Can memory prostheses boost memory?

Brain electrodes can help understand the electrical activity patterns when memories are encoded and then use those same electrodes to fire similar activity patterns in the hippocampus—a seahorse-shaped region deep in the brain that plays a crucial role in memory. Memory prosthesis is an electrode inserted deep into the brain to help people with memory disorders—and it is most effective in people with poor memory. 

In a healthy hippocampus, electrical activity flows from one layer to another before spreading to other brain regions. A decoding memory model (MDM) mimics patterns of electrical activity across the hippocampus that occur naturally when we successfully form memories. The MDM model takes an average of these patterns across each individual and then fires off this pattern of electrical stimulation. A multi-input, multi-output model more closely mimics how the hippocampus works by learning the electrical inputs and outputs corresponding to memory encoding and then mimicking them.

The memory prosthesis improved the volunteers' performances significantly on memory tests—if they had received the correct pattern of stimulation when first presented with the images. The prosthesis improved brain memory encoding by 11% to 54%. The most significant improvements occur in people with the worst memory performance at the start of the experiment. 

The electrodes used in the study are around a millimeter wide, and all the volunteers had them implanted deep enough into the brain to reach the hippocampus—around 10 centimeters deep. The hippocampus patterns associated with successfully stored memories are unique and different for each person. Therefore, customizing stimulation to individual brains by mirroring the hippocampus working will likely require brain electrodes with hundreds of contact points, allowing them to record from and stimulate hundreds or thousands of neurons. 

Although the prosthesis is still in some way from clinical use, more advanced versions could help people with memory loss due to brain injuries or aging or degenerative diseases like Alzheimer's.

Read the whole article on the memory prosthesis.c

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