Effects of lesions of the gustatory neocortex on taste aversion learning in the rat.

In 5 experiments, 110 normal male Long-Evans hooded rats and 125 Ss with lesions of the gustatory neocortex (GN) were compared for their ability to learn aversions to taste cues paired with toxicosis. When the taste presentation was followed immediately by toxicosis, normal Ss and 8 Ss with lesions of the posterior (visual) neocortex learned aversions to sucrose, sodium chloride, quinine hydrochloride, and hydrochloric acid solutions. Ss with GN lesions learned aversions to all solutions except sucrose. In preference tests, all solutions were shown to be discriminable from water by both normal and GN-lesioned Ss. Under conditions in which a 6-hr delay separated taste presentation and toxicosis, normals again learned specific aversions to all 4 solutions, but Ss with GN lesions failed to learn specific aversions to sucrose, sodium chloride, and hydrochloric acid solutions. It was shown that the ability of Ss with GN lesions to learn aversions to sucrose and quinine depended on stimulus concentration. It is proposed that the data can be accounted for by postulating a change in the threshold for taste illness associations following GN lesions. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ingestive responses of human newborns to salty, sour, and bitter stimuli.

In 2 experiments a total of 204 16-90 hr old neonates were offered 2 fluids differing in taste for 3 min each. The volumes ingested were measured. Ss offered water and bitter and sour solutions did not ingest them differentially, which corroborated earlier observations with weaker solutions. A sucrose solution was used to raise baseline ingestion above that of water. Ss offered the sucrose solution with and without urea, citric acid, or sodium chloride consumed less of it when citric acid was added. They were indifferent to the addition of urea or sodium chloride. The failure to observe intakes lower than that of water suggests that newborns maximally inhibit their ingestion of water. The effect of sex, age, birth weight, and individual consistency on intake were assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste as a dipsogenic stimulus.

Studied solution drinking in 50 male, nondeprived, Sprague-Dawley albino rats to determine how much animals will drink for reasons of taste alone. 4 different taste stimuli (sucrose, glucose, sodium saccharin, and sodium chloride) were used, each covering a wide range of concentrations. The same Ss were then retested after 16 hr. of water deprivation, and intakes under deprived and nondeprived conditions were compared. Results show that Ss ingested large volumes of sweet solutions in the absence of any need, and that water deprivation added only a small increment to the already high intakes of sweet solutions. Sodium chloride solutions, on the other hand, were ingested in relatively small quantities by nondeprived Ss, but water deprivation produced a large increase in intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavior of sodium-deficient rats: The search for a salty taste.

Tested whether 188 Na-deficient rats would search for the taste of Na or the taste of salt. Ss were subjected to various conditions of food and water deprivation before being given a choice between solutions of varying saltiness. Na-deficient Ss displayed an appetite for solutions that humans judged as salty-tasting whether or not the solutions contained sodium salts. When offered a choice between a pair of sodium salts, Ss generally preferred the more salty-tasting solution. They tended to do the same for a pair of nonsodium salts and for a pair of sodium and nonsodium salts. Results show that human psychophysical judgments of saltiness are a good predictor of the choices that rats will make when Na-deficient. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alcohol aversion generalization in rats: Specific disruption of taste and odor cues with gustatory neocortex or olfactory bulb ablations.

Rats with ablations of the gustatory neocortex (Experiment 1) and rats with olfactory bulb ablations (Experiment 2) were compared with normal rats for aversion generalization to both single taste solutions (sucrose, sodium chloride, quinine hydrochloride, hydrochloric acid) and compound taste solutions (pairs of the four single tastants) following alcohol aversion training. All rats acquired equal and strong alcohol aversions. Control rats showed consistent aversion generalization to both the sucrose plus quinine and the sucrose plus hydrochloric acid solutions; no significant generalization occurred to the single tastants except a weak generalization to sucrose in Experiment 2. Rats with gustatory neocortical ablations failed to show aversion generalization to any of the taste solutions. Rats with olfactory bulbectomies displayed the same aversion generalization functions as control rats but exhibited significantly faster extinction of the alcohol aversion than did the trained control rats. Results from the present experiments suggest that during alcohol aversion learning, rats lacking gustatory neocortex use odor cues (no taste generalization), whereas rats lacking olfactory bulbs utilize taste cues (normal taste generalization). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depressive symptoms and alterations in sucrose taste perception: Cognitive bias or a true change in sensitivity?

Examined whether changes in response bias and/or sucrose detection thresholds were associated with symptoms of depression. Ss were 49 18–34 yr old undergraduates and 1 52-yr-old outpatient who had been diagnosed with major depressive episode. Sucrose detection thresholds were measured (1) in Ss with high and low Hamilton Depression Rating Scale (HAM-D) scores who did not meet standard criteria for current Major Depressive Episode (MDE); and (2) in Ss who did fulfill standard criteria for MDE. Ss with low HAM-D scores produced significantly more false alarms than the other 2 groups but taste sensitivity did not vary significantly across groups. Results suggest that changes in response bias underlie previously reported increases in sucrose taste thresholds in depressed Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of illness in producing learned taste aversions in rats: A comparison of several rodenticides.

Compared several toxic agents to test the effect of various types of illness in producing learned taste aversions. Ss in 2 experiments were 90 female and 26 male Sprague-Dawley rats. After a 10-min sucrose drinking trial, groups of Ss were injected ip with lithium chloride or with a strong, near lethal dose of a rodenticide. Strong sucrose aversions were acquired by groups injected with lithium chloride, copper sulfate, sodium fluoroacetate, or red squill, and very weak or no aversions were learned by groups injected with thallium, warfarin, cyanide or strychnine. Results are discussed in terms of onset of symptoms, duration of symptoms, and kinds of physiological effects necessary to produce aversions. It is concluded that the effects of different drugs may be mediated by different physiological systems in producing learned taste aversions. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste reactivity as a dependent measure of the rapid formation of conditioned taste aversion: A tool for the neural analysis of taste-visceral associations.

Investigated the ability of animals to form taste aversions following neural manipulations. In Exp 1, 10 rats received intraoral infusions of sucrose every 5 min starting immediately after the injection of LiCl. 12 controls were injected with NaCl. Oromotor and somatic taste reactivity behaviors were videotaped and analyzed. Lithium-injected Ss decreased their ingestive taste reactivity over time; aversive behavior increased. Controls maintained high levels of ingestive responding and demonstrated virtually no aversive behavior following sodium injection. Ss were tested several days later for a conditioned taste aversion (CTA). Rats previously injected with lithium demonstrated significantly more aversive behavior than controls. Exp 3 revealed that when similarly treated rats were tested for a CTA while in a lithium-induced state, difference in the ingestive behavior was observed. In Exp 2, naive rats were injected with NaCl or LiCl but did not receive their 1st sucrose infusion for 20 min. Ss also received infusions at 25 and 30 min postinjection. There were no differences in the task reactivity behavior displayed. Rats dramatically changed their oromotor responses to sucrose during the period following LiCl administration, provided the infusions started immediately after injection, a change attributable to associative processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peers as mediators of television food advertisements aimed at children.

Past research on the effects of TV has focused primarily on it as a unitary force rather than as 1 source of influence in a network of cross-pressures. The present study attempted to determine how peer-modeled food preferences combined with TV food commercials to influence the food preferences of school-aged children. 40 Black and 40 White 4th graders were assigned randomly to 1 of 4 conditions: TV control, TV advertisements with similar peer-modeled food preferences, and TV advertisements with dissimilar peer-modeled food preferences. An additional 40 children served as peer models. Ss in the TV advertisement condition preferred foods in the same class as the advertised foods more frequently than did Ss in the TV control condition. Ss in the TV advertisement/peer-similar condition preferred foods like the advertised food more often than Ss in the TV advertisement condition, whereas Ss in the TV/peer-dissimilar condition preferred foods like the advertised food less frequently than did Ss in the TV advertisement condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of sodium- and calcium-deficient rats to acquire conditioned taste aversions to the object of their specific hunger.

Attempted to condition taste aversions to the objects of 2 mineral-specific hungers in 2 experiments with a total of 116 male Sprague-Dawley rats. Both the innate preference of adrenalectomized Ss for sodium and the learned preference of parathyroidectomized Ss for calcium were studied. None of the sodium-deficient Ss poisoned after drinking NaCl reached a taste-avoidance criterion, even after 9 pairings of salt ingestion with aversive lithium chloride injections. 6 of 11 calcium-deficient Ss did not meet the salt-avoidance criterion after 10 pairings. Nondeficient control Ss learned to avoid these salt solutions completely after an average of only 3 such pairings. Besides unmasking a surprising degree of similarity between the learned and innate specific hungers studied, results clearly demonstrate a powerful influence of physiological need on aversion conditioning. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of basolateral amygdala lesions on taste aversions produced by lactose and lithium chloride in the rat.

In Exp I, 24 intact male Lister rats were given either lactose or sucrose solutions. Although on 1st exposure they readily consumed lactose, its ingestion produced a conditioned taste avoidance (CTA) that was partly extinguished by repeated sucrose exposure after lactose conditioning. In Exp II, 8 Ss with large bilateral electrolytic lesions of the basolateral amygdala and 10 with either sham or no operations were given 2 pairings of saline with LiCl injections (upper gastrointestinal tract discomfort) and, in a separate condition, access to high levels of lactose (lower gastrointestinal tract discomfort). CTAs were measured both by 2-bottle tests and by video recordings of orofacial and somatic responses. The lesions attenuated LiCl-induced but not lactose-induced CTA, results demonstrating that a CTA can occur without the basolateral amygdala. Findings suggest that aversions based on distaste can be distinguished from avoidances based on danger, not only in terms of orofacial responses but also in terms of their neuroanatomical substrate. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hunger enhances the expression of calorie- but not taste-mediated conditioned flavor preferences.

Compared ethanol-mediated flavor preferences to preferences mediated by saccharin, which is sweet but noncaloric, and sucrose, which is both sweet and caloric in 4 experiments, using 74 Long-Evans rats. Ss learned to associate grape or orange flavor conditioned stimulus/stimuli (CS) with (1) ethanol or saccharin solution or (2) either the other unconditioned stimulus/stimuli (UCS) or plain tap water. They were then given 2-bottle choice tests between the flavor CSs apart from the UCSs. Flavors associated with 5% ethanol were preferred over saccharin-paired and water-paired flavors by sated Ss, and food deprivation during the choice test enhanced this preference. Flavors associated with 8% sucrose were preferred over water-paired flavors, and this preference was also enhanced by food deprivation. Flavors associated with 0.028% or 0.25% saccharin were preferred over flavors paired with water. In all cases, calorie-mediated preferences, at their highest levels, were stronger than taste-mediated preferences. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bait shyness: Avoidance of the taste without escape from the illness in rats.

Conducted 3 experiments with 50 young adult Sprague-Dawley rats. Thirsty Ss habituated to drinking .12 M sodium chloride accepted .12 M lithium chloride for 5 min on the 1st trial but stopped short of their sodium baseline. With repeated trials they reduced consumption of the toxin by either (a) detecting subtle oral CS differences, thus avoiding toxicosis (UCS) or (b) detecting earlier signs of malaise (UCS), thus escaping further distress. When both solutions were masked with saccharin, discrimination was more difficult but still possible. When both solutions were mixed in a solution masking all 4 taste qualities, discrimination was severely disrupted. When oral sensors were bypassed with nasopharyngeal tubes, intragastric pumping Ss were unable to use postingestional cues to escape, even though such cues were proximal to the ultimate malaise. Oral cues at the distal end of the consummatory chain were extremely effective. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of obesity and set point on taste responsiveness and ingestion in humans.

Two experiments, with a total of 120 undergraduates, investigated the relationships among degree of obesity, nearness to set point for adipose tissue mass, and responsiveness to taste. In Exp I, Ss rated milkshakes varying in sweetness intensity. Overweight and normal weight Ss did not have significantly different detection thresholds or preference ratings. However, overweight Ss worked longer than normals to obtain their most preferred substance. Exp II varied the ease of tasting the milkshake. Preference and food intake of moderately overweight Ss were significantly more influenced by tastes that they found positive and negative than was the preference of normal weight or obese Ss. The ease of ingesting the taste substance also significantly influenced preference and food intake of the moderately obese only. Nearness to set point, operationally defined as weight stability for 2 yrs, had no significant effects. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sodium depletion enhances salt palatability in rats.

Stereotyped fixed action patterns (FAPs) elicited in rats by oral infusions of taste solutions can be classified as either ingestive or aversive. They reflect the palatability of the taste and can be modified by learning and by the physiological state of the animal. The present 2 experiments, with 5 male Sprague-Dawley rats, demonstrated that when the physiological state of the S was altered by sodium depletion, the pattern of FAPs elicited by oral infusions of 0.5 M NaCl shifted from a mixture of ingestive and aversive components (while sodium replete) to exclusively ingestive ones (while sodium deplete). This shift in taste reactivity occurred the 1st time the Ss were made sodium deplete. A similar shift did not accompany infusions of 0.01 M HCl, a taste solution that also elicited mixed ingestive and aversive FAPs. This result suggests that the shift in response to NaCl was not due to a general change in ingestive bias or to a general taste deficit. On the basis of the change in FAPs, it is concluded that the palatability of highly concentrated salt solutions increases in sodium-deplete rats. Such a shift in salt palatability may be instrumental in directing the appetitive behavior of the animal. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of potassium depletion on mineral appetite in the rat.

Studied potassium appetite in normal female Sprague-Dawley rats and in rats in which the total body potassium had been reduced by 15-20%. Potassium depletion resulted in increased ingestion of solutions of NaCl, KCl, CaCl2, and quinine sulphate in concentrations that were unacceptable to normal Ss. The amount of potassium ingested was related to the degree of potassium depletion and repletion was usually completed within 24 hr. when potassium was offered. Potassium-depleted Ss also drank large quantities of aversive concentrations of sodium chloride. This was preferred to potassium chloride and its ingestion appeared to be unrelated to need. The appetite state was reversed by prior intragastric repletion with potassium but not with sodium salts. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste rejection of nonnutritive sweeteners in cats.

Cats reject saccharin and cyclamate and are indifferent to dulcin, although they, like other mammals, prefer sucrose. The rejection threshold for saccharin found for 10 cats in the present 2 experiments, 0.0001 M, was about 2 log steps lower than a previously reported rejection threshold for sodium saccharin. Water produced a taste in Ss adapted to their own saliva. The high sodium saccharin was masked by the taste of the water solvent; however, saccharin may also be somewhat more aversive to the cat than sodium saccharin. Saccharin may produce an aversive taste because it stimulates receptor sites sensitive to substances bitter to man as well as those sensitive to sugars. In addition, saccharin may not be an effective stimulus for all sugar-sensitive sites. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in electrophysiological and behavioral responses to NaCl taste.

We tested the hypothesis that sex differences in preference for NaCl are attributable to estrogen-mediated alterations in gustatory processing. Electrophysiological responses of the chorda tympani nerve to NaCl were blunted by estrogen treatment in ovariectomized female rats, suggesting that females are less sensitive to concentrated NaCl solutions during high estrogen conditions. In contrast, after a taste aversion was conditioned to 150-mM NaCl, estrogen- and oil-treated ovariectomized rats generalized the aversion to a lower concentration of NaCl than did males, suggesting that females are more sensitive to the taste of dilute NaCl solutions regardless of estrogen. Thus, sex differences in NaCl preferences may be attributable to differences in NaCl taste processing that involve both acute and developmental effects of estrogen. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of basolateral amygdala lesions on neophobia, learned taste aversions, and sodium appetite in rats.

Reports results of 8 experiments with a total of 327 male Sprague-Dawley rats. Lesions to the basolateral amygdala produced permanent impairment in Ss' ability to learn a taste aversion. When lesions were administered after Ss had already learned an aversion, there was complete loss of the aversion. Ss with amygdala lesions also had a diminished neophobic response when presented with a novel solution and showed a more generalized aversion to water after a sucrose-sickness trial. Whether a solution was novel or familiar affected the learning of an aversion for controls more than it did for Ss with amygdala lesions. Ss with amygdala damage also showed less sodium appetite than normals in response to desoxycorticosterone acetate injections. These results indicate that rats with amygdala lesions have deficits in recognizing the significance of stimuli. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste reactivity to alcohol and basic tastes in outbred mice

The taste reactivity test was used to determine the response of outbred mice to orally infused taste solutions. For the initial measures, mice (n = 10) were tested with 3%, 6%, 9%, and 12% (v/v) alcohol and four taste solutions: sucrose, sodium chloride, hydrochloric acid, and quinine hydrochloride (a single concentration of each). A second group of naive mice (n = 16) was tested with 5%, 10%, 20%, 30%, and 40% alcohol. The final set of measures with naive mice (n = 26) was taken with a range of sucrose concentrations: 0.01 M, 0.05 M, 0.1 M, 0.5 M, and 1.0 M. In general, mice made similar reactivity responses to all solutions tested. A predominant component of the mouse response to all infused fluids was forelimb flailing; gaping was also a common response to all solutions. Despite the large number of aversive-type responses, mice rejected very little fluid via passive drip or fluid expulsion. The single, significant difference in responding to the four taste stimuli was that mice made fewer aversive responses to sucrose. Differential responding to the 5 to 40% alcohol concentrations and sucrose concentrations was observed. Mice increased ingestive responding as the concentration of alcohol and sucrose increased. Aversive responding decreased reliably only with increases in the sucrose concentration. Data provide the first reported taste reactivity responses of mice to orally infused taste solutions. These results can be compared with the extant data available in rats and can also be used as a basis for exploring taste factors in genetically defined mouse populations.