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How brains make memories and what can alter them

Learn what neuroscientists know about how scent and stimulation affect memory during sleep and exercise. Plus, what happens when we alter those triggers.
A dreamy toned photo of a stack of Polaroid photos with one showing a Ferris wheel on top.

Your newsletter author can remember pages of poetry she memorized aloud 20 years ago, but can never remember how to spell commission on the first try. (Google auto-corrected that.) The scent of sawdust sends her right back to childhood (dad was a contractor), while the smell of Play-Doh evokes nothing.

This week, we explore what neuroscientists know about how our senses affect memory—and how we can use sensory triggers to alter memory to our benefit.

  • Checkup: to stop + not to stop
  • Memories: scent + motion + sleep 
  • Healthcare: women docs + clots + mpox


Remember that scent?

Close-up of a farmer with dirt on her hands and around her fingernails, holding fresh plums she just harvested in Santa Cruz, California.

Around 100 years ago, neuroscientists assumed there was a connection between our sense of smell + the creation of memories. Today, they’ve found out how powerful that connection is.

Our nose contains hundreds of receptors primed to receive specific odors—like a key going into a lock. Once opened, olfactory sensory neurons start firing in areas of our brain that help us understand the smell (the olfactory/piriform cortex), make an emotional connection to it (the amygdala) and remember it (the hippocampus). If the hippocampus has determined the scent is important, smelling it years or decades later can force the emotional memory back into the present. Some scent memories can boost our well-being. Others can trigger trauma.

The connection is so profound that a lost sense of smell can precede other Alzheimer’s symptoms by years—knowledge that can help with early diagnosis. Conversely, one study of veterans with combat-related PTSD found that scent exposure therapy successfully helped them detach from common triggers (like diesel fuel). To learn more about the research + its future, head to Harvard Medicine.

Can exercising in VR improve memory?

A sweaty young Asian woman with long wavy black hair wearing a black t-shirt stares at something away from the camera as she lifts a VR device from her head.

Studies show that aerobic fitness can improve executive function—the attention, planning, time management and multitasking that happen in the frontal lobe of the brain. A new study suggests that exercising in a virtual reality setting may enhance memory even more.

For the small study, 23 young, healthy participants were put through tests to set performance, memory + mood baselines. They then rested, exercised + exercised with a head-mounted VR display that showed them biking through Paris.

Repeat mood tests showed that VR exercise increased their vitality + arousal more than regular exercise. Memory reaction times were faster after both forms of exercise—but areas of the brain responsible for executive function were most active after the VR sessions. The report has not yet been peer-reviewed. But it suggests that the environment we exercise in may affect our stimulation, pleasure and overall brain health.

Can we reshape the sleeping brain?

A beach shore at sunset, with a tent on the shore and a pair of feet sticking out.

While we sleep, neurons in our brain fire in ripples, spindles + waves at varying speeds + frequencies. During the deep sleep stage, three things happen in a process experts call memory consolidation:

A cluster of spindles buzz around the thalamus, which stores information throughout the day. Slow waves emit from the cerebral cortex, which helps us interpret the information while we're awake. (At night, it does so without our input.) High-frequency ripples in the hippocampus cement memories. Then, we move into REM sleep, where it blends into dreams + nightmares.

In the last 20 years, several studies have successfully interrupted this process.

One study timed soft click sounds to participants’ slow waves—this enhanced the size + duration of those waves, which improved participants’ scores on memory tests. Another had participants with nightmare disorder imagine happier endings to their recurrent nightmares while they listened to a piano chord. When that chord played during their REM state, the nightmares improved—or disappeared entirely.

The findings could lead to wearable tech therapies. But researchers warn they’re years away + memory manipulation is not yet safe on a population level.

Read the fascinating details at Scientific American.

Healthcare 411

Surgical outcomes better with more women on your team (US News). A study out of Canada found that when 35% or more of surgical teams were female, patients’ post-op outcomes improved. The study analyzed over 700K surgeries across 10 years, and the findings support similar outcomes in studies from the US, Italy, Australia and Japan.

Genetics played role in rare blood clots linked to Covid-19 vaccines, researchers find (Time). Researchers discovered that people with a particular gene expression trigger antibodies that attack a protein that helps blood clot, putting them at higher risk for adenoviruses (which cause the common cold + conjunctivitis) and adenovirus-based vaccines like the J&J + AstraZeneca vaccines. 60 clotting cases were reported among the 18 million J&J jabs. In Australia, Astra vaccine complications occurred in 2-3 people per 100,000 + saved around 6.3 million lives.

CDC warns of a resurgence of mpox (NY Times). On Thursday, the CDC warned that a deadlier version of mpox is currently ravaging the Democratic Republic of Congo. (The 2022 outbreak spread from Nigeria.) They encourage vaccination before Pride events bring at-risk people in LGTBY+ communities closer together. Head to the article for details. For more about the history of mpox + vaccination, read Dr. B’s coverage.

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