Summary: Researchers have developed a novel framework that quantifies control costs when the brain transitions from one state to another by taking account of neural activity.
Source: University of Tokyo
The brain performs various cognitive and behavioral functions in everyday life, flexibly transitioning to various states to carry out these functions. Scientists view the brain as a system that performs these numerous functions by controlling its states.
To better understand the properties of this control in the brain, scientists look for ways to estimate the difficulty of control, or control cost, when the brain transitions from one state to another.
So a team of researchers undertook a study to quantify such control costs in the brain, and was successful in building a framework that evaluates these costs.
Controlling transitions to some states incurs greater “costs” than controlling transitions to others. With the development of a framework for quantifying transition costs, scientists will have a way to evaluate the difficulty of the shifts between various brain states. Possibly, they might also have a quantifiable measure for explaining cognitive loads, sleep-wake differences, habituation of cognitive tasks and psychiatric disorders.
The work is published in the Journal of Neuroscience.
The team worked to build a novel framework to quantify control cost that takes account of stochasticity, or the randomness, of neural activity. This stochasticity has been ignored in previous studies.
The current control paradigm in neuroscience uses a deterministic framework that is unable to consider stochasticity. But it is well known that the neural dynamics are stochastic and the noise is ubiquitous throughout the whole brain.
“In this work, we addressed the issue of stochasticity and first proposed a novel theoretical framework that quantifies the control cost taking account of the stochastic fluctuations of the neural dynamics,” said Shunsuke Kamiya, a doctoral student in the Graduate School of Arts and Sciences at the University of Tokyo.
In their study, the researchers established the analytical expression of the stochastic control cost, which enabled them to compute the cost in high-dimensional neural data. By the analytical expression, they discovered that the optimal control cost can be decomposed into the costs to control the mean and covariance.
“This decomposition enables us to investigate how various brain areas differently contribute to controlling the transitions from one brain state to another,” said Kamiya.
The researchers also identified the significant brain regions for the optimal control in cognitive tasks in human whole-brain imaging data. They examined the significant brain regions in the optimal control of transitions from the resting state to seven cognitive task states, using human whole-brain imaging data of 352 healthy adults.
They found that, with these different transitions, the lower visual areas commonly played a significant role in controlling the means, while the posterior cingulate cortex commonly played a significant role in controlling the covariances.
The posterior cingulate cortex is the upper part of the limbic lobe, that region of the brain that plays an important role in memory and emotional behaviors.
In this study, the team only considered the optimal control cost where brain state transitions are controlled in an optimal manner, with minimization of stochastic control cost. However, in real neural systems, it is not likely that state transitions are controlled in an optimal manner.
“An intriguing future direction will be to compare the optimally controlled dynamics and the actual dynamics using neural data during tasks,” said Masafumi Oizumi, associate professor in the Graduate School of Arts and Sciences at the University of Tokyo.
Looking ahead to future research, Oizumi explains that the ultimate goal of his lab is to understand the connection between brain dynamics and human behaviors, cognitions and consciousness. “For example, we suspect that the decrease of controllability in the brain dynamics may be related to mental fatigue or the loss of consciousness. We expect that control theoretical perspective will provide a new insight to this goal,” said Oizumi.
Funding
The research is funded by grants from the Japan Society for the Promotion of Science KAKENHI, Japan Science and Technology Agency Moonshot, Japan Science and Technology Agency CREST.
About this neuroscience research news
Author: Joseph Krisher
Source: University of Tokyo
Contact: Joseph Krisher – University of Tokyo
Image: The image is in the public domain
Original Research: Closed access.
“Optimal control costs of brain state transitions in linear stochastic systems” by Shunsuke Kamiya et al. Journal of Neuroscience
Abstract
Optimal control costs of brain state transitions in linear stochastic systems
The brain is a system that performs numerous functions by controlling its states. Quantifying the cost of this control is essential as it reveals how the brain can be controlled based on the minimization of the control cost, and which brain regions are most important to the optimal control of transitions.
Despite its great potential, the current control paradigm in neuroscience uses a deterministic framework and is therefore unable to consider stochasticity, severely limiting its application to neural data.
Here, to resolve this limitation, we propose a novel framework for the evaluation of control costs based on a linear stochastic model.
Following our previous work, we quantified the optimal control cost as the minimal Kullback-Leibler divergence between the uncontrolled and controlled processes. In the linear model, we established an analytical expression for minimal cost and showed that we can decompose it into the cost for controlling the mean and covariance of brain activity.
To evaluate the utility of our novel framework, we examined the significant brain regions in the optimal control of transitions from the resting state to seven cognitive task states in human whole-brain imaging data of either sex.
We found that, in realizing the different transitions, the lower visual areas commonly played a significant role in controlling the means, while the posterior cingulate cortex commonly played a significant role in controlling the covariances.
