Human decision making depends on flexible processing of complex information, but how the brain can adapt processing to momentary task demands has remained uncertain. In a new article published in the journal Nature communications, researchers at the Max Planck Institute for Human Development have now described several crucial neural processes revealing that our brain networks can quickly and flexibly switch from a rhythmic state to a “noisy” state when the need to treat information increases.
Driving a car, deliberating on different financial options, or even thinking about different life paths requires us to process an overwhelming amount of information. But not all decisions make the same demands. In some situations, decisions are easier because we already know what information is relevant. In other situations, uncertainty about what information is relevant to our decision requires us to take a broader view of all available information sources. The mechanisms by which the brain flexibly adapts information processing in such situations were previously unknown.
To reveal these mechanisms, researchers at Lifespan Neural Dynamics Group (LNDG) at the Max Planck Institute for Human Development and the Max Planck UCL Center for Computational Psychiatry and Aging Research designed a visual task. Participants were asked to visualize a moving cloud of small squares that differed from each other in four visual dimensions: color, size, brightness and direction of movement. Participants were then asked a question about one of the four visual dimensions. For example, “Were there more squares moving left or right?”. Before seeing the squares, the study authors manipulated “uncertainty” by educating participants about characteristics they could be asked about; the more relevant characteristics there were, the more uncertain participants became about which characteristics to focus on. Throughout the task, brain activity was measured using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI).
First, the authors found that when participants were more uncertain about the relevant feature in the upcoming choice, participants’ EEG signals shifted from a rhythmic mode (present when participants could focus on a single feature) to one. more arrhythmic and “noisy” mode. “Brain rhythms can be particularly useful when we need to select relevant rather than irrelevant inputs, while increased neural ‘noise’ could make our brains more receptive to multiple sources of information. Our results suggest that the ability to switch between these ‘noisy’ states may allow flexible information processing in the human brain, ”says Julian Q. Kosciessa, post-doc at LNDG and first author of the article.
Additionally, the authors found that the extent to which participants switched from rhythmic to noisy in their EEG signals was primarily associated with increased fMRI activity in the thalamus, a deep brain structure largely inaccessible by EEG. . The thalamus is often seen primarily as an interface for sensory and motor signals, yet its potential role in flexibility has remained elusive. The study’s findings may therefore have broad implications for our current understanding of the brain structures needed to adapt to an ever-changing world. “When neuroscientists reflect on how the brain allows behavioral flexibility, we often focus exclusively on the networks of the cortex, while the thalamus is traditionally viewed as a simple relay for sensorimotor information. Instead, our results support that the thalamus can support neural dynamics in general and could optimize brain states based on environmental demands, allowing us to make better decisions, ”says Douglas Garrett, lead author of the study. and leader of the LNDG group.
In the next phases of their research, the authors plan to study the underlying neurochemical basis of how the thalamus enables changes in neural dynamics, and whether such changes can be “tuned in” by stimulating the thalamus to the thalamus. ‘using weak electric currents.
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