Effects of combined lead and cadmium exposure: Changes in schedule-controlled responding and in dopamine, serotonin, and their metabolites.

Adult male rats were maintained on 1 of 4 ad-lib diets: Group Control-Diet received a normal laboratory diet that contained no added chemicals; Group Lead-Diet received a diet containing 500 ppm (parts per million) lead; Group Cadmium-Diet received a diet containing 100 ppm cadmium; and Group Lead-Cadmium Diet received a diet containing both 500 ppm lead and 100 ppm cadmium. After 60 days of exposure to their respective diets, animals were placed on restricted diets (15 g/day) of the identical food received during the exposure period. Each animal was trained to lever press on an FI 1-min schedule for 21 sessions (1 session/day). The results of schedule training showed that lead alone or cadmium alone was associated with increased lever pressing relative to control diet. However, when lead and cadmium were exposed jointly, performance was not significantly different from control performance. Similar attenuation of effects were observed for central neurotransmitter functions. Specifically, disturbances in dopamine and serotonin turnover that were produced by lead alone were attenuated by the cotreatment of cadmium and lead. Possible accounts of the apparent antagonism between cadmium and lead are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increasing the attractiveness of college cafeteria food: A reactance theory perspective.

Examined attitudinal effects of the elimination of a free behavior in a field experiment employing 27 female college students. Ss completed a survey, giving a rating of their cafeteria food. 9 days later they randomly received 1 of 3 communications: (a) elimination condition-eliminating their cafeteria use for 2 wks; (b) control condition-eliminating carbonated beverages; or (c) control condition-announcing a movie presentation. 5 min after receiving the communication, the Ss again completed the survey rating the cafeteria food. Only the elimination condition showed a greater positive reevaluation of the food as reflected by difference scores for the pretest and posttest ratings. Results are discussed in terms of contradictory hypotheses of J. Brehm's (1972) reactance theory and R. A. Wicklund's (l972) concept of prior exercise of behavioral freedom. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of initial-pecking consequences on subsequent pecking in young chicks.

White Leghorn cockeral chicks ? and 2? days old received saline or LiCl injection immediately following their 1st feeding experience. When retested 5 hrs later 2?-day-old Ss that had received saline increased their pecking rate, but ?-day-old Ss showed no change. Only 2?-day-old chicks, therefore, appear to associate ingestion of food with long-term positive consequences. Ss of both ages, on the other hand, greatly reduced pecking when retested 5 hrs after LiCl injection. Thus, ?- and 2?-day-old chicks are capable of forming an association between pecking and its long-term consequence when the consequence is aversive. When LiCl injection was not contingent on pecking, following the initial feeding session by 6 hrs, Ss did not reduce retest pecking rates. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lead levels in exposed herring gulls: differences in the field and laboratory

We compared blood lead levels for herring gull (Larus argentatus) chicks exposed at two days of age in the field and the laboratory. One randomly selected chick in each family of three was injected with lead, the second with a sterile saline solution, and the third was not injected. Field birds were then completely free-living, and were entirely cared for by their parents. Blood was drawn at 35 or 45 days of age for comparison with laboratory-reared chicks. In both the laboratory and the field, blood lead levels were positively related to dose, and concentrations were lower at 45 than at 35 days of age. However, at each dose, the field birds had lower levels than did the laboratory birds. We postulate that this relates to higher overall activity and accelerated bone development in the field, and perhaps to a move varied diet. Wild young gulls were mobile and practiced flight more often than did laboratory-reared gulls. Growth metabolic, and behavioral factors may enhance deposition of lead in the bone, reducing blood lead. Thus, both in ecological risk assessments and in using birds as bioindicators, caution is required in extrapolating from laboratory studies in field conditions.     

Assessing yourself as an emotional eater: Mission impossible?

Objective: The extent to which individuals are emotional eaters has typically been assessed by people’s self-reported desire to eat when they experience negative emotions. Elevated scores on these emotional eater scales have been associated with eating pathology and obesity. However, evidence that individuals scoring high on these scales truly increase their food intake during emotional encounters is inconclusive. The current studies tested whether emotional eater scales capture the proposed tendency to eat when feeling emotional. Design: In four experiments with different emotion induction procedures, female participants were randomly assigned to negative emotion or control conditions. In the control conditions positive or no emotions were induced. Next, food consumption was assessed by bogus taste tests. Main Outcome Measures: Emotional eater status, emotional experience, and actual consumption of different food types. Results: Individuals describing themselves as emotional eaters did not increase food intake during emotional encounters as compared to control conditions or individuals not judging themselves as emotional eaters. Conclusion: The results suggest that self-reported emotional eaters do not increase food intake during emotional encounters in the laboratory. Implications of these findings are discussed, including the idea that it may be complex to adequately assess one’s own emotional eating behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lower begging responsiveness of host versus parasitic brown-headed cowbird (Molothrus ater) nestlings is related to species identity but not to early social experience.

The survival of young brood parasites depends critically on their many adaptations to exploit hosts. Parasitic survival is particularly related to competitive superiority for foster parental care whenever host young are not destroyed in parasitized nests. Brown-headed cowbirds (Molothrus ater) are generalist obligate parasites whose early social environments are unpredictable regarding host species and numbers of nestmates. Young avian brood parasites typically beg more intensively and loudly than foster siblings, but an untested prediction is that young parasites are also more likely to respond by begging to a wider variety of stimulus types. Avian vocalizations were used in a playback experiment to stimulate begging behavior in cowbird hosts. Compared with age-matched cowbird nestlings, hosts begged less frequently to acoustic stimuli, and lower begging responsiveness was irrespective of whether hosts had been reared in parasitized nests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of fixational eye movements on the response of neurons in area MT of the macaque

After milk ejection, piglets spend several minutes massaging their own teats on the sow. We examined whether this behaviour could be a mammalian counterpart to begging in young birds, and hence be explained by theories of honest begging. In one experiment, the behaviour of piglets was examined in relation to their previous milk intake. In each of 16 litters, one focal piglet was exposed to three treatments for three consecutive sucklings: 'no milk', where the piglet was withheld from the teat during milk ejection; 'extra milk', where it was fed 10 ml of extra milk directly after milk ejection; and 'control', when it received its normal intake. Average massage duration in the next three sucklings was significantly longer in the 'no milk' than in the control piglets. 'No milk' pigs massaged more intensely (number of massage movements/min), were more persistent in attempting to maintain udder contact and spent less time away from the udder. However, there were no significant differences between 'control' and 'extra milk' treatments. In a second experiment, in which we manually massaged teats for 0, 3 or 10 min, we found no significant effect of massage duration on milk output (measured by weighing piglets before and after milk ejection), although massage tended to increase output. We conclude that post-sucking massage in piglets has a number of aspects similar to honest begging in birds. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.     

Development of food recognition in young chicks: I. Maturation and nutrition.

Investigated age and food ingestion as factors influencing food recognition in 5 experiments with a total of 338 Burmese Red Junglefowl chicks. Newly hatched chicks pecked indiscriminately at sand and food; by 3 days of age, pecks were directed primarily at food. Pecking at food or sand had little effect on subsequent pecking at either stimulus until the chicks were 2-3 days old. Ingestion of food then served to facilitate pecking, but such facilitation did not occur until 10 min to 1 hr after ingestion. The effects that occurred on Day 3 were not specific to the stimulus pecked, but pecking at food and sand increased in frequency when the chicks had ingested food. Control experiments using a forced-feeding technique showed that these effects were due to ingestion of food and occurred only if food ingestion was associated with pecking. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory cues mediate food selection by young chicks

An illness-induced aversion paradigm was used to assess the possible influence of olfactory cues on food selection by young chicks. At 2-3 days posthatching, chicks were exposed briefly to food scented with a novel odor (orange) followed by an injection of LiCl or saline. LiCl-injected chicks subsequently displayed stronger avoidance of orange-scented food than did the controls. Chicks in a second experiment were preexposed to novel-scented food, then either injected with LiCl or not injected. The LiCl chicks, but not the controls, later avoided food associated with the preexposure odor (relative to food treated with an unfamiliar odorant). Two- to three-day-old chicks are capable of associating specific food odors with negative consequences and modify their feeding behavior as a function of such experience.     

The magic cup: Great apes and domestic dogs (Canis familiaris) individuate objects according to their properties.

Despite current interest in dog (Canis familiaris) cognition, very little is known about how dogs represent objects and how they compare with other species, such as the great apes. Therefore, we investigated how dogs and great apes (chimpanzees [Pan troglodytes], bonobos [Pan paniscus], orangutans [Pongo pygmaeus], gorillas [Gorilla gorilla]) individuate objects in a classical violation of expectation paradigm. We used a container (magic cup) with a double bottom that allowed us to change the type of food that subjects had seen being placed in the container. Using a 2 × 2 design, we varied whether subjects received a generally preferred food and whether the food was substituted (surprise trials) or not (baseline trials). Apes showed increased begging and looking behaviors and dogs showed increased smelling behavior. Both species stayed near the experimenter more frequently in the surprise trials compared with baseline trials. Both species reacted to positive (i.e., good food substituted for bad food) and negative (i.e., bad food substituted for good food) surprises. These results suggest that apes and dogs were able to individuate objects according to their properties or type in comparable ways. In addition, we looked for frustration and elation effects, but subjects' behaviors were not influenced by the food they saw and which they received in previous trials. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The influence of job familiarity and impression management on self-report measure scale scores and response latencies.

Two studies were conducted to examine the effects of job familiarity and impression management on response latencies and scale scores for measures of personality and situational judgment. In a laboratory study using university students and a field study using U.S. Border Patrol Agent applicants, impression management was generally associated with faster personality item responses when job familiarity was high and with slower responses when job familiarity was low. Both impression management and job familiarity were associated with personality item responses that were more likely to lead to a job offer. The field study revealed a similar pattern of results for situational judgment scale response latencies, although only impression management was associated with item responses that were more likely to lead to a job offer. The implications for using response latencies to detect impression management on self-report measures are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The timing of food availability affects growth in chicks

Three experiments challenged the ability of domestic chicks to grow normally by differentially restricting when and for how long food was available. In Experiments 1 and 2, food was available for six 1-hr, three 2-hr, two 3-hr, or one 6-hr (a.m., p.m.) periods/day over the first 3 posthatch weeks. Control groups received continuous access to food. In Experiment 3, different amounts of light surrounded the 6-hr feeding period. In Experiments 2 and 3, chicks composed their own diets from separate sources high in protein or carbohydrate. Except for the single 6-hr meal preceding dark, large meals at other times of day impaired growth--primarily because chicks consumed insufficient dietary protein and ate less earlier in the light phase. We conclude that both the amount eaten and the proportion of the diet consumed as protein at given times of the day are phylogenetically acquired strategies that fit the omnivorous, diurnal chicken to its niche, independent of its momentary requirements, and appear early in development.     

Cortical, hippocampal, and striatal mediation of schedule-induced behaviors.

The sequential occurrence of licking, locomotor activity, entries into the food magazine (panel pressing), and nonreinforced lever pressing engendered by a periodic schedule of food presentation were measured in each 60-s interreinforcement interval in normal and brain-damaged rats. The development of these responses was measured over 20 days in different groups of food-deprived rats that had received aspirations of the hippocampus, small lesions of the cortex overlying the hippocampus (hippocampal-operated control group), decortication, or 6-hydroxydopamine lesions of the caudate nucleus or nucleus accumbens. All lesions produced distinctive patterns of change in the measured behaviors, and dissociations as well as similarities in their effects were evident. These results are discussed with respect to dissociations in the motor and motivational effects of the various lesions and in terms of contemporary hypotheses of schedule-induced behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats alternate on a dry-land but not swimming-pool (Morris task) place task: Implications for spatial processing.

Groups of rats were rewarded with food for traveling from a start point to 2 different locations while their alternations in choice between those locations on 2 daily trials were recorded. In one experimental condition, the rats swam and received food once they climbed upon a platform that was hidden just below the surface of the water at the food location. In the other condition, the rats walked to reach the food. It was found that the rats did not alternate their choices between target locations when swimming but that they did alternate target choices when walking. Even experience in alternating when walking did not produce reliable alternation when swimming. It is proposed that rats treat escape (swimming) and search (walking) tasks in different ways, and this difference is discussed with respect to the possibility that different central processes may be used in the task solutions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal lesions impair retention of discriminative responding based on energy state cues.

The present research investigated the hypothesis that the hippocampus is involved with the control of appetitive behavior by interoceptive “hunger” and “satiety” signals. Rats were trained to solve a food deprivation intensity discrimination problem in which stimuli produced by 0-hr and 24-hr food deprivation served as discriminative cues for the delivery of sucrose pellets. For Group 0+, sucrose pellets were delivered at the conclusion of each 4-min session that took place under 0-hr food deprivation, whereas no pellets were delivered during sessions that took place when the rats had been food deprived for 24 hr. Group 24+ received the reverse discriminative contingency (i.e., they received sucrose pellets under 24-hr but not under 0-hr food deprivation). When asymptotic discrimination performance was achieved (indexed by greater incidence of food magazine approach behavior on reinforced compared with nonreinforced sessions), half of the rats in each group received hippocampal lesions, and the remaining rats in each group were designated as sham- or nonlesioned controls. Following recovery from surgery, food deprivation discrimination performance was compared for lesioned and control rats in both Groups 0+ and 24+. Discriminative responding was impaired for rats with hippocampal lesions relative to their controls. This impairment was based largely on elevated responding to nonreinforced food deprivation cues. In addition, hippocampal damage was associated with increased body weight under conditions of ad libitum feeding. The results suggest that the inhibition of appetitive behavior by energy state signals may depend, in part, on the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of poisoning on predatory and ingestive behavior toward artificial prey in rats (Rattus norvegicus).

Ingestion of novel prey by vertebrate predators that is followed by illness typically decreases the predators' eating the prey more readily than their pursuing or killing it. We used artificial prey-food items (rolling ball bearings that predicted food pellets) to model and extend this finding in laboratory rats. During daily experimental sessions presentations of a novel bearing–food combination were intermixed with presentations of a familiar bearing–food combination. The poisoned animals received lithium chloride injections after each session. Poisoning markedly decreased ingestion of the novel food without decreasing the frequency of contact (nose, seize, carry, or chew) with the novel bearing predicting that food. However, poisoning did significantly decrease the average duration of contact with the novel bearing. Poisoning did not decrease behavior toward the familiar food and bearing. After moderate exposure to pairings of the novel food and bearing, poisoning decreased behavior toward both novel and familiar food and bearings. The results indicate that important aspects of predation can be simulated and examined in the laboratory by using artificial prey-food items. These results also support the conclusions that predatory behavior and ingestion reflect separable modes of behavior and that the presence of novel prey interferes with the generalization of poisoning effects to familiar prey. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Galanin stimulation of feeding is blocked by the addition of a response requirement.

Administration of the neuropeptide galanin increases food intake in laboratory rats and mice, however this increase has only been observed under conditions of free-feeding. As there is a growing distinction between consummatory and instrumental behavior, we assessed whether galanin would differentially affect food consumption when food was freely available or when the same food was response-contingent. We also tested whether food restriction would interact with galanin's effect on food consumption in either condition. As in previous studies, galanin significantly increased food consumption under free access conditions. However, when food was contingent upon lever-pressing, galanin had no such stimulatory effect. Food-restriction increased basal feeding levels in both tasks but there was no interaction between food restriction and free or response-contingent food intake. These results demonstrate that galanin-induced feeding stimulation is limited to conditions of free access and support the theoretical distinction between consummatory and instrumental behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of d-amphetamine and cocaine on strained ratio behavior in a repeated-acquisition task

Pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors. When the fixed-ratio requirement for food presentation was five completions of the chain, d-amphetamine and cocaine disrupted the behavior. As the dose of each drug was increased, the overall response rate decreased, the overall accuracy was impaired (i,e., percent errors increased), and there was less within-session error reduction (acquisition). In contrast, when the fixed-ratio requirement was either 20 or 50 completions of the chain, certain doses of both drugs produced large increases in the overall response rate by eliminating the extended pausing (ratio strain) that was characteristic of the control sessions. These rate-increasing effects were accompanied by error-decreasing effects, both during acquisition and after the response chain had been acquired. Taken together, the results show that the effects of d-amphetamine and cocaine on behavior in a repeated-acquisition task can be modulated by manipulating the value of the fixed-ratio schedule maintaining the behavior.     

Drug and food-deprivation modulation of activity in rats given chronic dietary lead: significance of type of activity measure

In Experiment 1, rats were given a 1% lead acetate diet from Day 100 of life to the termination of the experiment. After 82 days of lead feeding behavioral tests were started. Lead exposure increased wheel-turning hyperactivity produced by food deprivation and phenylethylamine injection. Lead produced no activity change in the unchallenged condition. In the open field, lead-exposure rats were less responsive to the stimulating action of PEA and amphetamine and to the sedating action of pentobarbital. In Experiment 2, the interaction of lead with food deprivation of PEA on wheel-turning was replicated in naive animals given only a 32-day exposure. Chemical analysis was made of tissues. Ingested lead entered the brain. Regional steady-state levels of brain norepinephrine, dopamine and serotonin were not altered by lead treatment when measured following four days of starvation at a time when lead-induced behavioral change was distinct. It was concluded that pharmacological challenges on activity may be sensitive indicators of lead exposure, but the type of activity measure is critical.