Visual entrainment responses are altered in patients with mild cognitive impairment and Alzheimer’s disease

Abstract

AbstractBackgroundAlzheimer’s disease (AD) is the most common cause of dementia in later life. AD is histologically characterized by the accumulation of extracellular amyloid‐β (Aβ) plaques and intracellular hyperphosphorylated‐tau neurofibrillary tangles. Recent research has indicated that visual entrainment may be useful in clearing Aβ‐ and tau‐load in the central nervous system in mouse models of AD. However, human studies in this area are rare and the degree to which patients with AD exhibit aberrations in visual entrainment are unknown, as is the impact of entrainment on amyloid and tau‐load.MethodWe recorded magnetoencephalography (MEG) during a 15‐Hz visual entrainment paradigm in amyloid‐positive patients on the AD spectrum and compared their neural responses to biomarker‐negative, demographically‐matched, cognitively‐normal controls. MEG data were imaged using a beamformer and virtual sensor data were extracted from the peak responses.ResultOur results indicated that participants on the AD spectrum exhibited significantly stronger entrainment relative to baseline in primary visual cortices. However, interestingly, the two groups exhibited roughly equal absolute levels of entrainment, which suggests lower spontaneous levels of 15‐Hz activity in the AD spectrum group. Additionally, we found that higher absolute levels of entertainment predicted greater MoCA scores.ConclusionThis pattern of results indicates that the increased entrainment in patients on the AD spectrum was compensatory and that those patients who were closer to the level seen in controls had better cognitive performance. Overall, these results indicate that entrainment may be altered in humans with AD and should be further examined in future studies.