PTN and Anxiety: Nevertheless, our findings that PTN KOs exhibit heightened anxiety, perhaps particularly in novel contexts, suggests that future assessment of PTN KOs' behavior should involve use of less anxiogenic paradigms when possible and when indicated by the hypotheses under study, e.g. the T-maze [45] and attention set-shifting tasks [46] instead of or in addition to paradigms like the Morris water maze, which are known to evoke anxiety [30].