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PubMed1978

Kinetics of drug interactions in the treatment of epilepsy.

The interactions of antiepileptic drugs in multiple drug treatment have been discussed. Although some combinations may lead to predictable increase or decrease of clearance of the respective drugs, most combinations will individually lead to a reduced predictability. Monitoring plasma concentrations may lead to adaptations of the choice of the drug and of the dosage regimen. Also physiological conditions control the individual clearance of antiepileptic drugs.

Animals↗
PubMed1995

Retrospective testing of an insulin advisory system.

A retrospective analysis of the function of adaptive model based consultation system for insulin therapy was performed. The program proved good adaptation ability with improving blood glucose level prediction. In a group of 12 brittle type 1 diabetic patients individual analysis showed problems resulting from retrospective testing of dynamic systems, when treatment is determined only by the physician.

Blood Glucose↗
PubMed1998

Social support predicts 5-year outcome in first-episode schizophrenia.

Investigations of social support in schizophrenia have been relatively sparse. In this research, patients with 1st-episode schizophrenia or affective psychosis were asked to describe supportive social relationships immediately prior to their 1st lifetime treatment contact and were interviewed 18 months and 5 years later for assessment of their social and occupational functioning. The results indicated that 18-month adaptive functioning was lower than in the year prior to 1st treatment contact but at 5 years rose above that seen both at baseline and 18 months. Moreover, social support from nonfamily members of the social network predicted 5-year adaptive functioning in the schizophrenia (n = 54) group but not in the affective psychosis (n = 55) group. Support from family did not predict 5-year outcome in either group. Together, these findings replicate and extend earlier findings that social support predicts outcome in 1st-episode schizophrenia.

Adolescent↗
PubMed1989

The effect of 0.5% thymoxamine on the pattern-onset electroretinogram.

Thymoxamine constricts the pupil without significant effect on accommodation and was used in this study because of the extreme sensitivity of the pattern electroretinogram (PERG) to defocus at high spatial frequencies. Pilocarpine, used in previous studies, can cause an unpredictable spasm of accommodation. A reduction in pupil size has two effects on the PERG due to illuminance and optical degradation. Illuminance differences can be compensated by neutral density filters. This allows the effects of optical degradation on the PERG to be examined under conditions of constant adaptation. Our studies on a group of 10 subjects have shown the PERG to be proportional to contrast. As contrast degradation is reduced with a smaller pupil, a larger PERG amplitude is predicted. However the tuning of neural elements under constant adaptation should not alter. Pattern onset ERGs were recorded from a further 10 subjects in response to checkerboards of various spatial frequencies under two conditions, a) with pupils moised by thymoxamine hydrochloride 0.5% and b) with natural pupils. Adaptation level was equated by a 0.4 neutral density filter before the natural pupils. The group-averaged PERGs were analyzed into retinal illuminance and pattern-specific responses. A paired t-test showed the pattern-onset ERG amplitudes to be significantly different in the two conditions, but the computed pattern-specific responses were virtually identical. These results therefore support the theory and method used for the extraction of the pattern-specific response.

Contrast Sensitivity↗
PubMed1988

From conditioning to category learning: an adaptive network model.

We used adaptive network theory to extend the Rescorla-Wagner (1972) least mean squares (LMS) model of associative learning to phenomena of human learning and judgment. In three experiments subjects learned to categorize hypothetical patients with particular symptom patterns as having certain diseases. When one disease is far more likely than another, the model predicts that subjects will substantially overestimate the diagnosticity of the more valid symptom for the rare disease. The results of Experiments 1 and 2 provide clear support for this prediction in contradistinction to predictions from probability matching, exemplar retrieval, or simple prototype learning models. Experiment 3 contrasted the adaptive network model with one predicting pattern-probability matching when patients always had four symptoms (chosen from four opponent pairs) rather than the presence or absence of each of four symptoms, as in Experiment 1. The results again support the Rescorla-Wagner LMS learning rule as embedded within an adaptive network model.

Association Learning↗
PubMed2004

Modelling the fate of persistent organic pollutants in Europe: parameterisation of a gridded distribution model.

A regionally segmented multimedia fate model for the European continent is described together with an illustrative steady-state case study examining the fate of gamma-HCH (lindane) based on 1998 emission data. The study builds on the regionally segmented BETR North America model structure and describes the regional segmentation and parameterisation for Europe. The European continent is described by a 5 degrees x5 degrees grid, leading to 50 regions together with four perimetric boxes representing regions buffering the European environment. Each zone comprises seven compartments including; upper and lower atmosphere, soil, vegetation, fresh water and sediment and coastal water. Inter-regions flows of air and water are described, exploiting information originating from GIS databases and other georeferenced data. The model is primarily designed to describe the fate of Persistent Organic Pollutants (POPs) within the European environment by examining chemical partitioning and degradation in each region, and inter-region transport either under steady-state conditions or fully dynamically. A test case scenario is presented which examines the fate of estimated spatially resolved atmospheric emissions of lindane throughout Europe within the lower atmosphere and surface soil compartments. In accordance with the predominant wind direction in Europe, the model predicts high concentrations close to the major sources as well as towards Central and Northeast regions. Elevated soil concentrations in Scandinavian soils provide further evidence of the potential of increased scavenging by forests and subsequent accumulation by organic-rich terrestrial surfaces. Initial model predictions have revealed a factor of 5-10 underestimation of lindane concentrations in the atmosphere. This is explained by an underestimation of source strength and/or an underestimation of European background levels. The model presented can further be used to predict deposition fluxes and chemical inventories, and it can also be adapted to provide characteristic travel distances and overall environmental persistence, which can be compared with other long-range transport prediction methods.

Climate↗
PubMed2006

A phyloclimatic study of Cyclamen.

BACKGROUND: The impact of global climate change on plant distribution, speciation and extinction is of current concern. Examining species climatic preferences via bioclimatic niche modelling is a key tool to study this impact. There is an established link between bioclimatic niche models and phylogenetic diversification. A next step is to examine future distribution predictions from a phylogenetic perspective. We present such a study using Cyclamen (Myrsinaceae), a group which demonstrates morphological and phenological adaptations to its seasonal Mediterranean-type climate. How will the predicted climate change affect future distribution of this popular genus of garden plants? RESULTS: We demonstrate phylogenetic structure for some climatic characteristics, and show that most Cyclamen have distinct climatic niches, with the exception of several wide-ranging, geographically expansive, species. We reconstruct climate preferences for hypothetical ancestral Cyclamen. The ancestral Cyclamen lineage has a preference for the seasonal Mediterranean climate characteristic of dry summers and wet winters. Future bioclimatic niches, based on BIOCLIM and Maxent models, are examined with reference to a future climate scenario for the 2050s. Over the next 50 years we predict a northward shift in the area of climatic suitability, with many areas of current distribution becoming climatically unsuitable. The area of climatic suitability for every Cyclamen species is predicted to decrease. For many species, there may be no areas with a suitable climate regardless of dispersal ability, these species are considered to be at high risk of extinction. This risk is examined from a phylogenetic perspective. CONCLUSION: Examining bioclimatic niches from a phylogenetic perspective permits novel interpretations of these models. In particular, reconstruction of ancestral niches can provide testable hypothesis about the historical development of lineages. In the future we can expect a northwards shift in climatic suitability for the genus Cyclamen. If this proves to be the case then dispersal is the best chance of survival, which seems highly unlikely for ant-dispersed Cyclamen. Human-assisted establishment of Cyclamen species well outside their native ranges offers hope and could provide the only means of dispersal to potentially suitable future environments. Even without human intervention the phylogenetic perspective demonstrates that major lineages could survive climate change even if many species are lost.

Algorithms↗
PubMed2005

Differential selection and mutation between dsDNA and ssDNA phages shape the evolution of their genomic AT percentage.

BACKGROUND: Bacterial genomes differ dramatically in AT%. We have developed a model to show that the genomic AT% in rapidly replicating bacterial species can be used as an index of the availability of nucleotides A and T for DNA replication in cellular medium. This index is then used to (1) study the evolution and adaptation of the bacteriophage genomic AT% in response to the differential nucleotide availability of the host and (2) test the prediction that double-stranded DNA (dsDNA) phage should exhibit better adaptation than single-stranded DNA (ssDNA) phage because the rate of spontaneous deamination, which leads to C-->T or C-->U mutations depending on whether C is methylated or not, is about 100-fold greater in ssDNA than in dsDNA. RESULTS: We retrieved 79 dsDNA phage and 27 ssDNA phage genomes together with their host genomic sequences. The dsDNA phages have their genomic AT% better adapted to the host genomic AT% than ssDNA phage. The poorer adaptation of the ssDNA phage can be partially accounted for by the C-->T(U) mutations mediated by the spontaneous deamination. For ssDNA phage, the genomic A% is more strongly correlated with their host genomic AT% than the genomic T%. CONCLUSION: A significant fraction of variation in the genomic AT% in the dsDNA phage, and that in the genomic A% and T% of the ssDNA phage, can be explained by the difference in selection and mutation between them.

Bacteriophages↗
PubMed1979

Behavior therapy as a test of psychoanalytic theory.

The author describes 4 patients in whom radically new symptoms appeared after intensive behavior therapy. He suggests that fresh symptoms are most likely to develop in a small minority of patients who are unable to learn more adaptive psychological defense mechanisms during or after behavior therapy and that psychoanalytic theory may help predict the nature of such symptoms.

Adaptation, Psychological↗
PubMed1996

The connection between the psychological condition of breast cancer patients and survival. A follow-up after eight years.

Forty breast cancer patients (Stage I, II) were interviewed in 1984. Eight years later, in 1992, 8 of the 40 women had died in the intervening period of time, another 7 women had developed bone metastases, and the remaining 25 women had no evidence of disease. The main findings of this study indicate that the psychological distress, anxiety, hostility, paranoid ideation and psychoticism, as well as the Global Severity Index (GSI), of the eight patients who died during the 8 years following diagnosis were more severe at the time of diagnosis than that of the patients who survived. Moreover, the findings indicate that severity of anxiety may predict length of survival.

Adaptation, Psychological↗
PubMed2005

Adaptive coding of reward value by dopamine neurons.

It is important for animals to estimate the value of rewards as accurately as possible. Because the number of potential reward values is very large, it is necessary that the brain's limited resources be allocated so as to discriminate better among more likely reward outcomes at the expense of less likely outcomes. We found that midbrain dopamine neurons rapidly adapted to the information provided by reward-predicting stimuli. Responses shifted relative to the expected reward value, and the gain adjusted to the variance of reward value. In this way, dopamine neurons maintained their reward sensitivity over a large range of reward values.

Adaptation, Physiological↗
PubMed2006

Smoking rates and topography predict adolescent smoking cessation following treatment with nicotine replacement therapy.

Establishing measurement invariance of tobacco addiction among adolescents remains challenging. In adult smoking cessation trials, poor outcome is predicted by high cigarette consumption and large puff volume at baseline. We examined the predictive value of pretreatment smoking rates and topography variables for abstinence outcomes among 66 adolescents enrolled in a 3-month smoking cessation trial using nicotine replacement and cognitive behavioral therapy. Pretreatment variables included cigarettes per day (CPD), puff volume, puff duration, and several youth-adapted Fagerström-derived questionnaire scores. Outcome measures included prolonged abstinence at end of treatment and point-prevalent abstinence 3 months after the end of the trial. Logistic regression controlling for treatment group showed that increases in baseline CPD (odds ratio, 1.438; 95% confidence interval, 1.051-1.967) and average puff volume (odds ratio, 1.168; 95% confidence interval, 1.030-1.326) predicted continued smoking at the end of treatment. Puff volume (P=0.013), but not CPD, predicted abstinence at the 3-month follow-up. None of the youth-adapted Fagerström questionnaires predicted outcome on either abstinence measure. If confirmed in a larger sample, our findings suggest that puff topography, and possibly CPD, might predict cessation outcome better than Fagerström scores in adolescent smokers.

Administration, Cutaneous↗
PubMed2004

Reliability of internal prediction/estimation and its application. I. Adaptive action selection reflecting reliability of value function.

This article proposes an adaptive action-selection method for a model-free reinforcement learning system, based on the concept of the 'reliability of internal prediction/estimation'. This concept is realized using an internal variable, called the Reliability Index (RI), which estimates the accuracy of the internal estimator. We define this index for a value function of a temporal difference learning system and substitute it for the temperature parameter of the Boltzmann action-selection rule. Accordingly, the weight of exploratory actions adaptively changes depending on the uncertainty of the prediction. We use this idea for tabular and weighted-sum type value functions. Moreover, we use the RI to adjust the learning coefficient in addition to the temperature parameter, meaning that the reliability becomes a general basis for meta-learning. Numerical experiments were performed to examine the behavior of the proposed method. The RI-based Q-learning system demonstrated its features when the adaptive learning coefficient and large RI-discount rate (which indicate how the RI values of future states are reflected in the RI value of the current state) were introduced. Statistical tests confirmed that the algorithm spent more time exploring in the initial phase of learning, but accelerated learning from the midpoint of learning. It is also shown that the proposed method does not work well with the actor-critic models. The limitations of the proposed method and its relationship to relevant research are discussed.

Acclimatization↗
PubMed1992

Stress, anxiety, and cognitive buffering.

Cognitive theories of psychopathology and therapy maintain that attitudes and beliefs mediate one's affective responses to life events. Anxiety and depression are thus consequences, not of an individual's circumstances, but of the distorted, irrational perspective from which these are viewed. Similarly, although less often considered, adaptive cognitions should serve as buffers against stressful life events. This proposition has received little attention, and the single study that attempted to address it directly failed to do so. The present investigation sought to reassess the buffering hypothesis. Ninety-seven subjects were evaluated as to (1) the levels of stress they had experienced in the recent past; (2) their current feelings of anxiety and depression; and (3) the extent to which they endorsed illogical, unrealistic attitudes. Dysfunctional attitudes demonstrated strong direct relations with psychological distress. Two of the several indices of life stress, total and negative scores on the Life Experiences Survey, also correlated with distress. There was no significant interaction between the attitude and stress measures. Cognitions, at least on the functional-dysfunctional dimension, did not moderate the impact of life events. Rather, both attitudes and life stresses were strong independent variables that, in additive fashion, provided considerable power for predicting distress.

Adaptation, Psychological↗
PubMed1998

Neonatal neurological examination as a predictor of neuromotor outcome at 4 months in term low-Apgar-score babies in Zimbabwe.

The predictive value of the neonatal neurological examination (NNE) adapted from Prechtl, was investigated in 139 term Zimbabwean infants born with an Apgar score of five or less at 5 min. At 4 months, seven infants had died and 13 were lost to follow-up, leaving 119 infants to undergo the Infant Motor Screen (IMS). Eighty-eight infants were diagnosed as normal, six as suspect and 25 as abnormal at screening. The sensitivity, specificity, positive predictive value and negative predictive value of the NNE were 94%, 55%, 42% and 96%, respectively. Seventeen (14%) infants had developed microcephaly at 4 months and 13 (77%) of them scored abnormal on the IMS. Twenty-three of the 48 (48%) infants who had convulsions within 48 h of birth, were diagnosed as abnormal (P < 0.0001). The NNE proved to be very sensitive in detecting neurodevelopmental abnormalities in the neonatal period and the five abnormal syndromes derived from the NNE were able to correctly identify 94% of the abnormal infants.

Adolescent↗
PubMedDate not supplied

[Venous pressure in the jugular vein system and the efficiency of venous return to the right heart during 120-day antiorthostatic hypokinesia].

Study of time-course variations of venous pressure in the jugular veins can be used to identify individual adaptation to prolonged head-down tilt. The method of measuring blood return to the right heart presented here can be employed to evaluate the efficacy of countermeasures during head-down tilt and to predict orthostatic tolerance after it.

Adaptation, Physiological↗
PubMed1972

Adaptation to square-wave gratings: inhibition between spatial frequency channels in the human visual system.

1. The observation that the detection threshold for a square-wave grating depends only on that of its fundamental was confirmed by showing that adapting to the fundamental spatial frequency caused elevation of the square-wave threshold, to the same extent as the fundamental threshold was elevated by the same adapting pattern. Adapting to the third harmonic frequency had no effect on the square-wave threshold.2. Adapting to a square-wave grating should elevate the thresholds for both the fundamental and third harmonic frequencies (Blakemore & Campbell, 1969), and the amount of elevation at each frequency should be predictable from the contrast of that frequency within the square-wave.3. It was found, however, that both the fundamental and third harmonic, when present in the square-wave, were much less effective as suprathreshold adapting stimuli than would be predicted from their effects when viewed in isolation.4. Adapting to a mixture of two sinusoidal gratings (with 3:1 frequency ratio) demonstrated that the fall in adapting power was not due to the higher harmonics of the square-wave nor to nonlinearities in the stimulus display. Similar effects were found when the phase relations of the adapting gratings were changed, showing that the interaction is not a special property of square-waves or of edges.5. It is suggested that the spatial frequency channels subserving the fundamental and third harmonic frequencies inhibit each other when the patterns are some way suprathreshold. At or near threshold, there is no such reciprocal inhibition.

Adaptation, Ocular↗
PubMedDate not supplied

Predictors of postoperative binocularity in adult strabismus.

We evaluated postoperative binocularity in a retrospective study of 111 adult strabismus patients in order to identify the factors which influence the success of surgery for horizontal concomitant strabismus in adults. Selection criteria included minimum age of 15 years at time of surgery, and preoperative fusion impairment with both the Bagolini lens test and synoptophore. Logistic regression analysis was used to correlate patient factors and postoperative binocularity. We found that 52 (65%) of 80 patients with exotropia and 23 (74.2%) of 31 patients with esotropia achieved post operative fusion. Significant predictive factors in exotropia were absence of previous surgery; visual acuity of the deviating eye > 0.5; an increase in the spherical equivalent of the deviating eye, and normal retinal correspondence. Significant predictive factors in esotropia were fusion during prism adaptation, absence of infantile esotropia, and an increase in vertical deviation. The majority of adults with exotropia or esotropia can achieve binocularity after surgery for horizontal concomitant strabismus.

Adolescent↗