Simply holding hands with a comforting partner will synchronise not only breathing and heart rate, but also brain wave patterns, accompanied with a decrease in pain, found a small US-Israeli study.
The study, by researchers with the University of Colorado Boulder and University of Haifa, also found that the more empathy a comforting partner feels for a partner in pain, the more their brainwaves fall into sync. And the more those brain waves sync, the more the pain goes away.
"We have developed a lot of ways to communicate in the modern world and we have fewer physical interactions," said lead author Dr Pavel Goldstein, a postdoctoral pain researcher in the Cognitive and Affective Neuroscience Lab at CU Boulder. "This paper illustrates the power and importance of human touch."
The study is the latest in a growing body of research exploring a phenomenon known as "interpersonal synchronisation," in which people physiologically mirror the people they are with. It is the first to look at brain wave synchronisation in the context of pain and offers new insight into the role brain-to-brain coupling may play in touch-induced analgesia, or healing touch.
Goldstein came up with the experiment after, during the delivery of his daughter, he discovered that when he held his wife's hand, it eased her pain. "I wanted to test it out in the lab: Can one really decrease pain with touch, and if so, how?"
He and his colleagues at University of Haifa recruited 22 heterosexual couples, age 23 to 32 who had been together for at least one year and put them through several two-minute scenarios as electroencephalography (EEG) caps measured their brainwave activity. The scenarios included sitting together not touching; sitting together holding hands; and sitting in separate rooms. Then they repeated the scenarios as the woman was subjected to mild heat pain on her arm.
Merely being in each other's presence, with or without touch, was associated with some brain wave synchronicity in the alpha mu band, a wavelength associated with focused attention. If they held hands while she was in pain, the coupling increased the most.
Researchers also found that when she was in pain and he couldn't touch her, the coupling of their brain waves diminished. This matched the findings from a previously published paper from the same experiment which found that heart rate and respiratory synchronisation disappeared when the male study participant couldn't hold her hand to ease her pain.
"It appears that pain totally interrupts this interpersonal synchronisation between couples and touch brings it back," says Goldstein.
Subsequent tests of the male partner's level of empathy revealed that the more empathetic he was to her pain the more their brain activity synced. The more synchronised their brains, the more her pain subsided.
How exactly could coupling of brain activity with an empathetic partner kill pain? More studies are needed to find out, stressed Goldstein. But he and his co-authors offer a few possible explanations. Empathetic touch can make a person feel understood, which in turn – according to previous studies – could activate pain-killing reward mechanisms in the brain. "Interpersonal touch may blur the borders between self and other," the researchers wrote.
The study did not explore whether the same effect would occur with same-sex couples, or what happens in other kinds of relationships. The takeaway for now, Goldstein said: Don't underestimate the power of a hand-hold. "You may express empathy for a partner's pain, but without touch it may not be fully communicated," he said.
The mechanisms underlying analgesia related to social touch are not clear. While recent research highlights the role of the empathy of the observer to pain relief in the target, the contribution of social interaction to analgesia is unknown. The current study examines brain-to-brain coupling during pain with interpersonal touch and tests the involvement of interbrain synchrony in pain alleviation. Romantic partners were assigned the roles of target (pain receiver) and observer (pain observer) under pain–no-pain and touch–no-touch conditions concurrent with EEG recording. Brain-to-brain coupling in alpha–mu band (8–12 Hz) was estimated by a three-step multilevel analysis procedure based on running window circular correlation coefficient and post hoc power of the findings was calculated using simulations. Our findings indicate that hand-holding during pain administration increases brain-to-brain coupling in a network that mainly involves the central regions of the pain target and the right hemisphere of the pain observer. Moreover, brain-to-brain coupling in this network was found to correlate with analgesia magnitude and observer’s empathic accuracy. These findings indicate that brain-to-brain coupling may be involved in touch-related analgesia.
Pavel Goldstein, Irit Weissman-Fogel, Guillaume Dumas, Simone G Shamay-Tsoory