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the world's religions, where gods spoke to men and were obeyed because they were human volition.3
There are two forms in which this hypothesis can be specified.
The stronger form, and the one I favor because it is simpler and more specific (and thus more easily verified or disconfirmed by empirical investigation), is that the speech of the gods was directly organized in what corresponds to Wernicke's area on the right hemisphere and 'spoken' or 'heard' over the anterior commissures to or by the auditory areas of the left temporal lobe.
(Note how I can only express this metaphorically, personifying the right temporal lobe as a person speaking or the left temporal lobe as a person listening, both being equivalent and both literally false.) Another reason I am inclined to this stronger form is its very rationality in terms of getting processed information or thought from one side of the brain to the other. Consider the evolutionary problem: billions of nerve cells processing complex experience on one side and needing to send the results over to the other through the much smaller commissures. Some code would have to be used, some way of reducing very complicated processing into a form that could be transmitted through the fewer neurons particularly of the anterior commissures. And what better code has ever appeared in the evolution of animal nervous systems than human language? Thus in the stronger form of our model, auditory hallucinations exist as such in a linguistic manner because that is the most efficient method of getting complicated cortical processing from one side of the brain to the other.
The weaker form of the hypothesis is more vague. It states that the articulatory qualities of the hallucination were of left hemisphere origin like the speech of the person himself, but that 3 I do not mean to imply that the bicameral transmission was the only function of the anterior commissure. This commissure interconnects most of the two temporal lobes, including a good part of the posterior portion of the inferior temporal convolution. This region is fed by a strong system of fibers sweeping down from the occipital lobe and is centrally important to visual gnostic functions. See E. G. Ettlinger, Functions of the Corpus Callosum (Boston: Little, Brown, 1965).
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its sense and direction and different relation to the person were due to right temporal lobe activity sending excitation over the anterior commissures and probably the splenium (the back part of the corpus callosum) to the speech areas of the left hemisphere, and 'heard' from there.
At the present time, it does not really matter which form of the hypothesis we take. The central feature of both is that the amalgamating of admonitory experience was a right hemisphere function and it was excitation in what corresponds to Wernicke's area on the right hemisphere that occasioned the voices of the gods.
The evidence to support this hypothesis may be brought together as five observations: (I) that both hemispheres are able to understand language, while normally only the left can speak; (2) that there is some vestigial functioning of the right Wernicke's area in a way similar to the voices of gods; (3) that the two hemispheres under certain conditions are able to act almost as independent persons, their relationship corresponding to that of the man-god relationship of bicameral times; (4) that contemporary differences between the hemispheres in cognitive functions at least echo such differences of function between man and god as seen in the literature of bicameral man; and (5) that the brain is more capable of being organized by the environment than we have hitherto supposed, and therefore could have undergone such a change as from bicameral to conscious man mostly on the basis of learning and culture.
The rest of this chapter will be devoted to these five observations.
1. That Both Hemispheres Understand Language The gods, I have said with some presumption, were amalgams of admonitory experience, made up of meldings of whatever commands had been given the individual. Thus, while the divine
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areas would not have to be involved in speech, they would have to be involved in hearing and in understanding language. And this is the case even today. We do in fact understand language with both hemispheres. Stroke patients who have hemorrhages on the left side of the cortex cannot speak, but still can understand.4
If sodium amytal is injected into the left carotid artery leading to the left hemisphere (the Wada test), the entire hemisphere is anesthetized, leaving only the right hemisphere working; but the subject still can follow directions.5 Tests on commissurotomized patients (which I shall describe more fully in a moment) demonstrate considerable understanding by the right hemisphere.6
Named objects can usually be retrieved by the left hand, and verbal commands obeyed by the left hand. Even when the entire left hemisphere, the speech hemisphere, remember, is removed in human patients suffering from glioma, the remaining right hemisphere immediately after the operation seems to understand the surgeon's questions, though unable to reply.7
2. That There Exists Vestigial Godlike Function in the Right Hemisphere
If the preceding model is correct, there might be some residual indication, no matter how small, of the ancient divine function of the right hemisphere. We can, indeed, be more specific here.
Since the voices of the gods did not, of course, entail articulate 4 Thi s is a general observation — true of cases I have interviewed personally.
5 T h e Wad a test is presently part of presurgical procedures before brain surgery in the Montreal Neurological Institute. See J. Wada and T. Rasmussen, "Intracarotid Injection of Sodium Amytal for the Lateralization of Cerebral Speech Dominance,"
Journal of Neurosurgery, 1960, 17: 266-282.
6 M. S. Gazzaniga, J. E. Bogen, R. W. Sperry, "Laterality effects in somesthesis following cerebral commissurotomy in man," Neuropsychologia, 1: 209-215. See also Stuart Dimond's excellent discussion of the problem in his The Double Brain (Edinburgh and London: Churchill Livingstone, 1 9 7 2 ) , p. 84.
7 Aaron Smith, "Speech and other functions after left (dominant) hemispherec-tomy," Journal of Neurology Neurosurgical Psychiatry, 29 : 4 6 7 - 4 7 1 .
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speech, did not entail the use of the larynx and mouth, we can rule out what corresponds to Broca's area and the supplementary motor area, to a certain extent, and concentrate on what corresponds to Wernicke's area or the posterior part of the temporal lobe on the right or so-called nondominant side. If we stimulate it in this location, would we hear then the voices of the gods as of yore? Or some remnant of them? Something that would allow us to think that three thousand years ago its function was that of the divine direction of human affairs?
We may recall that this was indeed the very area which had been stimulated by Wilder Penfield in a famous series of studies a few years ago.8 Let me describe them in some detail.