Behavioral Ncuroscience Copyright 1988 by the American Psychological Association, Inc. 1988, Vol, 102, No. 6, 942-952 0735-7044/88/S00.75 Taste Reactivity as a Dependent Measure of the Rapid Formation of Conditioned Taste Aversion: A Tool for the Neural Analysis of Taste-Visceral Associations Alan C. Spector, Paul Breslin, and Harvey J. Grill University of Pennsylvania Several explanations may account for deficits in the ability of animals to form taste aversions following neural manipulations. These encompass impairments in conditioned stimulus (CS) and unconditioned stimulus (US) processing, conditioned response (CR) measurement, and expression, memory, and taste-visceral integration. A behavioral procedure that aids in the distinction between some of these possibilities is presented. In Experiment 1, 10 rats received seven intraoral (IO) infusions of sucrose (30 s, 0.55 ml) spaced every 5 min starting immediately after the injection of 3.0 mEq/kg of lithium chloride (LiCl). Control rats (n = 12) were treated identically except that they were injected with sodium chloride (NaCl). Oromotor and somatic taste reactivity behaviors were videotaped and analyzed. Lithium-injected rats systematically decreased their ingestive taste reactivity behavior over time, whereas aversive behavior increased. Control rats maintained high and stable levels of ingcslive responding and demonstrated virtually no aversive behavior over the 30-min period following sodium injection. Rats were tested several days later for the presence of a conditioned taste aversion (CTA). Rats previously injected with lithium during sucrose infusions demonstrated significantly more aversive behavior than the control group, which demonstrated none. There were no differences in the level of ingestive behavior displayed by the two groups on the CTA test. Experiment 3 revealed that when similarly treated rats were tested for a CTA while in a lithium-induced state, a difference in the ingestive behavior between the two groups was observed. In Experiment 2, naive rats were injected with either NaCl or LiCl but did not receive their first sucrose infusion until 20 min later. These rats also received sucrose infusions at 25 and 30 min postinjection. There were no differences in the taste reactivity behavior displayed by lithium- or sodium-injected rats during any of the sucrose infusions. Collectively, these findings indicate that rats dramatically change their oromotor responses to sucrose during the period following LiCl administration, provided that the infusions start immediately after injection. Furthermore, this time-related behavioral change is predomi- nantly attributable to associative processes. This paradigm can be useful in distinguishing between neural manipulations that affect the establishment of taste-visceral associations from others that affect the animal's ability to retain such associations over the commonly employed 24-hr conditioning-test interval. When the consumption of a distinctly flavored fluid is conditioning; the flavored solution serves as the conditioned immediately followed by the administration of a toxin, rats stimulus (CS), the toxin serves as the unconditioned stimulus avoid ingesting this fluid on future presentations (Garcia, (US), and the avoidance behavior serves as the conditioned Kimeldorf, & Koelling, 1955; see also Riley & Clarke, 1977). response (CR). This alteration in behavior is referred to as conditioned taste An understanding of the neural mechanisms underlying aversion (CTA) and is considered to be a form of classical this type of integration between taste and visceral signals has been the goal of a variety of studies (see Ashe & Nachman, This research was supported in part bv grants from the National 198 °; Gatson > 1978 )- Indeed ' a host of neural lesions have Institutes of Health awarded to the first author (F32-NS07915 A) and been reported to attenuate or abolish CTA learning in rats. the third author (RO1-AM21397), as well as a postdoctoral fellowship These include lesions of the area postrema (e.g., Berger, Wise, from the MacArthur Foundation awarded to the first author. & Stein, 1973; Ossenkopp, 1983; Rabin, Hunt, & Lee, 1983), Portions of this work were presented at the Annual Meeting of the parabrachial nucleus (Schulkin, Flynn, Grill, & Norgren, Eastern Psychological Association, April 1986, and the Sixteenth 1985), amygdala (e.g., Nachman & Ashe, 1974; Simbayi, Annual Meeting of the Society for Neuroscience, November 1986. Boakes, & Burton, 1986), gustatory neocortex (eg, Braun We would like to thank Robert A. Rescorla and Gary Schwartz for j^^^ & Keifer> , 982; Lasiter> Deems & Glanzmari) , 9g5)) then- comments on an earlier version of this manuscript We would v£ntral posteromedial nucleus of lhe thalamus (Lasiterj , 985) also like to thank Francis W. Flynn and Terry Davidson for their ,. . . „. ,. . . . ' ... ' helpful advice during the course of this research. We acknowledge ** wel1 ** * romc supracolhcullar decerebration (Gnll & the assistance of Susan Barasch in the data collection. Norgren, 197s). Correspondence concerning this article should be addressed to Whenever a neural manipulation disrupts an animal's ami- Alan C. Spector, Department of Psychology, 3815 Walnut Street, ity loform a taste aversion, at least five possible explanations University of Pennsylvania, Philadelphia, Pennsylvania 19104. may account for the apparent deficit. First, it is possible that 942