A prefrontal cortex–brainstem neuronal projection that controls response to behavioural challenge

The prefrontal cortex (PFC) is thought to participate in high-level control of the generation of behaviours (including the decision to execute actions); indeed, imaging and lesion studies in human beings have revealed that PFC dysfunction can lead to either impulsive states with increased tendency to initiate action, or to amotivational states characterized by symptoms such as reduced activity, hopelessness and depressed mood. Considering the opposite valence of these two phenotypes as well as the broad complexity of other tasks attributed to PFC, the authors sought to elucidate the PFC circuitry that favours effortful behavioural responses to challenging situations. Here they develop and use a quantitative method for the continuous assessment and control of active response to a behavioural challenge, synchronized with single-unit electrophysiology and optogenetics in freely moving rats. In recording from the medial PFC (mPFC), they observed that many neurons were not simply movement-related in their spike-firing patterns but instead were selectively modulated from moment to moment, according to the animal’s decision to act in a challenging situation. Surprisingly, they next found that direct activation of principal neurons in the mPFC had no detectable causal effect on this behavior. 

Melissa R. Warden,  et al.
Nature (2012) doi:10.1038/nature11617,  Published online 18 November 2012