Relation of consummatory responses and preabsorptive insulin release to palatability and learned taste aversions.

In 6 experiments with 68 male Sprague-Dawley rats, the oral stimulation arising from food in the mouth produced a stereotyped sequence of ingestive consummatory responses and a rapid release of insulin prior to the absorption of nutrients into the blood. Conversely, when noxious taste stimuli were infused into the mouth, a different, aversive set of consummatory responses was evoked, and no insulin was released. These experiments demonstrate that pairing a sapid taste solution with LiCl reversed the consummatory response sequence to subsequent presentations of that taste from ingestion to aversion and abolished the preabsorptive release of insulin to that taste; this indicated an experience-produced shift in the palatability of the taste. It was further shown that a palatable but categorically noncaloric taste elicited behavioral ingestion but no insulin release. It is concluded that separate but related control systems operate to produce consummatory behavior and ingestive neuroendocrine responses. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Area postrema mediates the formation of rapid, conditioned palatability shifts in lithium-treated rats.

The rapid acquisition and subsequent retention of lithium-induced conditioned changes in taste reactivity responses to sucrose were examined in rats with the area postrema (AP) either ablated or intact. On 2 conditioning days, a series of brief intraoral sucrose infusions was paired with the effects of LiCl or NaCl injections. Repeated associations of the sucrose taste with the effects of lithium significantly reduced ingestive responses and increased aversive responses only in the AP-intact group. AP-ablated rats treated with LiCl and rats injected with NaCl displayed an ingestive pattern of responses. Only the AP-intact rats, previously injected with LiCl, subsequently displayed evidence of a conditioned taste aversion. We conclude that toxin activation of the AP is required to produce the conditioned shift in taste reactivity responses and subsequent expression of a taste aversion in rats treated with lithium. (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)     

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.     

Control of fluid palatability by exteroceptive Pavlovian signals.

Two experiments, with 15 male albino rats, investigated whether discrete auditory conditioned stimulus/stimuli (CS) that signal the availability or onset of taste unconditioned stimulus/stimuli (UCS) (sucrose, quinine) can control orofacial responses in the absence of those UCSs. In Exp I, one auditory stimulus (CS+) was paired with the delivery of a sucrose solution to the magazine floor, and another auditory stimulus (CS–) was never followed by sucrose. Following conditioning, oral infusions of water that were preceded by the CS+ were found to elicit more ingestive (sucrose-typical) orofacial responses than did water alone or water preceded by the CS–. In Exp II, the conditioned ingestive reactions to a signal for sucrose observed in Exp I again occurred, and conditioned aversive (quinine-typical) orofacial responses occurred in response to water infusions preceded by a former signal for quinine. Data suggest that perceived palatability may be influenced by Pavlovian associations involving exteroceptive CSs and illustrate the importance of supporting stimuli in modulating the effects of Pavlovian associations on behavior. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toxin-induced conditioned changes in taste reactivity and the role of the chemosensitive area postrema

Conditioned taste avoidances (CTAs) are an important component of behavioral regulation of ingestion. In the laboratory CTAs can be produced by pairing a novel taste stimulus with the physiological feedback produced by a toxin, such as lithium. Such toxins putatively activate a chemosensitive brainstem structure, the area postrema, which ultimately results in the production of a CTA. The present review describes a series of studies which examined conditioned changes in taste reactivity responses (TRRs) when a novel intraoral sucrose taste was paired with the effects of an intraperitoneal (IP) injection of LiCl, and the role of the area postrema in the formation of conditioned palatability shifts. It was first of all necessary to examine the effects of area postrema ablations on TRRs to a range of intraoral sucrose and quinine stimulus intensities. In the first study area postrema lesioned rats exhibited concentration dependent changes in TRRs to these taste stimuli that were very similar to those exhibited by sham lesioned rats. The second study demonstrated that 30 s intraoral infusions of sucrose (0.3 M), presented at 5 or 10 min intervals following an IP injection of LiCl (3.0 meq), resulted in conditioned changes in TRRs. These were characterized by orderly, gradual reductions in ingestive responses and increases in aversive responses. Finally, when area postrema lesioned rats (Study 3) were subjected to this conditioning procedure (brief sucrose presentations paired with the effects of LiCl) no evidence for conditioned or unconditioned changes in TRRs to sucrose were obtained. Lesioned rats injected with LiCl behaved similarly to sham lesioned rats injected with NaCl. These series of studies provide evidence indicating that the chemosensitive area postrema mediates the formation of conditioned palatability shifts induced by treatment with a toxin such as lithium.     

Electromyographic analysis of the ingestion and rejection of sapid stimuli in the rat.

For further clarification of the relation between orofacial movements produced by gustatory stimuli (the buccal phase of ingestion) and the act of swallowing (the pharyngeal phase), electromyogram (EMG) responses to intraoral sapid stimulation were recorded from a subset of orofacial and pharyngeal muscles in 25 male rats. Muscle activity reliably differentiated between ingestive sequences to water (W), sucrose (S), and NaCl (N) and a rejection response elicited by quinine monohydrochloride (Q). Ingestion responses to W, S, and N consisted of rhythmic alternations between genioglossus and styloglossus activity (intraoral licks) accompanied by episodic bursts of pharyngeal constrictor activity (swallowing). Both bout duration and number of swallows increased at higher concentrations of S and N. In contrast, Q stimulation elicited a rejection response characterized by several licks and followed by long duration contractions of the zygomatic and anterior digastric muscles (gapes). During gapes, styloglossus activity rather than genioglossus activity was simultaneous with that of the anterior digastric. At higher concentrations of Q, the latency to gape decreased and the latency to swallow increased. The earliest components of the response to S, N, or Q were indistinguishable from one another, suggesting that tactile (fluid) stimulation initiates the ingestive sequence and that gustatory stimuli modulate this ongoing activity. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic voluntary nicotine drinking enhances nicotine palatability in rats.

Examined the response of rats to nicotine (NI) solutions with the brief-exposure, taste reactivity (TR) test, and a 2-bottle, 24-hr preference test. Naive nondeprived Ss were administered intraoral infusions of distilled water and 1 μg/ml, 5 μg/ml, 10 μg/ml, 25 μg/ml, 50 μg/ml, and 100 μg/ml NI. NI solutions up to a concentration of 50 μg/ml elicited a number of ingestive TR responses similar to that by water. Ingestive responses significantly decreased and aversive TR responses significantly increased in response to 100 μg/ml nicotine. On the basis of these results, 2-bottle preferences for water vs 1 μg/ml, 5 μg/ml, and 0 μg/ml (water control group) NI were measured in 3 groups of naive Ss. Ss initially showed an equal preference for 0 μg/ml and 1 μg/ml NI. After 16 days of exposure, however, Ss developed a significant preference for 1 μg/ml NI. The preference ratio for 5 μg/ml NI significantly increased during the experiment, but the preference ratio remained significantly less than that for 1 μg/ml and 0 μg/ml NI solutions. Last, TR responses elicited by intraoral infusions of 1 μg/ml and 5 μg/ml NI were then measured in these Ss having had the 2-bottle experience. Ss showing a 2-bottle preference for the 1 μg/ml NI solution displayed significantly more ingestive TR responses to 1 μg/ml and 5 μg/ml NI than did the control Ss. Data indicate that prolonged voluntary access to NI results in an increased preference for NI and modifies the immediate oral/gustatory reactivity of the Ss to NI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal and Qualitative Dynamics of Conditioned Taste Aversion Processing: Combined Generalization Testing and Licking Microstructure Analysis.

The pattern of licking microstructure during various phases of a conditioned taste aversion (CTA) was evaluated. In Experiment 1, rats ingested lithium chloride (LiCl) for 3 trials and were then offered sodium chloride (NaCl) or sucrose on 3 trials. A CTA to LiCl developed and generalized to NaCl but not to sucrose. CTA intake suppression was characterized by reductions in burst size, average ingestion rate, and intraburst lick rate, and increases in brief pauses and burst counts. Compared with previous studies, LiCl licking shifted from a pattern initially matching that for normally accepted NaCl to one matching licking for normally avoided quinine hydrochloride by the end of the 1st acquisition trial. In Experiment 2, a novel paradigm was developed to show that rats expressed CTA generalization within 9 min of their first LiCl access. These results suggest that licking microstructure analysis can be used to assay changes in hedonic evaluation caused by treatments that produce aversive states. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amount of training and cue-evoked taste-reactivity responding in reinforcer devaluation.

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally trained CS controlled substantially more evaluative TR responses than the extensively trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively trained cue. These responses were reduced by sucrose devaluation comparably, regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating preevaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: II. Independent ingestive behavior.

In 4 experiments, Charles River rat pups 3 days of age and older consumed large quantities of milk, sucrose, and wet mash when the Ss were placed in warm containers in which one of these diets had been spread on the floor. The volume of Ss" intake was directly related to the severity of food deprivation. Ingestive behavior occurred in the early part of the 30-min test, but later in the test, Ss stopped feeding and became quiescent. Their ingestive behavior thus resembled that of adults in (a) the motor aspects of feeding responses (licking and lapping), (b) the dependency on deprivation for intake, and (c) the pattern of intake termination. However, in Exp IV, when diet was restricted to a small area of the test container, young Ss consumed little diet. They did not appear able to direct or focus their ingestive responding. It was not until 9–12 days of age that Ss successfully consumed milk from a localized source. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeding induced by GABAA receptor stimulation within the nucleus accumbens shell: Regional mapping and characterization of macronutrient and taste preference.

This study investigated the areas of the nucleus accumbens shell involved in the modulation of feeding behavior by GABAergic stimulation and characterized this response using macronutrient diets as well as saline, sucrose, and saccharin solutions. The GABA agonist muscimol induced a pronounced feeding response when infused in the medial nucleus accumbens shell but not in the ventral or lateral accumbens shell. In the macronutrient preference study, muscimol increased the intake of both high fat and high carbohydrate diets when presented separately. When both diets were available simultaneously, muscimol stimulated feeding of both diets to the same degree. Muscimol elicited a robust increase in the consumption of sucrose solution. However, no effect of muscimol was demonstrated for water, saline, or saccharin intake. These findings provide evidence for a selective role for GABA-sensitive neurons in the medial accumbens shell in the regulation of ingestive behavior and further suggest that GABAA receptors in this region do not modulate palatability, macronutrient selection, or rewarding properties of food. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning in honeybees (Apis mellifera) as a function of amount of reward: Acquisition measures.

Foraging honeybees (Apis mellifera) were trained individually to discriminate between targets that contained 5-μl or 20-μl drops of sucrose solution. Neither latency of response on single-stimulus trials nor preference on choice trials proved sufficiently sensitive to provide a detailed picture of the course of learning as a function of amount of reward, but measures of resistance to extinction supported the assumption that the slope of the acquisition function increases with amount of reward while its asymptote remains the same. Like rats in a double runway, the honeybees tended to respond less rapidly after large than after small reward, which does not require an associative interpretation. Other results showed that 5- and 20-μl drops of sucrose are differentially reinforcing in consequence of their ingestive properties rather than their visual appearance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Additivity of taste-specific effects of sucrose and quinine: Microstructural analysis of ingestive behavior in rats.

Effects of sweet and bitter tastes on ingestion were studied by timing licking responses. 12 water-deprived rats were given 15-min access to sucrose (SU) solutions (0.00, 1.25, 2.50, and 5.00%) with and without quinine (Q; 0.01%) and to Q solutions (0.00, 0.0025, 0.005, and 0.01%) with and without SU (5.00%). Volume ingested and number of licks increased with SU and decreased with Q. In response to SU, the number of bursts increased, and interlick intervals lengthened. In response to Q, licks to ingest 1 ml of solution, burst number, and percentage of slow licks increased, and burst size decreased. When Q and SU were mixed in the same solution, the pattern of ingestive responses manifested attributes of both tastes. Results suggest 2 separate, parallel systems that operate simultaneously to govern rats' licking behavior. One system expresses the effects of SU on the pattern of ingestion and the other expresses the effects of Q. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: I. Ingestive and behavioral responses to oral infusions.

Reports on 3 experiments with Charles River rat pups. When milk infusions were made through oral cannulas in the front of their mouths, 1–20 day old Ss actively ingested the diet, and their intake was related to the length of deprivation. Ss decreased their ingestive responding after they had consumed large volumes of milk. In addition, 1-, 3-, and 6-day-old Ss, when 24-hr deprived, exhibited an intense behavioral activation in response to milk infusion. The behavioral activation appeared to be stimulated primarily by taste and the opportunity to swallow. Milk infusions did not produce activation in older Ss; their behavior was more exclusively ingestive and food directed. Results demonstrate that (a) from birth, rat pups are capable of an active form of ingestion, independent of normal suckling from the mother; (b) such ingestion is controlled by physiological factors; (c) food has arousing properties in young animals; and (d) as pups grow older, their ingestive responding is refined from a generalized and nondirected activation to specific and directed feeding responses. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased liking for a solution is not necessary for the attenuation of neophobia in rats.

Recent evidence suggests that liking and wanting of food rewards can be experimentally dissociated (e.g., Berridge, 1996); this dissociation extends to attenuated neophobia in the present study. Rats tend to eat less of a novel food than a familiar food, a phenomenon called neophobia. The present experiments evaluated whether attenuation of neophobia by prior exposure reflects enhanced liking of the flavor using the Taste Reactivity (TR) test. In Experiment 1, rats given five 10-s TR trials with water or various concentrations of saccharin solution (0.1%, 0.2%, 0.5%) did not show a change in the number of hedonic reactions displayed across trials. However, in a subsequent consumption test from a bottle containing 0.25% saccharin solution, rats with no prior saccharin exposure (group water) consumed less than rats with prior saccharin exposure; that is they displayed neophobia. In Experiment 2, whether rats received five 10-s TR trials with water or 0.5% saccharin solution, they did not display a difference in hedonic reactions to 0.25% saccharin solution in two 5-min TR test trials. These results suggest that the attenuation of neophobia is evidenced as an increase in the tendency to approach a bottle containing the flavored solution (wanting), but not as an enhanced liking of that solution. (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)     

Intraoral intake and taste reactivity responses elicited by sucrose and sodium chloride in chronic decerebrate rats.

Oral stimulating effects of sucrose and NaCl were assessed in chronic decerebrate and pair-fed intact control rats by measuring oral motor taste-reactivity responses (TRRs) and intraoral intake (II) volume. TRRs were videotaped during the 1st minute of the intraoral taste infusion. The infusion continued until the taste solution was rejected from the mouth, and the intake volume was computed accordingly. The number of ingestive TRRs and the volume of II consumed by pair-fed control and decerebrate rats increased with increasing sucrose concentration. Sucrose intake increased as concentration increased, then plateaued for both groups. For controls, intraoral NaCl elicited an inverted U-shaped function for both TRRs and intake. TRRs of chronic decerebrate rats varied with NaCl concentration. In contrast with controls, intake of NaCl did not differ from that of water for decerebrate rats. Data indicate that caudal brain-stem mechanisms are sufficient to control sucrose intake but not adequate for the concentration dependent intake of NaCl. Data indicate it is possible for taste-elicited oral motor responses to be dissociated from intake. Roles of taste and postingestive factors in sucrose and NaCl intake are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Variations du rythme cardiaque d'enfants soumis à des taches d'observation et de contr?le de stimulations complexes.

Three experiments were conducted to determine the cardiac responses of 30 preschool children requested to be attentive to stimulations and/or to try to control their occurrences by a simple or more complex motor behavior. In Exp I, Ss were instructed to pay attention to the movements, lights, and sounds originating from a harlequin puppet (observation condition). In Exp II, Ss were told that they could initiate the harlequin stimulations with a simple motor response (easy control condition). In Exp III, Ss had to perform a more complex response to initiate the stimulation (difficult control condition). In the observation condition, the first stimulations elicited a decelerative heart rate response. In the easy control condition, both groups displayed an equivalent number of keypresses. Ss in the difficult control condition, while making as many keypress responses, obtained fewer stimulations than Ss of the easy contingent group. Their tonic and phasic cardiac responses during the demonstration–observation phase were similar. During the control trials, the first and last stimulations within trials were followed by phasic decelerative responses in this group. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alternating ingestive and aversive consummatory responses suggest a two-dimensional analysis of palatability in rats.

Examined the hedonic response to a taste which is usually regarded as the product of a central integration of gustatory afferent information that ends in a single decision about the nature and intensity of the response to be given. The response is often characterized as a point lying along a single dimension of palatability, stretching from strongly positive to strongly negative. Two experiments dealing with consummatory responses in male Sprague-Dawley rats suggested that the final response is not made on the basis of a single central analysis of taste information, but rather is the result of a competition between 2 separate systems that are activated by tastes. A single oral infusion of a taste solution may elicit rapid alternation between ingestive and aversive consummatory responses. Such alternation is better interpreted as due to a simultaneous activation of 2 palatability dimensions than as a reflection of neutral palatability. When increases in the magnitude of aversive responses are produced by taste mixtures, there is not necessarily a reciprocal decrease in ingestive responses. This asymmetry supports the hypothesis of independent palatability dimensions. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)