Stuck in yesteryear? An implant can help patients with memory loss form new memories.
Henry Molaison was a 27-year-old man who suffered from epilepsy in 1953 when a surgeon removed a part of his brain — two seahorse-like structures called the hippocampus.
But suctioned away on the operating table in Hartford, Connecticut, was Molaison’s ability to form new memories.
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Though small is size, the hippocampus does the heavy lifting of defining who we are. It forms new memories and prepares them to be stored long term, allowing them to be retrieved when needed.
But for the 5.5 million people in the United States suffering from Alzheimer’s, and for those who suffer strokes, damage to the hippocampus might lead to irreparable memory loss.
A team of neuroscientists at the University of Southern California and Wake Forest University are working on an implant that can help move the memories there directly, a type of brain prosthesis that bypasses the damaged hippocampus.
The new implant helped improve recall for patients with brain damages by up to 90 percent.
The brain prosthesis is a computer algorithm that reads the message coming into the brain — like the picture of a house, or where the car is parked — and codes it in the way the hippocampus would. That allows another region of the brain to receive the memory and store it, so that an hour later, the individual can recall her car’s location.
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“It’s like being able to translate from Spanish to French without being able to understand either language,” Theodore Berger, professor of biomedical engineering at USC, told LifeZette.
Berger is lead neuroscientist on the project, which was presented this summer at an annual meeting of medical engineers.
Messages are communicated from one part of the brain to another via electrical signals, USC professor Dong Song said. An electrode surgically implanted in the brain reads the brain’s electrical signals and conveys them to the computer that encodes them via an algorithm that Song wrote.
The computer system duplicates the work of the hippocampus by encoding the signals as they travel through its various regions and re-encodes them along the way. When the signal reaches the end, it can be transformed into a message and turned from short-term to long-term memory.
The prosthesis was first tested on animals. The memory functions of rats and monkeys could be restored after the hippocampus was removed.
The team moved on to human trials last year. Twelve patients with damage to their hippocampus had electrodes surgically implanted in their brains. For an hour every day for several weeks, they were shown images. They waited a period of time when they’d normally forget the images. Then they were shown the images in a line up of others and were asked to pick them out. The study showed the accuracy of their retrieval ability was up to 90 percent.
“Extremely exciting is the fact is that this intervention can help improve cognitive function,” said Brian Robinson, a graduate student working on the project, in an interview with LifeZette.
Although Henry Molaison didn’t live to benefit from an intervention to help regain memory function, he provided scientists with invaluable knowledge about the brain that helped build a prosthesis like this, and to appreciate just how complicated memory can be.
For Song, who has been working on this project for more than 20 years, the trials on actual patients are promising, but also daunting.
“We are dealing with simple memories here. In real life, we remember many more things like emotion,” Song told LifeZette. “The next step is for us to build more sensitive and complex models that can account for all that.”
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