“…The hindbrain contains the essential motor circuit for producing the emetic reflex (Miller et al, 1994b; Smith et al, 2002), and four neural pathways are known to project to this circuit (Horn, 2008; Horn, 2014): (1) vagal afferents from the gastrointestinal tract, sensitive to mechanical and chemical perturbations, e.g., food poisoning (Hu et al, 2007); (2) input to the VeN from the middle ear, e.g., motion sickness (Yates et al, 1998); (3) AP, an area with a low blood-brain barrier, sensitive to circulating toxins (Miller et al, 1994a); and (4) descending input from the forebrain, potentially responsible for psychogenic or learned emetic responses (Muraoka et al, 1990; Roscoe et al, 2011). An additional possibility, arguably not “normal” sensory activation of of the emetic circuit, would be stimulus actions on the internal components of the emetic system.…”