Acquisition of a second-order classically conditioned response.

Following alleyway food-training on a 50% random partial reinforcement schedule and 10 forward 1st-order (CS1-UCS) conditioning trials elsewhere, forward 2nd-order (CS2-CS1) classical conditioning trials were initiated for 40 female albino rats (Group 1) and equivalent but backward (CS1-CS2) training was started for 20 additional Ss (Group 2). After each set of 2 CS1-UCS and 3 CS2-CS1 trials (or 3 CS1-CS2 trials for Group 2) were given, the CS2 was presented in the goal area of the alley on nonreinforced trials to assess its suppressing effect on total running times. While the performance of Group 2 to the CS2 was unchanged as a function of conditioning trials, Group 1 evinced both increasing suppression and skin conductance levels as 2nd-order training progressed. Maximum suppression was obtained by the 12th CS2-CS1 trial. (French summary) (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thiamin deprivation in ventromedial hypothalamic hyperphagic rats: Anorexia, specificity of food aversion, and a dietary consideration.

In 3 studies, the anorexic consequence of thiamine deprivation was investigated in ventromedial hypothalamic (VMH) hyperphagic CD male rats under either high-fat or low-fat (HF and LF, respectively) thiamine-free diet conditions. The LF diet maintained feeding significantly longer in thiamine-deprived VMH Ss than in intact Ss, whereas the HF diet sustained feeding in thiamine-deficient intact Ss and accelerated anorexia onset in vitamin-B1-deprived VMH Ss. This effect was noted under both ad lib and pair-feeding conditions. Thiamine-deprived VMH Ss subjected to weight control developed anorexia sooner than intact Ss regardless of the diet employed. The VMH Ss fed an HF diet failed to resume feeding after thiamine readministration, which is interpreted as a permanent aversion to this diet. The relation between dietary intake and conditioned taste aversion is discussed with reference to the VMH and intact rats. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schedule-induced polydipsia suppresses pituitary-adrenal activity in rats.

The effects of schedule-induced polydipsia (SIP) on pituitary-adrenal activity, as indicated by plasma levels of corticosterone, were examined in 3 experiments in which a total of 52 Sprague-Dawley rats were given daily sessions on a fixed time 60-sec intermittent-feeding schedule. Half of the Ss in each experiment had water available during sessions. Ss with water available in the experimental chamber exhibited SIP. Blood samples were taken at various steps in the procedure and also after the opportunity to drink during sessions was removed. Results indicate that (a) schedule-induced drinking suppresses pituitary-adrenal activity, (b) corticoid suppression may become a conditioned response to drinking in the chamber, and (c) corticoids return to presession levels following removal of water from the chamber. In view of these findings, it is hypothesized that SIP may serve an arousal-reducing role in intermittent-feeding situations. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sham feeding in rats after ventromedial hypothalamic lesions and vagotomy.

Two studies examined sham feeding in female Sprague-Dawley rats with ventromedial hypothalamic (VMH) lesions with or without abdominal vagotomy. In Exp I, intact Ss consumed more than twice as much sweet milk during 1-hr tests of sham feeding as they did when feeding normally. Ss with VMH lesions showed exaggerated sham feeding, which was elevated almost four-fold over their already high normal feeding baseline. In Exp II, vagotomy substantially reduced sham feeding in Ss with VMH lesions. After vagotomy, VMH Ss sham fed half as much as nonvagotomized VMH Ss. Vagotomy did not, however, reduce sham feeding to control levels. Results are consistent with the hypothesis that VMH hyperphagia arise from exaggeration of orosensory responsiveness, which is, in part, a consequence of perturbed vagal function. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: III. Thermal determinants of early ingestive responding.

High ambient temperatures (38°C) stimulated high spontaneous levels of activity and high frequencies of behaviors normally associated with ingestion (mouthing and probing), particularly in young, 3- and 6-day-old Charles River CD rat pups (Exp I). The level of spontaneous behavior was highly correlated with body temperature and also depended on deprivation condition. Temperature played an important role in determining responses to food stimuli as well. When Ss were fed by oral infusion (Exp II) or by placing milk on the floor beneath them (Exp III), warm ambient temperatures were required for active ingestion. In Exp IV, body temperature and ambient temperature were manipulated independently to assess their relative importance for Ss' feeding behavior. Ss with a low (29°C) or normal (34°C) core temperature at the start of testing were fed in either a 24°C or a 34°C ambience. Regardless of body temperature, Ss' levels of intake, activity, mouthing, and probing were higher in a warm than in a cool ambience. Therefore, the suppressed ingestive behavior of Ss fed at cool temperatures occurred not simply because Ss became hypothermic and inactive. Perceived warmth appears to be a significant contextual cue that regulates pups' responses to food stimuli. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adrenal responses to reinforcement and extinction: Role of expectancy versus instrumental responding.

Measured plasma corticosterone levels during operant conditioning to determine the effect of reinforced and nonreinforced responding (extinction) on adrenal activation; Ss were 44 male Long-Evans rats. The influence of instrumental responding was assessed by comparing trained Ss with yoked Ss that received a matched reward schedule in the absence of an operant task. Reinforcement sessions resulted in a significant decrease in adrenal secretion at 20 min but not at 5 min, whereas extinction caused a rapid increase in corticosterone levels at 5 min and an even greater elevation at 20 min. Comparison of the operant and yoked Ss showed that this effect of reinforcement and extinction was not dependent on instrumental responding, but rather on the receipt or withdrawal of the expected reward. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy restriction with high-fat diet enriched with coconut oil gives higher UCP1 and lower white fat in rats

OBJECTIVE: To investigate the effects of overfeeding on a high fat diet, enriched in coconut oil, and the influence of food restriction on the uncoupling protein (UCP1) expression and on body fat content. DESIGN AND SUBJECTS: In experiment I, female Wistar rats were fed ad libitum either a normal-fat diet (control group, C) or a high-fat diet (HF), enriched in coconut oil, for 7 weeks. In experiment II, HF rats after finishing experiment I were fed (for 3 weeks) either the normal-fat diet (group CAHF, Control After High Fat) or food restricted diets which provided 60% of the energy intake of group CAHF: a group fed a low-energy, normal-fat diet (LENF) and another fed a low-energy, high-fat diet (LEHF). MEASUREMENTS: Body and fatty depot weights. Food intake. Protein and UCP1 levels of interscapular brown adipose tissue. RESULTS: High-fat diet feeding promoted an increase in body fat content, body weight and UCP1 levels. Energy restriction induced similar body weight reduction in groups LENF and LEHF. However, some adipose depots were more strongly reduced in the rats fed the high-fat diet enriched in coconut oil (group LEHF) than in the rats fed the normal-fat diet (Group LENF). Specific UCP1 was 2.0 (group LENF) and 3.4 (group LEHF) times higher than in controls (group CAHF). CONCLUSION: The coconut-oil enriched diet is effective in stimulating UCP1 expression during ad libitum feeding and in preventing its down regulation during food restriction, and this goes hand in hand with a decrease of the white fat stores.     

Effects of acute trimethyltin exposure on appetitive acquisition and extinction performance in the adult rat.

16 adult male Sprague-Dawley rats were given an intragastric infusion of 7 mg/kg of trimethyltin chloride (TMT), and 16 additional Ss (controls) received saline, to investigate TMT's effect on Ss' appetitive acquisition and extinction performance. Ss from each condition were divided into 2 equal groups and trained with either partial or continuous reinforcement (PRF or CRF) in a straight-alley maze 21 days after dosing. The acquisition training phase contained 40 trials (4 trials/day) and was followed by 20 trials of extinction training (4 trials/day). Analyses performed on total speed revealed that TMT Ss performed at lower levels during acquisition than controls, regardless of schedule condition. Also, the rate of resistance to extinction was significantly reduced for TMT Ss compared with that of controls, regardless of the training schedules used during acquisition. A PRF extinction effect was observed for both control and TMT Ss, independent of dose regimen. PRF training occasioned greater persistence during extinction than did CRF training. Findings are discussed in terms of issues relating to TMT-induced hippocampal lesions. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diet palatability modulates sham feeding in VMH-lesion and normal rats: Implications for finickiness and evaluation of sham-feeding data.

Examined the capacity for taste cues to modulate the food intake of 24 ventromedial hypothalamic (VMH) and normal Long-Evans rats. Ss were implanted with a chronically indwelling gastric cannula and sham fed (cannula open) or normally fed (cannula closed) liquid diets varying in sucrose content. VMH Ss were maintained at control body-weight levels. For both groups, the discrepancy in consumption between sham and normal feeding situations depended on the sweetness of the diet. The implications of this finding for studies using sham feeding to assess putative feeding control signals are discussed. VMH lesions exaggerated the sensory control of food intake. Under sham-feeding conditions, increases in the sweetness of the diet led to disproportionately large increments of food intake in VMH Ss relative to controls. Data support the existence of a finickiness component in the VMH syndrome and allude to the nature of the physiological disturbance underlying this behavior change. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of social competence in borderline essestial hypertension.

Examined the social competence of 22 male borderline hypertensives (aged 19–45 yrs) in relation to cardiovascular responsivity to a behavioral role-play test (RPT) of assertiveness. Ss were divided into 2 groups: one group experienced large increases in pulse pressure (PP) in response to social challenge (Group 1), while the other group showed small changes in PP (relatively equal rises in systolic and diastolic blood pressure) under the same stimulus condition (Group 2). These differential group patterns of cardiovascular response were specific to interpersonal stressors because the groups did not differ in reactivity to cognitive challenges. Group 2 Ss evidenced unassertive responding on a role-play test of negative assertion and were rated by significant others as the least socially competent as compared to normotensive controls (who received the highest social competence ratings) and Ss in Group 1. Group 1 Ss responded in an inappropriately assertive fashion on the RPT and had shorter response latencies during the RPT than Ss in Group 2, suggesting that Ss in Group 2 had greater levels of interpersonal anxiety. Findings indicate that hostile inappropriate assertiveness and inappropriate submissiveness may be associated with hypertension. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal and content variations as determinants of infants' visual control of verbal stimulations.

20 93–119 day old infants were presented with utterances varying in content or temporal structure that were contingent on fixation on a visual target. Treatment A consisted of utterances of equal duration and continually varying content. Treatment B consisted of utterances of slightly variable duration (temporal runs) and continually varying content. Treatment C included utterances organized in temporal runs and was composed of partial content variations (content runs). For Group AB, each A trial alternated with a B trial 4 times. For Group AC, each A trial alternated with a C trial 4 times. Half of the Ss in each group received Treatment A as their 1st trial; half of the Ss in Group AB received Treatment B; and half of the Ss in Group AC received Treatment C as their 1st trial. Group AB Ss showed a longer total fixation time than those of Group AC, with a more homogeneous distribution of number of fixations across treatments. Mean length of fixations was longer for Treatment A than B in Group AB, whereas Group AC showed a longer mean length of fixation for Treatment C relative to Treatment A. Those with Treatment B or C as their 1st trial looked more frequently at the target, and their decrease in looking time over trials showed a linear trend, whereas Ss with Treatment A at first displayed irregular decreases. These differences between groups and presentation orders suggest that 3-mo-old infants are sensitive to differences in linguistic material. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Training clients to help themselves: Outcome effects of training college student clients in facilitative self-responding.

Used training in facilitative self-responding to help clients alter what they say to themselves. The training was compared to empathy-based individual counseling for personal-social problems. 20 undergraduates served as Ss. Treatment consisted of 6 1-hr weekly sessions. Ss were compared on posttests of empathy, regard, genuineness, and concreteness of their self-help responses and self-ratings and observer ratings of interpersonal functioning and improvement on specific counseling goal behaviors. Significant treatment and Treatment * Measures interaction effects were observed, indicating significant differences in favor of the trained group for 6 of the 8 variables. Group differences on the 2 self-rating measures were not significant. The fact that minimally facilitative levels of self-responding and positive change as rated by observers was attained only by the trained group indicated the usefulness of the technique for self-help training. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some determinants of a natural food aversion in Norway rats.

Adult male Long-Evans rats were permitted to feed on the carcasses of adult male rodents, freshly sacrificed by CO? asphyxiation. In a 2-choice preference test (Exp I), hungry Ss were offered 1 conspecific and 1 house mouse, the pair of carcasses being either intact or skinned. 18 Ss offered intact carcasses fed on the mouse or on neither carcass, but 18 Ss offered skinned carcasses fed indiscriminately, usually on both carcasses. In Exp II, 10 hungry Ss that earlier had observed a cagemate feeding on intact conspecific carcasses fed more readily on a similar carcass during a single-choice test than did 8 controls. In Exp II, 20 food-deprived Ss (96 hrs) fed more readily and consumed more tissue from an intact conspecific carcass than did 20 nondeprived Ss. It is concluded that the aversion to feeding on the intact carcass of a freshly sacrificed adult conspecific is deprivation dependent and is mediated by chemoreceptive stimuli from the skin and/or fur. The aversion is diminished by social facilitation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adrenocortical response to hypertonic saline in rats with lateral hypothalamic lesions.

Used plasma corticosterone levels to assess the response to stress induced by ip injections of hypertonic saline in 27 male albino Harlan-Sprague rats with lateral hypothalamic (LH) or sham lesions. Ss with LH lesions displayed a corticosterone response equal to that of normal Ss under basal conditions, after control injections of isotonic saline, and 20 min after injection of hypertonic saline (1.5 M, 1.0 ml/100 g of body weight). The corticosterone response of Ss with LH lesions, however, was significantly less than that of normal Ss 90 min after injection of hypertonic saline when no water was available. With access to water, normal Ss displayed substantial drinking (14.5 ml/90 min), which resulted in a reduction in plasma corticosterone concentrations to a level observed after a control injection of isotonic saline, but the little water ingested by Ss with LH lesions (2.5 ml) had no effect on the pituitary-adrenal system. It is concluded that the failure of Ss with LH lesions to drink following a hydrational challenge is not the result of an exaggerated response to stress. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feeding, activity, and body temperature following 6-hydroxydopamine lesions in diabetes (db/db) mice.

Reductions in central catecholamines produced by intraventricular injections of 6-hydroxydopamine (6-OHDA) cause weight loss and decreased plasma glucose in diabetes (db/db) mice. The present study examined the effects of this treatment in short-term (64-day) and long-term (120-day) survival groups of female diabetes (C57 BL/KsJ-db/db) and lean mice. Phenotypically heterozygotes (db/m) and homozygotes (m/m) were used as controls. Diabetes Ss treated with 6-OHDA decreased food intake, lost weight, and maintained a lower weight than vehicle-treated controls until vehicle-treated Ss began to enter the terminal stages of the syndrome, indicated by a loss of body weight. Diabetes Ss given 6-OHDA lost weight despite reduced body temperatures and activity levels. Blood glucose levels were always lower in 6-OHDA than in ad lib fed vehicle-treated db/db Ss. The 6-OHDA treatment also improved pancreatic islet granulation. Pair feeding vehicle-treated with 6-OHDA-treated db/db Ss did not halt weight gain in the vehicle-treated group. However, measurement of carcass fat indicated similar losses in db/db-6-OHDA Ss and vehicle-treated Ss when the vehicle group was pair-fed with lean controls. Treatment with 6-OHDA produced long-term improvement in the diabetes syndrome, but the decreased body weight of the 6-OHDA-treated diabetes Ss could not be completely accounted for by changes in food intake or energy expenditure. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Efficacy of alpha biofeedback training in elevating mood.

Tested the hypothesis that alpha brain wave feedback training elevates mood, using 3 groups of 8 Ss each: Group I underwent training, Group 2 kept the alpha feedback signal off, and Group 3 named titles of tunes. Ss completed a perceived success questionnaire and the Multiple Affect Adjective Checklist. The hypothesis was not supported by the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retardation of jump-up escape responding in rats pretreated with different frequencies of noncontingent electric shock.

Pretreated 5 groups of 5 male albino Sprague-Dawley rats each with either 0, 10, 40, 80, or 160 5-sec, 1.5-ma pulsed shocks. Ss were then given escape training in a jump-up box. The number of failures to escape was an increasing function of pretreatment shock frequency. Ss that showed the retardation effect escaped irregularly with short latencies on some trials and failures to escape on others. After escape training, Ss in the 0-shock pretreatment group were given 80 5-sec, 1.5-ma pulsed shocks and then exposed to additional escape training in the jump-up box. These Ss did not show the retardation effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of spatial information processing in aged rats.

The spatial learning abilities of young, middle-age, and senescent rats were investigated in 2 experiments using several versions of the Morris water maze task. In Exp I, Long-Evans hooded rats were trained to find a submerged escape platform hidden within the water maze. Aged Ss exhibited acquisition deficits compared with either young or middle-age Ss. With continued training, all age groups eventually achieved comparable asymptotic levels of performance. To identify the basis of the age-related impairments observed in Exp I, naive young and aged Ss in Exp II were initially tested for their ability to locate a cued escape platform in the water maze. The escape latencies of both young and aged Ss rapidly decreased to equivalent asymptotic levels. Following cue training, young Ss exhibit a significant spatial bias for the region of the testing apparatus where the platform was positioned during training. In contrast, aged Ss showed no spatial bias. Training was continued in Exp II using a novel submerged platform location for each S. During these place training trials, the escape latencies of senescent Ss were longer than those of young Ss. These impairments were also accompanied by a lack of spatial bias among aged Ss relative to young controls. Results indicate that age-related impairments in water maze performance reflect a specific deficit in the ability of aged rats to utilize spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hyperinsulinemia in rats with ventromedial hypothalamic lesions: Role of hyperphagia.

Examined the relation of hyperinsulinemia to hyperphagia in 18 female hooded Long-Evans rats with lesions of the ventromedial hypothalamus (VMH). Plasma insulin and glucose levels were assayed after a 4-hr fast and 17 min after the initiation of a meal (6 ml of sweetened milk in 7 min) in 8 other Ss with sham lesions, VMH Ss maintained at preoperative body weight by food restriction, and VMH Ss fed ad lib. Both VMH groups displayed basal and postabsorptive hyperinsulinemia compared with the sham-operated group, but insulin levels were greatest under the ad lib feeding condition. It is suggested that VMH hyperinsulinemia is due both to a primary effect of the lesion and to hyperphagia and that marked obesity can result in the absence of basal hyperinsulinemia as a result of hyperphagia with consequent postabsorptive hyperinsulinemia. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arousal of frustration following gradual reductions in reward magnitude in rats.

16 male Holtzman rats were assigned to each of 4 groups; Ss were given a 14-pellet reward for 60 runway acquisition trials. During a subsequent 18-trial shift phase, one group was shifted to a 1-pellet reward on Trial 1, a 2nd was shifted on Trial 13, and a 3rd was given 1 less pellet each trial and then 1 pellet for the last 6 trials. The speeds of all 3 groups decreased to a level below that of a control group given a 1-pellet reward throughout training. All Ss were then given hurdle-jump training to escape from the 1-pellet reward to a neutral box. All 3 shifted groups showed acquisition of the response, whereas the control group did not. Results indicate that both gradual and abrupt reward reductions arouse frustration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)