Trkb. t1 overexpression impairs both long-term potentiation and long-term depression ([53,54], but see [55]) and reduces BDNF [56], which could potentially account for a transition away from hippocampal-dependent action selection to habit-based behaviors, which are instead associated with dorsolateral striatal and cortical sensorimotor systems [11–13,23,25]. The gene discussed is BDNF; the disease is major depressive disorder.