A new study reveals how our brains store and change memories. Researchers investigated episodic memory - the kind of memory we use to recall personal experiences like a birthday party or holiday.

They showed that memories aren’t just stored like files in a computer. Instead, they’re made up of different parts. And while some are active and easy to recall, others stay hidden until something triggers them.

Importantly, the review shows that for something to count as a real memory, it must be linked to a real event from the past. But even then, the memory we recall might not be a perfect copy. It can include extra details from our general knowledge, past experiences, or even the situation we’re in when we remember it.

The team say their work has important implications for mental health, education, and legal settings where memory plays a key role.

A new USC study shows teens with higher blood levels of per- and polyfluoroalkyl substances (PFAS) measured before bariatric surgery had smaller improvements in blood sugar over five years, including fasting glucose and hemoglobin A1c (HbA1c), which measures average blood sugar levels over the past 60-90 days. Blood sugar is a key marker of the surgery’s success—and the differences were large enough that the metabolic benefits of the surgery could fade within a decade. The results, published in the journal Environmental Endocrinology, suggest that PFAS exposure may help explain why metabolic outcomes differ among patients. Patient data for the study came from the Teen Longitudinal Assessment of Bariatric Surgery (Teen-LABS), which tracks outcomes among adolescents who have undergone the weight loss procedure. In 186 teens, aged 19 or younger, the researchers measured levels of eight types of PFAS before patients had surgery. After surgery, the researchers tracked each patient’s metabolic health at six months, 12 months, 36 months and five years. To measure short- and long-term blood sugar levels, they collected data on fasting glucose and HbA1c. They also measured insulin and estimated insulin resistance, or how hard the body has to work to keep blood sugar under control. Overall, most Teen-LABS patients had significant improvements in metabolic health after surgery. But teens with higher exposure to all eight PFAS together showed a smaller improvement in long-term blood sugar, with their HbA1c rising, on average, 0.27 percentage points three years after surgery. (For context, a normal HbA1c is under 5.7%, so this increase is considerable.) One PFAS in particular, perfluorohexanesulfonic acid (PFHxS), had an outsized impact. Teens with higher PFHxS exposure before surgery had average annual increases of 0.15 percentage points in HbA1c, a rate that could move someone from normal blood sugar to prediabetes—or from prediabetes to type 2 diabetes—within a few years. PFHxS was also linked to rising fasting glucose, about one milligram per deciliter (mg/dL) per year. At that rate, a patient who initially improved by 10 mg/dL after surgery could see those gains reversedwithin a decade.