Chemogenetic manipulation of learning-tagged neurons is sufficient to rescue progressive memory deficits in a mouse model of Alzheimer's disease

INTRODUCTION Alzheimer's disease (AD) primarily affects episodic memory, which relies on the medial temporal lobe, including the hippocampus and lateral entorhinal cortex (LEC). However, it remains unclear whether memory deficits in AD reflect disrupted encoding of new experiences or impaired retrieval of previously stored information. METHODS APPJ20 transgenic mice were used to investigate memory deficits. Neuronal populations activated during the learning phase of associative and non-associative tasks were tagged to express the excitatory chemogenetic receptor hM3Dq. Chemogenetic activation of these tagged neurons was performed during the recall phase of the tasks. RESULTS Chemogenetic reactivation of LEC or dentate gyrus (DG) learning-tagged neurons rescued memory performance in associative and non-associative tasks, respectively. Neuronal activation, assessed using c-Fos as a marker, revealed a specific deficit in the reactivation of neurons recruited during learning. DISCUSSION Chemogenetic reactivation of neuronal ensembles in the LEC and DG restored memory performance, suggesting that memory deficits in APPJ20 mice are associated with a failure in the endogenous reactivation of learning-relevant neurons.