Canalization and plasticity in psychopathology

This theory-building paper (2022) introduces a new model of psychopathology called canalization, which is a form of plasticity that relates to increased model precision. It suggests that TEMP, combined with psychological support, can counter the entrenchment of canalization in pathological phenotypes, and offers suggestions for experiments to test its main hypotheses and implications.

Abstract

“This theoretical article revives a classical bridging construct, canalization, to describe a new model of a general factor of psychopathology. To achieve this, we have distinguished between two types of plasticity, an early one that we call ‘TEMP’ for ‘Temperature or Entropy Mediated Plasticity’, and another, we call ‘canalization’, which is close to Hebbian plasticity. These two forms of plasticity can be most easily distinguished by their relationship to ‘precision’ or inverse variance; TEMP relates to increased model variance or decreased precision, whereas the opposite is true for canalization. TEMP also subsumes increased learning rate, (Ising) temperature and entropy. Dictionary definitions of ‘plasticity’ describe it as the property of being easily shaped or molded; TEMP is the better match for this. Importantly, we propose that ‘pathological’ phenotypes develop via mechanisms of canalization or increased model precision, as a defensive response to adversity and associated distress or dysphoria. Our model states that canalization entrenches in psychopathology, narrowing the phenotypic statespace as the agent develops expertise in their pathology. We suggest that TEMP – combined with gently guiding psychological support – can counter canalization. We address questions of whether and when canalization is adaptive versus maladaptive, furnish our model with references to basic and human neuroscience, and offer concrete experiments and measures to test its main hypotheses and implications.“

Authors: Robin L. Carhart-Harris, Shamil Chandaria, David E. Erritzoe, Adam Gazzaley, Manish Girn, Hannes Kettner, Pedro A. M. Mediano, David J. Nutt, Fernando E. Rosas, Leor Roseman, Chris Timmermann, Brandon Weiss, Richard J. Zeifman & Karl J. Friston

Summary of Canalization and plasticity in psychopathology

This theory-building article revives a classical bridging construct, canalization, to describe a new model of a general factor of psychopathology. It proposes that canalization is a defensive response to adversity and associated distress or dysphoria, and that Temperature or Entropy Mediated Plasticity (TEMP) – combined with gently guiding psychological support – can counter canalization.

Introduction

The construct of canalization was introduced in biology in 1942 by British evolutionary scientist, Conrad H. Waddington, and can be used in reference to the development of psychopathology.

Canalization does not fit the definition of neuroplasticity because it describes how features of the mind, brain, or behaviour become less able to change in a non-specific way.

The distinction between Hebbian plasticity and associative plasticity is key to understanding the present paper, and requires a reconsideration of some popular assumptions regarding plasticity.