Offline improvement occurs for temporal stability but not accuracy following practice of integer and non-integer rhythms

Procedural learning benefits from memory processes occurring outside practice resulting in offline learning. Offline gains have been demonstrated almost exclusively for the ordinal structure of sequential motor tasks. Many skills also demand that the correct serial order of events be appropriately timed. Evidence indicates that the temporal aspect of a procedural skill can be encoded independent of serial order knowledge and governed by at least two distinct neural circuits. The present experiment determined if (a) offline gains emerge for temporal learning, and (b) if such gains occur for timing supervised by distinct timing systems. Participants experienced 216 practice trials of a 7-key press sequence that involved integer- or non-integer timing rhythms. Twenty-four hours after training 30 test trials were administered. Results revealed robust offline enhancement for timing performance of the non-integer based temporal sequences. This improvement was localized to stabilization of the required relative but not absolute time profiles. The neural circuitry central to supporting the performance of non-integer timing sequences is also a principal constituent of what is described as the "cognitive" timing system. Timing governed by this system appears most susceptible to offline gains via consolidation.     

Offline Improvement during Motor Sequence Learning Is Not Restricted to Developing Motor Chunks

Robust offline performance gains, beyond those that would be anticipated by being exposed to additional physical practice, have been reported during procedural learning and have been attributed to enhancement consolidation, a process by which memory is transformed in such a way that it is not only more resistant to forgetting but may also involve a reorganization of information that supports superior task execution. The authors assessed the impact of increasing within-session practice extent on the emergence of offline performance gains. Practice-dependent improvements occurred across 12 and 24 30-s practice trials of a 5-element motor sequencing task. Offline improvements were observed following both 12 and 24 trials. The improvement following 12 trials was associated with the formation of motor chunks important for establishing movement sequence structure. In contrast, the offline improvement after 24 trials was not related to further changes in movement structure beyond those that had emerged during practice. These data suggest that additional memory operations, beyond those needed to amalgamate subsequences of the SRT task, are susceptible to enhancement consolidation.     

Test of Alternative Hypotheses Explaining the Comorbidity Between Attention-Deficit/Hyperactivity Disorder and Conduct Disorder

There is significant comorbidity between attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD). The conclusions of studies that examined the causes of comorbidity between ADHD and CD conflict, with some researchers finding support for the three independent disorders model and others finding support for the correlated risk factors model. We tested these models and eleven alternative hypotheses using the same analytical approach. The participants were 110 monozygotic twin pairs and 181 dizygotic twin pairs recruited from the Colorado Learning Disabilities Research Center Twin Study. The three independent disorders model did not fit the data, whereas the correlated risk factors model fit the data well. Several other comorbidity models fit the data as well as or better than the correlated risk factors model. The results suggest that correlated risk factors are a better explanation for the comorbidity between ADHD and CD than a third, independent ADHD+CD subtype.     

Common Genetic and Environmental Influences on Major Depressive Disorder and Conduct Disorder

The evidence for common genetic and environmental influences on conduct disorder (CD) and major depressive disorder (MDD) in adolescents was examined. A sample of 570 monozygotic twin pairs, 592 dizygotic twin pairs, and 426 non-twin siblings, aged 12-18 years, was recruited from the Colorado Twin Registry. For the past year data, there was a significant correlation between the genetic influences on MDD and CD and, for the lifetime data, there was a significant correlation between the genetic influences on MDD and CD, and a significant correlation between the nonshared environmental influences on MDD and CD. Our results suggest that some genetic factors will increase an individual's vulnerability to both MDD and CD in adolescence.     

The Relationship Between Caregiver Capacity and Intensive Community Treatment for Children with a Mental Health Crisis

We studied 9,220 children referred to a comprehensive mental health crisis stabilization program to examine the impact of caregiver capacity on crisis worker decisions to refer children for intensive community-based treatment as opposed to inpatient psychiatric hospitalization. Due to the different role of caregivers in the child welfare system, analyses were stratified by state custody status. Among both groups, there was a significant inverse association between child mental health need and referral to intensive community-based treatment. For children not in state custody with low mental health need, there was no difference in the likelihood of referral to intensive community-based treatment across levels of caregiver capacity. However, for children not in state custody with medium and high mental health needs, those whose caregivers were deficient or severely deficient were significantly more likely to be referred for intensive community-based treatment than were those who had capable caregivers. Multivariate analyses demonstrated similar results after controlling for potential confounding variables and confirmed that caregiver capacity contributes significantly to the logistic model’s classification accuracy. Results suggest further investigation of the impact of caregiver capacity on mental health crisis worker referral decisions is needed.     

Differences Between Korean and Japanese Processing Overload

We report the results of a pilot questionnaire study which indicates a difference between Japanese and Korean in the processing of twice center-embedded transitive sentences. Babyonyshev and Gibson (1995) claimed that, in Japanese, these structures are significantly more difficult to parse than twice center-embedded intransitives. Our study showed that, in Korean, this difference in processing difficulty does not obtain. We suggest that the difference between Japanese and Korean processing should be attributed to short-term memory effects on repetition of case markers and to differences in the syntax of the two languages with respect to verb movement.     

Ethnic identity as a predictor of problem behaviors among Korean American adolescents

This study examined three dimensions of ethnic identity (level of ethnic identity, attitudes toward other groups, and perceived discrimination) as predictors of adolescent problem behaviors among Korean American adolescents. Multiple regression analyses were carried out, and the results indicated that level of ethnic identity, perceived discrimination, and academic performance were significant predictors of both internalizing and externalizing problems. Implications for the provision of mental health services and strengthening multicultural education are discussed.