Reach for the hand of a loved one in pain
and not only will your breathing and heart rate synchronize with theirs,
your brain wave patterns will couple up too, according to a new study.
The study, by researchers with CU Boulder and University of Haifa, in
collaboration with the Institut Pasteur published in the journal
Proceedings of the National Academy of Sciences (PNAS) this week, 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 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 synchronization," in which people
physiologically mirror the people they are with. It is the first to look
at brain wave synchronization 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
synchronization disappeared when the male study participant couldn't
hold her hand to ease her pain. "It appears that pain totally interrupts
this interpersonal synchronization 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 synchronized 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.
In an article in 2010, Guillaume Dumas, a research associate at the
Institut Pasteur in the Human Genetics and Cognitive Functions Unit, had
already demonstrated synchronization of brain activity during our
social interaction with others, particularly in terms of alpha-mu
rhythm. This involved using the technique of hyperscanning, which
consists of recording several brains simultaneously. He adds: "We are
very excited about this study because it demonstrates how hyperscanning
combined with the right experimental protocol can provide insight into
the link between our biological anchorage and our sociality."
Guillaume Dumas, researcher at the Institut Pasteur in the Human
Genetics and Cognitive Functions Unit, had already demonstrated in an
article in 2010 that brain activities synchronize during our social
interactions, particularly in terms of alpha-mu rhythm. For that, he had
used this technique of hyperscanning, which consists of recording
several brains simultaneously. He completes: "We are very excited about
this study because it demonstrates how hyperscanning combined with the
right experimental protocol can provide insight into the link between
our biological anchorage and our sociality."
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, Pavel 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 study was supported with a grant from the Binational Science Foundation.