Our Brains Are Prediction Machines

In 1953, Henry Molaison, suffering from debilitating epilepsy, underwent a radical surgery. Having exhausted all known forms of treatment at the time, his doctors decided to remove the part of his brain that they had isolated as the cause of his seizures, the hippocampus.

Upon recovering, his epileptic condition had vastly improved, but there was a startling side effect. He could no longer form new memories. “Every day is alone in itself, whatever joy I’ve had, and whatever sorrow I’ve had,” Molaison said.

Much like Leonard Shelby in the film Memento, he suffered from what the medical field calls anterograde amnesia. He had memories from before the surgery, but after, it wouldn’t matter if you had seen him a hundred times, in his mind he would still be meeting you for the first time.

That alone astonished researchers, as it was believed at the time that memory was delocalized in the brain. But even more surprising was that Molaison could learn new things, such as new motor skills.

It turned out that not only were memories of events localized in the hippocampus, but also other kinds of memory, such as skills or habits, were localized elsewhere.

Although a tragedy for the patient, this surgical mishap revolutionized our understanding of how memories are formed and stored in the brain.

Today at UT’s Center for Learning and Memory, Alison Preston takes our understanding of brain structures and memory beyond what was learned from Molaison. “Remembering an event is a form of mental time travel. We can all be Dr Whos in our TARDIS” Preston said recently, referring to the British sci-fi show about the time-traveling humanoid who explores the universe in a sentient time machine.

Speaking as part of the “Hot Science, Cool Talks” series, Preston spoke about how her lab researches. There, scientists study how the hippocampus and other parts of the brain influence aspects of thought outside of memory, such as learning, and also how these structures help us to not only recall the past, but to perceive the future as well.

“Our brain is a prediction machine,” Preston said.

In one experiment her lab conducts, subjects are presented pairs of images while being given an fMRI scan, a non invasive method for determining which sections of the brain are active. Later, participants answer questions related to the images.

With the aid of a computer, researchers can determine from the fMRI what kind of image from the experiment the person is recalling, such as a scene versus an object, “a form of mind reading,” Preston joked.

They can then measure performance on various tests, and compare results from when a person is recalling a certain image, versus when they are not. From these studies, it appears that memory helps us in other kinds of reasoning, such as making inferences, in ways that were previously unknown to scientists.

More understanding into how these brain structures interact can lead to better teaching methods, showing us how memory of previous lessons can be better harnessed to facilitate learning of new skills.

Preston’s research may also ultimately help with treatment of degenerative neurological disorders, such as Alzheimer’s.


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