Gamma-range oscillations in backward-masking functions and their putative neural correlates

Backward-masking functions have been hitherto categorized into two types, commonly named Type A and Type B. The analysis of a model of Retino-Cortical Dynamics produces the prediction that spatially localized stimuli should reveal an oscillatory metacontrast function. The predicted new type of metacontrast masking function was investigated in a psychophysical experiment. The results show oscillatory metacontrast functions with significant power in the gamma range (30-70 Hz). A marked decrease in the oscillations is observed when the spatial extent of the stimuli is increased. The theoretical basis of the study relates the oscillations found in the metacontrast function to gamma-range oscillations observed in scalp and intracerebral recordings. The qualitative agreement between the model and data provides support for this putative relationship.     

Correction for range restriction: an expanded typology

A common research problem is the estimation of the population correlation between x and y from an observed correlation rxy obtained from a sample that has been restricted because of some sample selection process. Methods of correcting sample correlations for range restriction in a limited set of conditions are well-known. An expanded classification scheme for range-restriction scenarios is developed that conceptualizes range-restriction scenarios from various combinations of the following facets: (a) the variable(s) on which selection occurs (x, y and/or a 3rd variable z), (b) whether unrestricted variances for the relevant variables are known, and (c) whether a 3rd variable, if involved, is measured or unmeasured. On the basis of these facets, the authors describe potential solutions for 11 different range-restriction scenarios and summarize research to date on these techniques.     

Akaike's Information Criterion and Recent Developments in Information Complexity

In this paper we briefly study the basic idea of Akaike's (1973) information criterion (AIC). Then, we present some recent developments on a new entropic or information complexity (ICOMP) criterion of Bozdogan (1988a, 1988b, 1990, 1994d, 1996, 1998a, 1998b) for model selection. A rationale for ICOMP as a model selection criterion is that it combines a badness-of-fit term (such as minus twice the maximum log likelihood) with a measure of complexity of a model differently than AIC, or its variants, by taking into account the interdependencies of the parameter estimates as well as the dependencies of the model residuals. We operationalize the general form of ICOMP based on the quantification of the concept of overall model complexity in terms of the estimated inverse-Fisher information matrix. This approach results in an approximation to the sum of two Kullback-Leibler distances. Using the correlational form of the complexity, we further provide yet another form of ICOMP to take into account the interdependencies (i.e., correlations) among the parameter estimates of the model. Later, we illustrate the practical utility and the importance of this new model selection criterion by providing several real as well as Monte Carlo simulation examples and compare its performance against AIC, or its variants. Copyright 2000 Academic Press.     

Brain Potentials in the Processing of Complex Sentences: An ERP Study of Control and Raising Constructions

In the present study we made use of Event-Related Potentials (ERPs) to examine raising and subject control constructions in German. Our most salient result is that the ERPs elicited at the empty subject position of a raising construction are clearly different from those elicited at the corresponding position of an otherwise identical subject control construction, the former producing a stronger P600. We argue that this result provides an electrophysiological correlate of the theoretical distinction between NP trace and PRO.     

Hypermnesia: Age-related differences between young and older adults

Hypermnesia is a net improvement in memory performance that occurs across tests in a multitest paradigm with only one study session. Our goal was to identify possible age-related differences in hypermnesic recall. We observed hypermnesia for young adults using verbal (Experiment 1) as well as pictorial (Experiment 2) material, but no hypermnesia for older adults in either experiment. We found no age-related difference in reminiscence (Experiments 1 and 2), though there was a substantial difference in intertest forgetting (Experiments 1 and 2). Older, relative to young, adults produced more forgetting, most of which occurred between Tests 1 and 2 (Experiments 1 and 2). Furthermore, older, relative to young, adults produced more intrusions. We failed to identify a relationship between intrusions and intertest forgetting. We suggest that the age-related difference in intertest forgetting may be due to less efficient reinstatement of cues at test by older adults. The present findings reveal that intertest forgetting plays a critical role in hypermnesic recall, particularly for older adults.     

Effects of antecedent order and semantic context on Chinese pronoun resolution

Three reading time experiments were conducted in order to examine the relative contributions of order of antecedents and semantic context to the resolution of temporarily ambiguous Chinese pronouns. These pronouns were ambiguous because each of them was preceded by two antecedents, both of which were likely candidates for coreference. The identity of the pronoun was revealed by subsequent disambiguating information that constrained the pronoun to one particular interpretation. Experiment 1 showed that reading of the disambiguating phrase was slower when the phrase confined the pronoun to the second rather than to the first antecedent. Experiment 2 produced the same effect of antecedent order (first vs. second antecedent) regardless of whether the target antecedent was an action-performing or an action-receiving entity. In Experiment 3, the order effect was eliminated by a biasing modifier inserted immediately before the pronoun. These results indicate that in a semantically neutral environment, the first-appearing antecedent is the preferred candidate for coreferencing the ambiguous Chinese pronoun. The interaction between order of antecedents and semantic context (in the form of preposed biasing modifiers) suggests that the initial comprehension of Chinese pronouns depends as much on contextual as on structural factors.     

Repeated assessment of the Tower of Hanoi test: reliability and age effects

The purpose of this research was to analyze the effects of repeating an executive function test. Three versions of the Tower of Hanoi (TOH) test were repeated three times each, with test-retest intervals of 2 months. Two groups of children participated in the research (7.7 and 11.6 years, n = 22 and n = 28). Repeating the assessment improved the performance and decreased the total performance time in both of the groups. The older participants improved their performance faster than the younger ones. The reliability of all the scores, besides the error scores, seemed to be satisfactory after the first few assessments. The stability of the scores was maintained through all the assessments. The planning time did not explain the variations of the achieved score. The reasons for the initially low reliabilities are discussed, and modifications for the test administration and scoring are suggested.     

The effects of averaging subjective probability estimates between and within judges

The average probability estimate of J > 1 judges is generally better than its components. Two studies test 3 predictions regarding averaging that follow from theorems based on a cognitive model of the judges and idealizations of the judgment situation. Prediction 1 is that the average of conditionally pairwise independent estimates will be highly diagnostic, and Prediction 2 is that the average of dependent estimates (differing only by independent error terms) may be well calibrated. Prediction 3 contrasts between- and within-subject averaging. Results demonstrate the predictions' robustness by showing the extent to which they hold as the information conditions depart from the ideal and as J increases. Practical consequences are that (a) substantial improvement can be obtained with as few as 2-6 judges and (b) the decision maker can estimate the nature of the expected improvement by considering the information conditions.     

Consequences of right cerebrovascular accident on emotional functioning: diagnostic and treatment implications

The relationship between lesion location and neuropsychiatric sequelae in stroke patients has been extensively studied. Emotional disorders associated with right hemisphere stroke include depression, anxiety, anger, and/or mania. Pharmacotherapy, electroconvulsive therapy, and/or psychotherapy are common treatments for these disorders. This article reviews the clinical presentations of seven right hemisphere stroke patients. The treatment rationale and course of treatment are described for two of these patients. The aims of this paper are to explore the appropriateness of various assessment tools and treatment modalities for stroke patients as well as to demonstrate the techniques of psychotherapy as applied to the two cases featured in this article. Specific factors that may significantly influence treatment outcome, such as lesion location and degree of cognitive impairment, are considered.     

Effects of glucose on scopolamine-induced learning deficits in rats performing the Morris water maze task

In order to assess the effects of glucose on drug-induced spatial learning deficits, three experiments were conducted using the Morris water maze. Scopolamine and glucose were injected ip at various stages of training. Rats of Wistar strain served as subjects. In Experiment 1, scopolamine (0.4 mg/kg) and 10, 100, or 500 mg/kg of glucose were administered every day from the start of training, and the effect on acquisition was evaluated. In Experiment 2, scopolamine and 100 or 500 mg/kg of glucose were administered after 6 days of training, and the effect on performance was assessed. In Experiment 3, scopolamine and 500 mg/kg of glucose were injected after 2 days of training, and the effect on the following trial was tested. In all experiments, scopolamine impaired acquisition/performance of the task. Glucose at 500 mg/kg showed a significant enhancing effect on acquisition regardless of scopolamine injection only when injected daily from the start of training (Experiment 1). Glucose injected after the performance has reached asymptote (Experiment 2) did not affect performance, and glucose in the middle of training showed a slight but insignificant enhancing effect (Experiment 3). These results may suggest that the effect of glucose changes as a function of the degree of learning of the spatial learning task. The possibility of task specificity of the glucose effect was also discussed in relation to the cholinergic systems and local cerebral glucose utilization.