Walsh & Hoyt: Supranuclear Pathways Mediating Tear Secretion

The cerebral structures and pathways supporting emotional tearing include cortical, limbic, and hypothalamic systems that discharge through descending hypothalamotegmental pathways to the parasympathetic lacrimal nuclei of the pons. Experimental study of these systems is limited by the fact that psychic tearing is a function unique to humans. Pfuhl suggested that psychic lacrimation results from stimulation of the frontal cortical fields responsible for eye motion (the second frontal convolution). In cats, direct projections were demonstrated to the superior salivatory nucleus from the amygdala, a region in the anterior temporal lobe that is involved in emotional regulation. It is noteworthy that these projections did not pass through hypothalamic synapses, suggesting that lacrimation can be directly affected by the cerebral cortex. Takeuchi et al. and Botelho et al. stated that psychogenic tears may be decreased or increased by lesions of the frontal cortex, basal ganglia, or hypothalamus. Mizukawa et al. reported that stimulation of the ventromedial hypothalamic nucleus of the rabbit causes lacrimation.