Targeted electrical stimulation may improve memory in patients with epilepsy and traumatic brain injury (TBI), a study found.
Machine-learning high-frequency stimulation to the temporal cortex of patients with epilepsy and traumatic brain injury (TBI) improved memory recall by 19%, according to a closed-loop stimulation study published in the journal Brain Stimulation.1
“The last decade has seen tremendous advances in the use of brain stimulation as a therapy for several neurological and psychiatric disorders including epilepsy, Parkinson’s disease, and depression,” said lead study author Michael Kahana, PhD, professor of psychology at the University of Pennsylvania, in a statement.2 “Memory loss, however, represents a huge burden on society. We lack effective therapies for the 27 million Americans suffering.”
TBI is often associated with short-term memory problems and has affected about 1% to 2% of the world’s population. Although prior studies have found electrical brain stimulation improved memory in patients with epilepsy, it was unclear if these results could be generalized to patients who also have a history of TBI.
In the current study, the researchers trained personalized machine-learning classifiers to predict momentary fluctuations in mnemonic function in a select subgroup of patients with a history of moderate-to-severe TBI who underwent neurosurgical evaluation for refractory epilepsy. These classifiers were then used to trigger high-frequency stimulation to the lateral temporal cortex when memory was expected to fail.
A total of 8 patients were recruited for the study, including 7 males and 1 female. Most of the patients' injuries occurred years prior to TBI evaluation and included reports of a significant head injury accompanied by a loss of consciousness longer than 30 minutes, post-traumatic amnesia, or imaging results suggesting moderate-to-severe brain injury.
All patients underwent multiple sessions of non-stimulation behavioral treatment followed by at least 1 session of closed-loop stimulation. Patients were asked to perform a non-verbal recall task on a laptop in which they were given a set of lists that comprised 12 words selected without replacement from a pool of nouns grouped into 25 semantic categories, such as beverages, kitchen appliances, zoo animals, etc. Each list of words contained 4 unique words at random from each of 3 selected categories.
The researchers then analyzed whether memory improved across entire lists of words when only some words were stimulated, rather than prior studies that only stimulated individual words.
After undergoing the stimulations, memory recall improved by 19% in stimulated lists compared with non-stimulated lists (P = .012). Furthermore, the observed improvement suggests a 0.44 standard deviation increase, and a theoretical reduction in the burden of delayed-free recall impairment by 53.6% in TBI-afflicated patients in the study.
While the researchers believe the results of this study were encouraging, they also noted that further research needs to be done to establish the validity of this technique in a clinical, real-world setting, as well as the long-term efficacy of brain stimulation as a treatment option for patients with TBI.
“These are still early days in the field,” said Ramon Diaz-Arrastia MD, PhD, Department of Neurology, University of Pennsylvania, and author of the study, in a statement.2 “I think eventually what we would need is a self-contained, implantable system, where you could implant the electrodes into the brain of someone who had a brain injury.”
1. AI-guided brain stimulation AIDS memory in traumatic brain injury. Press release. University of Pennsylvania. July 18, 2023. Accessed July 18, 2023. https://penntoday.upenn.edu/news/ai-guided-brain-stimulation-aids-memory-traumatic-brain-injury
2. Kahana MJ, Ezzyat Y, Wanda PA, et al. Biomarker-guided neuromodulation AIDS memory in traumatic brain injury. Brain Stimulation. 2023;16(4):1086-1093. doi:10.1016/j.brs.2023.07.002