To demonstrate this, Carmena and Karunesh Ganguly, a post-doctoral fellow in Carmena's laboratory, used a mathematical model, or "decoder." The decoder, analogous to a simplified spinal cord, translated the signals from the brain's motor cortex into movement of the cursor.
It took about four to five days of practice for the monkeys to master precise control of the cursor. Once they did, they completed the task easily and quickly for the next two weeks.
As the tasks were being completed, the researchers were able to monitor the changes in activity of individual neurons involved in controlling the cursor. They could tell which cells were active when the cursor moved in specific directions. The researchers noticed that when the animals became proficient at the task, the neural patterns involved in the "solution" stabilized.
There are three major features scientists associate with motor memory; stability once a motor memory is consolidated it is difficult to change, rapid recall upon demand, and resistance to interference when new skills are learned. All three elements were demonstrated by the macaques in the UC Berkeley study.
To test resistance to interference, the researchers presented a new decoder marked by a different colored cursor two weeks after the monkeys showed mastery of the first decoder.
As the monkeys were mastering the second decoder, the researchers would suddenly switch back to the original decoder and saw that the monkeys could immediately perform the task without missing a beat. The ability to switch back and forth between the two decoders shows a level of neural plasticity never before associated with the control of a prosthetic device.
"This is a study that says that maybe one day, we can really think of the ultimate neuroprosthetic d
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