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Difference Scores (difference + score)
Selected AbstractsDegree of discrepancy between self and other-reported everyday functioning by cognitive status: dementia, mild cognitive impairment, and healthy eldersINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 9 2005Sarah Tomaszewski Farias Abstract Background Previous studies show individuals with dementia overestimate their cognitive and functional abilities compared to reports from caregivers. Few studies have examined whether individuals with Mild Cognitive Impairment (MCI) also tend to underestimate their deficits. In this study we examined whether degree of discrepancy between patient and informant-reported everyday functioning was associated with cognitive status. Methods The sample consisted of 111 ethnically diverse community-dwelling older adults (46 Caucasians and 65 Hispanic individuals), which was divided into four diagnostic categories: cognitively normal, MCI-memory impaired, MCI-nonmemory impaired, and demented. Everyday functional abilities were measured using both a self-report and informant-report version of the Daily Function Questionnaire (DFQ). A Difference Score was calculated by subtracting patients' DFQ score from their informants' score. Results DFQ Difference Scores were significantly higher in the demented group compared to normals and both of the MCI groups. However, the Difference Scores for the MCI groups were not significantly different than the normals. Further, while patient reported everyday functioning did not differ among the four diagnostic groups, informant reported functional status was significantly different across all diagnostic groups except MCI-nonmemory impaired vs normals. Performance on objective memory testing was associated with informant-rated but not patient-rated functional status. Demographic characteristics of the patients and informants, including ethnicity, had no association with the degree of discrepancy between raters. Conclusions Although there may be some mild functional changes associated particularly with the MCI-memory impaired subtype, individuals with MCI do not appear to under-report their functional status as can often been seen in persons with dementia. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Reliability of Difference Scores in Populations and SamplesJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2009Donald W. Zimmerman This study was an investigation of the relation between the reliability of difference scores, considered as a parameter characterizing a population of examinees, and the reliability estimates obtained from random samples from the population. The parameters in familiar equations for the reliability of difference scores were redefined in such a way that determinants of reliability in both populations and samples become more transparent. Computer simulation was used to find sample values and to plot frequency distributions of various correlations and variance ratios relevant to the reliability of differences. The shape of frequency distributions resulting from the simulations and the means and standard deviations of these distributions reveal the extent to which reliability estimates based on sample data can be expected to meaningfully represent population reliability. [source] Increasing the Reliability of Ability-Achievement Difference Scores: An Example Using the Kaufman Assessment Battery for ChildrenJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2002John C. Caruso In this study, we focused on increasing the reliability of ability-achievement difference scores using the Kaufman Assessment Battery for Children (KABC) as an example. Ability-achievement difference scores are often used as indicators of learning disabilities, but when they are derived from traditional equally weighted ability and achievement scores, they have suboptimal psychometric properties because of the high correlations between the scores. As an alternative to equally weighted difference scores, we examined an orthogonal reliable component analysis, (RCA) solution and an oblique principal component analysis (PCA) solution for the standardization sample of the KABC (among 5- to 12-year-olds). The components were easily identifiable as the simultaneous processing, sequential processing, and achievement constructs assessed by the KABC. As judged via the score intercorrelations, all three types of scores had adequate convergent validity, while the orthogonal RCA scores had superior discriminant validity, followed by the oblique PCA scores. Differences between the orthogonal RCA scores were more reliable than differences between the oblique PCA scores, which were in turn more reliable than differences between the traditional equally weighted scores. The increased reliability with which the KABC differences are assessed with the orthogonal RCA method has important practical implications, including narrower confidence intervals around difference scores used in individual administrations of the KABC. [source] Neuropsychological correlates of hippocampal and rhinal cortex volumes in patients with mesial temporal sclerosisHIPPOCAMPUS, Issue 8 2003Catherine E. O'Brien Abstract Considerable progress has been made toward understanding the function of the primate rhinal cortex, comprising the entorhinal (ErC) and perirhinal (PrC) cortices. However, translating animal models to human memory has been limited by the technological problems associated with characterizing neural structures in vivo. Functional correlates of hippocampal and rhinal cortex volume changes were examined in a sample of 61 temporal lobe epilepsy patients with mesial temporal sclerosis (MTS; 33 left, 28 right). Patients were administered the Wechsler Adult Intelligence Scale (revised or third edition), the Wechsler Memory Scale (revised or third edition), and a spatial maze task. Neuropsychological data, together with rhinal cortex and hippocampal volumes, collected in our earlier study (O'Brien CE, Bowden SC, Whelan G, Cook MJ, unpublished observations), were analyzed using multiple regression. The only significant predictor of verbal memory function was the difference score between the volume of left hippocampus and the left PrC. Spatial maze scores were predicted by the bilateral sum of ErC volume. The difference score between the left hippocampus and left PrC volumes was the most powerful predictor of verbal episodic memory. Right hippocampal volume was not a significant predictor of nonverbal episodic memory. Verbal and nonverbal semantic memory were not significantly predicted by any combination of rhinal cortex structures. This quantitative study suggests a lateralized or material-specific memory function for the left hippocampus and left PrC, in contrast to the bilateral role of the ErC. The left hippocampus and left PrC appear to act on verbal memory function through an opposing relationship. Finally, differentiation between hippocampal and subhippocampal components in terms of episodic and semantic memory, respectively, could not be supported by the current data. © 2003 Wiley-Liss, Inc. [source] Latent difference score approach to longitudinal trauma researchJOURNAL OF TRAUMATIC STRESS, Issue 6 2006Lynda A. King In this article, the authors introduce a latent difference score (LDS) approach to analyzing longitudinal data in trauma research. The LDS approach accounts for internal sources of change in an outcome variable, including the influence of prior status on subsequent levels of that variable and the tendency for individuals to experience natural change (e.g., a natural decrease in posttraumatic stress disorder [PTSD] symptoms over time). Under traditional model assumptions, the LDSs are maximally reliable and therefore less likely to introduce biases into model testing. The authors illustrate the method using a sample of children who experienced significant burns or other injuries to examine potential influences (i.e., age of child,adolescent at time of trauma and ongoing family strains) on PTSD symptom severity over time. [source] Serial Estimation of Survival Prediction Indices Does Not Improve Outcome Prediction in Critically III Dogs with Naturally Occurring DiseaseJOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue 3 2001DACVECC, DACVIM, Lasely G. King MVB Abstract Objective: The objectives of this study were to test the value of adding serial measurements to the Survival Prediction Index (SPI 2), and to investigate whether time trajectories add predictive information beyond measurements at a single point in time. Design: Prospective clinical trial. Setting: Intensive care unit at a Veterinary Teaching Hospital. Animals: 63 critically ill dogs Interventions: Physiologic data were collected within 24 hours of admission to the ICU (Day 1), and again on Day 3 of hospitalization. Measurements: The first analysis applied the SPI 2 equation on Day 1 and again on Day3. Then a prediction model was re-estimated using Day 1 measurements, and the incremental predictive value of adding Day 1 to Day 3 change scores was evaluated. the third analysis tested the incremental predictive value of change scores in models containing only one prognostic variable. The final analysis compared the re-estimated Day 1 model to an analogously re-estimated Day 3 model. Main Results: Using the SPI 2 equation, the AUC was 7.7% higher using Day 3 measurements than that obtained using Day 1 measurements (P = 0.515). Starting with the re-estimated Day 1 model (AUC = 0.925), forward stepwise addition of the difference score for each variable did not result in an improvement in the AUC. The AUC for the re-estimated Day 1 model was not statistially different from that of the re-estimated model using Day 3 measurements. Conculusion: This study shows no benefit to repeated calculation of the SPI 2 later in hospitalization. [source] The Wilcoxon Signed Rank Test for Paired Comparisons of Clustered DataBIOMETRICS, Issue 1 2006Bernard Rosner Summary The Wilcoxon signed rank test is a frequently used nonparametric test for paired data (e.g., consisting of pre- and posttreatment measurements) based on independent units of analysis. This test cannot be used for paired comparisons arising from clustered data (e.g., if paired comparisons are available for each of two eyes of an individual). To incorporate clustering, a generalization of the randomization test formulation for the signed rank test is proposed, where the unit of randomization is at the cluster level (e.g., person), while the individual paired units of analysis are at the subunit within cluster level (e.g., eye within person). An adjusted variance estimate of the signed rank test statistic is then derived, which can be used for either balanced (same number of subunits per cluster) or unbalanced (different number of subunits per cluster) data, with an exchangeable correlation structure, with or without tied values. The resulting test statistic is shown to be asymptotically normal as the number of clusters becomes large, if the cluster size is bounded. Simulation studies are performed based on simulating correlated ranked data from a signed log-normal distribution. These studies indicate appropriate type I error for data sets with ,20 clusters and a superior power profile compared with either the ordinary signed rank test based on the average cluster difference score or the multivariate signed rank test of Puri and Sen (1971, Nonparametric Methods in Multivariate Analysis, New York: John Wiley). Finally, the methods are illustrated with two data sets, (i) an ophthalmologic data set involving a comparison of electroretinogram (ERG) data in retinitis pigmentosa (RP) patients before and after undergoing an experimental surgical procedure, and (ii) a nutritional data set based on a randomized prospective study of nutritional supplements in RP patients where vitamin E intake outside of study capsules is compared before and after randomization to monitor compliance with nutritional protocols. [source] Genetic basis for the psychostimulant effects of nicotine: a quantitative trait locus analysis in AcB/BcA recombinant congenic miceGENES, BRAIN AND BEHAVIOR, Issue 7 2005K. J. Gill Genetic differences in sensitivity to nicotine have been reported in both animals and humans. The present study utilized a novel methodology to map genes involved in regulating both the psychostimulant and depressant effects of nicotine in the AcB/BcA recombinant congenic strains (RCS) of mice. Locomotor activity was measured in a computerized open-field apparatus following subcutaneous administration of saline (days 1 and 2) or nicotine on day 3. The phenotypic measures obtained from this experimental design included total basal locomotor activity, as well as total nicotine activity, nicotine difference scores, nicotine percent change and nicotine regression residual scores. The results indicated that the C57BL/6J (B6) were insensitive to nicotine over the entire dose,response curve (0.1, 0.2, 0.4 and 0.8 mg/kg). However, the 0.8-mg/kg dose of nicotine produced a significant decrease in the locomotor activity in the A/J strain and a wide and continuous range of both locomotor excitation and depression among the AcB/BcA RCS. Single-locus association analysis in the AcB RCS identified quantitative trait loci (QTL) for the psychostimulant effects of nicotine on chromosomes 11, 12, 13, 14 and 17 and one QTL for nicotine-induced depression on chromosome 11. In the BcA RCS, nicotine-induced locomotor activation was associated with seven putative regions on chromosomes 2, 7, 8, 13, 14, 16 and 17. There were no overlapping QTL and no genetic correlations between saline- and nicotine-related phenotypes in the AcB/BcA RCS. A number of putative candidate genes were in proximity to regions identified with nicotine sensitivity, including the ,2 subunit of the nicotinic acetylcholine receptor and the dopamine D3 receptor. [source] Functional magnetic resonance imaging response to increased verbal working memory demands among patients with multiple sclerosisHUMAN BRAIN MAPPING, Issue 1 2006Lawrence H. Sweet Abstract Multiple sclerosis (MS) patients frequently experience impaired verbal working memory (VWM). Functional magnetic resonance imaging (fMRI) may help identify neural mechanisms underlying these deficits. Neuroimaging studies of healthy adults have characterized responses associated with increased VWM demands during the n-Back task, suggesting that this experimental paradigm could help identify neural correlates of VWM deficits among MS patients. Fifteen MS patients and 15 matched control participants completed the n-Back during whole-brain fMRI. Mean signal during adjacent 0-Back blocks was subtracted, on a voxel-wise basis, from mean signal observed during n-Back blocks. Resulting difference scores for 1-, 2-, and 3-Back were compared across groups and difficulty levels. Signal intensity was positively related to difficulty level in anterior regions, including premotor, supplementary motor, and dorsolateral prefrontal cortices. MS patients exhibited significantly greater intensity in these areas compared to controls during the 1-Back, while portions of the left superior frontal gyrus, cingulate, and parahippocampal gyri were relatively less intense at more difficult levels. MS group responses were slower during the 1-Back and tended to be slower during the 3-Back; however, accuracy did not differ at any level. Lesion load was positively related to only 1-Back activity and unrelated to any performance measure. Results suggest that compensatory activity occurs among MS patients matched on performance accuracy. Furthermore, compensatory activity occurs predominantly in regions associated with VWM, and this may decline relative to controls as task demands increase. These findings may help to explain why MS patient performance decreases as a function of effort on neuropsychological tests. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Emotional availability: Differential predictions to infant attachment and kindergarten adjustment based on observation time and contextINFANT MENTAL HEALTH JOURNAL, Issue 4 2005Zeynep Biringen Two studies are used to illustrate the importance of context and length of time in the use of the Emotional Availability Scales (EAS) to predict aspects of child development. The purpose of the first study was to examine whether prediction of attachment by the EAS is better with increasing amounts of time. We scored emotional availability (EA) every 15 min for a total of 2 hr, with correlations showing an increasingly stronger relation with attachment with increasing time. In addition, difference scores were calculated between the first and the last 15 min for each EAS dimension. The difference score was significantly higher for the insecure group, suggesting that we need more observation time for the prediction of insecure attachments than is the case for the prediction of secure attachments. The second study investigated whether EA is differentially predictive based on context. We explored play contexts versus reunion contexts. We also explored the relations with other indices of child development. Results revealed that some dimensions of EA (e.g., maternal nonhostility) are difficult to detect outside of a stress context. Maternal nonhostility during the reunion (but not the play situation) was correlated with child aggression in the kindergarten classroom. In addition, most dimensions of EA assessed in the reunion context were better predictors of teacher reports of kindergarten adjustment than was EA assessed in the play situation. [source] Self-ratings in Training Programs: An Examination of Level of Performance and the Effects of FeedbackINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 3 2001Sally A. Carless The level of agreement (mean differences and correlations) between self, peer and training staff ratings were examined in this study. The sample consisted of 545 participants who were undertaking a Royal Australian Airforce officer training program. Consistent with previous research there was strong agreement between training staff and peers and weak agreement between self-ratings and ratings by others (training staff and peers). Accuracy of ratings was examined by (a) comparing the mean ratings of outstanding, average and below-average performers; and (b) correlating difference scores with a measure of performance. The findings showed that below-average performers have a less accurate view of themselves compared to outstanding performers. Finally, we examined the effects of negative feedback on self-perceptions. The analyses indicated that after receiving negative feedback, average performers adjusted their self-ratings. Various explanations were proposed together with practical implications for training. [source] If We Produce Discrepancies, Then How?JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 9 2010Testing a Computational Process Model of Positive Goal Revision Within the self-regulation literature on goals, both discrepancy reduction and discrepancy production are considered important theoretical and practical processes. Yet, discrepancy production has only been examined in a limited number of goal-striving contexts, and the analytical strategies employed (e.g., difference scores) are difficult to interpret. This study extends discrepancy production research to multiple goal contexts where the goals are in conflict. Computational modeling and an organizational simulation were used to test a control theory explanation of discrepancy production. The occurrence of discrepancy production in the computational model and participants was assessed using hierarchical linear modeling. Comparing the data from the computational model with participants' data indicated a good fit. Implications of the findings and methods are discussed. [source] The Reliability of Difference Scores in Populations and SamplesJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2009Donald W. Zimmerman This study was an investigation of the relation between the reliability of difference scores, considered as a parameter characterizing a population of examinees, and the reliability estimates obtained from random samples from the population. The parameters in familiar equations for the reliability of difference scores were redefined in such a way that determinants of reliability in both populations and samples become more transparent. Computer simulation was used to find sample values and to plot frequency distributions of various correlations and variance ratios relevant to the reliability of differences. The shape of frequency distributions resulting from the simulations and the means and standard deviations of these distributions reveal the extent to which reliability estimates based on sample data can be expected to meaningfully represent population reliability. [source] Increasing the Reliability of Ability-Achievement Difference Scores: An Example Using the Kaufman Assessment Battery for ChildrenJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2002John C. Caruso In this study, we focused on increasing the reliability of ability-achievement difference scores using the Kaufman Assessment Battery for Children (KABC) as an example. Ability-achievement difference scores are often used as indicators of learning disabilities, but when they are derived from traditional equally weighted ability and achievement scores, they have suboptimal psychometric properties because of the high correlations between the scores. As an alternative to equally weighted difference scores, we examined an orthogonal reliable component analysis, (RCA) solution and an oblique principal component analysis (PCA) solution for the standardization sample of the KABC (among 5- to 12-year-olds). The components were easily identifiable as the simultaneous processing, sequential processing, and achievement constructs assessed by the KABC. As judged via the score intercorrelations, all three types of scores had adequate convergent validity, while the orthogonal RCA scores had superior discriminant validity, followed by the oblique PCA scores. Differences between the orthogonal RCA scores were more reliable than differences between the oblique PCA scores, which were in turn more reliable than differences between the traditional equally weighted scores. The increased reliability with which the KABC differences are assessed with the orthogonal RCA method has important practical implications, including narrower confidence intervals around difference scores used in individual administrations of the KABC. [source] Value Similarities Among Fathers, Mothers, and Adolescents and the Role of a Cultural Stereotype: Different Measurement Strategies ReconsideredJOURNAL OF RESEARCH ON ADOLESCENCE, Issue 4 2009Annette M. C. Roest In research on value similarity and transmission between parents and adolescents, no consensus exists on the level of value similarity. Reports of high-value similarities coexist with reports of low-value similarities within the family. The present study shows that different conclusions may be explained by the use of different measurement strategies. In addition, we demonstrate that measured value similarities may be biased by a cultural stereotype, that is, an indirectly measurable phenomenon outside the family most likely attributed to shared cultural experiences. We examined similarities in 8 social,cultural value orientations among fathers, mothers, and adolescents from 433 Dutch families. Results revealed different outcomes when using ordinary correlations (r), absolute difference scores (d), or profile correlations (q). Similarly, different influences of a cultural stereotype were found when applying different measurement strategies. We discuss which measurement strategies are best used under which circumstances and which role the cultural stereotype plays. [source] Modelling method effects as individual causal effectsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2008Steffi Pohl Summary., Method effects often occur when different methods are used for measuring the same construct. We present a new approach for modelling this kind of phenomenon, consisting of a definition of method effects and a first model, the method effect model, that can be used for data analysis. This model may be applied to multitrait,multimethod data or to longitudinal data where the same construct is measured with at least two methods at all occasions. In this new approach, the definition of the method effects is based on the theory of individual causal effects by Neyman and Rubin. Method effects are accordingly conceptualized as the individual effects of applying measurement method j instead of k. They are modelled as latent difference scores in structural equation models. A reference method needs to be chosen against which all other methods are compared. The model fit is invariant to the choice of the reference method. The model allows the estimation of the average of the individual method effects, their variance, their correlation with the traits (and other latent variables) and the correlation of different method effects among each other. Furthermore, since the definition of the method effects is in line with the theory of causality, the method effects may (under certain conditions) be interpreted as causal effects of the method. The method effect model is compared with traditional multitrait,multimethod models. An example illustrates the application of the model to longitudinal data analysing the effect of negatively (such as ,feel bad') as compared with positively formulated items (such as ,feel good') measuring mood states. [source] Redefining functional models of basal ganglia organization: Role for the posteroventral pallidum in linguistic processing?MOVEMENT DISORDERS, Issue 11 2004Brooke-Mai Whelan PhD Abstract Traditionally the basal ganglia have been implicated in motor behavior, as they are involved in both the execution of automatic actions and the modification of ongoing actions in novel contexts. Corresponding to cognition, the role of the basal ganglia has not been defined as explicitly. Relative to linguistic processes, contemporary theories of subcortical participation in language have endorsed a role for the globus pallidus internus (GPi) in the control of lexical,semantic operations. However, attempts to empirically validate these postulates have been largely limited to neuropsychological investigations of verbal fluency abilities subsequent to pallidotomy. We evaluated the impact of bilateral posteroventral pallidotomy (BPVP) on language function across a range of general and high-level linguistic abilities, and validated/extended working theories of pallidal participation in language. Comprehensive linguistic profiles were compiled up to 1 month before and 3 months after BPVP in 6 subjects with Parkinson's disease (PD). Commensurate linguistic profiles were also gathered over a 3-month period for a nonsurgical control cohort of 16 subjects with PD and a group of 16 non-neurologically impaired controls (NC). Nonparametric between-groups comparisons were conducted and reliable change indices calculated, relative to baseline/3-month follow-up difference scores. Group-wise statistical comparisons between the three groups failed to reveal significant postoperative changes in language performance. Case-by-case data analysis relative to clinically consequential change indices revealed reliable alterations in performance across several language variables as a consequence of BPVP. These findings lend support to models of subcortical participation in language, which promote a role for the GPi in lexical,semantic manipulation mechanisms. Concomitant improvements and decrements in postoperative performance were interpreted within the context of additive and subtractive postlesional effects. Relative to parkinsonian cohorts, clinically reliable versus statistically significant changes on a case by case basis may provide the most accurate method of characterizing the way in which pathophysiologically divergent basal ganglia linguistic circuits respond to BPVP. © 2004 Movement Disorder Society [source] Is dosage of physiotherapy a critical factor in deciding patterns of recovery from stroke: a pragmatic randomized controlled trialPHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2000Dr Cecily Partridge Abstract Background and Purpose The best treatment and management of stroke patients has been shown to be in stroke units by multidisciplinary rehabilitation teams. Since the composition of stroke units differs it is important to know the extent to which the different components contribute to this result. Physiotherapy is one component of most rehabilitation teams and recent systematic reviews have shown that patients with stroke receiving more physiotherapy achieve more recovery from disability. However, information about the actual amounts of physiotherapy needed to achieve this result is not known. Method A pragmatic, randomized, single-blind, controlled trial comparing recovery from disability in subjects receiving the current standard amount of 30 minutes' physiotherapy with those receiving double that amount (60 minutes). The study included measures of physical performance and function, psychological aspects of anxiety and depression, and perceived control over recovery. Results Some 114 subjects were recruited to the study; full six-week data are available for 104 subjects and six-month data for 93 subjects. Comparison of initial to six-week difference scores in the control and intervention groups of the whole sample did not show a significant difference. Scrutiny of the recovery curves of the whole sample showed that, in half the sample, three distinct patterns of recovery were demonstrated. Conclusion These results suggest that doubling the physiotherapy time available for patients in a stroke unit will not provide a measurable benefit for all patients. The subgroup analysis of patterns of recovery must be regarded as speculative, but provides the basis for hypotheses about those likely to respond well to more intensive therapy. Copyright © 2000 Whurr Publishers Ltd. [source] Cognitive effects of hormonal therapy in early stage breast cancer patients: a prospective studyPSYCHO-ONCOLOGY, Issue 8 2009Barbara Collins Abstract Objective: The primary purpose of this study was to evaluate the cognitive effects of adjuvant hormonal therapies in breast cancer patients. Participants and Methods: Post-menopausal breast cancer patients scheduled to receive tamoxifen (n=31) or anastrozole (n=14) completed neuropsychological testing around the time of commencement of treatment (T1), and again 5,6 months later (T2). A sample of healthy female volunteers (n=28) was tested at comparable intervals. A standardized regression-based approach was used to assess cognitive change. This method uses test/retest scores of the healthy control group to generate an equation that predicts T2 scores from T1 scores. The difference between the predicted and obtained T2 scores divided by the standard error of the estimate produces a deviation score that reflects the discrepancy from the T1,T2 difference scores that would be expected on the basis of practice and error alone. Results: Analysis of individual deviation scores revealed that both the patients taking tamoxifen and those taking anastrozole were more likely than healthy controls to show reliable cognitive decline from T1 to T2 (39, 64, and 7%, respectively). Processing speed and verbal memory were the cognitive domains most affected. Conclusion: These data suggest that hormonal therapies exert a subtle negative influence on cognition in breast cancer patients. Further analyses indicated that this effect was not fully accounted for by demographic factors or fatigue. Methodological limitations of the current study are addressed, along with recommendations for future studies in this area. Copyright © 2008 John Wiley & Sons, Ltd. [source] Range of sensory gating values and test,retest reliability in normal subjectsPSYCHOPHYSIOLOGY, Issue 4 2007Darren R. Fuerst Abstract This article characterizes gating in normal subjects using P50, N100, and P200 components in a paired-click paradigm and compares the test,retest reliabilities of the three components. Sixty-seven normal subjects had gating data from a standard paired-click paradigm; 30 had test,retest data. The test,retest reliability of the amplitudes, latencies, and sensory gating indices derived from the P50, N100, and P200 responses were compared. Measured gating ratios showed either normal or positively skewed distributions. Test,retest reliability of the P50 gating ratio did not reach significance, but N100 and P200 ratios showed better reliability (.50 and .64). The P50 difference score was more reliable (.61), and the N100 and P200 test,retest reliabilities of difference scores were high (.83 and .81, respectively). N100 and P200 attenuation is reliable; further work is needed to develop more reliable P50 gating measures. [source] The sensitivity of human event-related potentials and reaction time to mobile phone emitted electromagnetic fieldsBIOELECTROMAGNETICS, Issue 4 2006D.L. Hamblin Abstract There is some evidence to suggest that exposure to mobile phones (MPs) can affect neural activity, particularly in response to auditory stimuli. The current investigation (n,=,120) aimed to test recent findings in this area, namely that N100 amplitude and latency would decrease, and that P300 latency and reaction time (RT) would increase under active relative to sham exposure during an auditory task. Visual measures were also explored. A double blind, counterbalanced, crossover design was employed where subjects attended two sessions 1 week apart. In both sessions participants (1) performed auditory and visual oddball tasks while electroencephalogram (EEG) was recorded with a MP set to sham exposure mounted over the temporal region, and (2) performed the same tasks while the handset was set to active/sham. When active, the MP transmitted for 30 min at 895 MHz (average power 250 mW, pulse modulated at 217 Hz, average SAR 0.11 W/kg). Paired t -tests compared difference scores from the sham/sham session to those from the sham/active condition. The study was designed to detect differences of of a standard deviation with a power of 0.80. There was no significant difference between exposure conditions for any auditory or visual event related potential (ERP) component or RT. As previous positive findings were not replicated, it was concluded that there is currently no evidence that acute MP exposure affects these indices of brain activity. Bioelectromagnetics 27:265,273, 2006. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||||||||