The effect of hunger on water intake in rats

Although reciprocal inhibition between eating and drinking has been postulated, the commonly observed reduction of water intake by hungry rats may not be due to any direct inhibitory mechanism. In one experiment rats deprived of food for 24 hr. and then injected with 2 ml. of NaCl drank the same as rats that had received food ad lib. In the second experiment a stomach load of 10 ml. of water 3 hr. before the salt injection was designed to abolish any water deficit that might have occurred during food deprivation had there been inhibition of drinking by hunger. Here again rats deprived of food did not drink less than undeprived animals. In fact the hungry rats drank slightly but significantly more. This phenomenon may be related to the observation confirmed here that during food deprivation rats excrete about twice as much rather dilute urine as during ad lib food intake. This seems to indicate that though in general food deprived rats drink less than normal they actually drink more than they need. Schedule induced polydipsia also occurs during food deprivation and this too makes it unlikely that water-intake is actually inhibited during hunger.     

The role of the instrumental contingency in the motivational control of performance

In four experiments we investigated an irrelevant incentive effect based upon a transition from hunger to thirst. Hungry rats were trained to lever press either for sucrose solution or for food pellets before performance was tested in extinction while they were thirsty. Reinforcer-specific motivational control was found in the first experiment in that the animals pressed the lever more on tests following training with the sucrose solution rather than with food pellets. Moreover, this effect was seen only when testing was conducted following water, but not following food deprivation. The outcome of the remaining experiments suggests that this motivational control is not mediated by the instrumental contingency between lever pressing and the sucrose reinforcer during training. In these studies lever pressing and chain pulling were reinforced concurrently, one with sucrose and the other with food pellets, in order to equate the noninstrumental functions of the incentives. Following this training, lever pressing in extinction under thirst was unaffected by the type of incentive used as its reinforcer during training.     

Personal Theories of Hunger and Eating1

Recent research on hunger and eating has shown that (a) among individuals with adlibitum access to food, hunger and eating are not regulated by deviations in the body's energy resources from set-points, and (b) it is healthier for people to consume their daily caloric intake as several small snacks than as 3 large meals. People's beliefs about hunger and eating were assessed in 2 questionnaire studies. In Study 1, a large sample of undergraduates was surveyed; in Study 2, dietetics students, nursing students, medical students, dietitians, nurses, and doctors were surveyed. Both studies revealed that people's personal theories of hunger and eating were inconsistent with research findings in ways that could promote overconsumption. These results suggest that educational programs designed to modify the beliefs about hunger and eating of people suffering from problems of overconsumption and of health professionals who treat problems of overconsumption may increase the effectiveness of current treatment regimens.     

Predictors of disinhibited eating in children with and without overweight

OBJECTIVE: This study examined how 7-13-year-old children with and without overweight respond to free access to snack food in the absence of hunger and whether this eating behaviour could be predicted by parental feeding strategies and child's characteristics. METHODS: A total of 52 children (26 normal weight and 26 overweight children) were exposed to snack food after consuming a typical meal. Parental feeding practices and child's variables were assessed via self-report. RESULTS: Two-third of the sample ate of the presented snacks and consumed an average of 68 g. Overweight boys consumed twice as much than the normal weight boys. Parental feeding strategies did not contribute to the prediction of this eating behaviour. Regardless of the children's weight status, the child's eating style strongly predicted snack intake. CONCLUSIONS: This study provides evidence that overweight boys show difficulties in regulating their eating behaviour. Inconsistent with previous work, no evidence for parental contribution of snack intake was found. The present findings suggest that in older children especially children's own eating style account for the variance in snack eating behaviour.     

Reversal learning as a function of changed reward location or changed drive

In two experiments, rats were trained with food in one location (e.g., black alley) and water in another location (white alley) under hunger or thirst. Subsequently, either the locations of the rewards were reversed, or the drive was changed (from hunger to thirst or thirst to hunger). Reversal of instrumental responses took considerably longer when drive was changed and rewards remained in the same locations than when reward locations were reversed. These results were interpreted as indicating that the animal's internal representations of the rewards received in each location transfer when drive is changed. These internal-reward representations interfere with reversal learning by eliciting the responses which were conditioned to them in Phase 1. Because the values of food and water reverse when drive is changed from hunger to thirst or vice versa, it was suggested that the reward representations surviving the drive shift are cognitive representations of the specific events received (food or water), independent of the value of the rewards under either hunger or thirst.     

The effect of anxiety on food intake in the rat

Three levels of anxiety were induced experimentally in rats. With hunger drive held constant, the effects of anxiety on the intake of food which had either a positive or negative incentive value were observed and compared. The results for the intake of food with positive incentive value showed eating to be increased above control level by a low level of anxiety, and slightly decreased by medium and high levels. On the other hand, a direct relationship was observed between level of anxiety and suppression of the intake of food with a negative incentive value. These findings were shown to be inconsistent with previous explanations of similar effects in terms of an interaction between relevant and irrelevant drives. An alternative explanation in terms of incentive was offered.     

Variations in the sensitivity of instrumental responding to reinforcer devaluation

In five experiments hungry rats were trained to make a lever press response for a sucrose reinforcer. That sucrose was subsequently devalued by conditioning a food-aversion to it, and the ability of the rats to integrate knowledge about the instrumental contingency with that gained from aversion training was assessed in an extinction test. Experiment I showed successful integration following limited but not extended instrumental training. Experiment II suggested that the crucial factor was the spacing of training; successful integration was seen after massed but not distributed training. The third experiment implicated distributed experience with the reinforcer, rather than distributed response practice, in failures of integration. Experiment IV showed that if the distribution of food-aversion learning was dissimilar to that of instrumental training then a failure of integration could result; this finding was able to account for the distribution of training effects seen in previous studies, but not the effect of extended training. Experiment V replicated the extended training effect seen in Experiment I, and provided evidence that this may reflect the degree of exposure to the reinforcer rather than the extent of response practice.     

Increased eating in rats deprived of running

Daily food intake in rats was temporarily reduced by the introduction of an activity wheel and temporarily increased by the subsequent removal of the wheel. When this outcome is coupled with the positive relation between food deprivation and running—and food deprivation is seen as a loss of eating rather than as a physiological state—there is the suggestion that the total behavior output of the organism may be regulated as such. Specifically, when the rat is deprived of a behavior that recurrently comprises a large part of its total daily activity, an increase may occur in some other behavior.     

Motivational control of instrumental performance following a shift from thirst to hunger

Thirsty rats were trained to press a lever for either a sucrose solution or saline before performance was tested in extinction while the animals were either hungry alone or experiencing both hunger and a sodium appetite. Reinforcer-specific motivational control was observed in that the animals trained with the sucrose solution pressed more than those trained with the saline when they were tested hungry, but not when they were tested under combined hunger and sodium appetite. In order to assess the role of a Pavlovian incentive process in this effect, thirsty animals received non-contingent pairings of one stimulus with the sucrose solution and another with saline in the second experiment. In an extinction test the sucrose stimulus augmented lever pressing relative to the saline stimulus when the animals were hungry, but not when they were thirsty. In the subsequent experiments the contribution of the Pavlovian process was equated by giving concurrent training with both incentives. Lever pressing and chain pulling were reinforced concurrently, one with the sucrose solution and the other with saline, while the animals were thirsty. Once again, the animals pressed more in extinction if this action had been trained with the sucrose solution rather than the saline, but only if they were hungry rather than thirsty. Thus, instrumental performance across a thirst-to-hunger shift can also be controlled by an instrumental incentive process. The direct engagement of the instrumental process by this motivational shift contrasts to the absence of such control following a hunger-to-thirst transition (Dickinson & Dawson, 1987a), a fact attributed to the asymmetrical motivational interactions produced by water and food deprivation.     

Motivational properties of conditioned suppression

Two experiments were performed to investigate the interaction of baseline appetitive drive and incentive on the conditioned suppression of instrumental behavior exhibited in the presence of a preaversive stimulus. In one experiment, suppression of lever pressing of rats working on an intermittent food reinforcement schedule was considerably enhanced following partial satiation with food. In a second experiment, using a similar baseline, suppression was shown to be diminished by an increase in concentration of the baseline incentive. These results are consistent with the hypothesis that the instrumental suppression of the conditioned emotional response (CER) is a consequence of an algebraic interaction of hunger with fear.     

Rats (Rattus norvegicus) modulate eating speed and vigilance to optimize food consumption: effects of cover, circadian rhythm, food deprivation, and individual differences.

The eating behavior of rats (Rattus norvegicus) given food pellets of specified size was examined as a function of environmental, circadian, and experiential influences. Eating times were shorter in lighted, exposed environments than in dark, covered environments, even though in novel, exposed conditions the rats made many scanning movements as they ate. Eating time also varied as a function of the circadian cycle in that eating times were shorter in the night portion of the day-night cycle. Finally, eating times decreased if rats were food deprived, and deprivation had a small but enduring influence. Within the tests there were differences in the eating times of individual rats that were not attributable to the experimental manipulations. That rats can optimize food intake by varying eating speed is discussed in relation to physiological regulation of feeding and to optimal foraging theory.     

Resistance to satiation of consummatory and instrumental performance

In three experiments rats received training in a straight alley under high hunger and then were tested satiated. Both eating and running continued to occur under satiation, but the two responses were not completely correlated, and continued running did not depend upon continued eating. Further, groups differed in their eating behavior, although all experienced the same satiation procedure, suggesting that eating under satiation is not just a reflection of incomplete satiation. Resistance to satiation of the running response was greater following partial reward than following consistant reward and tended to be greater following small reward training than large reward training, regardless of schedule of reward. Eating during satiation was greater following partial than following consistent reward and was greater if the same reward magnitude was given in satiation as in acquisition than if a different reward magnitude was given. It was suggested that resistance to satiation is an associative phenomenon. Eating and running occur during satiation because the stimuli present during satiation continue to elicit them. The differences between results using rewarded satiation and results using high drive extinction as measures of persistence were attributed to satiation being nonfrustrating.     

Binge eating proneness emerges during puberty in female rats: a longitudinal study

Puberty is a critical risk period for binge eating and eating disorders characterized by binge eating. Previous research focused almost entirely on psychosocial risk factors during puberty to the relative exclusion of biological influences. The current study addressed this gap by examining the emergence of binge eating during puberty in a rat model. We predicted that there would be minimal differences in binge eating proneness during pre-early puberty, but significant differences would emerge during puberty. Two independent samples of female Sprague-Dawley rats (n = 30 and n = 36) were followed longitudinally across pre-early puberty, mid-late puberty, and adulthood. Binge eating proneness was defined using the binge eating resistant (BER)/binge eating prone (BEP) model of binge eating that identifies BER and BEP rats in adulthood. Across two samples of rats, binge eating proneness emerged during puberty. Mixed linear models showed little difference in palatable food intake between BER and BEP rats during pre-early puberty, but significant group differences emerged during mid-late puberty and adulthood. Group differences could not be accounted for by changes in nonpalatable food intake or body weight. Similar to patterns in humans, individual differences in binge eating emerge during puberty in female rats. These findings provide strong confirming evidence for the importance of biological risk factors in developmental trajectories of binge eating risk across adolescence.     

Inhibition of ad Libitum Feeding in Rats by Salt Injections and Water Deprivation

Inhibition of ad libitum feeding in rats was induced by hypertonic NaCl injections. Though osmotic loads of sufficient size were capable of abolishing feeding completely for a time, the effect was not as large as had been predicted from a hypothesis of strictly linear subtractive inhibition. Feeding at a low level of hunger seems to be somewhat less affected by osmotic inhibition than feeding on a deprivation schedule. Inhibition of feeding was also produced by deprivation of water, and both the inhibition of food intake during deprivation, and the disinhibition by subsequent drinking indicated that the amount of inhibition of food intake is a non-linear (accelerating) function of water deficit. A model of the process indicating that the thirst signal undergoes a non-linear transformation before being subtracted from the signal corresponding to food demand is proposed.     

The saliva priming effect,eating speed and the measurement of hunger

Volunteers were tested under two conditions, either just before or just after a meal. The aim of the investigation was to identify subjective, behavioural and physiological correlates of hunger. Subjective measures of hunger and expected enjoyment as well as speed of eating clearly differentiated the two conditions. Although the basal level of salivation did not change significantly, there was a clear differential priming effect after consuming a small amount of chocolate. The saliva priming effect was greater when subjects were hungry. Correlations between change scores suggest that two partially independent systems are activated by food deprivation which could be labelled ‘hunger-salivation’ and ‘enjoyment-speed of eating’.     

Trigeminal deafferentation and hunger in the pigeon (Columbia livia).

The location and distribution of the pigeon's trigeminal nerve permit deafferentation of the oral region without affecting motor functions. Although trigeminal deafferentation does not affect drinking, it reduces the efficiency of the consummatory response of eating and disrupts motivational processes underlying hunger and weight regulation. Although the two types of deficit may be experimentally dissociated, trigeminal deafferentation invariably affects both sensorimotor and motivational mechanisms. The deficits in food intake and weight regulation seen after trigeminal deafferentation in the pigeon resemble some components of the "lateral hypothalamic syndrome" in the rat. The results are related to recent studies of the contribution of peripheral and central oropharyngeal factors to the neural control of food intake in both rat and pigeon.     

Abdominal vagotomy disrupts food-related drinking in the rat

Rats with complete subdiaphragmatic bilateral transection of the abdominal vagus (Vgx-C) showed disordered food-related drinking when drinking water in temporal association with a meal of dry food after 5-hr food deprivation and when drinking water in association with a liquid meal after 24-hr food deprivation. The Vgx-C rats drank after significantly longer latencies and drank significantly less water in 1 hr than did sham-vagotomized (Sham) rats after eating the same size meal (solid or liquid) as Shams. Rats with incomplete vagal transection (Vgx-I) ate and drank like Shams. Water intake of Sham and Vgx-I rats correlated positively with the meal size of solid food, but the water intake of Vgx-C rats did not. The failure of Vgx-C rats to drink water normally when food was ingested was not due to failure of a food stimulus to reach the intestine, because Vgx-C and Sham rats emptied equivalent volumes of liquid food from the stomach into the intestine within 10 min of food entering the stomach. These results indicate that the abdominal vagus is an important neurological substrate for food-related drinking in the rat.     

A bioinspired model of short-term satiety of hunger influenced by food properties in virtual creatures

The behavior of the human is continually changed as a consequence of various drives which human is predisposed also of your survival instinct. Among the basic drives of the human, there are the physiological needs and is precisely the hunger that motivates the food intake to get the energy that the body requires via food. The regulation of hunger allows to stop the food intake by means of the homeostatic and hedonic control which are influenced by the food properties. The process that consists of ending the food intake is known as short-term satiety and is important because it limits the amount of food intake; Otherwise, an over-consumed affect the organism functioning negatively. In this paper, we propose a conceptual model for the generation of short-term satiety behaviors based on neuroscientific evidence for virtual creatures. The conceptual model proposed is implemented in a distributed system-a virtual creature endowed with this implementation is placed in a virtual environment to analyze its behavior. The analysis shows how the virtual creature modifies its hunger level (behavior) based on food’s properties. The results show the execution of the process when the creature interacts with the environment.     

Pavlovian processes in the motivational control of instrumental performance

Hungry rats were rewarded for pressing a lever on a multiple schedule. During one component the reward was a sucrose solution, whereas food pellets acted as the reward during another component. Lever pressing was never rewarded during the third component. When the drive state was switched from hunger to thirst and the animals tested in extinction, they pressed more in the presence of the component stimulus that had been associated with the sucrose reward during training. A similar effect was observed during the extinction test of a second study in which the component stimuli had signalled non-contingent presentations of either the sucrose or pellet rewards in the absence of the lever. This suggests that the instrumental irrelevant incentive effect observed in the first experiment was due, at least in part, to the Pavlovian relationship between the component stimuli and the reinforcers during training. In fact, when the size of the effects controlled by purely Pavlovian and supposedly instrumental contingencies was compared directly in the final study, no difference could be detected.     

Assessment Methods for Eating Behavior,Food Intake and Food Preferences

Abstract

A survey is provided of methods for the assessment of food intake and eating behavior in clinical and research contexts. Five methods of dietary assessment in the epidemiological tradition are presented: dietary history, 24-hour recall, 7-day recall, 7-day record and food-frequency. Behavioral measures of eating behavior, food choice, food preference and hunger are presented and studies of their reliability and validity and other methodological properties are reviewed. Methodological recommendations and suggestions for future research are provided.