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USING FIXED PATTERN STIMULATION CODES THAT MIMIC NEURAL ACTIVITY TO MODULATE MEMORY PERFORMANCE

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abstract
Memory loss is a debilitating problem that not only effects a person in their every-day life, but can attack that person’s sense of self. A multitude of conditions, such as Traumatic Brain Injury (TBI), Epilepsy, and Alzheimer’s Disease, either can or will result in interference with a person’s ability to form new memories. The development of a neural prosthetic that increases memory functions therefore offers a possible solution that can be used in all of these cases.The research that is contained in my thesis focuses on testing a stimulation technique to enhance memory retention for specific information, specifically visual and semantic information regarding the type (category) of images including animals, buildings, plants, tools, and/or vehicles. By recording activity in the hippocampus – a brain area known to be involved in creating new memory – we were able to model the memory "codes" when patients viewed these images and create electrical stimulation patterns to mimic the brain activity in hippocampus. These patterns were then applied in patients performing a memory task to determine if they would enhance memory for that information. Patients with epilepsy which required seizure monitoring through the use of electrodes implanted into the brain to localize seizure origin and spread were recruited at Wake Forest Baptist Medical Center, USC Keck Memorial Hospital, and Rancho Los Amigos National Rehabilitation Center. Participating patients agreed to have the electrodes necessary for their seizure monitoring supplemented with electrodes that included additional recording sites for our study. The electrodes with additional recording sites were used in place of the regular electrodes implanted in the hippocampus. xi The study utilized a computerized Delayed Match to Sample (DMS) Task, and a combined DMS and Delayed Recognition (DMS+DR) Task. The tasks were presented on a computer, and patients responded by touching images on a touchscreen. DMS Tasks were used to gather the neural recordings used to generate the stimulation patterns, while the DMS+DR task was used to test the stimulation patterns. A DMS task consisted of 100 to 150 trials where a patient was shown a single image in the sample phase, retained that memory, then picked the same image in the match phase. In the DMS+DR task, the DR portion would show both images from the DMS task and new images to the patients and have the patient rate how well they remembered the images. These ratings were used to determine if a patient successfully remembered the sample images from the DMS trials. The first experiment tested the effect of stimulation using the category patterns created from a patient’s own memory codes. This experiment posed two questions; does this stimulation method work to change memory performance, and if it does change memory performance how well do the stimulation patterns work to enhance memory. In nearly 20% of all stimulation tests, we found that memory performance had been changed due to stimulation. The magnitude of change varied between patients; however, the majority of patients showed changes in performance due to stimulation. This result suggests that stimulation with patterns designed to mimic specific human memory codes will alter memory performance. While memory was clearly modified by stimulation, the results included both increased and decreased performance, suggesting that further development is required to allow better creation of codes specific to the memory information they are intended to enhance.
subject
contributor
roeder, brent michael (author)
Hampson, Robert (committee chair)
Constantinidis, Christos (committee member)
Maier, Joost (committee member)
Kishida, Kenneth (committee member)
Ferris, Mark (committee member)
date
2021-06-03T08:36:21Z (accessioned)
2021 (issued)
degree
Neuroscience (discipline)
2022-06-02 (liftdate)
embargo
2022-06-02 (terms)
identifier
http://hdl.handle.net/10339/98843 (uri)
language
en (iso)
publisher
Wake Forest University
title
USING FIXED PATTERN STIMULATION CODES THAT MIMIC NEURAL ACTIVITY TO MODULATE MEMORY PERFORMANCE
type
Dissertation

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