Biology subjects

Munn, B. R.

Publications and source records attributed to Munn, B. R..

3 recordsLinked to original sources

bioRxiv2023

Translating electrophysiological signatures of awareness into thalamocortical mechanisms by inverting systems-level computational models across arousal states

While consciousness never fades during wakefulness, there is a paradoxical coexistence of consciousness during dreaming states. Its also possible for sensory awareness to be either present or absent when awakened from seemingly-identical states of sedation and anaesthesia. Traditionally, these states have been characterised in terms of their electroencephalographic neural correlates, however, without clear underlying neurobiological mechanisms. To bridge this gap, we invert a validated neural mass model of the corticothalamic system using scalp EEG collected during nonlinear transitions in conscious experience and sensory awareness across varying depths of dexmedetomidine sedation. We found that a decline in conscious experience and sensory awareness with dexmedetomidine was associated with a decrease in the engagement of excitatory thalamocortical loop resonances, along with an increase in inhibitory intrathalamic loop gains. These findings shed light into the neural mechanisms of conscious experience and sensory awareness, and explain how it fades across arousal states, bridging the gap between the neural correlates of consciousness and its underlying systems-level thalamocortical mechanisms.

neuroscience↗

bioRxiv2023

A Biophysical Model of Visual Rivalry Links Cellular Mechanisms to Signatures of Conscious Perception

Contemporary models of perceptual awareness lack tractable neurobiological constraints. Inspired by recent cellular recordings in a mouse model of tactile threshold detection, we constructed a biophysical model of perceptual awareness that incorporated essential features of thalamocortical anatomy and cellular physiology. Our model reproduced, and mechanistically explains, the key in vivo neural and behavioural signatures of perceptual awareness in the mouse model, as well as the response to a set of causal perturbations. We generalised the same model (with identical parameters) to a more complex task - visual rivalry - and found that the same thalamic-mediated mechanism of perceptual awareness determined perceptual dominance. This led to the generation of a set of novel, and directly testable, electrophysiological predictions. Analyses of the model based on dynamical systems theory show that perceptual awareness in simulations of both threshold detection and visual rivalry arises from the emergent systems-level dynamics of thalamocortical loops.

neuroscience↗

bioRxiv2021

The ascending arousal system shapes low-dimensional brain dynamics to mediate awareness of changes in intrinsic cognitive states

Models of cognitive function typically focus on the cerebral cortex and hence overlook functional links to subcortical structures. This view neglects the highly-conserved ascending arousal systems role and the computational capacities it provides the brain. In this study, we test the hypothesis that the ascending arousal system modulates cortical neural gain to alter the low-dimensional energy landscape of cortical dynamics. Our analyses of spontaneous functional magnetic resonance imaging data and phasic bursts in both locus coeruleus and basal forebrain demonstrate precise time-locked relationships between brainstem activity, low-dimensional energy landscapes, network topology, and spatiotemporal travelling waves. We extend our analysis to a cohort of experienced meditators and demonstrate locus coeruleus-mediated network dynamics were associated with internal shifts in conscious awareness. Together, these results present a novel view of brain organization that highlights the ascending arousal systems role in shaping both the dynamics of the cerebral cortex and conscious awareness.

neuroscience↗