Components of the Fear System and Real-World Evidence for Sex Differences in Fear

Abstract

We begin by briefly outlining how we detect, interpret and respond to fearful stimuli. The fear system involves numerous complex interactions between subsystems serving different functions (Adolphs, 2013; LeDoux, 2012) and it is beyond the scope of this thesis to outline every specific component (specific neuroarchitecture will only be detailed where necessary). The fear system, explained briefly, works in a series of steps. Firstly, sensory detection and identification of threat gives rise to activation of the sympathetic nervous system and automatic behavioural responses (fleeing, freezing, fighting). Continued feedback from the peripheral to the central nervous system allows for moment-to-moment fine tuning of the response for as long as the threat persists. Neurotransmitters control arousal, and connectivity within and between brain circuits. Multiple cortical regions are involved synchronously in evaluating threatening stimuli, experiencing conscious awareness of fear, the regulation of fear levels, monitoring cognitive resources and action planning. Attention is focused (and if necessary sustained) on the potential threat and memory is enhanced for contextual cues associated with it, allowing more effective responses should the threat reoccur. The subjective, phenomenological (lived) experience of fear is also an output of one or more of these processes.