Brain in a Vat
Updated: Feb 26
If there is one thing that mad scientists are attracted to for personal edification, the advancement of knowledge, and of course, taking over the world, it is ‘brains’. The best way to study them, at least when you give credence to science fiction and horror genres, is to detach them from their bodies, put them in a nutrient filled vat, and connect them to all sorts of probes that measure the electrical to and fro of brain waves, or excite and depress brain cells to manipulate what the brain thinks and feels. By detaching brains from bodies, this sadly resulted in creations that were more akin to Frankenstein than Einstein, a problem that was remedied by the local gendarmes and lots of aroused peasants with pitchforks and torches. And that’s entertainment!
Now fast forward to real brains and the not so mad scientists that study them. For affective and cognitive neuroscientists, brain imaging (fmri) and ‘in vivo’ or direct stimulation of cellular arrays in the brain are the primary methods to understand how affect is instantiated in the brain, yet cannot account for how neuro-muscular stimuli modulate affect. In other words, the afferent or direct input from the musculature is neglected because of limitations of the observational tools that neuroscientists use, thus effectively making the brain virtually if not literally detached from the body, or disembodied. But neglect is not a research strategy, and impedes the explanatory power of neuroscience. The result does not quite make for Frankenstein, but models of the mind that are more akin to Frankenstein, who was not exactly a true model of a mind.
So what’s neglected?
A trifling matter of proprioception.
So, what’s a proprioceptor?
Proprioceptors (sensory receptors) are located in our muscles and joints and respond to changes in the relative activity of the overt and covert musculature. They also induce changes in affective states in the brain. An example of this is how we experience pleasure. Unlike other functions in the brain, from perception to thinking, the neural source of our pleasures are localized in the brain as specialized groups of nerve cells or ‘nuclei’, or ‘hot spots’, located in the midbrain. These nuclei receive inputs from different sources in the nervous system, from 'exteroceptive' or proprioceptive stimuli (neuro-muscular activity) to interoceptive stimuli (satiation and deprivation and associated visceral input) to cognitive stimuli (novel positive or negative means-end expectancies), and all modulate the activity of these nuclei which release or inhibit endogenous opioids that embody the rainbow of pleasures which mark our day.
For example, relaxation induces opioid activity and is pleasurable, but tension inhibits it and is painful. Similarly, satiation inhibits our pleasure when we eat, and deprivation or hunger increases it. Finally, positive novel means-ends expectancies enhance our pleasures, and negative expectancies inhibit them. It is this interleaving of proprioception, interoception, and cognition that makes our affective world go round. Thus, for our sensory pleasures (eating, drinking), watching an exciting movie makes popcorn taste better than when watching a dull or depressing movie. This also applies to when we are relaxed, as thinking or performing meaningful activity is reflected in pleasurable ‘flow’ or ‘peak’ experiences when we are engaging in highly meaningful behavior while relaxed. (Meaning will be defined as anticipated or current behavior that has branching novel positive implications, such as creating art, doing good deeds or productive work). Thus if we are tense, we find our pleasures are reduced, and if we are relaxed, they are enhanced, and these affective states are modulated in turn by abstract properties of cognition. That is, our pleasures are highly dependent not only upon how we think but how our bodies overtly and covertly ‘move’, and by depriving a brain of a body, we cannot fully understand or maximize our pleasures, which can get one a bit grumpy and prone to overturn apple carts. You know, like Frankenstein.