Rethinking the inhibitory system in the sensory system and descending pain modulation

Abstract

The inhibitory mechanism in the nervous system does not always block the transmitted signal. Lateral inhibition in the information processing of the sense is deeply involved in the mechanism of contrast enhancement. The first report of lateral inhibition was Hartline's study of Limulus lateral eyes. In the human retina, lateral inhibition caused by reciprocal synapses between the photoreceptor and horizontal cells plays a role in reducing the receptive fields of the bipolar cells. In the pain system, a similar mechanism can be used to pinpoint where you feel pain. Periaqueductal gray (PAG), which has reciprocal connections with extensive areas of the brain, is involved in sleep, wakefulness, and regulation of the autonomic nervous system, including the circulatory, respiratory, and thermoregulatory systems. The dorsolateral PAG is involved in the noradrenaline-mediated, and the ventrolateral PAG is involved in the serotonin-mediated descending pain modulation. Both pain and descending pain modulation circuits may be part of the nocifensive response for maintaining homeostasis.