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Effect of bilateral somatosensory stimulus on oscillatory brain activity and long term memory

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2017
Göktepe, Gizem
A psychotherapy treatment called eye-movement desensitization and reprocessing (EMDR) is used to elicit traumatic memories in shorter time and decrease its negative effect by using bilateral saccadic eye-movements, auditory and tactile stimuli. As yet, there is no well-accepted result with regard to the effect of bilateral stimuli on long term memory. In this thesis, effect of bilateral somatosensory stimulus on oscillatory brain activity and long term memory was investigated. Accordingly, a novel face recognition paradigm was designed comprising two separate sessions of memory encoding and recognition. In the encoding session, 240 face images consisting of 3 ethnicities as asian, black and white were uniformly presented to 20 university students. In the recognition session, with and without somatosensory stimulus applied, totally 336 face images (240 old, 96 new) were presented to the subjects while they were asked whether they had seen them previously. EEG recording was performed only during the recognition session. Analysis showed that bilateral somatosensory stimulus increased alpha activity in the left parieto-occipital channels prior to the stimulus and in the right parieto-occipital channels during decision making. Furthermore, subjects, who increased long term memory performance, also had significantly greater alpha activity in the frontal channels when somatosensory stimulus was applied. Our study shows that bilateral stimulation may change the long term memory performance along with a modification in the oscillatory brain activity.