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Biomedical subjects

A M Albano

Publications and source records attributed to A M Albano.

At least 19 recordsLinked to original sources
PubMed2005

Statistical validation of mutual information calculations: comparison of alternative numerical algorithms.

Given two time series X and Y , their mutual information, I (X,Y) = I (Y,X) , is the average number of bits of X that can be predicted by measuring Y and vice versa. In the analysis of observational data, calculation of mutual information occurs in three contexts: identification of nonlinear correlation, determination of an optimal sampling interval, particularly when embedding data, and in the investigation of causal relationships with directed mutual information. In this contribution a minimum description length argument is used to determine the optimal number of elements to use when characterizing the distributions of X and Y . However, even when using partitions of the X and Y axis indicated by minimum description length, mutual information calculations performed with a uniform partition of the XY plane can give misleading results. This motivated the construction of an algorithm for calculating mutual information that uses an adaptive partition. This algorithm also incorporates an explicit test of the statistical independence of X and Y in a calculation that returns an assessment of the corresponding null hypothesis. The previously published Fraser-Swinney algorithm for calculating mutual information includes a sophisticated procedure for local adaptive control of the partitioning process. When the Fraser and Swinney algorithm and the algorithm constructed here are compared, they give very similar numerical results (less than 4% difference in a typical application). Detailed comparisons are possible when X and Y are correlated jointly Gaussian distributed because an analytic expression for I (X,Y) can be derived for that case. Based on these tests, three conclusions can be drawn. First, the algorithm constructed here has an advantage over the Fraser-Swinney algorithm in providing an explicit calculation of the probability of the null hypothesis that X and Y are independent. Second, the Fraser-Swinney algorithm is marginally the more accurate of the two algorithms when large data sets are used. With smaller data sets, however, the Fraser-Swinney algorithm reports structures that disappear when more data are available. Third, the algorithm constructed here requires about 0.5% of the computation time required by the Fraser-Swinney algorithm.

Journal Article↗
PubMed2003

Comment on "Performance of different synchronization measures in real data: a case study on electroencephalographic signals".

Quian Quiroga et al. [Phys. Rev. E 65, 041903 (2002)] reported a similar performance of several linear and nonlinear measures of synchronization when applied to the rat electrocorticogram (ECoG). However, they found that the mutual information measure did not produce robust estimates of synchronization when compared to other measures. We reexamined their data using a histogram method with adaptive partitioning and found the mutual information to be a useful measure of regional ECoG interdependence.

Comment↗
PubMed2003

Comparative study of embedding methods.

Embedding experimental data is a common first step in many forms of dynamical analysis. The choice of appropriate embedding parameters (dimension and lag) is crucial to the success of the subsequent analysis. We argue here that the optimal embedding of a time series cannot be determined by criteria based solely on the time series itself. Therefore we base our analysis on an examination of systems that have explicit analytic representations. A comparison of analytically obtained results with those obtained by an examination of the corresponding time series provides a means of assessing the comparative success of different embedding criteria. The assessment also includes measures of robustness to noise. The limitations of this study are explicitly delineated. While bearing these limitations in mind, we conclude that for the examples considered here, the best identification of the embedding dimension was achieved with a global false nearest neighbors argument, and the best value of lag was identified by the mutual information function.

Journal Article↗
PubMed2001

Screening for anxiety and depression in early adolescence.

OBJECTIVE: To examine the level of diagnostic and discriminative accuracy of three dimensional rating scales for detecting anxiety and depressive disorders in a school-based survey of 9th grade youths. METHOD: Classroom screening instruments, the Center for Epidemiologic Studies-Depression Scale (CES-D), the Revised Children's Manifest Anxiety Scale (RCMAS), and the Multidimensional Anxiety Scale for Children (MASC) were administered to 632 youths from three sites in 1998. On the basis of rating scale results, samples of high-scoring and non-high-scoring youths were invited to participate in a diagnostic interview conducted within 2 months of the screening sessions. RESULTS: MASC scores were most strongly associated with individual anxiety disorders, particularly among females, whereas the CES-D composite score was associated with a diagnosis of major depression, after controlling for comorbid disorders. The RCMAS was least successful in discriminating anxiety and depression. When receiver operator characteristic curves were examined, diagnostic accuracy was moderate. CONCLUSIONS: The ability of the MASC and CES-D to discriminate within and between categorically defined diagnostic groups has important implications for the accurate identification of youths in need of services.

Adolescent↗
PubMed2001

Current trends in the understanding and treatment of social phobia in youth.

Social phobia is a common psychiatric problem in children and adolescents that has recently gained serious attention in clinical practice and research. This article describes the clinical presentation of social phobia and reviews several emergent areas of related research to social phobia in children and adolescents. We begin with a summary of research regarding the developmental pathways of childhood social anxiety into social phobia, highlighting normative developmental factors, behavioral inhibition, pathophysiology, genetics, and parenting/environmental factors. This is followed by a critical review of findings from studies providing evidence for and against the existence of subtypes of social phobia. Common comorbid disorders and sequelae of social phobia in children and adolescents are discussed, bringing to attention the critical need for effective treatments, the current status of which is reviewed in the final section. In sum, this review demonstrates that through research in multiple disciplines, scientists are now developing a better understanding of the risk and protective factors of social phobia in children and adolescents, ultimately leading to improvements in primary prevention and intervention efforts for children at serious risk for long-term problems with education, employment, social relationships, and independent adult functioning.

Activities of Daily Living↗
PubMed2000

Cognitive-behavioral group therapy for social phobia in female adolescents: results of a pilot study.

OBJECTIVES: To examine the efficacy of cognitive-behavioral group therapy for adolescents (CBGT-A) in females with social phobia and the effect of this treatment on the risk for major depression. METHOD: Female adolescents with social phobia (N = 35) were randomly assigned to treatment (n = 12) or no treatment (n = 23) groups. Assessments were conducted at baseline, after treatment, and at a 1-year follow-up. RESULTS: Eleven subjects completed treatment. Sixteen weeks of treatment produced a significant improvement in interference and reduction in symptoms of social anxiety. There was a significant reduction in the number of subjects meeting DSM-IV criteria for social phobia in the CBGT-A versus the untreated group; however, at the 1-year follow-up there were no significant differences by treatment condition. There was also suggestive evidence that treatment of social phobia lowers the risk for relapse of major depression among those with a history of major depression. Combining social phobia and major depression as the outcome produced more robust treatment effects in the 1-year follow-up. CONCLUSIONS: This pilot study provides evidence for a moderate short-term effect of CBGT-A for treating female adolescents suffering from social phobia and indicates that treatment of social phobia may result in a reduction of major depression.

Adolescent↗
PubMed1999

Subtypes of social phobia in adolescents.

Thirty-three social phobic adolescents were asked to name their ten most feared social situations. Two independent judges classified each situation reported by the participants into one of four situational domains: formal speaking/interactions, informal speaking/interactions, observation by others, and assertion. Fifteen participants (45.5%) were assigned a generalized subtype of social phobia because they endorsed at least moderate anxiety in all four situational domains. This subgroup scored higher on self-report measures of anxiety and depression than the rest of the sample. These results provide empirical support for the existence of subtypes of social phobia in adolescents.

Adolescent↗
PubMed1998

Cross-informant agreement in the assessment of social phobia in youth.

In the present study involving children and adolescents with a principal diagnosis of social phobia, we measured parent-child agreement regarding social anxiety symptoms. Additionally, we examined variables related to the severity of the children's social phobia symptoms as reported by children and as rated by clinicians. Examination of cross-informant agreement indicated little difference between mean parent and children ratings of the children's social fears. In contrast, there was a significant difference in parent and children ratings of the children's avoidance, with parents endorsing greater degrees of social avoidance. Children's report of social avoidance was negatively related to scores on a measure of self-presentational concerns (i.e., social desirability). Clinicians' determination of the severity of the children's social phobia was also influenced by the children's self-presentation as well as parent report of social avoidance and children's depression scores. Thus, this differential weighting by the clinician of parent versus child report may be related to the finding that children's self-reported social avoidance was negatively related to their concerns regarding positive self-presentation. Results suggest the need to consider the impact of social desirability when examining clinical characteristics of children and adolescents with social phobia.

Adolescent↗
PubMed1998

Methodological strategies in child clinical trials: advancing the efficacy and effectiveness of psychosocial treatments.

The present paper reviews issues of treatment efficacy (i.e., potency) and effectiveness (i.e., clinical utility) in applied clinical child research. Threats to treatment evaluation are reviewed in the context of these two dimensions. It is proposed that treatment outcome research faces new challenges stemming from the ever increasing emphasis on generalization of gains and dissemination of interventions outside of clinical research settings. Issues and approaches proposed as warranting further development and attention include development, flexibility, acceptability, and disseminability of psychosocial assessment and treatment methods. A research emphasis is promoted that balances experimental control with the need for treatment generalization and delivery outside of the research setting, in order to maximize the utility of clinical research.

Child↗
PubMed1998

The structure of negative emotions in a clinical sample of children and adolescents.

The authors sought to define the latent factors associated with childhood anxiety and depression, using a structural equations/confirmatory factor-analytic approach involving multiple informants (i.e., parent and child report) of symptoms. A sample of 216 children and adolescents with diagnoses of an anxiety disorder or comorbid anxiety and mood disorders and their parents were administered measures of childhood fear, anxiety, and depression. Results of comparative modeling best supported 3-factor solutions (fear, anxiety, and depression) that were consistent with recent conceptual models of anxiety and depression (e.g., tripartite model). Results also suggested that 3 widely used measures of childhood negative emotion are conceptually heterogeneous (containing item sets that loaded on different latent factors). Implications for the assessment of childhood negative emotions are discussed.

Adolescent↗
PubMed1996

A systematic replication of the prescriptive treatment of school refusal behavior in a single subject.

We employed a multiple-baseline design to test the efficacy of a recently developed approach for reducing school refusal behavior. This approach uses a systematic method for conducting a functional analysis for the target behaviors and suggests specific intervention strategies based upon this analysis. To maximize external validity, the intervention was tested using a systematic replication strategy, whereby only the major conceptual elements of the intervention were retained from previous applications. The subject was a 10 year old girl who attended school with great difficulty and resistance and who was assigned DSM-III-R diagnoses of separation anxiety disorder and social phobia prior to treatment. Following 8 weeks of treatment, she showed marked reductions in problem behavior and no longer met criteria for any anxiety disorder diagnoses. The results highlight the importance of the use of functional analytic strategies to effect behavior change.

Anxiety, Separation↗
PubMed1995

Cognitive-behavioral group treatment for social phobia in adolescents. A preliminary study.

The present study is a preliminary evaluation of the effectiveness of a new cognitive-behavioral group treatment protocol for social phobia in adolescents. Five adolescents with social phobia were treated in a 16-session group treatment program, with parental involvement in selected sessions. Treatment involved skills training (social skills, problem solving, assertiveness), cognitive restructuring, behavioral exposure, and homework. Self-report measures of anxiety and depression, taken throughout treatment, indicated significant improvements over a 1-year follow-up period. Behavior test measures also indicated a decrease in subjective anxiety ratings after treatment which was maintained at follow-up. Structured diagnostic interviews 1 year after treatment confirmed full remission of social phobia for four subjects, with one subject's phobia in partial remission. Overall, the present findings support the continued evaluation of this protocol for social phobic adolescents.

Adolescent↗
PubMed1995

Treatment of anxiety disorders of childhood.

The development of empirically derived, efficacious treatment methods for the range of anxiety disorders in children and adolescents lags far behind the field of adult anxiety treatment research. Controlled trials of both psychosocial and pharmacologic methods are warranted, and several trials are currently underway. Although the literature in this field is growing, many questions remain regarding the application and long-term benefit of interventions with youth. Specifically, although the field of adult psychosocial treatment research has advanced such that empirically derived treatment protocols are readily available, such methodologies are lacking for anxious youth. Serious attention must turn toward the empirical testing and validation of developmentally appropriate psychosocial treatment protocols. Fortunately, work in this area is currently under way in several centers (e.g., for social phobia, OCD, and generalized anxiety). Moreover, the role of parents in the psychosocial treatment process remains largely unexplored. Investigations are underway examining the effectiveness of training parents in the delivery of particular psychosocial procedures and evaluating the optimal "degree" of parental involvement. Attention also must turn to the systematic study of variables hypothesized to affect negatively the successful integration of parents (e.g., age of child, severity of disorder, parental psychopathology). And lastly, combined trials of pharmacologic compounds and psychosocial interventions are needed to examine the prescriptive treatment approach of matching patients to treatments.

Adolescent↗
PubMed1994

The algorithmic complexity of neural spike trains increases during focal seizures.

The interspike interval spike trains of spontaneously active cortical neurons can display nonrandom internal structure. The degree of nonrandom structure can be quantified and was found to decrease during focal epileptic seizures. Greater statistical discrimination between the two physiological conditions (normal vs seizure) was obtained with measurements of context-free grammar complexity than by measures of the distribution of the interspike intervals such as the mean interval, its standard deviation, skewness, or kurtosis. An examination of fixed epoch data sets showed that two factors contribute to the complexity: the firing rate and the internal structure of the spike train. However, calculations with randomly shuffled surrogates of the original data sets showed that the complexity is not completely determined by the firing rate. The sequence-sensitive structure of the spike train is a significant contributor. By combining complexity measurements with statistically related surrogate data sets, it is possible to classify neurons according to the dynamical structure of their spike trains. This classification could not have been made on the basis of conventional distribution-determined measures. Computations with more sophisticated kinds of surrogate data show that the structure observed using complexity measures cannot be attributed to linearly correlated noise or to linearly correlated noise transformed by a static monotonic nonlinearity. The patterns in spike trains appear to reflect genuine nonlinear structure. The limitations of these results are also discussed. The results presented in this article do not, of themselves, establish the presence of a fine-structure encoding of neural information.

Algorithms↗