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PubMed1976

Teratopsychogenetic effects apparently produced by nonphysiological neurotransmitter concentrations during brain differentiation.

In male rats treated with pargyline, reserpine or pyridostigmine during neonatal life significant permanent changes of sexual behaviour and conditioned learning behaviour were observed in juvenile and/or adult life. Male sexual activity and learning capacity were permanently decreased in neonatally pargyline- or reserpine-treated animals, but permanently increased in neonatally pyridostigmine-treated rats. These findings suggest that nonphysiological concentrations and/or turnover rates of neurotransmitters, if produced during a critical period of brain differentiation, are able to induce lifelond effective behavioural changes, i.e. teratopsychogenetic effects.

Animals↗
PubMed1985

Simulating conditions of learned helplessness: the effects of interventions and attributions.

We report 2 experiments that assess factors potentially responsible for a proactive interference with the sensitivity of a mother's response to infant signals. Using a version of the "learned helplessness" paradigm, mothers' performance on a solvable task was assessed following pretreatments that involved exposure to an infant cry but that differed in the mothers' ability to exert control over the termination of the cry. Each experiment explored the role of varying attributions made by a mother in the development of, or the reversal of, the helplessness phenomenon. The first experiment addressed the question of whether a specific intervention (i.e., providing the mother an attribution for failure) can reduce the debilitating effect of prior experience with failure. The results indicated that the debilitating effects associated with previous failure were reversed for the 16 mothers assigned to the intervention group. 40 mothers participated in the second experiment, which varied attributions assigned to an identical cry stimulus (i.e., the cry was produced by an "easy" vs. a "difficult" infant). This experiment assessed the effect of varying attributions on the mothers' ability to terminate the cry. We found that mothers pretreated with inescapable cries and those receiving the experimental manipulation of attributing the cry to a "difficult" infant showed debilitated performance in stopping the cry when given the opportunity. We propose that models based on learned helplessness theory have value in the study of caregiver-infant relationships, in particular, caregivers' perceived and objective effectiveness in responding to an infant's signals.

Adult↗
PubMed1995

Impact of chronic undernutrition on higher mental functions in Indian boys aged 10-12 years.

Undernourished rural children 10-12 years of age demonstrated the following, when compared to normal nourished children: (i) a relative deficit of memory quotients assessed by the Wechsler memory scale; (ii) lower scores for abilities related to personal and current information, orientation, mental control, logical memory, digit span, visual reproduction and associative learning; (iii) impaired set formation and flexibility in attention as assessed by the card sorting test; and (iv) impairment in conditional learning on maze and conditional associative learning tests. The performance on the finger dexterity test for fine motor coordination was not affected in undernourished children.

Attention↗
PubMed2005

Attentional selection and action selection in the ventral and orbital prefrontal cortex.

Different accounts of the ventral and orbital prefrontal cortex (PFv+o) have emphasized either its role in learning conditional rules for action selection or the attentional selection of behaviorally relevant stimuli. Although the accounts are not mutually exclusive, it is possible that the involvement of PFv+o in conditional action selection is a consequence of its role in selecting relevant stimuli or that its involvement in attentional selection is a consequence of the conditional rules present in many attentional paradigms. Five macaques learned a conditional action-selection task in which the difficulty of identifying the stimulus relevant for guiding action selection was varied in a simple manner by either altering its distance from the action or presenting additional distracting stimuli. Simply increasing the spatial separation between the instructing stimulus led to slower responses. Experiment 1 showed that bilateral PFv+o lesions impaired conditional action selection even when attentional demands were kept to a minimum, but there was evidence that the impairment was exacerbated by manipulating stimulus selection difficulty. Experiment 2 confirmed the importance of PFv+o for conditional action selection even when stimulus selection difficulty was minimal. Experiments 3 and 4 demonstrated that the action-selection impairment was significantly increased by making identification of the behaviorally relevant stimulus difficult. PFv+o is central to the use of conditional rules when selecting courses of action, but conditional rules are also represented in premotor and striatal regions. A special contribution of PFv+o may be initial selection of behaviorally relevant stimuli.

Animals↗
PubMed1992

Indomethacin and sodium carbonate effects on conditioned fever and NK cell activity.

The augmentation of natural killer (NK) cell activity and elevation of body temperature (fever) can both be conditioned using camphor odor as the conditioned stimulus (CS) and poly I:C as the unconditioned stimulus (US). While both responses can be conditioned in parallel fashion as shown previously, our results indicate the conditioned learning of these responses may not follow along a common path. We found that injection of a 1% solution of sodium carbonate was able to consistently block the CS/US learning of the NK cell response but did not block conditioning of the fever response. In contrary fashion, mice treated with indomethacin (which inhibits prostaglandin-induced fever) dissolved in the sodium carbonate solution did not learn in consistent fashion the fever response. However, indomethacin-treated animals were able to recall the NK cell response. These results support the view that although the same mediator, IFN-beta, is responsible for the conditioned learning of the NK cell and fever responses both the learning and recall of the responses are initiated along separate pathways.

Animals↗
PubMedDate not supplied

Extracting the principal behavior of a probabilistic supervisor through neural networks ensemble.

In this paper, we propose a model of a neural network ensemble that can be trained with a supervisor having two kinds of input-output functions where the occurrence probability of each function is not even. This condition can be likened to a learning condition, in which the learning data are hampered by noise. In this case, the neural network has the impression that the learning supervisor (object) has a probabilistic behavior in which the supervisor generates correct learning data most of the time but occasionally generates erroneous ones. The objective is to train the neural network to approximate the greatest distributed input-output relation, which can be considered to be the principal nature of the supervisor, so that we can obtain a neural network that is able, to some extent, to suppress the ill effect of erroneous data encountered during the learning process.

Algorithms↗
PubMed2006

Which processes are involved in cognitive procedural learning?

Procedural memory is characterised by a relative resistance to pathology, making its assessment of the utmost importance. However, few studies have looked at the cognitive processes involved in cognitive procedural learning. In an initial experiment, we studied the role of different cognitive functions in massed cognitive procedural learning. Our results confirmed the existence of three separate learning phases and, for the first time, demonstrated the involvement of episodic memory and executive functions in the first learning phase. In a second experiment, we studied the effect of distributed learning conditions on the dynamics of procedural learning. This second study confirmed our results but showed that these conditions slow down the process of cognitive procedural learning. Our overall findings call into question the status of functionally autonomous memory system that is currently allotted to procedural memory, and suggest that the role of nonprocedural cognitive components should be taken into account in patient rehabilitation.

Adolescent↗
PubMed1991

The effects of occipital ablation on a conditioned visual avoidance learning task in young and old rats.

Previous data indicate that learning of a conditioned visual avoidance task following simultaneous complete bilateral occipital ablations is affected by the age of the organism as well as the postoperative recovery period. The present study investigated the performance of the avoidance task, following complete occipital ablations, in young and older rats given two different recovery intervals. Young rats given 10 days to recover performed more poorly than the young control animals; given 20 days to recover, young rats performed comparable to controls. Older rats given 10 days to recover performed significantly better than the controls; given 20 days to recover, older rats did not show a decrease in performance. The present finding is consistent with previous data which show that the occipital cortex exerted an inhibitory effect on the learning ability of the avoidance task in older rats, which, upon removal, enhanced the performance of these rats on the task.

Aging↗
PubMed1987

Rats with lesions in anteromedial extrastriate cortex fail to learn a visuosomatic conditional response.

The involvement of rat anteromedial extrastriate cortex (area AM, in the anterior portion of area 18b) in the integration of visual and somatic cues was assessed behaviorally. Following restricted bilateral lesions of selected cortical regions, rats were tested on their ability to retain or relearn a conditional visuosomatic discrimination task learned prior to surgery. Two compound, visuosomatic stimuli were used: white or black associated with either one of two degrees of roughness. The use of a guided-response procedure was essential for rats to learn this difficult conditional bimodal task. None of the 6 rats with lesions aimed at area AM retained the habit postoperatively. Four of these rats were incapable of relearning the task after 3 postoperative training series, and they had either extensive lesions of area AM or relatively small, symmetric damage of anterior portions of AM. The remaining two rats with lesions in area AM were able to relearn the task in the second postoperative training series, and their lesions either were restricted to posteromedial aspects of area AM or they involved asymmetric loci in anterior area AM. In contrast to rats with lesions of area AM, rats with lesions in visual cortex in areas 17 and 18a, or in auditory cortex in area 41, were able either to retain the task or to relearn in the first postoperative training series. These results indicate that the integrity of area AM appears necessary for rats to discriminate between pairs of compound stimuli that differ in brightness and roughness. The behavioural data point to the notion that this area might be involved in the integration of these types of visual and somatic stimuli. In addition, our finding that performance was largely unimpaired following extensive lesions of lateral extrastriate area supports previous reports indicating that medial and lateral extrastriate visual areas differ in function.

Animals↗
PubMed2005

Associative change in connectionist networks: an addendum.

The results of a recent study have provided direct support for the suggestion that conditional learning in rats is best characterized by a 3-layer connectionist network (M. J. Allman, J. Ward-Robinson, & R. C. Honey, 2004). In the 2 experiments reported here, rats were used to investigate the nature of the changes that occur when a stimulus compound is presented, whose components activate hidden units associated with food and no food, and either food or no food is presented. The results of both experiments, while controlling for the possible contribution of associations between these hidden units (within-layer links), provide evidence that the distribution of associative change between units in the hidden layer that are activated by the stimulus compound and those in the output layer (between-layer links) are unequal. They also indicate that associative change is more marked on trials on which no food was presented than on trials on which food was presented.

Analysis of Variance↗
PubMed1994

The effects of learning strategy instruction on the completion of job applications by students with learning disabilities.

The purpose of this study was to assess the effects of learning strategy instruction on the completion of job applications by students identified as learning disabled. Thirty-three students (average age 15 years 6 months) were randomly assigned by grade and gender to one of two experimental conditions: learning strategy instruction or traditional instruction. The result was 16 students (10 boys and 6 girls) being placed under the learning strategy instruction condition and 17 students (10 boys and 7 girls) being placed under the traditional instruction condition. Results indicated that in addition to statistically significant lower numbers of information omissions and information location errors, holistic ratings of the overall neatness of the job applications were significantly higher for those students under the learning strategy instruction condition. In addition to these positive changes in the performance measures, social validity data suggest that students under the learning strategy condition would be more likely to receive an invitation for a job interview. The findings and future research needs are discussed.

Adolescent↗
PubMed2004

Human orbitofrontal cortex mediates extinction learning while accessing conditioned representations of value.

In extinction, an animal learns that a previously conditioned stimulus (CS+) no longer predicts delivery of a salient reinforcer (unconditioned stimulus, UCS). Rodent studies indicate that extinction relies on amygdala-prefrontal interactions and involves formation of memories that inhibit, without actually erasing, the original conditioning trace. Whether extinction learning in humans follows similar neurobiological principles is unknown. We used functional magnetic resonance imaging to measure human brain activity evoked during olfactory aversive conditioning and extinction learning. Neural responses in orbitofrontal cortex and amygdala were preferentially enhanced during extinction, suggesting potential cross-species preservation of learning mechanisms that oppose conditioning. Moreover, by manipulating UCS aversiveness via reinforcer inflation, we showed that a CS+ retains access to representations of UCS value in distinct regions of ventral prefrontal cortex, even as extinction proceeds.

Adolescent↗