The human brain and nervous system have astonishing capabilities that allow us to make sense of the environment around us in a multitude of ways (touch, taste, sound, smell, sight). But is it possible that our brain also restricts what we can sense?
Aldous Huxley famously suggested that our brains might also act as a ‘reducing valve’, restricting our access to a much greater amount of information actually available to us via ‘psi’-like abilities such as telepathy and clairvoyance. In this he was following the suggestion of philosopher C.D. Broad, who himself was citing a proposal by Henri Bergson:
The suggestion is that the function of the brain, nervous system, and sense organs is eliminative and not productive. Each person is at each moment capable of remembering all that has ever happened to him and of perceiving everything that is happening everywhere in the universe. The function of the brain and nervous system is to protect us from being overwhelmed and confused by this mass of largely useless and irrelevant knowledge, by shutting out most of what we should otherwise perceive or remember at any moment, and leaving only that very small and special selection which is likely to be practically useful.
According to this theory, the ‘reducing valve’ of the brain evolved to enhance our biological survival – while small amounts of psi-received information might be helpful to us, being overwhelmed by irrelevant information would render us as easy prey for other predators. Huxley believed that psychedelics offered one method for ‘opening up’ this reducing valve and exposing us to a wider range of sensory inputs.
And now, perhaps, there is some experimental support for the idea. In a paper published in the journal Cortex (“Enhanced mind-matter interactions following rTMS induced frontal lobe inhibition“), researchers followed up on an earlier study they had conducted – investigating a neurobiological model they had proposed based on Bergson’s suggestion, in which the frontal lobes of the brain act as a filter to inhibit psi – which had resulted in significant mind-matter interactions in two individuals with frontal brain lesions.
One had a tension pneumocephalus and the other had behavioral variant frontotemporal dementia associated with a mutation in the C9ORF72 gene… The experimental task was to influence output of a Random Event Generator translated into movement of an arrow on a computer screen to the right or left. Compared to a well-designed control condition, both individuals demonstrated a significant effect in moving the arrow on the screen contralateral to the side of their primary lesion overlap, i.e., to the right.
Based on these findings, in the new study the researchers adopted a new method of testing if the frontal region of brain acts a filter to inhibit psi: they used repetitive transcranial magnetic stimulation (TMS) to induce reversible brain lesions in the left medial middle frontal region in healthy participants, making it feasible to test a larger number of individuals for psi capabilities – 108 in all, divided into 3 groups of 36 (testing left side of the brain, right side of the brain, and ‘sham-testing’/control group).
Each participant took part in 500 trials (presented in 5 blocks of 100 trials lasting approximately 10 minutes) trying to move the arrow to the left, and then another 500 trials trying to move the arrow to the right. After they had completed these 1000 trials and left the room, another 1000 trials were run with no human present in the room trying to move the arrows.
Once the experiment was complete, the researchers analyzed the data and found that:
As predicted by our a priori hypothesis, we demonstrated that healthy participants with reversible rTMS induced lesions targeting the left medial middle frontal brain region showed larger right intention effects on a mind-matter interaction task compared to healthy participants without rTMS induced lesions…
Thus, we replicated the previous findings which we reported in two participants with brain lesions…These robust findings across different brain pathologies in neurological patients, as well in healthy participants with reversible rTMS induced brain lesions, support the concept that the brain acts as a filter to inhibit psi and that the left medial middle frontal region, involving one or more of Brodmann areas 9, 10, and 32, is a key anatomical component of this filter.
Furthermore, they believe that their findings suggest a possible neuroanatomical mechanism for manifestations of psi in other circumstances such as during use of psychedelics – for instance, via a reduction of cerebral blood flow in the medial prefrontal cortex caused by psilocybin.
However, their conclusions included what appears to be an important caveat. “This significant effect,” the paper notes, “was found only after we applied a post hoc weighting procedure aligned with our overarching hypothesis. We applied the weighting procedure in the statistical analysis because neural inhibition due to rTMS was expected to decline over time.” More specifically: to account for an expected decline in neural inhibition, they applied greater weighting to the earlier intention trials (that is, those that were closer in time to the stimulation than to trials that occurred later). However, they say, “regardless of whether we set the mid-point of the taper around the transition between the first and second set of 500 intention trials, around the 300th trial or around the 700th trial, the mind-matter interaction effect following the induced left medial middle frontal lesion was significant. Thus, our findings appear robust regardless of how the weighting is applied.” Nevertheless, this post-hoc weighting seems a likely weakness that skeptics will raise in objections against taking the study seriously (if it was expected, why nnot just run shorter sessions?).
The study researchers however believe that their findings in healthy participants with rTMS induced reversible brain lesions…
…are potentially transformative for the way we view interactions between the brain and seemingly random events. They replicate our previously published findings in individuals with damage to their frontal lobes and support the concept that the brain serves as a filter to block psi effects. This may help explain why these effects are so small and hard to replicate in healthy participants.
