Search PubMed⌕ Search

Biomedical subjects

S J Segalowitz

Publications and source records attributed to S J Segalowitz.

35 records · Page 2Linked to original sources
PubMed1993

The reliability of ERP components in the auditory oddball paradigm.

Nineteen adolescents (average age 15 years, 3 months) were tested and retested using a standard 40 target, auditory oddball ERP paradigm across an interval of 1 year, 10 months to determine reliability of the ERP components, both in terms of intersubject stability and score agreement and in terms of trait (between-session reliability) versus state (within-session reliability). Significant trait stability was found for the N100, P200, and P300 latencies (r = .48, .51, and .74, respectively), and for P300 amplitude (r = .62), supporting the P300 as a reliable measure, with the stability required for group research but not necessarily for clinical applications. Discussion and examples illustrate the application of reliability information to the planning and evaluation of ERP paradigms.

Adolescent↗
PubMed1992

The construct of brain maturation in theories of child development.

Developmental psychologists have avoided using brain maturation as a primary construct in theories of child development for a variety of reasons during the past 40 years. However, during the last decade we have seen a return to considering brain growth as a useful element in theory construction. During the past few years, the frontal lobe has received increasing attention with respect to major developmental issues. In this Introduction, we review some of these historical and contemporary trends.

Brain↗
PubMed1992

Lateral versus frontal ERP predictors of reading skill.

Neuropsychological factors that could account for good versus poor reading skills include hemispheric asymmetry for language, signal processing efficiency, hemisphericity, and frontally based control of attention. Using event-related potential (ERP) measures of these constructs, we find that only hemisphericity accounts for individual differences in reading skill among our 15-year-old good readers, while the frontally generated Contingent Negative Variation attentional ERP accounts for reading skill differences among the poor readers. While good readers show expected hemispheric ERP asymmetries and poor readers do not, this group difference does not account for the variation in reading skill. These data suggest that below some crucial threshold, reading disability is predicted by frontal attentional skill, whereas above this threshold, good reading is better predicted by hemisphericity.

Adolescent↗
PubMed1992

CNV evidence for the distinctiveness of frontal and posterior neural processes in a traumatic brain-injured population.

The association between certain behavioral tests of executive functions in humans and the integrity of the prefrontal lobes has rested primarily on studies comparing subjects with frontal versus other loci of damage. Another approach is to compare the within-group variation on a physiological index of frontal functioning with the behavioral tests of interest. In the present study, subjects with traumatic brain injury (TBI) were given four behavioural measures of executive function, two measures of posterior nonexecutive function, and a Contingent Negative Variation (CNV) task, a proposed electrophysiological index of frontal-lobe functioning. We found that three of the four executive function tests were significantly related to the CNV, accounting for 23-52% of the variance, while the CNV did not correlate at all with the posterior tasks.

Adolescent↗
PubMed1991

Mild head injury as a source of developmental disabilities.

The hospital-reported incidence of mild head injury among children indicates a prevalence of 2% to 3% in high-school-aged adolescents (14 to 18 years). Yet, our survey of 616 high school adolescents suggests that light and mild head injury (not necessarily leading to hospital admission) is almost 10 times this level. Despite the common notion that such injury is generally benign, we found significant relationships in our sample between reported head injury and hyperactivity, stuttering, mixed handedness, and dislike of mathematics.

Adolescent↗
PubMed1989

Right hemisphere EEG sensitivity to speech.

Recent speech perception work with normals and aphasics suggests that the right hemisphere may be more adept than the left at making the voicing discrimination, and the reverse for place of articulation. We examined this right hemisphere voicing effect with natural speech stimuli: stop consonants in pre-, mid-, and postvocalic contexts. Using a neuroelectric event-related potential paradigm, we found numerous effects indicating bilateral components reflecting the voicing and place contrast and unique right hemisphere discrimination of both voicing and place of articulation.

Adult↗
PubMed1985

Music draws attention to the left and speech draws attention to the right.

Providing free-field music input prompts right-handers to attend to their left side in a loudness-matching task that requires no musical analysis. Conversely, speech prompts rightward attention. The processes inferred are akin to the attentional asymmetry demonstrated in the syndrome of hemispatial neglect.

Adult↗
PubMed1980

Use of fetal heart rate, other perinatal and maternal factors as predictors of sex.

The purpose of this study was to examine thi hypothesis that in humans the sex of the fetus can be determined by fetal heart rate. Data were collected from 250 male and 250 female births on a number of perinatal and maternal variables that could affect fetal heart rate. The measures included (1) the sex of the child, (2) the fetal heart rate ausculated numerous times from admission to the hospital until the administration of obstetrical drugs, (3) the weight and length of the neonate, (4) the birth order of the child, (5) the maternal heart rate, (6) the weight gain of the mother during pregnancy, (7) the weight and age of the mother. Data from 41 families in which one child of each sex had been born were also compiled. The data did not support the hypothesis; the inclusion of the other variables in the analysis did not improve the correlation. Explanations are suggested for the results and the origin of the hypothesis.

Body Weight↗
PubMedDate not supplied

Task complexity and habituation effects on frontal P300 topography.

The P3(00) event-related potential (ERP) component is usually reported as having a centroparietal maximum. However, the P3 topography is more frontal in early-session trials which may be masked by averaging over the entire session and is evident longer into the test session among elderly subjects. This hyperfrontality is interpreted as a sign of poor prefrontal adaptive functioning. In the present study, P3 amplitude was examined in university students to determine how early a change in amplitude would be evident and the effect of task complexity on the amplitude across electrode sites. ERPs were elicited using a working-memory n-back task where participants pressed a key to target letter presentations in three conditions of increasing complexity. Single-trial ERP waveforms were then averaged in successive sequences of five trials. Results revealed a greater decrease in frontal P3 amplitude compared to the central and parietal P3 after the first block of five target trials until the third block. The results are interpreted as indicating rapid decrease in hyperfrontality with habituation to an easy task. Increases in task complexity (the 2-back paradigm), however, reduced this frontal P3 attenuation. Results support a P3 ERP model of hyperfrontality reflecting short-term adaptive function by the prefrontal cortex.

Adult↗
PubMedDate not supplied

Impulsivity and control of inhibition in Benign Focal Childhood Epilepsy (BFCE).

Childhood epilepsy represents abnormal brain functioning and may affect cognitive functions that depend on the late development of the frontal lobes. This study addresses the possible consequences of benign epilepsy on frontal functions, specifically action regulation and inhibition in the absence of explicit frontal neurological signs. Thirteen children (8 males; 6-12 years old) with benign epilepsy were matched to 13 controls. They performed tasks designed to measure impulsivity and control of inhibition: CPT, Stop Signal Paradigm, Stroop test, and Matching Familiar Figures Test (MFFT). Children with epilepsy made more errors on the MFFT (p < .02), made more errors in the interference condition on the Stroop test (p < .01), and had a longer response time to the Stop Signal (p < .05) than controls, with no differences on nonexecutive functions measures. Thus, children with benign epilepsy have a deficit on some measures of impulsivity and inhibition, which may reflect poor frontal lobe functioning.

Child↗
PubMedDate not supplied

Signal-to-noise ratio sensitivity in ERPs to stimulus and task complexity: different effects for early and late components.

Traditionally, early and late ERP components are evaluated by the latency and amplitude of their components. We investigated their signal-to-noise (S/N) ratio: how well individual ERP trials correlate with their overall averaged ERP. High correlations indicate minimal noise or individual trial variability while low correlations reflect greater trial variability. Continuous EEG activity was recorded from 57 university students during single- and dual-task conditions in a within-subjects paradigm (easy and difficult tone discrimination; with and without verbal working memory task). For early components, the addition of the second task increased the correlations between the individual trials and the averaged ERPs. For the late components, both the addition of the second task and an increase in stimulus difficulty decreased individual trial correlations. Results suggest that the S/N ratio analysis is a useful method for highlighting differences between early and late components associated with stimulus processing manipulations.

Adult↗
PubMedDate not supplied

An EEG coherence test of the frontal dorsal versus ventral hypothesis in N-back working memory.

We examined Goldman-Rakic's conceptualization of working memory (WM) involving modality-specific reverbatory circuits using electrophysiological measures. An n-back WM task, with either spatial information or object information to be remembered, was administered with EEG coherence used to provide a functional measure of corticocortical communication. Support was not found for modality-specific WM systems in this task. Instead, results suggest that there is a circuit that connects dorsal frontal with dorsal parietal areas which is activated during all levels of the WM vigilance task, regardless of the type of stimuli involved. Data also suggest that left frontal areas are sensitive to the level of difficulty of the WM task (0,1,2, and 3-back), as well as familiarity of task demands. Overall, our results support a model that conceptualizes a unitary WM system rather than a system composed of separate WM circuits for different modalities.

Adult↗