Performance on the Hebb-Williams maze as related to discrimination and reversal learning in rats.
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Animals↗
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Quantitative trait loci associated with reversal learning and latent inhibition in honeybees (Apis mellifera).
A study was conducted to identify quantitative trait loci (QTLs) that affect learning in honeybees. Two F1 supersister queens were produced from a cross between two established lines that had been selected for differences in the speed at which they reverse a learned discrimination between odors. Different families of haploid drones from two of these F1 queens were evaluated for two kinds of learning performance--reversal learning and latent inhibition--which previously showed correlated selection responses. Random amplified polymorphic DNA markers were scored from recombinant, haploid drone progeny that showed extreme manifestations of learning performance. Composite interval mapping procedures identified two QTLs for reversal learning (lrn2 and lrn3: LOD, 2.45 and 2.75, respectively) and one major QTL for latent inhibition (lrn1: LOD, 6.15). The QTL for latent inhibition did not map to either of the linkage groups that were associated with reversal learning. Identification of specific genes responsible for these kinds of QTL associations will open up new windows for better understanding of genes involved in learning and memory.
Animals↗
Rhinal cortex, but not medial thalamic, lesions cause retrograde amnesia for objects in rats.
Male Long-Evans rats were trained on five separate object discrimination problems at different times prior to surgery. Following surgery, retrograde amnesia was assessed by measuring retention of the preoperatively learned discrimination problems in lesioned rats and controls. Rats with rhinal cortex lesions displayed temporally graded retrograde amnesia; retention of object discriminations acquired in the recent past (i.e. 2 or 9 days prior to surgery) was significantly impaired, whereas retention of object discriminations acquired more remotely (i.e. 16, 37, or 58 days prior to surgery) was not. In contrast, rats with mediodorsal thalamic lesions exhibited normal savings of all discrimination problems. These results suggest that the rhinal cortex, but not the mediodorsal thalamus, plays a time-limited role in the consolidation of object memory.
Amnesia, Retrograde↗
Hippocampal function in the rat: cognitive mapping or vicarious trial and error?
The most prominent hypothesis of hippocampal function likens the hippocampus to a "cognitive map," a term used by a famous learning theorist, E. C. Tolman, to explain maze learning. The usual application of this concept of cognitive map, as it applies to the hippocampus, is to what is called spatial learning, mainly in the radial-arm maze of Olton and the Morris water maze. In a recent Hippocampus Forum, evidence for the cognitive map hypothesis was reviewed in a lead article by Nadel, followed by a series of commentaries by leading investigators of hippocampal function. This speculative commentary offers an alternative not represented in the forum--that the function of the hippocampus in spatial learning is not as a cognitive map, but that it subserves another function proposed by Tolman in his work on simple discrimination learning, vicarious trial and error, based on incipient, conflicting dispositions to approach and avoid.
Animals↗
Role of gustatory and postingestive actions of sweeteners in the generation of positive affect as evaluated by place preference conditioning.
Either an 18% sucrose or a 0.1% saccharin solution was used as reward in a conditioned place preference procedure. The respective solution was consumed immediately before the subject was confined to the non-preferred compartment of a place preference box. In this way only the affective reaction produced by the rewarding stimulus participated in place conditioning. Non-deprived rats consumed similar quantities of the two solutions, suggesting that they were equally rewarding. Yet only sucrose induced place preference. The lack of effect of saccharin may have been due to weaker positive affect or to an inability to induce an affective state that outlasted consummatory behavior. The first possibility was evaluated in the second experiment. Food-deprived rats were subjected to a discrimination learning task in a runway with plain water, sucrose or saccharin as reinforcer. Sucrose sustained running responses and produced improvement of discrimination behavior. Saccharin had a small effect at the first sessions only. It was concluded that saccharin is less rewarding than sucrose. In a final experiment, one group of rats was injected with glucose (2 g/kg) 17 min before being introduced in the non-preferred compartment of a place preference box. Another group was given the same dose of glucose just before drinking saccharin for 15 min. Immediately thereafter place conditioning was performed. Glucose alone had no effect, while a place preference was established when glucose injection was combined with saccharin drinking. These results show that the positive affect produced by sweet substances does not outlast consummatory behavior in the absence of postabsorptive actions.
Analysis of Variance↗
The effect of iron deficiency on cognitive performance in the rat.
The effects of iron deficiency anemia on cognitive performance of the rat were examined in a test of transfer learning. Young adult female rats maintained on either an iron-adequate (37 ppm) or low-iron (7 ppm) diet were behaviorally tested in a modified Skinner box. Tests involved visual, auditory, association, and discrimination learning. Circulating hemoglobin levels of anemic animals approximated 58.5 and 64.3% of well-nourished controls during the training and final test phase. Hematocrit levels of anemic animals followed a similar reduction, approximating only 67.0 and 72.1% of iron-adequate controls. No significant differences were observed in visual discrimination performance of the anemic animals when compared to their well-nourished counterparts. Deficits in the ability to transfer a learning association between visual and auditory stimuli were observed, however, in the anemic animals during the final test phase. The results of the present study are indicative that some aspect of association learning is adversely affected by concurrent iron-deficiency anemia.
Acoustic Stimulation↗
The aged mouse as a model of cognitive decline with special emphasis on studies in NMRI mice.
The use of the aged mouse as an integrated model of age-related cognitive decline is reviewed, with special emphasis on experiments covering the life span of NMRI mice, using different age-groups ranging from 3 through to 22 months. Age-related changes in the sensorimotor profile, spontaneous behaviour and performance in learning and memory tasks are considered. The data provide evidence for cognitive impairment and decreases in spontaneous activity and exploration from middle age onwards. Chronologically, this age depends on the longevity of the strain selected; in NMRI mice, middle age corresponds to 11-12 months. Complex learning tasks, such as the Morris water maze for spatial learning, appear to be the most sensitive to age-related changes, as are tests requiring prolonged retention of acquired information, for example, using passive avoidance. Cued and simple discrimination learning are only impaired in the oldest animals. Age-related changes in non-cognitive variables, including sensorimotor capacity, pain sensitivity, emotionality, or locomotor activity, do not account for the learning impairments, although deficits in visual acuity cannot be excluded in the very old animals. Detailed analysis of the individual data for middle aged and old mice, using discriminant and correlation studies highlight a marked heterogeneity between animals of any given chronological age. Furthermore, individual aged mice do not exhibit similar degrees of impairment across all the behavioural variables, showing that aging is not a uniform process. The possible relationship between age-related behavioural decline and neurochemical changes is an area as yet unexplored apart from a few isolated investigations, including a study on ChAT and AChE in NMRI mice. The studies in the NMRI mice illustrate the value of investigating the full age-range to detect an age group which shows cognitive decline dissociable from physical or emotional changes and which is representative of the population as a whole.
Aged↗
Synaptic vesicle ultrastructural changes in the rat hippocampus induced by a combination of alpha-linolenate deficiency and a learning task.
Rats fed either a safflower oil (alpha-linolenate-deficient) or a perilla oil (alpha-linolenate-sufficient) diet through two generations (F1) showed significant differences in the brightness-discrimination learning task. In this task, correct responses were lever-pressing responses, which were reinforced with dietary pellets, and incorrect responses were those with no reinforcement. The inferior learning performance in the safflower oil group was caused mainly by the inferior ability to rectify the incorrect responses through the learning sessions. In the safflower oil group after the learning task, the average densities of synaptic vesicles in the terminals of the hippocampus CA1 region were decreased by nearly 30% as compared with those in the perilla oil group, and it is notable that this difference was not detected without the learning task. These results suggest that dietary oil-induced morphological changes in synapses in the hippocampus of rats are related to the differential learning performance and that the turnover rate of synaptic vesicles in the hippocampus may be an important factor affecting learning performance.
Animals↗
Blood ethanol concentration from early postnatal exposure: effects on memory-based learning and hippocampal neuroanatomy in infant and adult rats.
Early postnatal exposure to ethanol (EtOH) that results in daily high-peak blood ethanol concentration (BEC) retarded the acquisition of single-patterned alteration (PA), a kind of memory-based discrimination learning, and was related to reduced brain weight, hippocampal cell number, and CA1 area in infant rats. These behavioral and neuroanatomical effects survived into young adulthood. On the PA discrimination, in both pups and young adults, postnatal exposure to high-peak EtOH condition, in relation to low-peak and control conditions, impaired the acquisition of PA at 60-s but not at 30-s intertrial intervals. These results provide further evidence of hippocampal involvement in intermediate-term memory and indicate that early postnatal EtOH is a behavioral and neuroanatomical teratogen, particularly when the BEC is relatively high.
Alcohol Drinking↗
Acute exposure to power-frequency magnetic fields has no effect on the acquisition of a spatial learning task by adult male mice.
A series of four experiments was performed to determine whether acute exposure to a range of 50 Hz magnetic fields had any effect on a learning task in adult male CD1 mice. A radial-arm maze placed within the bore of an electromagnet was used to assess spatial discrimination learning for food reward. Subjects were reduced to 85% of their free-feeding weight and were placed in the maze for up to 15 minutes each day for 10 days. Performance of the task was measured by using maximum likelihood techniques to calculate the probability that an animal would not reenter any given arm of the maze. Experimental subjects were exposed to a vertical, 50 Hz sinusoidal magnetic field at 5 microT, 50 microT, 0.5 mT, or 5.0 mT (rms). Control subjects were exposed only to a background time-varying field of less than 50 nT and the ambient static field of about 40 microT. The variation in the applied magnetic field was less than 5% except at the ends of the arms, where it approached 10%. It was found that all eight groups of subjects (n = 10 in all cases) showed similar increases in performance with testing, and the acquisition curve for each group of experimental subjects was not significantly different from that of their control group (P > 0.05 in all cases). It was concluded that exposure had no effect on learning at any flux density. This result is contrary to the findings of a number of preliminary studies, although other studies have reported that magnetic fields do not affect spatial learning in adult male rodents. It is possible that differences between experimental conditions might explain some of this apparent discrepancy.
Animals↗
The effects of the anti-cancer drugs, methotrexate and 5-fluorouracil, on cognitive function in mice.
There is evidence that standard-dose chemotherapy may impact cognitive function in cancer patients. The present study evaluated the effects of a combination of two anti-cancer drugs, methotrexate (37.5 mg/kg) and 5-fluorouracil (5FU, 75 mg/kg) on cognitive function in a mouse model. Drug-induced deficits were observed in adult BALB/C mice on tests of spatial memory, non-matching-to-sample (NMTS) learning and in a delayed-NMTS test of non-spatial memory. There were no group differences on tests of cued memory or discrimination learning. Performance-related variables were ruled out as possible explanations of the observed impairments. The impaired performance of the drug group, which was consistent with cognitive deficits observed in human cancer patients treated with similar types of chemotherapy, was attributed to functional changes in specific brain regions, including the frontal lobes and hippocampus.
Animals↗
A study of discrimination and perceptual learning with retarded readers.
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Child↗
Role of collateral behavior in temporal discrimination performance and learning in rats.
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Animals↗
Rigidity as a function of absolute and relational shifts in the learning of successive discriminations.
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Learning↗
Rigidity as a function of reversal and non-reversal shifts in the learning of successive discriminations.
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Learning↗
The role of learned irrelevance in attentional set-shifting impairments in Parkinson's disease.
In this study, the cognitive and neurochemical factors underlying learned irrelevance, one of the mechanisms thought to be responsible for attentional set-shifting deficits in Parkinson's disease (PD), were investigated. In a visual discrimination learning task, the extent to which a target dimension was irrelevant prior to an extra-dimensional shift was varied. Twenty patients with PD and 22 healthy participants performed the task twice, with patients tested on and off L-dopa. The patients made more errors than control participants in the condition in which the target dimension was completely irrelevant prior to the extradimensional shift, but not when it was partially reinforced. Moreover, L-dopa had no effect on the patients' task performance, despite improving their working memory. These results confirm that learned irrelevance is a significant factor in accounting for attentional set-shifting deficits in patients with PD, although unlike other executive impairments in this group, the phenomenon appears to be unrelated to their central dopaminergic deficit.
Adult↗
Perceptual attentional set-shifting is impaired in rats with neurotoxic lesions of posterior parietal cortex.
The posterior parietal cortex (PPC) is believed to be involved in the representation of spatial information, including spatial attentional processing. Because the PPC is extensively interconnected with frontal cortical regions involved in attention and executive function, we sought to determine whether PPC was involved in nonspatial attentional processes such as those of the frontal areas to which it projects. Lesions of the medial frontal cortex (in rats) or lateral prefrontal cortex (in nonhuman primates) impair the ability to shift attention from one perceptual dimension of a stimulus to another (referred to as an extradimensional shift). Rats with neurotoxic lesions of the PPC tested in an attentional set-shifting paradigm demonstrated a pattern of impairment identical to that of rats with medial frontal cortex lesions: they were selectively impaired on the extradimensional shift phase of the task. Performance in other phases of the task was indistinguishable from that of control rats, including the ability to reverse a previously learned discrimination. These findings are consistent with models that assign the PPC a prominent role in cortical attentional processing networks, as well as a role for the PPC in processing information about expectancy and surprise. They also suggest, importantly, that the interaction between the PPC and the frontal cortex is not limited to spatial attentional processing.
Animals↗
Change of oligosaccharides of rat brain microsomes depending on dietary fatty acids and learning task.
We have analyzed oligosaccharide chains in brain microsomes of rats fed an n-3 polyunsaturated fatty acid-deficient (safflower oil group; S group) or -rich (perilla oil group; P group) diet before and after brightness-discrimination learning tasks. The amount of concanavalin A-binding sites (mainly mannoside) of the brain microsomes was found to be significantly less in the S group than the P group before the learning task. Detailed analysis of glycoprotein glycans demonstrated that high mannose type oligosaccharides were dominant in brain microsomes before the learning task in both dietary groups, whereas multiantennary complex-type oligosaccharides became dominant after the learning task and especially a tetra-antennary glycan, that had a core structure of the glycan of neural cell adhesion molecule, was more increased in the S-group than the P group. When polysialylated glycans were analyzed on serotonin-conjugated HPLC column, the glycans in the S-group microsomes before the learning task contained larger amount of higher affinity-polysialylated glycans to serotonin column than those in the P-group, and also contained larger amount of phosphoglycans that showed also high affinity to serotonin column than the P-group. Removal of mannoside from microsomes by alpha-mannosidase-treatment changed the membrane surface physical property, especially permittivity, as revealed by analysis of the interaction with 1-anilinonaphthalene-8-sulfonate. These results suggest that high mannose content and several multiantennary glycans including polysialylated and phospho-glycans were changed by dietary n-3 fatty acid deficiency and learning task in rat brain microsomal glycoproteins and that these changes may affect membrane functions through changes of membrane surface physical properties and reactivity against serotonin.
Animals↗