The size of the hypothesis set during discrimination learning.
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Discrimination Learning↗
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Configural associations in discrimination learning.
In 4 experiments, Sprague-Dawley rats and homing pigeons received training with an A+ AB0 BC+ discrimination, in which food (+) accompanied trials with A and BC. Food was not presented (0) on trials with the compound AB. Subsequent test trials revealed that responding during C by itself, or the compound ABC, was slower than during either A or BC. Responding during the ABC compound was also found to be slower after training with the A+ AB0 BC+ than an A0 AB+ BC+ discrimination. We argue that these findings demonstrate the importance of configural associations in discrimination learning. Two accounts for the way in which these associations exert their influence are considered.
Animals↗
Fornix damage enhances successive, but not simultaneous, object-discrimination learning in cats.
The purpose of this study was to compare the effects of fornix lesions with the deficits known to follow septum lesions in cats learning visual object discriminations. In Experiment 1 when eight cats with aspiration lesions of the fornix performed successive discrimination problems, acquisition was greatly facilitated, but first- and second-reversal scores were normal by comparison with eight normal cats and two operated corpus callosum-control cats without fornix damage. Four corpus callosum-damaged cats with secondary degeneration in the medial fornix also learned the initial problem faster than normals. In Experiment 2 in a simultaneous paradigm, eight cats with fornix lesions scored like five normal controls, although they perseverated in early stages of reversal problems. The authors hypothesize that medial fornix damage, in contrast with septum lesions, enhances both initiation and maintenance of response inhibition.
Afferent Pathways↗
Visual discrimination learning in binocularly deprived cats: 20 years of studies in the Nencki Institute.
Data obtained by the author and his colleagues on various forms of visual discrimination learning in cats binocularly deprived of pattern vision with cloth masks (BD cats) are reviewed. In these studies two comparison groups were used: controls reared also in the laboratory but with open eyes (C cats) and cats reared in normal environment outside the laboratory (N cats). Data from other laboratories on lid-sutured and dark-reared BD cats are also shortly reviewed. The BD cats showed several clear-cut deficits. Those in pattern discrimination and in fine contrast discrimination were presumably mainly due to impairment of the perceptual inhibitory learning, whereas those in coping with the partition in the apparatus and in successive discrimination were due to impairment of associative inhibitory learning. The deficits in object discrimination and in interocular transfer were apparently due to a reduced number of binocular neurons in the deprived visual cortex and superior colliculi. Dramatic deficit in relearning after ablation of the superior colliculi-pretectum complex shows a reduced utilization of the abnormal cortex in discrimination learning. The C cats shared fully with BD cats a dramatic impairment in the visually delayed response. This short-term memory deficit was presumably due to a limited practice in visual learning in cage-reared cats. The C cats showed also some impairment in coping with the partition and in relearning after the colliculus-pretectum ablation. The BD cats were not impaired in pattern vs. no-pattern discrimination and in grating discrimination. Thus, visual deprivation does not impair the formation of excitatory and simple inhibitory connections required in crude discrimination. Moreover, presumably due to their less distractibility by external stimuli, the BD cats could be even superior to N and C cats in very crude discrimination tasks.
Animals↗
Septo-hippocampal cholinergic system under the discrimination learning task in the rat: a microdialysis study with the dual-probe approach.
To investigate regulation of the septo-hippocampal cholinergic system by dopaminergic inputs to the septum in rats which performed a discrimination learning task, an in vivo microdialysis method with the dual-probe approach was used. Rats were trained to discriminate between lamp-on and -off states under an operant-type learning procedure. After stable discriminative behavior was established, dialysis probes were implanted into the hippocampus and the lateral septum area of each rat. The concentration of dopamine (DA) in the septum rapidly increased within 20 min after the beginning of a learning session. However, another group of rats trained on a similar but non-discriminative task showed no such increase. The concentration of acetylcholine (ACh) in the hippocampus was significantly enhanced during the learning session and rapidly returned to the basal value after the session, but showed a delayed and diminished increase in the non-discrimination group. These results suggest that DAergic inputs to the septum may be involved in control of the septo-hippocampal cholinergic system which is of importance for discrimination learning behavior.
3,4-Dihydroxyphenylacetic Acid↗
The role of homecage environmental stimuli in the facilitation of shock-motivated spatial discrimination learning in rat pups.
In three experiments we examined the role of homecage environmental stimuli on learning an aversively motivated spatial discrimination task in 11-day-old rats. Varying the presence and absence of nest shavings in the correct and incorrect arms of a T-maze in Experiment 1 revealed that nest shavings had both nondirective facilitation and approach-eliciting properties. Training the 11-day-old rats in the presence or absence of shavings over three daily sessions and comparing their performance on the third day of training with that of a maturation control in Experiment 2 indicated that there is a residual training effect of the approach-eliciting property of nest shavings on shock-escape behavior. In Experiment 3, using nest shavings either as an irrelevant stimulus or as a redundant relevant cue in an aversively motivated T-maze reversal task suggested that 11-day-old rats acquire the discrimination task using non-nest spatial or directional cues as well as those provided by nest shavings. Overall, these results suggest that nest shavings introduced into aversively motivated tasks create a learning environment comparable to that of appetitively motivated instrumental tasks utilizing suckling from an anesthetized dam as a reinforcer.
Animals↗
The role of response-reinforcer relationship in discrimination learning of mentally retarded persons.
The role of the spatial relationship between target responses and reinforcers in the discrimination learning of mentally retarded subjects was evaluated. On each training trial, subjects were instructed to move a hand-operated manipulandum to a positive stimulus located at the left or right end of a track. Correct responses were immediately followed by onset of a light and presentation of an edible reinforcer. In the control condition the light and edible reinforcers were presented in a single location equidistant from the ends of the manipulandum track; in the experimental condition, they were presented directly adjacent to the terminus of the response at the end of the manipulandum track corresponding to the location of the correct stimulus. Results showed that discrimination performance was more efficient in the experimental condition than in the control condition.
Adult↗
The contribution of the rewarded and the non-rewarded stimulus in visual discrimination learning in mice.
The relative contribution of the rewarded and non-rewarded stimulus in the learning of a visual discrimination task in various species is unclear. A number of different parameters have been suggested as influencing the importance of the one over the other, among them the type of reinforcement. Our results show that with both positive reinforcement (using water as reward after a correct choice, and no reinforcement after an incorrect choice) and negative reinforcement (electroshock punishment after an incorrect choice) mice use the position of the incorrect stimulus as a cue for the discrimination. Mice trained by positive reinforcement without the added negative reinforcement of blocking the door on which the incorrect stimulus is projected, do not learn a brightness discrimination task. This suggested that the added negative reinforcement of the closed door had a strong influence on the learning behaviour in our experiments.
Animals↗
Neurobehavioral and systemic effects of longterm blood lead-elevation in rats. I. Discrimination learning and open field-behavior.
In order to assess neurobehavioral deficit subsequent to early low-level lead-exposure, Wistar-rats were prenatally Pb-exposed via their mothers, neonatally via their dams' milk, and later on via their diet containing lead acetate (745 mg Pb/kg diet). Blood-lead levels (PbB) of dams increased from 24.2-31.2 microgram-% during pregnancy and suckling-periods, those of offsprings were 26.6 microgram-% at about 16 days of age and 28.5 microgram-% at about 190 days of age. Between 100 and 200 days of age 40 male offsprings were subjected to behavioral testing, namely an open field-test and a visual discrimination-learning task. Two learning-tasks of different complexity, i.e. orientation- and size-discrimination, were used. Data of 20 lead-treated animals were compared with those of 20 age-matched controls. In the open-field test lead-fed animals were significantly more restless than controls; an increase of ambulation, rearing and grooming was observed. In the difficult learning-task, i.e. size discrimination, only the controls did learn the problem, whereas only one of the lead-group did; there was, however, no difference between lead- and control-animals for the easy task, i.e. orientation-discrimination. The observed effects, namely overreaction in the open field and a deficit of visual discrimination learning, may be interpreted in terms of lead-induced CNS-dysfunction. They clearly suggest that the "no-response level" for neurobehavioral damage in the rat, subsequent to early lead-exposure, must be assumed to be lower than 35 microgram/100 ml.
Animals↗
Differential effects of chlordiazepoxide on simultaneous and successive brightness discrimination learning in rats.
Chlordiazepoxide (CDP) at a dose of 20 mg/kg, i.p. was found to exert a marked disruptive effect on black-white successive discrimination learning in rats, while this effect failed to be obtained on black-gray simultaneous discrimination. Since trials to the learning criterion were found almost equal for saline rats on both successive and simultaneous discrimination tasks, the differential inhibitory effects of CDP could not be accounted for in terms of differences in difficulties of the two tasks. It is suggested that present results might be interpreted in terms of the hypotheses (a) that CDP produces a deficit in the integration of relevant stimulus cues when they were presented across trials or (b) that CDP has a disinhibitory effect in that inhibition of dominant response (positional preference) patterns is weakened by the drug, in a manner similar to effects observed in hippocampectomized animals.
Animals↗
Discrimination learning in preschool children as a function of the stimulus and relevant dimension.
The purpose of the present study was to determine discrimination learning rates as a function of the nature of the stimulus and the relevant dimension. Ss were 160 preschool boys and girls. The design consisted of two stimuli (faces and cups), two constant dimensions (size and form), and two relevant dimensions (form and color when the size dimension was held constant, and size and color when the form dimension was held constant). The errors to criterion scores revealed that for cup stimuli the color dimension was learned more rapidly than size and form, while for face stimuli the dimensions of size and form were learned more rapidly than color.
Child, Preschool↗
Effects of the Ca2+ channel antagonist flunarizine on visual discrimination learning.
Recent studies report that the peripheral administration of Ca2+ channel antagonists improves memory while central administration impairs memory in neurologically intact subjects. This study compares the effects of systemic versus central administration of the Ca2+ channel antagonist flunarizine on visual discrimination learning. In Experiment 1, 60 five-day-old male chicks received an intraperitoneal injection of 0, 1, 10, or 25 mg/kg flunarizine. Each chick then received three post-treatment test sessions (+5 min, +30 min, and +24 h) consisting of 60 visual discrimination trials followed by 5 min of observation in an open field. Flunarizine produced a dose- and time-dependent facilitation of learning. Evaluation of open-field behaviors indicated that the dose of flunarizine required to increase spontaneous activity was 10 times higher than the dose required to facilitate visual discrimination learning. No other open-field behaviors were effected. In Experiment 2, 44 chicks received intracerbroventricular injections of 0, 100 nM, 100 micro M, or 1 mM flunarizine followed by visual discrimination training as described in Experiment 1. Ventricular injection of flunarizine significantly increased the number of errors made during acquisition and retention trials. These data are consistent with earlier studies showing that systemic, but not central, administration of Ca2+ channel antagonists facilitates learning.
Animals↗
Conditioned manipulation of natural killer (NK) cells in humans using a discriminative learning protocol.
There is growing evidence indicating that the immune function can be modified by classical conditioning techniques. This phenomenon, initially explored in animals, is further documented by studies providing evidence that the human immune response can also be influenced by classical conditioning processes. In the present study, we tested the hypothesis that human immune parameters can be modulated by discriminative learning processes. Using a classical discriminative conditioning design, healthy volunteers were provided with a CS+ (sherbet sweet/white noise), which was repeatedly paired with an injection of epinephrine (unconditioned stimulus, US). After epinephrine injections (0.2 mg subcutaneously), a transient increase of natural killer (NK) cell activity (unconditioned response, UR) could be observed. A second stimulus complex (herbal sweet/auditory stimulus, conditioned stimulus, CS-) remained without reinforcement. After repeated presentation of the stimuli, re-exposure of the CS+ on the test trial 1 resulted in a significantly increased number of NK positive (NK+) cells and in slightly elevated NK cell activity. No alteration of NK cells, however, could be observed after presentation of the CS-. A second re-exposure of the CS+ on test trial 3, again resulted in a marked increase of NK+ cell number as well as in significantly elevated NK cell activity. The data presented here extend previous observations of conditioned alteration of immune responses in humans and indicate that the human organism might be able to react differentially to external stimuli, which have been associated with different immunological consequences.
Adult↗
Conditioned taste aversions as a behavioral baseline for drug discrimination learning: an assessment with phencyclidine.
When PCP was given prior to the pairing of saccharin with LiCl (and the PCP vehicle prior to a nonpoisoned exposure to the same saccharin solution), rats rapidly acquired the discrimination, avoiding saccharin consumption following PCP and consuming saccharin following the vehicle after only three conditioning trials. Conversely, when the PCP vehicle was given prior to the saccharin-LiCl pairing and PCP prior to a nonpoisoned exposure to saccharin, other subjects avoided saccharin consumption following the vehicle injection and readily consumed saccharin after an injection of PCP. During dose substitution sessions, animals displayed greater drug-appropriate responding as the dose of PCP increased. When a range of doses of ketamine was given in place of PCP prior to saccharin access, subjects displayed dose-dependent PCP-appropriate responding. When a range of doses of d-amphetamine was substituted for PCP, subjects displayed vehicle-appropriate responding at all doses. The relative efficacy of the taste aversion procedure as a baseline for drug discrimination learning is discussed.
Animals↗
Visual discrimination learning in spontaneously hypertensive (SHR) and Wistar normotensive rats: computerized analysis of choice strategies.
Spontaneously hypertensive rats (SHR) were found to learn a visual discrimination paradigm better than Wistar normotensive rats (NT). The present analysis of choice strategies used by rats was performed to detect possible correlates between patterns of responding and duration of learning. The following strategies were included into the analysis: perseveration and alternation of choice (response-set hypotheses), win-stay lose-shift and win-shift lose-stay (prediction hypotheses). A computer programme called "The Thinking Rat" was written to analyse rat strategies during the learning. The analysis was applied for two irrelevant dimensions of stimuli, i.e. position and orientation, and for colour as a relevant cue. SHR solved the task using different strategies than the NT rats. All subjects began by responding to position as a cue, but SHR gave up this strategy more quickly than NT rats did and responded earlier to colour. NT rats showed a strong preference to persevere in their choices with respect to stimulus position, whereas SHR used more frequently the prediction hypotheses with respect to colour. The analysis of performance and the analysis of choice strategies-could indicate that the discrepancy in learning between SHR and NT rats may be caused by differences in attention.
Analysis of Variance↗
Sodium amytal and the shock-right intensity function for visual discrimination learning.
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Amobarbital↗
Avoidance and discrimination learning following hippocampal ablation in the cat.
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Animals↗
Vicarious discrimination learning in retardates.
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Adolescent↗