Le transfert interhémisphérique d'apprentissages visuels chez le chat à cerveau divisé: Effets de la situation expérimentale.

Demonstrated that the amount of residual interhemispheric transfer of pattern discrimination in split brain cats can be influenced by the nature of the training task. Three groups of Ss that had been subjected to an optic chiasma and a corpus callosum transection were each trained and tested for transfer in 1 of 3 experimental conditions: (1) the classical 2-choice discrimination apparatus with food reward; (2) a similar apparatus with incorrect trials punished with a painful electric shock; or (3) a Lashley-type jumping stand adapted for cats. Ss were tested on a number of patterns using either one or the other eye for learning and the naive eye for transfer testing. Results indicate that Ss tested in the 1st method showed no transfer, Ss given shocks for incorrect responses became neurotic, and Ss trained in the jumping stand showed no immediate transfer but rather good saving. Better transfer performance of the 3rd group may be a result of motivational factors in the testing situation and possibly increased facility to use secondary cues such as head and/or eye movements to make their discriminations. (English abstract) (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The contribution of the rat prelimbic-infralimbic areas to different forms of task switching.

The experiments examined the effects of prelimbic-infralimbic inactivation in rats on the acquisition and reversal learning of different discrimination tasks: 2- or 4-choice odor discrimination in Experiments 1 and 2, the shift from 2-choice odor discrimination to 2-choice place discrimination in Experiment 3, and the shift from 2-choice place to 2-choice odor discrimination in Experiment 4. Infusions of 2% bupivacaine did not impair performance in the odor discrimination tests. Prelimbic-infralimbic inactivation did not impair acquisition but did impair the shift from an odor to a place discrimination and vice versa. Analysis of the errors revealed that the deficit was due to perseveration of the previously learned strategy. The selective deficits observed in the odor-place tests suggest that the prelimbic-infralimbic areas enable behavioral flexibility when conditions demand inhibiting the use of one type of attribute information and learning a new type of attribute information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

La plasticité du système calleux.

Studied the potential plasticity of the callosal system in epileptic patients and kittens subjected to corpus callosotomy. Human Ss were 5 male and female Canadian children, adolescents, and adults (epilepsy) (corpus callosotomy). Animal Ss were 6 cats (corpus callosotomy at 20 or 45 days after birth). Human Ss were tested for unilateral tactile discrimination of a series of 30 familiar objects presented randomly to the right or left hand and for interhemispheric transfer of tactile information about 30 objects that were manipulated inside of a box. The cats were tested for unilateral discrimination of visual patterns and interhemispheric transfer of these patterns. The cats were trained to recognize the patterns with 1 eye and tested with the other. The results of both studies were analyzed according to age at which corpus callosotomy had been performed on the cats. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of experience on interocular transfer of pattern discriminations in split-chiasm and split-brain cats.

In a study with 8 cats, interocular transfer (IOT) of monocularly learned pattern discriminations was found to be imperfect in split-chiasm cats but to improve as a result of specific practice with IOT tasks. Section of the forebrain commissures subsequently performed in these Ss abolished immediate IOT of pattern discriminations. However, there were some savings in reattaining the learning criterion with the 2nd eye. Other cats that learned the same discriminations monocularly but had sustained a combined section of optic chiasm and forebrain commissures before learning showed no indication of IOT. Data suggest that the commissural systems involved in IOT and interhemispheric transfer of pattern discriminations may be modified by practice and learning. Further, it is possible that the intervening transfer experience between the section of the optic chiasm and that of the forebrain commissures results in the persistence of some capacity for IOT of pattern discriminations after commissurotomy. However, this residual capacity may be negligible when compared with the capacity for IOT of split-chiasm cats with intact forebrain commissures. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early and permanent effects of monocular deprivation on pattern discrimination and visuomotor behavior in cats

Visuomotor behavior and pattern discrimination were studied in a group of cats raised with one eye closed by eyelid suturing 7-10 days after birth. At the age of 8-10 months the animals were forced to use their deprived eye by reversal of eye closure (closing the normal eye and opening the deprived one). Visuomotor behavior and pattern discrimination were tested before as well as after reverse closure, to compare performances of the deprived eye with those of the non-deprived eye. In order to get optimal visuomotor experience, the animals were kept in large playrooms for at least 4h each day. Except for normal tactile placing responses, visually triggered extension responses and uncertain jumping, 2 years after reverse closure all other tests (visually guided reaching, visual cliff behavior, obstacle avoidance, tracking, jumping, and visual blink responses) still showed impairments; the optokinetic nystagmus was asymmetric. In contrast with this partial behavioral recovery, pattern discrimination in a simple nose-push training box requiring no complicated visuomotor coordination was found to be positive. Discriminations of gratings of different orientations, starting 4 weeks after reverse closure, appeared to be normal, in comparison with performance using the non-deprived eye of the same cats tested before reverse closure. Form discrimination was also found to be positive; some monocularly deprived cats required more trails than normal cats in upright vs. reversed solid triangles discrimination, but succeeding form problems were mastered within the same range as found in normal cats. Apparently behavioral defects after monocular deprivation are due to deficiencies in visuomotor control rather than in pattern identification.     

Interocular transfer in the split-brain rat.

After the 1991 development of a method to transect the optic chiasm in the rat, the authors investigated interocular transfer in split-chiasm rats with corpus callosum section and callosum intact. 17 male rats were monocularly trained on an orientation discrimination, reversed with the other eye, and retrained with the 1st eye on the 2nd-eye problem or reversal. In split-chiasm rats, the 2nd-eye S+ (correct stimulus) showed strong transfer (55% savings) to the 1st eye. S– (incorrect stimulus) did not; reversal and transfer groups differed significantly. Split-brain rats retrained with the 1st eye on the 2nd eye S+ required no more trials than original learning, as if they had not experienced this problem. Split-brain rats retested with the original S+ showed modest (19%) savings. The findings establish interhemispheric communication via the callosum and suggest, as in findings of cat and monkey studies, the disruption of transfer by callosal section. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination and switching learning in normal, familial retarded, and organic retarded children.

In an effort to explicate the contradictory findings of earlier studies, normals, familial retardates, and organic retardates at 2 MA levels were trained on either a 3-choice or a 2-choice discrimination task. Following solution of the original task Ss were switched to either a new 3-choice discrimination, a 2-choice transposition, or a 2-choice reversal problem. There were no significant types of S main effects on either the 1st or 2nd problems. It was concluded that the findings offered no support for the view that the cognitive functioning of retardates is inherently different from normals of the same MA. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrasting effects of lateral striate and superior colliculus lesions on visual discrimination performance in rhesus monkeys.

Tested 3 rhesus monkeys with lesions of lateral striate cortex (LSC), 4 monkeys with superior colliculus (SC) lesions, and 3 unoperated monkeys for retention of a preoperatively acquired pattern discrimination. The 3 groups of monkeys were then tested in 2-choice, color discrimination tests, 1 involving varying degrees of stimulus–response (S–R) separation and the other, administered several months later, involving various directions of S–R separation. Ss were also tested in a series of 2-choice pattern discriminations, following each of which they were tested for relearning when the patterns were masked with bars or circles. LSC lesioned Ss were moderately retarded in retention of the pattern discrimination, whereas those with SC lesions were not. SC lesioned Ss, but not those with LSC lesions, were impaired in both S–R separation tests, which demonstrates that their deficit was not transient or solely due to a difficulty in shifting the gaze in 1 direction. The LSC Ss, unlike those with SC lesions, were deficient in relearning discriminations between masked patterns. Findings suggest that SC and LSC may be involved in 2 different aspects of attention, respectively: shifting attention (and orientation) from 1 spatial locus to another and maintaining attention on fixated stimuli. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effect of early enrichment and deprivation on learning in the rhesus monkey (Macaca mulatta).

Conducted an experiment with 24 rhesus monkeys to extend research findings concerning the effects of early experience on nonhuman primate learning ability. Enriched Ss tested in their home living environment performed more proficiently than Ss separated from their living environments and tested in an adjoining room. Further, Ss reared in enriched environments were superior to partially isolated controls on the complex oddity tasks but not on 2-choice discrimination or delayed-response problems. (33 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus monkeys (macaca mulatta) immediately generalize the uncertain response.

Rhesus monkeys (Macaca mulatta) have learned, like humans, to use an uncertain response adaptively under test conditions that create uncertainty, suggesting a metacognitive process by which human and nonhuman primates may monitor their confidence and alter their behavior accordingly. In this study, 4 rhesus monkeys generalized their use of the uncertain response, without additional training, to 2 familiar tasks (2-choice discrimination learning and mirror-image matching to sample) that predictably and demonstrably produce uncertainty. The monkeys were significantly less likely to use the uncertain response on trials in which the answer might be known. These results indicate that monkeys, like humans, know when they do not know and that they can learn to use a symbol as a generalized means for indicating their uncertainty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Constant irrelevant cues and stimulus generalization in monkeys.

Trained 14 jungle-born female pigtailed monkeys to criterion on 2 concurrently presented 4-choice object discriminations. In 1 problem form was relevant and color constant irrelevant; in the other, color was relevant and form constant irrelevant. Following training, Ss were given transfer tests with a 4-choice setting consisting of the 2 formerly rewarded objects, a 3rd object composed of the rewarded relevant features of the color and form discriminations, and a 4th object constructed from the 2 constant irrelevant color and form features. Ss consistently chose the previously rewarded objects during transfer, but of the new objects, almost always chose the object constructed of relevant features. A number of models for discrimination learning are considered in the light of these data. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acoustic classification of alarm calls by vervet monkeys (Cercopithecus aethiops) and humans (Homo sapiens): I. Natural calls.

A 2-choice, operant-conditioning-based classification procedure was developed in which vervet monkeys (Cercopithecus aethiops) categorized species-typical snake and eagle alarm calls recorded from individually identified free-ranging animals. After preliminary training with a pair of calls from a single animal, 2 vervets were tested with novel exemplars produced by a variety of callers. Experiment 1 combined testing with continued training in routine classification of 14 new calls. In Experiment 2, the Ss were tested with 48 novel calls in rapid succession. Human (Homo sapiens) control Ss participated in the 1st study without extended preliminary training. Monkey and human Ss both showed immediate transfer to classification of unfamiliar alarm calls, despite variations both in voice characteristics and reproduction quality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Color vision in horses (Equus caballus): Deficiencies identified using a pseudoisochromatic plate test.

In the past, equine color vision was tested with stimuli composed either of painted cards or photographic slides or through physiological testing using electroretinogram flicker photometry. Some studies produced similar results, but others did not, demonstrating that there was not yet a definitive answer regarding color vision in horses (Equus caballus). In this study, a pseudoisochromatic plate test--which is highly effective in testing color vision both in small children and in adult humans--was used for the first time on a nonhuman animal. Stimuli consisted of different colored dotted circles set against backgrounds of varying dots. The coloration of the circles corresponded to the visual capabilities of different types of color deficiencies (anomalous trichromacy and dichromacy). Four horses were tested on a 2-choice discrimination task. All horses successfully reached criterion for gray circles and demonstration circles. None of the horses were able to discriminate the protan-deutan plate or the individual protan or deutan plates. However, all were able to discriminate the tritan plate. The results suggest that horses are dichromats with color vision capabilities similar to those of humans with red-green color deficiencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization learning in horses (Equus caballus).

Categorization learning was investigated in 2 horses (Equus caballus). Both horses learned to select a 2-dimensional black stimulus with an open center instead of a filled stimulus in a 2-choice discrimination task. After a criterion of 10 out of 10 correct responses in a random series for 2 consecutive sessions was reached, 15 additional pairs of open-center versus filled stimuli were tested. Each was run to criterion and then incorporated into sessions of randomly mixed problems. Both horses solved the 1st problem by simple pattern discrimination and showed evidence of categorical processing for subsequent problems. New pairs were learned with few or no errors, and correct responses on novel trials were significantly above chance. These results suggest that the horses were making their selections on the basis of shared characteristics with the training stimuli and were using categorization skills in problem solving. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric transfer of visual discriminations in split-chiasm monkeys (Macaca nemestrina) and its measurement.

The interhemispheric transfer of visual discriminations in split-chiasm monkeys (Macaca nemestrina) was assessed by training with one eye to a criterion level, then testing either with that same eye (control) or with the other eye (transfer). The difference between these 2 values was the loss due to transfer. A computer simulation suggested that the usual savings score could grossly misestimate transfer ability. In addition, stimuli with comparable left and right halves were used to minimize the effect of the bilateral hemianopia caused by chiasm section. Performance with the untrained eye was slightly, but statistically significantly, poorer than with the trained eye. No evidence of the phenomena of "learning to transfer" was found (i.e., there was no improvement in transfer ability in relation to concurrent intrahemispheric controls). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of caffeine on nicotine's discriminative stimulus, subjective, and reinforcing effects.

Caffeine may acutely alter the discriminative stimulus and subjective effects of nicotine, perhaps explaining the association of coffee intake with smoking status. In this study, smokers were initially trained to discriminate 20 μg/kg nicotine by nasal spray from placebo (0). Then, generalization of nicotine discrimination was tested, using both 2- and 3-choice ("novel" option) procedures, across a range of doses (0-20 μg/kg) following pretreatment with 0, 2.5, and 5.0 mg/kg caffeine p.o. Nicotine reinforcement was assessed after the end of generalization testing using a choice procedure. Caffeine pretreatment did not alter nicotine discrimination and self-administration. Caffeine and nicotine influenced some subjective and cardiovascular responses, but there were no interaction effects except for diastolic blood pressure. These results do not support the notion that caffeine acutely alters nicotine's discriminative stimulus, subjective, or reinforcing effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the dorsomedial striatum in behavioral flexibility for response and visual cue discrimination learning.

These experiments examined the effects of dorsomedial striatal inactivation on the acquisition of a response and visual cue discrimination task, as well as a shift from a response to a visual cue discrimination, and vice versa. In Experiment 1, rats were tested on the response discrimination task followed by the visual cue discrimination task. In Experiment 2, the testing order was reversed. Infusions of 2% tetracaine did not impair acquisition of the response or visual cue discrimination but impaired performance when shifting from a response to a visual cue discrimination, and vice versa. Analysis of the errors revealed that the deficit was not due to perseveration of the previously learned strategy, but to an inability to maintain the new strategy. These results contrast with findings indicating that prelimbic inactivation impairs behavioral flexibility due to perseveration of a previously learned strategy. Thus, specific circuits in the prefrontal cortex and striatum may interact to enable behavioral flexibility, but each region may contribute to distinct processes that facilitate strategy switching. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor preferences in cats (Felis catus and Panthera sp.).

Conducted 4 experiments with 28 domestic and 12 wild cats to examine flavor preference in cats. In the 1st experiment domestic Ss exhibited no preference (both in 24-hr and 1-hr 2-choice preference tests) for any of a variety of carbohydrate or artificial sweeteners regardless of whether a water or saline diluent was employed. A preference for sucrose or lactose dissolved in dilute milk compared with dilute milk alone was observed. This preference may have been based on textural rather than flavor characteristics of the milk-sugar solution. In the 2nd experiment a similar lack of preference for carbohydrate sweeteners was found when using 5-min 2-choice preference tests with wild Ss (genus Panthera). In light of this lack of sweet preference among cats, Exps III and IV examined responses to solutions of hydrolyzed protein and individual amino acids and to emulsified fat mixtures. Solutions of hydrolyzed soy, lactalbumin, and casein; l-alanine and l-proline solutions; and butterfat mixtures were all preferred to the diluent. It is suggested that a pattern of responses characterized by an avidity for protein and fat products and no avidity for carbohydrate sweeteners may be typical of strict carnivores like cats. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A model of the go/no-go task.

In this article, the first explicit, theory-based comparison of 2-choice and go/no-go variants of 3 experimental tasks is presented. Prior research has questioned whether the underlying core-information processing is different for the 2 variants of a task or whether they differ mostly in response demands. The authors examined 4 different diffusion models for the go/no-go variant of each task along with a standard diffusion model for the 2-choice variant (R. Ratcliff, 1978). The 2-choice and the go/no-go models were fit to data from 4 lexical decision experiments, 1 numerosity discrimination experiment, and 1 recognition memory experiment, each with 2-choice and go/no-go variants. The models that assumed an implicit decision criterion for no-go responses produced better fits than models that did not. The best model was one in which only response criteria and the nondecisional components of processing changed between the 2 variants, supporting the view that the core information on which decisions are based is not different between them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial reversal learning and the evolution of behavioral flexibility in three species of North American corvids (Gymnorhinus cyanocephalus, Nucifraga columbiana, Aphelocoma californica).

In serial reversal learning, subjects learn to respond differentially to 2 stimuli. When the task is fully acquired, reward contingencies are reversed, requiring the subject to relearn the altered associations. This alternation of acquisition and reversal can be repeated many times, and the ability of a species to adapt to this regimen has been considered as an indication of behavioral flexibility. Serial reversal learning of 2-choice discriminations was contrasted in 3 related species of North American corvids: pinyon jays (Gymnorhinus cyanocephalus), which are highly social; Clark's nutcrackers (Nucifraga columbiana), which are relatively solitary but specialized for spatial memory; and western scrub jays (Aphelocoma californica), which are ecological generalists. Pinyon jays displayed significantly lower error rates than did nutcrackers or scrub jays after reversal of reward contingencies for both spatial and color stimuli. The effect was most apparent in the 1st session following each reversal and did not reflect species differences in the rate of initial discrimination learning. All 3 species improved their performance over successive reversals and showed significant transfer between color and spatial tasks, suggesting a generalized learning strategy. The results are consistent with an evolutionary association between behavioral flexibility and social complexity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)