Researchers from Germany developed a method to track and manipulate memories in fruit flies. With this method, they can watch memories form, change them as they develop, and may even be able to implant artificial ones.

Their results were recently published in the journal PLOS Biology. The study authors are confident this is an important step in understanding what memories are and how they work.

Jan Pielage, one of the authors of the study, claimed “Now we have genetic access to get after the cellular and molecular changes occurring during long term memory formation.”

What is Memory?

In the simplest terms, memory is the brain’s ability to encode, store, and retrieve information. However, not much is known about how this actually happens.

We do know that when memories are formed the connections between neurons are restructured. That is, new connections are formed, some are broken, some are strengthened, and some are weakened. With 100 billion neurons in the brain and with each being connected to 10 thousand other neurons, the possibilities are astronomical.

One explanation for memory is that it is composed of a vast collection of synapses, which are the transferring of chemical and electrical signals from one neuron to others. When a neuron fires, it releases a burst of neurotransmitters. These bind to the receptors of other neurons, causing a change in their properties, a process known as signal transduction. Through use, this connection becomes stronger and can involve large networks of neurons. This means that when one neuron is activated, it can activate the entire network, as well as other connected networks.

Neuroscientists believe that if “one of the resulting networks of interconnected neurons is activated, others are also likely to be activated, and this enhanced connectivity encodes information.”

Therefore, one stimulus can activate large networks and clusters of networks that have been previously encoded, which explains why a smell, for example, can evoke an old feeling.

We also know that there are 3 stages of memory: sensory, short-term, and long-term. Sensory memory stores inputs from the environment for a brief moment. For example visual information is stored for a less than half a second, whereas audio information is stored for around 3 seconds. The information that we focus on is then transferred to our short-term memory, where it is stored for between a few seconds and 30 seconds. These form our working memory, which allows us to hold on to information while performing other tasks, such as remembering a phone number while searching for a pen to write it down.

Information is then transferred to the long-term memory, which can be subdivided into implicit and explicit. Implicit memory is the unconscious mind and involves procedural memories, like riding a bike, and priming, which uses “pictures, words or other stimuli to help someone recognize another word or phrase in the future.”

Explicit memory is part of the conscious mind and is divided into episodic and semantic. Episodic memories are events that have happened to you, and semantic memories are general knowledge about the world.

Where are Memories Stored?

Since the early 1900s, scientists have tried to pin down the exact location of where a single memory, or engram, is stored in the brain. Beginning in 1916, the psychologist Karl Lashley spent years letting rats learn the path through a simple maze, then systematically destroying nonessential parts of their brains, and then letting them try the maze again. Much to his frustration, no matter which part of the brain he destroyed, the rats always remembered the path to the end.

What Lashley didn’t realize was that memories are highly distributed and involve basic areas of the brain that he wasn’t willing to destroy.

Thanks to brain imaging techniques, we now know memories are mostly distributed across the cerebellum, the amygdala, the hippocampus, and the prefrontal cortex. Using techniques like functional magnetic resonance imaging (fMRI), researchers can watch which areas of the brain become active during encoding, storing, and retrieval of memories.

Moreover, researchers can now use a new technique called multi-voxel pattern analysis (MVPA). This is a set of deep learning algorithms that takes data from brain scans and computes the neural patterns of specific memories. In one study, the techniques of fMRI and MVPA were used on participants watching different scenes from a Sherlock Holmes movie. The results showed patterns that were “remarkably specific, at times telling apart scenes that did or didn’t include Sherlock, and those that occurred indoors or outdoors.”

While the above techniques are impressive, they failed to isolate an engram.

Engrams and Fruit Flies

Engrams are tough to nail down because of the difficulty in marking specific neurons. That is, to trace a single memory requires tagging neurons with biomarkers that only respond to the neurons forming the memory. However, neurons share the same DNA, meaning a tag cannot be designed for some and not for others–or at least it was thought.

A team of researchers from Germany recently developed a tag that responds to memory formation. Called the CRE-activity dependent memory engram label (CAMEL) it works by utilizing the DNA binding site for CRE binding proteins, which play an essential role when forming memories. When these proteins are present at the binding site, then a memory is being formed, causing CAMEL to light up. Therefore, researchers can isolate only the neurons that are forming memories, singling out an engram.

The team demonstrated their technique in the brains of fruit flies, due to their simplicity. While doing this, they also found they could turn neurons that stored memories on and off, allowing them to create associations between stimuli and responses. For example, by manipulating specific neurons, they made the fruit flies afraid of a certain odor and of red light, as they associated both with an electric shock.

Next, the team plans on trying to implant artificial memories in the fruit flies.

What are the Implications?

Like any advancement in science, the above techniques can be used for good or bad, although they have not yet been applied to more advanced brains, namely those of humans.

For example, a benefit of tinkering with memories might be trauma treatment, in that harmful memories can be targeted and changed. People that have suffered from abuse, war veterans, etc., would be able to just simply erase the problem.

On the other hand, it may open the door to all kinds of strange and unethical practices, a la the movies Eternal Sunshine of the Spotless Mind, Inception, Total Recall, among many others. That is if scientists can manipulate memories, then they can change the very essence of a person, often with dire outcomes.

If this gets used on humans, will it be an example of science going too far? There’s no way to tell, but, in the opinion of this author, the answer is likely yes.

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