Deep Brain Stimulation for Memory Modulation: A New Frontier.

In the coming years the number of patients with cognitive disorders, such as Alzheimer disease and traumatic brain injury, is expected to dramatically increase, leading to an ever-increasing societal cost. Unfortunately, few medical and pharmacologic treatments have shown tangible benefit in the treatment of these diseases. Deep brain stimulation (DBS) is an established surgical technique to address multiple conditions, including Parkinson disease and essential tremor. Data from patients being treated with DBS, as well as those being monitored for seizures with depth electrodes, have suggested improvement in memory with electrical neuromodulation.MEDLINE was searched from inception through March 2018 using the keywords "DBS," "Deep Brain Stimulation," "Memory," "Memory Modulation," and "Cognition." Studies evaluating the effect of DBS on memory and learning were shortlisted and reviewed.Efforts to stimulate various nodes within the memory circuitry suggest that the variable effects may result from different mechanisms, including alteration of neural firing patterns, increased activity across several regions, and amplification of neural plasticity. Some of these targets, such as the entorhinal cortex, hippocampus, and nucleus basalis of Meynert, have shown promising results with regards to modulation of memory.Given the aging population and increasing numbers of patients with memory impairment from neurodegenerative diseases, interest in neuromodulation for memory enhancement will likely expand. Further work should employ more sophisticated responsive stimulation parameters and precise spatial targeting that may lead to an effective stimulation strategy for memory enhancement.