This week,an article appeared at NOVA-Next, the companion web site for the PBS NOVA TV series. For those of you who have followed this blog in the past, you will recognize some of the key personnel, and the project they are working on.
Here is the latest in the quest for a memory prosthetic:
Inside the Memory Machine
"Sam Deadwyler and Robert Hampson had spent the 1980s and early 1990s studying how neurons behaved in the rat brain while they performed a simple memory task. Two levers sat side-by-side on one wall of the rat’s cage. After the rat pressed one of the levers, it had to run over to the other side of the cage and stick its nose into a tiny opening. Then, to get its reward, the rat had to go back to the levers and press the other lever. In all of this running back and forth, the rat had to remember both which lever it had pressed and which lever it still needed to press. on
"While the rats performed this task, Deadwyler and Hampson, both neuroscientists at Wake Forest Baptist Medical Center in North Carolina, recorded neural activity in the hippocampus, a seahorse-shaped structure deep in the brain that is the headquarters of learning and memory. They had designed a device containing 16 tiny electrodes and implanted it into the rat’s brain to record electrical activity. Up until that point, the best scientists could do was measure single neurons, but this device could record the activity of a whole group of neurons, giving Deadwyler and Hampson a much more detailed and accurate picture.
"They focused on two regions of the hippocampus: CA3, which showed the highest activity when the rat pressed the first lever, and CA1, which showed highest activity when the rat had to decide which lever to push at the end of the task. After hundreds of repetitions, Deadwyler and Hampson noticed that when the rats pressed the first lever, they found that a group of neurons in CA3 fired in a specific pattern. Then, when the rats had to decide which lever to press the second time, they also found that CA1 patterns fired in a specific pattern.
"'This pattern was the code of the memory, and it was nearly identical from time to time to time—and the system worked from rat to rat to rat,' Hampson says. Based on the activity they observed, they could even tell when the rats were going to make an error. 'The rats are not making mistakes randomly. They’re responding the way they are because the hippocampus encoded the wrong information,' he adds."
Read on at the NOVA Next website!