Irreversibility
202306071528
Status:
Tags: arrow of time entropy dynamical system
Irreversibility is an estimation of the true value of production entropy. It measures the asymmetry in causal interactions between two time-series, which points toward the asymmetry in directionality of information flow.
The INSIDEOUT framework assumes that irreversibility is a measure of how much the external environment drives intrinsic dynamics. Since extrinsic dynamics will first affect sensory regions at the bottom of the Brain hierarchy, a change in irreversibility will reflect the extent to which the brain is being driven by external dynamics.
Implementation
The asymmetry in temporal processing of the environment (the level of reversibility), also called the arrow of time, directly measures the breaking of the detailed balance (detailed causal interactions) in brain dynamics Deco2022 → approximates true measure of production entropy
- INSIDEOUT is a framework which estimates the irreversibility (arrow of time) based on pairwise comparisons of forward signals across the brain (Deco2022)
- Form of cross-correlation and distinct from Granger causality
- Variability of irreversibility represents hierarchy (degree of asymmetry in causal interactions b/w elements)
Alternative methods exist for assessing differences in effective connectivity and hierarchical processing, including NDTE (Deco2021), transfer entropy (a measure of Granger causality), TENET.
Seif2021 and Jarzynski2011 measured the level of irreversibility by estimating the arrow of time in the underlying signals of a dynamical system. Their method requires forward and reversed time-series, and uses machine learning to distinguish between the two.
- Computationally expensive, and Deco2022 improves on it
the brain is inside-out
the brain is hierarchically organized
psychedelics flatten the brain’s hierarchy