Nav: Home

Functional in silico dissection of the brain during the natural wake-sleep cycle

June 30, 2020

The human brain is a complex system comprising 1010 non-linear units (neurons) that interact in 1015 sites (synapses). Considering such an astonishing level of complexity and heterogeneity, it is surprising that the global dynamics of the brain self-organize into a discrete set of well-defined states.

These states are frequently placed along a unidimensional continuum. This continuum corresponds to the level of consciousness, which is reduced in states such as sleep, general anaesthesia or post-comatose disorders. The intuition behind the concept of "level of consciousness" is that consciousness is graded and uniform.

An alternative to this conception is the multidimensional and mechanistic characterization in brain states in terms of cognitive capacities, using computational models to reproduce the underlying neural dynamics.

This is the focus of a study published in the advanced online edition of the journal NeuroImage. In this international study, the first author is Ignacio Pérez Ipiña, a researcher in the Department of Physics at the University of Buenos Aires, who enjoyed the collaboration of Gustavo Deco, ICREA research professor at the Department of Information and Communication Technologies (DTIC) and director of the Center for Brain and Cognition (CBC), at UPF, along with other researchers from research centres and universities in Germany, Argentina, Australia, Chile, Denmark and the UK.

The experimental protocol involved participation by a cohort of 63 healthy subjects. "We explore this alternative by introducing a semi-empirical model linking regional activation and long-range functional connectivity in the different brain states studied during the natural wake-sleep cycle", the authors claim. "Our model combines functional magnetic resonance imaging (fMRI) data, in vivo estimates of structural connectivity, and anatomically-informed priors to constrain the independent variation of regional activation", they add.

The functional segregation of the human brain into systems that are differentially activated during cognition has been known since the earliest days of neurology, and this knowledge was greatly advanced by the introduction of non-invasive neuroimaging tools. Due to this specialization, even if different brain states bring about global changes in brain metabolism, the functional consequences of these changes are likely to manifest regional dependence. Thus, "we performed a computational simulation of functional connectivity for the different levels of arousal in the wake-deep sleep progression", Gustavo Deco clarifies.

The best computational fit to the empirical data was achieved using priors based on functionally coherent networks, with the resulting model parameters dividing the cortex into regions presenting opposite dynamical behaviour. In this study, frontoparietal regions approached a bifurcation from dynamics at a fixed point governed by noise, while sensorimotor regions approached a bifurcation from oscillatory dynamics

"In agreement with human electrophysiological experiments, sleep onset induced subcortical deactivation, which was subsequently reversed for deeper stages. We simulated external perturbations, and identified the key regions relevant for the recovery of wakefulness from deep sleep. Our model represents sleep as a state with diminished perceptual gating and the latent capacity for global accessibility that is required for rapid arousals", Deco explains.

In conclusion, the study authors implemented a computational model that synthesizes different sources of empirical data to achieve a mechanistic and multidimensional description of the intermediate complexity of the different brain states visited during the progression from wakefulness to deep sleep. This research shows that using the proposed model, states of consciousness can be described in terms of multiple dimensions with interpretations given by the choice of anatomically-informed priors.
-end-


Universitat Pompeu Fabra - Barcelona

Related Sleep Articles:

Size and sleep: New research reveals why little things sleep longer
Using data from humans and other mammals, a team of scientists including researchers from the Santa Fe Institute has developed one of the first quantitative models that explains why sleep times across species and during development decrease as brains get bigger.
Wind turbine noise affects dream sleep and perceived sleep restoration
Wind turbine noise (WTN) influences people's perception of the restorative effects of sleep, and also has a small but significant effect on dream sleep, otherwise known as REM (rapid eye movement) sleep, a study at the University of Gothenburg, Sweden, shows.
To sleep deeply: The brainstem neurons that regulate non-REM sleep
University of Tsukuba researchers identified neurons that promote non-REM sleep in the brainstem in mice.
Chronic opioid therapy can disrupt sleep, increase risk of sleep disorders
Patients and medical providers should be aware that chronic opioid use can interfere with sleep by reducing sleep efficiency and increasing the risk of sleep-disordered breathing, according to a position statement from the American Academy of Sleep Medicine.
'Short sleep' gene prevents memory deficits associated with sleep deprivation
The UCSF scientists who identified the two known human genes that promote 'natural short sleep' -- nightly sleep that lasts just four to six hours but leaves people feeling well-rested -- have now discovered a third, and it's also the first gene that's ever been shown to prevent the memory deficits that normally accompany sleep deprivation.
Short sleep duration and sleep variability blunt weight loss
High sleep variability and short sleep duration are associated with difficulties in losing weight and body fat.
Nurses have an increased risk of sleep disorders and sleep deprivation
According to preliminary results of a new study, there is a high prevalence of insufficient sleep and symptoms of common sleep disorders among medical center nurses.
Common sleep myths compromise good sleep and health
People often say they can get by on five or fewer hours of sleep, that snoring is harmless, and that having a drink helps you to fall asleep.
Sleep tight! Researchers identify the beneficial role of sleep
Why do animals sleep? Why do humans 'waste' a third of their lives sleeping?
Does extra sleep on the weekends repay your sleep debt? No, researchers say
Insufficient sleep and untreated sleep disorders put people at increased risk for metabolic problems, including obesity and diabetes.
More Sleep News and Sleep Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Warped Reality
False information on the internet makes it harder and harder to know what's true, and the consequences have been devastating. This hour, TED speakers explore ideas around technology and deception. Guests include law professor Danielle Citron, journalist Andrew Marantz, and computer scientist Joy Buolamwini.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

How to Win Friends and Influence Baboons
Baboon troops. We all know they're hierarchical. There's the big brutish alpha male who rules with a hairy iron fist, and then there's everybody else. Which is what Meg Crofoot thought too, before she used GPS collars to track the movements of a troop of baboons for a whole month. What she and her team learned from this data gave them a whole new understanding of baboon troop dynamics, and, moment to moment, who really has the power.  This episode was reported and produced by Annie McEwen. Support Radiolab by becoming a member today at Radiolab.org/donate.