Neuroscience

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Posts tagged social memory

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Researchers Pinpoint Brain Region Essential for Social Memory Columbia University Medical Center (CUMC) researchers have determined that a small region of the hippocampus known as CA2 is essential for social memory, the ability of an animal to recognize another of the same species. A better grasp of the function of CA2 could prove useful in understanding and treating disorders characterized by altered social behaviors, such as autism, schizophrenia, and bipolar disorder. The findings, made in mice, were published on Feb. 23, 2014, in the online edition of Nature. Scientists have long understood that the hippocampus—a pair of seahorse-shaped structures in the brain’s temporal lobes—plays a critical role in our ability to remember the who, what, where, and when of our daily lives. Recent studies have shown that different subregions of the hippocampus have different functions. For instance, the dentate gyrus is critical for distinguishing between similar environments, while CA3 enables us to recall a memory from partial cues (e.g., Proust’s famous madeleine). The CA1 region is critical for all forms of memory. “However, the role of CA2, a relatively small region of the hippocampus sandwiched between CA3 and CA1, has remained largely unknown,” said senior author Steven A. Siegelbaum, PhD, professor of neuroscience and pharmacology, chair of the Department of Neuroscience, a member of the Mortimer B. Zuckerman Mind Brain Behavior Institute and Kavli Institute for Brain Science, and a Howard Hughes Medical Institute Investigator. A few studies have suggested that CA2 might be involved in social memory, as this region has a high level of expression of a receptor for vasopressin, a hormone linked to sexual motivation, bonding, and other social behaviors. To learn more about this part of the hippocampus, the researchers created a transgenic mouse in which CA2 neurons could be selectively inhibited in adult animals. Once the neurons were inhibited, the mice were given a series of behavioral tests. “The mice looked quite normal until we looked at social memory,” said first author Frederick L. Hitti, an MD-PhD student in Dr. Siegelbaum’s laboratory, who developed the transgenic mouse. “Normally, mice are naturally curious about a mouse they’ve never met; they spend more time investigating an unfamiliar mouse than a familiar one. In our experiment, however, mice with an inactivated CA2 region showed no preference for a novel mouse versus a previously encountered mouse, indicating a lack of social memory.” In two separate novel-object recognition tests, the CA2-deficient mice showed a normal preference for an object they had not previously encountered, showing that the mice did not have a global lack of interest in novelty. In another experiment, the researchers tested whether the animals’ inability to form social memories might have to do with deficits in olfaction (sense of smell), which is crucial for normal social interaction. However, the mice showed no loss in ability to discriminate social or non-social odors. In humans, the importance of the hippocampus for social memory was famously illustrated by the case of Henry Molaison, who had much of his hippocampus removed by surgeons in 1953 in an attempt to cure severe epilepsy. Molaison (often referred to as HM in the scientific literature) was subsequently unable to form new memories of people. Scientists have observed that lesions limited to the hippocampus also impair social memory in both rodents and humans. “Because several neuropsychiatric disorders are associated with altered social behaviors, our findings raise the possibility that CA2 dysfunction may contribute to these behavioral changes,” said Dr. Siegelbaum. This possibility is supported by findings of a decreased number of CA2 inhibitory neurons in individuals with schizophrenia and bipolar disorder and altered vasopressin signaling in autism. Thus, CA2 may provide a new target for therapeutic approaches to the treatment of social disorders.
Researchers Pinpoint Brain Region Essential for Social Memory

Columbia University Medical Center (CUMC) researchers have determined that a small region of the hippocampus known as CA2 is essential for social memory, the ability of an animal to recognize another of the same species. A better grasp of the function of CA2 could prove useful in understanding and treating disorders characterized by altered social behaviors, such as autism, schizophrenia, and bipolar disorder. The findings, made in mice, were published on Feb. 23, 2014, in the online edition of Nature.

Scientists have long understood that the hippocampus—a pair of seahorse-shaped structures in the brain’s temporal lobes—plays a critical role in our ability to remember the who, what, where, and when of our daily lives. Recent studies have shown that different subregions of the hippocampus have different functions. For instance, the dentate gyrus is critical for distinguishing between similar environments, while CA3 enables us to recall a memory from partial cues (e.g., Proust’s famous madeleine). The CA1 region is critical for all forms of memory.

“However, the role of CA2, a relatively small region of the hippocampus sandwiched between CA3 and CA1, has remained largely unknown,” said senior author Steven A. Siegelbaum, PhD, professor of neuroscience and pharmacology, chair of the Department of Neuroscience, a member of the Mortimer B. Zuckerman Mind Brain Behavior Institute and Kavli Institute for Brain Science, and a Howard Hughes Medical Institute Investigator. A few studies have suggested that CA2 might be involved in social memory, as this region has a high level of expression of a receptor for vasopressin, a hormone linked to sexual motivation, bonding, and other social behaviors.

To learn more about this part of the hippocampus, the researchers created a transgenic mouse in which CA2 neurons could be selectively inhibited in adult animals. Once the neurons were inhibited, the mice were given a series of behavioral tests. “The mice looked quite normal until we looked at social memory,” said first author Frederick L. Hitti, an MD-PhD student in Dr. Siegelbaum’s laboratory, who developed the transgenic mouse. “Normally, mice are naturally curious about a mouse they’ve never met; they spend more time investigating an unfamiliar mouse than a familiar one. In our experiment, however, mice with an inactivated CA2 region showed no preference for a novel mouse versus a previously encountered mouse, indicating a lack of social memory.”

In two separate novel-object recognition tests, the CA2-deficient mice showed a normal preference for an object they had not previously encountered, showing that the mice did not have a global lack of interest in novelty. In another experiment, the researchers tested whether the animals’ inability to form social memories might have to do with deficits in olfaction (sense of smell), which is crucial for normal social interaction. However, the mice showed no loss in ability to discriminate social or non-social odors.

In humans, the importance of the hippocampus for social memory was famously illustrated by the case of Henry Molaison, who had much of his hippocampus removed by surgeons in 1953 in an attempt to cure severe epilepsy. Molaison (often referred to as HM in the scientific literature) was subsequently unable to form new memories of people. Scientists have observed that lesions limited to the hippocampus also impair social memory in both rodents and humans.

“Because several neuropsychiatric disorders are associated with altered social behaviors, our findings raise the possibility that CA2 dysfunction may contribute to these behavioral changes,” said Dr. Siegelbaum. This possibility is supported by findings of a decreased number of CA2 inhibitory neurons in individuals with schizophrenia and bipolar disorder and altered vasopressin signaling in autism. Thus, CA2 may provide a new target for therapeutic approaches to the treatment of social disorders.

Filed under hippocampus social memory schizophrenia autism social interaction dentate gyrus psychology neuroscience science

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Dolphins Have Longest Memories in Animal Kingdom Marine mammals can remember their friends after 20 years apart, study says. New experiments show that bottlenose dolphins can remember whistles of other dolphins they’d lived with after 20 years of separation. Each dolphin has a unique whistle that functions like a name, allowing the marine mammals to keep close social bonds. The new research shows that dolphins have the longest memory yet known in any species other than people. Elephants and chimpanzees are thought to have similar abilities, but they haven’t yet been tested, said study author Jason Bruck, an animal behaviorist at the University of Chicago. Bruck came up with the idea to study animal memory when his brother’s dog, usually wary of male strangers, remembered and greeted him four years after last seeing him. “That got me thinking: How long do other animals remember each other?” I Remember You! Bruck studied dolphins because their social bonds are extremely important and because there are good records for captive dolphins (as opposed to wild ones). So he collected data from 43 bottlenose dolphins at six facilities in the U.S. and Bermuda, members of a breeding consortium that has swapped dolphins for decades and kept careful records of each animal’s social partners. He first played recordings of lots of unfamiliar whistles to the dolphins in the study until the subjects got bored and stopped inspecting the underwater speaker making the sounds. At this point, he played the whistles of the listening dolphins’ old friends. When the dolphins heard these familiar whistles, they would perk up and approach the speakers, often whistling their own name and listening for a response. Overall, the dolphins responded more to animals they’d known decades ago than to random animals—suggesting they recognized their former companions, according to the study, published recently in Proceedings of the Royal Society B. Cheeky Dolphins Working with animals as intelligent as dolphins was a challenge, Bruck added. The animals loved participating in the experiment so much that they’d often hover over the speaker, blocking the noise. Others would begin “whistling directly at me as if I could understand them,” he said. And one set of cheeky young dolphins swam up to Bruck and started whistling the names of the dominant males in their group in order of rank, perhaps suggesting the names they wanted to hear, Bruck said. Memory Linked to Smarts? Why dolphins—which live an average of 20 years in the wild—need long-term memory is still unknown. But it may have to do with maintaining relationships, since over time dolphin groups often break up and reorganize into new alliances. This sort of social system is called “fission-fusion,” and it’s also seen in elephants and chimpanzees—two other highly intelligent and social beings. Coincidence? Bruck suspects not: “It seems that maybe complex cognition comes from a place of trying to remember who your buddies are,” he said.

Dolphins Have Longest Memories in Animal Kingdom

Marine mammals can remember their friends after 20 years apart, study says.

New experiments show that bottlenose dolphins can remember whistles of other dolphins they’d lived with after 20 years of separation. Each dolphin has a unique whistle that functions like a name, allowing the marine mammals to keep close social bonds.

The new research shows that dolphins have the longest memory yet known in any species other than people. Elephants and chimpanzees are thought to have similar abilities, but they haven’t yet been tested, said study author Jason Bruck, an animal behaviorist at the University of Chicago.

Bruck came up with the idea to study animal memory when his brother’s dog, usually wary of male strangers, remembered and greeted him four years after last seeing him. “That got me thinking: How long do other animals remember each other?”

I Remember You!

Bruck studied dolphins because their social bonds are extremely important and because there are good records for captive dolphins (as opposed to wild ones).

So he collected data from 43 bottlenose dolphins at six facilities in the U.S. and Bermuda, members of a breeding consortium that has swapped dolphins for decades and kept careful records of each animal’s social partners.

He first played recordings of lots of unfamiliar whistles to the dolphins in the study until the subjects got bored and stopped inspecting the underwater speaker making the sounds.

At this point, he played the whistles of the listening dolphins’ old friends.

When the dolphins heard these familiar whistles, they would perk up and approach the speakers, often whistling their own name and listening for a response.

Overall, the dolphins responded more to animals they’d known decades ago than to random animals—suggesting they recognized their former companions, according to the study, published recently in Proceedings of the Royal Society B.

Cheeky Dolphins

Working with animals as intelligent as dolphins was a challenge, Bruck added. The animals loved participating in the experiment so much that they’d often hover over the speaker, blocking the noise.

Others would begin “whistling directly at me as if I could understand them,” he said.

And one set of cheeky young dolphins swam up to Bruck and started whistling the names of the dominant males in their group in order of rank, perhaps suggesting the names they wanted to hear, Bruck said.

Memory Linked to Smarts?

Why dolphins—which live an average of 20 years in the wild—need long-term memory is still unknown. But it may have to do with maintaining relationships, since over time dolphin groups often break up and reorganize into new alliances.

This sort of social system is called “fission-fusion,” and it’s also seen in elephants and chimpanzees—two other highly intelligent and social beings.

Coincidence? Bruck suspects not: “It seems that maybe complex cognition comes from a place of trying to remember who your buddies are,” he said.

Filed under mammals bottlenose dolphins cognition LTM social memory science

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