What Am I Forgetting?

In September, a paper was published in the journal “Science” by a team of researchers in Japan. While studying sleep regulation in mice, the team had stumbled upon melanin-concentrating hormone (MCH) neurons in the hypothalamus—a region in the brain mainly responsible for memory. Contrary to traditional neurons, which are most active when the brain is “awake,” the MCH neurons only spring into action during a phase of the sleep cycle called R.E.M. (rapid eye movement) sleep. This kind of sleep is characterized by rapid eye movements, dreaming, physical movement, and increased pulse and breathing.

Upon further research, the researchers discovered that the MCH neurons were suppressing other brain cells in the hippocampus. To determine the neurons’ effects on the hippocampus, they used genetic tools to switch MCH neurons on and off in different mice, exposed the mice to two foreign objects, allowed them to sleep for a time, and repeated the process after replacing one of the old objects with a new object. The report stated that “genetic ablation of MCH neurons increased memory performance in mice. Conversely, pharmacogenetic activation of MCH neurons impaired memory.” Furthermore, mice who had their MCH neurons amplified approached both items with similar, uncertain behaviors, while those who had their neurons suppressed tended toward the foreign object, indicating that they retained their memories of the old objects and felt no need to explore them again. This, according to Dr. Akihiro Yamanaka, a neuroscientist who worked on this discovery, suggests “that hypothalamic MCH neurons help the brain actively forget new information that is not important.” This new discovery is critical in understanding the important role that MCH neurons play in the way we retain our memories.

Another significance of the report is that “vitro physiological experiments showed that activation of MCH fibers in hippocampal slices suppressed spiking activity of pyramidal cells.” Pyramidal cells are multipolar neurons that function in transporting large amounts of information. Therefore, the fact that the researchers were able to manipulate MCH neurons and thus change the function of pyramidal cells presents a potential future where we could revamp our memory processing for practical use. For example, applying such methodology to modern medical science could have various important impacts on treating memory-related diseases, expanding the limits of human memory, and constructing a better understanding of how the brain works with both memory and sleep.

The concept that the hippocampus serves as a place of both memory formation and destruction is highly important; we are bombarded with excessive information every day, and some sort of mechanism is necessary to sort and filter all the unnecessary memories from the important ones. Take the case of “S,” a journalist who came to Dr. Alexander Luria's office in 1929 and claimed that he could never forget a piece of information, no matter how hard he tried. S was able to recite entire stories, poems, formulas, and virtually anything if he focused enough. S's memory was seemingly so strong that he was able to remember information years after learning it. However, his inability to forget haunted him, as he could not understand nuanced and abstract concepts and even had a hard time remembering faces due to memories that clouded his brain. Clearly, forgetting things is just as instrumental to day-to-day life as remembering them.

Soon, we may see how altering our ability to forget can have significant implications on how we learn. Picking and choosing what you remember sounds like a futuristic concept, but now such technology appears to be much closer at hand. It is highly important to strike a balance between forgetting and remembering, and this is especially important when put in the perspective of Stuyvesant High School. Students always struggle to find the right balance between studying an extra hour for a test and squeezing in that extra hour of sleep. Understanding how our memory works in conjunction with sleep is critical for finding this balance and can lead to the discovery of even more practical information. This can include figuring out the optimal times for going to sleep and waking up to orient our work schedules, individualizing approaches to studying and avoiding burnout, and decreasing the chances of being diagnosed with a memory-related disease.