The Changes of short-term memory and Autonomic neurocardiac function after 4-10Hz sound and light stimulation: A pilot study

Lee, Seung Hwan; Kim, Jin Hwan; Park, Joong Kyu; Lee, Kyung Uk; Yang, Dae Hyun; Kim, Sun Hee; Chae, Jeong Ho

Abstract

OBJECTIVES
Sound and light (SL) stimulation has been used as a method to induce some useful mental states in the fields of psychology and psychiatry. It is believed that sound and light entrainment device (SLED) has some specific effects through synchronization of EEG in patients who use it. Theta frequency is believed to stimulate deep relaxation and short term memory processing. This study was conducted to evaluate if 4-10Hz SL stimulation can induce relaxation and improve short term memory function. METHODS: Ten medical students with no medical or psychiatric problems participated in this study. Subjects were randomly divided into two groups. One group was applied with real SLED was applied to one group (R group) and pseudo SLED to the other group (P group). The two groups were exposed to SL stimulation with SLED 15 minutes a day for 5 days, and after two days rest the two groups were switched over. The Korea Wechsler Adult Intelligence Scale (K-WAIS), Academic Motivation Tests (AMT), Test Anxiety Scale (TAS), Korea Auditory Verbal Learning Test (K-AVLT), and digit span were used to evaluate short term memory. Spielberger's State-Trait anxiety inventory and heart rate variability (HRV) test were used to evaluate degree of relaxation. RESULTS: Compared with S group, R group showed a significant improvement in K-AVLT and digit span after a single application of SL stimulation. But 5-day long application did not reveal any differences between the two groups. A significant change in HRV was observed in 5-day long application of SL stimulation after being switched over to other SLED. CONCLUSION: This pilot study suggests that 4-10Hz SL stimulation has some positive influences on short term memory and relaxation.