Chronic effects of non-invasive audiovisual gamma stimulation on network activity in the aging hippocampus

Brain oscillations are crucial for cognition. In Alzheimer’s disease (AD), disruptions in gamma rhythms have been linked to memory deficits and cognitive decline. Recently, it has been shown that non-invasive audiovisual (AuViS) stimulation at 40 Hz improves pathological symptoms in AD models. Furthermore, it promotes structural plasticity through its positive effects on adult neurogenesis in the aging hippocampus. However, the specific mechanisms by which AuViS induces plastic changes within the circuit and how these modifications can lead to positive behavioral effects remain poorly understood. To assess the impact of AuViS on hippocampal network activity, we performed simultaneous in vivo single-unit and local field potential (LFP) recordings in the CA1 and dentate gyrus subregions of 8-month-old wild type mice exposed to chronic 40 Hz AuViS. We characterized oscillatory power during acute AuViS and free exploration of familiar and novel environments, both before and after six weeks of daily treatment. Preliminary results reveal an enhanced response to the acute stimulation after the treatment, together with lower decay in the endogenous gamma band recorded during spatial exploration. This could be related to similar preliminary observations in human AD patients, describing that AuViS rescues a shift toward lower gamma band, related to disease progression. Finally, we characterized single unit activity during acute stimulation and free exploration.