CNI Chalk Talk: Peter Sterling

Peter Sterling
Department of Neuroscience
University of Pennsylvania

Allostasis: Human Design, Society, and Healing

The human brain out-thinks a supercomputer. To achieve this performance yet remain portable, the brain follows principles of efficient design (Sterling and Laughlin, 2015). The body needed for the brain’s care and feeding costs 4-fold more energy than the brain, so it too must follow efficient design. The body’s mechanisms for efficient regulation are captured by a model that I developed with Joseph Eyer (Sterling and Eyer, 1988) and named “allostasis.” The model draws on my investigations of neural circuits and on my life-long engagement with the problems of modern society.

Allostasis proposes that physiological regulation is efficient because the brain predicts what the organism will need at all levels and adjusts all responses to match. Predictive regulation: (i) reduces errors; (ii) promotes efficient coupling across levels; and (iii) allows trade-offs between systems, thus optimizing use of system capacity. Effective prediction requires learning at all levels and across all time scales -- and this couples individual human design to societal design. For example, a brain that chronically predicts societal danger will chronically elevate blood pressure, release chemicals that stiffen up arterial walls and stimulate the appetite for salt.

To select a behavior from among various possibilities, the brain uses a circuit for reward learning. The circuit selects the behavior that it values most (salt, food, warmth, sex); then if the reward exceeds the predicted value, the circuit delivers a pulse of dopamine to various brain regions. We experience the pulse of dopamine as a pulse of satisfaction and learn to repeat the behavior. The pulse is designed to be brief and to shrink with repetition (as the reward becomes more predictable). Thus the circuit, which we share with flies, evolved to navigate diverse sources of small satisfaction. As market based society shrinks reward diversity, the few that remain tend to become addictions.

Predictive control under conditions of chronic social disruption and shrunken sources of reward causes chronic disease, such as established hypertension; drug addictions, obesity, and type 2 diabetes. Generally the system is not “broken”. Rather, the brain is merely addressing its predictions by adapting the system to a particular state. Consequently an effort to correct the problem with a drug tends to evoke brain-driven compensations that require more drugs and eventually reduce response capacity. Many of our current afflictions would be more effectively healed at the social level – by reducing the sources of chronic danger and by re-expanding the diversity of small satisfactions.

References:

• Sterling and Laughlin (2015) Principles of Neural Design MIT Press.
• Sterling and Eyer (1988) Allostasis: a new paradigm to explain arousal pathology. In: Handbook of Life Stress, Cognition and Health (Fisher S; Reason J, eds), pp 629-649. J. Wiley & Sons.
• Sterling (2012) Allostasis: A model of predictive regulation. Physiol. Behav. 106: 5-15.
• Sterling (2014) Homeostasis vs. Allostasis: Implications for brain function and mental disorders. JAMA Psychiatry 71: 1192-3.
• Sterling (2016) Why we consume: neural design and sustainability. Great Transition Initiative. http://www.greattransition.org/publication/why-we-consume.
• Sterling (2016) Why we abandon a live of small pleasures Great Transition Initiative.

Lunch will be served.