The role of 40 Hz auditory stimulation in sustaining cognitive health: a pilot study in dementia

Abstract

This case series examined the potential cognitive and neuro-physiological effects of daily auditory stimulation at a 40 Hz gamma frequency with dementia patients. In total, twenty older adults, ages 65–84 years and clinically diagnosed with mild to moderate dementia, completed a structural auditory stimulation procedure lasting for 15 minutes per day for 30 consecutive days. Assessments of cognition were completed using the standardized Mini-Cog test, and resulting neural responses were quantitatively examined with electroencephalography (EEG), focusing on gamma-band oscillatory activity. The results demonstrated 40% of participants showed statistically relevant improvements over pre-stimulation Mini-Cog scores, demonstrating improvements in memory, attention, and executive functioning. The EEG data demonstrated adults showed increased gamma-band neural activity following the stimulation as evidenced by increases in all participants at a minimum sensitivity setting of 7.5 µV/mm (to a maximum setting of 10 µV/mm), indicating improved cortical synchrony and neuro-plasticity. Neuro-physiological changes were confirmed as neurologist review of the EEG data confirmed the safety and neurological tolerability of the stimulation. No adverse effects were identified, there were no epileptiform discharges or abnormal slowing, nor other pathological changes (other than one isolated case of mild diffuse slowing). The strong participant compliance and the lack of adverse events emphasize the clinical feasibility of this intervention. Given these initial results, cognitive stimulation using non-invasive auditory stimulation at gamma frequency may provide an effective adjunct treatment to help reduce cognitive impairment in dementia. Future large randomized controlled trials of a longer duration with detailed neuroimaging assessments are needed to further establish these findings.