Preferences for and against stimuli paired with food.
(17/1652)
Pigeons were presented with a concurrent-chains schedule in which terminal-link entries were assigned to two response keys on a percentage basis. The terminal links were fixed delays that sometimes ended with food and sometimes did not. In most conditions, 80% of the terminal links were assigned to one key, but a smaller percentage of the terminal links ended with food for this key, so the number of food reinforcers delivered by the two alternatives was equal. When the same terminal-link stimuli (orange houselights) were used for both alternatives, the pigeons showed a preference for whichever alternative delivered more frequent terminal links. When different terminal-link stimuli (green vs. red houselights) were used for the two alternatives, the pigeons showed a preference for whichever alternative delivered fewer terminal links when terminal-link durations were long, and no systematic preferences when terminal-link durations were short. This pattern of results was consistent with the predictions of Grace's (1994) contextual choice model. Preference for the alternative that delivered more frequent terminal links was usually stronger in the first few sessions of a condition than at the end of a condition, suggesting that the conditioned reinforcing effect of the additional terminal-link presentation was, in part, transitory. (+info)
Essential amino acid deficiency enhances long-term intake but not short-term licking of the required nutrient.
(18/1652)
Rats can adjust their nutrient intake in response to nutritional deficiency. This phenomenon has been described extensively for sodium deficiency, whereas other nutrient deficiencies have not been explored thoroughly. Essential amino acid (EAA) deficiency represents a relevant model to describe adaptive changes in behavior resulting from deficiency. The purpose of these experiments was to examine more closely the behavioral responses that occur as a result of lysine (LYS) and threonine (THR) deficiency. Licking to LYS, THR, glycine and distilled water during 10-s trials was measured in control (CON) and EAA-deficient rats. Licking tests were conducted both before and after 23-h intake tests. Although EAA-deficient rats did not show increased licking to the deficient EAA in any of the brief-access tests, in all cases, they did initiate significantly more overall trials than did CON. The EAA-deficient rats also had elevated intake of the deficient EAA in long-duration tests. These findings suggest that LYS or THR deficiency does not emulate the behavioral properties of sodium deficiency in that it does not result in enhanced immediate licking responses to the limiting EAA in brief-access tests. Nevertheless, an appetite is expressed to the relevant EAA in a long-term intake test. (+info)
Effects of dietary viscosity and energy density on total daily energy consumption by young Peruvian children.
(19/1652)
BACKGROUND: Results of prior studies of the effect of viscosity reduction of high-energy-density, starch-containing diets on young children's energy intakes are inconsistent, possibly because of differences in the characteristics of the unmodified diets with which the low-viscosity diets were compared. OBJECTIVE: Our objective was to determine the effects of dietary viscosity and energy density on total daily energy consumption by young, non-breast-fed children. DESIGN: We measured the amount of food consumed and the duration of meals during 3 substudies, in each of which 3 study diets were offered for 4 consecutive days each in random sequence: high energy density, high viscosity (HD-HV); high energy density, low viscosity (HD-LV); and low energy density, low viscosity (LD-LV). The viscosity and energy density of the unmodified starch-containing HD-HV diet were varied across substudies to determine whether the effect of amylase liquefaction was related to the initial characteristics of the HD-HV diet. The viscosity of the HV diets ranged from 79000 to 568000 mPa s; energy density of the HD diets ranged from approximately 4.18 to 4.93 kJ (1.00-1.18 kcal)/g. Viscosity of the LV diets was approximately 3000 mPa s and the energy density of the LD diets was approximately 2.47 kJ (0.6 kcal)/g. RESULTS: In each substudy, children consumed more of the LD-LV diet (g kg body wt(-)(1) d(-)(1)) than of the other diets and more of the HD-LV diet than of the HD-HV diet (P < 0.001). Energy consumption from the HD-LV diet was greater than from the other diets (P < 0.001), but the energy intakes from the latter diets were not significantly different. CONCLUSION: Amylase liquefaction of HD-HV porridges resulted in increased energy consumption by young children. (+info)
Reduced K+ channel inactivation, spike broadening, and after-hyperpolarization in Kvbeta1.1-deficient mice with impaired learning.
(20/1652)
A-type K+ channels are known to regulate neuronal firing, but their role in repetitive firing and learning in mammals is not well characterized. To determine the contribution of the auxiliary K+ channel subunit Kvbeta1.1 to A-type K+ currents and to study the physiological role of A-type K+ channels in repetitive firing and learning, we deleted the Kvbeta1.1 gene in mice. The loss of Kvbeta1.1 resulted in a reduced K+ current inactivation in hippocampal CA1 pyramidal neurons. Furthermore, in the mutant neurons, frequency-dependent spike broadening and the slow afterhyperpolarization (sAHP) were reduced. This suggests that Kvbeta1.1-dependent A-type K+ channels contribute to frequency-dependent spike broadening and may regulate the sAHP by controlling Ca2+ influx during action potentials. The Kvbeta1.1-deficient mice showed normal synaptic plasticity but were impaired in the learning of a water maze test and in the social transmission of food preference task, indicating that the Kvbeta1.1 subunit contributes to certain types of learning and memory. (+info)
Deficits in memory tasks of mice with CREB mutations depend on gene dosage.
(21/1652)
Studies in Aplysia, Drosophila, and mice have shown that the transcription factor CREB is involved in formation and retention of long-term memory. To analyze the impact of differential CREB levels on learning and memory, we varied the gene dosage of CREB in two strains of mutant mice: (1) CREBalphadelta mice, in which the alpha and delta isoforms are disrupted, but a third isoform beta is strongly up-regulated; (2) CREBcomp, a compound strain with one alphadelta allele and one CREBnull allele in which all CREB isoforms are disrupted. To minimize genetic background effects, CREB mutations were backcrossed into a C57BL/6 and a FVB/N strain, respectively, and studies were performed in F1 hybrids from these lines. CREBcomp but not CREBalphadelta F1 hybrids were impaired in water maze learning and fear conditioning, demonstrating a CREB gene dosage effect. However, analysis of the platform searching strategies in the water maze task suggested that CREBcomp mutants are impaired in behavioral flexibility rather than in spatial memory. In contrast to previous experiments using CREBalphadelta mice with different genetic background, the F1 hybrid CREBalphadelta and CREBcomp mice did not show deficits in a social transmission of food preference task nor in dentate gyrus and CA1 LTP as recorded from slice preparations. These data indicate that the hybrid vigor typical for F1 hybrids may compensate for a reduction in CREB levels in some tests. On the other hand, the persistence of clear behavioral deficits as shown by the F1 hybrid CREBcomp mice in water maze and fear conditioning indicates a robust and repeatable phenomenon that will permit further functional analysis of CREB. (+info)
Galactose consumption induces conditioned flavor avoidance in rats.
(22/1652)
Recent findings revealed that intragastric infusions of galactose conditioned a flavor avoidance in adult rats. To determine whether the galactose-conditioned avoidance was due to the infusion procedure, we investigated the flavor conditioning effect of orally consumed galactose. Food-restricted rats drank a flavored galactose solution, a flavored fructose solution and a flavored saccharin solution in separate one-bottle training sessions; grape, cherry and orange flavors were used. Because fructose is sweeter than galactose, saccharin was added to the galactose solution to increase its palatability. Pre- and posttraining preferences for the galactose and fructose solutions were evaluated in two-bottle choice tests. Also, preferences for the sugar-paired flavors were evaluated in two-bottle tests with the flavors presented in saccharin. In Experiment 1, rats were trained with flavored 80 g/L fructose, 80 g/L galactose + 2 g/L saccharin, and 2 g/L saccharin solutions (20 mL/d). Their preference for the flavored galactose solution changed (P < 0.01) from 76% (pretraining) to 19% (posttraining). The rats also avoided (P < 0.05) the flavor paired with the galactose solution in choice tests with the fructose-paired flavor and the saccharin-paired flavor. Similar pre- to posttraining preference reversals were obtained in Experiments 2 and 3, which used 20 g/L galactose and fructose solutions, and 20 g/L galactose and fructose solutions mixed with 20 g/L glucose, respectively. These findings, together with the intragastric infusion data, demonstrate that galactose has aversive postingestive consequences in adult rats even at low concentrations (20 g/L). Unlike lactose intolerance, which is due to intestinal malabsorption, this galactose-induced flavor avoidance is presumably due to the slow and incomplete postabsorptive metabolism of galactose. (+info)
The influence of early experience with vanillin on food preference later in life.
(23/1652)
A study with 133 adults, who had been breast-fed or bottle-fed after birth, shows that neonatal experience with vanilla influences preferences for other foods in later life. (+info)
Variation in food selection among lambs: effects of basal diet and foods offered in a meal.
(24/1652)
In studies of behavior and nutrition, we typically determine nutritional needs and formulate diets for the average member of the herd, not for specific individuals within a herd. Nevertheless, variation among individuals could affect productivity of the group if the diet diverges too much from what individuals at the extremes prefer to eat. Thus, it is important to determine the degree to which individuals within a group vary in their food preferences when offered alternatives. Our first objective was to determine the degree to which lambs differed in preference for foods high in energy (barley) or protein (alfalfa) (Exp. 1). When we offered lambs barley and alfalfa for ad libitum consumption for 25 d, individuals varied in the amounts of barley (range: 221 to 991 g/d) and alfalfa (range: 51 to 558 g/d) they consumed (P < .0001). At one extreme, individuals preferred a diet of 6% alfalfa and 94% barley; at the other extreme, individuals preferred a diet of 70% alfalfa and 30% barley. Our second objective was to determine whether lambs from Exp. 1 compensated, when fed a basal diet that was lower in alfalfa than they preferred, by ingesting foods higher in alfalfa when offered a meal (Exp. 2). Lambs were ranked according to the percentage of alfalfa (range from 6 to 70%) and barley (range from 94 to 30%) they ate during Exp. 1 and then assigned alternately to two treatments: 1) basal diet with similar proportions of alfalfa and barley consumed ad libitum (preferred diet) or 2) basal diet with 10% less alfalfa than consumed ad libitum (low-alfalfa diet). We then conducted three trials in which lambs fed the different basal diets were offered a meal for 15 min/d for 2 d of two foods that differed in barley and alfalfa. During Trial 1, when we offered barley and alfalfa, lambs in both groups preferred barley (138 g) to alfalfa (46 g) (P < .05). During Trial 2, when the test foods (barley and alfalfa) were diluted with grape pomace (20%), lambs fed the preferred basal diet ate more barley (116 vs 64 g) and less alfalfa (48 vs 87 g) than lambs fed the low-alfalfa basal diet (P < .05). During Trial 3, when we offered a food high in barley (80% barley and 20% pomace) and a food high in alfalfa (70% alfalfa, 14% cornstarch, and 16% pomace), lambs fed the preferred basal diet ate more of the high-barley food (124 vs 73 g) and less of the high-alfalfa food (45 vs 98 g) than lambs fed the low-alfalfa basal diet (P < .05). Collectively, these results illustrate that lambs varied greatly in their preferences for foods that differ in energy (barley) and protein (alfalfa), and that when their preferred basal diet was altered, lambs compensated by ingesting food that complemented their basal diet during a daily meal. The addition of grape pomace in Trials 2 and 3 reduced the protein content of the high-barley and high-alfalfa foods such that the high-barley food was only marginally adequate to meet needs compared with the high-alfalfa food. Lambs fed the low-alfalfa basal diet compensated by eating more of the high-alfalfa food than lambs fed the preferred basal diet. (+info)