Microstructural analysis of ingestive behaviour reveals no contribution of palatability to the incomplete extinction of a conditioned taste aversion

Abstract

An analysis of the microstructure of licking responses was used to investigate the effects of conditioning and extinguishing a taste aversion. Rats received a single pairing of 8% fructose with lithium chloride (LiCl) while controls received unpaired exposure to fructose and LiCl. Pairing fructose with LiCl produced a reduction both in consumption and in the size of licking clusters. Subsequent exposure to fructose in the absence of LiCl produced some extinction of the taste aversion although at asymptote there was a residual difference in consumption between the taste aversion group and unpaired controls. In contrast the reduction in lick cluster size did completely extinguish. Previous analyses of licking microstructure indicate that lick cluster size is related to the palatability of the ingested solution. Thus these results indicate that although taste aversion learning initially reduces the palatability of the cue solution this reduction is not permanent. These results are discussed with reference to the possibility that preparatory behaviours are more resistant to extinction than are consummatory behaviours.

Keywords:

• Taste aversion
• Licking
• Preference
• Microstructure
• Extinction

Acknowledgments

The experimental work reported here was supported by a Biotechnology and Biological Sciences Research Council (BBSRC) new investigator award to D.M.D. The author would also like to thank Andrew Delamater for raising the implications of two-dimensional concepts of palatability.

Notes

¹ Although there are potential problems with the use of initial lick rate as a measure of palatability in water-deprived animals, it is worth noting that during the current experiment the number of licks in the first 60 s of each trial was lower in group paired than in group unpaired during Extinction Trials 1–8, lowest t (14) = 3.16, p < .001, but there was no difference in initial lick rate during Extinction Trials 9–14, highest t (14) = 1.29, p = .217.