Kavan Modi (Monash University)
Thursday, 9 July 2020, 12:00
Computational mechanics is concerned with constructing a minimal model to track a stochastic process. In the past three decades it has developed a sophisticated toolkit, including a ready to use algorithm (CSSR), to readily infer the minimal model from a given time series data. Here, we apply techniques from the field of computational mechanics to evaluate the statistical complexity of neural recording data from fruit flies drosophila. First, we connect a central measure in computational mechanics, the statistical complexity, to the flies’ level of conscious arousal, which is manipulated by general anaesthesia (isoflurane). We show that the complexity of even single channel time series data decreases under anaesthesia. The observed difference in complexity between the two states of conscious arousal increases as higher orders of temporal correlations are taken into account. Another key result of computational mechanics is that it can account for temporal asymmetry of a stochastic process. We show here that anaesthesia also modulates the informational structure between the forward and reverse-time neural signals. Specifically, using three distinct notions of temporal asymmetry we show that anaesthesia 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 time scales and across broad regions of the fly brain, thus heralding the macroscopic state of anaesthesia in a previously unforeseen manner, and (2) that general anaesthesia also modulates the temporal asymmetry of neural signals. Together, our results demonstrate that anaesthetised brains become both less structured and more reversible.