Theta waves can be considered a marker of emotional regulation


Without realizing it, we all rely on emotional regulation many times a day. It’s the process by which we mitigate the effect of disturbing stimuli in order to stay focused, improve our well-being and respond to demands from our environment.

Emotional regulation plays a key role in many mental illnesses and their treatment, including anxiety, mood disorders and borderline personality disorder.

Now Inès Zouaoui, a master’s student in psychology supervised by Professor Marc Lavoie at the Research Center of the Montreal Mental Health University Institute, has demonstrated that emotional regulation is associated with the action of theta waves in a specific part of the brain, the frontal cortex. Zouaoui is set to start her Ph.D. in biomedical science, psychiatry option, at UdeM this fall.

A brain wave specific to emotional regulation

Building on the results of a 2013 study that showed theta waves are generated during emotional regulation, the Montreal research team gave 24 subjects a cognitive reappraisal exercise.

“We used cognitive reappraisal, which basically involves re-interpreting the meaning of a situation, to carry out an experimental study of emotional regulation,” explained Zouaoui. “Our goal was to decipher the electrocortical mechanisms that accompany this complex process.”

They attached electrodes to the scalps of the 10 men and 14 women to record the electrical activity in their brains in response to upsetting images, such as a man armed with a knife or a threatening dog.

While their brain activity was being continuously measured and recorded using electroencephalography, the subjects were instructed to either increase, decrease or maintain their feelings of aversion, depending on what group they were assigned to. This step also involved cognitive reappraisal. After a few seconds, the image disappeared and the emotional regulation phase ended.

“We performed more detailed analyses of the encephalograms than what was done in the previous study to measure the frequencies of the brain waves generated during cognitive reappraisal and found only theta waves, which oscillate between 4 and 8 Hz,” Zouaoui reported.

“So theta waves can be considered a marker of emotional regulation.

“What’s new about our study is that by comparing the emotional induction and emotional regulation phases, we were able to show that theta waves are specific to the regulation phase,” said Zouaoui.

“We also looked for alpha waves, which are in the 8 to 13 Hz range, to see if theta waves are specific to emotional regulation and found that alpha waves are not sensitive to either emotional induction or emotional regulation.”

The use of electrodes also enabled the research team to pinpoint the precise region of the brain responsible for generating the theta waves: the frontal regions involved in cognitive control.

New treatment options

Zouaoui’s goal wasn’t just to build on a previous study and add to the scientific literature; she hopes her experiment can one day be used to support clinical practice.

“Since theta waves can be a marker of successful emotional regulation, this could lead to new treatment options for people whose emotional regulation process is perturbed, which is the case in severe anxiety and schizophrenia, for example.”

Brain waves consist of rhythmic patterns of neuronal activity or synchronized electrochemical pulses from groups of neurons in the central nervous system (CNS)1. There are several well-established brainwave range patterns: gamma (30-70 Hz), beta (13-30 Hz), alpha (8-13 Hz), theta (4-8 Hz), and delta (1-4 Hz)2. Each one of these frequency bands has been correlated with different states of consciousness, such as awake, relaxed, rapid eye movement (REM) sleep, as well as non-REM sleep stages3.

According to Gruzelier4, prolonged audio stimuli in repetitive and synchronized manner may induce changes in brain waves patterns and, consequently, may modulate neurophysiological and behavioral responses. More specifically, repetitive external or environmental stimuli may temporarily affect the predominance of specific brain wave frequencies, a phenomenon namely brainwave entrainment (BWE)5-7. Therefore, BWE can be defined as rhythmic synchronization of brainwave oscillation with an external repetitive stimulus.

BWE is a recurrent phenomenon in nature and biologically present in living beings8. The principle of entrainment or harmonization was discovered around 1665, by the Dutch scientist Christian Huygens9. The synchronization obtained through the entrainment principle is the result of the harmonization principle, a physical phenomenon that occurs systematically in nature, and that is dependent on environmental stimuli, for example, visual, auditory, or tactile.

These stimuli may be used to elicit synchronized brainwave patterns to match that of different mental states and/or levels of consciousness, as seen with data acquisition techniques, such as the electroencephalography (EEG). In this context, Oster10 stated the possibility to improve, amplify or modulate brain wave patterns to conditioned events in the cerebral cortex 3,11. The proposed therapeutic benefits have a wide scope, including the improvement of cerebral blood flow, neuroplasticity stimulation, and neurophysiological compensations between the cerebral hemispheres 3.

In this review, we focused on the most common forms of auditory BWE, that is, binaural beats and isochronic tones. Acoustic waves are characterized in Hertz (number of cycles per second). The audible sound spectrum for humans comprises frequencies between 20 Hz and 20,000 Hz, regardless of its complexity, and as long as it has an amplitude greater than 0 dB (decibel)12,13.

Isochronic tones consist of distinct and repetitive regular beats of a single tone. The number of peaks per second in the signal amplitude is the isochronic frequency heard at regular and standardized time intervals. On the other hand, binaural beats represent the auditory experience that occurs when two sounds of close frequencies are presented separately to each ear with headphones or stereo speakers.

The brain integrates the two signals, producing a third “phantom sound” representing the difference between the two auditory stimuli. For example, if a frequency of 114 Hz is presented to the right ear, and another of 124 Hz to left ear, a binaural beat of 10 Hz is created by the brain as a result of these stimuli. In this case, brain waves tend to match the binaural beat frequency, in this example 10 Hz, which corresponds to alpha brainwave pattern. Binaural beats are created in the superior olivary nucleus of the brain stem, the local of contralateral integration of auditory input 14 (Fig. 1).

Figure 1 Binaural beats generated by the brain. 

The beat is neurologically transported to the reticular formation, which uses neurotransmitters to trigger changes in brain wave activity10 that synchronizes with that of the stimulus generated. The mental features associated with each brain wave pattern can be elicited based on the scientific principle of harmonization, also known as “brain wave entrainment.”

Most of studies with binaural beats and isochronic tones provides positive outcomes, indicating that audio brain entrainment may yield different benefits, both physically and mentally 15,16. More specifically, brain entrainment can be applied to induce mental states and as adjunctive treatment to several brain disorders in a safe and non-invasive manner, such as for the treatment of depression and anxiety disorders17.

For instance, it was demonstrated that a group of individuals exposed to 6 Hz sounds for 10 min presented a significant increase on theta wave (4-8 Hz) cortical activity in comparison to control group that did not receive the stimulus. These findings indicate a facilitatory effect on induction of a meditative state and altered states of consciousness18. In this context, the aim of this study was to review the scientific evidence on the therapeutic use of binaural beats and isochronic tones for the modulation of brain wave patterns and mood states.

Main findings of the studies addressing the effects of brain waves on mental states

In this section is presented a description of the different brainwaves, their effects, and the discussion of the main findings obtained in the studies reviewed here. The study performed by Washington and collaborators21 indicated that each brain wave frequency produces particular neurophysiological and cognitive effects, been associated with a specific state of consciousness.

Delta waves (< 4 Hertz): the slowest waves are associated with the deepest state of sleep and unconscious. These waves represent the ideal for sleep, physical and mental recovery, and deep meditation. Delta waves lead to a state of mental happiness and empathy where the person feels more connected with her/himself. This state improves intuition and memory. Delta waves are associated with the release of growth hormone 22, which is beneficial for cell regeneration, as well as the production of endogenous opioids 23. None of the selected studies review here used delta waves.

Theta waves (4-8 Hz): this frequency pattern is related to the processes of creativity, enhanced intuition, more intense emotional connections that elevate sensitivity, and a sense of tranquility and reduced anxiety. Theta waves also contribute to the improvement of problem-solving skills and retention of much larger amounts of information in shorter period of time. This pattern is associated with decreased levels of serum cortisol and with the modulation of serotonin and melatonin. Theta waves generate a relaxed state of consciousness24,25.

Eight of the studies reviewed here were conducted with Theta waves, with binaural beats as well as isochronic tones interventions. Major targets were cognitive and/or pathological states. Increased long-term memory performance was observed in patients with epilepsy who underwent 6-min 5 Hz brain entrainment sessions, once a week for 6 weeks with binaural and isochronic tones26. On the other hand, in non-epileptic adult subjects, 15-min 5 Hz brain entrainment sessions did not induce significant effects


Visuospatial working memory and cortical connectivity were not altered following a single intervention of 5 min with 5 Hz therapy28. Another study using binaural beats also describes absence of significant effects in the working memory of healthy young adults29. Interestingly, 20-min 6 Hz binaural beat entrainment twice a week for 14 days effectively reduced the perception of pain severity16.

In addition, in patients with temporal lobe epilepsy who underwent brain implants with EEG signal control, acute therapy of temporolateral (5 Hz for 5 min) increased memory acuity with EEG synchronization17. Moreover, in young adult’s post-physical training, binaural beat entrainment (4-7 Hz for 20 min) increased parasympathetic activation and self-reported relaxation30. Finally, a single intervention with isochronic tones at 6, 10 and 40 Hz during 5 min reduced anxiety and improved well-being reports of healthy individuals31.

Alpha waves (8-13 Hz): this frequency pattern is related to mental relaxation32, visualization, and creative processes; therapeutically uses include memory optimization, and modulation of pain perception threshold. The use of this wave pattern in the elderly population has been shown an excellent therapeutic potential to treat memory disorders33.

Alpha waves were used with a therapeutic and/or neurocognitive focus in six studies reviewed here. Vernon et al.34 reported that 10 Hz alpha pattern for 1 or 5 min did not elicit significant EEG alteration. However, isochronic stimulation with 7 Hz for 9 min with 3 min intervals induced temporal and parietal lobe activation with the potential to alter brain networks in adult’s healthy young individuals35. Alpha binaural beats for 3 min in healthy young adults did not affect attentional blink (AB) control with the EBR method (predictor of mood states associated with dopamine levels)36. Moreover, patients with temporal lobe epilepsy who underwent brain implants, the acute exposure to 10 Hz isochronic tones for 5 min increased significantly medio temporal synchronization17,30.

Beta waves (13-39 Hz): this frequency pattern is related to attention, focus, concentration, and cognition. Beta BWE was shown to be effective in improving fatigue and some symptoms of attention deficit hyperactive disorder (ADHD), including learning and attention deficits. Additional studies showed improvement in visual acuity, coordination, potential for the dyslexia treatment and low of concentration, as well as, to promote IQ gain in the range of 8-10 points37. Beta wave entrainment influenced self-confidence and socialization and makes people more optimistic and energetic38-41. Finally, it helps learning as well as sports-related abilities3,42.

Five independent studies reviewed here used beta waves. Beauchene et al.28 demonstrated that 15 Hz beta pattern for 5 min increased short-term visuospatial working memory and cortical connectivity in healthy young subjects. A single 15-min session of 20 Hz significantly increased long-term memory, improving the codification of new information without previous memories24. Interestingly, Vernon et al.34 demonstrated that two daily sessions (14 Hz, during 10 min) increased motor and non-motor symptoms in Parkinson’s disease (PD) patients. In addition, Gálvez et al.43 showed a decrease of functional connectivity and optimization of working memory, with no changes in gait or anxiety levels in PD patients in comparison to control group. Kennel et al.44 submitted a group of children and adolescents with diagnosis of ADHD to brain entrainment sessions (duration of 10 min, 3 days per week for 3 weeks). Results were not totally conclusive, although parents reported improvement in the performance of homework tasks after the interventions.

Gamma Waves (> 40 Hz): this frequency pattern is involved in blinking and processing of information from all parts of the brain. High gamma wave activity in the brain is associated with intelligence, compassion, self-control, and feelings of happiness45-48. In addition, gamma brainwaves have been associated with improved memory and a greater ability of reality perception49,50. Gamma brainwave activity has been shown to be increased in monks during meditation51.

Six studies were conducted with gamma BWE. It was demonstrated that 40 Hz gamma stimulation for 20 min improved working memory performance and mnemonic function in healthy subjects52. AB control, using the EBR method (predictor of mood states associated with dopamine levels), was significantly affected by 3-min binaural gamma stimulation in healthy young adults, before and during a global-local task36.

These benefits were observed only in individuals with low rates of spontaneous blinking, which indicates low levels of dopamine in the striatum. Colzato et al.53 reported that 3-min 40 Hz binaural beats stimulation improved focus and attention in healthy young adults.

Moreover, a study using 10-min 40 Hz stimulation in healthy adults54 demonstrated that BWE acts by modeling specific brain oscillations, in cognitive processes sustained in the gamma wave frequency range, such as mental processes related to intelligence, self-control, and well-being. In epileptic patients subjected to brain implants, acute isochronic tones and binaural beats exposure, in the range of 40-80 Hz for 5 min significantly decreased synchronization in medio-temporal sites, demonstrating their potential as a non-invasive therapy for modulating intracranial flow in synchronization of the EEG signals17.

A single intervention with isochronic tones 6, 10, and 40 Hz over 5 min reduced anxiety and, consequently, increased the subjects’ well-being, however, without marked effects on cognition55.

As illustrated in figure 3, in 82.35% of the reviewed studies, monaural, and/or binaural audio stimulation were more effective in comparison to control group. As previously mentioned, binaural beats were used as therapeutic modality in 15 studies (88.25%), and isochronic tones were only used in two studies (11.76%).


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Source: University of Montreal


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