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Spatial learning, discrimination learning, paw preference and neocortical ectopias in two autoimmune strains of mice.

NZB and BXSB mice were given a battery of behavioral tests including paw preference, water escape, Lashley III maze, and discrimination learning. Their brains were then evaluated for cortical ectopias. The incidence of ectopias was 40.5% in NZBs and 48.5% in BXSBs. In the NZB strain left-pawed ectopic mice (both male and female) had the fastest swimming time in the water escape test, while right-pawed ectopics were the slowest. The same findings were obtained for left- and right-pawed ectopic BXSB males, but not for the females. However, on discrimination learning the BXSB males had the exact opposite pattern: right-pawed ectopics were the best learners while left-pawed ectopics were the worst. Male BXSBs and both male and female NZBs were manifesting autoimmune disease at the time of testing, while female BXSBs were not, suggesting that autoimmunity is a necessary background condition for the differential expression of ectopias and paw preference upon learning processes. The finding that the left-pawed ectopic BXSB mice, who were the poorest learners in the non-spatial discrimination learning test, learned best in the spatial water escape test is in agreement with the Geschwind hypothesis that pathological events during brain development may, in some instances, produce superiority of function.

Animals

Drug effects on sucessive discrimination learning in young chickens.

Chicks were trained to avoid pecking either a red or a blue bead in a one-trial avoidance task by coating one bead with methy anthranilate. They avoided the aversant bead on retention tests 10 to 180 min or 24 hr after learning, but not the neutral bead. Intracranial administration of ouabain or cycloheximide (CXM) 5 min before learning resulted in decay in retention after 10 and 30 min respectively following learning, discrimination being effective prior to those times. In a second experiment, chicks were trained on three physically distinct beads, two of which were made aversive during the learning period, the training trials separated by an hour. Saline-treated chickens retained memory of both aversive beads on retention trials 180 min later. CXM- and ouabain-treated chickens showed loss of memory for the bead associated with the drug but showed retention of the task which was not associated with the drug.

Animals

Amygdalectomy and ventromedial prefrontal ablation produce similar deficits in food choice and in simple object discrimination learning for an unseen reward.

Cynomolgus monkeys (Macaca fascicularis) with either bilateral amygdalectomy or bilateral ventromedial prefrontal cortical ablations showed abnormal choices between apple, lemon, olive, and meat. Not only did they choose meat or olive more often than normal animals, but also their choices were less consistent from trial to trial than the normal animals' choices were. The same animals were subsequently tested for their ability to learn 2-choice simultaneous visual discriminations between objects which they could suck. The positive object yielded fruit juice, which entered the mouth directly without being seen. Both groups of animals with lesions were severely impaired in this discrimination learning task. The reason why amygdalectomy has little effect on simple object discrimination learning in the Wisconsin General Test Apparatus, we suggest, is that the animal can there associate the visual discriminanda with the visual properties of the food reward, a mechanism which is not available when the reward is unseen. These results add to existing evidence of a close functional relationship between the amygdala and the ventromedial prefrontal cortex, and they support the proposal, derived from previous work, that the amygdala is important for associating visual stimuli with the incentive value of reinforcers.

Amygdala

Conditioned taste aversions support drug discrimination learning at low dosages of morphine.

The present experiment shows that a conditioned taste aversion procedure can support discrimination learning at dosages of morphine comparable to those required to produce motivational effects. Sprague-Dawley rats were injected with 4.0 mg/kg morphine sulfate prior to a saccharin-lithium chloride pairing, and physiological saline prior to a saccharin-saline pairing. The rats avoided the saccharin solution following the administration of morphine and consumed significantly more saccharin following saline administration after four discrimination cycles. After this initial discrimination the subjects were trained with progressively lower doses of morphine. Discrimination learning was apparent at doses of 2.0, 1.5, 1.0, 0.75 and 0.5 mg/kg. Animals initially trained with 1.0 mg/kg morphine also learned the discrimination but required 10 training cycles. After this initial discrimination the subjects were trained with progressively lower dosages of morphine and showed a discrimination at a dosage of 0.5 mg/kg.

Animals

Effect of intraventricular gamma-aminobutyric acid (GABA) on discrimination learning in rats.

Rats were trained to perform light-dark discrimination learning for a period of 6 consecutive days. GABA, an inhibitory transmitter, was administered into the lateral ventricle either immediately or 60 min after the completion of each training session. GABA, in dose levels of 100 and 150 microgram and injected immediately after the completion of the session, significantly increased correct responses in comparison with the corresponding control group, while 200 microgram of the drug had no further effect on the correct responses. When the administration of the drug was delayed by 60 min, neither 100 nor 150 microgram of GABA significantly increased correct response. Intraventricular GABA did not affect total activity or water intake which could be considered indexes corresponding to motility and motivational state, respectively. It was concluded that under these conditions GABA improves discrimination learning by its action as an inhibitory transmitter.

Aminobutyrates

The effect of change in stimuli on the transfer of dimensional pretraining to the discrimination learning of kindergarten children.

Kindergarten children were given verbal pretaining prior to a simultaneous discrimination learning task under 1 or 2 stimulus conditions. For half the children, the stimuli were changed from the pretaining task to the criterion task; for the other half, the stimuli were identical in the 2 tasks. During pretaining, the children learned to label the values of the dimension that would be either relevant, constant, or irrelevant in discrimination learning. When the stimuli were identical in 2 tasks, pretaining produced significant facilitation and interference effects in discrimination performance. The pretaining effects in the changed-stimulus condition were greatly attenuated and nonsignificant. The relation of these results to earlier findings and to studies of dimensional attention in general is discussed.

Child

Diprenorphine as a stimulus in drug discrimination learning.

Using the conditioned taste aversion baseline of drug discrimination learning, animals were trained to discriminate diprenorphine from distilled water. In subsequent generalization tests, the opiate antagonists naltrexone and naloxone and the mixed opiate agonist/antagonist nalorphine substituted for the diprenorphine stimulus in a dose-dependent manner, while the opiate agonist morphine and the nonopiate pentobarbital failed to substitute even at the highest doses tested. That a range of opiate antagonists substituted for the diprenorphine stimulus (and an opiate agonist and a nonopiate failed to substitute) suggest that diprenorphine's antagonist properties may mediate the discrimination, presumably by blocking endogenous opiate activity. The ability of these drugs to substitute for the diprenorphine stimulus may also be a function of this receptor activity. The differences in the specific generalization patterns reported in the present assessment and those of earlier reports were discussed.

Animals

Technique for assessing visual discrimination learning in mice.

An automated technique for the study of visual discrimination learning in mice has been developed. The technique utilizes a nose-poke as the operant response. The nose-poke response requires no shaping, has a relatively high operant level and can be used to measure preacquisition exploratory behavior. CD-1 mice acquired a simultaneous brightness discrimination readily but a successive brightness discrimination proved more difficult. A 20 sec intertrial interval was optimal for acquisition of the simultaneous discrimination. Reversal learning was slow. This procedure should prove useful in the study of the effects of pharmacologic and toxic agents on learning and performance in both weanlings and adult mice.

Animals

Attentional aspects of classroom behavior and discrimination learning.

Teachers' ratings of their mentally handicapped pupils' classroom behavior were examined as correlates of the child's performance on a discrimination learning task. Teachers completed the 23-item version of the Attention/Distraction Inhibition/Excitation Classroom Assessment Scale (ADIECAS) for a total of 77 pupils. Factors identified as attention/distractibility and responsivity to consequences correlated significantly with number of errors and number of trials to criterion during acquisition of a simultaneous visual discrimination. Attention/distractibility scores also correlated significantly with number of dimensions "attended to" during discrimination learning.

Adolescent

Genetic analysis of water maze discrimination learning for Mus musculus: polygenes and albinism.

Recombinant inbred strains, their progenitor strains and reciprocal F1 hybrids were given thirty spatial discrimination learning trials in the water maze. The pattern of RI strains in relation to the reciprocal F1 hybrids and the progenitor strains, and differences among strains, suggested that different sets of genes affect the various components of water maze discrimination learning. There was no evidence that the albino gene influenced either inferior or superior performance. Pigmented strains performed as well as, or better than, some albino strains, and albino strain BALB/cBy differed significantly from albino strains CXBG and CXBI. The two reciprocal F1 hybrids differed from blocks 2 and 3 of discrimination trials when swimming time was used a dependent variable. Thus, it appears that performance of the F1 hybrids was influenced by paternal effects, maternal effects, or paternal maternal interactions.

Albinism

Differences in the effects of post-trial chlorpromazine, reserpine, and amphetamine on discrimination learning in rats.

Rats were trained to perform in discrimination learning reinforced by water for 6 days, and were intraperitoneally injected with chlorpromazine, reserpine, or d-amphetamine after each training session. Although chlorpromazine at the dose levels of 0.5 mg/kg or more injected immediately after training impaired learning, the drug did not affect learning when it was injected 60 min after training. Reserpine and amphetamine also impaired learning, but delaying the time intervals between training and injection to 60 min or more had no influence on this learning impairment. Post-trial chlorpromazine and amphetamine had no effect on, but reserpine decreased, motility in the subsequent training session. Chlorpromazine had no effect on water intake in the subsequent session, but reserpine and amphetamine decreased water intake at the dose levels that impaired learning. It was concluded that all three drugs impaired learning, but differed in their effects on learning; chlorpromazine impaired learning by a specific effect on learning itself; reserpine, by a non-specific effect on behavior due to a long acting sedation; and amphetamine, by an effect to decrease the motivation to drink water. The specific effect of chlorpromazine could be related to the hypothesis of "memory trace" synthesis.

Animals

Visual discrimination learning in cats with different early visual experiences.

Simultaneous object discrimination learning in an alimentary situation was strongly impaired in cats deprived from birth of patterned visual experience. The same impairment was observed in cats with experience limited to those objects that were used later in the discrimination task. Some impairment was also present in cats which were reared with opened eyes in the laboratory as compared with normal cats, that spent the early period of life outside of the laboratory. It is concluded that the deprived cats were impaired mainly because of the lack of opportunity during early development to use visual cues in alimentary tasks.

Animals

Theoretical and methodological considerations on drug discrimination learning.

A method is described which allows the assessment of discriminative stimulus properties of drugs, and the ability of amphetamine (0.16 mg/kg s.c.), chlordiazepoxide (5 mg/kg p.o.), desipramine (5 mg/kg s.c.), and haloperidol (0.02 mg/kg s.c.) to produce a discriminative stimulus complex (DSC) is evidenced. The method is found to yield clear-cut data that are specifically related to drug discrimination learning without being possibly confounded by state dependent effects. In addition, the experimental procedure is designed so as to provide an appropriate measurement of operant response modulating drug effects.

Amphetamine

Discrimination learning without short-term memory: dissociation of memory processes in pigeons.

Pigeons were trained to perform delayed matching to samples of food and no food when each sample concurrently served as the outcome of a discrimination learning trial which immediately preceded each matching trial. Ambient light presented during the delays after the samples of food or no food severely disrupted matching but had no effect on the rate of discrimination learning.

Animals

Prehatch color stimulation effects on color pecking preferences and color discrimination learning in white leghorn chicks.

Four experiments assessed the effects of stimulating chick embryos with colored light at 2 intensity levels. Both posthatch color pecking preferences (Experiments 1 and 2) and color discrimination learning (Experiments 3 and 4) were unaffected. These results affirm and extend a prior finding of no pre- and posthatch colored light stimulation effect on posthatch color preferences in ducklings. The color pecking preferences found replicated prior findings with chicks. However, they differed from the approach color preferences observed in color discrimination learning.

Animals

Changes in pattern discrimination learning induced by visual deprivation in normal and commissurotomized pigeons.

The effect of monocular (MD), binocular (BD) and alternating monocular (AMD) deprivation on monocular pattern discrimination learning and interocular transfer was investigated in pigeons reared with intact and sectioned supraoptic decussation (DSO). In BD and AMD animals acquisition and interocular transfer of two different pattern discrimination problems remained as good as in the control animals (CO). Monocularly deprived animals (MDE) required significantly more trials to learn the discriminations through the deprived eye, when it was trained first, and interocular transfer from the deprived to the experienced eye was absent. However, if the experienced eye was trained first (MED), learning with the deprived eye was at least as rapid as with the experienced eye. This indicates positive interocular transfer from the experienced to the deprived eye. Interocular transfer of pattern discriminations was completely blocked by section of the DSO in both adults (DSOad) and newly hatched animals (DSOjuv). The elimination of binocular interaction by commissurotomy from the beginning of the postnatal life failed to produce an impaired pattern discrimination learning in monocularly deprived animals.(MD+DSO). The results are discussed in terms of competition between the projections from both eyes in the visual Wulst.

Animals

Naloxone as a stimulus in drug discrimination learning: generalization to other opiate antagonists.

Nonopiate dependent animals were trained to discriminate the opiate antagonist naloxone (1 mg/kg) from distilled water within the conditioned taste aversion baseline of drug discrimination learning. Specifically, rats injected with naloxone prior to a saccharin-LiCl pairing, and with its vehicle prior to saccharin alone, rapidly acquired the drug discrimination, avoiding saccharin following the administration of naloxone and consuming saccharin following its vehicle after only three conditioning trials. Once the discrimination was acquired, generalization tests revealed that the opiate antagonists diprenorphine and naltrexone and the mixed opiate agonist/antagonist nalorphine completely generalized to the naloxone cue at doses of 1.8, 5.6 and 18 mg/kg, respectively. That discriminative control was established with a low dose of naloxone (i.e., 1 mg/kg) and other compounds with opiate antagonist activity generalized to the naloxone cue suggest that the stimulus effects of naloxone were likely mediated through the opiate receptor. Because each of these compounds are reported to bind to the mu receptor (with varying affinities and varying degrees of selectivity), the stimulus properties of naloxone are likely mediated at this specific receptor subtype.

Animals