Polarisation of brain dynamics in mania and depression.

INTRODUCTION

This work investigated brain dynamics underlying manic and depressive states in bipolar disorder.

METHODS

Resting-state fMRI data were obtained from 69 bipolar patients-34 manic, 35 depressed-and 73 healthy controls. Intrinsic brain activity was modelled as a temporal sequence of discrete quasi-stationary states (co-activation patterns), which were compared between groups and related to symptomatology.

RESULTS

Mania was associated with increased occurrence of a co-activation pattern encompassing sensorimotor network areas, which positively correlated with manic symptomatology (hyperactivity and mood elevation) and manic polarity, and negatively correlated with depressive symptomatology (retardation and apathy). Depression was associated with increased occurrence of a co-activation pattern encompassing default-mode network areas, negatively correlating with manic symptomatology (hyperactivity and mood elevation).

CONCLUSIONS

These findings suggest that polarisation of brain dynamics towards low-order sensorimotor/insular systems-subserving perception and modulation of the outer and inner/body environments-may reshape subjective experience and behaviour promoting immediate interaction with the environment, manifesting as mania. Conversely, polarisation towards high-order associative systems-subserving stimulus-independent associative processing-may reshape experience and behaviour favouring detachment from the environment, manifesting as depression. This framework illustrates how changes in the functional brain architecture may alter the structure of phenomenal experience and behaviour in physiology and psychopathology.