Threat and the Body: How the Heart Supports Fear Processing

Mental processes depend upon a dynamic integration of brain and body. Emotions encompass internal physiological changes which, through interoception (sensing bodily states), underpin emotional feelings, for example, cardiovascular arousal can intensify feelings of fear and anxiety. The brain is informed about how quickly and strongly the heart is beating by signals from arterial baroreceptors. These fire in bursts after each heartbeat, and are quiet between heartbeats. The processing of fear stimuli is selectively enhanced by these phasic signals, and these inhibit the processing of other types of stimuli including physical pain. Behavioural and neuroimaging studies detail this differential impact of heart signals on the processing of salient stimuli, and add to knowledge linking rhythmic activity in brain and body to perceptual consciousness.

Trends

The timing and strength of each heartbeat is signalled in chunks to the brain by arterial baroreceptors. This is the basis of the interoceptive representation of cardiovascular arousal.

Recent studies show that fear signals are judged more fearful during heartbeats (when baroreceptors are activated) than between heartbeats (when baroreceptors are quiescent). At the limit of perception, fear signals are more easily detected during heartbeats than between heartbeats.

The enhancement of fear processing by heartbeats indicates a selective, differential influence of physiology on motivationally relevant functions as the processing of painful stimuli is inhibited by heartbeats.

Physiological fluctuations in the body dictate sensory sampling and the contents of perceptual consciousness.

Characterisation of these selective cardiac interoceptive effects will inform emotional neuroscience and may lead to new treatment approaches for anxiety.