Fear balance is maintained by bodily feedback to the insular cortex in mice.

How does the brain maintain fear within an adaptive range? We found that the insular cortex acts as a state-dependent regulator of fear that is necessary to establish an equilibrium between the extinction and maintenance of fear memories in mice. Whereas insular cortex responsiveness to fear-evoking cues increased with their certainty to predict harm, this activity was attenuated through negative bodily feedback that arose from heart rate decelerations during freezing. Perturbation of body-brain communication by vagus nerve stimulation disrupted the balance between fear extinction and maintenance similar to insular cortex inhibition.

Facial expressions of emotion states and their neuronal correlates in mice.

Understanding the neurobiological underpinnings of emotion relies on objective readouts of the emotional state of an individual, which remains a major challenge especially in animal models. We found that mice exhibit stereotyped facial expressions in response to emotionally salient events, as well as upon targeted manipulations in emotion-relevant neuronal circuits. Facial expressions were classified into distinct categories using machine learning and reflected the changing intrinsic value of the same sensory stimulus encountered under different homeostatic or affective conditions.

Aversive state processing in the posterior insular cortex.

Triggering behavioral adaptation upon the detection of adversity is crucial for survival. The insular cortex has been suggested to process emotions and homeostatic signals, but how the insular cortex detects internal states and mediates behavioral adaptation is poorly understood. By combining data from fiber photometry, optogenetics, awake two-photon calcium imaging and comprehensive whole-brain viral tracings, we here uncover a role for the posterior insula in processing aversive sensory stimuli and emotional and bodily states, as well as in exerting prominent top-down modulation of ongoing behaviors in mice.