EEG Session 26: Theta Audiovisual Entrainment

This page contains the data and analysis of a brain wave recording session I did using a Muse Gen 1 EEG Headband.

Session Characteristics

  • 10/11/2023, 00:29
  • During this session, I was testing aThetaAudiovisual Brainwave Entrainment track I created.
  • I was seated in the dark, looking directly at the flashing screen with my eyes open.
  • I felt mostly relaxed, and sometimes I even got lost in thought, even though the audiovisual experience itself can be described as being somewhat intense.

All Sensors

  • BetaandGammastarted in a descending trajectory, staying low, then quickly ascending and starting to descend again. This is a pattern I haven’t seen before. Other frequencies didn’t behave like this.
  • This is the first, out of all the“ThetaSessions” (starting from Session 19), that does not haveThetaas the second dominant force and instead hasBeta.
  • It’s hard to find sessions with such highBetadominance in the All Sensors section, especially if I’m not being engaged with mental effort (which I wasn’t at all during this session). Therefore, I am strongly inclined to attribute this behavior to the entrainment track, even if it’s not focused onBetaentrainment.
  • Let’s see what else we can find.

All Sensors (Gamma and Beta Isolated)

  • Taking a closer look atBetaandGamma, we can see more clearly the gradual decrease in energy, then a sudden boost to seemingly start the process all over again.
  • As I said, I have not seen this type of brainwave activity in any of the previous sessions, and am not sure at this point the meaning of this behavior.

Front Sensors (AF7, AF8)

  • The described behavior of BetaandGamma clearly comes from the Front part of the brain.
  • In the Front-Left sensor (AF7), shown below, that same behavior can be visually identified.
  • Another thing that can also be identified is the very largeDeltaoscillations.
    • This is not caused by signal noise. It may be caused by blinking, but it’s not present as symmetrically in the Right-Front sensor, so I can’t say for sure. In the future, sessions dedicated to the study of blinking artifacts will be recorded and added to this website.
    • While completely different, I have observed uncommonDeltabehavior in AF7 before (e.g. Session 24).
  • In the Front-Right sensor (AF8), shown below, it’s also possible to see how muchBetaandGamma contributed to the previously described behavior — starting in a high place of dominance, decreasing, jumping back up again, and then starting to decrease again.
  • Relevant is also the big jump inGammaenergy at around 12:36, going from 0 dB to about 80 dB — that’s a very large jump.
    • Again —could this be explained by blinking or muscle tension?
    • Even though that spike was detected in all sensors, different kinds of brainwave frequencies were boosted primarily. For instance, in the Back,Alpha,ThetaandDeltawere boosted butBetaandGamma barely moved.
  • As of now, the meaning of this behavior remains unknown to me.

How Does Dominance Change Over Time?

The graphs shown below show how dominant frequencies were across the session, in %.

  • I will group the activity into three groups, based on their behavior similarity — Front-Left (AF7), Front-Right (AF8), and Back (TP9, TP10).
  • In all three groups,Betainitially decreases 40% in dominance,Gammadecreases 60% in dominance, and then they stabilize. Additionally:
    • Front-Left (AF7) is whereBetaandGamma show the highest dominance levels.
    • In the Front-Right (AF8) is whereBetaandGammaexhibit a different behavior, by rising again in dominance by the end of the session.
      • BetaandGammaincreased exclusively in AF8 in the previous Session 25. Is this a pattern emerging?
  • Alphaincreases 80% in dominance in the Front-Left (AF7) and 50% in Front-Right (AF8).
  • However, in absolute numbers,Alpha dominance is still higher in AF8. This, coupled with lower BetaandGamma dominance, indicates the Front-Right brain has less activation and the Front-Left brain has more activation. This state has been associated with positive mood and emotions, and more motivation ✅
  • Thetashows some dominance increase across all brain quadrants — in some, in a more sustained way than in others. However,Thetadominance is more interesting to me in the Front than in the Back, so let’s take a closer look.
    • In the Front-Right (AF8) there is a 33% increase in dominance that is not sustained by the end of the session.
    • In the Front-Left (AF7) there is a 275% increase in dominance that is sustained.
    • IncreasedTheta dominance (better if associated with increasedGammadominance as well1) in the front is associated with the Frontal Midline Theta rhythm, prefrontal-cortex activation, attention, focus, memory, and meditative states.

Absolute Average Values (All Sensors)

  • Alphaaverage: 54 dB
  • Betaaverage: 47 dB
  • Thetaaverage: 40 dB
  • Deltaaverage: 36 dB
  • Gammaaverage: 30 dB

Percentual Average Values (All Sensors)

  • Alphaaverage: 33%
  • Betaaverage: 24%
  • Thetaaverage: 18%
  • Deltaaverage: 15%
  • Gammaaverage: 11%

Brainwave Lateralization

Center of Gravity

For reference: the circle with the black circumference marks the central area of the brain. Activity inside it is more central and symmetrical; outside is more asymmetrical.

  • Delta’s center of gravity was located on the Center-Back quadrant, close to the central circle border. It also showed some occasional variability.
  • Theta’scenter of gravity was located in the Center-Back quadrant.
  • Alpha’scenter of gravity was located on the CenterRight-Back quadrant.
  • Beta’scenter of gravity starts outside of the Left-Back quadrant and moves towards the middle of the circle, over time, to achieve perfect Symmetry.
  • Gamma’scenter of gravity starts outside of the Left-Center quadrant and moves towards the middle of the circle, over time, to achieve Symmetry with a slight pull toward the Center-Front quadrant.
  • The starting position of the faster frequencies in the left hemisphere towards the middle point of the circle has not been observed in any previous session. However, their moving towards the circle reminds me of the very special Session 16.

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References

  1. https://www.frontiersin.org/articles/10.3389/fnhum.2023.1145282/full ↩︎

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