Associated tasks & behaviors: high-level information processing, "binding"
Physiological correlates: associated with information-rich task processing
Effects of Training: not known
Gamma is measured between 30 and 44 (Hz) and is the only frequency group found in every part of the brain. When the brain needs to simultaneously process information from different areas, its hypothesized that the 40Hz activity consolidates the required areas for simultaneous processing. A good memory is associated with well-regulated and efficient 40Hz activity, whereas a 40Hz deficiency creates learning disabilities." - NeuroHealth (2004)
"MIT neuroscientists found that neurons in the prefrontal cortex — the brain's planning center — fire in unison and send signals to the visual cortex to do the same, generating high-frequency waves that oscillate between these distant brain regions like a vibrating spring. These waves, also known as gamma oscillations, have long been associated with cognitive states such as attention, learning and consciousness. "We are especially interested in gamma oscillations in the prefrontal cortex because it provides top-down influences over other parts of the brain," explains senior author Robert Desimone, director of the McGovern Institute for Brain Research and the Doris and Don Berkey Professor of Neuroscience at MIT. "We know that the prefrontal cortex is affected in people with schizophrenia, ADHD and many other brain disorders, and that gamma oscillations are also altered in these conditions. Our results suggest that altered neural synchrony in the prefrontal cortex could disrupt communication between this region and other areas of the brain, leading to altered perceptions, thoughts, and emotions."" - MIT (May 2009)
Gamma brainwaves are very important
"Gamma waves are fast, high-frequency, rhythmic brain responses that have been shown to spike when higher cognitive processes are engaged. Research in adults and animals suggests that lower levels of gamma power might hinder the brain’s ability to efficiently package information into coherent images, thoughts and memories." - Science Daily (Oct 2008)
"Analyzing the children’s EEGs (electroencephalograms), Benasich and her research team found that those with higher language and cognitive abilities had correspondingly higher gamma power than those with poorer language and cognitive scores. Similarly, children with better attention and inhibitory control, the ability to moderate or refrain from behavior when instructed, also had higher gamma power." - Science Daily (Oct 2008) and Scientific Blogging (Oct 2008) and Science Central ( Oct 2008) and Rutgers University ( Oct 2008)
Gamma brainwaves and Involuntary Attention
"Gamma-band response was linked to voluntary shifts of attention, but not to the involuntary capture of attention. The presence of increased gamma responses for the voluntary allocation of attention, and its absence in cases of involuntary capture suggests that the neural mechanisms governing these two types of attention are different." - Journal of Neurscience (Oct 2007)
"Specifically, we investigated changes in induced alpha, beta, and gamma activity in 6-month-old infants during repeated presentations of either a face or an object, and examined whether these changes predicted behavioral responses to novelty at test. We found that induced gamma activity over occipital scalp regions decreased with stimulus repetition in the face condition but not in the toy condition, and that greater decreases in the gamma band were associated with enhanced orienting to a novel face at test." - MIT Press Journals (Dec 2008)
"We investigated whether evoked and induced 40?Hz activity differentiate automatic, bottom-up aspects of attention from voluntary, top-down related attentional demands. An auditory novelty-oddball task was applied to 14 healthy subjects. As predicted, more evoked gamma was found for the target condition than in the two task-irrelevant conditions. Since gamma band activity was not enhanced for novel stimuli, the evoked gamma response cannot be explained with a simple concept of stimulus arousal. Neither induced gamma nor the degree of 40?Hz phase-locking were different between the experimental conditions. Taken together, our data emphasize the role of evoked gamma band activity for top-down attentional processing." - Neuro Report (April 2003)
Gamma Brainwaves and Working Memory
"Working memory is the ability to actively hold information in the mind. Recent results demonstrate that working memory is organized by oscillatory processes in the theta and gamma frequency range." - Current Biology (June 2010)
"Studies of working memory load effects on human EEG power have indicated divergent effects in different frequency bands. Although gamma power typically increases with load, the load dependency of the lower frequency theta and alpha bands is uncertain." - Cerebral Cortex (2008)
"Maintenance of an increasing number of items elicited an incrementally negative shift of the DC potential and an increase in MTL gamma-band activity." - Journal of Neuroscience (July 2007)
"We analyzed intracranial recordings from two epileptic patients as they performed a working memory task. Spectral analyses revealed that, in both patients, gamma (30–60 Hz) oscillations increased approximately linearly with memory load, tracking closely with memory load over the course of the trial. This constitutes the first evidence that gamma oscillations, widely implicated in perceptual processes, support the maintenance of multiple items in working memory." - Cerebral Cortex (2003)
Gamma Brainwaves to Treat Alzheimer's
"The accumulation of amyloid-beta proteins is linked to the development of Alzheimer's disease. The disease is triggered by an imbalance in two different amyloid proteins—which form a plaque found in the brains of Alzheimer's patients. A reduction in the relative level of healthy amyloid-beta 40 compared to 42 is linked to Alzheimer’s. Dr. Inna Slutsky of Tel Aviv University's Sackler Faculty of Medicine and colleagues have uncovered two main features of the brain circuits that impact this crucial balance."
"The researchers found that spikes in the patterns of electrical pulses in the form of high-frequency bursts combined with the filtering properties of synapses are crucial to the regulation of the amyloid-beta 40/42 ratio. Synapses that transfer information in spike bursts improve the amyloid-beta 40/42 ratio. This research represents a major advance in understanding how brain circuits regulate the composition of amyloid-beta proteins."
"According to Dr. Slutsky, different kinds of environmental changes—as well as sensory and emotional experience—can modify the properties of synapses and change the spiking patterns in the brain." - Psychology Today (April 2013)
Gamma Brainwaves and Consciousness
"The suggested mechanism is that gamma waves relate to neural consciousness via the mechanism for conscious attention" - Wikipedia
"Thus the claim is that when all these neuronal clusters oscillate together during these transient periods of synchronized firing, they help bring up memories and associations from the visual precept to other notions. This brings a distributed matrix of cognitive processes together to generate a coherent, concerted cognitive act, such as perception. This has led to theories that gamma waves are associated with solving the binding problem." - Wikipedia
Gamma Brainwaves and Inspiration
"Behold the proverbial Aha! Moment—a key phenomenon that emerges in a range of situations, from offering a solution to a problem or a new interpretation of a situation to more simple feats such as understanding a joke or solving a crossword puzzle... In the volunteers that experienced insight, Kounios and Beeman found a distinctive spark of high gamma activity that would spike one-third of a second before volunteers consciously arrived at an answer." - Brain World Magazine (June 2012) and The Wall Street Journal (June 2009)
Gamma Brainwaves and Memory
"Thus, we set out to test whether access to LTM [Long Term Memory] modulates human gamma responses. We investigated whether simple visual stimuli evoke more gamma activity when subjects already have a memory representation of the presented objects as compared to when they perceive novel visual stimuli which do not match LTM. Indeed, stimuli for which subjects already had a representation in their LTM evoked significantly larger gamma responses." - Biomed Central (April 2004)
"Lang and her colleagues have also investigated whether formal features affect people's memory of what they have seen. In one of their studies, participants watched a program and then filled out a score sheet. Increasing the frequency of edits--defined here as a change from one camera angle to another in the same visual scene--improved memory recognition, presumably because it focused attention on the screen. Increasing the frequency of cuts--changes to a new visual scene--had a similar effect but only up to a point. If the number of cuts exceeded 10 in two minutes, recognition dropped off sharply. " - Scientific American (Feb 2002)
Gamma Brainwaves and Real Memories
"While patients performed the memory game, scientists observed electrical activity in their brains to determine whether specific brain waves were associated with successfully storing and retrieving memories. Researchers found that a fast brain wave, known as the gamma rhythm, increased when participants studied a word that they would later recall. The same gamma waves, whose voltage rises and fall between 50 and 100 times per second, also increased in the half-second prior to participants correctly recalling an item." - Science Daily (Oct 2007)
Gamma Brainwaves and Recognition
"Neural mechanisms of object recognition seem to rely on activity of distributed neural assemblies coordinated by synchronous firing in the gamma-band range (>20 Hz). In the present electroencephalogram (EEG) study, we investigated induced gamma band activity during the naming of line drawings of upright objects and objects rotated in the image plane. Such plane-rotation paradigms elicit view-dependent processing, leading to delays in recognition of disoriented objects. Our behavioral results showed reaction time delays for rotated, as opposed to upright, images. These delays were accompanied by delays in the peak latency of induced gamma band responses (GBRs), in the absence of any effects on other measures of EEG activity. The latency of the induced GBRs has thus, for the first time, been selectively modulated by an experimental manipulation that delayed recognition. This finding indicates that induced GBRs have a genuine role as neural markers of late representational processes during object recognition. In concordance with the view that object recognition is achieved through dynamic learning processes, we propose that induced gamma band activity could be one of the possible cortical markers of such dynamic object coding." - Journal of Cognitive Neuroscience (June 2007)
Gamma Brainwaves and ADHD
"Children with AD/HD had elevated levels of absolute delta and theta power, and decreased levels of absolute beta and gamma power, compared to controls. With relative power measures, children with AD/HD showed enhanced delta and theta activity, with reduced alpha, beta and gamma activity. Inattention scores on the Conners’ Parent Rating Scale were negatively correlated with absolute gamma." - Science Direct (April 2010)
Gamma Brainwaves and Schizophrenia
"Media Lab Professor Edward S. Boyden is developing technology to assess the role of coordinated neural activity in cognitive deficits in schizophrenia. The technology will be used to determine whether gamma-synchronized neural activity is necessary for proper behavioral function, and to determine if amplified oscillations can remedy disordered perceptual and cognitive processing typically found in individuals with schizophrenia." - MIT News (July 2008) see also MIT News (Jan 2009)
Gamma Brainwaves and Autism
""What we've observed is that starting as young as 6 months, maybe even younger, infants who have a high risk for developing autism show dramatic reductions in gamma activity," Nelson says." - NPR (June 2011)
"Gamma waves are also known to help establish the proper balance of excitation and inhibition in the brain, disruptions in which have been linked to autism." - SFARI (May 2009)
More on Gamma Brainwaves
""Enhancing Nav1.1 activity, and consequently improving PV cell function, may help in the treatment of Alzheimer's disease and other neurological disorders associated with gamma-wave alterations and cognitive impairments such as epilepsy, autism and schizophrenia," said Dr. Palop, who is also an assistant professor of neurology at the University of California, San Francisco, with which Gladstone is affiliated. "These findings may allow us to develop therapies to help patients with these devastating diseases." " - Medical News Today (April 2012)
"In the first few runs, while the rats were still learning the maze, the researchers saw bursts of ventral striatum activity in the gamma frequency range shortly before the rats finished the maze... When the rats began to catch on to how to earn the reward, the gamma activity faded away and was replaced with short bursts of activity in the beta band, a lower frequency, just after they finished the maze." - MIT News (Sept 2011)
"MIT neuroscientists found that neurons in the prefrontal cortex — the brain's planning center — fire in unison and send signals to the visual cortex to do the same, generating high-frequency waves that oscillate between these distant brain regions like a vibrating spring. These waves, also known as gamma oscillations, have long been associated with cognitive states like attention, learning, and consciousness." - Science Daily (June 2009)
"These waves, also known as gamma oscillations, have long been associated with cognitive states such as attention, learning and consciousness." - MIT News (May 2009)
"Scientists have studied high-frequency brain waves, known as gamma oscillations, for more than 50 years, believing them crucial to consciousness, attention, learning and memory.
Now, for the first time, MIT researchers and colleagues have found a way to induce these waves by shining laser light directly onto the brains of mice." - The Medical News (April 2009) and MIT News (April 2009)
""What we found is that if you crank the parvalbumin neurons down, you see fewer of these 40-Hertz oscillations. If you crank them up you see more of these gamma oscillations," Deisseroth said. "That's the first real proof that these neurons are indeed involved in generating these gamma brain waves." - Science Daily (April 2009) and Stanford (April 2009) and Regenerative Medicine (April 2009)
"The patterns of these brain waves allowed the investigators to obtain a thorough description of how attention altered neural function." - Science Daily (Dec 2006)
"Researchers at the University of Wisconsin-Madison have found that during meditation, Zen Buddhist monks show an extraordinary synchronization of brain waves known as gamma synchrony--a pattern increasingly associated with robust brain function and the synthesis of activity that we call the mind." - Scientific American (March 2005)
"Those transformed states have traditionally been understood in transcendent terms, as something outside the world of physical measurement and objective evaluation. But over the past few years, researchers at the University of Wisconsin working with Tibetan monks have been able to translate those mental experiences into the scientific language of high-frequency gamma waves and brain synchrony, or coordination. And they have pinpointed the left prefrontal cortex, an area just behind the left forehead, as the place where brain activity associated with meditation is especially intense. " - The Washington Post (Jan 2005)
"Functional imaging of human cortex implicates a diverse network of brain regions supporting working memory — the capacity to hold and manipulate information for short periods of time. Although we are beginning to map out the brain networks supporting working memory, little is known about its physiological basis. We analyzed intracranial recordings from two epileptic patients as they performed a working memory task. Spectral analyses revealed that, in both patients, gamma (30–60 Hz) oscillations increased approximately linearly with memory load, tracking closely with memory load over the course of the trial. This constitutes the first evidence that gamma oscillations, widely implicated in perceptual processes, support the maintenance of multiple items in working memory." - Cerebral Cortex (2003)
