What is Health? allostasis and the evolution of human design

Peter Sterling

Department of Neuroscience, University of Pennsylvania
Friday, February 14, 2020 at 12:00pm
125 Li Ka Shing

(Note: this was a MCB/neuro seminar, not a Redwood Seminar).

Human design is constrained by natural selection to maximize performance for a given energy cost. The brain predicts what will be needed and controls metabolism, physiology, and behavior to deliver just enough, just in time. By preventing errors (allostasis), rather than correcting them (homeostasis), energy is saved. Predictive control is a core function that requires rapid computations by the whole brain to guide its tiny effector (the hypothalamus).

Survival in challenging environments required foragers to learn over decades. Learning is guided by an optimal rule that rewards each unexpected positive result with a pulse of dopamine––experienced as a pulse of satisfaction. But our recent success at providing food and comfort reduces opportunities for positive surprise and deprives us of frequent dopamine pulses upon which rest the whole edifice of behavioral regulation and mood. Lacking dopamine pulses, we grow uncomfortable and are driven to seek new sources. One route is through consumption: more food and drugs that produce great surges of dopamine. But the surprise that follows more can only be still more. Moreover physiological systems adapt to more by reducing their sensitivities, which drives our systems into damaging spirals.

Standard medicine promotes drugs to treat addictions by blocking the reward circuit. But strategies to prevent satisfaction cannot work. Standard economics promotes “growth” for more “jobs”. But economic growth drives climate change, and “jobs” devoid of long-term challenge are what now drive us to despair. To restore planetary and bodily health, we must re-expand opportunities for small satisfactions via challenging activities and thereby rescue the reward system from its pathological regime.