Experimental paradigm: in vitro whole cell patch clamp recordings of layer 3 frontal cortex pyramidal neurons.Findings: increased excitability both in early and advanced tauopathy. Depolarized resting membrane potential, an increased depolarizing sag potential and increased action potential firing rates—all indicative of hyperexcitability. Hyperexcitability reversed by suppression of human mutant tau transgene. Here, MAPT is linked to tauopathy.