Past experiences can shift your perception of future events

 

Memories of the past may help us to learn new things in the future by altering how we perceive future events

Photo credit: WIKIMEDIA COMMONS

Our past events are more than just memories it shapes us and our view of the world that we live in. When we enter a new environment, we tend to associate it with things that we know from our past to learn and adapt quickly.

According to a new study, memories of past events can help the brain learn new things much faster and more efficiently than it would take normally. In this new research, scientists have found that past memories that are essentially positive can force the brain to form new memories in the future similar to it. They found the exact neurological mechanism for this by studying a snail's response to various stimuli.

Lymnaea Mollusca is a pond snail that has a brain with roughly 20,000 neurons which is in contrast to humans, who have more than 86 billion neurons. The reason for choosing Lymnaea is not only does it have a brain that has a smaller number of neurons, but each of its neurons is far larger and more accessible than that of the human brain or any other mammal.

Long-term memory formation is more energetically expensive than short-term memory. It requires the activation of special neurological pathways with lasting synaptic connections which requires the release of a large number of special molecules (neurotransmitters).  Lymnaea on the other hand has a very strict energy budget hence any long-term memory formation needs to be worth it. How does the snail know what memories are worth remembering and therefore leads to formation of long-term memories?

Facilitatory learning

To find exactly what changes the snail’s perception to new memories that help it to remember, the scientists gave it two kinds of stimuli. The first stimulus was a ‘conditioned stimuli, where a relatively indifferent substance was fed to the snail such as the banana-flavored water which it found to be energetically indifferent. Then the scientist gave a second stimulus an ‘unconditioned stimulus’, where a sugar solution was given to the snail which was energetically rich and they fed actively. This is known as strong training which seems to shift the snail's perception of new stimuli in the future. This they proved by demonstrating that in the experiments just the presence of unconditioned stimulus is enough for the snail to ‘anticipate’ the energy-rich unconditioned stimulus.

The scientists also devised another training method, weakening the unconditioned stimulus by diluting the sugar solution to check whether it could induce changes in the snail's perception. They found that weak training could not induce changes in the snail's perceptions leading to the conclusion that a strong long-lasting memory was needed to make the snail more accepting of new memory formation and therefore learning.

Do perceptions really change?

How do find how the snails perceive the conditioned training and thereby towards training? For this, the scientist found a really interesting solution. During general feeding, the snails had a peculiar way of taking up the substance especially when they perceived the substance to be neutral (conditioned stimulus). The snails were found to be taking in some of the substance and rejecting some of the substance by ingestion and egestion bites.

Snails that didn’t have any prior exposure to the substances that is without any training were often observed to be flip-flopping between these two feeding behaviors. But the snails that had strong training that is the ones that were exposed to the conditioned stimulus and strong unconditioned stimulus were found to perform more ingestion bites than egestion bites when tested with weak training after a few hours. It seems like the snails are more willing to learn after exposure. That is the perception of the conditioned stimulus or general training and learning seem to have to have become more positive.

Mechanism of the shift in perception

What is actually going on? How does the perception seem to shift? To find this the scientist had to study the underlying circuitry of the snail's feeding center of its brain.

They identified two interneurons that were responsible for the two contrasting behaviors of the snail’s feeding behavior. They found that these two neurons were working competitively with each other in a way in which when one is stimulated the other is inhibited. So the neuron that reaches the firing potential first inhibits the other first hence leading to one feeding behavior than the others.

To test this the scientists blocked the neuron that was responsible for the egesting behavior and found the snail to perform more ingesting bites when fed. So, they concluded that prior exposure to strong favorable stimuli has decreased the firing level for the neuron responsible for the ingesting behavior hence naturally shifting the snail's perception towards new information or stimulus in a more favorable or positive way.

The future looks bright!

This research is groundbreaking in many ways as this suggests that the snail's previous exposure to strong training or learning stimulus opens its brain to a period of high learning capacity. This is possible only by shifting its perception about the new stimulus which would be rather be ignored otherwise. Although it lasts for only about a few hours it is very useful for when it enters a new niche with a large amount of unknown information.

This is remarkable because the human brain is not very different from Lymnaea hence it is likely that there are similar mechanisms in our brains where our past memories could help us learn new things much faster. How our brains shift their perception to new information is not yet fully understood. But this should be found in some future experiments in the not-too-distant future.