Relations among chronic peer group rejection, maladaptive behavioral dispositions, and early adolescents' peer perceptions.

Adolescents' perceptions of peers' relational characteristics (e.g., support, trustworthiness) were examined for subtypes of youth who evidenced chronic maladaptive behavior, chronic peer group rejection, or combinations of these risk factors. Growth mixture modeling was used to identify subgroups of participants within a normative sample of youth (N = 477; 50% female) for whom data had been gathered from fifth grade (M(age) = 10.61) through eighth grade (M(age) = 13.93). Results revealed that both enduring individual vulnerability (i.e., chronic withdrawn or chronic aggressive behavioral dispositions) and interpersonal adversity (i.e., chronic peer group rejection) were linked with either differences or changes in adolescents' perceptions of their peers' supportiveness and trustworthiness across the early adolescent age period.

The effect of electrical stimulation on corticospinal excitability is dependent on application duration: a same subject pre-post test design.

BACKGROUND: In humans, corticospinal excitability is known to increase following motor electrical stimulation (ES) designed to mimic a voluntary contraction. However, whether the effect is equivalent with different application durations and whether similar effects are apparent for short and long applications is unknown. The aim of this study was to investigate whether the duration of peripheral motor ES influenced its effect on corticospinal excitability. METHODS: The excitability of the corticomotor pathway to abductor pollicis brevis (APB) was measured in fourteen health subjects using transcranial magnetic stimulation before, immediately after and 10 minutes after three different durations (20-, 40-, 60-min) of motor ES (30Hz, ramped). This intervention was designed to mimic a voluntary contraction in APB. To control for effects of motor ES on the peripheral elements (muscle fibre, membrane, neuromuscular junction), maximum compound muscle actions potentials (M-waves) were also recorded at each time point. Results were analysed using a repeated measures analysis of variance. RESULTS: Peripheral excitability was reduced following all three motor ES interventions. Conversely, corticospinal excitability was increased immediately following 20- and 40-min applications of motor ES and this increase was maintained at least 20-min following the intervention. A 60-min application of motor ES did not alter corticospinal excitability. CONCLUSIONS: A 20-min application of motor ES that is designed to mimic voluntary muscle contraction is as effective as that applied for 40-min when the aim of the intervention is to increase corticospinal excitability. Longer motor ES durations of 60-min do not influence corticospinal excitability, possibly as a result of homeostatic plasticity mechanisms.

The Child Behavior Scale (CBS) revisited: a longitudinal evaluation of CBS subscales with children, preadolescents, and adolescents.

The Child Behavior Scale (CBS) is a teacher-report instrument that was developed over a decade ago as an alternative to more costly methods for assessing children's behavior and peer relations in school contexts. This investigation was undertaken to clarify how well the CBS achieves its aims with a broader age spectrum of youth (6- to 13-year-olds). Investigative aims were to examine the basic psychometric properties of the CBS and evaluate the construct and criterion-related validity of the CBS's 6 subscales at each of 8 grade levels (Grades 1-8). These aims were examined in a longitudinal investigation with samples of children and their teachers, classmates, and parents. One sample (n = 396) was followed from 1st through 8th grade, and a second sample (n = 100) was recruited in 5th grade, combined with the initial sample, and followed through 8th grade. Results suggest that the majority of the CBS subscales provide trustworthy data about the behavioral and peer relational constructs that this instrument was designed to measure and that the CBS's range of application, or developmental purview as an assessment tool, spans the period from early childhood (age 5) through early adolescence (age 13).