SEARCH RESULTS FOR: Neuroanatomy-and-Physiology-of-Fear

Neuroanatomy and Physiology of Fear

Neuroanatomy and Physiology of Fear Sensory receptors detect an environmental stimulus (e.g., photoreceptors detect a snake-like image) Olfaction: olfactory bulb sends direct input to subcortical & cortical pathways Sight, sound, touch, & taste: thalamus† pre-processes & relays sensory information to subcortical & cortical pathways Authors: Taryn Stokowski Andrea Moir Reviewers: Erika Russell Usama Malik Emily J. Doucette Brienne McLane* * MD at time of publication Subcortical pathway (12 ms) Amygdala† initiates defensive response Nucleus accumbens (ventral basal ganglia) integrates input to bias selection of active (fight/flight) or passive (freeze) responses via ventral pallidum Periaqueductal gray (PAG) coordinates motor response Hypothalamus† coordinates the corresponding autonomic & hormonal responses Somatic motor system Medulla oblongata relays stimulation Endocrine system PAG activates brainstem motor nuclei & spinal cord Autonomic system Active only: hypothalamus† secretes corticotropin- releasing hormone Pituitary gland If active or releases If active early passive If passive adrenocorticotropic (dorsal If passive (sympathetic): (para- hormone** PAG): (ventral adrenal gland sympathetic): rapid, PAG): releases vagus nerve muscle whole- adrenaline releases Adrenal cortex releases cortisol activation body acetylcholine muscle tension Energy sustained (e.g, ↑ blood glucose) Defensive movement (e.g, startle or flee) Systemic physical response (e.g, ↑ heart rate) Cortical pathway (300 ms) Sensory cortices analyze the stimulus in detail (e.g., visual cortex determines that a coiled object is in view) Association areas in the parietal, temporal, and frontal lobes categorize the object based on previous knowledge (e.g., could this be a garden snake?) Insular cortex detects interoceptive information (e.g., awareness of racing heart) Hippocampus† uses memory to assign contextual meaning (e.g., has this type of snake harmed me before?) Prefrontal cortex (PFC) integrates interoceptive, sensory, & memory information to respond to stimulus Ventromedial PFC & anterior cingulate cortex† assess emotional salience & modulate subcortical response (e.g., ↓ arousal) Subjective experience of fear (e.g., I feel scared by that garden snake!) Emotion is regulated (e.g., body relaxes) †Part of the Limbic System **See corresponding Calgary Guide slide Note: This slide is based on the Two-System Framework by LeDoux & Pine (2016) Legend: Complications Published July 19, 2025 on www.thecalgaryguide.com Pathophysiology Mechanism Sign/Symptom/Lab Finding