Other research has shown that the brains of other animals also store memories differently in their hemispheres. Researchers in the field have called such differences lateralization. In this new effort, the researchers wondered if the same might be true for wood ants. To learn more about how ant brains store memories, the researchers carried out an experiment that involved allowing ant specimens to touch and eat a droplet of sugar as they were shown a cue. Ants use their antennae to touch or smell an object to figure out if it is food.
Thus, to train an ant to expect a treat, the researchers allowed them to touch a sugar droplet with their left antenna, their right antenna, both of them, or neither of them—all while being shown a blue object. The goal was to get the ants to respond to the sight of the blue object the way dogs did in Pavlov's experiments.
Once the ants were trained, the researchers time-tested them on how they responded to seeing the object—at 10 minutes, an hour and then a day later. The researchers found that when an ant was trained using just its right antenna, it demonstrated a strong response at 10 minutes, a weaker response after that, and no response for longer times. In sharp contrast, those ants that were trained using the left antenna showed no response at 10 minutes, or even after an hour.
But the next day they had a strong response. The researchers suggest this is solid evidence for short-term memory being stored in the right hemisphere and long-term memory in the left hemisphere. Explore further.
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This is particularly important because strong emotional memories e. The amygdala doesn't just modify the strength and emotional content of memories; it also plays a key role in forming new memories specifically related to fear. Fearful memories are able to be formed after only a few repetitions. Understanding how the amygdala processes fear is important because of its relevance to post-traumatic stress disorder PTSD , which affects many of our veterans as well as police, paramedics and others exposed to trauma.
Anxiety in learning situations is also likely to involve the amygdala, and may lead to avoidance of particularly challenging or stressful tasks. QBI researchers including Professor Pankaj Sah and Dr Timothy Bredy believe that understanding how fear memories are formed in the amygdala may help in treating conditions such as post-traumatic stress disorder. There are two areas of the brain involved in implicit memory : the basal ganglia and the cerebellum. The basal ganglia are structures lying deep within the brain and are involved in a wide range of processes such as emotion, reward processing, habit formation, movement and learning.
They are particularly involved in co-ordinating sequences of motor activity, as would be needed when playing a musical instrument, dancing or playing basketball. The cerebellum, a separate structure located at the rear base of the brain, is most important in fine motor control, the type that allows us to use chopsticks or press that piano key a fraction more softly.
A well-studied example of cerebellar motor learning is the vestibulo-ocular reflex, which lets us maintain our gaze on a location as we rotate our heads. The prefrontal cortex PFC is the part of the neocortex that sits at the very front of the brain.
The hippocampus is associated with declarative and episodic memory as well as recognition memory. The cerebellum plays a role in processing procedural memories, such as how to play the piano. The prefrontal cortex appears to be involved in remembering semantic tasks.
The main job of the amygdala is to regulate emotions, such as fear and aggression [link]. The amygdala plays a part in how memories are stored because storage is influenced by stress hormones. For example, one researcher experimented with rats and the fear response Josselyn, Using Pavlovian conditioning, a neutral tone was paired with a foot shock to the rats.
This produced a fear memory in the rats. After being conditioned, each time they heard the tone, they would freeze a defense response in rats , indicating a memory for the impending shock. Then the researchers induced cell death in neurons in the lateral amygdala, which is the specific area of the brain responsible for fear memories. They found the fear memory faded became extinct.
Because of its role in processing emotional information, the amygdala is also involved in memory consolidation: the process of transferring new learning into long-term memory. The amygdala seems to facilitate encoding memories at a deeper level when the event is emotionally arousing. A Laser Beam. Find out why their work caused a media frenzy once it was published in Science.
Another group of researchers also experimented with rats to learn how the hippocampus functions in memory processing [link]. They created lesions in the hippocampi of the rats, and found that the rats demonstrated memory impairment on various tasks, such as object recognition and maze running.
Another job of the hippocampus is to project information to cortical regions that give memories meaning and connect them with other connected memories. It also plays a part in memory consolidation: the process of transferring new learning into long-term memory. Injury to this area leaves us unable to process new declarative memories.
One famous patient, known for years only as H. Then, they could use light to artificially reactivate these memory cells at different times and see if that reactivation provoked a behavioral response from the mice freezing in place. The researchers could also determine which memory cells were active when the mice were placed in the chamber where the fear conditioning occurred, prompting them to naturally recall the memory. Just one day after the fear-conditioning event, the researchers found that memories of the event were being stored in engram cells in both the hippocampus and the prefrontal cortex.
The memory is already there. Over the next two weeks, the silent memory cells in the prefrontal cortex gradually matured, as reflected by changes in their anatomy and physiological activity, until the cells became necessary for the animals to naturally recall the event. By the end of the same period, the hippocampal engram cells became silent and were no longer needed for natural recall. However, traces of the memory remained: Reactivating those cells with light still prompted the animals to freeze.
In the basolateral amygdala, once memories were formed, the engram cells remained unchanged throughout the course of the experiment. Those cells, which are necessary to evoke the emotions linked with particular memories, communicate with engram cells in both the hippocampus and the prefrontal cortex.
The findings suggest that traditional theories of consolidation may not be accurate, because memories are formed rapidly and simultaneously in the prefrontal cortex and the hippocampus on the day of training. Further studies are needed to determine whether memories fade completely from hippocampal cells or if some traces remain. Right now, the researchers can only monitor engram cells for about two weeks, but they are working on adapting their technology to work for a longer period.
Kitamura says he believes that some trace of memory may stay in the hippocampus indefinitely, storing details that are retrieved only occasionally. The researchers also plan to further investigate how the prefrontal cortex engram maturation process occurs.
This study already showed that communication between the prefrontal cortex and the hippocampus is critical, because blocking the circuit connecting those two regions prevented the cortical memory cells from maturing properly.
Simon Makin of Scientific American writes that MIT researchers have discovered the brain uses a complimentary memory system that simultaneously creates and stores both long and short-term memories. Susumu Tonegawa.
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