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PubMed2006

Self-controlled visual discrimination learning of group-housed dwarf goats (Capra hircus): behavioral strategies and effects of relocation on learning and memory.

In most studies on animal learning, individual animals are tested separately in a specific learning environment and with a limited number of trials per day. An alternative approach is to test animals in a familiar environment in their social group. In this study, the authors--applying a fully automated learning device--investigated voluntary, self-controlled visual shape discrimination learning of group-housed dwarf goats (Capra hircus). The majority of the tested goats showed successful shape discrimination, which indicates the adaptive value of an effective learning strategy. However, in each group, a few individual goats developed behavioral strategies different from shape discrimination to get reward. Relocation impairs memory retrieval (probably by attention shifting) only temporarily for previously learnt shapes. The results demonstrate the usefulness of a self-controlled learning paradigm to assess learning abilities of social species in their normal social settings. This may be especially relevant for captive animals to improve their welfare.

Animals↗
PubMed1989

Effect of piracetam, a nootropic agent, on discrimination learning deficits induced by parental undernutrition and environmental impoverishment in young rats.

The study was conducted on 64 Charles Foster albino rats which were equally distributed into 8 even-matched groups, following a 2 x 2 x 2 factorial design by varying three independent factors at two levels: nutrition--normal and undernutrition, environmental--enrichment and impoverishment, and drug treatment--vehicle and piracetam (100 mg/kg, ip). Prenatal nutrition was induced by restricting the mother's food intake. The environmental enrichment/impoverishment and the vehicle/drug treatments were given during the postweaning period of the rat pups. The animals were subjected to original and subsequent reversal brightness discrimination learning tests in a single unit T-maze at 8-9 weeks of age. The results indicate that undernutrition and environmental impoverishment significantly attenuated the original discrimination as well as the reversal discrimination learning. Piracetam treatment improved the learning performance of normally reared rats and also attenuated the original and reversal learning deficits induced by prenatal undernutrition and postnatal impoverishment. The results indicate that piracetam may be useful in memory deficits induced by malnutrition.

Analysis of Variance↗
PubMed1997

Impairment of visual object-discrimination learning after perirhinal cortex ablation.

Eight cynomolgus monkeys learned preoperatively 20 concurrent visual discriminations between pairs of colored shapes presented on a touch screen with 24-hr intertrial intervals. Three then received bilateral perirhinal cortex ablation, and 5 remained controls. The ablated monkeys were severely impaired in reacquiring the preoperatively acquired set, whereas postoperative learning of 20 new discriminations was not significantly affected. The task was then made more difficult. First, the number of foils from which the stimulus had to be selected was increased to 2, 4, 7, and then 14. Second, larger sets of 40, 80, and 160 problems were presented. Both manipulations revealed some significant but relatively mild impairments in the monkeys with ablations. It is suggested that perirhinal cortex ablation impairs the monkey's capacity to identify individual objects, which leads to deficits in both visual-object recognition memory and discrimination learning.

Animals↗
PubMed1985

Genetic differences in avoidance learning by Rattus norvegicus: escape/avoidance responding, sensitivity to electric shock, discrimination learning, and open-field behavior.

The behaviors of rats selectively bred for either good or poor shuttle box avoidance learning were studied. The results of Experiment 1 indicated that the phenotypic difference in avoidance learning is not associated with differences in speed of escape or avoidance responding. Differences between the lines in frequency of intertrial responses (ITRs), which appear during training but not during pretest, suggest that ITRs in animals of the low-avoidance (SLA) line are more suppressed by electric shock than in animals of the high-avoidance (SHA) line. This result suggests that SLA animals may be more emotionally responsive than SHA animals. Experiment 2 demonstrated that the animals of the two lines do not differ in absolute sensitivity to electric shock, and Experiment 3 showed that the poor performance of the SLA line is not due to an inability to learn. Experiment 3 also provided evidence which suggests that the poor avoidance learning by SLA animals is due to their emotional reactivity. Observations of open-field behavior in Experiment 4 are consistent with this hypothesis. The major consistent correlate of the phenotypic difference in avoidance learning is greater emotionality or emotional reactivity in SLA than in SHA animals.

Animals↗
PubMed1988

Delta-9-tetrahydrocannabinol impairs visual recognition memory but not discrimination learning in rhesus monkeys.

The effects of orally administered delta-9-tetrahydrocannabinol (THC) were evaluated on two different learning abilities in monkeys. Visual recognition memory, known to depend on limbic system integrity, was tested by means of delayed nonmatching-to-sample and found to be significantly impaired by acute administration of 2 and 4 mg/kg THC given 1 or 2 h prior to testing. Performance was significantly impaired throughout a 21-day period of repeated administration of 4 mg/kg THC and also during a 3-5 day period that began 7-10 days after the last dose of THC. By contrast, 24-h concurrent discrimination learning, a task that monkeys with limbic lesions can perform normally, was not impaired by THC, even following doses as high as 16 mg/kg. These results suggest that THC interferes with recognition memory more than discrimination learning, possibly reflecting a selective action of THC on limbic mechanisms.

Administration, Oral↗
PubMed1991

Hippocampus and the blood supply to TE: parahippocampal pial section impairs visual discrimination learning in monkeys.

In the base of each temporal lobe in 4 monkeys (Macaca fascicularis) we sectioned the pia mater in an antero-posterior line along the most medial part of the inferior temporal visual association cortex (area TE), lateral to the parahippocampal cortex. This pial section interrupts the blood flow in branches of the posterior cerebral artery which cross the parahippocampal gyrus en route to area TE. Histologically, the brains of 2 of these animals did not show any abnormalities in cresyl violet stained material, apart from the small cortical damage along the line of the pial section itself. Of the remaining two animals, one had a small unilateral infarct in TE and one had bilateral infarcts in TE. All of these animals were impaired in visual discrimination learning, and the severity of impairment was correlated only imperfectly with the severity of infarction. These results show that pial section along the medial boundary of area TE can affect visual discrimination learning without producing large infarcts. Further, since aspiration lesions of the hippocampal formation require the pia mater to be sectioned in a similar way to that reported here, the effects of such aspiration lesions on visual learning and memory may be mediated in part by effects on TE.

Animals↗
PubMed2005

Systemic and prefrontal cortical NMDA receptor blockade differentially affect discrimination learning and set-shift ability in rats.

The authors examined discrimination rule learning and extradimensional set-shifting ability in rats given systemic or intracranial injections of the N-methyl-D-aspartate (NMDA) receptor antagonist MK801. Pretraining systemic injections of MK801 impaired both the acquisition of the initial discrimination rule (Set 1) and the shift to the 2nd rule (Set 2). Pretraining intramedial prefrontal cortical (mPFC) administration of MK801 did not impair Set 1 acquisition. Intra-mPFC injection of MK801 was previously found to impair Set 2 acquisition. Impaired Set 2 performance was due to increased cognitive perseveration. The data suggest that discrimination learning in naive subjects requires NMDA receptors outside the mPFC, whereas NMDA receptors within the mPFC are selectively involved in the modification of previous knowledge and/or the inhibition of previously learned responses.

Animals↗
PubMed2006

Early experience and domestication affect auditory discrimination learning, open field behaviour and brain size in wild Mongolian gerbils and domesticated laboratory gerbils (Meriones unguiculatus forma domestica).

The influence of early experience and strain differences on auditory discrimination learning, open field behaviour and brain size was investigated in wild-type Mongolian gerbils (strain Ugoe:MU95) raised in the wild (wild F-0) or in the laboratory (wild F-1) and in domesticated Laboratory Gerbils (LAB). Adult males were conditioned for 10 days in a shuttle box go/no-go paradigm to discriminate two frequency-modulated tones. Significant learning was established within 5 days in wild F-0 and within 3 days in wild F-1 and LAB. Spontaneous jumps in the shuttle box (inter-trial crossings) were frequently seen in wild F-0 and F-1, but rarely in LAB. All groups exhibited nearly the same ability to remember after 2 weeks without training. In the open field test applied on 5 consecutive days, no differences in locomotion patterns and inner field preferences were found. Rearing frequency decreased over 5 days in wild gerbils. Running distances (4-6m/min) were similar in wild F-0 and LAB, but higher in wild F-1. The ratio of brain size to body weight did not differ between wild F-0 and F-1, but was 17.1% lower in LAB. Correspondingly high brain weights in wild F-1 and F-0 support our domestication hypothesis and negate any serious effect of early experience or captivity on brain size in Mongolian gerbils. In contrast, wild F-1 raised in the laboratory show a rapid improvement in learning performance, indicating that early experience rather that genetic differences between strains affect shuttle box discrimination learning in gerbils.

Acoustic Stimulation↗
PubMed1985

Control of children's observing responses by information feedback during visual discrimination learning.

Four experiments examined the control of observing responses by information feedback during visual discrimination learning. Second-grade children participated in Experiment 1; kindergarten, second-, and fifth-grade children were subjects in Experiments 2 and 3, and grade 5 and adult subjects were tested in Experiment 4. In order to view the stimuli, subjects in Experiments 1, 2, and 3 activated lights in viewing boxes; in Experiment 4, stimulus fixations were measured using a corneal reflection technique. Fifth graders and adults observed the discriminative stimuli for longer times on trials following negative feedback than on trials following positive feedback; in contrast, kindergartener's observing was not affected by type of feedback. Second graders showed smaller and less reliable reactions to type of feedback than did older subjects. These results support the view that visual observing is controlled by cognitive processes associated with hypothesis testing.

Child↗
PubMed1996

Relationship between cholinergic dysfunction and discrimination learning disabilities in Wistar rats following chronic cerebral hypoperfusion.

The effects of chronic hypoperfusion of cerebral blood flow (CBF) on central cholinergic indices and intellectual functions were investigated in rats. Male Wistar rats, aged 9 weeks, were anesthetized with pentobarbital, and the bilateral common carotid arteries were permanently ligated. Cortical CBF in the hypoperfused rats was markedly decreased at 6 weeks after the operation. In the hypoperfused group, cholinergic indices were changed to consist two phases after the operation, before (acute) and after (chronic) 6 weeks after the operation. At 6 weeks, choline acetyltransferase activity was restored to the sham-operated level compared with the changes in the frontal cortex and thalamus + midbrain at 3 weeks. On the other band, the maximum number of muscarinic acetylcholine receptors was reduced in the frontal cortex, hippocampus and striatum at 6 weeks and thereafter remained at this low level. In discrimination learning task, the percentage of correct responses in the hypoperfused rats was generally reduced in contrast with that of the sham-operated rats, although the number of total responses were not changed. As a consequence, cholinergic dysfunctions correlate with discrimination learning disabilities in the hypoperfused rats. These findings suggest that the hypoperfused rat may be useful for the cerebrovascular type dementia model to clarify pathophysiology.

Analysis of Variance↗
PubMed1993

Operant conditioning after temporal lobe lesions in man: conditional and simple discrimination learning.

Temporal lobe lesions have been found to impair the acquisition of classical conditional discrimination learning in an eyelid conditioning paradigm, with sparing of simple eyelid conditioning. In the present study, subjects with left or right temporal resections were compared with normal controls on two operant conditioning tasks using a conditional and a simple discrimination paradigm analogous to the previously reported classical conditioning tasks. Subjects with right temporal lesions, and to a lesser extent those with left temporal lesions, were impaired relative to frontal lobe and control subjects in the acquisition of a conditional discrimination within an operant conditioning setting. A subsequent experiment showed that both left and right temporal lobe subjects were unimpaired on a simple operant discrimination task. These findings are compatible with theory relating hippocampal function to the learning of if-then rules.

Adult↗
PubMed1983

Luck and learning: feedback contingencies and initial success in verbal discrimination learning.

Ninety undergraduate volunteers learned a 12-pair, low frequency, verbal discrimination list. The independent variables were feedback (positive only, negative only, or both) and initial success (17%, 50%, or 83% correct on trial one). With the total errors on nine trials as the dependent variable, the main effect of feedback was found to be not significant. The main effect of initial success was significant. Subjects who started at 50% correct had the most difficulty learning the list and subjects in the 83% correct condition learned quickest. The predicted interaction between feedback and initial success was not significant, even though the means for the three types of feedback at the 17% correct starting level reflect the expected differences. The results are interpreted as supporting the rule-use component of frequency theory. The relationship between initial success and subsequent performance appears to be curvilinear, rather than linear, as many theorists have assumed.

Discrimination Learning↗
PubMed1990

[Investigation of cortical slow potentials during the delayed discrimination learning in monkeys].

Averaged slow potentials (SPs) were recorded at different training stages of delayed discrimination learning in two monkeys. The details of the task sequence was described in our previous work. It was found that at the early stages of the training the amplitude of SPs was very small, and it increased gradually with the increase of percentage of correct responses. The SPs recorded from the prefrontal cortex had the largest amplitude and there was no SPs recorded from the rear portion of the cortex. SPs recorded from the symmetrical sites of the two hemispheres showed no significant differences in amplitude and duration. Moreover, the SPs did not show significant differences in amplitude and distribution between two test models (R Model and B Model). The results obtained from the extinction experiments showed that after extinction of the behavioral responses the SPs disappeared. The results showed that the SPs recorded were learning-dependent and represented the association of events. As the SPs appeared in the delay period and were prefrontal-dominant, it was suggested that the prefrontal cortex might play an important role in short-term memory process.

Action Potentials↗