New research reveals that learning in the brain occurs not just when there are external rewards like food or money, but also naturally through the constant ebb and flow of dopamine and acetylcholine. The researchers found that this hormonal balancing act is ongoing and independent of rewards, potentially offering new insights into neuropsychiatric conditions.
The findings could explain how memories form throughout the day.
Scientists have long believed that rewards such as food or money stimulate learning by triggering the release of dopamine, a hormone associated with pleasure and positive reinforcement. However, a recent rodent study suggests that learning can still happen even when there is no immediate reward involved.
Conducted by a team from NYU Grossman School of Medicine, the study examined the interaction between dopamine and acetylcholine, another brain chemical involved in learning and memory. Previous studies indicated that these two hormones have an inverse relationship; an increase in one leads to a decrease in the other. It was previously thought that rewards facilitate learning by simultaneously elevating dopamine levels while reducing acetylcholine.
This sudden hormone imbalance is believed to open a window of opportunity for brain cells to adjust to new circumstances and form memories for later use. Known as neuroplasticity, this process is a major feature of learning as well as recovery after injury. However, the question remained whether food and other external rewards are the only drivers for this memory system, or whether our brains instead are able to create the same conditions that are favorable to learning without outside help.
To provide some clarity, the study authors focused on when and under what circumstances dopamine levels are high at the same time as acetylcholine levels are low. They found that this situation occurs frequently, even in the absence of rewards. In fact, it turns out that the hormones constantly ebb and flow in the brain, with dopamine levels regularly raised while acetylcholine levels are low, setting the stage for continual learning.
“Our findings challenge the current understanding of when and how dopamine and acetylcholine work together in the brain,” said study lead author Anne Krok, PhD. “Rather than creating unique conditions for learning, rewards take advantage of a mechanism that is already in place and is constantly at work,” added Krok, who is also a medical student at NYU Grossman School of Medicine.
For the research, which was recently published in the journal Nature, the study team gave dozens of mice access to a wheel on which they could run or rest at will. On occasion, the researchers offered the animals a drink of water. Then they recorded rodent brain activity and measured the amount of dopamine and acetylcholine released at different moments.
As expected, the drink treats created the typical patterns of dopamine and acetylcholine release that are prompted by rewards. However, the team also observed that well before receiving water treats, dopamine, and acetylcholine already followed “ebb and flow” cycles approximately twice every second, during which the levels of one hormone dipped while the other surged. Krok notes that this pattern continued regardless of whether the rodents were running or standing still. Similar brain waves have been observed in humans during periods of introspection and rest, she adds.
“These results may help explain how the brain learns and rehearses on its own, without the need for external incentives,” said study senior author and neuroscientist Nicolas Tritsch, Ph.D. “Perhaps this pulsing circuit triggers the brain to reflect on past events and to learn from them.”
That said, Tritsch, an assistant professor in the Department of Neuroscience and Physiology at NYU Langone Health, cautions that their research was not designed to tell whether mouse brains process information the same way as human brains do during this “self-driven” learning, as he describes it.
Nevertheless, he says, the results of the study may also offer insight into new ways of understanding neuropsychiatric conditions that have been tied to incorrect levels of dopamine, such as schizophrenia, attention-deficit/hyperactivity disorder (<span class=”glossaryLink” aria-describedby=”tt” data-cmtooltip=”
ADHD
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by an ongoing pattern of excessive amounts of inattention, hyperactivity, carelessness, and impulsivity that are pervasive, impairing, and otherwise age-inappropriate.
” data-gt-translate-attributes=”[“attribute”:”data-cmtooltip”, “format”:”html”]”>ADHD), and depression.
In schizophrenia, for example, patients often experience delusions that contradict reality. If the dopamine-acetylcholine circuit is constantly strengthening connections in the brain, says Tritsch, then problems with this mechanism might lead to the formation of too many, and incorrect, connections, causing them to “learn” of events that did not really occur.
Similarly, lack of motivation is a common symptom of depression, making it challenging to perform basic tasks such as getting out of bed, brushing teeth, or going to work. It is possible that a disruption in the internal-drive system might be contributing to these issues, the authors say.
As a result, Tritsch says the research team next plans to examine how dopamine-acetylcholine cycles behave in animal models of such mental illnesses, as well as during sleep, which is important for memory consolidation.
Reference: “Intrinsic dopamine and acetylcholine dynamics in the striatum of mice” by Anne C. Krok, Marta Maltese, Pratik Mistry, Xiaolei Miao, Yulong Li and Nicolas X. Tritsch, 9 August 2023, Nature. DOI: 10.1038/s41586-023-05995-9
Funding for the study was provided by <span class=”glossaryLink” aria-describedby=”tt” data-cmtooltip=”
National Institutes of Health
The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. Founded in 1887, it is a part of the U.S. Department of Health and Human Services. The NIH conducts its own scientific research through its Intramural Research Program (IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program. With 27 different institutes and centers under its umbrella, the NIH covers a broad spectrum of health-related research, including specific diseases, population health, clinical research, and fundamental biological processes. Its mission is to seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce illness and disability.
” data-gt-translate-attributes=”[“attribute”:”data-cmtooltip”, “format”:”html”]”>National Institutes of Health grants DP2NS105553, R01MH130658, T32NS086750, T32GM007308, and T32GM136573. Further funding was provided by the Alfred P. Sloan Foundation, the Danna Foundation, the Whitehall Foundation, the Feldstein Medical Foundations, and the Vilcek Scholars Award.
In addition to Krok and Tritsch, other investigators involved in the study were Marta Maltese, Ph.D.; Pratik Mistry, MS; at NYU Langone, and Xiaolei Miao, Ph.D.; and Yulong Li, Ph.D., at Peking University School of Life Sciences in Beijing.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
