Cyclical Brain Rhythms Drive Key Cognitive Functions

Post by Soumilee Chaudhuri

The takeaway

Brain networks carry out day-to-day cognitive functions, such as focusing, remembering, and processing sensory information. The activity in these networks follows a cyclical pattern, with each activation supporting essential cognitive functions.

What's the science?

The human brain carries out numerous cognitive and bodily functions, but it has been unclear how these processes are coordinated over time. Previous studies using different forms of neuroimaging have observed directional relationships in network transitions; however, it remained unclear whether these asymmetries are part of a higher-level organization. This week in Nature Neuroscience, van Es and colleagues analyzed brain imaging data from five independent datasets and revealed that, while individual transitions appear noisy, they collectively form consistent cycles that repeat every 300–1,000 milliseconds, with each network having a preferred position within the cycle. 

How did they do it?

The study analyzed brain activity from over 800 participants across five Magnetoencephalography (MEG) datasets. Participants ranged in age from 19 to 88 years and included both males and females. MEG signals were mapped onto the brain’s cortex, divided into 38–78 regions depending on the dataset, to track how different brain areas interacted over time. Using a Hidden Markov Model, the researchers identified 12 recurring brain network states and examined the timing and direction of transitions between these states. They applied a new method, temporal interval network density analysis or TINDA, to detect characteristic sequences of network activations emerging as cycles. The makeup of this cyclical pattern, along with its strength (amount of deviations from the cycle) and speed, were quantified and analyzed for consistency across participants and their relationship with age, cognitive performance, and behavior, showing how these brain rhythms relate to key individual traits.

What did they find?

Identified brain networks followed a cyclical pattern, with cognitive and perceptual networks taking turns in a consistent and coordinated sequence. This sequence or cycle lasted approximately 300–1,000 milliseconds, and the timing and strength of these cycles were linked to age and cognitive performance. The researchers found that older adults showed much slower cycles compared to younger participants. The phase of the cycle also predicted moment-to-moment behavior, including markers of memory consolidation and reaction speed. Finally, additional findings suggested that the rate of these cycles was partly heritable, indicating a biological basis for these rhythms.

What's the impact?

This study provides compelling evidence that the natural cyclical activation of large-scale brain networks underlies essential cognitive functions. These findings shed light on the mechanisms underlying cognitive processes in the brain and highlight the potential for targeting brain network rhythms in interventions designed to enhance cognitive function.

Access the original scientific publication here.

How Does the Brain Overcome Social Exclusion?

Post by Rebecca Glisson

The takeaway

Negative emotions that come from social exclusion can be relieved through emotionally supportive social interaction between two people. During this emotional support, there is synchronized activity in the prefrontal cortex, the brain region involved in emotional regulation, between the person giving and receiving emotional support.

What's the science?

When you are excluded from a social group, it can be challenging to manage the unhappiness and upset on your own and to emotionally regulate. Having someone else to help support and comfort you, which is called interpersonal emotional regulation, may be a more effective way to handle these negative emotions, although this has not yet been studied. This week in Scientific Reports, Zhu and colleagues investigated whether interpersonal emotional regulation is more effective than intrapersonal emotional regulation for managing negative emotions in response to social exclusion, as well as the brain activity that controls these behaviors.

How did they do it?

To study the differences between intrapersonal and interpersonal emotional regulation, the authors had participants experiencing negative emotions after social exclusion events either regulate their own emotions or work with another participant to regulate their emotions. First, participants were shown pictures of someone being excluded by their peers, and then were asked to think about a time they personally experienced social exclusion. Following this, one group of participants was given a strategy to try to regulate their emotions while alone, which simulated intrapersonal emotional regulation. The interpersonal emotional regulation group, on the other hand, was paired with another person who was given a strategy to help the person experiencing social exclusion.

In a second experiment, the authors used functional near-infrared spectroscopy (fNIRS) to measure brain activity while participants were negatively reacting to social exclusion and during the interpersonal emotional regulation afterwards. The authors focused their measurements on the prefrontal cortex, the area of the brain that links emotion regulation and social interaction. Both the participants who were experiencing the negative emotions and their paired partners who were helping regulate their emotions were scanned at the same time to study if brain activity was synchronized during interpersonal emotional regulation.

What did they find?

In the first experiment, the authors found that people feeling negatively after social exclusion were better at managing those emotions with someone else than by themselves. This suggests that interpersonal emotional regulation is more effective at relieving negative feelings after social exclusion than working through the emotions alone. In the second experiment, the authors found that the left medial part of the prefrontal cortex is more active while someone is reacting negatively to social exclusion. Then, during interpersonal emotional regulation, they found that the activation of both the emotion experiencer and the emotion supporter was synchronized in the prefrontal cortex. This suggests that synchronization of activity in the prefrontal cortex between two people during interpersonal emotional regulation is the mechanism that leads to better outcomes after social exclusion.

What's the impact?

This study is the first to show that interpersonal emotional regulation is more effective than intrapersonal emotional regulation at reducing negative reactions to social exclusion, and the brain mechanisms involved with this process. These results suggest that empathy is crucial for helping others deal with social exclusion. As social exclusion is common for both children in school and adults in the workplace, and can lead to poor outcomes for both mental and physical health, it is important for studies like these to provide strategies to manage responses to social exclusion.

Access the original scientific publication here.

Brain Similarity Predicts Whether Strangers Become Friends

Post by Natalia Ladyka-Wojcik

The takeaway

Friendships are more likely to form and last between people who already share similar brain patterns in response to the world, even before they meet. These pre-existing brain similarities, beyond factors such as physical proximity or demographics, predict who grows closer over time, suggesting that deeper interpersonal compatibilities shape enduring social relationships. 

What's the science?

Humans are thought to form social networks based on their resemblance to one another in demographics, behaviors, and preferences, a phenomenon known as homophily. Yet, past attempts to link social network closeness with inter-individual similarities in self-report measures of personality traits have yielded inconsistent findings. More recent research suggests that friends share similar feelings and thoughts about the world, which are mirrored by similarities in brain-based measures. However, because these studies are cross-sectional, they cannot determine whether brain similarity predicts a future friendship or instead emerges as people become friends and influence one another through shared experiences and environments. This week in Nature Human Behavior, Shen and colleagues aimed to test whether pre-existing similarities in neural responses to naturalistic movies among strangers could predict who would later become closer in a social network.

How did they do it?

To determine whether similarities in brain activity predict who will later become friends, the authors recorded brain responses in a cohort of incoming graduate university students while they underwent fMRI scanning and watched 14 naturalistic movie clips. At later time points during the school year, the student cohort completed surveys reporting on their friendships, which allowed the authors to map out their social network. For each unique pair of participants, the authors calculated the correlation between their brain response time series at the start of the study in different brain regions, providing a measure of neural similarity, and the students’ social network positions two and eight months later, focusing on whether people who became friends had more similar brain activity than those who did not. The researchers also tested whether demographic factors like age, academic background, or shared interests predicted friendships more strongly, and whether enjoyment of the movies themselves could account for brain similarities.

What did they find?

The study found that people who later became friends, or who grew closer over time, tended to have more similar brain responses when watching the same movies before they had met. This effect was strongest in key brain regions of the frontoparietal control network, which has been linked to processing emotions, decision-making, and attention. Importantly, these similarities could not be fully explained by whether people simply enjoyed the movies or found them interesting. Whereas shared demographic factors like age accounted for some of the resemblance in brain responses between people, they did not explain the broader pattern observed in friendships that grew closer over time across the social network. Taken together, the findings suggest that friendship is shaped not only by shared backgrounds or interests, but also by deeper similarities in how people’s brains process the world around them.

What's the impact?

This study is the first to show that over time, strangers who exhibit similar brain responses for interpreting, attending to, and emotionally processing the external world are more likely to become friends and increase their social closeness. 

Access the original scientific publication here.