The insular cortex balances the mind and body’s responses to fear in mice

Within the insular cortex – a small lobe folded deep within the cerebral cortex of the mammalian brain – bodily feedback signals are used to keep fear responses in check, according to a new study in mice. The study revealed the insular cortex’s dual role in either enhancing or weakening the extinction of fear, depending on the internal fear-state of the animal. Fear – the innate response for coping with danger – is essential to survival. However, it needs to be maintained within a functional balance to be healthy. If a fear response is too strong, it can lead to anxiety and stress disorders. Conversely, too weak a response may lead to exaggerated risk-taking. Fear can invoke strong bodily feedback signals, including changes in heart and breathing rates, as well as behavioral (e.g., fight or flight) and emotional (e.g., unpleasant feelings of dread) responses that facilitate self-preservation when faced with danger. However, a true understanding of how the mind and body work together to balance fear within an adaptive range remains elusive. Previous research suggests that the insular cortex (InsCtx) plays a role in processing bodily signals and perhaps fear maintenance and extinction. To investigate whether the InsCtx contributes to fear regulation, Alexandra Klein and colleagues used a mouse model. Through a series of conditioned fear experiments, they found that the InsCtx plays an important parallel role in either enhancing or suppressing fear. According to Klein et al., InsCtx function depended on bodily feedback signals. For example, fear-induced freezing behavior was associated with a slowed heart rate, which in turn dampened fear-evoked activity in the insular cortex, keeping the fear response in check and within an adaptive range. The findings illustrate how the InsCtx integrates opposite fear-associated sensory and bodily signals necessary for fear regulation. “The work of Klein et al. underscores the importance of a holistic, ‘mind, brain and body’ approach to understanding emotion and provides a template for future basic science to uncover how complex states associated with pain and sickness interact with mental processes,” writes John Christianson in a related Perspective.