When a person’s brain receives sensory input, the electrical signals are decoded in various sensory areas of the cortex, and then combined in the brain’s hippocampus, the brain’s memory centre, into one single experience. The hippocampus is then responsible for analyzing these inputs and ultimately deciding if they will be committed to long-term memory. Memory can be impaired by various injuries and diseases. Damage to the medial temporal lobe and hippocampus can devastate the ability to form new memories; damage to the storage areas in cortex can disrupt retrieval of old memories and interfere with acquisition of new memories, simply because there is nowhere to put them.
Now, researchers at USC and Wake Forest Baptist Medical Center have developed a brain prosthesis that is designed to help individuals suffering from memory loss. The team state that the novel prosthesis, which includes a small array of electrodes implanted into the brain, has performed well in laboratory testing in animals and is currently being evaluated in human patients. The research was presented at the 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.
Previous studies show that if there’s damage at any brain region involved in the re-encoding of memory-based electrical signal, then there is the possibility that long-term memory will not be formed. An individual with hippocampal damage can recall events from a long time ago and have difficulty forming new long-term memories. This is because the electrical signals were already encoded into long-term memories before the brain damage occurred.
The current study found a way to accurately mimic how a memory is translated from short-term memory into long-term memory using data obtained from animal and humans. The team explain that the prosthesis is designed to bypass a damaged hippocampal section and provide the next region with the correctly translated memory.
The effectiveness of the model was tested with the permission of patients who had electrodes implanted in their hippocampi to treat chronic seizures. The group read the electrical signals created during memory formation at two regions of the hippocampus and used that information to construct the model. The lab then fed those signals into the model and read how the signals generated from the first region of the hippocampus were translated into signals generated by the second region of the hippocampus.
Results in hundreds of trials conducted with nine patients, showed that the algorithm accurately predicted how the signals would be translated with about 90 percent accuracy.
The team surmise that being able to predict neural signals with their new model suggests that it can be used to design a device to support or replace the function of a damaged part of the brain. For the future, the researchers will attempt to send the translated signal back into the brain of a patient with damage at one of the regions in order to try to bypass the damage and enable the formation of an accurate long-term memory.