ABSTRACT

This chapter describes what is known regarding state-specific modulation of ascending sensory transmission by outlining electrophysiological recording studies in the trigeminal sensory nuclear complex (TSNC) and spinal cord of chronically instrumented, unanesthetized animal preparations. Sensory tracts that arise from the regions receive a multitude of ascending and descending input and convey an array of sensory modalities. A simple method for assessing aggregate TSNC excitability changes across behavioral state is to measure alterations of electrical field potentials within the region. Field potentials evoked by electrical stimulation of nerve trunks or receptive fields represent the summed activity of a population of trigeminal sensory neurons in the vicinity of the electrode tip. Several techniques for recording activity of lumbar sensory neurons have been described in the literature since the late 1960s. Thus, lumbar restraint has been employed and considered essential for minimizing spinal cord movement and for allowing the investigator to record from lumbar sensory neurons.