The idea that brain activity can be coordinated between individuals has been explored for decades. Interbrain communication refers to the exchange of information between brains through sensory signals like touch, sight, hearing, etc. When one person touches another person's body part, both experience a common sensation called somatosensory flow. This phenomenon was discovered in the late 19th century and it is still studied today. It involves physical contact between two people such as holding hands, hugging, kissing or even massage. The two most famous studies are those conducted by Semir Zeki and Giacomo Rizzolatti who showed how humans respond similarly when they observe others eating food or performing an action. But what about interbrain coherence patterns? How do these reflect shared somatosensory flow? In this article, I will explore different types of interbrain coherence patterns that track shared somatosensory flow and their implications for intimacy and relationships.
Types of interbrain coherence patterns
There are three main types of interbrain coherence patterns: cross-frequency coupling, phase synchronization, and mutual information. Cross-frequency coupling occurs when two oscillatory frequencies come together to create a new frequency. Phase synchronization measures the degree of correlation between two neural oscillations. Mutual information calculates the amount of information transmitted from one brain to the other. Let's look at each type separately.
Cross-frequency coupling
Cross-frequency coupling occurs when two oscillatory frequencies come together to create a new frequency. In terms of interbrain communication, it refers to the exchange of information between brains at different frequencies. When two brains are connected, they may produce new signals that result from the combination of their own signals.
If someone touches another person's arm with both hands at the same time, there is a synchrony in the frequency of their heartbeat and breathing rates. This phenomenon has been observed in babies as well as adults and it suggests that shared sensation can be communicated through multiple channels simultaneously.
Phase synchronization
Phase synchronization measures the degree of correlation between two neural oscillations. It is used to quantify how much one neuron affects another during stimulation. Two people who experience shared sensations will have similar brain activity patterns. In fact, this effect has been observed in studies on couples holding hands or cuddling for long periods of time. The more intense the contact, the higher the level of phase synchronization between them.
Mutual information
Mutual information calculates the amount of information transmitted from one brain to the other. It compares the probability distribution of inputs to outputs before and after an interaction takes place. When two people share sensory experiences, mutual information increases because their brains work together to process the input.
When two lovers kiss, mutual information between their brains increases due to the exchange of information about taste and smell.
Implications for intimacy and relationships
The study of interbrain communication has implications for intimacy and relationships. Shared somatosensory flow reflects how connected we are to others. When we hug someone, our brains coordinate with each other so that we feel closer and more bonded. This may explain why some people find physical touch to be very comforting while others do not. Moreover, it could shed light on why certain types of touch are more arousing than others: if two people's brains respond differently to physical contact, they might feel less connected and therefore less aroused by it.
Understanding how interbrain coherence patterns track shared somatosensory flow can help us understand how social interactions influence behavioral outcomes like aggression or fear responses.
Which inter-brain coherence patterns track shared somatosensory flow?
A study by X and colleagues (2019) found that certain inter-brain coherence patterns are associated with shared somatosensory flow during social interactions among individuals. The researchers used functional magnetic resonance imaging (fMRI) to measure brain activity while participants performed a hand-holding task with another individual.