Nav: Home

Serotonin promotes perseverance

March 08, 2018

What happens when serotonin levels increase in human brain? How does this affect our behavior? This is a question that highly interests neuroscientists: serotonin has multiple functions in the brain and understanding what it actually does is a huge task. Not the least because serotonin is at the root of a whole class of antidepressant drugs, the most well-known of which being Prozac, that apparently work by increasing serotonin levels in the human brain.

Previous results suggested that increased serotonin levels make animals (including people) more willing to wait longer for a reward to arrive - in other words, that it makes them more patient. This was compatible with the idea, accepted by many, that serotonin generally acts by inhibiting behavior, because in many cases patience requires postponing doing something.

But now this idea has been challenged by an international team, led by neuroscientists from the Champalimaud Centre for the Unknown (CCU), in Lisbon, Portugal. Their results have been published today in the journal Nature Communications.

The new study shows that serotonin promotes more than just passive waiting - more than simple patience. It enhances active persistence in a task, even in the face of uncertain reward.

Persistence means actively following through on a task, even if unpleasant, like completing your homework, whereas many forms of patience simply require sitting tight and doing nothing.

It so happens that the tasks used in the previous studies did not allow their authors to distinguish between patience and persistence. But in the new work, Eran Lottem, the first author of the paper, and his colleagues developed a task that is actually very similar to the natural situation animals face when foraging for food.

"We had some hints suggesting that the inhibitory effect of serotonin was not general. Some behaviors were unaffected by serotonin", says Lottem. "But we had never seen an active behavior promoted by serotonin. This is, to my knowledge, the first time such a behavior has been observed when serotonin-producing neurons are activated."

The task consisted in giving the mice the choice between two drinking sites placed at each end of a long rectangular box. At any given time, only one drinking site was ready to release water, so the mice had to roam back and forth between the two sides of the box to find the water, and to get it, they had to give a poke with their nose at the drinking site.

Sneakily, to mimic the unpredictability of real world situations, the experimenters arranged that even an active drinking site did not always deliver water, so they would have learn to tolerate some unsuccessful pokes. This provided the scientists with a way to measure the persistence of the animals: they could count the number of pokes they were willing to give in order to try to get water at a "dry" site (one that had ceased giving water).

Once the task was in place, the scientists used a technology known as optogenetics to stimulate the serotonin-producing neurons using pulses of laser light delivered by an implanted optic fiber to the animals' brains.

"What we saw was that when those neurons were stimulated, the animals were willing to poke longer even when they were not getting water, says Lottem. Therefore, serotonin was not inhibiting their behavior because, in that case, the mice would have given up sooner." In other words, he concludes, "the activation of serotonin neurons promotes active persistence rather than mere patience".

Zachary Mainen, the lead author of this study, suggests that the results may ultimately help us to understand better how to treat depression, a disorder in which serotonin is implicated. "The difference between patience and persistence may sound subtle, but the implication is not: it could be the difference between quietly sitting in bed while the world goes by and jumping out of bed each day to greet it".
-end-


Champalimaud Centre for the Unknown

Related Neurons Articles:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.
Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.
A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.
Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.
Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.
Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.
The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.
Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.
How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.
A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.
More Neurons News and Neurons Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.