Do You Remember What You Had for Breakfast Last Year?

Graphic by Jake Slaughter

We’ve all fantasized about having photographic memory. Never needing to study and never forgetting a birthday seems like a superpower. But when considering the perks of perfect memory, we often fail to recognize the value of forgetting.

Patient AJ and Subject S. remember nearly every event from every single day of their lives. They suffer from hyperthymesia, a condition that significantly enhances their ability to form and retrieve episodic memories. The weather from every day in 2005, a condiment added to a hotdog at one’s first baseball game: patients with hyperthymesia could rattle these off with ease. When studied by researchers, Patient AJ could not only recite the events of the previous year’s Easter, but also the preceding 35 Easters. Similarly, after being shown a lengthy string of numbers for a few minutes, Subject S. could still flawlessly recall the sequence over ten years later.

 Neither subject acquired their uncanny memory through practice; rather scientists found that they had certain abnormally large brain structures in common. These included portions of the prefrontal cortex and temporal lobe—the region which houses the hippocampus, one of the brain’s memory centers.

But scientists still advise against jumping to any conclusions about a causal relationship between certain brain structures and hyperthymesia, since this ability has only been observed anecdotally in 25 patients around the world. Researchers are currently investigating the cause of this perplexing condition, and exploring potential treatments. 

While the prospect of having perfect memory may sound like a blessing, the costs far outweigh the benefits. For instance, Subject S. was unable to recognize faces and conceive of abstract ideas due to his inability to forget. As a result of memorizing exact snap-shots of people’s facial expressions, Subject S. failed to match faces across different contexts, and thus struggled with facial recognition.

Patient AJ and Subject S. can teach us a valuable lesson: the ability to forget is critical in our daily lives. The overwhelming abundance of  information that we receive on a regular basis is too much to attend to, and so we need a mechanism to clear out space in order to store new memories.

A recent study showed that there may be specific cells that play this exact role in the human brain. Melanin-Concentrating Hormone (MCH) neurons were discovered to be a biological mechanism of forgetting. These cells inhibit the activity of neurons within the hippocampus during REM sleep. In addition, their genetic inhibition leads to a significant improvement in memory-related tasks. While this field is still relatively unexplored, it is fascinating to consider the possibility that people like Patient AJ and Subject S. may have developed inadequate or malfunctioning MCH neurons. In this realm, researchers may be able to genetically modify the activity of these neurons in hyperthymesia patients as well as patients who suffer from amnesia.

The ability to forget is an integral part of our social and emotional wellbeing, as well as our mental health. While trying to memorize flashcards for an upcoming exam, remember to thank your MCH neurons for clearing up some space for those memories to be made.

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