Topic: threat imminence

The neuromodulator dopamine has qualities of a prediction error in temporal difference (TD) models of reward learning. However, the neuromodulatory substrates of threat prediction errors have remained elusive. Norepinephrine (NE) is released by surprise and uncertainty, and causal manipulations demonstrate a role for NE in threat learning. Thus, we hypothesized that NE encodes a threat prediction error signal, and compared NE release measurements in mice undergoing threat learning with predictions of TD learning. NE release scales with the strength of fear associations and threat imminence. Ho

Defensive brain states, such as fear and anxiety, evolved as mediators of multidimensional reactions to threat, which encompass integrated autonomic, behavioral and endocrine responses. Multiple interconnected brain structures have been involved in defensive reactions, in particular the midbrain’s periaqueductal gray (PAG), the amygdala, and different cortical areas such as the auditory and prefrontal cortices, together processing information at multiple levels of the neuraxis. Several roles pertaining to higher-order threat processing have been assigned to the medial prefrontal cortex (mPFC),