Pain research, accelerated in recent decades through refined morphophysiological studies in experimental animals and through precise psychophysical measurements in man, anticipates significant progress from bridging the animal-human gap through combining microneurography (MNG) and microstimulation (INMS). This method allows to explore, at the unitary level in experiencing human subjects, the neurophysiological basis both for encoding stimuli at the periphery and for decoding sensations cognitively. Using safe intraneural microelectrodes, we record nerve signals from identifiable single sensory units in awake subjects, and map their peripheral receptor site. We selectively impose a choice of nerve signals upon identified sensory channels via intraneural microstimulation. We then question the brain about the cognitive characteristics of the sensation evoked. Fundamental knowledge has thus emerged about subjective attributes of elementary sensations evoked from single low threshold mechanoreceptor units innervating the human hand. For example (1) what determines the subjective sensory quality; (2) how afferent input parameters contribute to the subjective magnitude; and (3) how accurately is sensory localization function resolved. Preliminary data on nociception and pain, also contributed through combined MNG/INMS, guarantees feasibility and relevance at basic and clinical levels for a follow-up project involving high threshold sensory systems in man. The present proposal for continuation pursues expansion of our preliminary MNG/INMS research on (1) laws that normally govern cognition of quality, magnitude and localization of pain and itch; (2) pathological deviations of somatosensory quality whereby mild stimuli cause pain (hyperalgesia, allodynia); and (3) mechanisms of pain, spontaneous or sympathetic-dependent, in patients with neuropathy.
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