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PubMedDate not supplied

Monkey perirhinal cortex is critical for visual memory, but not for visual perception: reexamination of the behavioural evidence from monkeys.

Overdependence on discrimination learning paradigms to assess the function of perirhinal cortex has complicated understanding of the cognitive role of this structure. Impairments in discrimination learning can result from at least two distinct causes: (a) failure to accurately apprehend and represent the relevant stimuli, or (b) failure to form and remember associations between stimulus representations and reward. Thus, the results of discrimination learning experiments do not readily differentiate deficits in perception from deficits in learning and memory. Here I describe studies that do dissociate learning and memory from perception and show that perirhinal cortex damage impairs learning and/or memory, but not perception. Reanalysis and reconsideration of other published data call into further question the hypothesis that the monkey perirhinal cortex plays a critical role in visual perception.

Animals↗

PubMed1991

Cerebellar interpositus nucleus lesions disrupt classical nictitating membrane conditioning but not discriminative avoidance learning in rabbits.

Cerebellar interpositus nucleus lesions were given to 14 rabbits trained in two behavioral paradigms; discriminative avoidance conditioning of locomotor behavior and classical nictitating membrane conditioning. Bilateral lesions that prevented acquisition of the classically conditioned response on both the left and right side failed to affect the acquisition or performance of the conditioned discriminative avoidance response. The results are discussed in terms of differences in neural substrates that apparently subserve the two forms of learning.

Animals↗

PubMed1990

Auditory discrimination, attention, learning, and memory in paranoid schizophrenics.

The present research was designed to assess auditory discrimination, attention, memory, and learning in paranoid schizophrenic patients using a dichotic listening procedure consisting of attending to a signal or a story channeled only to one ear. A sample of 24 paranoid schizophrenics and 24 normal controls volunteered. In Experiment 1, 12 schizophrenics and 12 controls attended to the signal while shadowing the story. The task of the other 12 clinical and 12 normal subjects in Experiment 2 was identical to Experiment 1 with the exception that the subjects did not shadow the story. In each experiment, subjects completed three trials as well as three evaluations of the story. The results indicated that schizophrenics showed substantial attentional deficits in comparison to normal controls.

Journal Article↗

PubMed1989

Differences in open-field behavior and in learning tasks between two rat strains differing in their reactivity to stressors.

The study characterizes differences between inbred Wistar-Kyoto (WKYs) and Brown-Norway (BNs) rats in open-field behavior, and in discriminative learning and acquisition of an avoidance learning task. Hyper-reactivity of WKYs to novelty was demonstrated in an open-field test. Discriminative learning and retention thereof was slower in WKYs, but as efficient as in BNs. Acquisition of avoidance learning was also slower in WKYs, but their maximal avoidance score was much higher (approximately 85%) than in BNs. Also, recall of avoidance learning was slower for WKYs. We conclude: (1) hyper-reactivity of WKYs to novelty is expressed by their exceptional immobility and excess defecation in the open-field and is paralleled by their known hyper-reactivity to stressful stimuli, and (2) no strain differences exist in the ability to learn a discriminative task, but both acquisition and recall of an avoidance task are slower in WKYs. This may imply that the degree of reactivity to stressful environmental stimuli may play an important role in the acquisition of learning.

Animals↗

PubMed1983

Discriminated instrumental learning by an acute encéphale isolé preparation.

Rats were prepared and maintained with high cervical transections in order to study learning in an intact brain that is isolated from uncontrolled sensory input and immobilized, allowing ready access to central physiological mechanisms. Stimulation electrodes were aimed at loci associated with response reinforcing processes. A response sensor was placed in the mouth to record both learned and evoked biting. All experimental subjects were trained successfully to discriminate the presence of an exteroceptive stimulus that indicated availability of the brain stimulation for biting. An intact control subject performed similarly in a lever pressing situation for brain stimulation. Biting also was evoked in both experimental and control subjects following removal of reinforcers, in a relation like that previously demonstrated between withdrawal of reinforcers and attack. The value of the experimental procedure in the study of the neural bases of learning and of the interactions between learned and inherent response processes is discussed.

Aggression↗

PubMed1989

Automation of learning-set testing: the video-task paradigm.

Researchers interested in studying discrimination learning in primates have typically utilized variations in the Wisconsin General Test Apparatus (WGTA). In the present experiment, a new testing apparatus for the study of primate learning is proposed. In the video-task paradigm, rhesus monkeys (Macaca mulatta) respond to computer-generated stimuli by manipulating a joystick. Using this apparatus, discrimination learning-set data for 2 monkeys were obtained. Performance on Trial 2 exceeded 80% within 200 discrimination learning problems. These data illustrate the utility of the video-task paradigm in comparative research. Additionally, the efficient learning and rich data that were characteristic of this study suggest several advantages of the present testing paradigm over traditional WGTA testing.

Animals↗

PubMed1998

Resistance to interference in human associative learning: evidence of configural processing.

In 4 experiments the authors used 2-stage designs to study susceptibility to interference in human discrimination learning. The experiments used a food allergy task. In Experiment 1, participants were presented with a discrimination in Stage 1 in which Food A predicted an allergy outcome (A-->O). In Stage 2, when combined with Food B, Food A predicted the absence of the allergy (B-->O, AB-->no O). In the test phase, Food A was found to have retained its Stage 1 association with the allergy despite the potentially interfering Stage 2 trials. In Experiment 2, a discrimination between 2 compounds (AB-->O, CD-->no O) remained intact despite subsequent complete reevaluation of the elements, (A-->no O, B-->no O, C-->O, D-->O); in Experiments 3 and 4, a discrimination between 2 pairs of elements (A-->O, B-->O, C-->no O, D-->no O) remained intact despite subsequent complete reevaluation of the AB and CD compounds, (AB-->no O, CD-->O). These experiments yielded evidence of remarkable resistance to interference in human discrimination learning. The results are at variance with the predictions of J. M. Pearce's (1987, 1994a) configural theory of associative learning.

Association Learning↗

PubMed1983

Multiple-unit activity of the prefrontal cortex and mediodorsal thalamic nucleus during reversal learning of discriminative avoidance behavior in rabbits.

Multiple-unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) thalamic nucleus was recorded during reversal training following differential conditioning of a locomotory (wheel rotation) avoidance response in rabbits. The positive and negative conditional stimuli (CS+ and CS-) were pure tones and the unconditional stimulus (UCS) was footshock. A major objective was to compare the activity in the PFC and MD nucleus with that in the neighboring cingulate cortical and anteroventral (AV) thalamic system, studied previously. During the first session of reversal training the rostral-sulcal subfield of the PFC manifested significant discriminative activity appropriate to the original habit, i.e., a greater discharge to the original CS+ than to the original CS-. The difference between the CS+ and CS- elicited discharges diminished as reversal learning progressed, but discriminative activity appropriate to the reversal problem did not develop. The medial subdivision of the MD nucleus which is interconnected reciprocally with the rostral-sulcal PFC subfield did not manifest discriminative activity during reversal training (nor had it done so during original learning). The caudal subfield of the PFC (which had shown rapidly developing acquisition of the discriminative discharges followed by diminution of the discriminative discharges during original training) manifested an original discriminative effect in the initial session of reversal training followed by the reverse discriminative discharge in the criterial session. The lateral subdivision of the MD nucleus which is interconnected reciprocally with the caudal PFC subfield, also manifested the original discriminative effect in the initial session of reversal training, followed by the reverse discriminative effect during the subsequent (precriterial and criterial) sessions. Thus, as in the AV nucleus, the lateral MD subdivision showed earlier and more robust development of discriminative activity appropriate to the reversal problem, than its cortical counterpart. The present results also suggested that cerebral cortical areas such as the caudal PFC, which transfer discriminative activity to their respective thalamic nuclei during discriminative acquisition, are subsequently more likely to manifest the reverse discriminative activity, than are cortical areas such as the rostral-sulcal subfields of the PFC, which do not transfer their discriminative activity.

Animals↗

PubMed1976

Effects of neonatal cerebral ventricular injection of ACTH 4-9 and subsequent adult injections on learning in male and female albino rats.

An investigation of permanent developmental effects of a potent, long acting ACTH/MSH 4-10 analogue (Organon 2766) on adult passive avoidance performance and of subsequent peripheral adult injections of the same substance on visual (black and white) discrimination learning and reversal in a Thompson-Bryant box was conducted. A subproblem analysis of visual and position preferences during reversal was performed. No differences in passive avoidance performance or in original discrimination learning were obtained. Both infant and adult treatments enhanced reversal learning and visual orientation (proportion of responese to the previously positive stimulus). Infant treatment suppressed position orientation in males and enhanced position orientation in females. These effects were interpreted as indicating that ACTH-like peptides enhance attention to the relevant stimulus by a direct effect on the brain.

Adrenocorticotropic Hormone↗

PubMed1984

Stimulus overselectivity in autistic and mentally retarded children--a research note.

Groups of autistic and mentally retarded children were compared for the degree of stimulus overselectivity manifested during test probes after discrimination learning. Results demonstrated that stimulus overselectivity was a function of diagnostic category when groups were equated for performance IQ and mental age. Procedures used to obtain IQ as well as discrimination learning rate were also shown to be equivalent. Pulse rate response suggested that the test probes may be assessing performance during the early trials of a transfer problem for both groups of children. Implications for 'one-look' models of discrimination learning were discussed.

Arousal↗

PubMed1992

Taste-potentiated odor aversion learning: role of the amygdaloid basolateral complex and central nucleus.

The present study examined the relative contributions of the amygdaloid basolateral complex (ABL) and central nucleus (CN) to taste-potentiated odor aversion (TPOA) learning--an associative learning task that is dependent on information processing in two sensory modalities. In Experiment 1, rats with neurotoxic lesions of these systems were trained on the TPOA task by presenting a compound taste-odor conditioned stimulus, which was followed by LiCl administration. Results showed that ABL damage caused an impairment in potentiated odor aversion learning but no deficit in the conditioned taste aversion. In contrast, rats with CN damage learned both tasks. Experiment 2 examined the effects of ABL damage on TPOA and odor discrimination learning. The odor discrimination procedure used a place preference task to demonstrate normal processing of olfactory information. Results indicated that although ABL-lesioned animals were impaired on TPOA, there was no deficit in odor discrimination learning.

Animals↗

PubMed2003

Learning and discrimination of audiovisual events in human infants: the hierarchical relation between intersensory temporal synchrony and rhythmic pattern cues.

This study examined 4- to 10-month-old infants' perception of audio-visual (A-V) temporal synchrony cues in the presence or absence of rhythmic pattern cues. Experiment 1 established that infants of all ages could successfully discriminate between two different audiovisual rhythmic events. Experiment 2 showed that only 10-month-old infants detected a desynchronization of the auditory and visual components of a rhythmical event. Experiment 3 showed that 4- to 8-month-old infants could detect A-V desynchronization but only when the audiovisual event was nonrhythmic. These results show that initially in development infants attend to the overall temporal structure of rhythmic audiovisual events but that later in development they become capable of perceiving the embedded intersensory temporal synchrony relations as well.

Association Learning↗

PubMed2001

Orientation discrimination independent of retinal matching by blowflies.

Blowflies, Phaenicia sericata, can be trained to discriminate in a learning paradigm in which one of the two visual cues is positively rewarded. Retinotopic matching of a learned visual image to the same retinal location from viewing to viewing has been hypothesized to underlie visual pattern learning and memory in insects. To address the theory of retinotopic matching, a detailed analysis was made of the flies' body orientations during learned discriminations between +45 degrees and -45 degrees gratings. Initial approaches to the positive rewarded visual cue did not originate from the same spatial location within the behavioral arena with respect to the visual cues; thus, individual flies approached the positive cue from a different vantage point from trial to trial. During initial approaches to the rewarded visual cue, the distributions of body angles with respect to the cue were different from trial to trial for each individual. These data suggest that Phaenicia sericata can learn a visual pattern with one eye region and later recognize the same pattern with another eye region. Thus, retinotopic matching is not necessary for the recognition of pattern orientation in the experimental paradigm used here. The average amount of head turning in the yaw plane was too small to compensate for the changes in body orientation exhibited by the flies. Flies view the visual patterns with distinct retinal regions from trial to trial during orientation discrimination.

Animals↗

PubMed1980

[Discrimination shift learning and dimensional dominance in mental retarded children (author's transl)].

Dimensional dominance (either form or color) among retarded and normal children was assessed prior to their being presented with reversal or nonreversal shift task. During the initial learning, the dominant dimension was either relevant or irrelevant to the solution. Both rate of criterion attainment during the initial learning and subsequent shift performance were related to dimensional dominance. If the dominant dimension was relevant, the retarded learned the task as fast as the normal; if the dominant dimension was irrelevant, the retardates learned it with more difficulty than the normals. This result was discussed in relation to the tendency of the retardates' towards being bound to one dimension and no switching to an other.

Child↗

PubMed1997

Color vision discrimination in the capuchin monkey Cebus apella: evidence for trichromaticity.

Primates display significant differences in color vision. The purpose of this study was to assess the ability of capuchin monkeys in discriminating chromatic and achromatic Munsell color chips through behavioral tests. The subjects were trained in a simple and reverse discrimination learning procedure. All subjects were capable of discriminations along five color categories investigated. The results are discussed in terms of the hypothesis of male dichromatism in New World monkeys, the role of color vision in adaptation to feeding ecology, as well as to aspects regarding primate evolution.

Animals↗

PubMedDate not supplied

Human central auditory plasticity associated with tone sequence learning.

We investigated learning-related changes in amplitude, scalp topography, and source localization of the mismatch negativity (MMN), a neurophysiological response correlated with auditory discrimination ability. Participants (n = 32) underwent two EEG recordings while they watched silent films and ignored auditory stimuli. Stimuli were a standard (probability = 85%) and two deviant (probability = 7.5% each for high [HD] and low [LD]) eight-tone sequences that differed in the frequency of one tone. Between recordings, subjects practiced discriminating the HD or LD from the standard for 6 min. The amplitude of the LD MMN increased significantly across recordings in both groups, whereas the amplitude of the HD MMN did not. The LD was easier to discriminate than was the HD. Thus, practicing either discrimination increased the MMN for the easier discrimination. Learning and changes in the LD MMN amplitude were highly correlated. Source localizations of event-related potentials (ERPs) to all stimuli revealed bilateral sources in superior temporal regions. Compared with the standard ERP, the LD ERP revealed a stronger source in the left superior temporal region in both recordings, whereas the right-sided source became stronger after learning. Consistent with prior studies of auditory plasticity in animals and humans, tone sequence learning induced rapid neurophysiological plasticity in the human central auditory system. The results also suggest that there is asymmetric hemispheric involvement in tone sequence discrimination learning and that discrimination difficulty influences the time course of learning-related neurophysiological changes.

Acoustic Stimulation↗

PubMed1975

Stimulus generalization following extra-dimensional training in educationally subnormal (severely) children.

The use of discrimination learning paradigms in the study of attentional transfer is discussed. The technique of go/no-go discrimination learning followed by stimulus generalization testing is contrasted with the more familiar simultaneous learning paradigm followed by a shift in the relevant cues. In the former paradigm the effect of training a discrimination on one dimension on the slope of the stimulus generalization gradient on an independent gradient dimension (extra-dimensional training) is assessed. A steepening of the gradient relative to appropriate control procedures is taken as evidence of positive attentional transfer. The relevance of the technique to the detailed study of attentional transfer in educationally subnormal (severely) (ESN(S)) children is considered. In Expt. I nine ESN(S) children were trained in a go/no-go discrimination involving stimuli differing in orientation, and were generalization tested on a dimension that was orthogonal, namely hue. Of the six subjects who learnt the discrimination five showed clear decremental gradients on the hue dimension. In contrast a Pseudo-Discrimination group (PD) of eight subjects matched to those in the TD group showed no gradients. These subjects were not trained in the orientation discrimination, but were reinforced for responding on 50 per cent of each of the S+ and S- stimulus presentations. They thus received equal exposure to, but no differential training on, the orientation dimension. An S+ only group of four subjects who received no exposure to the orientation stimuli showed no gradients when stimulus generalization testing on the hue continuum was carried out. The result is discussed in terms of transfer deriving from stimulus control by relational aspects of the stimuli; in terms of control by constant irrelevant stimuli; and in terms of the study of stimulus control in ESN(S) children. In Expt. II the influence of the codability of the colours on the location of the peak of the stimulus generalization gradients in the TD group is investigated.

Adolescent↗

PubMed1992

Problem-solving behaviour in apomorphine-susceptible and unsusceptible rats.

Pharmacogenetically selected apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats were trained in a discrimination learning paradigm. After the initial discrimination task was solved, reinforcement contingencies were reversed. No differences between APO-SUS and APO-UNSUS animals were found in the rate of learning. However, negative transfer from the initial discrimination to its reversal was less for the APO-SUS rats than for the APO-UNSUS rats. Moreover, the APO-SUS rats responded more to the relevant dimension (light) than the APO-UNSUS rats in the last 100 trials before solving the initial problem as well as the reversal. During overtraining on the first problem, APO-SUS animals responded less to an irrelevant dimension (position of the lever) than APO-UNSUS animals. In the first 100 trials of the reversal APO-SUS rats responded more to another irrelevant dimension (noise) than APO-UNSUS rats. The data show that APO-SUS and APO-UNSUS rats used the various dimensions (visual, auditory, and spatial) differently in the chosen discrimination learning paradigm. It is concluded that the interline differences found are the consequences of the interline differences in the dopaminergic activity of the ventral and dorsal striatum.

Acoustic Stimulation↗