Role of anxiety level and stress in rule acquisition.
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Anxiety↗
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Results for “Probability Learning”
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General conditions for predictivity in learning theory.
Developing theoretical foundations for learning is a key step towards understanding intelligence. 'Learning from examples' is a paradigm in which systems (natural or artificial) learn a functional relationship from a training set of examples. Within this paradigm, a learning algorithm is a map from the space of training sets to the hypothesis space of possible functional solutions. A central question for the theory is to determine conditions under which a learning algorithm will generalize from its finite training set to novel examples. A milestone in learning theory was a characterization of conditions on the hypothesis space that ensure generalization for the natural class of empirical risk minimization (ERM) learning algorithms that are based on minimizing the error on the training set. Here we provide conditions for generalization in terms of a precise stability property of the learning process: when the training set is perturbed by deleting one example, the learned hypothesis does not change much. This stability property stipulates conditions on the learning map rather than on the hypothesis space, subsumes the classical theory for ERM algorithms, and is applicable to more general algorithms. The surprising connection between stability and predictivity has implications for the foundations of learning theory and for the design of novel algorithms, and provides insights into problems as diverse as language learning and inverse problems in physics and engineering.
Algorithms↗
Practical model-based dose-finding in phase I clinical trials: methods based on toxicity.
We describe two practical, outcome-adaptive statistical methods for dose-finding in phase I clinical trials. One is the continual reassessment method and the other is based on a logistic regression model. Both methods use Bayesian probability models as a basis for learning from the accruing data during the trial, choosing doses for successive patient cohorts, and selecting a maximum tolerable dose (MTD). These methods are illustrated and compared to the conventional 3+3 algorithm by application to a particular trial in renal cell carcinoma. We also compare their average behavior by computer simulation under each of several hypothetical dose-toxicity curves. The comparisons show that the Bayesian methods are much more reliable than the conventional algorithm for selecting an MTD, and that they have a low risk of treating patients at unacceptably toxic doses.
Algorithms↗
School performance in adolescents with and without periventricular-intraventricular hemorrhage in the neonatal period.
Long-term sequelae of preterm birth have been studied extensively up until the age of 5 to 8 years. However, the cognitive development of adolescents born preterm has received limited attention. The objective of this study is to determine school performance in adolescents born very preterm. We have followed up a cohort of 484 infants born before 32 weeks of gestation in whom cranial ultrasound was routinely and systematically performed. School performance was assessed in the surviving adolescents at 14 years of age. The outcome variable divided the adolescents into three groups: (1) normal, (2) slow learners, and (3) special education. School performance data were obtained from 278 of 304 surviving adolescents; 129 performed normally, while 107 were slow learners, and 42 needed special education. From the unadjusted odds ratios for the need of special education by the various perinatal factors, only the odds ratio for periventricular-intraventricular hemorrhage was significantly associated (2.56, 95% confidence interval 1.17-4.86). Logistic regression analysis revealed that, after correction for possible confounding factors, the odds ratios for special education were significantly higher for adolescents with all grades of periventricular-intraventricular hemorrhage. Less than 50% of adolescents born before 32 weeks gestation perform normally in school. Periventricular-intraventricular hemorrhage, including the lower grades,does have an unfavorable additional effect on school performance.
Adolescent↗
Graft-induced behavioral recovery in an animal model of Huntington disease.
Bilateral ibotenic acid lesions of the anteromedial neostriatum produce neuropathological and behavioral changes in rats that are characterized by locomotor hyperactivity and severe maze learning impairments, which can be viewed as analogous to changes seen in Huntington disease. Grafts of fetal striatal neurons, implanted either into the lesioned striatum or into the denervated globus pallidus, reduced both the learning impairments and the locomotor hyperactivity, probably via different mechanisms. The results demonstrate the capacity of neural implants for functional neuronal replacement and promotion of functional recovery after damage to a major telencephalic structure participating in complex cognitive and motoric behaviors.
Animals↗
A study of the ability of English speakers to guess the meanings of nonantonym foreign words.
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Adolescent↗
Positive effects of 17beta-estradiol on insulin sensitivity in aged ovariectomized female rats.
Aging is associated with insulin resistance, which represents a common factor in age-related diseases. We aimed to determine the role of 17beta-estradiol on insulin sensitivity and memory during aging using ovariectomized rats (2-26 months of age) treated with physiological doses of 17beta-estradiol. Our results indicate a lack of effect of 17beta-estradiol replacement on spatial memory assessed in a water maze. Conversely, estradiol treatment improved insulin sensitivity in aging rats. These data imply that relatively low doses of 17beta-estradiol may have beneficial effects on glucose homeostasis due to the protective effects of estrogen. However, estradiol treatment used in the present study did not prevent memory impairment associated with aging.
Aging↗
Attenuation of morphine tolerance and dependence in scopolamine-treated rats.
Morphine tolerance and dependence were investigated in scopolamine-treated rats. The results showed that scopolamine treatment (up to 2 mg/kg) did not affect basal line or morphine-induced latency in the tail-flick test but significantly increased the escape latency in the Morris water-maze task. Co-administration of scopolamine could considerably attenuate development of morphine tolerance and naloxone-precipitated withdrawal syndrome. Pretreatment of scopolamine for 7 days prior to morphine administration also significantly reduced the tolerance and withdrawal symptoms. Scopolamine treatment was further shown to attenuate morphine-induced conditioned place preference, an indicator of morphine psychological dependence. The present study demonstrated the attenuation of morphine tolerance and dependence in scopolamine-treated animals, probably related to scopolamine-produced learning and memory impairment.
Analgesics, Opioid↗
7-Nitroindazole blocks nicotine-induced conditioned place preference but not LiCl-induced conditioned place aversion.
We have shown previously that the neuronal nitric oxide synthase (nNOS) is involved in the rewarding effect of cocaine as determined by the conditioned place preference (CPP) paradigm. In the present study we investigated the effect of the nNOS inhibitor 7-nitroindazole (7-NI) on nicotine-induced CPP and LiCl-induced conditioned place aversion (CPA) in Swiss Webster mice. Mice treated with nicotine (0.5 mg/kg) or saline every other day for 8 days (four drug and four saline sessions) developed CPP that was completely blocked by pretreatment with 7-NI (25 mg/kg). Mice treated with LiCl (150 mg/kg) developed marked aversion to the LiCl-paired compartment. LiCl-induced CPA was not affected by the pretreatment with 7-NI. These findings suggest that nitric oxide (NO) plays a role in the acquisition of reward but not of aversion and that the blockade of nicotine-induced CPP is probably not due to impairment of learning and memory.
Animals↗
Headaches caused by decreased intracranial pressure: diagnosis and management.
PURPOSE OF REVIEW: More patients with spontaneous intracranial hypotension are now being diagnosed, and it is realized that most cases result from spontaneous cerebrospinal fluid leaks. A broader clinical and imaging spectrum of the disorder is recognized. This paper reviews new insights into the variability of clinical manifestations, imaging features, etiological factors, anatomy of leaks, and implications of these in patient management. RECENT FINDINGS: Spontaneous intracranial hypotension should not be equated with post-lumbar puncture headaches. In a substantial minority of patients, headaches are not orthostatic and may mimic other types of headache. Additional diverse neurological manifestations may dominate the clinical picture and patients may occasionally have no headache at all. Reports on unusual presentations of the disorder continue to appear in the literature. Furthermore, additional imaging features of cerebrospinal fluid leaks are recognized. High-flow and slow-flow leaks may present diagnostic challenges, and require modification of diagnostic studies aimed at locating the site of the leak. Stigmata of connective tissue abnormality, especially abnormalities of fibrillin and elastin, are seen in a notable minority of patients, pointing to weakness of the dural sac as one of the etiological factors. After treatment of spontaneous intracranial hypotension, surgically or by epidural blood patch, a rebound and self-limiting intracranial hypertension may sometimes develop. SUMMARY: In the past decade, interest in spontaneous intracranial hypotension has been rekindled, with a substantial growth of knowledge on various aspects of the disorder. We are in the learning phase, and new information will probably appear in the future, with notable diagnostic and therapeutic implications.
Cerebrospinal Fluid↗
Fifty years of progress in water relations research.
Many of the basic concepts dealing with soil and plant water relationships were in existence 50 years ago, but were inadequately presented in the textbooks of that time. There has been a marked increase in the amount of work done in this field during recent decades, but much of it involves advances in understanding the concepts already in existence. Three of the most important advances in the field of water relations are: (a) acceptance of the term, water potential, to describe the free energy status of water in soil and plants; (b) marked improvement in methods of measuring water potential and stomatal resistance; and (c) use of the concept of water flow in the soil-plant system as analogous to flow of electricity in a conducting system.A number of interesting and important problems remain to be studied. Of these, probably the most important is to learn why mild water stress of less than - 10 bars can affect various enzyme-mediated metabolic processes. Plant scientists in applied fields also need to learn more about the causes of differences in ability to tolerate drought among plants of various kinds. There is uncertainty concerning the relative magnitude of the resistances to water flow in various parts of the soil-plant system and concerning the causes of the apparent changes in resistance to water flow with increase in rate and with time of day. More information also is needed concerning the role of growth regulators synthesized in roots and the importance of the older, suberized roots in the absorption of water and mineral nutrients.
Journal Article↗
Signal-driven computations in speech processing.
Learning a language requires both statistical computations to identify words in speech and algebraic-like computations to discover higher level (grammatical) structure. Here we show that these computations can be influenced by subtle cues in the speech signal. After a short familiarization to a continuous speech stream, adult listeners are able to segment it using powerful statistics, but they fail to extract the structural regularities included in the stream even when the familiarization is greatly extended. With the introduction of subliminal segmentation cues, however, these regularities can be rapidly captured.
Adult↗
Neuroscience. Does grammar start where statistics stop?
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Adult↗
Cortical oscillatory activity and the dynamics of auditory memory processing.
Oscillatory activity in the gamma-band range (>30 Hz) has been proposed as a correlate of cortical network synchronization. In human electroencephalogram (EEG), enhanced gamma-band activity (GBA) has been found in relation to processes ranging from visual gestalt perception to selective attention, learning and memory. We used statistical probability mapping to investigate oscillatory signals in magnetoencephalogram (MEG) during different types of auditory processing. GBA at frequencies between 50-90 Hz was increased over posterior parietal areas during auditory spatial processing and over anterior temporal/inferior frontal regions during auditory pattern processing. GBA followed early auditory cortex responses after about 130 ms, suggesting serial processing along the putative auditory dorsal and ventral streams. During short-term memory tasks, additional frontal gamma amplitude enhancements were observed, and coherence was increased between putative sensory storage regions and prefrontal networks. These empirical findings have raised some questions concerning research on oscillatory activity. In contrast to EEG, in which gamma responses are spectrally and topographically widely distributed, activity in MEG shows more narrow distribution. This could be attributable to the higher sensitivity of MEG to smaller, more local networks that may synchronize at higher frequencies. In addition, the significance of different dominant frequencies within the gamma range still has to be elucidated. Finally, there have been suggestions of a link between GBA and hemodynamic measures of brain activity which should be explored further. In summary, oscillatory activity in MEG may provide unique information about both the activity of local networks and cortico-cortical integration.
Auditory Perception↗
Transposition in dogs: successive reversals of the intermediate size problem.
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Animals↗
Role of field dependence in perception of movements.
194 male students in physical education were administered the Group Embedded Figures Test. Those who scored high or low were selected for a perceptual experiment (n = 49). Expecting that the analyzing and (re)structuring ability of the field-independent person also applies to complex movement stimuli, subjects had to describe eight complex gross-motor gymnastic skills, demonstrated on a video system. field-independent persons tended to give more detailed descriptions of observed movements; in 5 of 8 cases the difference was statistically significant. Perhaps the field-independent person builds a more structured visual image of movements than the field-dependent person. If so, the former is probably in a better position to learn new motor skills.
Adult↗
Client types in drug-free and methadone treatment: comparison of personality traits.
The Drug-Free Therapeutic Community (TC) and Methadone Maintenance Treatment (MMT) modalities provide environmental conditions that are particularly well suited for examining addict personality characteristics suggested as important to the treatment of addiction. This study examines 174 addicts of two programs to determine how their relatedness to others varies with a self-selected treatment modality. Results indicate a generally low relatedness to others for the sample of addicts studied based on measures of the enduring trait associated with dependency on others and the more situational characteristic of interpersonal behavior. The MMT subsample showed greater social dependency in terms of the more enduring personality trait while the TC subsample was more interpersonally oriented based on the situational context. The absence of a relationship between the two measures suggests that there is a self-selection of treatment types which may serve to compensate for trait-related deficiencies or liabilities in addicts, and that the techniques employed by the approaches interact with these personality attributes that are probably accrued in the midst of learning how to cope with troubled familial settings and life as an addict.
Adult↗
Tactile perception in blind Braille readers: a psychophysical study of acuity and hyperacuity using gratings and dot patterns.
It is not clear whether the blind are generally superior to the sighted on measures of tactile sensitivity or whether they excel only on certain tests owing to the specifics of their tactile experience. We compared the discrimination performance of blind Braille readers and age-matched sighted subjects on three tactile tasks using precisely specified stimuli. Initially, the blind significantly outperformed the sighted at a hyperacuity task using Braille-like dot patterns, although, with practice, both groups performed equally well. On two other tasks, hyperacute discrimination of gratings that differed in ridge width and spatial-acuity-dependent discrimination of grating orientation, the performance of the blind did not differ significantly from that of sighted subjects. These results probably reflect the specificity of perceptual learning due to Braille-reading experience.
Adult↗