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PubMed1978

The effect of visual deprivation in the rat on transfer effects after form discrimination training.

In 3 experiments the performances of light-reared (LR) and dark-reared (DR) 90-day-old rats were compared on a variety of transfer tests following acquisition of 3 discriminations involving patterns of small squares (dots). Though no significant difference due to rearing condition was found in acquisition of those discriminations consisting of single lines of dots in various orientations, transfer tests did reveal subtle differences in the way LR and DR rats analyze contour information. Significant differences due to rearing were also observed on the acquisition of a complex dot pattern (gradient vs X) and, in spite of overtraining, on subsequent stimulus equivalence tests. Anomalous transfer effects were not observed in any of these test situations.

Animals↗
PubMed1975

Associative recall and formation of stable modes of activity in neural network models.

Models of neural networks with recurrent inhibition are studied, as well as one model which also includes recurrent excitation. The models are intended as possible descriptions of the cerebral cortex. Each network model is composed of neuron models called pyramidal cells and stellate cells in accordance with the names of two types of cells in the cortex. Inputs and outputs of the network are connected to the pyramidal cells while feedback is provided by the stellate cells. Connections within the network are random. During a learning phase the pyramidal cell excitatory synapses become facilitated according to a two-conditional facilitation rule. This is the basis of the model's ability for associative learning. The associative retrieval of information can be studied during a subsequent association phase. This has been done by simulation on a digital computer. It was shown that all of the models considered can be designed to perform a so-called decision-making function. This means that if the associating input pattern is similar to several patterns which occurred during learning the model can decide which similarity is greatest by responding with the appropriate associated pattern. The model also including recurrent excitation differs from the simpler models in that it can become stabilized in so-called stable modes of activity which are self-sustaining and remain even after the input has been turned off. Normally, only one stable mode can be active at a time. However, through careful choice of construction parameters it was possible to obtain a model in which a maximum of two stable modes could be activated independently of each other. Physiological and psychological interpretations are discussed and so are the limitations of the models, which are evident in certain situations.

Cerebral Cortex↗
PubMed1976

Piracetam-induced facilitation of interhemispheric transfer of visual information in rats.

The effect of Piracetam (UCB 6215, 2-pyrrolidoneacetamide) on learning mediated by transcommissural information flow was studied in hooded rats. Acquisition of monocular pattern discrimination was faster in drug-treated rats (100 mg/kg, 30 min before training) than in untreated controls. Subsequent relearning with one hemisphere functionally eliminated by cortical spreading depression showed that the strength of the primary engram formed under Piracetam in the hemisphere contralateral to the trained eye remained unaffected but that the secondary trace (in the ipsilateral hemisphere) was considerably improved and almost equalled the primary one (savings increased from 20-30% to 50-60%). Learning with uncrossed optic fibers was unaffected by the drug. Interhemispheric transfer of lateralized visual engrams acquired during functional hemidecortication was facilitated by Piracetam administration preceding the five transfer trials performed with the untrained eye open (imperative transfer). Piracetam was ineffective when the trained eye was open during transfer trials (facultative transfer). After a visual engram had been lateralized by 5 days of monocular overtraining, Piracetam facilitated formation of the secondary engram induced by 3 interocular transfer trials. It is concluded that Piracetam enhances transcommissural encoding mechanisms activated in the initial stage of monocular learning and in some forms of interhemispheric transfer, but does not affect the transcommissural readout. This effect is interpreted as a special case of the Piracetam-induced facilitation of the phylogenetically old mechanisms of redundant information storage which improve liminal or subnormal learning.

Animals↗
PubMed1977

Reducing stimulus overselectivity in autistic children.

It has been repeatedly reported that when presented with a discrimination task involving multiple cues, autistic children, as compared to normal children, tend to respond on the basis of only a restricted portion of the component cues. This phenomenon has been called "stimulus overselectivity" and has been implicated as a possible basis for some of the pronounced behavioral deficits charactertistic of autism. Examination of the results of several previous studies suggests that the overselectivity effect might be reduced with repeated exposure to testing. However, since the previous studies were not designed to test this hypothesis, no conclusions were drawn regarding variables influencing the reduction of the overselectivity phenomenon. The present investigation was therefore conducted to determine if stimulus overselectivity in autistic children is changed as a function of repeated exposure to testing. Nineteen autistic children were trained on a discrimination task with a cue complex composed of two visual cues. After the children reached criterion on the task, they were exposed to a testing phase with probe trials where the cue components were presented singly. The results indicated that 16 of the children initially showed overselectivity and 3 responded to both cues. Of the 16 children who showed overselectivity, 13 decreased their level of overselectivity with continued testing. These results are discussed in relation to variables in the testing procedure itself and to the literature on selective attention.

Attention↗
PubMed1976

Overselectivity, developmental level, and overtraining in autistic and normal children.

Thirteen autistic children were compared to 13 normal children matched to them in mental age, on performance of a visual discrimination task. Form, color, and size were relevant and redundant cues. The groups did not differ significantly in mean trials to reach criterion or in breadth of learning, and both groups increased their breadth of learning after 50 trials of overtraining. Form was preferred to color and size by both autistic and normal children. Within each group, rank on mental age was highly correlated with rank in breadth of learning. Verbal and nonverbal autistic children did not differ in breadth of learning or in dimensional preference. Even nonverbal autistics equaled the performance of their normal controls. Our results suggest that overselective attention is better understood as part of a general developmental lag in cognition in autistic children than as a specific deficit underlying psychotic behavior.

Attention↗
PubMed1979

The effects of schedule of reinforcement on stimulus overselectivity in autistic children.

Recent research demonstrated that when autistic children are presented a discrimination task with multiple cues, they typically respond to an abnormally limited number, usually one, of the available cues. This phenomenon, termed "stimulus overselectivity," has been implicated as a possible basis for many of the behavioral deficits characteristic of autism. The present investigation was conducted to systemically analyze the effects of changing the schedules of reinforcement during discrimination training on subsequent stimulus overselectivity. Twelve autistic children were taught a discrimination involving multiple visual cues, with a CRF schedule of reinforcement. The children were then overtrained on either the same (CRF) schedule or on a partial (VR:3) reinforcement schedule. Subsequent overselectivity on single-cue test trials was then assessed. Results suggested that significantly less overselectivity occurred when the children were presented with the VR:3 reinforcement schedule during overtraining. These results are discussed in terms of variables influencing overselectivity and in terms of implications for designing treatment procedures for autistic children.

Adolescent↗
PubMed1985

Parental ratings of treatments of self-injurious behavior.

This study examined (a) how parents of autistic children, parents of other handicapped children, and parents of nonhandicapped children rate, as a whole, acceptability of time-out, differential reinforcement, overcorrection, and shock as treatments for self-injurious behavior, and (b) whether these parents show differences, as groups, in ratings of these treatments. On the Treatment Evaluation Inventory, all groups consistently rated differential reinforcement, time-out, and overcorrection as acceptable and shock as unacceptable. Differential reinforcement was consistently rated as the most acceptable, but the groups differed in ratings of acceptability of other treatments. On the Semantic Differential, ratings of differential reinforcement, overcorrection, and time-out did not differ. However, shock was consistently rated as the most potent and active of treatments as well as the most unacceptable. The implications of these findings for treatment of autistic and other handicapped children are discussed.

Adolescent↗
PubMed1985

Operational specificity: implications for field-based replications.

This paper discusses problems with field-based replications of behavioral interventions. Major issues identified include operational specificity, mislabelling of procedures, relative contributions of components in multi-faceted treatment packages, and impediments to systematic replication. The paper concludes with a call for increased operational specificity in the reporting of both baseline and intervention procedures on the part of researchers and clinicians responsible for dissemination.

Adolescent↗
PubMed1985

Treatment of constipation-caused encopresis by a negative reinforcement procedure.

During a baseline condition soiling and the cumulative number of bowel movements of a child suffering from retentive encopresis were recorded. Following this, a DRO (differential reinforcement of other behavior) alone, a DRO plus overcorrection procedure, and a negative reinforcement procedure were each evaluated using a reversal design. The negative reinforcement procedure, which involved having the child sit on the toilet three times a day for increasing time periods if no bowel movement occurred, suppressed soiling and led to regular unprompted daily bowel movements in a very brief period of time. The DRO alone and DRO plus overcorrection conditions produced only a small decline in soiling.

Behavior Therapy↗
PubMed1985

Comprehensive treatment of chronic fire setting in a severely disordered boy.

A comprehensive, multidimensional treatment strategy was designed for a severely behaviorally disordered 10-year-old boy with a 7-year history of setting fires. The study replicates a previous study designed to suppress fire setting, teach appropriate substitute behavior and increase awareness of the consequences of fire setting. Three additional components were added to the original treatment program: relaxation training, a response cost for fire setting, and a visit to a hospital burn unit (overt sensitization). Follow-up data 1 year later indicate that treatment was successful in extinguishing all fire-setting behaviors. The additional treatment components presented in this paper may add to the efficacy and sustained durability of treatment gains in difficult, low frequency fire setting behavior.

Behavior Therapy↗
PubMed1975

Intermanual transfer in the monkey as a function of amount of callosal sparing.

The effects of commissure section, task difficulty and overtraining on the intermanual transfer of tactile learning have been examined. Twenty-one rhesus monkeys were allocated to 4 groups. One group was subjected to complete transection of the corpus callosum, massa intermedia and posterior commissure. Some of this group also sustained a cerebellar section. A second group received a similar division of the commissures but with part of the posterior body of the corpus callosum left intact. A third group received similar division of the commissures but with the posterior commissure left intact. The fourth group formed an unoperated control group. Animals with only the posterior commissure left intact showed little or no transfer. Animals with partial callosal lesions showed significantly greater transfer than animals with total transections, but were impaired relative to the unoperated controls. Estimates have been made of the number of callosal fibres left intact in the animals with partial callosal lesions. These estimates have been correlated with transfer. The correlation was significant on only one task. Neither task difficulty nor overtraining were found to affect transfer significantly. The comparison of transfer of the submodalities of size and roughness was inconclusive.

Animals↗
PubMed1979

An autoradiographic study of the chick brain after imprinting.

On the first day after hatching domestic chicks were exposed to an imprinting stimulus, a horizontal yellow slit of light moving upwards in a window and presented at a rate of 4 slits/sec. Chicks were exposed for either 45 min (undertrained) or 180 min (overtrained) on the first day of hatching (60 or 240 min in the case of 1 pair). On the second day all birds were exposed for a further 63 min. Twenty birds were matched in pairs and each chick received 1.1 muCi [14C]uracil/g body weight injected into the heart region before exposure on day 2. At 150 min after the injection the chicks were decapitated and serial coronal sections of their brains cut; alternate pairs of sections were prepared for autoradiography. The optical density for a number of major anatomical regions was measured. The measurements for each region were averaged over congruent to 0.6 mm 'slabs' of brain and expressed as a percentage of the mean of all measurements for that brain. Standardized mean optical density was significantly greater in undertrained chicks than in overtrained chicks in a part of the medial region of hyperstriatum ventrale (MHV) which extended across two adjacent slabs. The slabs were slightly posterior to the mid-point between anterior and posterior poles of the brain. In the next two, adjacent, anterior slabs the variances for MHV were significantly greater in undertrained chicks than in overtrained chicks. There were no other significant differences between brain regions. Taken together with previous studies these results suggest that the intermediate and medial part of hyperstriatum ventrale is intimately linked with the imprinting process.

Animals↗
PubMed1987

Posterior cingulate cortical lesions eliminate learning-related unit activity in the anterior cingulate cortex.

The frequency of multi-unit neuronal firing in response to tonal conditional stimuli increases, and the neuronal responses become discriminative in character, in the anterior and posterior subfields of the cingulate cortex (Brodmann's Area 24 and 29, respectively) during the course of discriminative avoidance conditioning in rabbits. Bilateral electrolytic lesions of the dorsal subicular complex eliminated the training-induced excitatory response in both cortical subfields, suggesting that subiculocortical projection fibers are essential for this effect. Yet, available data indicate that the subicular projection reaches only Area 29, not Area 24. Here we test the hypothesis that the subicular influence attains Area 24 via a synaptic relay in Area 29. The results showed in keeping with the hypothesis, that bilateral aspirative or electrolytic lesions in Area 29 eliminated the training-induced neuronal responses in Area 24. As in the case of subicular lesions, the Area 29 lesions increased the amplitude of the macropotentials in Area 24. These results are discussed in relation to a model of the interactions of the cingulate cortex, hippocampus and the limbic thalamic nuclei during learning.

Animals↗
PubMed1991

Hippocampal CA1 evoked response and radial 8-arm maze performance after hippocampal kindling.

Rats with chronically implanted electrodes in the hippocampal CA1 region were trained in the open radial 8-arm maze and then subjected to kindling (afterdischarges, ADs) or 0.17 Hz low-frequency stimulations (LFSs) as controls. Partial kindling (21 ADs) induced a general increase of AD threshold but no motor convulsions. The commissurally evoked average evoked potentials (AEPs) in CA1 were enhanced above the pre-AD baseline or the AEPs in LFS control rats at 1 day after the 1st, 6th, 11th and 16th AD and for at least 25 days after 21 ADs. Similarly, maze performance was significantly worse in kindled than LFS rats for about 4 weeks after 21 ADs/LFSs. The study confirms the long-lasting behavioral effect of partial kindling and suggests that synaptic enhancement may underlie the behavioral disruption.

Animals↗