The Neurobiology of the “Love Hormone” Revealed

Neuroscientists link oxytocin to both love and autism-spectrum disorder.

Posted Aug 05, 2013

In a new study, researchers at New York University Langone Medical Center have discovered a link between the “love hormone” oxytocin and autism-spectrum disorder (ASD). It turns out that our ability to focus and pick up on social cues is directly linked to oxytocin’s ability to promote social and parental bonding. On the flip side, a lack of oxytocin is now linked to the social disconnection created by ASD.

The NYU study titled “Oxytocin Enhances Hippocampal Spike Transmission by Modulating Fast-Spiking Interneurons” was released August 4, 2013 in the online journal of Nature. Dr. Tsien and his Stanford graduate student Scott Owen collaborated with Gord Fishell, PhD, the Julius Raynes Professor of Neuroscience and Physiology at NYU Langone Medical Center, and NYU graduate student Sebnem Tuncdemir for this study.

As a neurohormone, oxytocin not only reduces background noise, it also allows people to pick up on important interpersonal signals. These findings are relevant to how we create intimate bonds and helps unravel the neurobiology behind the social disconnection created by autism, which affects 1 in 88 American children. Brain imaging of people with ASD shows that a lower level of oxytocin impairs even the most rudimentary transmission of sensory signals.

“Oxytocin has a remarkable effect on the passage of information through the brain,” says Richard W. Tsien, the Druckenmiller Professor of Neuroscience and director of the Neuroscience Institute at NYU Langone Medical Center. “It not only quiets background activity, but also increases the accuracy of stimulated impulse firing. Our experiments show how the activity of brain circuits can be sharpened, and hint at how this re-tuning of brain circuits might go awry in conditions like autism.”

People of all ages who are living with ASD struggle to interpret the emotions of others and are easily distracted by overstimulation created by the sensory inputs of their environment. In previous studies lower levels of oxytocin have been found in people with ASD. The Langone researchers hypothesize that mutations in the oxytocin receptor gene may be at the root of a predisposition for autism.

The Oxytocin/GABA Connection

The current NYU study expands on a Swiss study from 30 years ago which found that oxytocin acted in the hippocampus, a region of the brain involved in memory and cognition. Back in the 80s researchers in Geneva found that oxytocin stimulated nerve cells – called inhibitory interneurons – to trigger the release a neurochemical called GABA. As a neurotransmitter, GABA is an ‘anti-anxiety’ molecule because it dampens the activity of the adjoining excitatory nerve cells, known as pyramidal cells.

The NYU researchers found that continually activating the fast-spiking inhibitory neurons – which are necessary for reducing background noise – causes GABA-releasing synapses to fatigue. Accordingly, when a stimulus arrives, the tired synapses release less GABA and excitation of the pyramidal neuron is not dampened as much, so that excitation drives the pyramidal neuron’s firing more reliably.

The researchers were perplexed to discover that oxytocin was selective in how it stimulated brain spikes and one's ability to focus on specific social and environmental cues. Dr. Tsien explains, “From the previous findings, we predicted that oxytocin would dampen brain circuits in all ways, quieting both background noise and wanted signals. Instead, we found that oxytocin increased the reliability of stimulated impulses – good for brain function, but quite unexpected.” To find the answer to this riddle, the researchers honed in on a particular type of “fast-spiking” inhibitory interneurons which are responsible for the finely tuned effects of oxytocin. The mystery of how oxytocin drives these fast-spiking inhibitory cells to fire, yet also increases signaling to pyramidal neurons, was solved through studies with rodent models.

In a previous Psychology Today blog titled “The Neurochemicals of Happiness” I wrote about how 7 neurochemicals – including oxytocin and GABA – are linked to social connectedness, lower anxiety, and well-being. Please check out that blog if you’d like to learn more about the function of oxytocin and GABA. For more on brain-spikes check out my blog: “Brain Waves Create Archives of Experience and Expectation”.

Conclusion: Oxytocin Let’s You Zoom In on Love and Block Out Distractions

A healthy dose of oxytocin allows you to zoom in on love and block out distractions. It appears that the social isolation created by autism may be deeply rooted in a genetic disposition to produce less oxytocin. Hopefully these findings will lead to new treatments for ASD and help people with autism be able to create stronger human bonds, improve focus, and block out background noise by recalibrating oxytocin levels.

Dr. Fishell concludes, “The stronger signal and muffled background noise arise from the same fundamental action of oxytocin and give two benefits for the price of one. It’s too early to say how the lack of oxytocin signaling is involved in the wide diversity of autism-spectrum disorders, and the jury is still out about its possible therapeutic effects. But it is encouraging to find that a naturally occurring neurohormone can enhance brain circuits by dialing up wanted signals while quieting background noise."

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