Investigating the effects of oscillating sounds on the memory of older populations

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Pfalzgraf, Hadley C.
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Introduction: Memory functions are associated with various oscillations of electrical activity in the brain, and disruptions of those rhythms can be observed in many neurological syndromes, including Alzheimer’s Disease. Oscillations at the theta (3-7 Hz) frequency, in particular, are thought to play an important role in memory. The peak frequency and amplitude of the theta frequency are modulated by age and could be a useful target to combat the cognitive decline commonly associated with aging. Previous studies have induced theta oscillations using transcranial Direct Current Stimulation (tDCS) and repetitive Transcranial Magnetic Stimulation (rTMS). We hypothesized that oscillatory auditory stimulation could similarly entrain theta rhythms in a less invasive, more cost-efficient manner. Preliminary data collected from young adults indicated a positive relationship between theta entrainment and improved short-term visuospatial memory. Methods: We recorded the neural activity, using electroencephalography (EEG), from participants aged over 50 years while they completed a spatial memory task. Three groups of participants with varying memory ability were recruited with no memory complaints (n = 15), mild memory complaints (n = 16), and moderate memory complaints (n = 16). During the first part of the task, participants listened to amplitude modulated noise at 3, 4, 5, 6, and 7 Hz to determine which frequency within the theta band induced the strongest increase in theta power with respect to a pure noise control. Next, participants learned the locations of 30 objects via a spatial memory task administered on a computer. Each object was consistently paired with one of three types of pink noise—constant noise, individualized theta frequency-modulated noise (3, 4, 5, 6, or 7Hz), and 15-Hz-modulated noise (beta). Results: Individuals who identified as having moderate memory complaints had significantly lower MoCA scores than individuals with no memory complaints and preferred lower theta frequencies. Individuals with moderate memory complaints also exhibited lower memory scores in the spatial memory task. Male participants (n = 17) on average displayed higher memory scores compared to female participants (n = 30), despite similar age and memory group distributions. Sounds at an individual’s preferred theta frequency led to an increase in theta activity in the brain compared to pure pink noise and beta sounds. Additionally, there was a main effect of memory complaint group on neural activity in the theta and alpha bands. Conclusions: Subjective memory complaints may be an accurate proxy for the beginnings of age-related neurological changes reflected in EEG activity. More research in this area could contribute to novel diagnostic techniques and therapies for Alzheimer’s Disease. Auditory stimulation could be an easy, non-invasive method to promote beneficial neural activity in aging populations.
Neuroscience , Theta oscillations , Memory , Elderly , Subjective memory complaints , Alzheimer's disease
Pfalzgraf, H. C. Investigating the effects of oscillating sounds on the memory of older populations. MRes Thesis, University College Cork.
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