Archive for June, 2007

Weekly Brain Video: Thoughts on Gamma Brainwaves 70-200+ hz

Extremely high frequency gamma was previously thought not to exist because it is difficult to measure from the scalp. However, if electrodes are implanted in the brain, it becomes clear that ultra high gamma plays an important role, and could even be the dominant frequency band of the brain.

Today’s video is a lecture by Robert Knight, a neuroscientist at Berkeley, talking about his work with high gamma.

This video is (unfortunately) only available in Real Player format. Click the image below to open it.

Robet Knight

EEG research on psychedelics, or what your brain REALLY looks like on drugs

Here is an interesting study on the effects of psychedelics measured from an EEG. For those of you who lived throught he 60’s, this is what was happening to you.

Some of the results may not be what you expected.

Effects of a Psychedelic, Tropical Tea, Ayahuasca, on the EEG Activity of the Human Brain during a Shamanistic Ritual – MAPS Magazine, Spring 2001

By Erik Hoffmann, Jan M. Keppel Hesselink, Yatra-W.M. da Silveira Barbosa

EEG data from 12 volunteers participating in a workshop in Brazil were recorded under field conditions before and after a shamanistic ritual in which the psychoactive tea, Ayahuasca, was consumed. Following three doses of the tea, the subjects showed strong and statistically significant increases of both EEG alpha (8-13Hz) and theta (4-8Hz) mean amplitudes compared to baseline while beta (13-20Hz) amplitudes were unchanged. The strongest increases of alpha activity were observed in the occipital lobes while alpha was unchanged in the frontal lobes. Theta amplitudes, on the other hand, were significantly increased in both occipital and frontal areas. Our data do not support previous findings of cortical activation with decreased alpha and increased beta activity caused by psychedelics (e.g. LSD, mescaline, psilocybin). They rather point to a similarity between the altered states produced by ayahuasca and marihuana which also stimulates the brain to produce more alpha waves. We suggest that these findings of increased EEG alpha and theta activity after drinking Ayahuasca reflect an altered state of consciousness. In this state the subjects reported increased awareness of their subconscious processes. This is an altered state comparable to, however more profound than, the meditative state. Ayahuasca seems to open up the individual to his feelings and provide personal, psychological insights, and thus it may be a valuable adjunct to psychotherapy.

Also an excerpt from the study:

EEG research of psychedelics.

The majority of EEG studies done on psychedelics appeared in the scientific journals some 30 years ago before these compounds were banned. Wikler (1954), Itil (1968) and Fink (1978) are all in agreement that psychedelics, regardless of the substance (LSD, mescaline, psilocybin), produce decreases in slow wave (alpha and theta) activity together with increases of fast (beta) activity. This low amplitude, desynchronized EEG pattern induced by psychedelics reflect an activation of the brain and is in opposition to the highly synchronized alpha pattern observed during deep relaxation. Fink (1978) found that regardless of the nature of the drug administered, EEG synchronization (alpha/theta waves) was associated with euphoria, relaxation, and drowsiness; while EEG desynchronization was associated with anxiety, hallucinations, fantasies, and illusions. Don et al. (1998) found an increase of high frequency beta (’40Hz’) with no significant change of alpha and theta activity in the EEG following the ingestion of ayahuasca. All the above studies indicate that most psychedelic compounds tend to suppress low EEG frequency activity (alpha and theta) and enhance beta activity reflecting an activation of the brain. However, other psychedelic-like compounds such as marihuana and MDMA (ecstasy) seem to have the opposite effect and increase alpha activity. In a recent, controlled placebo study, an increase of EEG alpha power, correlating with intense euphoria, was found after smoking marihuana (Lukas, et al., 1995).

Long-term effects of the use of psychedelics, using qEEG monitoring, have rarely been studied. However, in a recent study of 23 recreational MDMA users Dafters et al. (1999) found that the use of MDMA was positively correlated with absolute power in the alpha (8-12Hz) and beta (12-20Hz) frequency bands. These findings were supported recently by another study by Gamma et al. (2000) who found global increases of theta, alpha and beta power in a group of regular MDMA users compared to a control group.

You can download the full PDF version here.

Auditory Illusions

Optical illusions are well known, fun and easy to find. One of my favorites is the checkerboard illusion. I once showed that to my boss at a former job, and he refused to believe it was possible, even after I proved it using Photoshop. And, who can forget the magic eye books of the 90’s – how many millions of eye-strain-induced headaches were those responsible for?

But did you know there are also a number of Auditory illusions?

Last month, the Mighty Optical Illusions site explored some of them:

Be sure to turn “repeat” on!

Shepard’s ascending tones (MP3) – This is a recording of Shepard’s paradox synthesized by Jean-Claude Risset. Pairs of chords sound as if they are advancing up the scale, but in fact the starting pair of chords is the same as the finishing pair. If you loop this sample seamlessly then it should be impossible to tell where the sample begins and ends.

Falling bells (MP3) – This is a recording of a paradox where bells sound as if they are falling through space. As they fall their pitch seems to be getting lower, but in fact the pitch gets higher. If you loop this sample you will clearly see the pitch jump back down when the sample repeats. This reveals that the start pitch is obviously much lower than the finishing pitch.

Quickening Beat (MP3) – This recording is subtle. A drum beat sounds as if it is quickening in tempo, but the starting tempo is the same as this finishing tempo.

You can also create an auditory illusion using Binaural Beats. Set the binaural beat to less than 1 hz, or set the carrier and offset less than 1 hz away from each other. Listen through stereo headphones. It will sound as if the tones are floating around inside your head. This effect occurs because the neural process that creates binaural beats is also involved in spatially locating sounds in your environment.

Here is a sample: Binaural Beat Auditory Illusion

Here is the NP2 session I used to create it: Binaural Beat Auditory Illusion.nps


Weekly Brain Video: Carl Jung

Perhaps second only to Sigmund Freud as the most famous name in psychology, Carl Jung’s influences on modern thought are far and wide. He is responsible for many well known concepts such as the archetype, and the collective unconscious. He popularized the terms “extroversion” and “introversion”, and many personality tests are based on his work.

In these videos he talks on a range of topics, from the subconscious to individuality to life and death. Interesting stuff, from a great thinker.


Talking about a variety of topics:

Talking about life and death: