The strategy of tail-autotomy in the ground skink, Lygosoma laterale.
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Results for “Appetitive Behavior”
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Naltrexone, opiate addiction, and endorphins.
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Animals↗
Eating and the American Zeitgeist.
This article traces the development of the science of eating in the United States from the experiment of Cannon and Washburn in 1912 until the founding of the Appetitive Seminar at Columbia in 1972. The interplay between the intrinsic aspects of science that depend on the sequence of ideas, techniques, and results, and the extrinsic influences of the Zeitgeist is emphasized.
Animals↗
The laboratory preference of annual legumes by pea weevil sitona lineatus L. (Col., curculionidae) and their effect on susceptibility of weevils to entomogenous nematodes.
The activity and natural mortality of Sitona lineatus weevils during the egg laying period may be connected with host plant preference. Preference of S. lineatus adults for early field pea and other pea cultivars influences their low feeding activity and results in lopff average body weight and higher susceptibility to entomogenous nematodes, Steinernema carpocapsae, S. feltiae, and Heterorhabditis bacteriophora.
Animals↗
Mathematical modelling of host-parasitoid systems: effects of chemically mediated parasitoid foraging strategies on within- and between-generation spatio-temporal dynamics.
In this paper we develop a novel discrete, individual-based mathematical model to investigate the effect of parasitoid foraging strategies on the spatial and temporal dynamics of host-parasitoid systems. The model is used to compare naïve or random search strategies with search strategies that depend on experience and sensitivity to semiochemicals in the environment. It focuses on simple mechanistic interactions between individual hosts, parasitoids, and an underlying field of a volatile semiochemical (emitted by the hosts during feeding) which acts as a chemoattractant for the parasitoids. The model addresses movement at different spatial scales, where scale of movement also depends on the internal state of an individual. Individual interactions between hosts and parasitoids are modelled at a discrete (micro-scale) level using probabilistic rules. The resulting within-generation dynamics produced by these interactions are then used to generate the population levels for successive generations. The model simulations examine the effect of various key parameters of the model on (i) the spatio-temporal patterns of hosts and parasitoids within generations; (ii) the population levels of the hosts and parasitoids between generations. Key results of the model simulations show that the following model parameters have an important effect on either the development of patchiness within generations or the stability/instability of the population levels between generations: (i) the rate of diffusion of the kairomones; (ii) the specific search strategy adopted by the parasitoids; (iii) the rate of host increase between successive generations. Finally, evolutionary aspects concerning competition between several parasitoid subpopulations adopting different search strategies are also examined.
Animals↗
Memory for magnitude of reinforcement: dissociation between the amygdala and hippocampus.
Rats were trained on a successive delayed conditional discrimination task measuring memory for magnitude of reinforcement. In the study phase of the task, the rats were given one of two cereals. One cereal contained 25% sugar; the other 50% sugar. One of the two cereals was always designated the positive stimulus and the other the negative stimulus. This study phase was followed by the test phase in which the rat was shown an object which covered a food well. If the rat was given the negative stimulus in the study phase of the trial, no food reward was placed beneath the object. Whenever the positive stimulus was presented a food reward was available beneath the object. Performance was measured as the latency to uncover the food well. After reaching criterion level, the rats were given amygdala, hippocampal, or control lesions. Amygdala-lesioned rats showed significant deficits in performance, whereas no long-term deficits were observed for the hippocampal-lesioned groups even at longer retention delays. In additional experiments, it was shown that amygdala-lesioned, like normal, rats had similar taste preferences. Finally, normal and hippocampal-, but not amygdala-, lesioned rats transferred readily to different cereals containing 25% or 50% sugar. Thus, it appears that the amygdala, but not the hippocampus, plays a significant role in explicit data-based or working memory for affect information based on magnitude of reinforcement.
Affect↗
Quinacrine acts like an acetylcholine receptor antagonist rather than like a phospholipase A2 inhibitor in a passive avoidance task in the chick.
Quinacrine (QU) is an inhibitor of phospholipase A2 (PLA2). However, QU has antagonistic properties at the acetylcholine receptor as well. To investigate if PLA2 activity is of importance in memory formation, QU was tested in a passive avoidance task in the chick. Injecting QU pretraining caused amnestic effects 45 min post-training. When comparing this result with results obtained with other PLA2 inhibitors, it became apparent that QU is not acting primarily as an inhibitor of PLA2. Scopolamine, an acetylcholine receptor antagonist, was tested and produced the same onset of amnesia as QU. I conclude that QU is acting functionally as an antagonist of acetylcholine receptors rather than of PLA2.
Animals↗
Beta-amyloid accumulation correlates with cognitive dysfunction in the aged canine.
It is well known that beta-amyloid accumulates abnormally in Alzheimer's disease; however, beta-amyloid's relationship to cognitive dysfunction has not been clearly established and is often confounded by the presence of neurofibrillary tangles. We used canines to investigate the relationship between beta-amyloid accumulation and cognitive function in an animal model of aging lacking neurofibrillary tangles. The performance of 20 canines (11 purebred beagles and 9 mongrels) on a battery of six cognitive tasks was measured. These tasks included Reward Approach and Object Approach learning, as well as Discrimination, Reversal, Object Recognition, and Spatial learning and memory. Aged canines were impaired on some tasks but not others. beta-Amyloid-immunopositive plaques were found in many of the older animals. Plaques were all of the diffuse subtype and many contained intact neurons detected with double-labeling for neurofilaments. No neurofibrillary tangles were detected. beta-Amyloid was also associated with the processes of many neurons and with blood vessels. Using computerized image analysis, we quantified the area occupied by beta-amyloid in entorhinal cortex, frontal cortex, and cerebellum. Controlling for age-related increases in beta-amyloid, we observed that increased beta-amyloid deposition is strongly associated with deficits on Discrimination learning (r = .80), Reversal learning (r = .65), and Spatial learning (r = .54) but not the other tasks. There were a few differences between breeds which are discussed in the text. Overall, these data suggest that beta-amyloid deposition may be a contributing factor to age-related cognitive dysfunction prior to the onset of neurofibrillary tangle formation.
Alzheimer Disease↗
Lesions in the dentate hilum and CA2/CA3 regions of the rat hippocampus produce cognitive deficits that correlate with site-specific glial activation.
Thirty male rats pressed a lever three times (FR3) when a stimulus light (sD) was off to obtain sucrose pellets. They were then evenly divided into sham Controls versus groups lesioned bilaterally in the hippocampus by stercotaxic injection of ibotenic acid into the dentate hilum (HIL) or the CA2/CA3 region (CA2/3). On measures of recall of the FR3-sD task taken during the initial 30 min of a postlesion test session, the CA2/3 and especially the HIL groups showed significant (p < .05) impairments relative to the Controls. During an ensuing 30-min period, rats were reshaped to criterion, beginning at FR1, and no appreciable intergroup differences were noted on this schedule or at FR1-sD. At FR2-sD, the HIL but not the CA2/3 group showed some impairment relative to Controls. At FR3-sD, both the CA2/3 and HIL groups had impaired task performance. An immunocytochemical index of glial activation showed higher reactivity in CA2/3 or the dentate hilum among CA2/3 or HIL animals, respectively, that was associated with the degree to which they showed an FR3-sD performance deficit.
Animals↗
Olfactory cues potentiate learning of distant visuospatial information.
The influence of proximal olfactory cues on place learning and memory was tested in two different spatial tasks. Rats were trained to find a hole leading to their home cage or a single food source in an array of petri dishes. The two apparatuses differed both by the type of reinforcement (return to the home cage or food reward) and the local characteristics of the goal (masked holes or salient dishes). In both cases, the goal was in a fixed location relative to distant visual landmarks and could be marked by a local olfactory cue. Thus, the position of the goal was defined by two sets of redundant cues, each of which was sufficient to allow the discrimination of the goal location. These experiments were conducted with two strains of hooded rats (Long-Evans and PVG), which show different speeds of acquisition in place learning tasks. They revealed that the presence of an olfactory cue marking the goal facilitated learning of its location and that the facilitation persisted after the removal of the cue. Thus, the proximal olfactory cue appeared to potentiate learning and memory of the goal location relative to distant environmental cues. This facilitating effect was only detected when the expression of spatial memory was not already optimal, i.e., during the early phase of acquisition. It was not limited to a particular strain.
Animals↗
Spatial working memory and reference memory of Brown Norway and WAG rats in a holeboard discrimination task.
To determine whether working memory (WM) and reference memory (RM) represent different aspects of spatial memory, albino WAG rats and the pigmented Brown Norway rats were tested in the acquisition, retention, and reversal of spatial orientation tasks in the holeboard, which allows the simultaneous assessment of WM and RM. Putative nonmnemonic factors, such as the speed of visiting the holes or the development of a search strategy (preferred sequence of visiting the baited set of holes) were also evaluated because they might influence WM and RM performance. The WM performance of Brown Norway rats was generally worse than that of the WAG rats. The reverse was true for the RM performance. Correlation analysis supported the notion that these two measures are independent. Differences in the speed of visiting the holes and in the development of a preferred sequence of visiting the baited set of holes could not explain the strain differences in WM and RM performance. Because spatial WM and RM appear to be independent measures in the holeboard, this task could be used to investigate whether different neural substrate(s) underlie these two memory components.
Animals↗
Pavlovian heart rate and jaw movement conditioning in the rabbit: effects of medial prefrontal lesions.
An experiment was conducted in which jaw movements (JM) and heart rate (HR) were concomitantly assessed in rabbits during simple Pavlovian conditioning. A 2-s 1200-Hz tone was the conditioned stimulus (CS) and an intraoral 1-cc pulse of 0.5 M sucrose-water solution was the unconditioned stimulus (US). Sham and medial prefrontal (mPFC)-lesioned animals received paired CS/US training with a 70- to 75-dB CS and were compared with sham- and mPFC-lesioned animals that received explicitly unpaired CS/US presentations. The percentages of JM CRs were significantly greater in the paired than the unpaired groups, but mPFC lesions had no effect on this measure. Conditioned HR decelerations occurred only in the paired groups and then only during the first session of training. Moreover, these CS-evoked cardiac decelerations were somewhat attenuated by the mPFC lesion. CS-evoked HR accelerations, which were significantly greater in unpaired than in paired animals, occurred during the four subsequent sessions. These results suggest that a CS-evoked cardioinhibitory process, mediated by the mPFC, is engendered by Pavlovian appetitive conditioning, as has been previously demonstrated for aversive conditioning. However, during JM conditioning these inhibitory changes are quickly replaced by tachycardia, possibly related to increased nonspecific somatomotor activity, since the tachycardia was somewhat greater in the unpaired animals.
Animals↗
Honeybee memory: navigation by associative grouping and recall of visual stimuli.
Studies of navigation in bees and ants are beginning to reveal that foraging insects traveling repeatedly to a food source navigate by using a series of visual images of the environment acquired en route (Collett, 1996; Collett et al., 1993; Judd & Collett, 1998; Wehner et al., 1990, 1996). By comparing the currently viewed scene with the appropriate stored image, the insect is able to ascertain whether or not it is on the correct path and make any necessary corrections. If a bee happens to forage at more than one site, then she needs not only to memorize a separate set of images for each route that she has learned but also to retrieve the set of images that is appropriate to each route. Here we examine the bee's capacity to learn and later retrieve from memory two different sets of visual stimuli. Bees were trained to fly through a compound Y-maze where they were presented alternately with two different sequences of visual stimuli on their route to a food reward. We find that bees can indeed store two different sequences of images simultaneously. Furthermore, the trained bees are able to classify the memorized images into two groups, one pertaining to each three-stimulus set. Exposure to any of the images pertaining to one set triggers recall of all of the other images associated with that set. Associative grouping and recall of visual stimuli, demonstrated here for the first time in honeybees, provide an effective means of retrieving the appropriate navigational information from memory.
Animals↗
Appetitive learning using visual conditioned stimuli in the pond snail, lymnaea.
Feeding can be conditioned in the pond snail Lymnaea stagnalis to two different visual stimuli (a black panel or a 5-mm black and white check surround) by pairing the potential conditioned stimulus (CS) with sucrose. Exclusion of chemical cues (associated with differences between the water in home tank and that in training apparatus) that could serve as CS is important for successful visual conditioning. A featureless gray surround, used as an alternative to the check (to which it was matched in luminance) in counterbalanced training designs, was discriminated from the check, showing that resolution (for which the eyes would be necessary) was occurring. The gray surround was largely ineffective as a CS. Single-trial learning was possible with the black panel, but not with the check; it is argued that this may be due to lack of prior experience of stimuli like the check. Conditioning of feeding has now been obtained in Lymnaea to chemical, tactile, and visual cues, opening the way to comparative studies of the neural circuitry underlying appetitive conditioning in different senses, so far explored in Lymnaea only for tactile CS. Such comparative studies are as yet largely lacking in invertebrates.
Animals↗
Noradrenergic receptor blockade of the NTS attenuates the mnemonic effects of epinephrine in an appetitive light-dark discrimination learning task.
These experiments examined the contribution of noradrenergic neurons in the nucleus of the solitary tract (NTS) in mediating the memory-facilitating effects of epinephrine. In Experiment 1, saline or 0.05 or 0.1 mg/kg of epinephrine was given intraperitoneally (ip) to rats after the second day of training in a light-dark Y-maze discrimination task. On a 20-trial retention test given 2 and 7 days later, the 0.1 mg/kg epinephrine group made significantly more correct responses than controls and required fewer trials to reach criterion. In Experiment 2, phosphate-buffered saline or the noradrenergic antagonist dl-propranolol (0.3 or 1.0 microg/0.5 microl) was infused into the NTS prior to an ip injection of saline or 0.1 mg/kg of epinephrine. The memory-enhancing effects of epinephrine were attenuated by the infusion of 0.3 microg/0.5 microl of dl-propranolol into the NTS. These findings indicate an involvement of NTS noradrenergic neurons in mediating the effects of peripheral epinephrine on memory storage processes.
Animals↗
Glucose treatment reduces memory deficits in young adult rats fed high-fat diets.
Feeding rats high-fat diets for 3 months produces a widespread cognitive deficit that affects performance on a wide range of learning and memory tasks. The present study tested the hypothesis that this effect is related to a fat-induced impairment in glucose metabolism. Following 3 months of dietary intervention (20% by weight fat diets, composed primarily of either beef tallow or soybean oil versus standard laboratory chow), male Long-Evans rats were tested on a variable interval delayed alternation (VIDA) task that measures learning and memory functions that differentially involve specific brain regions. Relative to rats fed chow, rats consuming the high-fat diets were impaired on all aspects of VIDA performance. Following baseline testing, rats were maintained on their respective diets and the effect of glucose administration (100 mg/kg BW; i.p.) was examined. For the next 6 days, animals alternately received injections of saline or glucose 30 min prior to VIDA testing. Glucose treatment improved performance, with the effect being most pronounced at the longer intertrial intervals where task performance is sensitive to hippocampal impairment. Importantly, the beneficial effect of glucose were confined to those animals consuming the high-fat diets and were not observed in rats fed chow. These results demonstrate that glucose administration can overcome those deficits associated with hippocampal function in rats fed high-fat diets and are consistent with the hypothesis that high-fat diets, in part, mediate their effect through the development of insulin resistance and glucose intolerance.
Age Factors↗
Comparability of a single-trial passive avoidance learning task in the young chick across different laboratories.
The discrepant results noted by the La Trobe/Monash, Sussex, Open, and Berkeley University memory research groups employing the passive avoidance task (PAT) with the chick indicate that some of these differences may be due to differences in training procedures between the various groups. The procedures employed by each group were replicated as closely as possible and compared using the same strain of chick. Higher levels of pecking and lower training latencies were observed in the La Trobe/Monash chicks. Improved training latency was observed following a change in the day of experimentation with Sussex chicks, and in white light in Open chicks. A powerful reinforcing effect was observed when pretraining was conducted with a wet lure across multiple pretraining trials, indicating the importance of this difference between groups. The observed impact on chick performance of these variables indicates that differences between PAT procedures may have important interactive effects with aversive learning. The results of data gathered using different procedures may only be superficially comparable, and further investigation of the effects of these variables is indicated.
Age Factors↗
Appetitive instrumental learning is impaired by inhibition of cAMP-dependent protein kinase within the nucleus accumbens.
The medium spiny neurons of the nucleus accumbens receive a unique convergence of dopaminergic and glutamatergic inputs from regions associated with motivational, cognitive, and sensory processes. Long-term forms of plasticity in the nucleus accumbens associated with such processes as appetitive learning and drug addiction may require coactivation of both dopamine D1 and glutamate N-methyl-D-aspartate (NMDA) receptors. This notion implies that an intracellular mechanism is likely to be involved in these long-term neuroadaptive processes. The present series of experiments examined the effects of intra-accumbens microinfusion of protein kinase inhibitors on acquisition of an instrumental task, lever-pressing for food. Male Sprague-Dawley rats were bilaterally implanted with chronic indwelling cannulae aimed at the nucleus accumbens core. Following recovery, animals were food-restricted and subsequently trained for operant responding. The broad-based serine/threonine kinase inhibitor H-7 (5 or 27 nmol per side) dose-dependently impaired learning when infused immediately after testing on days 1-4. Rp-cAMPS, a cAMP-dependent protein kinase (PKA) inhibitor, also impaired learning regardless of whether it was infused immediately before (5 or 20 nmol) or immediately after (10 nmol) testing on days 1-4. Rp-cAMPS (10 nmol) also inhibited learning when infused 1 h after testing, though to a lesser extent than when administered before or immediately after testing. The PKA stimulator Sp-cAMPS (5 or 20 nmol) also impaired learning when infused before testing, suggesting that there is an optimal level of PKA activity required for learning. None of the drugs used produced nonspecific motor or feeding effects. These results provide evidence supporting the involvement of nucleus accumbens PKA in appetitive learning and suggest that this kinase may be involved in long-term changes associated with this and other motivationally based neuroadaptive processes.
Animals↗