Neuromodulatory control of complex adaptive dynamics in the brain

Abstract

How is the massive dimensionality and complexity of the microscopic constituents of the nervous system brought under sufficiently tight control so as to coordinate adaptive behaviour? A powerful means for striking this balance is to poise neurons close to the critical point of a phase transition, at which a small change in neuronal excitability can manifest a nonlinear augmentation in neuronal activity. How the brain could mediate this critical transition is a key open question in neuroscience. Here, I propose that the different arms of the ascending arousal system provide the brain with a diverse set of heterogeneous control parameters that can be used to modulate the excitability and receptivity of target neurons—in other words, to act as control parameters for mediating critical neuronal order. Through a series of worked examples, I demonstrate how the neuromodulatory arousal system can interact with the inherent topological complexity of neuronal subsystems in the brain to mediate complex adaptive behaviour.

Causal evidence for cholinergic stabilization of attractor landscape dynamics

“…Together, our results advance our understanding of how the cholinergic forebrain constrains the formation of the brain state dynamics that form the basis of cognitive and affective brain states. 8 , 11 …”

“… (A) Graphical representation of the effects of acetylcholine (ACh) on facilitating attractor landscape topography, in which brain states are particular locations in a low-dimensional state space. Neuromodulatory neurotransmitters are proposed to alter the topography of the landscape; 11 , 12 specifically, ACh has been linked to the deepening of attractors. 13 …”

A thalamocortical substrate for integrated information via critical synchronous bursting

“…Thus, the thalamus is poised to increase apical and basal coupling and enact upon the coupling forming cortico-thalamocortical loops that enhance apical–basal coupling ( 18 , 27 , 55 ). Further, various other mechanisms can modify the likelihood of thick-tufted L5 PN bursting that have not been considered, such as adrenergic ( 56 ) and cholinergic ( 23 ) neuromodulation ( 57 ) or ephaptic changes in subthreshold dendritic voltages ( 58 ). Nevertheless, this simplified model captures the core concept of these biological implementations: demonstrating the benefits of coordinated dynamic switching between regular and high-frequency spiking (bursting).…”

Making and breaking symmetries in mind and life

“…A further beautiful example of the power of dynamical systems perspectives on brain and mind can be found in royalsocietypublishing.org/journal/rsfs Interface Focus 13: 20230015 'Neuromodulatory control of complex adaptive dynamics in the brain' by James Mac Shine [79], who asks a key question: how can the massive complexity of nervous systems be brought under sufficiently tight control to coordinate adaptive behaviour? Shine suggests neurons are balanced close to critical point phase transitions, where small perturbations to neuronal excitability lead to nonlinear changes in overall neural activity, in order to realize this capacity to be coordinated.…”