New research conducted at the University of Haifa has found that emotions are not only the products of information processing in the brain, as was thought until now. It turns out that emotions directly impact the formation of memory in the brain.
The researchers used rats in order to show that emotions that accompany a first encounter affect the way in which information is received and the manner in which social memory is formed. The research was carried out by Dr. Shlomo Wagner from the Neurobiology Department at the university, together with research student Alex Tandler. Their work provides a scientific correlation to the saying that ‘there’s no second chance to form a first impression,’ by showing a link between emotions and cognitive processes such as learning and memory.
The main objective of the study, the results of which were just published in the journal eLife, was to identify brain electrical activity associated with the formation of social memory. The first step was to study brain activity during a first encounter with another rat, in brain areas known to be associated with the formation of social memory. To their surprise, the researchers saw that the first encounter is accompanied by particularly intense neuronal activity, expressed as rapid brain waves at a rate of eight cycles per second. This activity gradually diminished upon subsequent encounters.
In addition, the researchers determined that during that first encounter, the brainwaves were well coordinated between different areas, in contrast to later encounters. “At the first meeting, brainwaves in all parts of the relevant network were highly synchronized and very intense. As the rats got better acquainted the intensity and synchronization throughout the network diminished,” relates Wagner, adding that high levels of synchronization of these waves, labeled theta waves, is known to be conducive to the formation of strong memories in other parts of the brain.
Subsequently, the researchers compared initial social encounters with encounters with inert objects for the first time. The experiment showed that even though the rats showed great interest in these objects, their brain function did not show the same specific synchronization that was elicited by a first meeting with another rat. In addition, the researchers found that the intense responses they measured during the initial encounter continued well after it was over, suggesting that the first encounter switches the brain to a specific socially-associated emotional state, in which it operates in an atypical manner. “This can explain why people tend to particularly remember their first meeting with a friend or future spouse,” explains Wagner.
As soon as the researchers established a link between social sensitization and social memory, they set out to investigate whether other emotions could similarly affect the same network in the brain. When they exposed rats to a negative emotion such as fear, they found that the brain responds differently. Here, too, there was strong rhythmic activity and coordination between brain areas associated with memory, but the rhythm was slower (4-6 cycles per second). The pattern of inter-regional coordination was also different than that measured during the social encounter.
“It seems that when the emotion is a positive social one, the brain guides different regions to function according to a different protocol than that which functions with other emotions, such as fear,” explains Wagner, adding: “In future work we’ll have to sort out the precise implications of different emotions on memory. This might include work with humans. The overall significance of this work is that different emotions apparently make the brain work differently in terms of cognitive processes such as learning and memory.”