Conditioning-testing Paradigm Research Articles

Response properties of neurons in trigeminal nucleus caudalis to noxious and innocuous stimuli under chloralose anesthesia

The response properties of a population of neurons in trigeminal nucleus caudalis, responsive to electrical stimulation of the dental pulp, were quantitatively studied in cats under chloralose anesthesia. A considerable difference was noted between the firing patterns of these units, as identified by poststimulus time histogram analysis, and a group of pulpal units previously studied by others in rostral trigeminal nuclei also under chloralose anesthesia. No specific firing pattern characterized unit response to noxious as opposed to innocuous stimuli in this study. However, patterns of stimulus interaction, identified using a conditioning-testing paradigm, were identical in this study to those reported rostrally. A portion of the units identified in nucleus caudalis possess the firing characteristics required of a population of neurons which might secondarily activate more rostral cells differentially in response to noxious and innocuous stimuli. It is concluded that all the components predicted by a theory of facial sensation based on interdependence of trigeminal primary relay nuclei were shown to exist within the trigeminal brain stem complex.