities. Prior to wave reflection, they both are characterized by a steep wave front followed by a nearly exponential decay at close distances. They have similarities in how they cause neural effects in the brain. In tissue, both types of pressure waves have similar magnitudes, duration, and frequency characteristics. Both have been shown to cause damage in the hippocampus. It has been hypothesized that both reach the brain from the thoracic cavity via major blood vessels.
During World War II, Lilly researched the physiology of high-altitude flying and invented instruments for measuring gas pressure. After the war, he trained in psychoanalysis at the University of Pennsylvania, where he began researching the physical structures of the brain and consciousness. In 1951 he published a paper showing how he could display patterns of brain electrical activity on a cathode ray display screen using electrodes he devised specially for insertion into a living brain. Furthermore, Lilly's work on electrical stimulation of the nervous system gave rise to biphasic charge balanced electrical stimulation pulses (later known as "Lilly's wave" or "Lilly's pulses" ), now an established approach to design of safe electrical stimulation in neuroprosthetics. In the 1960s he sponsored research on Human–animal communication with a dolphin.
Electroencephalography (EEG) has been used in many studies as a primary method for evaluating the meditating brain. Electroencephalography uses electrical leads placed all over the scalp to measure the collective electrical activity of the cerebral cortex. Specifically, EEG measures the electric fields of large groups of neurons. EEG has the benefit of excellent temporal resolution and is able to measure aggregate activity of portions or the entire cortex down to the millisecond scale. Unlike other imaging based methods, EEG does not have good spatial resolution and is more appropriately used to evaluate the running spontaneous activity of the cortex. This spontaneous activity is classified into four main classifications based on the frequency of the activity, ranging from low frequency delta waves (< 4 Hz) commonly found during sleep to beta waves (13–30 Hz) associated with an awake and alert brain. In between these two extremes are theta waves (4–8 Hz) and alpha waves (8–12 Hz).
Nelly Kim is a lone Brain Powerd pilot whom Yu met when he and his Brain was damaged by the Baron Grand Cher. She gave Yu pieces of wisdom on how to listen and understand carefully of how his Brain feels. But in the end on the second attack made by the Baron Grand Cher she fell and disappeared in a storm gust as the two damaged Brains fused in a Chakra wave and became a hybrid Brain Powerd named Nelly Brain.
Gamma wave thalamocortical oscillation is prominent during REM sleep, similar to the awakened, active brain. Contrary to the conscious state, however, it appears that sensory input may be blocked or gated from interfering with the intrinsic activity of the brain during REM. Measures of bulk electrical signalling in the brain by MEG show no impact of auditory stimuli on the gamma wave patterns; measurements on conscious subjects show a distinct modulation due to the auditory input. In this way, the thalamocortical system acts to gate the brain from external stimuli during REM.
Cordance is a measure of regional brain activity. It is computed using quantitative electroencephalographic (QEEG) measures of brain wave patterns in an algorithm developed at the UCLA Laboratory of Brain, Behavior, and Pharmacology by Drs. Andrew Leuchter and Ian Cook.
As a young man, Walter was greatly influenced by the work of the Russian physiologist Ivan Pavlov. He visited the lab of Hans Berger, who invented the electroencephalograph, or EEG machine, for measuring electrical activity in the brain. Walter produced his own versions of Berger's machine with improved capabilities, which allowed it to detect a variety of brain wave types ranging from the high speed alpha waves to the slow delta waves observed during sleep.
Researchers work side-by-side with clinicians. Brain scientists at the Center use technologies to elucidate how brain networks can be strengthened and reconnected, including electroencephalography (EEG) to record the brain’s electrical rhythms during cognitive task performance, functional MRI (fMRI) scans to measure brain blood flow during cognitive tasks, an indicator of brain activity and brain morphometrics to measure size and shape differences of brain regions to millimeter accuracy. The Center houses specialists in various fields of neuroscience, and has produced publications from members of the BrainHealth Team. Research initiatives include:
VEP testing of acuity is somewhat similar to preferential looking in using a series of black and white stripes (sine wave gratings) or checkerboard patterns (which produce larger responses than stripes). Behavioral responses are not required and brain waves created by the presentation of the patterns are recorded instead. The patterns become finer and finer until the evoked brain wave just disappears, which is considered to be the endpoint measure of visual acuity. In adults and older, verbal children capable of paying attention and following instructions, the endpoint provided by the VEP corresponds very well to the psychophysical measure in the standard measurement (i.e. the perceptual endpoint determined by asking the subject when they can no longer see the pattern). There is an assumption that this correspondence also applies to much younger children and infants, though this does not necessarily have to be the case. Studies do show the evoked brain waves, as well as derived acuities, are very adult-like by one year of age.
Mori's theory was criticized as unwarranted research by established neuroscientists and brain specialists, because he used unreliable measures and misinterpreted the fluctuation of beta waves. One of his critics, Dennis Schutter, a neuroscientist specialising in the EEG signatures of different emotional states has stated, "My guess is that fatigue is the most likely cause of the absence of the beta waves and not the gaming per se."
Neurotechnology enables studying the brain and racial interactions, though this study can be difficult because these interactions can be hard to replicate. Face recognition tests are the most commonly used method in studying racial interactions. These tests consist of observing own-race and other-race faces, and studying the brain's response to the faces. There are three major neurological techniques used to measure the brain's response to these simulated racial interactions. Functional magnetic resonance imaging (fMRI) measures the brain activity through measuring the blood oxygen level in the brain. This test gives insight into which regions of the brain are active during a certain event. Event-related potentials (ERPs) measure the brain's activity through measuring electrical impulses by electrodes on the head. This test gives insight in rapid changes in the brain. Transcranial magnetic stimulation (TMS) measures the response of a region of the brain once activated through magnetism. This test gives insight into causality of occurrences and gives specific insight in what the brain regions are doing. Brain-damaged patients have also been used to study racial interactions, by studying how racial interactions are affected when specific brain regions are damaged. These studies give insight into how different brain regions are involved in racial interactions once certain regions have been damaged.
An implicit association test (IAC) is often used to measure the racial bias of people in studies by testing what objects, whether positive or negative, people associate with same-race or other-race faces.
Neurometrics is the science of measuring the underlying organization of the brain's electrical activity. Certain brainwave frequencies are associated with general psychological processes. EEGs are used to measure the brain waves.
Sound is measured based on the amplitude and frequency of a sound wave. Amplitude measures how forceful the wave is. The energy in a sound wave is measured in decibels (dB), the measure of loudness, or intensity of a sound; this measurement describes the amplitude of a sound wave. Decibels (dB) are expressed in a logarithmic scale. On the other hand, pitch describes the frequency of a sound and is measured in hertz (Hz). 
The majority of patented methods for noninvasive monitoring of ICP are based on an assumption that changes in ICP affect the physical dimensions and/or acoustic properties of the cranial vault or intracranial structures (dura, brain tissue, brain ventricles, and/or intracranial vessels). The common drawback of all these methods is that they measure only relative changes of ICP as referenced to a baseline measurement during which absolute ICP is known, i.e. the ultrasound readouts need to be calibrated on each subject against an invasive measurement. Ultrasound ‘time of the flight’ methods for non-invasive ICP monitoring have not been extensively validated and currently, the majority of them do not seem to be accurate enough for a routine clinical use. Their original formulations usually do not specify locations for the transducer's placement and do not address how the intentional or accidental use of different locations and/or angles of the transducers will affect the reliability of ICP estimates. It has also remained unexplored how the measurements are affected by the presence of intracranial pathological masses on the path of the ultrasound wave, or by brain masses shifts.
A classic and popular tool used to relate mental and neural activity is the electroencephalogram (EEG), a technique using amplified electrodes on a person's scalp to measure voltage changes in different parts of the brain. Hans Berger, the first researcher to use EEG on an unopened skull, quickly found that brains exhibit signature "brain waves": electric oscillations which correspond to different states of consciousness. Researchers subsequently refined statistical methods for synthesizing the electrode data, and identified unique brain wave patterns such as the delta wave observed during non-REM sleep.
The brain sensing headband measures the players brain waves with EEG technology.
1970s - Computers emerge as business tools, allowing researchers to conduct large-scale data manipulations. (Honomichl p. 175) Multiple studies prove DAR (Recall) scores do not predict sales. The measure, persuasion, also known as motivation, is validated as a predictor of sales. The measure known as “breakthrough” is re-examined by researchers who make a distinction between the attention-getting power of the creative execution (attention) and how well “branded” the ad is (brand linkage). Herbert Krugman seeks to measure non-verbal measures biologically by tracking brain wave activities as respondents watch commercials. (Krugman) Others experiment with galvanic skin response, voice pitch analysis, and eye-tracking.
Many studies on mindfulness meditation, assessed in a review by Cahn and Polich in 2006, have linked lower frequency alpha waves, as well as theta waves, to meditation. Much older studies report more specific findings, such as decreased alpha blocking and increased frontal lobe specific theta activity. Alpha blocking is a phenomenon where the active brain, normally presenting beta wave activity, cannot as easily switch to alpha wave activity often involved in memory recall. These findings would suggest that in a meditative state a person is more relaxed but maintains a sharp awareness. Two large, recent comprehensive review works, however, point to poor control and statistical analyses in these early studies and comment that it can only be said with confidence that increased alpha and theta wave activity exists.
Functional magnetic resonance imaging (fMRI) is another highly utilized methodology for studying state changes in meditating brains. fMRI detects subtle increases in blood flow to areas of the brain with higher metabolic activity. Thus these areas of increased metabolic activity indicate which regions of the brain are currently being used to process whatever stimuli presented. Counter to EEG, the advantage of fMRI is its spatial resolution, with the ability to produce detailed spatial maps of brain activity. It suffers, however, in temporal resolution and cannot measure progressive activity, like the EEG, with much detail.
Janov initiated from the outset small-scale research using questionnaires and measures of EEG, body temperature, blood pressure and pulse from his patients. A 1971 "Pittsburgh Press" article cited a University of California at Irvine study on primal therapy patients that showed a slowing of brain waves. Janov claimed that primal therapy reduced, in some patients, the frequency and the amplitude of Alpha waves, core body temperature (as much as three degrees) and blood pressure (as much as 30 percent). Two Brain Research Institute (UCLA) scientists confirmed that there were brain-wave changes in primal patients.
One class of solutions to the Boltzmann brain problem makes use of differing approaches to the measure problem in cosmology: in infinite multiverse theories, the ratio of normal observers to Boltzmann brains depends on how infinite limits are taken. Measures might be chosen to avoid appreciable fractions of Boltzmann brains. Unlike the single-universe case, one challenge in finding a global solution in eternal inflation is that all possible string landscapes must be summed over; in some measures, having even a small fraction of universes infested with Boltzmann brains causes the measure of the multiverse as a whole to be dominated by Boltzmann brains.
Sleep involves great changes in brain activity. Until the 1950s it was generally believed that the brain essentially shuts off during sleep, but this is now known to be far from true; activity continues, but patterns become very different. There are two types of sleep: "REM sleep" (with dreaming) and "NREM" (non-REM, usually without dreaming) sleep, which repeat in slightly varying patterns throughout a sleep episode. Three broad types of distinct brain activity patterns can be measured: REM, light NREM and deep NREM. During deep NREM sleep, also called slow wave sleep, activity in the cortex takes the form of large synchronized waves, whereas in the waking state it is noisy and desynchronized. Levels of the neurotransmitters norepinephrine and serotonin drop during slow wave sleep, and fall almost to zero during REM sleep; levels of acetylcholine show the reverse pattern.
To express matters differently (paraphrasing Steven Weinberg), the Schrödinger wave equation determines the wave function at any later time. If observers and their measuring apparatus are themselves described by a deterministic wave function, why can we not predict precise results for measurements, but only probabilities? As a general question: How can one establish a correspondence between quantum and classical reality?
Berger took a cue from Ukrainian physiologist Vladimir Pravdich-Neminsky, who used a string galvanometer to create a photograph of the electrical activity of a dog's brain. Using similar techniques, Berger confirmed the existence of electrical activity in the human brain. He first did this by presenting a stimulus to hospital patients with skull damage and measuring the electrical activity in their brains. Later he ceased the stimulus method and began measuring the natural rhythmic electrical cycles in the brain. The first natural rhythm he documented was what would become known as the alpha wave. Berger was very thorough and meticulous in his data-gathering, but despite his brilliance, he did not feel confident enough to publish his discoveries until at least five years after he had made them. In 1929, he published his first findings on alpha waves in the journal "Archiv für Psychiatrie". He was originally met with derision for his EEG technique and his subsequent alpha and beta wave discoveries. His technique and findings did not gain widespread acceptance in the psychological community until 1937, when he gained the approval of the famous physiologist Lord Adrian, who took a particular interest in alpha waves.