A Collection of Notes about the Components of SWMM 4 and 5
Unexpected Outcomes Key to Human Learning
'The Unexpected Outcome' Is A Key To Human Learning
ScienceDaily (Mar. 15, 2009) — The human brain’s sensitivity to unexpected outcomes plays a fundamental role in the ability to adapt and learn new behaviors, according to a new study by a team of psychologists and neuroscientists from the University of Pennsylvania.
Using a computer-based card game and microelectrodes to observe neuronal activity of the brain, the Penn study, published March 13 in the journal Science, suggests that neurons in the human substantia nigra, or SN, play a central role in reward-based learning, modulating learning based on the discrepancy between the expected and the realized outcome.
“This is the first study to directly record neural activity underlying this learning process in humans, confirming the hypothesized role of the basal ganglia, which includes the SN, in models of reinforcement including learning, addiction and other disorders involving reward-seeking behavior,” said lead author Kareem Zaghloul, postdoctoral fellow in neurosurgery at Penn’s School off Medicine. “By responding to unexpected financial rewards, these cells encode information that seems to help participants maximize reward in the probabilistic learning task.”
Learning, previously studied in animal models, seems to occur when dopaminergic neurons, which drive a larger basal ganglia circuit, are activated in response to unexpected rewards and depressed after the unexpected omission of reward. Put simply, a lucky win seems to be retained better than a probable loss.
Similar to an economic theory, where efficient markets respond to unexpected events and expected events have no effect, we found that the dopaminergic system of the human brain seems to be wired in a similar rational manner -- tuned to learn whenever anything unexpected happens but not when things are predictable," said Michael J. Kahana, senior author and professor of psychology at Penn’s School of Arts and Sciences.
Zaghloul worked with Kahana and Gordon Baltuch, associate professor of neurosurgery, in a unique collaboration among departments of psychology, neurosurgery and bioengineering. They used microelectrode recordings obtained during deep brain stimulation surgery of Parkinson’s patients to study neuronal activity in the SN, the midbrain structure that plays an important role in movement, as well as reward and addiction. Patients with Parkinson’s disease show impaired learning from both positive and negative feedback in cognitive tasks due to the degenerative nature of their disease and the decreased number of dopaminergic neurons.
The recordings were analyzed to determine whether responses were affected by reward expectation. Participants were asked to choose between red and blue decks of cards presented on a computer screen, one of which carried a higher probability of yielding a financial reward than the other. If the draw of a card yielded a reward, a stack of gold coins was displayed along with an audible ring of a cash register and a counter showing accumulated virtual earnings. If the draw did not yield a reward or if no choice was made, the screen turned blank and participants heard a buzz.
“This new way to measure dopaminergic neuron activity has helped us gain a greater understanding of fundamental cognitive activity," said Baltuch, director of the Penn Medicine Center for Functional and Restorative Neurosurgery.
The work is supported by grants from the National Institutes of Health, the Conte Center and the Dana Foundation.
Journal reference:
- Kareem A. Zaghloul, Justin A. Blanco, Christoph T. Weidemann, Kathryn McGill, Jurg L. Jaggi, Gordon H. Baltuch, and Michael J. Kahana. Human Substantia Nigra Neurons Encode Unexpected Financial Rewards. Science, 2009; 323 (5920): 1496 DOI: 10.1126/science.1167342
MLA
Tiny Brain Region Key To Fear Of Rivals And Predators
ScienceDaily (Mar. 15, 2009) — Mice lose their fear of territorial rivals when a tiny piece of their brain is neutralized, a new study reports.
The study adds to evidence that primal fear responses do not depend on the amygdala – long a favored region of fear researchers – but on an obscure corner of the primeval brain.
A group of neuroscientists led by Larry Swanson of the University of Southern California studied the brain activity of rats and mice exposed to cats, or to rival rodents defending their territory.
Both experiences activated neurons in the dorsal premammillary nucleus, part of an ancient brain region called the hypothalamus.
Swanson's group then made tiny lesions in the same area. Those rodents behaved far differently.
"These animals are not afraid of a predator," Swanson said. "It's almost like they go up and shake hands with a predator."
Lost fear of cats in rodents with such lesions has been observed before. More important for studies of social interaction, the study replicated the finding for male rats that wandered into another male's territory.
Instead of adopting the usual passive pose, the intruder frequently stood upright and boxed with the resident male, avoided exposing his neck and back, and came back for more even when losing.
"It's amazing that these lesions appear to abolish innate fear responses," said Swanson, who added: "The same basic circuitry is found in primates and people that we find in rats and mice."
The study was slated for online publication the week of March 9 in Proceedings of the National Academy of Sciences.
Swanson predicted that his group's findings would shift some research away from the amygdala, a major target of fear studies for the past 30 years.
"This is a new perspective on what part of the brain controls fear," he said.
He explained that most amygdala studies have focused on a different type of fear, which might more accurately be called caution or risk aversion.
In those studies, animals receive an electric shock to their feet. When placed in the same environment a few days later, they display caution and increased activity of the amygdala.
But the emotion experienced in that case may differ from the response to a physical attack.
"We're not just dealing with one system that controls all fear," Swanson said.
Swanson and collaborators have been studying the role of the hypothalamus in the fear response since 1992.
Because of its role in basic survival functions such as feeding, reproduction and the sleep-wake cycle, the hypothalamus seems a plausible candidate for fear studies.
Yet, said Swanson, "nobody's paid any attention to it."
The PNAS study is the most recent of several by Swanson on fear and the hypothalamus. The few other researchers in the area include Newton Canteras of the University of Sao Paulo in Brazil, who collaborated with Swanson on the PNAS study, as well as Robert and Caroline Blanchard of the University of Hawaii.
The other authors on the PNAS study were Simone Motta, Marina Goto, Flavia Gouveia and Marcus Baldo, all from the University of Sao Paulo.
The Brazilian government funded the study.
Journal reference:
- Simone C. Motta, Marina Goto, Flavia V. Gouveia, Marcus V. C. Baldo, Newton S. Canteras, and Larry W. Swanson. Dissecting the brain's fear system reveals the hypothalamus is critical for responding in subordinate conspecific intruders. Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0900939106
MLA
Last updated by Robert Dickinson Mar 15.
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