Executive dysfunction is associated with altered hippocampal-prefrontal functional connectivity in male 3xTg Alzheimer's model mice

Executive function depends on connectivity between the ventral hippocampus and medial prefrontal cortex (mPFC). How abnormalities in this pathway lead to cognitive dysfunction in Alzheimers disease (AD) have yet to be elucidated. Here, male 3xTg AD mice at 6-months displayed maladaptive decision-making in the rodent 4-Choice Gambling Task measure of executive function. Extracellular field recordings in the infralimbic cortex at this age showed layer-specific reductions in response amplitude and paired-pulse ratio following activation of hippocampal input fibres, indicating changes to short-term hippocampal-prefrontal synaptic plasticity. Bulk RNA sequencing of the mPFC in 6-month-old mice identified differential gene expression changes associated with calcium ion transport, glutamatergic, GABAergic, and dopaminergic neurotransmission. Seven of these genes (Gpm6b, Slc38a5, Ccr5, Kcnj10, Ddah1, Gad1, Slc17a8) were also differentially expressed in 3-month mice. These results reveal a pre-clinical deficit in executive function correlating with synaptic plasticity and gene expression changes in the mPFC of male 3xTg mice.