Specialized Neurons in the Medullary Dorsal Horn and the Somatosensory Cortex Involved in the Perception of Pain

Abstract

Research findings have suggested that there are specialized neurons in the peripheral and central nervous system that encode stimulus intensity in the noxious heat range and provide information about the sensory-discriminative aspects of pain. However, almost all studies of central nervous system nociceptive pathways have been performed in anesthetized animals where the transmission of information about tissue damage is suppressed. Sensation is an active process. Perception is dependent not only on stimulus features, but also on the behavioral context in which a stimulus is received. We have studied the activity of single neurons in behaving animals trained in sensory detection and discrimination tasks (Hoffman et al., 1981; Bushneil et al., 1984; Kenshalo et al., 1988; Dubner et al., 1989; Maixner et al., I989). Monkeys were trained to detect noxious thermal stimuli and we utilized this model to study neuronal activity associated with the behavior. In this paper, we will describe our findings on the role of medullary dorsal horn neurons and primary somatosensory cortex (SI) neurons in the perception of noxious stimuli.