Noradrenergic Modulation of Whole Brain Energy Landscape Mediates Perceptual Switches

Visual perception relies on a distributed thalamocortical network whose modes of interaction are governed by the neuromodulatory systems. Here we set out to test the hypothesis that bursts of noradrenaline from the locus coeruleus help to facilitate shifts in perception by increasing neural gain across the cortex and flattening the whole brain ‘energy landscape’. In line with our hypothesis, shifts in the perceptual interpretation of an ambiguous image were associated with peaks in pupil diameter – a correlate of adrenergic tone. We trained a recurrent neural network (RNN) to perform an analogous task, then manipulated the gain of the RNN to mimic the effect of noradrenaline. We observed an earlier perceptual shift as a function of noradrenaline heightened gain. Leveraging a dimensionality reduced readout of the dynamics, and a measure of the energy landscape traversed by the dynamics, we developed two predictions: perceptual switches should co-occur with peaks in low-dimensional brain state velocity and with a flattened energy landscape. We used whole-brain fMRI data to test these predictions in humans, thus, confirming the role of the adrenergic system in the large-scale network velocity and flattened energy landscape topography signatures of the brain during perceptual switches.