A pathway through the LHb has recently been shown to be involved in the expression of learned helplessness (B. Li et al., 2011; K. Li et al., 2013), a model of depression in which animals previously exposed to an inescapable aversive stimulus show diminished escape behavior when the stimulus is avoidable (Maier, 1984; Maier and Watkins, 2005; Duman, 2010). Here, LHB is linked to major depressive disorder.