Taste sensitivity in rats with lesions of the thalamic gustatory nucleus

Rats trained to detect 100 mM NaCl and 300 mM sucrose received lesions of the thalamic gustatory nucleus (VPMpc) and then were tested for their absolute NaCl and sucrose thresholds. Most rats with small lesions or lesions posterior to VPMpc had excellent retention of the detection tasks and normal thresholds. Those with less than total destruction of VPMpc had poor retention and significantly higher thresholds than controls. Rats with essentially complete lesions of VPMpc had no retention and demonstrated little or no ability to detect these stimuli even after retraining on higher concentrations. These results indicate that VPMpc may play a critical role in the detection of taste stimuli. The results of additional analyses suggest that poor performance of rats with less than total VPMpc lesions is due to a combination of a decrease in taste sensitivity and a decrease in the salience of the taste cue.