Gamma-patterned sensory stimulation reverses synaptic plasticity deficits in rat models of early Alzheimer's disease

Abstract

Non-invasive sensory stimulation in the range of the brain’s gamma rhythm (30-100 Hz) is emerging as a new potential therapeutic strategy for the treatment of Alzheimer’s disease (AD). Here we investigated the effect of repeated combined exposure to 40 Hz synchronized sound and light stimuli on hippocampal long-term potentiation (LTP) in vivo in three rat models of early AD. We employed a very complete model of AD amyloidosis, amyloid precursor protein (APP)-overexpressing transgenic McGill-R-Thy1-APP rats at an early pre-plaque stage, systemic treatment of transgenic APP rats with corticosterone modelling certain environmental AD risk factors and, importantly, intracerebral injection of highly disease-relevant AD patient-derived synaptotoxic beta-amyloid and tau in wild-type animals. We found that daily sessions of 40 Hz sensory stimulation fully abrogated the inhibition of LTP in all three models. Moreover, there was a negative correlation between the magnitude of LTP and the level of active caspase-1 in the hippocampus of transgenic APP animals which suggests that the beneficial effect of 40 Hz stimulation was dependent on modulation of pro-inflammatory mechanisms. Our findings support ongoing clinical trials of gamma-patterned sensory stimulation in early AD.

Gamma sensory stimulation and effects on the brain

“…Previous findings, by our lab and others, have shown effects of 40 Hz stimulation on a wide array of phenotypes in neurodegenerative disease, including protein clearance, synaptic potentiation, autophagy, glial activation, inflammatory changes, and vascular responses [1][2][3]7,8,25,26 . These effects may be indirect from the neural response to gamma stimulation, but it is unclear how neural response to sensory stimulation is coupled to biological pathways related to pathology.…”