By Meghan Bialt-DeCelie ‘19

For many animals and humans, a major region of the brain involved in memory formation is the hippocampus. Learning and memory is done through a neural process called long-term potentiation (LTP), and past research has shown that electric stimulation to the hippocampus can promote this process. Researchers led by Ali Titiz, PhD from The University of California Los Angeles found a way to stimulate the brain to improve the memory of epileptic subjects.

The researchers had thirteen human epileptic subjects perform recollection tasks while given a low current electrical stimulation through a 100 µm wire to the left and right entorhinal region of the brain. This electrical stimulation was administered at the beginning of the first phase of the activity in a theta-burst pattern to promote LTP and involved five sets of four biphasic pulses of 100 Hz with 200 ms rest between each set. The recollection task performed involved three phases. In the first, subjects were shown pictures of people and asked whether the person was male or female. In the next phase, they were shown numbers and asked if they were odd or even. Last, the subjects were shown pictures of people, some of which looked similar to the first set, and asked if they saw those pictures before.

In the last phase, patients were able to recall the pictures from the first phase better with theta-burst stimulation even when lured with similar looking photos. This was quantitated by calculating the average change in remembrance rates from unstimulated trials. They found that stimulation to the right entorhinal region significantly improved the memory specificity of the patients. Stimulation of the left did not improve remembrance rates or even made them worse, suggesting that stimulation to the left or right hemispheres can result in opposite biases in memory from each other.

The study provides a better understanding of the areas responsible for memory and memory specificity and can pave the way for targeting treatment of neurological conditions.

References:

1. A. Titiz, et al., Theta-burst microstimulation in the human entorhinal area improves memory specificity. eLife 6, (2017). doi: 10.7554/eLife.29515.
2. Image retrieved from: https://commons.wikimedia.org/wiki/File:PSM_V46_D167_Outer_surface_of_the_human_brain.jpg