Brainwave entrainment

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Brainwave entrainment, also referred to as brainwave synchronization or neural entrainment, refers to the observation that brainwaves (large-scale electrical oscillations in the brain) will naturally synchronize to the rhythm of periodic external stimuli, such as flickering lights, [1] speech, [2] music, [3] or tactile stimuli.

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As different conscious states can be associated with different dominant brainwave frequencies, [4] it is hypothesized that brainwave entrainment might induce a desired state. Researchers have found, for instance, that acoustic entrainment of delta waves in slow wave sleep had the functional effect of improving memory in healthy subjects. [5]

Neural oscillation

Neural oscillations are rhythmic or repetitive electrochemical activity in the brain and central nervous system. [6] Such oscillations can be characterized by their frequency, amplitude and phase. Neural tissue can generate oscillatory activity driven by mechanisms within individual neurons, as well as by interactions between them. They may also adjust frequency to synchronize with the periodic vibration of external acoustic or visual stimuli. [7] [8]

The activity of neurons generate electric currents; and the synchronous action of neural ensembles in the cerebral cortex, comprising large numbers of neurons, produce macroscopic oscillations. These phenomena can be monitored and graphically documented by an electroencephalogram (EEG). The EEG representations of those oscillations are typically denoted by the term 'brainwaves' in common parlance. [9] [10]

The technique of recording neural electrical activity within the brain from electrochemical readings taken from the scalp originated with the experiments of Richard Caton in 1875, whose findings were developed into EEG by Hans Berger in the late 1920s.

Neural oscillation and cognitive functions

The functional role of neural oscillations is still not fully understood; [11] however they have been shown to correlate with emotional responses, motor control, and a number of cognitive functions including information transfer, perception, and memory. [12] [13] [14] Specifically, neural oscillations, in particular theta activity, are extensively linked to memory function, and coupling between theta and gamma activity is considered to be vital for memory functions, including episodic memory. [15] [16] [17]

Etymology

Entrainment is a concept first identified by the Dutch physicist Christiaan Huygens in 1665 who discovered the phenomenon during an experiment with pendulum clocks: He set them each in motion and found that when he returned the next day, the sway of their pendulums had all synchronized. [18]

Such entrainment occurs because small amounts of energy are transferred between the two systems when they are out of phase in such a way as to produce negative feedback. As they assume a more stable phase relationship, the amount of energy gradually reduces to zero, with systems of greater frequency slowing down, and the other speeding up. [19]

The cocept of entrainment was developed in complex systems theory. The theory explains the way that two or more independent, autonomous oscillators with differing rhythms or frequencies, when situated in proximity where they can interact for long enough, influence each other mutually, to a degree dependent on coupling force. They then adjust until both oscillate with the same frequency. Examples include the mechanical entrainment or cyclic synchronization of two electric clothes dryers placed in close proximity, and the biological entrainment evident in the synchronized illumination of fireflies. [20]

The term 'entrainment' has been used to describe a shared tendency of many physical and biological systems to synchronize their periodicity and rhythm through interaction. This tendency has been identified as specifically pertinent to the study of sound and music generally, and acoustic rhythms specifically. The most familiar examples of neuromotor entrainment to acoustic stimuli is observable in spontaneous foot or finger tapping to the rhythmic beat of a song.

Brainwaves, or neural oscillations, share the fundamental constituents with acoustic and optical waves, including frequency, amplitude and periodicity. Consequently, Huygens' discovery precipitated inquiry[ citation needed ] into whether or not the synchronous electrical activity of cortical neural ensembles might not only alter in response to external acoustic or optical stimuli but also entrain or synchronize their frequency to that of a specific stimulus. [21] [22] [23] [24]

Brainwave entrainment is a colloquialism for 'neural entrainment', [25] which is a term used to denote the way in which the aggregate frequency of oscillations produced by the synchronous electrical activity in ensembles of cortical neurons can adjust to synchronize with the periodic vibration of external stimuli, such as a sustained acoustic frequency perceived as pitch, a regularly repeating pattern of intermittent sounds, perceived as rhythm, or of a regularly rhythmically intermittent flashing light.

See also

Related Research Articles

A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 30 and 100 Hz, the 40 Hz point being of particular interest. Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation or neurostimulation. Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer's disease, epilepsy, and schizophrenia.

<span class="mw-page-title-main">K-complex</span>

A K-complex is a waveform that may be seen on an electroencephalogram (EEG). It occurs during stage 2 NREM sleep. It is the "largest event in healthy human EEG". They are more frequent in the first sleep cycles.

Beta waves, or beta rhythm, are neural oscillations (brainwaves) in the brain with a frequency range of between 12.5 and 30 Hz. Several different rhythms coexist, with some being inhibitory and others excitory in function.

Alpha waves, or the alpha rhythm, are neural oscillations in the frequency range of 8–12 Hz likely originating from the synchronous and coherent electrical activity of thalamic pacemaker cells in humans. Historically, they are also called "Berger's waves" after Hans Berger, who first described them when he invented the EEG in 1924.

<span class="mw-page-title-main">Thalamocortical radiations</span> Neural pathways between the thalamus and cerebral cortex

In neuroanatomy, thalamocortical radiations, also known as thalamocortical fibers, are the efferent fibers that project from the thalamus to distinct areas of the cerebral cortex. They form fiber bundles that emerge from the lateral surface of the thalamus.

<span class="mw-page-title-main">Neural oscillation</span> Brainwaves, repetitive patterns of neural activity in the central nervous system

Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by interactions between neurons. In individual neurons, oscillations can appear either as oscillations in membrane potential or as rhythmic patterns of action potentials, which then produce oscillatory activation of post-synaptic neurons. At the level of neural ensembles, synchronized activity of large numbers of neurons can give rise to macroscopic oscillations, which can be observed in an electroencephalogram. Oscillatory activity in groups of neurons generally arises from feedback connections between the neurons that result in the synchronization of their firing patterns. The interaction between neurons can give rise to oscillations at a different frequency than the firing frequency of individual neurons. A well-known example of macroscopic neural oscillations is alpha activity.

Theta waves generate the theta rhythm, a neural oscillation in the brain that underlies various aspects of cognition and behavior, including learning, memory, and spatial navigation in many animals. It can be recorded using various electrophysiological methods, such as electroencephalogram (EEG), recorded either from inside the brain or from electrodes attached to the scalp.

Thalamocortical dysrhythmia (TCD) is a theoretical framework in which neuroscientists try to explain the positive and negative symptoms induced by neuropsychiatric disorders like Parkinson's Disease, neurogenic pain, tinnitus, visual snow syndrome, schizophrenia, obsessive–compulsive disorder, depressive disorder and epilepsy. In TCD, normal thalamocortical resonance is disrupted by changes in the behaviour of neurons in the thalamus.
TCD can be treated with neurosurgical methods like the central lateral thalamotomy, which due to its invasiveness is only used on patients that have proven resistant to conventional therapies.

Bursting, or burst firing, is an extremely diverse general phenomenon of the activation patterns of neurons in the central nervous system and spinal cord where periods of rapid action potential spiking are followed by quiescent periods much longer than typical inter-spike intervals. Bursting is thought to be important in the operation of robust central pattern generators, the transmission of neural codes, and some neuropathologies such as epilepsy. The study of bursting both directly and in how it takes part in other neural phenomena has been very popular since the beginnings of cellular neuroscience and is closely tied to the fields of neural synchronization, neural coding, plasticity, and attention.

<span class="mw-page-title-main">Mu wave</span> Electrical activity in the part of the brain controlling voluntary movement

The sensorimotor mu rhythm, also known as mu wave, comb or wicket rhythms or arciform rhythms, are synchronized patterns of electrical activity involving large numbers of neurons, probably of the pyramidal type, in the part of the brain that controls voluntary movement. These patterns as measured by electroencephalography (EEG), magnetoencephalography (MEG), or electrocorticography (ECoG), repeat at a frequency of 7.5–12.5 Hz, and are most prominent when the body is physically at rest. Unlike the alpha wave, which occurs at a similar frequency over the resting visual cortex at the back of the scalp, the mu rhythm is found over the motor cortex, in a band approximately from ear to ear. People suppress mu rhythms when they perform motor actions or, with practice, when they visualize performing motor actions. This suppression is called desynchronization of the wave because EEG wave forms are caused by large numbers of neurons firing in synchrony. The mu rhythm is even suppressed when one observes another person performing a motor action or an abstract motion with biological characteristics. Researchers such as V. S. Ramachandran and colleagues have suggested that this is a sign that the mirror neuron system is involved in mu rhythm suppression, although others disagree.

Michael Hasselmo is an American neuroscientist and professor in the Department of Psychological and Brain Sciences at Boston University. He is the director of the Center for Systems Neuroscience and is editor-in-chief of Hippocampus (journal). Hasselmo studies oscillatory dynamics and neuromodulatory regulation in cortical mechanisms for memory guided behavior and spatial navigation using a combination of neurophysiological and behavioral experiments in conjunction with computational modeling. In addition to his peer-reviewed publications, Hasselmo wrote the book How We Remember: Brain Mechanisms of Episodic Memory.

<span class="mw-page-title-main">Subthreshold membrane potential oscillations</span>

Subthreshold membrane potential oscillations are membrane oscillations that do not directly trigger an action potential since they do not reach the necessary threshold for firing. However, they may facilitate sensory signal processing.

Recurrent thalamo-cortical resonance or Thalamocortical oscillation is an observed phenomenon of oscillatory neural activity between the thalamus and various cortical regions of the brain. It is proposed by Rodolfo Llinas and others as a theory for the integration of sensory information into the whole of perception in the brain. Thalamocortical oscillation is proposed to be a mechanism of synchronization between different cortical regions of the brain, a process known as temporal binding. This is possible through the existence of thalamocortical networks, groupings of thalamic and cortical cells that exhibit oscillatory properties.

The trisynaptic circuit or trisynaptic loop is a relay of synaptic transmission in the hippocampus. The trisynaptic circuit is a neural circuit in the hippocampus, which is made up of three major cell groups: granule cells in the dentate gyrus, pyramidal neurons in CA3, and pyramidal neurons in CA1. The hippocampal relay involves 3 main regions within the hippocampus which are classified according to their cell type and projection fibers. The first projection of the hippocampus occurs between the entorhinal cortex (EC) and the dentate gyrus (DG). The entorhinal cortex transmits its signals from the parahippocampal gyrus to the dentate gyrus via granule cell fibers known collectively as the perforant path. The dentate gyrus then synapses on pyramidal cells in CA3 via mossy cell fibers. CA3 then fires to CA1 via Schaffer collaterals which synapse in the subiculum and are carried out through the fornix. Collectively the dentate gyrus, CA1 and CA3 of the hippocampus compose the trisynaptic loop.

<span class="mw-page-title-main">Electroencephalography</span> Electrophysiological monitoring method to record electrical activity of the brain

Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals 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 using the International 10–20 system, or variations of it. Electrocorticography, involving surgical placement of electrodes, is sometimes called "intracranial EEG". Clinical interpretation of EEG recordings is most often performed by visual inspection of the tracing or quantitative EEG analysis.

Cornelius Hendrik "Case" Vanderwolf was a Canadian neuroscientist.

The neuroscience of rhythm refers to the various forms of rhythm generated by the central nervous system (CNS). Nerve cells, also known as neurons in the human brain are capable of firing in specific patterns which cause oscillations. The brain possesses many different types of oscillators with different periods. Oscillators are simultaneously outputting frequencies from .02 Hz to 600 Hz. It is now well known that a computer is capable of running thousands of processes with just one high-frequency clock. Humans have many different clocks as a result of evolution. Prior organisms had no need for a fast-responding oscillator. This multi-clock system permits quick response to constantly changing sensory input while still maintaining the autonomic processes that sustain life. This method modulates and controls a great deal of bodily functions.

Sharp waves and ripples (SWRs) are oscillatory patterns produced by extremely synchronised activity of neurons in the mammalian hippocampus and neighbouring regions which occur spontaneously in idle waking states or during NREM sleep. They can be observed with a variety of imaging methods, such as EEG. They are composed of large amplitude sharp waves in local field potential and produced by tens of thousands of neurons firing together within 30–100 ms window. They are some of the most synchronous oscillations patterns in the brain, making them susceptible to pathological patterns such as epilepsy.They have been extensively characterised and described by György Buzsáki and have been shown to be involved in memory consolidation in NREM sleep and the replay of memories acquired during wakefulness.

<span class="mw-page-title-main">Phase resetting in neurons</span> Behavior observed in neurons

Phase resetting in neurons is a behavior observed in different biological oscillators and plays a role in creating neural synchronization as well as different processes within the body. Phase resetting in neurons is when the dynamical behavior of an oscillation is shifted. This occurs when a stimulus perturbs the phase within an oscillatory cycle and a change in period occurs. The periods of these oscillations can vary depending on the biological system, with examples such as: (1) neural responses can change within a millisecond to quickly relay information; (2) In cardiac and respiratory changes that occur throughout the day, could be within seconds; (3) circadian rhythms may vary throughout a series of days; (4) rhythms such as hibernation may have periods that are measured in years. This activity pattern of neurons is a phenomenon seen in various neural circuits throughout the body and is seen in single neuron models and within clusters of neurons. Many of these models utilize phase response (resetting) curves where the oscillation of a neuron is perturbed and the effect the perturbation has on the phase cycle of a neuron is measured.

György Buzsáki is the Biggs Professor of Neuroscience at New York University School of Medicine.

References

  1. ↑ Notbohm, Annika; Kurths, Jürgen; Herrmann, Christoph S. (2016). "Modification of Brain Oscillations via Rhythmic Light Stimulation Provides Evidence for Entrainment but Not for Superposition of Event-Related Responses". Frontiers in Human Neuroscience. 10: 10. doi: 10.3389/fnhum.2016.00010 . ISSN   1662-5161. PMC   4737907 . PMID   26869898.
  2. ↑ Ding, Nai; Simon, Jonathan Z. (2014). "Cortical entrainment to continuous speech: functional roles and interpretations". Frontiers in Human Neuroscience. 8: 311. doi: 10.3389/fnhum.2014.00311 . ISSN   1662-5161. PMC   4036061 . PMID   24904354.
  3. ↑ Thaut, Michael H. (2015-01-01), Altenmüller, Eckart; Finger, Stanley; Boller, François (eds.), "Chapter 13 - The discovery of human auditory–motor entrainment and its role in the development of neurologic music therapy", Progress in Brain Research, Music, Neurology, and Neuroscience: Evolution, the Musical Brain, Medical Conditions, and Therapies, 217, Elsevier: 253–266, doi:10.1016/bs.pbr.2014.11.030, ISBN   9780444635518, PMID   25725919 , retrieved 2021-12-01
  4. ↑ Cantor, David S.; Evans, James R. (2013-10-18). Clinical Neurotherapy: Application of Techniques for Treatment. Academic Press. ISBN   9780123972910.
  5. ↑ Diep, Charmaine; Ftouni, Suzanne; Manousakis, Jessica E; Nicholas, Christian L; Drummond, Sean P A; Anderson, Clare (2019-11-06). "Acoustic slow wave sleep enhancement via a novel, automated device improves executive function in middle-aged men". Sleep. 43 (1). doi: 10.1093/sleep/zsz197 . ISSN   0161-8105. PMID   31691831.
  6. ↑ Buzsáki, György. "neural oscillation | Definition, Types, & Synchronization". Encyclopædia Britannica. Retrieved 7 January 2021.
  7. ↑ Niedermeyer E. and da Silva F.L., Electroencephalography: Basic Principles, Clinical Applications, and Related Fields. Lippincott Williams & Wilkins, 2004.
  8. ↑ "Capital District Neurofeedback". Saturday, 30 July 2022
  9. ↑ da Silva FL (1991). "Neural mechanisms underlying brain waves: from neural membranes to networks". Electroencephalography and Clinical Neurophysiology. 79 (2): 81–93. doi:10.1016/0013-4694(91)90044-5. PMID   1713832.
  10. ↑ Cooper R, Winter A, Crow H, Walter WG (1965). "Comparison of subcortical, cortical, and scalp activity using chronically indwelling electrodes in man". Electroencephalography and Clinical Neurophysiology. 18 (3): 217–230. doi:10.1016/0013-4694(65)90088-x. PMID   14255050.
  11. ↑ Llinas, R. R. (2014). "Intrinsic electrical properties of mammalian neurons and CNS function: a historical perspective". Front Cell Neurosci. 8: 320. doi: 10.3389/fncel.2014.00320 . PMC   4219458 . PMID   25408634.
  12. ↑ Fries P (2005). "A mechanism for cognitive dynamics: neuronal communication through neuronal coherence". Trends in Cognitive Sciences. 9 (10): 474–480. doi:10.1016/j.tics.2005.08.011. PMID   16150631. S2CID   6275292.
  13. ↑ Fell J, Axmacher N (2011). "The role of phase synchronization in memory processes". Nature Reviews Neuroscience. 12 (2): 105–118. doi:10.1038/nrn2979. PMID   21248789. S2CID   7422401.
  14. ↑ Schnitzler A, Gross J (2005). "Normal and pathological oscillatory communication in the brain". Nature Reviews Neuroscience. 6 (4): 285–296. doi:10.1038/nrn1650. PMID   15803160. S2CID   2749709.
  15. ↑ Buszaki G (2006). Rhythms of the brain. Oxford University Press.
  16. ↑ Nyhus, E; Curran T (June 2010). "Functional role of gamma and theta oscillations in episodic memory". Neuroscience and Biobehavioral Reviews. 34 (7): 1023–1035. doi:10.1016/j.neubiorev.2009.12.014. PMC   2856712 . PMID   20060015.
  17. ↑ Rutishauser U, Ross IB, Mamelak AN, Schuman EM (2010). "Human memory strength is predicted by theta-frequency phase-locking of single neurons" (PDF). Nature. 464 (7290): 903–907. Bibcode:2010Natur.464..903R. doi:10.1038/nature08860. PMID   20336071. S2CID   4417989.
  18. ↑ Pantaleone J (2002). "Synchronization of Metronomes". American Journal of Physics. 70 (10): 992–1000. Bibcode:2002AmJPh..70..992P. doi:10.1119/1.1501118.
  19. ↑ Bennett, M., Schatz, M. F., Rockwood, H., and Wiesenfeld, K., Huygens's clocks. Proceedings: Mathematics, Physical and Engineering Sciences, 2002, pp563-579.
  20. ↑ Néda Z, Ravasz E, Brechet Y, Vicsek T, Barabsi AL (2000). "Self-organizing process: The sound of many hands clapping". Nature. 403 (6772): 849–850. arXiv: cond-mat/0003001 . Bibcode:2000Natur.403..849N. doi:10.1038/35002660. PMID   10706271. S2CID   4354385.
  21. ↑ Will, U., and Berg, E., "Brainwave synchronization and entrainment to periodic stimuli" Neuroscience Letters, Vol. 424, 2007, pp 55–60.
  22. ↑ Cade, G. M. and Coxhead, F., The awakened mind, biofeedback and the development of higher states of awareness. New York, NY: Delacorte Press, 1979.
  23. ↑ Neher, A., "Auditory driving observed with scalp electrodes in normal subjects. Electroencephalography and Clinical Neurophysiology, Vol. 13, 1961, pp 449–451.
  24. ↑ Zakharova, N. N., and Avdeev, V. M., "Functional changes in the central nervous system during music perception. Zhurnal vysshei nervnoi deiatelnosti imeni IP Pavlova Vol. 32, No. 5, 1981, pp 915-924.
  25. ↑ Obleser, J., Kayser, C., "Neural Entrainment and Attentional Selection in the Listening Brain, Trends in Cognitive Sciences, Vol. 23, No. 11, 913-926

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