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PubMed1998

Synchrony effects in inhibitory control over thought and action.

Two experiments explore whether synchrony between peak circadian arousal periods and time of testing influences inhibitory efficiency for younger and older adults. Experiment 1 assesses inhibitory control over no-longer-relevant thoughts, and Experiment 2 assesses control over unwanted but strong responses, as well as performance on neuropsychological tasks that index frontal function. Inhibitory control is greatest at optimal times for both age groups and is generally greater for younger than for older adults. Performance on 2 neuropsychological measures (Stroop and Trails) also changes over the day, at least for older adults, and is correlated with inhibitory indexes, suggesting that for older adults changes in inhibition may be mediated by circadian variations in frontal functioning. By contrast, access to well-learned responses is not vulnerable to synchrony or age effects.

Adolescent↗

PubMed1985

Angiotensin converting enzyme inhibition. Unique and effective therapy for hypertension and congestive heart failure.

Major developments in the use of angiotensin converting enzyme (ACE) inhibition for the treatment of hypertension and congestive heart failure have occurred since the discovery of captopril in June 1975. Early in the past decade, this oral ACE inhibitor was restricted to refractory and severe cases of hypertension. By July 1985, the Food and Drug Administration approved its use not only for all degrees of hypertension but also for the initial treatment of hypertensive patients with uncomplicated disease. New information has confirmed the effectiveness of twice-daily administration (which favorably influences compliance) and the lack of a need to monitor blood or urine levels to assure safety. The renin-mediated and non-renin-mediated mechanisms of action of captopril-induced ACE inhibition have been fully delineated, as has its side effect profile, which does not include various CNS, sympathetic reflex, and metabolic side effects seen with other antihypertensive agents. As the first vasodilator to prove its efficacy in the acute and chronic treatment of congestive heart failure to the FDA, captopril is now widely used throughout the United States. ACE inhibition reduces symptoms, enhances exercise capacity, and favorably affects sodium, water, and potassium homeostasis in patients with heart failure. Also, recent but as yet unconfirmed evidence suggests that ACE inhibition may prolong survival in these patients. The success of captopril, the first oral agent of this class, promises to hold true for other ACE inhibitors (such as enalapril), which have similar activities but differing pharmacokinetic properties and will soon be available for clinical use. Further information on these newer agents is anxiously awaited. In the near future, the clinician will undoubtedly be able to choose from a large selection of ACE inhibitors for the treatment of hypertension and heart failure. Therefore, it is important to learn about any meaningful differences among ACE inhibitors and to contrast this class of agents with older, standard therapies. This learning process is crucial as we assess whether newer agents offer clinical advantages over the old.

Adrenergic beta-Antagonists↗

PubMed2004

Academic underachievement by people with Prader-Willi syndrome.

BACKGROUND: Prader-Willi syndrome (PWS) is a genetically determined neurodevelopmental disorder that is associated with the under-expression of maternally imprinted genes at the 15q11-q13 chromosomal locus. In addition to a characteristic physical and behavioural phenotype, those with the syndrome have impaired social cognition, literal mindedness and inflexibility. The present authors investigated the relationship between the PWS cognitive and behavioural phenotype, educational experience, and levels of attainment in reading, writing and arithmetic. METHODS: All subjects from a population-based sample of people with PWS, augmented by those with PWS living in other regions together with a contrast group of people with learning disability (LD) of other aetiologies, are included in the present study. Those children over 3 years of age whose families consented or adults who themselves consented were assessed for ability and attainment (over 7 years of age), and information on functional ability was also obtained from an informant. Underachievement was defined as the difference between the score predicted from full-scale IQ and the actual achievement score. RESULTS: Commonly, levels of achievement were lower than would have been predicted on the basis of IQ among those in the groups with PWS and LD. In the group with PWS, underachievement across academic domains was positively correlated with the percentage of time in education in a special school and negatively correlated with Vineland Socialization domain standard score. There were no across-domain significant correlations in the group with LD. When using multiple regression analysis, the percentage of time in special school was the only predictor of underachievement and only in the group with PWS. However, some children with PWS in special schools did achieve as expected in at least one academic domain. CONCLUSIONS: Children with PWS may be placed in special schools largely because of their behavioural problems or physical disabilities, or expectations based on their PWS status. Their intellectual abilities may well be masked by their immature social behaviour. The present authors propose that a failure to recognize and address the specific educational needs which follow from this combination of poor socialization skills and complex maladaptive behaviours, in the context of relatively mild LD, may explain their findings.

Adolescent↗

PubMed2006

Effect of age on detection of gaps in speech and nonspeech markers varying in duration and spectral symmetry.

Gap detection thresholds for speech and analogous nonspeech stimuli were determined in younger and older adults with clinically normal hearing in the speech range. Gap detection thresholds were larger for older than for younger listeners in all conditions, with the size of the age difference increasing with stimulus complexity. For both ages, gap detection thresholds were far smaller when the markers before and after the gap were the same (spectrally symmetrical) compared to when they were different (spectrally asymmetrical) for both speech and nonspeech stimuli. Moreover, gap detection thresholds were smaller for nonspeech than for speech stimuli when the markers were spectrally symmetrical but the opposite was observed when the markers were spectrally asymmetrical. This pattern of results may reflect the benefit of activating well-learned gap-dependent phonemic contrasts. The stimulus-dependent age effects were interpreted as reflecting the differential effects of age-dependent losses in temporal processing ability on within- and between-channel gap detection.

Adult↗

PubMed1979

Behavioral contrast during the acquisition of speechreading.

Two hearing-impaired children were taught to speechread the names of 18 objects divided into three sets. A multiple baseline across sets of objects was obtained for each subject. Tokens presented contingent upon correct responses to certain sets of names increased the frequencies of those correct responses. Both subjects exhibited positive behavioral contrast during the acquisition of speechreading; correct responses to one set increased above the previously established level when the contingencies for a second set changed from token reinforcement to extinction. The obtained contrast effect was conductive to learning and the procedure was effective in teaching the children to speechread the training words.

Behavior Therapy↗

PubMed1999

Generating novel ideas: fluency performance in high-functioning and learning disabled individuals with autism.

Tasks of fluency tap the ability to generate multiple responses spontaneously following a single cue or instruction. The present study compared the fluency performance of subjects with autism and clinical control subjects at two different levels of ability (high-functioning subjects with a verbal IQ of 76 or greater, and globally learning disabled subjects with a verbal IQ of 74 or below). A battery of tasks was employed to assess subjects' word fluency (for letters and semantic categories), ideational fluency (for uses of objects and interpretations of meaningless line drawings), and design fluency (for abstract meaningless designs). Subjects with autism showed reduced fluency for both the word and ideational fluency tasks, generating significantly fewer responses than the clinical control subjects. Results were particularly striking for the ideational fluency tasks. On these tasks, autistic subjects produced very low response totals, with the performance of the high-functioning subjects with autism equivalent to that of the learning disabled subjects with autism and significantly inferior to that of the learning disabled control individuals. In contrast, the results of the design fluency paradigm paint a different picture. This paradigm revealed no significant difference in the quantity of designs generated by the subjects with autism and the control subjects but a clear qualitative difference, with the autistic group producing significantly higher rates of disallowed and perseverative responses. Whilst the results of the word and ideational fluency tasks are suggested to support the hypothesis that individuals with autism are impaired in the generation of novel responses and behaviour, the results of the design fluency task are equally consistent with an impairment in the regulation of behaviour through inhibition and/or monitoring. The implications of these findings for the study of executive function abilities in autism are discussed.

Adolescent↗

PubMed1989

Nerves on magnetic resonance imaging.

Nerves are often visualized on magnetic resonance imaging (MRI) studies of the soft tissues on the chest and shoulder girdle. To learn the reasons for the contrast between the nerves and adjacent tissues, the authors obtained a fresh specimen containing part of the brachial plexus nerves from the left axilla and compared MRI with x-ray projections and photomicrographs of histologic sections. The results suggest that the high signals from the nerves stand out in contrast to the low signals from their rich vascular supply.

Connective Tissue↗

PubMed1987

Parent-adolescent conflict: an empirical review.

Conflict between parents and adolescents is usually seen as a normal and necessary part of human development. However, treatment approaches for problematic conflict differ depending on several variables including theoretical orientation of the clinician. This article compares and contrasts psychoanalytic, systems, and social learning theories in order to determine the empirical support for each. In addition, several issues inherent in parent-adolescent conflict are reviewed including developmental stage theory, parenting styles, peer pressures, communications skills, marital conflict, drugs, school, and sex. Several studies and reviews of the literature are examined for common conclusions. Finally, an integrated and empirically supported model to explain parent-adolescent conflict is described.

Adolescent↗

PubMed1997

Brain aging: impaired coding of novel environmental cues.

Studies of the spatial memory capacities of aged animals usually focus on performance during the learning of new environments. By contrast, efforts to characterize age-related alterations in spatial firing information processing by hippocampal neurons typically use an environment that is highly familiar to the animals. In the present study we compared the firing properties of hippocampal neurons in young adult and aged rats as they acquired spatial information about new environmental cues. Hippocampal complex spike cells were recorded while rats performed a radial arm maze task in a familiar environment and then recorded again after many of the spatial cues were changed. After the change in the environment, in aged rats 35-42% of place fields retained their original shape and location with respect to the maze center, although they usually rotated to another arm. By contrast, all place fields in young animals either disappeared or appeared in a new location. Some of the new place fields appeared in the new environment during the first 5 min of exploration, whereas others needed more than 30 min to develop fully. In the familiar environment spatial selectivity of place cells was similar in young and aged rats. By contrast, when rats were placed into a new environment, spatial selectivity decreased considerably in aged memory-impaired rats compared with that of young rats and aged rats with intact memory performance.

Aging↗

PubMed2000

Stimulus enhancement in greylag geese: socially mediated learning of an operant task.

We recently observed the spreading of a novel tradition in a flock of semiferal greylag geese, Anser anser: an increasing number of individuals began to bite and chew the stems of butterbur, Petasites hybridus. Because this behaviour spread particularly fast within families, social learning seemed to be involved. We therefore designed an experiment with hand-reared goslings, which were socially imprinted on humans, to investigate whether and how the observation of an experienced tutor affects the acquisition of a novel skill. Goslings had to open the gliding lid of a box to get at a food reward. To each of seven hand-reared observers a human tutor demonstrated where and how to open the lid, whereas seven controls remained untutored. All observers learned to perform the task but only one of the controls succeeded. The observers explored more often at the position shown by the tutor than elsewhere and seemingly learned by trial and error. In contrast, control birds explored primarily at positions that did not allow them to open the box. These results indicate that in greylag goslings the observation of an experienced model facilitates the learning of an operant task. We conclude that stimulus enhancement followed by operant conditioning were the mechanisms involved, which may have accounted for the fast spread of the stem-chewing tradition between family members. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1998

Self-organization of binocular disparity tuning by reciprocal corticogeniculate interactions.

This article develops a neural model of how sharp disparity tuning can arise through experience-dependent development of cortical complex cells. This learning process clarifies how complex cells can binocularly match left and right eye image features with the same contrast polarity, yet also pool signals with opposite contrast polarities. Antagonistic rebounds between LGN ON and OFF cells and cortical simple cells sensitive to opposite contrast polarities enable anticorrelated simple cells to learn to activate a shared set of complex cells. Feedback from binocularly tuned cortical cells to monocular LGN cells is proposed to carry out a matching process that dynamically stabilizes the learning process. This feedback represents a type of matching process that is elaborated at higher visual processing areas into a volitionally controllable type of attention. We show stable learning when both of these properties hold. Learning adjusts the initially coarsely tuned disparity preference to match the disparities present in the environment, and the tuning width decreases to yield high disparity selectivity, which enables the model to quickly detect image disparities. Learning is impaired in the absence of either antagonistic rebounds or corticogeniculate feedback. The model also helps to explain psychophysical and neurobiological data about adult 3-D vision.

Algorithms↗

PubMedDate not supplied

Contour integration in amblyopic monkeys.

Amblyopia is characterized by losses in a variety of aspects of spatial vision, such as acuity and contrast sensitivity. Our goal was to learn whether those basic spatial deficits lead to impaired global perceptual processing in strabismic and anisometropic amblyopia. This question is unresolved by the current human psychophysical literature. We studied contour integration and contrast sensitivity in amblyopic monkeys. We found deficient contour integration in anisometropic as well as strabismic amblyopic monkeys. Some animals showed poor contour integration in the fellow eye as well as in the amblyopic eye. Orientation jitter of the elements in the contour systematically decreased contour-detection ability for control and fellow eyes, but had less effect on amblyopic eyes. The deficits were not clearly related to basic losses in contrast sensitivity and acuity for either type of amblyopia. We conclude that abnormal contour integration in amblyopes reflects disruption of mechanisms that are different from those that determine acuity and contrast sensitivity, and are likely to be central to V1.

Adaptation, Psychological↗

PubMed1989

Reduced brightness contrast as a reading aid.

A standard reading comprehension test, modified by printing half of the material on medium grey paper to lower the contrast of print-to-page, was administered to 54 college students, 21 of whom had previously been diagnosed as learning disabled. Comprehension of the control group was little affected by the contrast, but the mean score for the learning disabled students was 10% higher on the pages with reduced contrast. This is congruent with Meares's 1980 clinical observations that reducing contrast significantly aids some readers.

Female↗

PubMed2001

Deficient long-term synaptic depression in the rostral cerebellum correlated with impaired motor learning in phospholipase C beta4 mutant mice.

Long-term depression (LTD) at parallel fibre-Purkinje cell synapse of the cerebellum is thought to be a cellular substrate for motor learning. LTD requires activation of metabotropic glutamate receptor subtype 1 (mGluR1) and its downstream signalling pathways, which invariably involves phospholipase Cbetas (PLCbetas). PLCbetas consist of four isoforms (PLCbeta1-4) among which PLCbeta4 is the major isoform in most Purkinje cells in the rostral cerebellum (lobule 1 to the rostral half of lobule 6). We studied mutant mice deficient in PLCbeta4, and found that LTD was deficient in the rostral but not in the caudal cerebellum of the mutant. Basic properties of parallel fibre-Purkinje cell synapses and voltage-gated Ca2+ channel currents appeared normal. The mGluR1-mediated Ca2+ release induced by repetitive parallel fibre stimulation was absent in the rostral cerebellum of the mutant, suggesting that their LTD lesion was due to the defect in the mGluR1-mediated signalling in Purkinje cells. Importantly, the eyeblink conditioning, a simple form of discrete motor learning, was severely impaired in PLCbeta4 mutant mice. Wild-type mice developed the conditioned eyeblink response, when pairs of the conditioned stimulus (tone) and the unconditioned stimulus (periorbital shock) were repeatedly applied. In contrast, PLCbeta4 mutant mice could not learn the association between the conditioned and unconditioned stimuli, although their behavioural responses to the tone or to the periorbital shock appeared normal. These results strongly suggest that PLCbeta4 is essential for LTD in the rostral cerebellum, which may be required for the acuisition of the conditioned eyeblink response.

Animals↗

PubMed2003

Evolving spike-timing-dependent plasticity for single-trial learning in robots.

Single-trial learning is studied in an evolved robot model of synaptic spike-timing-dependent plasticity (STDP). Robots must perform positive phototaxis but must learn to perform negative phototaxis in the presence of a short-lived aversive sound stimulus. STDP acts at the millisecond range and depends asymmetrically on the relative timing of pre- and post-synaptic spikes. Although it has been involved in learning models of input prediction, these models require the iterated presentation of the input pattern, and it is hard to see how this mechanism could sustain single-trial learning over a time-scale of tens of seconds. An incremental evolutionary approach is used to answer this question. The evolved robots succeed in learning the appropriate behaviour, but learning does not depend on achieving the right synaptic configuration but rather the right pattern of neural activity. Robot performance during positive phototaxis is quite robust to loss of spike-timing information, but in contrast, this loss is catastrophic for learning negative phototaxis where entrained firing is common. Tests show that the final weight configuration carries no information about whether a robot is performing one behaviour or the other. Fixing weights, however, has the effect of degrading performance, thus demonstrating that plasticity is used to sustain the neural activity corresponding both to the normal phototaxis condition and to the learned behaviour. The implications and limitations of this result are discussed.

Action Potentials↗

PubMed1987

Is increase in post-learning paradoxical sleep modified by cueing?

Rats were submitted to three sessions of an active avoidance conditioning. The conditioned stimulus (CS) was either an ear shock or a tone. Sleep was measured after each session. Experimental animals received non-awakening ear shocks during post-learning paradoxical sleep (PS). When ear shocks were the CS and were subsequently used as cues during PS, PS increases were observed, but they displayed 2 unusual characteristics: they were due to longer average size of PS phases rather than to higher number of phases as usually; PS did not return to baseline level even when learning seemed to be achieved. By contrast, when ear shocks were not associated with conditioning, animals shocked during PS exhibited the usual PS increases.

Animals↗

PubMed2006

A link between perceptual learning, adaptation and sleep.

Between-sessions gains in the texture discrimination task have been attributed to memory consolidation. A strong dependence of consolidation on sleep was suggested though not always supported by experimental results. Here we suggest that the interaction between consolidation and sleep depends on the adaptation level obtained during the training session. We find that both discrimination thresholds and learning depend on the number of trials used during training, with more trials producing higher discrimination thresholds due to suppressive processes related to adaptation. In addition, while learning benefits from increasing number of trials, a further increase in number of trials reduces learning. Consolidation may benefit from between-session sleep in the adapted states.

Adaptation, Psychological↗

PubMed2000

Learning and memory impairment in cocaine-dependent and comorbid schizophrenic patients.

Impairments in verbal learning and memory functioning have been found to be cardinal features among individuals with schizophrenia as well as among non-schizophrenic cocaine abusers. Cognitive deficits in these areas, moreover, have been associated with poor treatment response and short-term outcome. Little is known, however, about the acute effects of cocaine abuse on schizophrenic patients' learning and memory functioning. Consequently, a potentially reversible and treatable source of cognitive impairment has been virtually ignored. The present study examined the extent of verbal learning and memory impairment in a group of cocaine-dependent schizophrenic patients (n=42) and a group of non-schizophrenic cocaine-dependent patients (n=21) within 72 h of the last cocaine use using the California Verbal Learning Test (CVLT). Schizophrenic patients (n=34) without any substance-use disorders were also tested in an identical time frame and served as a comparison group. Results revealed that all groups demonstrated significant learning and memory impairment relative to CVLT published age and gender corrected norms. Both cocaine-dependent and non-substance abusing schizophrenic groups presented a very similar pattern of impaired learning and recall performance across all CVLT task domains. Comorbid patients, in contrast, presented with marked deficits in their ability to learn and recall verbal information relative to either schizophrenic or cocaine-only groups. Moreover, the cocaine-abusing schizophrenic patients showed significant forgetfulness of the information that they did acquire during delayed recall conditions. The performance deficits exhibited by cocaine-abusing schizophrenic patients differed not only in relative severity of impairment, but also qualitatively in their increased rates of forgetfulness of acquired information. These results are interpreted in terms of the neurobiological substrates of learning and memory and the neurobiological impact of cocaine on schizophrenic patients' cognition during the early phase of inpatient hospitalization. These results suggest that comorbid patients should be targeted for specialized remediation efforts at the beginning phases of inpatient treatment.

Acute Disease↗