# General anesthesia reduces complexity and temporal asymmetry of the informational structures derived from neural recordings in Drosophila

## TL;DR

This study uses computational mechanics to show that general anesthesia in fruit flies decreases neural complexity and temporal asymmetry, indicating a less structured and more reversible brain state.

## Contribution

It introduces a novel application of computational mechanics to neural data, revealing how anesthesia reduces complexity and temporal asymmetry in Drosophila.

## Key findings

- Neural complexity decreases under anesthesia across various brain regions.
- Anesthesia reduces temporal asymmetry in neural signals.
- Complexity differences are observable at short timescales.

## Abstract

We apply techniques from the field of computational mechanics to evaluate the statistical complexity of neural recording data from fruit flies. First, we connect statistical complexity to the flies' level of conscious arousal, which is manipulated by general anesthesia (isoflurane). We show that the complexity of even single channel time series data decreases under anesthesia. The observed difference in complexity between the two states of conscious arousal increases as higher orders of temporal correlations are taken into account. We then go on to show that, in addition to reducing complexity, anesthesia also modulates the informational structure between the forward- and reverse-time neural signals. Specifically, using three distinct notions of temporal asymmetry we show that anesthesia reduces temporal asymmetry on information-theoretic and information-geometric grounds. In contrast to prior work, our results show that: (1) Complexity differences can emerge at very short timescales and across broad regions of the fly brain, thus heralding the macroscopic state of anesthesia in a previously unforeseen manner, and (2) that general anesthesia also modulates the temporal asymmetry of neural signals. Together, our results demonstrate that anesthetized brains become both less structured and more reversible.