Representation of capsaicin-evoked urge-to-cough in the human brain using functional magnetic resonance imaging

RATIONALE: Coughing in humans is typically preceded by a desire (or urge) to cough. The neural circuitry involved in sensing airway irritation and generating the urge-to-cough in humans is essentially unknown. OBJECTIVES: The aim of the present study was to use functional brain imaging to describe the supramedullary regions that are activated in humans during capsaicin inhalation. METHODS: Experiments were performed on 10 healthy subjects (5 males, 5 females). Capsaicin doses were individually tailored to evoke a transient and reversible urge-to-cough. Blood oxygen level-dependent (BOLD) functional magnetic resonance measures were collected during repeated 24-second challenges with capsaicin or saline inhalation and subjects were asked to rate the urge-to-cough intensity of each challenge. MEASUREMENTS AND MAIN RESULTS: Capsaicin inhalation reliably evoked an urge-to-cough, which was associated with activations in a variety of brain regions, including the insula cortex, anterior midcingulate cortex, primary sensory cortex, orbitofrontal cortex, supplementary motor area, and cerebellum. CONCLUSIONS: These data provide the first insights into the cortical neuronal network involved in sensing airway irritation and modulating coughing in humans.