We aim at increasing current knowledge of the neurophysiological basis of cognitive sensation by studying, in human health and disease, the correlations between activity in single sensory nerve fibers and sensory experience. We will use the exclusive Vallbo-Hagbarth microneurographic technique to record activity in indentifiable single afferent nerve fibers from intact nerves in alert subjects, complemented with our own technique of intraneural microstimulation (INMS). The combined strategy allows controlled activation of the whole spectrum of sensory channels on a single unit basis. Psychophysical studies can be performed on the quality (submodality), magnitude, temporal profile and referred localization of unitary sensations evoked by INMS. The identity of the type of sensory unit excited and the actual location of its receptive field can be established by electrophysiologically "marking" the nerve fiber stimulated and by subsequent testing of its receptor characteristics and conduction velocity. Fundamental questions outstanding in neurology, neurophysiology, and psychology are now being answered by combined microneurography/INMS. For example, a) a description of the inventory of pure sensations related to activity in the range of a single sensory channels, b) a description of their distinct psychophysical temporal and magnitude profiles relative to afferent impulse frequency, c) identification of enhancing or suppressing interactions between the inputs of different sensory channel types... In the field of abnormal sensation the combined strategy emerges as the long awaited means to explore the neural basis of positive sensory phenomena of peripheral sensory unit origin, like neuropathic pains and paresthesias. Implementing a rigorous research project to expand our present studies should yield further knowledge on the principles governing how the sensory apparatus works and fails. It is hoped that a better understanding of the pathophysiology of sensory cognition will help develop scientific approaches towards prevention and therapy of abnormal sensation.