Arousal Fluctuations Govern Oscillatory Transitions Between Dominant and Occipital Activity During Eyes Open/Closed Conditions.

Arousal results in widespread activation of brain areas to increase their response in task and behavior relevant ways. Mediated by the Ascending Reticular Arousal System (ARAS), arousal-dependent inputs interact with neural circuitry to shape their dynamics. In the occipital cortex, such inputs may trigger shifts between dominant oscillations, where activity is replaced by activity, or vice versa. A salient example of this are spectral power alternations observed while eyes are opened and/or closed. These transitions closely follow fluctuations in arousal, suggesting a common origin. To better understand the mechanisms at play, we developed and analyzed a computational model composed of two modules: a thalamocortical feedback circuit coupled with a superficial cortical network. Upon activation by noise-like inputs originating from the ARAS, our model is able to demonstrate that noise-driven non-linear interactions mediate transitions in dominant peak frequency, resulting in the simultaneous suppression of limit cycle activity and the emergence of oscillations through coherence resonance. Reduction in input provoked the reverse effect - leading to anticorrelated transitions between and power. Taken together, these results shed a new light on how arousal shapes oscillatory brain activity.