Wanted: a new paradigm for neuroscience
(An improved and updated version of this material has appeared in my book Why Materialism Is Baloney. The version below is kept for legacy purposes.)
|Illustration of a chemical synapse in the brain. Source: Wikipedia.|
In an earlier article in this blog, I discussed the extensive empirical evidence available today of the fact that the most intense subjective experiences correlate with a dampening – or even cessation – of brain activity. Examples of this are Near-Death Experiences (NDEs), mystical experiences induced through hyper-ventilation (which causes constriction of blood vessels in the brain), psychedelic trances, and Out-of-Body Experiences (OBEs) induced through G-LOC, brain damage (caused, for instance, by surgery or strokes), and even cortical deactivation through the use of high-power magnetic fields. This pattern of empirical evidence seems to contradict the current, materialist paradigm that consciousness is merely the result of brain activity. After all, how could the most intense conscious experiences correlate precisely with a reduction (and even elimination) of brain activity? There are two tentative rebuttals to this from the point of view of the materialist paradigm. In this article, I hope to show that both rebuttals are flawed.
The first materialist rebuttal is this: Brain activity is composed of both excitatory processes and inhibitory processes. Excitatory processes generate – well, correspond to – subjective experiences (perceptions, feelings, ideas, etc.). Inhibitory processes, on the other hand, dampen excitatory processes down, preventing them from arising. So the idea is that, when brain activity is impaired or reduced, the inhibitory processes are blocked. The consequence is that excitatory processes – which would otherwise be stopped before taking root – can now grow to become major subjective experiences.
This answer appears wrong on an empirical basis. If it were correct, one should observe not only a reduction of activity in certain brain regions (i.e. the inhibitory processes being blocked), but alongside it also a significant activation of other brain regions (i.e. the excitatory processes that can now take root). However, the study that identified the dampening of brain activity as the mechanism of action of psychedelics did not observe any significant activation elsewhere in the brain. So the “hallucinations” reported by the study subjects have no measurable signature in the brain; their unfathomable subjective experiences appear to have no grounding on matter. How, then, do they happen? Moreover, regardless of this particular study, it is hard to imagine that generalized reductions of blood flow to the brain (as occurs through hyperventilation, G-LOC, NDEs, etc.) can act so selectively on inhibitory processes that, although much less energy is available to drive brain metabolism as a whole, the net effect can still be a peak subjective experience. Any orthodox explanation for this today will be tentative, promissory, and generally contrived and convoluted. Do we really need to push this round peg through a square hole?
The second materialist rebuttal is that the excitatory processes are happening all the time in the brain, as part of the normal, background neural activity. Inhibitory processes simply prevent them from crossing the threshold of awareness. Therefore, no significant brain activation is necessary, since these excitatory processes are part of the sub-conscious, background noise anyway. By stopping the inhibitory processes, this background excitatory activity simply becomes conscious.
Just like the first rebuttal, this second one also appears to be false on an empirical basis. Functional MRIs can measure relatively small brain activations when, for instance, a person looks at an evocative image (e.g. a picture of war). These activations are clearly seen as areas of elevated blood flow in the brain. Since the subject’s emotional experience is postulated to be such activations, the intensity of his or her emotions should naturally be proportional to the level of blood flow in corresponding brain regions. Therefore, major mystical experiences – which subjects often consider the most intense of their lives – should correspond to levels of blood flow much higher than those of, for instance, a person looking at a picture. In fact, they should be higher than practically all ordinary cognitive activity. Yet, this is not what is observed in a functional MRI. How can that be?
The evidence shows that, although ordinary experience correlates well with brain activity, some extraordinary experiences reported by mankind through the millennia seem to have no material basis in brain function. If subjective experiences were indeed merely the result of electrochemical brain processes, then they should always, without a single exception, correlate with brain activation patterns. These activation patterns should also be proportional to the intensity of the experience. That this isn't the case is a fundamental problem for the current paradigm in neuroscience.
We need a new one.