Biofeedback and Self-Regulation, Vol. 14, No. 3, 1989

Let ter to the Edi tor

I thank Dr. Niels Birbaumer for his thoughtful review of my book, The Hyperventilation Syndrome (1987), in an issue of this journal (1988, 13, 271-273). I would like to elaborate on a statement in that review that ques- tions one of my findings, as well as to emphasize the importance of his refer- ence to "microvibration," a phenomenon sadly overlooked by American behavioral science, but potentially of enormous interest in self-regulation methodology.

Dr. Birbaumer writes:

. . . s o m e of the recordings contain artifacts (i.e., Figure 6.7 compares wrist EMG and cortical EEG both showing the same alpha frequence (8-23 Hz), leading the author to the conclusion that "EEG reflects the vasotonic activity of the cerebral arterial vas- cular bed . . . . " T h e author is obviously unaware of the difference between muscular microvibration caused by pulse resonance, EMG and cortical EEG. See Roracher & Inanaga, Mikrovibration, Bern: Huber, 1968 [sic].

I am as thoroughly familiar with Mikrovibration as anyone can be who has a less than perfect grasp of German.

I considered the possibility that an apparently frivolous conclusion, in my book, about the validity of the EEG observed with surface electrodes would jeopardize its acceptability for publication: Reviewers, all medical con- sultants to the Johns Hopkins University Press Series in Contemporary Medi- cine and Public Health, noted my conclusion and, while not entirely comfortable with it, nevertheless let it stand.

What is it exactly that I am asserting in the passage in question? First, since arterial caliber and blood flow correlate with the fundamental frequency of the EEG, and PaCO2, the partial pressure of arterial blood CO2, these parameters are functionally interchangeable. I cite many dozen convention- al references, going back to Lennox, Gibbs and Gibbs (1938).

The graphics on page 56 superimpose power-spectral composition of the EEG taken at the scalp and EMG taken at the right wrist in a 25-year- old woman, above a facsimile of the actual, simultaneous, polygraphic traces from which the said power spectra were obtained. Standard recording tech- niques were reported.

Since power-spectral composition of biopotentials from the brain vary with PACO2 and arterial caliber, they must do so at all sites where one ob- serves the arterial vascular system, and I proceeded to compare scalp and

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260 Letter to the Editor

wrist sites. The recordings are astonishingly similar, as the figures in the book show.

It might seem irrational to question the contribution of individual and aggregate neuronal activity to the EEG. I certainly don't. I simply question their dominance in the signal. And, to assure my colleagues that I have not taken leave of my senses. I would mention that I am not the first, nor do I hope the last, to question it.

History suggests that the notion that all components in the EEG are neu- ronal arose from early studies of action potentials in peripheral nerves, the resultant "telephone switchboard" analogy, and the concept that arteries are just ducts (vas) without an electrophysiology. Gibbs, Davis, and Lennox (1935), pioneers in EEG, exemplify this position: "The electro-encephalogram is the graphic record of electrical disturbances arising in the brain. This record is analogous to the electro-cardiogram, which is the record of the electrical action current associated with the contraction of the heart" (p. 1133).

There may be a hazard in "arguing by analogy." In the review, Birbaumer clearly suggests that the aggregate knowledge

of microvibrations contradicts my assertions, as stated above. I am inclined to disagree.

Theta and alpha band biopotentials cannot be mistaken for EMG, be- cause EMG and EEG frequency ranges are not usually thought to overlap. Second, they cannot be taken for microvibrations (MV) because these are "tremors"--mechanical in nature-and cannot be observed with surface elec- trodes, and, as Inanaga states: "die Frequenzspektren yon MV und EEG ganz verschiedene Verl/iufe zeigen, sodass zwischen MV und gehirnelektrischen Vorg~ingen keine direkte Beziehung angenommen werden kann" (p. 99).

In other words, there is no direct relationship between MV and EEG. And since I have had the opportunity, many hundreds of times, to observe on-line EEG changes as a function of PETCO~ during breathing maneuvers, I cannot but be awed by the confirmation of the reports of the early brain electroneurophysiologists who described the relationship between PaCO2, vas- cular diameter, and cerebral blood flow, and the "dominant" EEG frequen- cy (Lennox et al., 1938; Penfield & Jasper, 1954).

Finally, evidence that pulse resonance might contaminate the EEG sig- nal, as Birbaumer suggests, if anything, strengthens my conclusions, insofar as its major effect would contrive to affect the piezoelectric biopotentials of vascular tonus picked up by surface electrodes.

Rohracher and Inanaga both support the contention, though with differ- ent degrees of enthusiasm, that circulation somehow figures in MV. The fre-

Letter to the Editor 261

quency range is certainly in the ball park. But it is yet to be determined that MV frequency varies with PACO2.

Robert Fried, Ph.D. Department o f Psychology, Hunter College, CUNY, and

Director o f the Stress and Biofeedback Clinic, Institute f o r Rational Emot ive Therapy

R E F E R E N C E S

Fried, R. (1987). The hyperventilation syndrome-Research and clinical treatment. Baltimore: Johns Hopkins University Press.

Gibbs, F. A., Davis, H., & Lennox, W. G. (1935). The electroencephalogram in epilepsy and in conditions of impaired consciousness. Archives of Neurology and Psychiatry, 34, 1133-1148.

Lennox, W. G., Gibbs, F. A., & Gibbs, E. J. (1938). The relationship in man of cerebral activi- ty to blood flow and blood constituents. Journal of Neurology and Psychiatry, 1,221-225.

Penfield, W., & Jasper, H. (1954). Epilepsy and the functional anatomy of the brain. Boston: Little, Brown.

Rohracher, H., & Inanaga, K. (1968). Die mikrovibration, Bern: Hans Huber.