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PubMed1995

Spatial discrimination learning and choline acetyltransferase activity in streptozotocin-treated rats: effects of chronic treatment with acetyl-L-carnitine.

Treatment of rats with i.c.v. injected streptozotocin (STREP) may provide a relevant model of neurodegeneration that is induced by a decrease in the central metabolism of glucose. Acetyl-L-carnitine (ALCAR) enhances the utilization of alternative energy sources and by such a mechanism of action ALCAR could antagonize the effects of STREP treatment. In this study the effects of chronic treatment with ALCAR were evaluated on spatial discrimination learning in the Morris task and choline acetyltransferase (ChAT) activity of middle-aged STREP-treated rats. Chronic treatment with ALCAR attenuated both the STREP-induced impairment in spatial bias and the decrease in hippocampal ChAT activity. These findings indicate that ALCAR treatment has a neuroprotective effect, although further studies are needed to characterize the mechanism of action of ALCAR in this model.

Acetylcarnitine↗
PubMed2000

Individual differences in the functional neuroanatomy of verbal discrimination learning revealed by positron emission tomography.

Why do some people have better memory abilities than others? This issue has been of long-standing interest to scientists and lay people. However, using purely behavioral methods, psychologists have made little progress in illuminating it. Now that functional brain imaging techniques have become available to study mind/brain relations, there is a new promise of understanding individual differences in learning and memory in terms of corresponding differences in brain activity. In this paper, we will present a positron emission tomography (PET) study designed to examine individual differences in learning and memory abilities. The basic assumption is that different patterns of brain activity serve as strong predictors of memory performance. Two specific questions were addressed in this study: (i) Can PET illuminate the relations between memory processes and their neuroanatomical correlates among individual learners and rememberers? and (ii) if so, how are these relations affected by the stage of practice on a given memory task? Our PET study examined individual differences in the neuroanatomical correlates of multi-trial verbal discrimination learning in 16 young healthy subjects. The results identified patterns of brain regions in which blood flow correlated with subjects' retrieval performance. However, these regions did not correlate with performance during all learning trials. Instead, a gradual shift was observed from one pattern of brain regions to another over the course of learning. These results suggest that individual differences in memory performance are related to differences in neural activity within specific brain circuits.

Adult↗
PubMed1988

Changes in discrimination learning and brain activity (ERP's) due to combined exposure to NO and CO in rats.

Carbon monoxide (CO) and nitric oxide (NO) are air pollutants frequently appearing in combination. Information available on the mechanisms of NO intoxication suggests that in mixtures with CO additive effects should be assumed. In this study CO and NO-induced changes and their interaction were investigated at different levels of integration: carboxyhemoglobin (COHb) and methemoglobin (met-Hb) formation as well as centrally mediated effects were analyzed using evoked potential techniques and behavioral data from a complex discrimination learning experiment. Slight enhancements of COHb and met-Hb concentrations were seen for the combined CO + NO exposure conditions at low and high exposure levels when compared to isolated exposure conditions. The performance decrease was clearly higher under NO exposure than under CO exposure. Decrements were overadditive when simultaneous CO + NO exposure was used in higher concentration. Both gases affected early evoked potential components (P10, N30) in the same way: latencies were prolonged and amplitudes increased. Later potential components were differently influenced by CO and NO. Mainly the N150 amplitude was decreased in NO exposure and increased in CO conditions. N150 amplitude was also decreased after combined CO + NO exposure. At high levels this effect was overadditive indicating a dominant role of NO in the CO + NO combinations used in this experiment.

Animals↗
PubMed2006

[Expression of caveolin-1 protein in the rat brain and its role in the discrimination learning].

Caveolin-1 (Cav-1) is a marker protein for caveolae, and acts as scaffolding protein to regulate the activities of signaling molecules. Previous studies indicate that Cav-1 mainly locates at the base of axonal and dendritic terminals of mouse primary hippocampal neurons and plays an active role in the regulation of injury-induced synaptic and terminal remodeling in central nervous system. The aim of this study was to identify the expression profile of Cav-1 protein in the brains of rats at different ages and to investigate the role of Cav-1 in Y-maze bright-dark discrimination learning (BDL). Firstly, the expressions of Cav-1 in the brains of young (1-month), adult (3-month) and aged (22-month) rats were observed by Western blot. Higher expression in the hippocampus and lower expression in the cortex were shown in the adult rats. It was also found that the score of BDL was related with the expression level of Cav-1. Secondly, using open-field test for spontaneous locomotor activities (SLA) and BDL, the role of Cav-1 in the learning and memory was observed. Compared with that in the control adult group, the Cav-1 protein expression in the hippocampus and prefrontal cortex of Y-maze trained adult rats significantly increased, while no marked changes in the cerebellum. These results suggest that Cav-1 protein is involved in BDL and plays an important role in the plasticity of central nervous system.

Age Factors↗
PubMed1983

The effects of lesions to ascending noradrenergic neurons on discrimination learning and performance in the rat.

Three experiments examined the effect of central noradrenergic depletion on the acquisition and performance of a temporal discrimination in auditory or visual modalities. In Experiment 1, 6-hydroxydopamine-induced lesions of the dorsal noradrenergic bundle significantly retarded acquisition compared to a similarly lesioned ventral noradrenergic bundle-group, two sham-operated and one unoperated control group. In Experiment 2, the acquisition impairment produced in the dorsal noradrenergic bundle group was replicated, for both auditory and visual modalities, by lesions depleting hippocampal and neocortical noradrenaline by over 80%. In rats subsequently switched to discriminations involving the unfamiliar modality, the dorsal-bundle lesion also impaired acquisition several weeks after surgery. Experiment 3 showed significantly impaired performance in rats with dorsal bundle lesions when training prior to surgery had not resulted in better than chance performance. In rats previously trained to criterion, the dorsal bundle lesion transiently, but non-significantly, impaired performance. In rats performing better than chance, but not having reached criterion, there were no significant effects of the dorsal bundle lesion. Subsequent manipulations of deprivation and difficulty of discrimination in general failed to distinguish between the dorsal bundle lesion and sham-groups, suggesting that the acquisition impairment did not result from simple sensory or motivational effects. Reducing the interstimulus interval did impair the dorsal bundle group more than controls. However, there was no evidence of altered "distractibility" in the lesioned group when the alternative modality was introduced as a distractor. The results are discussed in terms of other acquisition deficits shown by rats with central noradrenaline depletion and their significance for determining the functions of the projections from the locus caeruleus via the dorsal noradrenergic bundle to the neocortex and hippocampus.

Afferent Pathways↗
PubMed1999

Hormones of the hypothalamo-pituitary-gonadal axis in drug discrimination learning.

More than 30 years ago, T-maze studies with progesterone indicated that sex hormones have the potential to act as a discriminative stimulus in rats. Despite these early positive findings, the interest in discriminative stimulus properties of sex hormones remained low; few studies were dedicated to the investigation of discriminative stimulus properties of hypothalamo-pituitary-gonadal axis hormones (i.e., LHRH, LH/FSH, sex steroids). Nevertheless, the few studies that were published showed some interesting, and often sex-dependent results. Applying various methodologies (T-, or Y-maze, two-lever drug discrimination, taste aversion procedures), it was found that not only progesterone but also the two other principal sex steroids estradiol and testosterone can serve as discriminative stimuli in rodents. In addition to these gonadal hormones, the hypothalamic peptide LHRH (having a key role in the neuroendocrine regulation of steroid release from the gonads) appears to generate discriminative stimulus properties. Interestingly, recent (but preliminary) studies in postmenopausal women suggest that estradiol (and possibly progesterone) may also function as a discriminative stimulus in human subjects.

Animals↗
PubMed1959

Discrimination learning.

Eight rats were run through discrimination training sessions in which responses in the dark were not reinforced whereas the first response after the onset of a light was reinforced. The procedure generated orderly learning and latency data for the individual animal. The latency distributions are adequately described by a simple mathematical formulation.

Animals↗
PubMed2006

Perirhinal cortex lesions impair simultaneous but not serial feature-positive discrimination learning.

The role of the perirhinal cortex in discriminative eyeblink conditioning was examined by means of feature-positive discrimination procedures with simultaneous (A-/XA+) and serial (A-/X-->A+) stimulus compounds. Lesions of the perirhinal cortex severely impaired acquisition of simultaneous feature-positive discrimination but produced no impairment in serial feature-positive discrimination. The results suggest that the perirhinal cortex plays a role in discriminative eyeblink conditioning by resolving ambiguity in discriminations with overlapping stimulus elements.

Animals↗