A groundbreaking new study at the University of Haifa has found for the first time that emotions are not only the product of the processing of information by the brain, but that they also directly influence processes of learning and memory in the brain. Dr. Shlomo Wagner of the Sagol Department of Neurobiology at the University of Haifa, who undertook the study, explains: “It turns out that different emotions cause the brain to work differently and on distinct frequencies.”
The main goal of the new study, which was published this February in the prestigious science journal eLife, was to identify the electrical activity that takes place in the brain during the formation of social memory. During the course of their work, the researchers – Dr. Wagner and Ph.D. Alex Tendler – discovered the scientific explanation behind the saying “you never get a second chance to make a first impression.” More importantly, they came to understand the connection between emotions and cognitive processes such as learning and memory.
In the first part of the study the researchers examined the electrical activity in the brains of rats during social behavior. They discovered strong rhythmical activity reflecting a state of excitement in the animal. To their surprise, this activity was particularly strong and synchronous between areas of the brain associated with social memory during the first encounter between two previously unfamiliar rats. This rhythmical brain activity declined in strength and in the level of coordination between different brain areas as the encounter between the two rats was repeated.
“In other words, during the first encounter between the two animals, the distinct brain areas worked intensively and at a high level of coordination. It’s almost as though the brain was working under a specific communication protocol coordinating different areas and telling them precisely when to operate. As the two animals got to know each other, the rhythmical activity declined in strength and the coordination between the different parts of the network trailed off,” Dr. Wagner noted.
The researchers compared the brain activity during this social behavior with the activity sparked by non-emotional stimuli, such as an encounter with an inanimate object. Although on the behavioral level the rats also showed a high level of interest in such stimuli, their brain patterns did not show the same exceptional level of coordinated rhythmical activity seen in the encounter with an unfamiliar rat. The researchers also found that once a true social encounter occurs, the brain continued to work at a high level of coordination for some time, even after the encounter had ended. In other words, the brain entered a state of social arousal.
“The findings clearly showed that the excitement of the social encounter with a stranger rat created the high level of synchronized rhythmic activity in the brain, and it was this factor that seems to facilitate the formation of social memory. In other words, we found a connection between the feeling of excitement, rhythmical activity in specific brain areas, and the cognitive process of memory formation. Once the rats were familiar with each other, they were much less excited, and accordingly the distinct areas of their brain worked in much less coordination,” Dr. Wagner explained. “In essence, this finding explains why people tend to remember in particular their first encounter with a future friend or partner.”
Having found the connection between social excitement and social memory, the researchers then sought to examine whether a different emotion would also influence the same network of brain areas in the same way. Conventional wisdom would suggest that this should be the case. Dr. Wagner explains that the usual approach did not see any connection between specific emotions and cognitive processes such as memory, so that the brain should have acted in a similar manner in the case of a different emotion.
The researchers duly exposed the rats to a different emotion – a negative one associated with exposure to a frightening stimulant. It emerged that the brain works differently in this instance. Once again, strong rhythmical activity and coordination between the different areas associated with social memory was seen. However, this took place on a different frequency and at a slower rhythmical pattern.
“It seems that when the emotion is social and positive, the brain tells the different areas to work according to one communication protocol. When a different emotion is involved, such a negative emotion of fear as in our experiment, the brain tells the same areas to use a different communication protocol. We will need to conduct additional studies, including studies on humans, in the future in order to understand the precise ramifications of each emotion on memory. But in broad terms,” Dr. Wagner concludes, “the implication is clear. Different emotions cause the brain to work differently, including in terms of cognitive processes such as learning and memory.”
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Source:University of Haifa Image Credit: The image is credited to OpenStax College and is licensed CC BY 3.0 Original Research: Full open access research for “Different types of theta rhythmicity are induced by social and fearful stimuli in a network associated with social memory” by Alex Tendler, Shlomo Wagner in eLife. Published online February 16 2015 doi:10.7554/eLife.03614
Different types of theta rhythmicity are induced by social and fearful stimuli in a network associated with social memory
Rhythmic activity in the theta range is thought to promote neuronal communication between brain regions. In this study, we performed chronic telemetric recordings in socially behaving rats to monitor electrophysiological activity in limbic brain regions linked to social behavior. Social encounters were associated with increased rhythmicity in the high theta range (7–10 Hz) that was proportional to the stimulus degree of novelty. This modulation of theta rhythmicity, which was specific for social stimuli, appeared to reflect a brain-state of social arousal. In contrast, the same network responded to a fearful stimulus by enhancement of rhythmicity in the low theta range (3–7 Hz). Moreover, theta rhythmicity showed different pattern of coherence between the distinct brain regions in response to social and fearful stimuli. We suggest that the two types of stimuli induce distinct arousal states that elicit different patterns of theta rhythmicity, which cause the same brain areas to communicate in different modes.
“Different types of theta rhythmicity are induced by social and fearful stimuli in a network associated with social memory” by Alex Tendler, Shlomo Wagner in eLife. Published online February 16 2015 doi:10.7554/eLife.03614