On a simple general principle of brain organization

Abstract

A possible framework to characterise nervous system dynamics and its organization in conscious and unconscious states is introduced, derived from a high level perspective on the coordinated activity of brain cell ensembles. Some questions are best addressable in a global framework and here we build on past observations about the structure of configurations of brain networks in conscious and unconscious states and about neurophysiological results. Aiming to bind some results together into some sort of coherence with a central theme, the scenario that emerges underscores the crucial importance of the creation and dissipation of energy gradients in brain cellular ensembles resulting in maximisation of the configurations in the functional connectivity among those networks that favour conscious awareness and healthy conditions. These considerations are then applied to indicate approaches that can be used to improve neuropathological syndromes.

An Integrative View on Entropic Measures Applied to the Nervous System

“…Finding that entropy associated with the number of the configurations of brain networks is largest during states of conscious awareness [35,40] is an indication that energy is maximally distributed among those networks in these behavioural states. Following thermodynamic considerations about the time evolution of the entropy, energy dissipation was found larger during conscious awareness as opposed to unconscious pathological states -seizures and coma [25]. Therefore the tendency to maximise energy distribution/dissipation emerges from those entropic measures.…”

“…It depends on the viewpoint. Having said this, the fact that surrogate signals provide similar synchrony as those during waking consciousness is a consequence of the signals measured, which at the mesoscale level reflect the activity of large cellular populations, and considering that the brain has to integrate and segregate a myriad of sensorimotor transformations simultaneously in order to adequately perceive and respond to incoming stimuli [25,51], then this neuronal activity at the microscale level is observed at higher levels as stochastic. It does not mean a healthy brain displays random activity, rather it needs to support so many different configurations of micro-level connections (the aforesaid large entropy during conscious states) that depending on the measurement it will appear as organised or as purely stochastic; if we were to follow the activity in specific microcircuits we would see organised activity, but when the recordings sample thousands of these organised microcircuits the result is a noisy, random-like time series.…”

“…As illustrations, it has been used to characterize ageing properties of the human brain through the analysis of resting state blood oxygen level dependent (BOLD) signals, indicating that the functional entropy associated with brain activity increase with age [23]; as well, a link between human intelligence and brain entropy has been sought in a study that found that brain entropy was positively associated with intelligence [24], and in the abstract of the paper the authors mention that "This relationship between high brain entropy and high intelligence indicates an essential role for entropy in brain functioning". It may be worth pointing out now one aspect, perhaps a warning, about all these entropy estimations that will be addressed in following sections, namely, that in reality rather than entropy having a "role in" some event, it is the physical meaning of the measure -energy distribution, see section 4-, its underlying physical substrate that has the role, because one should not forget that entropy is a measure we have devised to characterise natural phenomena, but whether it can be considered a cause of processes driving living systems is a matter of debate [25]. It will be emphasised in sections below that entropy is an index of energy dispersal [26] and thus energy gradients are the fundamental essence directing the evolution of natural phenomena.…”

“…Therefore the tendency to maximise energy distribution/dissipation emerges from those entropic measures. Taking the aforesaid perspective that the brain microstates represent configurations of "connecte" brain cell ensembles -it has been proposed that the nature of brain states are patterns of coordinated activity that can be observed as correlations/synchronization of activity in cell ensembles [25]-then the comment in the previous section on the equal distribution of energy among microstates maximising entropy finds here its neurophysiological correlate: energy, that is the neural activity, tends to be distributed as widely as possible in normal waking consciousness and the result of that energy distribution is the maximisation of brain microstates, the configurations of connectivity patterns among brain networks.…”

Consciousness as an Emergent Phenomenon: A Tale of Different Levels of Description

“…They appear as a result of feedback activity across large neuronal loops, and they have been associated to a myriad of cognitive functions [ 34 ]. Of crucial importance in the current context, the gamma band activity (around 40 Hz) has been associated with high cognitive functions, including consciousness; however, the generation of gamma activity may be a consequence of the natural activity of neurons during conscious experience: gamma frequencies reflect the emergence and dissolution of communication among many neuronal ensembles, fluctuations providing the variability needed in brain dynamics to process information leading to adaptive behaviors [ 35 ].…”