By Antonio Fontenele (University of Arkansas, Fayetteville, AR). November 8th, 2024.
It has long been suggested that the brain operates near the critical point of a phase transition. However, the mechanisms by which the brain mediates this criticality remain poorly understood. In this study, we propose that the arousal system acts as a key biological mechanism facilitating this critical transition. To test this hypothesis, we applied a temporal renormalization group (tRG) analysis in both mouse motor cortex and a computational model. Our results show that cortical neuronal activity exhibits the greatest degree of scale invariance—closest to a tRG fixed point—at moderate levels of arousal, when the animal is alert but neither overly active nor inactive. Both low arousal (inactivity) and high arousal (intense movement) disrupt this scale invariance. We validated our findings by comparing the tRG analysis with a computational model in which arousal-related biophysical processes drive the system through a critical phase transition. Additionally, we investigated the role of the neuromodulator acetylcholine, a key mediator of arousal changes, confirming its strong correlation with behavioral states. The agreement between experimental data and the model suggests that the motor cortex approaches criticality most closely during moderate arousal, between drowsy rest and heightened activity.
Contact: Antonio Fontenele, fonteneleneto.a.j@gmail.com
Additional authors: Antonio J. Fontenele, Department of Physics, 226, 825 W Dickson, Fayetteville, 72701, Arkansas, United States of America, af080@uark.edu; J. Samuel Sooter, Department of Physics, 226, 825 W Dickson, Fayetteville, 72701, Arkansas, United States of America, sooter@uark.edu; Nivaldo A. P. de Vasconcelos, Department of Biomedical Engineering, Federal University of Pernambuco, Av. da Arquitetura, Recife, 50670-901, Pernambuco, Brazil., nivaldo.vasconcelos@ufpe.br; V. Kindler Norman, Department of Physics, 226, 825 W Dickson, Fayetteville, 72701, Arkansas, United States of America, vknorman@uark.edu; Shree Hari Gautam, Department of Physics, 226, 825 W Dickson, Fayetteville, 72701, Arkansas, United States of America, shgautam@uark.edu; Woodrow L. Shew, Department of Physics, 226, 825 W Dickson, Fayetteville, 72701, Arkansas, United States of America, vknorman@uark.edu; Shree Hari Gautam, Department of Physics, 226, 825 W Dickson, Fayetteville, 72701, Arkansas, United States of America, woodrowshew@gmail.com