Intensity coding in the transient portion of the rat chorda tympani response

For assessment of the relative importance of the transient and steady state components of the chorda tympani response to intensity coding of gustatory stimuli, the rat's ability to discriminate aversive solutions following adaptation was compared with changes in the neural response also resulting from adaptation. A taste aversion was conditioned to .9% NaCl, and subsequent acceptance of several NaCl concentrations (range: .1%-1.5%) was tested following infusion of 1 ml of adapting solution (H2O or .1%, .9%, or 1.5% NaCl) through an intra-oral cannula. Adaptation significantly decreased gustatory intensity discrimination and decreased the magnitude of the transient portion of the chorda tympani response. The degree of reduction in transient magnitude correlated significantly with reduced discrimination in all adapting conditions. However, the magnitude of the steady state response negatively correlated with discrimination. These data suggest that gustatory intensity discrimination depends upon information contained in the transient portion of the neural response and that the transient is necessary as well as sufficient for taste intensity discrimination.