How the brain can stop action on a dime

Researchers identify neurons that can abruptly halt a planned behavior

Date:
September 17, 2015
Source:
Johns Hopkins University
Summary:
Scientists have identified the precise nerve cells that allow the brain to make a split-second change of course, like jamming on the brakes.

Johns Hopkins University researchers, working with scientists at the National Institute on Aging, have revealed the precise nerve cells that allow the brain to make this type of split-second change of course. In the latest issue of the journal Nature Neuroscience, the team shows that these feats of self-control happen when neurons in the basal forebrain are silenced.

“The study discovered a new role for basal forebrain neurons in the control of action,” said Michela Gallagher, the Krieger-Eisenhower Professor of Psychology and Neuroscience at Johns Hopkins. “This work opens the door to novel approaches focused on this circuit in certain neurological and psychiatric conditions that affect basic cognitive functions of the brain.”

The ability to rapidly stop a behavior is critical for everyday functioning — allowing people crossing the street to freeze if a car surprises them, to not reach for their phone when it vibrates in their pocket during a meeting or, in the case of a batter, to stop from swinging at a bad pitch. A better understanding of the cognitive mechanics behind what’s known as reactive inhibition could help people suffering from neurological conditions where such control is diminished — everything from Alzheimer’s disease and Parkinson’s disease to attention deficit hyperactivity disorder and normal aging.

Scientists had assumed the ability to stop a planned behavior occurred in the basal ganglia, an area in the brain responsible for a variety of motor control functions including the ability to start an action or a behavior. This study demonstrates, however, that the stop response happens in the basal forebrain, a part of the brain best known for regulating sleep, but also recognized as a site for early neurodegeneration in Alzheimer’s disease.

The researchers trained rats to play a game: If the rats quickly moved after hearing a tone, they got a treat. The rats were also rewarded if they stopped moving when a light flashed. All the while, the team monitored the rats for electrical signals in the basal forebrain.

The researchers trained rats to move quickly to get a treat. After hearing a tone, the rats would rush into a new port to lick sucrose water. But, when the tone was followed by a flash of light, the rats would have to immediately stay in place to get a treat. In other words, when the light flashed, the rule of reward reversed — instead of moving quickly to get reward, the rats had to cancel that planned response and stay still to get their treat.

While the rats performed the tasks, the team monitored the activity of individual basal forebrain neurons. The researchers were also able to get the rats to stop without using the flash of light by stimulating the same neurons with a small pulse of electricity.

“In the lab, we were able to manipulate these neurons, which caused rats to stop their behavior even though they had no reason to do so,” said lead author Jeffrey D. Mayse, who conducted the research as a Johns Hopkins doctoral student and is now a postdoctoral fellow at Brown University.

“Understanding how these cells are involved in this form of self-control expands our knowledge of the normal brain circuits involved in everyday decision-making,” he said, “and will be absolutely critical to developing future treatments and therapies for diseases and disorders with impaired reactive inhibition as a symptom.”


Story Source:

The above post is reprinted from materials provided by Johns Hopkins University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jeffrey D Mayse, Geoffrey M Nelson, Irene Avila, Michela Gallagher, Shih-Chieh Lin. Basal forebrain neuronal inhibition enables rapid behavioral stopping. Nature Neuroscience, 2015; DOI: 10.1038/nn.4110
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Do estrogen levels affect the willingness to share?

Date:September 17, 2015

Source:Goethe-Universität Frankfurt am Main

Summary:Fluctuating hormone levels change a woman’s social behaviour over the course of the menstrual cycle. Mood swings and irritability before the period as well as a greater interest in sex during ovulation are well known. Now psychologists have discovered that the willingness to share one’s own resources with strangers also fluctuates with hormone levels. Women exhibit a higher willingness to cooperate during and shortly after menstruation — this is the result of two online studies involving over 400 German and US American women.

To qualify for the study, the participants had to have a natural menstrual cycle, in other words not be using hormone-based contraceptives, had to not be pregnant and not have entered menopause yet. The researchers compared the willingness to cooperate between women in the time during and shortly after menstruation (early follicular phase), when the levels of the hormones estrogen and progesterone are low, and a few days after ovulation (midluteal phase), when the estrogen and progesterone levels are especially high. The hormone levels were estimated based on the self-reported day in the cycle.

The researchers measured the subjects’ individual willingness to cooperate using a well-established psychological scale, the “Social Value Orientation.” To do so, they asked the women to divide fictitious money between themselves and another person who was a complete stranger to them.

“Numerous studies have shown that people who exhibit a high willingness to share in this test also donate money more often and in larger amounts in real life, take the train instead of the car to work more often and are more willing to compromise in negotiations than people with a less pronounced pro-social value orientation,” Christine Anderl, lead author of the study, explains.

The two studies showed that the women were significantly more inclined to share their own resources with a stranger during and shortly after menstruation than they were a few days after ovulation.

The greater the cycle-dependent level of the “female” sex hormone estrogen, the lower the willingness to share of the women on a purely statistical basis. “While we are firmly convinced that the variation in the willingness to share over the course of the cycle is a real and systematic effect, we still have to determine whether or not it is really caused by estrogen as the present data suggest,” Christine Anderl tells us.

“This matches the findings of other research groups, who were able to show that hormones such as oxytocin and the “male” sex hormone testosterone affect the willingness to cooperate in humans,” Prof. Sabine Windmann from the Institute for Experimental Psychology 2 at the Goethe University commented. How strongly the cycle-dependent fluctuations in the willingness to cooperate affect the day-to-day life of women and which areas of life are particularly affected by this will have to be researched in further studies.

However, the researchers have already found initial evidence which suggests that the described effects also occur when the subjects are using real money. These results are also interesting in light of hormonal contraception. Little is currently known about how synthetic hormones act on the receptors in the brain and what effect they have on the behaviour of women.


Story Source:

The above post is reprinted from materials provided by Goethe-Universität Frankfurt am Main. Note: Materials may be edited for content and length.


Journal Reference:

  1. Anderl, C., Hahn, T., Notebaert, K., Klotz, C., Rutter, B., & Windmann, S. Cooperative preferences fluctuate across the menstrual cycle. Judgment and Decision Making, Vol. 10, No. 5, September 2015, pp. 400-406