Conditioning and associative learning.
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Animals↗
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Results for “Association Learning”
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[Molecular genetics on behavioral plasticity in Caenorhabditis elegans: mechanisms for associative learning].
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Animals↗
Presenilin 1 familial Alzheimer's disease mutation leads to defective associative learning and impaired adult neurogenesis.
Alzheimer's disease is a learning and memory disorder pathologically characterized by the deposition of beta-amyloid plaques and loss of neurons and synapses in affected areas of the brain. Mutations in presenilin 1 (PS1) lead to the most aggressive form of familial Alzheimer's disease (FAD), and are associated with accelerated plaque deposition. However, since the function of PS1 is pleiotropic, we reasoned that the FAD mutations may alter multiple PS1-mediated pathways, and the combination of which may account for the early onset nature of the disease phenotype. Using the PS1M146V knockin mice in which the M146V mutation was incorporated into the endogenous mouse PS1 gene, we report here that the FAD mutation results in impaired hippocampus-dependent associative learning, as measured by a contextual fear conditioning paradigm, at 3 months of age. This is correlated with reduced adult neurogenesis in the dentate gyrus. However, short-term and long-term synaptic plasticity in both area CA1 and dentate gyrus are not affected. Our results suggest that impaired adult neurogenesis may contribute to the memory deficit associated with FAD.
Animals↗
A pharmacological analysis of an associative learning task: 5-HT(1) to 5-HT(7) receptor subtypes function on a pavlovian/instrumental autoshaped memory.
Recent studies using both invertebrates and mammals have revealed that endogenous serotonin (5-hydroxytryptamine [5-HT]) modulates plasticity processes, including learning and memory. However, little is currently known about the mechanisms, loci, or time window of the actions of 5-HT. The aim of this review is to discuss some recent results on the effects of systemic administration of selective agonists and antagonists of 5-HT on associative learning in a Pavlovian/instrumental autoshaping (P/I-A) task in rats. The results indicate that pharmacological manipulation of 5-HT1-7 receptors or 5-HT reuptake sites might modulate memory consolidation, which is consistent with the emerging notion that 5-HT plays a key role in memory formation.
Animals↗
Associative learning in premature hydranencephalic and normal twins.
A hydranencephalic infant lacking cerebral hemispheres and a normal twin were tested for associative learning. After repeated trials in which two stimuli were temporally paired, test trials were given in which the second stimulus was omitted. Cardiac orienting responses to stimulus omission indicated that learning had taken place in both infants.
Anencephaly↗
Paired associate learning: form 1 and form 2 of the Wechsler Memory Scale.
Despite its popularity as a clinical measure, the paired Associate Learning (PAL) subtest of Wechsler's Memory Scale (WMS) still remains relatively undocumented for its psychometric properties. This article reports on the performance of 500 (form 1) and 600 (form 2) general medical patients hospitalized for other than neuropsychiatric conditions across five (20-69) and six (20-79) ten-year age bands respectively. In both alternate forms of PAL, strong age effects emerged while sex differences were more marked in form 2. Temporal reliability, assessed in separate student samples, proved adequate for either form. Parallel form correlations also indicated a moderate relationship between them. When easy and hard associates were analysed as separate measures with MANOVA the two forms were found to differ. Some possible reasons for these results are explored with respect to current information processing concepts postulated to affect verbal learning performance, and their utility in helping distinguish between pseudodementia and mild Alzheimer type dementia. Separate factor analyses also showed the two equivalent forms to diverge somewhat in their structural pattern with form 1 demonstrating clear clusterings of the pairs along a continuum ranging from very easy (overlearned) and mediate (superordinate) to hard associates.
Journal Article↗
Sensitization to the psychomotor stimulant effects of amphetamine: modulation by associative learning.
The authors investigated the influence of associative pairing of contextual stimuli with amphetamine administration on the expression of psychomotor sensitization. Animals received d-amphetamine or saline in group-specific environments. Amphetamine produced robust behavioral sensitization in all environments, but when an amphetamine challenge was given in a test environment that was novel for some groups but not others, the expression of sensitization was completely context specific. An injection of saline in the amphetamine-paired environment produced a conditional response (CR), but this was quite small compared to the magnitude of the sensitized response, and sensitization remained completely context specific following extinction of the CR. Results are discussed in relation to 3 models of how context may modulate the expression of sensitization: an excitatory conditioning model, an inhibitory conditioning model, and an occasion-setting model.
Amphetamine↗
Associative learning of visual and vestibular stimuli in Lymnaea.
A conditioned withdrawal response was characterized in the pond snail Lymnaea stagnalis. Using light as the conditioned stimulus and high-speed orbital rotation as the unconditioned stimulus, experimental animals were trained with 30 paired presentations of light and orbital rotation per day for 3 days. After training, all experimental animals responded to light with a withdrawal response, the conditioned response. Control animals exposed to the same number of explicitly unpaired presentations of light and orbital rotation, light alone, or no stimulation did not respond to light. Thirty paired presentations per day for 2 days produced less than optimal acquisition of the conditioned withdrawal response. Neither 45 paired presentations per day for 2 days nor 90 paired presentations for 1 day resulted in complete acquisition of the conditioned withdrawal response. The conditioned withdrawal response observed following 30 paired presentations per day for 3 to 5 days persisted to Day 10, regardless of the number of training days. As a measure of savings, reacquisition of the conditioned response after extinction was investigated. After the conditioned withdrawal response was extinguished, only 2 to 5 paired presentations of light and orbital rotation were required for reacquisition of the conditioned response for most animals. This study further establishes Lymnaea as an animal model of basic associative learning.
Animals↗
latheo, a new gene involved in associative learning and memory in Drosophila melanogaster, identified from P element mutagenesis.
Genetic dissection of learning and memory in Drosophila has been limited by the existence of ethyl methanesulfonate (EMS)-induced mutations in only a small number of X-linked genes. To remedy this shortcoming, we have begun a P element mutagenesis to screen for autosomal mutations that disrupt associative learning and/or memory. The generation of "P-tagged" mutant alleles will expedite molecular cloning of these new genes. Here, we describe a behavior-genetic characterization of latheoP1, a recessive, hypomorphic mutation of an essential gene. latheoP1 flies perform poorly in olfactory avoidance conditioning experiments. This performance deficit could not be attributed to abnormal olfactory acuity or shock reactivity-two task-relevant "peripheral" behaviors which are used during classical conditioning. Thus, the latheoP1 mutation appears to affect learning/memory specifically. Consistent with chromosomal in situ localization of the P element insertion, deficiencies of the 49F region of the second chromosome failed to complement the behavioral effect of the latheoP1 mutation. Further complementation analyses between latheoP1 and lethal alleles, produced by excision of the latheoP1 insert or by EMS or gamma-rays, in the 49F region mapped the latheo mutation to one vital complementation group. Flies heterozygous for latheoP1 and one of two EMS lethal alleles or one lethal excision allele also show the behavioral deficits, thereby demonstrating that the behavioral and lethal phenotypes co-map to the same locus.
Animals↗
A time contraction effect of acute tail-pinch stress on the associative learning of rats.
The effect of tail-pinch stress interpolated between the saccharin conditioned stimulus (CS) and the illness-inducing unconditioned stimulus (US) during long-trace taste-aversion conditioning was examined in young- and old adult rats with a two-cylinder (saccharin versus water) test. A 2 x 2 x 4 factorial ANOVA was performed on percent-preference-for-saccharin data, with age (young, old), stress condition (stressed, non-stressed), and CS-US interval (22.5-, 45-, 90-, and 180-min) being the factors under consideration. The ANOVA yielded only significant main effects of stress condition and CS-US interval. These findings indicate that stress weakens the CS-US association as evidenced by a higher percent preference for saccharin in the stressed rats than in non-stressed rats at all CS-US intervals. A comparison of the stressed and non-stressed conditioned rats with pseudo-conditioned controls showed that the non-stressed rats formed strong aversions up to the 45-min CS-US interval whereas the stressed rats showed no conditioning beyond the 22.5 min CS-US interval, indicating that stress decreases the effective CS-US interval. Results were interpreted in terms of time-contraction and an internal biological countdown timer hypothesized to govern processes involved in associative learning over long delays.
Animals↗
The decerebrate human: associative learning.
Phasic changes in cardiac reactivity to innocuous stimuli, presented in a sensory disparity paradigm, were used to evaluate habituation and learning processes in five decerebrate subjects. Three subjects showed systematic changes over trials in the pattern of cardiac response to simple auditory or visual stimuli, indicative of habituation. In addition, tests for associative learning were given after repeated presentations of two paired stimuli. The appearance of a marked cardiac orienting response, to the unpredictable omission of the second stimulus, documented the development of a conditioned association in these same three subjects. One additional subject failed to show a consistent pattern of response to the stimuli, and another demonstrated a consistent response which was not subject to habituation. Overall, these findings support the view that learning processes are not solely the product of the cerebral hemispheres, but reflect general integrative features of the human neuraxis.
Association Learning↗
Context extinction and associative learning in Lymnaea.
Aerial respiratory behavior in the pond snail Lymnaea was operantly conditioned so that snails learned not to perform aerial respiration in a hypoxic environment. Snails were trained in either the standard context (no food odorant) or a carrot (food-odorant) context. An operant training procedure of two 45-min training sessions with a 1-h interval between the sessions followed by a third 45-min training session 18 h later was sufficient to produce associative learning and long-term memory (LTM) that persisted for at least 5 days. If, however, following the third operant training session snails received three 45-min extinction training sessions, with each extinction session separated by at least a 1-h interval, LTM was not observed when tested the following day. That is, the memory was extinguished. Extinction, however, did not occur if the context of the extinction training was different from the context of the associative training. That is, in the snails trained in the standard context, extinction did not occur if the extinction training sessions were performed in the food-odorant context and vice versa.
Animals↗
Molecular cloning of linotte in Drosophila: a novel gene that functions in adults during associative learning.
The linotte (lio) gene was identified in a screen for mutations that disrupted 3 hr memory after olfactory associative learning, without affecting the perception of odors or electroshock. The mutagenesis yielded a transposon-tagged gene disruption, which allowed rapid cloning of genomic DNA. The lio transcription unit was identified via rescue of the lio1 learning/memory defect by induced expression of a lio+ transgene in adults. The perception of odors or electroshock remained normal when the lio+ transgene was expressed in these lio1 flies. Learning/memory remained normal when the lio+ transgene was expressed in wild-type (lio+) flies. The lio gene produces only one transcript, the level of expression of which varies throughout development. Sequence analysis indicates that lio encodes a novel protein.
Amino Acid Sequence↗
Neurotrophic factors in the central nucleus of amygdala may be organized to provide substrates for associative learning.
The central nucleus of amygdala was examined to identify the ultrastructural distribution of neurotrophins responsible for the complex of neuronal signaling processes which regulate synaptic transmission and neuronal plasticity, and possibly underlie memory formation. We investigated at the electron microscopic level the cellular organization of brain-derived neurotrophic factor (BDNF) and its receptor, tyrosine kinase receptor B (TrkB), in the extended amygdala (CE). We also investigated the interaction between cortical inputs to CE and BDNF and TrkB. Our results indicate the presence of pro-BDNF and BDNF in terminals in the CE which show a strong association with immunoreactive postsynaptic densities. TrkB receptor immunoreactivity was localized to postsynaptic densities of asymmetric synapses on dendrites and dendritic spines. Cortical terminals formed asymmetric synapses with dendritic shafts and spines, but were not BDNF immunoreactive. TrkB receptors were observed opposed to cortical terminals. These data also suggest that one potential substrate for associative learning may be the interaction of different cortical inputs with neurotrophin-containing terminals ending on dendritic spines and other neuronal structures of CE.
Amygdala↗
Using a paired-associate learning task to assess parent-child phenotypic similarity.
The fact of uncertain paternity has led some researchers to hypothesize that children should more closely resemble their fathers than their mothers. The evidence in support of this hypothesis is mixed, partly because the procedures used to measure perceived phenotypic similarity may not be sensitive enough to detect small effects and partly because comparisons are made between fathers and mothers rather than random control groups. In the present experiment the viability of using a paired-associate learning paradigm to investigate parent-child phenotypic similarity is demonstrated using 15 stimulus sets of colored photographs picturing two adults and one child. Using a 2 x 2 between subjects analysis of variance for total errors across learning trials, evidence indicated genetic relatedness for both mothers and fathers influences perceived resemblance and that association of male facial features with those of children, whether paternal or not, are learned more quickly than female facial features. While the significance of genetic relatedness to facial similarity was expected, the overall sex difference was not. However, the additive combination of these variables, genetic relatedness and maleness may explain why children seem to more closely resemble their fathers.
Adolescent↗
Post-ingestive feedbacks and associative learning regulate the intake of unsuitable sterols in a generalist grasshopper.
Behavioural studies of the grasshopper Schistocerca americana were undertaken to identify the mechanisms that regulate the intake of dietary sterols. In the first experiment, grasshoppers were allowed to feed on spinach, a plant containing only unsuitable sterols; immediately after this first meal, a suitable or unsuitable sterol was injected into the haemolymph. Grasshoppers injected with unsuitable sterols had second meals on spinach that were significantly shorter than those of grasshoppers injected with suitable sterols, indicating that unsuitable dietary sterols are detected post-ingestively. In the second experiment, grasshoppers were fed food containing only unsuitable sterols and were then presented with glass-fibre discs containing different concentrations of a suitable sterol or sucrose only (the control). The results suggest that grasshoppers do not use a direct feedback operating on mouthpart chemoreceptors to regulate their intake of suitable sterols. In the third experiment, grasshoppers were presented with artificial diets containing different sterols and flavours, and feeding was observed over a sequence of meals. The results from both the first and last experiments suggest a role for associative learning in regulating the intake of unsuitable sterols.
Animals↗
Evolution of cerebral cortex involvement in the acquisition of associative learning.
The presence of the c-Fos protein has been evidenced in the piriform cortex, subiculum, entorhinal and perirhinal cortices, and parietal and occipital cortices at different stages (Sessions 2, 4, and 6) in the acquisition of a trace conditioning in behaving rabbits. c-Fos immunostaining was also measured after a reminder (7th) session. c-Fos immunoreactivity increased significantly across conditioning on the contralateral side of the piriform, entorhinal, perirhinal, and parietal cortices as compared with the ipsilateral side of conditioned animals and the contralateral side of pseudo-conditioned ones. No difference in c-Fos immunostaining was observed between contra- and ipsilateral sides in the subiculum of conditioned animals. c-Fos production decreased significantly across conditioning but presented a noticeable bilateral increase after the reminder session in the piriform, entorhinal, perirhinal, and parietal cortices, but not in the subiculum. Peak production of c-Fos was observed after the 2nd and 7th (reminder) conditioning sessions for the piriform, entorhinal, perirhinal, and parietal cortices, and after the 4th session for the subiculum. It is proposed that different cortical areas process associative learning with different strengths and side dominances.
Animals↗
Associative learning and memory in Lymnaea stagnalis: how well do they remember?
The search for 'the how and the where' of memory formation in the brain, the engram, is still one of the unattained 'Holy Grails' of neuroscience. Over the years, various paths have been trodden in attempts to attain this goal, and while tantalizing glimpses appear now and then on the scientific horizon, the Grail still has not been grasped. One of the paths that investigators have walked is the invertebrate 'model system' approach. Some invertebrates possess relatively simple nervous systems that mediate relatively simple behaviours that are both interesting and trainable. In this commentary, we would like to shed light on a relatively new player, the pond snail Lymnaea stagnalis L., that is being used in the quest to illuminate 'the how and the where' the nervous systems encode and store memory. We will show that it is possible to demonstrate that a single neuron is a site of memory formation and storage for a form of associative learning in this lowly snail. It may be that the Grail is a little closer to being grasped.
Animals↗