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A Brief History of the 40 Hertz RhythmMy purpose here is to give you some background on the 40 Hertz rhythm that will show its importance and also support the ideas that it is a system designed to optimize the brain’s processing of new discoveries. This is by no means an exhaustive review, or even an academic one.
One indication of the importance of the 40 Hertz rhythm is that it is the most highly correlated with the rate of brain metabolism (Oakes et al, 2004), suggesting that there is probably a good reason for such energy expenditure. Relatively few EEG studies of the 40 Hertz rhythm have been performed in comparison to its neurophysiological importance because of some methodological problems. In addition to the EMG (muscle contraction artifact) contamination issue, early researchers had to deal with another daunting methodological problem when measuring above 32 Hertz (cycles per second). The old style pen and paper strip physiological recorders couldn’t easily go that fast without catching paper or spitting ink across the room. Most of the current research is recorded by computers and analyzed quantitatively or printed out by newer, faster technology. It is also well known that the higher the frequency of any EEG wave, the greater the percentage of its energy is lost coming through the scalp and meninges, so the 40 Hertz rhythm appears very small and therefore unimportant when it is measured from the scalp. On the surface of the cortex, it is much larger. The Neureka! Protocol compensates for this problem.
There are several strands of scientific work that I will weave together to sketch in this brief history. They appear to be somewhat independent in origin, because two different techniques were used, electroencephalography (EEG) and magnetoencephalography (MEG). The third strand concerns the relationship between 40 Hertz and memory. The fourth strand focused on the study of meditation and other altered states such as hypnosis, using EEG. The story begins there, back in the mid-1950’s.
The original study on the EEG of meditators was by Das and Gastaut back in 1955. They reported (in French) high amplitudes of 40 Hertz rhythm from seven trained yogis, recorded from the occipital lobe (in the back of the brain) during the samadhi state. Banquet (1973), studying 12 subjects practicing transcendental meditation and recording from left occipital and frontal leads, also observed 40 Hertz during the third deep stage of meditation.
A recent study of Buddhist meditators who are followers of the Dalai Lama recorded their brainwaves as they performed an objectless meditation practice, enhancing “unconditional loving kindness and compassion”. It demonstrated increases in the 25-42 Hertz band at a number of locations on the scalp, including the prefrontal locations surrounding the middle of the forehead (Lutz et al, 2004). Subsequently, at a meeting sponsored by the Mind and Life Foundation (2005), Davidson reported that there were strikingly significant correlations between these amplitudes and the monk’s reported clarity of their meditation, on a moment to moment basis, but only for the EEGs recorded from the prefrontal sites.
For the technically minded: Davidson also reported that there was enhanced long-range synchrony of the brainwaves between sites in these meditators. Synchrony is a very confusing word for neurophysiologists, open to a number of different interpretations. The basic idea is that it is a measure which responds to the similarity of the shape of waveforms that come from two different sources. Actually, the waveform that is measured by the Peak Achievement Trainer comes from two different sources—the front tips of the right and left cerebral hemispheres. These two waveforms are superimposed or added together before we measure them. I prefer the term “superposition”. Some of the founders of neurofeedback, particularly Lester Fehmi, would call this synchrony. In a sense, then, the Neureka! Protocol responds to long-range synchrony, since the actual fiber connections between the tips of the hemispheres take a long route through the corpus callosum. Also, Davidson’s paper calls this “gamma synchrony”, but this takes some liberties with the term, since gamma generally refers to brainwave frequencies above 30 Hertz. I don’t find “gamma” precise enough to use here. In general, when I refer to the 40 Hertz band, I mean approximately 35 to 45 Hertz.
There is also some evidence that high hypnotizable subjects produce greater 40 Hertz amplitudes while they are hypnotized than low hypnotizable ones (de Pascalis, 1993). The same researcher did some very interesting work on the relationship between memory and 40 Hertz. The idea that hypnosis leads to its life-changing effects through an effect on memory mediated by the 40 Hertz rhythm is a fascinating one.
The second strand is the work of Dulio Giannitrapani and Daniel Sheer. Giannitrapani (1966) found that “increases in 35-45 Hertz occurred immediately prior to answering in tasks such as multiplication questions” (Hammond, 2000), suggesting the Aha! response to a new discovery. Sheer thought that 40 Hertz was a particular type of focused arousal (Sheer, 1984), basically a high frequency “beta” mechanism. He did not realize that a large part of the 40 Hertz signals he so carefully isolated from EMG had a different origin. Sheer (1974) found that normal children produced more 40 Hertz in their parietal cortex as they solved problems, while those with learning disabilities did not. His group (Bird et al., 1978a, b) demonstrated that people could be trained to selectively enhance their 40 Hertz rhythm and to develop conscious control over it--both increasing and decreasing it when requested--and five out of six subjects could repeat this (Ford et al., 1980) when tested one to three years later! Sheer was not interested in the 40 Hertz rhythm from the prefrontal cortex, presumably because he was so concerned about demonstrating that the effects he saw were not due to muscle artifact. Most neurofeedbackers were even more concerned and opted not to do 40 Hertz brainwave feedback anywhere on the scalp for many years. I sincerely hope that the Neureka! Protocol will help to reverse this trend.
According to Hammond (2000), Giannitrapani also found that the 40 Hertz rhythm “seemed to synchronize and coordinate neurons that process incoming sensory stimuli”. There’s not much of a leap from there to the idea that it enhances awareness, as we have found from direct observation. Some have called it the “event binding rhythm”. Other researchers have found that activation of this rhythm will not occur with meaningless words, but does occur in response to meaningful stimuli, even when you aren’t paying attention to them (see the review by Hammond, 2000). That’s just what you would expect from a brain system that is designed to respond—but only to meaningful discoveries—by increasing your awareness of them and the surrounding context, remembering them, and then rewarding you with a brief moment of satisfaction.
In an elegant series of experiments combining animal tissue work, implanted electrode studies and human MEG (magnetoencephalography), Llinas and his coworkers (1998) developed evidence for the hypothesis that there were actually two different brain systems that carried information at about 40 Hertz. Both of these systems involved feedback loops between (different) layers of the cerebral cortex and the thalamus, the organ shaped like two flattened eggs, one in each hemisphere, with a thick bridge between them in the center of the brain. Information, in the form of somewhat repetitive patterns of nerve excitation, resonates--travels back and forth--between the thalamus and the cortex at about a 40 Hertz frequency in both of these systems. One system, the specific sensory and motor relay system, relays information from the external world through the outer nuclei (technically called the extralaminar nucleii, those located outside a fiber bundle or lamina dividing each egg) of the thalamus to the cortex. It is the system in which most all of the activity related to the Focus and Alertness measurements takes place. The 40 Hertz activity in this system may not be that different than the activity in other frequency ranges, “focused arousal” as Sheer argued. The other, non-specific, thalamocortical system is uniquely set up to scan all the regions of the cortex and collect information back from them, using a beam that resonates near a constant 40 Hertz frequency. It scans the brain from front to rear 40 times a second, and delivers this information back to a more central location, the intralaminar nuclei, where it can be integrated and analyzed, combining or binding the different neural aspects of the event together. Hence, the name “event binding rhythm”. Next, the scanning function can be refined for the next pulse, modulating our awareness to emphasize the important new discoveries. This location is very close and well connected to the hypothalamus, the control center for many of the body’s important functions.
Llinas argues that consciousness is actually a result of the simultaneous neural firing produced by the coherence (I prefer superposition) of the inputs from the specific and non-specific systems on the layers of dendrites in the cortex. The specific system would then provide the content that relates to the external world, and the non-specific system would give rise to the context. Together, they generate a single cognitive experience. My perspective is that consciousness is not inherent in the brain, but rather exists in a field that is co-located with and simultaneously external to it, a multidimensional “electroholomorphic” field. In a paper I gave at the first ISSSEEM meeting in 1990, published informally in Megabrain (1993), and that is now being revised and in press for Subtle Energies, I argued that the brain is actually able to holographically project this dendritic excitation pattern into this electroholomorphic field by using the coherent radiation (a brain “laser”) that is emitted by these thalamocortical systems.
I believe that the Neureka! Protocol actually isolates the output of the non-specific scanning system that increases awareness and contributes the context to the cognition. Outside of my knowledge of the proprietary method by which it is calculated, the evidence for this is largely empirical. The “Neureka! F--Neureka! Triggers and Enlarges DVD Research Version.bxd” design shows correlations between Neureka! and both Focus and Alertness. Our preliminary testing shows that these correlations are never more than 0.06 if they are allowed to stabilize for at least three minutes. This indicates that the measures are independent of each other.
There are several lines of evidence that indicate that the 40 Hertz rhythm profoundly enhances learning and memory. Sheer speculated about this relationship in 1970 on the basis of his studies of the olfactory bulb. There are studies which show that stimulating cortical cells at more than 7 Hertz enhances long term potentiation of their ability to transmit information across synapses (Sterman, 2006). This process is triggered by calcium entering the cell every time the synapse is stimulated (Malenka and Nicoll, 1999). It would seem reasonable that faster stimulation speeds, such as 40 Hertz, would increase the amount of calcium entering the cells per second and speed up this process. Long term potentiation of a group of cells connected together (a “cell assembly”) forms a long term memory. The clearest experimental evidence for the specific role of the 40 Hertz rhythm in learning was published by Miltner et al. (1999) in Nature. They measured the EEGs of a group of young women who were learning the association between a colored light and a shock to one hand, examining those regions of the cortex that were known to be stimulated by the light and the shock to the hand. They found that there was more 40 Hertz activity in those regions of the cortex, as well as some surrounding regions, during the trials than at other times. Furthermore, they examined the coherences between the 40 Hertz outputs of the specific areas involved and compared them with other regions and other times when the specific color and shock were not paired as controls. They found clear evidence that associative learning involved increased connectivity (coherence) between these brain regions in the 40 Hertz band, and that this coherence dropped off very quickly as they examined higher or lower frequencies. In a study of epileptic patients with electrodes implanted right on their cortical surfaces, Sederberg et al, 2003 found that their short-term memory for words was related to the gamma output of electrode sites in their frontal and temporal areas, particularly near the 40 hertz band. There are several recent studies which feature relationships between gamma and theta bands, learning and memory. There is also one study which indicated that quicker reaction times are related to the faster appearance of the 40 Hertz band at relevant brain sites (Haig et al., 1999).
The study that lead to the discovery of the Neureka! Protocol produced some remarkable results that puzzled me for quite some time. I believe that they can best be understood as an indication of the power of the Neureka! Protocol in improving learning and memory. This was a small pilot study—an undergraduate thesis—performed by Marcus Perman under the supervision of Dr. Artur Pocswardowski at St. Lawrence University; the results are in Appendix A. Briefly, three groups of five young ladies were given the IVA (Integrated Visual and Auditory Continuous Performance Test) and our Concentration Protocol (without instructions) as pretests before training. These tests were repeated after the fourth and eighth (final) testing session. One group was given training on the Concentration Protocol, one on the Neureka! Protocol (both from our older software) and one was a control group given no training. To our surprise, the Neureka! group showed a very large gain (1.5 standard deviations of their original scores) in just four sessions on the IVA Full Scale Attention Quotient, and outscored the Concentration Protocol group. They also did as well as the group trained on the Concentration Protocol in learning how to concentrate, despite a lot less practice. Is it possible that they learned the pre-tests more quickly during their Neureka! practice right afterwards due to its effects on memory?
One overall reminder about interpreting these studies is that unless I have specifically stated that they were done in the prefrontal area, they may not be clearly applicable to the Neureka! Protocol.
To investigate the quality of our feedback for the Three Dimensions of Mental Processing (Focus, Alertness, and Neureka!), I surveyed 10 biofeedback experts who did a demo in our booth at the International Society for Neurofeedback and Research by asking them to fill out the Three Dimensions of Mental Processing Questionnaire #3. For each dimension, a 7 point scale was used to answer the question: "How strong do you think the relationship between your definition of single-pointed Focus and the Peak Achievement Trainer’s measurement of [the Dimension] is? Make a / anywhere along the line." Responses were permitted anywhere along a continuous line from 1 (Extremely Strong Negative) to 7 (Extremely Strong Positive). Each of the Dimension's ratings was significantly different from Neutral (4), p<.001. The averages were all between 5.8 to 6.0 (Moderately Strong Positive) and did not differ significantly from each other.
I also asked them to compare the PAT's clarity with "other types of biofeedback I have experienced". The average of the 8 responses for each of the Dimensions--Focus, Alertness, and Awareness--was "clearer than 90% of the other feedback experiences." While this was only an imperfect pilot study, it is consistent with all my experience in demonstrating our system to thousands of people.
Dr. Beverly Rubik or the Institute for Frontier Sciences recently conducted a study which shows that brainwave signals associated with feelings of happiness, love, satisfaction, gratitude, full awareness, mindfulness, peace, and the absence of stress, are related to the Neureka! feedback. The study established that the Neureka! brainwave biofeedback system, which is used in the Peak Brain Happiness Trainer, is able to give users instantaneous, clear information about these brainwaves related to these positive feelings.
The study also showed that Transcendental Meditators™ with over 10 years experience could enhance this brainwave pattern associated with good feelings much more powerfully than subjects who did not meditate, although both groups learned to increase this pattern in just one session.
Both meditators and controls were asked to try to create particular positive and negative experiences by following a description for two minutes each, while they were looking at the Neureka! feedback signal, and to rate the relationship between momentary changes in the experience and the Neureka! measure along a -100 to +100 scale, with 0 representing no relationship, 20 a mild relationship, 40 a moderate association, 60 a strong one, 80 a very strong relationship, and 100 an extremely strong connection. Eleven of the 16 adjectives showed very strong positive relationships, with the probability that they occurred by chance <.0001.
However, the meditators were far better able to reach the Neureka! state quickly upon request, indicating that practicing Transcendental Meditation™ prepared them to have these positive experiences.
To summarize, I believe the big picture is that the Neureka! Protocol reflects the moment to moment activity of a scanning system, based in the center of the brain and looking outwards, which creates the awareness of events as wholes, in their context. It is activated particularly at moments of new discovery (the Aha! experience) or the anticipation of one and results in the enhanced learning, memory, and satisfaction of accomplishment.
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Banquet, J. P. (1973). Spectral analysis of the EEG in meditation. Electroencephalography & Clinical Neurophysiology, 35, 143.
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Oakes, T.R., Pizzagalli, D.A., Hendrick, A.M., Horras, K.A., Larson, C.L., Abercrombie, H.C., Schaefer, S.M., Koger, J.V., & Davidson, R.J. (2004). Functional coupling of simultaneous electrical and metabolic activity in the human brain. Human Brain Mapping, 21, 257-270.
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