The title is cribbed from one of the most overlooked papers/commentary (IMO) of all time in neuroscience. The article is based on the work of a pediatrician who was investigating the longitudinal effects of hydrocephalus, a condition in which the brain fills up with CSF and this compresses or retards the growth of brain structures.
The work is pretty shocking as he come across adults in professional careers who had brain cavities nearly completely filled with fluid, and total mass 1/10th that of a “normal” brain. The bizarre part of it all? These individuals weren’t even aware that they were particularly different from anyone else.
One of the cornerstones of modern cognitive fields, psychiatry, psychology, and many neuroscience specialties is this concept that behavior is the product of cortical or limbic processing, that the complex interplay of various regions are essential, or even pre-requisite for cognitive function.
Often, we present the brain as a series of hubs, and assert that a particular “disease” or function is the result of “dysfunction” in one particular area, something u/jndew aptly described as “modern phrenology”. This conceit is so engrained into neuroscience now, that it’s almost impossible to find a paper researching cognitive topics which isn’t wholly reliant on them.
My break from this construct (and ultimately what was a major turning point in the model), was working through insult and lesion studies. There’s a lot of reasons why these are bad science as a whole, but they do present a way to test the generally accepted regional activity conceits.
After reviewing quite a bit of work in this area, it dawned on me that there’s literally no region of the cortex or limbic system which are necessary for behavior. There are individuals alive who’ve had -ectomies done to literally every single part of the cerebrum and limbic regions, some bilaterally, and many with “improved” function afterward. The younger the indivudals are (pre-puberty) when these surgeries take place, the more likely they retain “normal” function afterward.
It introduced the concept that maybe all of these fancy maps of cognitive function were bullshit, and led to the search for why they might be bullshit.
I’ve been pretty critical about how psychiatry/psychology is practiced, and described the assumptions they are based on as being marginally more consistent than astrology for most definitions and constructs.
Additionally, I’ve been extremely critical of psychiatric constructs being used as the basis for neuroscientific research as being harmful to the field and our understanding, largely because of the lack of validity of the psychiatric constructs.
The primary driver of these positions is that nearly all of our understanding of brain function does not derive from the actual mechanics of brains, but psychiatric definitions. And it’s been a stick in the wheel of progress for the last 100 years.
When neuroscience first started assuming that the hippocampus was critical for the formation and recollection of memory for instance, it was because Henry Molaison had most of his limbic regions hacked out bilateraly, and it was nearly arbitrarily assigned the function of memory because although healthy, HM was unable to articulate certain types of memory.
And the conceit just never went away, we built layers and layers of supporting “evidence” on top of this anecdote, despite evidence which was clearly contrary to the conceit. Once “Alzheimer’s Disease” etiology became popularly associated with the hippocampus, despite the global degeneration in Alzheimer’s (because that’s where memory is of course), it’s been written in stone ever since.
The whole mass of psychiatric bullshit revolving around the pre-frontal cortex was started in a similar manner with Phineas Gage’s injuries, and since this neatly correlated to existing phrenological/localized function concepts (along with Broca’s area), neuroscience simply adopted these psychiatric anecdotes and has been building on them ever since.
Our view of the amygdala as a source of “fear” and “anxiety” is largely driven by psychiatry, and the complete blindspot regarding the contributions of the cerebellum and brainstem are also largely driven by these self perpetuating myths built on anecdotal evidence. The view of the nucleus accumbens as a “reward center” is purely psychiatric/psychological language that we’ve forced onto the physiology, to the detriment of us all.
Of course the obvious response to this is look at the volume of evidence, how could it possibly all be wrong? Which begs the question, if it was right, why is all this still a mystery under those models?
Is there a precedent for us to have such highly supported scientific constructs ultimately turn out to be completely wrong? Yes, literally all of science ever was more wrong before it became less wrong.
And this is the core of my issue with the psychiatrization of neuroscience, is that it breaks the mechanisms with which science is self correcting, because it relies on unquestioned or assumed inviolable constructs inherited from psych conceits. Is depression a “disease”?
Despite all of the evidence produced without the assumption that we are researching “depression”, despite the massive data sets now available which still cannot reliably determine the difference between a “depressed” brain and “normal” brain, neuroscience is still compelled to understand nervous systems in this context.
This has led us to grossly misunderstand the question of “how do nervous systems function”. How is it possible that individuals with little to no cortical or limbic tissue can live a relatively “normal” life? How is it possible that this complex, careful interconnectedness of brains can be upended by -ectomy surgies with “improved” affect?
Why can we create memory without a hippocampus? If we can, do we really understand what the structure is doing? Why can we feel “fear” or “anxiety” without an amygdala? Do we really understand the function of the structure? Why do addicts still addict even with complete ablation of the nucleus accumbens (thanks for this one China)? Do we really understand the structure of this structure?
Despite the wealth of essentially null hypothesis evidence for most of our assumptions of function, why are we still employing them, without criticism? On a more core process integrity level, why do so many directly contradicting p-value results for exactly the same topics? Is it even possible to reconcile contradicting results, considering the underlying assumptions are based on nebulous specificity?
Considering all of this, there are only a few possible answers to “How much brain do we really need”.
First, the brainstem is the only region which is absolutely necessary for all function. We can clearly demonstrate that no brainstem, no nothing.
We can also demonstrate that nearly every other area of the brain can be deleted in part or whole, without suppressing functions like “memory”, “fear”, or even “addiction”.
It seems clear that nearly all cognitive function at least instantiates in the brain stem, and other regions “enhance” the function of those core instructions.
Another option might be that we simply have magical souls, ghosts in the machine which store information and magically transmit it through microtubules.
The question of how much brain do we need to process the world, the source of our cognition and “consciousness”, what is the minimum quantum of brain for humans to produce interactive social behavior, begins and ends with the brainstem.
Wittgenstein’s Certainty is Uncertain: Brain Scans of Cured Hydrocephalics Challenge Cherished Assumptions – The crazy thing about Lorber’s work is that HALF of the adult hydrocephalus group had above average “IQ”, including a couple of 2std scores.
Nucleus Accumbens Surgery for Addiction – Heh, 50% relapse rate. Just wow.
A Manual for the Glasgow Outcome Scale-Extended Interview – Crap reference, but higher Glasgow scores require brainstem insult and are the group with the overwhelmingly worst cognitive prognosis and highest mortality.