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PubMed1996

Cognitive fatigue and complex decision making under prolonged isolation and confinement.

Cognitive fatigue and subjective state were assessed in four healthy subject (three males and one female), confined for a period of 60 days in a hyperbaric chamber stimulating a space station environment. They were required to carry out daily a working memory/decision-making test, simulating the management of the levels of contaminants present in a spacecraft atmosphere. Information about a set of contaminants is presented on a 'reference screen.' This has to be memorized, then used to make decisions about the need for corrective action across a sequence of four 'status screens.' Subjects may check back to the reference information at any time. A low error rate was emphasized in the instructions and training. In addition to error rate, performance was also measured in terms of the time taken to make decisions and checks of reference screens (decision time and check time). Subjective measures were also made of workload and environmental resources (personal control and support), levels of anxiety and fatigue before the task, and cognitive effort expended during the task. The search for decrements during the second half of the isolation period was complicated by evidence of a continued learning process during the first half, probably because of insufficient practice before isolation. Learning curves (negative exponential functions) were fitted to the data points for the first half of the isolation period, and residuals between predicted and observed data for the second four weeks were analyzed. All subjects showed increases in decision time and check time during the last weeks of isolation, with one subject also showing an increase in errors. Workload levels were reported as moderate, but varied across the four subjects, The same was true for resources. Anxiety was low and relatively stable over the entire 60-day period, but fatigue levels were elevated during the second half. This was particularly true for the two subjects who maintained the required low error rate. Effort was also quite stable, through it tended to follow changes in work demands and fatigue. Individual subjects are seen to adapt to the stress of prolonged isolation in different ways. Two subjects maintained low error rates under increasing subjective demands by additional cognitive effort and slowing of performance. The other two subjects exhibit more widespread decrement, including high error rates, without increase in subjective demands. The analysis of individual patterns of adaptation is recommended as a way of understanding and predicting the impact of isolation and confinement during spaceflights.

Adaptation, Psychological↗
PubMed2005

Comparison of the impact of melatonin on chronic ethanol-induced learning and memory impairment between young and aged rats.

Chronic alcohol exposure causes functional and structural changes in nervous system which have all been associated with learning and memory impairments. Furthermore, alcohol consumption has been shown to alter the pattern of neural cell adhesion molecules (NCAM) which are involved in memory processes. In the current work, we investigated the effects of melatonin on learning and memory deficits induced by alcohol exposure in young and aged rats. A group of young rats (3 months old) were administered ethanol for 45 days and half of them were co-treated with melatonin. Similar treatments were performed in the aged (19 months old) rats. Morris water maze test and passive avoidance task were used to assess cognitive performance. Lipid peroxidation (LPO) and glutathione (GSH) levels were determined to characterize the level of oxidative stress in the hippocampus and cortex. NCAM levels were determined by Western blotting in the hippocampal homogenates. There was a significant elevation in LPO levels and a reduction in GSH levels in aged and alcohol-exposed rats. Furthermore, both young and aged rats displayed some cognitive impairment when given with alcohol for 45 days. Co-administration of melatonin with ethanol significantly reduced LPO and elevated GSH levels while improving the learning and memory deficits induced by ethanol; the aged rats exhibited a greater response to melatonin supplementation. Moreover, melatonin modulated NCAM expression in hippocampus. Present findings indicate that exposure to ethanol induces learning and memory deficits probably by generating reactive oxygen species and downregulating NCAM 180 in hippocampus of aged rats. Melatonin improves learning and memory deficits and the behavioral responses of rats to melatonin supplementation are age dependent.

Aging↗
PubMed2004

Identification of humans using gait.

We propose a view-based approach to recognize humans from their gait. Two different image features have been considered: the width of the outer contour of the binarized silhouette of the walking person and the entire binary silhouette itself. To obtain the observation vector from the image features, we employ two different methods. In the first method, referred to as the indirect approach, the high-dimensional image feature is transformed to a lower dimensional space by generating what we call the frame to exemplar (FED) distance. The FED vector captures both structural and dynamic traits of each individual. For compact and effective gait representation and recognition, the gait information in the FED vector sequences is captured in a hidden Markov model (HMM). In the second method, referred to as the direct approach, we work with the feature vector directly (as opposed to computing the FED) and train an HMM. We estimate the HMM parameters (specifically the observation probability B) based on the distance between the exemplars and the image features. In this way, we avoid learning high-dimensional probability density functions. The statistical nature of the HMM lends overall robustness to representation and recognition. The performance of the methods is illustrated using several databases.

Algorithms↗
PubMed2004

Binary halftone image resolution increasing by decision tree learning.

This paper presents a new, accurate, and efficient technique to increase the spatial resolution of binary halftone images. It makes use of a machine learning process to automatically design a zoom operator starting from pairs of input-output sample images. To accurately zoom a halftone image, a large window and large sample images are required. Unfortunately, in this case, the execution time required by most of the previous techniques may be prohibitive. The new solution overcomes this difficulty by using decision tree (DT) learning. Original DT learning is modified to obtain a more efficient technique (WZDT learning). It is useful to know, a priori, sample complexity (the number of training samples needed to obtain, with probability 1 - delta, an operator with accuracy epsilon): we use the probably approximately correct (PAC) learning theory to compute the sample complexity. Since the PAC theory usually yields an overestimated sample complexity, statistical estimation is used to evaluate, a posteriori, a tight error bound. Statistical estimation is also used to choose an appropriate window and to show that DT learning has good inductive bias. The new technique is more accurate than a zooming method based on simple inverse halftoning techniques. The quality of the proposed solution is very close to the theoretical optimal obtainable quality for a neighborhood-based zooming process using the Hamming distance to quantify the error.

Algorithms↗
PubMed2006

The emergence of symmetry in a conditional discrimination task using different responses as propioceptive samples in pigeons.

In Experiment 1, 10 pigeons were exposed to a successive symbolic matching-to-sample procedure in which the sample was generated by the pigeons' own behavior. Each trial began with both response keys illuminated white, one being the "correct" key and the other the "incorrect" key. The pigeons had no way of discriminating which key was correct and which incorrect, since these roles were assigned on a random basis with the same probability of 0.5 for each key. A fixed ratio of five responses was required on the correct key. However, each time the pigeon pecked the incorrect key, the correct key response counter reset. Five consecutive pecks on the correct key was the only way to end this component, and switch off both key lights. Two seconds later, these same keys were illuminated again, one green and the other red (comparison stimuli). Now, if the correct white key had been on the left, a peck at one color produced food, and if the correct white key had been on the right, a peck at the other color produced food. When the pigeons had learned this discrimination, they were exposed to several symmetry tests (simultaneous presentations of both keys illuminated the same color-i.e., both red or both green), in order to interchange the sample with the comparison stimuli. In Experiment 2, the importance of requiring discrimination between the samples and between the comparisons was analyzed. In Experiment 3, we compared the results of Experiment 1 with a slightly different experiment, which resulted in discrimination of key position, an exteroceptive stimulus. The results showed that symmetry emerged only when different responses were used as samples.

Animals↗
PubMed1994

Aging and illusory correlation in judgments of co-occurrence.

This study examined the influence of aging on illusory correlation in judgments of co-occurrence. Older and younger Ss judged the probability of co-occurrence for events associated with preexisting expectancies after receiving nonsalient or salient information about the true probabilities of co-occurrence of the events. Results showed that when current information on event co-occurrence was not salient, preexisting expectancies strongly influenced the judgments of both younger and older Ss. However, when this information was salient, younger Ss' judgments reflected more accurate adjustment to the probabilistic relationships in the information than did older Ss' judgments. This age difference may be related to changes in memory processes that accompany increasing age and to differences in judgment processes necessitated by these changes.

Adolescent↗
PubMed2004

Hippocampal gray matter reduction associates with memory deficits in adolescents with history of prematurity.

Using optimized voxel-based morphometry (VBM), we compared the relationship between hippocampal and thalamic gray matter loss and memory impairment in 22 adolescents with history of prematurity (HP) and 22 normal controls. We observed significant differences between groups in verbal learning and verbal recognition, but not in visual memory. VBM analysis showed significant left hippocampal and bilateral thalamic reductions in HP subjects. Using stereological methods, we also observed a reduction in hippocampal volume, with left posterior predominance. We found correlations between left hippocampal gray matter reductions (assessed by VBM) and verbal memory (learning and percentage of memory loss) in the premature group. The stereological analysis showed a correlation between verbal learning and the left posterior hippocampus. Our results suggest that left hippocampal tissue loss may be responsible for memory impairment and is probably related to the learning disabilities that HP subjects present during schooling.

Adolescent↗
PubMedDate not supplied

[Psychotherapy in the penitentiary environment: problems and perspectives].

While recent studies suggest that psychotherapy has little impact on recidivism, these studies are far from conclusive and they tell us little about the ultimate value of psychotherapy in the correctional setting. Aside from the issue of recidivism, psychotherapy in prison has many practical and humanistic advantages. The incarcerated offender may seek psychotherapy because of motivations that are totally unrelated to the issue of release. It is useful to consider psychotherapy of incarcerated offenders in terms of the relevance of helping factors that are critical to all types of psychotherapy. Some of these factors have less therapeutic influence in the prison setting than in the free world. Certain factors such as tension reduction and the learning of new behaviors probably have a greater therapeutic affect in the prison setting.

Criminal Psychology↗
PubMed2000

Schizophrenics know more than they can tell: probabilistic classification learning in schizophrenia.

BACKGROUND: Previous studies have demonstrated impaired explicit and preserved implicit memory functions in schizophrenia. However, it is less clear whether schizophrenics can learn complex information (e.g. probabilistic stimulus response associations) with or without access for conscious recollection. In this study we applied a classification learning task to assess explicit and implicit processes concurrently. METHODS: Two test procedures were administered to 40 schizophrenic subjects and 20 healthy volunteers: a probabilistic classification learning (PCL) task to evaluate implicit memory functions; and a category cue recognition test to investigate the explicit memory system. The PCL task included feedback guided category learning of geometrical shapes. These shapes were called category cues, predicting class membership with certain probabilities. The gradual increase of categorization performance during the feedback learning was a potentially implicit process, whereas the subsequent recognition of category cues required explicit memory functions. RESULTS: The schizophrenic patients improved their categorization performance to a similar extent to the controls, but they failed to recognize the category cues. Memory performances were independent of the positive and negative symptoms. CONCLUSIONS: Patients with schizophrenia were able to establish representations of complex categories, but these remained unconscious. This is consistent with earlier reports, suggesting damaged explicit and spared implicit memory in schizophrenia.

Adult↗
PubMed1987

Toward a universal law of generalization for psychological science.

A psychological space is established for any set of stimuli by determining metric distances between the stimuli such that the probability that a response learned to any stimulus will generalize to any other is an invariant monotonic function of the distance between them. To a good approximation, this probability of generalization (i) decays exponentially with this distance, and (ii) does so in accordance with one of two metrics, depending on the relation between the dimensions along which the stimuli vary. These empirical regularities are mathematically derivable from universal principles of natural kinds and probabilistic geometry that may, through evolutionary internalization, tend to govern the behaviors of all sentient organisms.

Behavior↗
PubMed1999

[Model trial: use and evaluation of a problem-oriented learning program in internal medicine].

BACKGROUND: Problem-based training is a new approach in medical education. It is in particular essential that students work actively with authentic medical cases. Modern software is appropriate for developing interactive case-based training systems and the use in teaching environments. This method is still rarely integrated within medical curricula. METHOD: In an educational trial with 287 students the conceptual background, feasibility and evaluation are discussed. The learning program CASUS was used to present the case of a macroprolactinoma for interactive training. A questionnaire with a return rate of 78% was used for evaluation. RESULTS: 96% of the students had no problems in learning how to handle and use the program. A major problem was to focus the contents of the program exactly to the students' needs. The students' judgement was independent of the individual computer skills. 82% of the students would like to use the program in the future. CONCLUSION: Case-based and computer-assisted learning increases motivation and probably improves the quality in medical education. Controlled trials have to be implemented in future to show the effectiveness and the long-term output of these learning systems.

Computer-Assisted Instruction↗
PubMed2000

[How can one improve the understanding and communication of the importance of medical test results?].

Interpreting medical test results demands statistical reasoning on the part of doctors: How great is the probability of falsely diagnosing an illness based on a positive test result? This probability can be determined with the assistance of Bayes's Rule. Several studies show, however, that doctors often experience problems with these kinds of Bayesian inferences. We demonstrate that doctors' judgments can be considerably improved when numerical information is presented in a form easily accessible to the ways humans process information. This is not the case with the utilization of applied probabilities that has become customary, but is the case when the problem is presented in terms of "natural frequencies" that result from the counting of observed isolated cases in a natural environment. In a series of studies, we varied the representation format of the relevant statistical information. If the information was not presented in the form of probabilities or percentages but simply in natural frequencies, medical experts, as well as laymen, were able to improve their judgments significantly. And dealing with probabilities and percentages can also be easily learned: Two training programs, which showed how probabilities can be translated into natural frequencies, placed the participants in the position of being able to obtain very good results when solving these tasks. Finally, we discuss the impact of a comprehensible risk and utility communication on the doctor-patient relationship.

Bayes Theorem↗
PubMedDate not supplied

The influence of the probability of random performance of a reaction to be developed on the rate of formation of an instrumental reflex.

An instrumental defense reflex of pedal pressing during the action of a conditional signal (light) was developed in rats. The process of learning given a varying probability of the random performance of the instrumental reaction, p(a), which depends in particular on the duration of the intervals between the action of the conditional stimulus, was studied. It was shown that the rate of formation of a conditioned reflex is higher for p(a) = 0.25 than for p(a) = 0.05. The rate of formation of the conditioned reflex also depends on the frequency of the positive reinforcement of the correct reactions (from 50 to 100%). With a high p(a), the rate of formation of the reflex in question does not depend on the frequency of reinforcement of the positive responses; a feedback relationship is observed in the case of a low p(a). The hypothesis is advanced that not only does the behavior itself change the probability of contact with the external object but the original (a priori) probability substantially influences the formation of the behavior as well.

Animals↗
PubMed1993

Lack of strain differences in spatial learning among seizure-prone and seizure-resistant mice.

Learning rates were examined in the following inbred mice strains: DBA/2, C3H/He, C57B1/6J, E1, and ddY. DBA/2 mice become susceptible to audiogenic seizures after 2-3 weeks of age and E1 mice have generalized seizures in response to handling after 3 months of age, but the remaining three strains do not develop seizures. In this study, mice from all five strains underwent 32 training trials in a Morris water maze at 7-9 weeks of age. The seizure-prone DBA/2 and E1 mice, along with the nonepileptic ddY and C57B1/6J mice, exhibited learning at similar rates, but the nonepileptic C3H/He mice were unable to learn the water maze task, probably due to visual difficulties. In the C57B1/6J strain only, female mice learned the task significantly faster than males. There was no difference in the learning rate between the E1 strain and its parent ddY strain, or any correlation between spatial learning ability and kindling rates in these strains.

Animals↗