This is a brand new book, it was a gift from my mother, who knows I am interested in stuff like this. And I was very interested. First of all, it is written well. You don’t have a be a doctor or scientist to understand it. Lauren Aguirre is a journalist and that helps.

It’s a medical mystery, so-called. Tells the story of the discovery of Opioid Associated Amnestic Syndrome. Basically, the use of opioids, particularly fentanyl, can lead to serious damage in the area of the brain responsible for memory encoding, the hippocampus. We’ve discussed the hippocampus before, in our dementia series, episode 233, How the Brain works – memory.

2 ideas particularly intrigued me:

The first is that memory is stored all over the brain. An experiment was done in which mice were allowed to learn how to navigate a maze. Then they had surgery in which a part of the brain was removed. The more of the brain was removed, the less they remembered about the maze, but it didn’t seem to matter which part of the brain was removed. Meaning that memory is stored in fragments in all areas of the brain.

The second is that memories change as they are recalled and affected by other experiences. This was demonstrated using a genetically engineered mouse whose brain responded to light impulses fed into it by fiber optics. The mouse was put in a warm, dark room with an orange smell, allowed to explore, and its brain activity located using fiber optics. Then it was placed in a bright, almond-scented room, where mild electric shocks were added to areas, making the mouse freeze to avoid the shocks. While in the room, the same areas of its brain were stimulated. When it returned to the first room, it froze as if avoiding shocks. The conclusion is that memories change.

Fentanyl is widely used as a general anesthetic, and some patients experience memory loss after surgery. It is known to produce loss of memory of the time during which the patient is under its influence. So this is something that definitely needs further study. But the studies outlined in the book include memory loss due to overdose of fentanyl.
If you are as into neuroscience as I am, you will definitely enjoy this book.