Interhemispheric transfer time and structural properties of the corpus callosum.

The present study examined how interhemispheric transfer time (IHTT) is affected by interindividual differences in corpus callosum (CC) architecture. For this purpose the CC of 42 healthy male subjects was assessed by applying a combination of morphological and diffusion-tensor magnetic resonance imaging to characterize the CC on macro- (midsagittal area) and microstructural level (mean diffusion, fractional anisotropy). Following the so-called Poffenberger paradigm, IHTT was determined with both reaction time measures and event-related potentials recorded in response to stimuli briefly presented to either left or right visual hemifield. Statistical analysis revealed significant negative correlations between mean diffusion and IHTT estimates derived from the P100 component (at O1/O2 electrode pair), particularly in the posterior CC subregion. Interpreting mean diffusion as an index of microstructural tissue properties, IHTT appears to be directly related to the structural integrity of the posterior CC.

The role of the corpus callosum in dichotic listening: a combined morphological and diffusion tensor imaging study.

The objective of the present study was to examine the role of the corpus callosum (CC) in dichotic listening. For this purpose, 40 right-handed healthy male participants were assessed with morphological and diffusion tensor imaging, which yielded macrostructural (midsagittal area) and microstructural (mean diffusion, fractional anisotropy) measures of the total CC and predefined subregions. Applying the standard consonant-vowel Bergen Dichotic Listening Test (including 3 different attentional instructions), the authors found dichotic listening performance to be substantially related to the integrity of the CC at both macro- and microstructural levels. Results indicate a dual role of the CC; it is relevant not only for the stimulus-driven (bottom-up) transfer of left-ear input to the left hemisphere but also for its attentional (top-down) modulation.

The association of macro- and microstructure of the corpus callosum and language lateralisation.

The present study aimed to examine how differences in functional lateralisation of language are related to interindividual variations in interhemispheric connectivity. Utilising an fMRI silent word-generation paradigm, 89 left- and right-handed subjects were subdivided into four lateralisation subgroups. Applying morphological and diffusion-tensor MRI, midsagittal cross-sectional area as well as quantitative measures of molecular diffusion (anisotropy, mean diffusion) of the corpus callosum were determined to assess interhemispheric connectivity. Statistical analyses revealed group differences in molecular diffusion but not in callosal size, which may be interpreted to reflect a stronger and/or faster interhemispheric connection in strongly left-lateralised subjects as compared to moderately left-lateralised, bilateral, or moderately right-lateralised subjects.

Handedness, dichotic-listening ear advantage, and gender effects on planum temporale asymmetry--a volumetric investigation using structural magnetic resonance imaging.

Previous research has often examined whether the asymmetrical structure of the planum temporale (PT) represents an anatomical correlate of lateralized language-processing functions, gathering diverging empirical evidence by comparing PT asymmetry in subjects with differing handedness, gender, or speech lateralization. Apart from other methodological problems, direct comparisons between studies are hampered by insufficient assessment and consideration of all three potential determinants of structural cerebral asymmetry. Based on volumetric assessment of structural Magnetic Resonance Imaging (MRI) scans of 104 healthy subjects, the present study replicated earlier observations of an overall leftward PT asymmetry, which was found to prevail irrespective of handedness, gender, or dichotic-listening ear advantage. However, the mean magnitude of this leftward asymmetry was not determined by either one of these factors in itself, but varied depending on their specific combination. A clear correspondence between structural and functional asymmetry was only observed among right-handed males. In this particular subgroup, more pronounced structural asymmetry was associated with an enlarged PT on the left side, while the enhanced leftward asymmetry of female sinistrals resulted from smaller adjusted volumes of their right PT. The existence of such complex interactions suggests that future research in this area can only be expected to overcome past inconsistencies by adequately considering handedness, gender, and speech lateralization.

Effects of handedness and gender on macro- and microstructure of the corpus callosum and its subregions: a combined high-resolution and diffusion-tensor MRI study.

The corpus callosum (CC) represents the major commissural tract connecting the two cerebral hemispheres and is supposed to play crucial integrative role in functional hemispheric specialization. The present study examined whether interindividual variations in macro- and microstructure of the human CC are associated with handedness and gender. Therefore, a combined diffusion-tensor (DTI) and high-resolution morphological MRI study was performed on 34 right- and 33 left-handed subjects of both sexes. The mid-sagittal surface areas and quantitative measures of molecular diffusion (relative anisotropy, mean diffusion) of the total CC and its subregions (genu, truncus, posterior third) were determined. Analysis revealed a larger total callosal area in right- as compared to left-handed subjects and in males as compared to females. Throughout all callosal subregions, anisotropy was found to be increased in left-handed as well as in male subjects, while the mean diffusion was diminished only in left-handers. For the posterior third of the CC, a significant negative correlation (r=-0.34) between anisotropy and area was detected in right-handed subjects. Summarized, significant alterations in the molecular diffusion and in the size of the CC with respect to gender and handedness were revealed in the present study. These findings can be interpreted as handedness- and gender-related differences in macro- and microstructure of the callosal pathways. It was demonstrated that the inspection of the callosal microstructure using DTI yields empirical evidence on interhemispheric connectivity that goes well beyond the information revealed by anatomical measurements alone. Thus, DTI has proven to be a useful additional method in cognitive neuroscience.

Normative data and scale properties of the German parent SDQ.

BACKGROUND AND OBJECTIVES: The Strengths and Difficulties Questionnaire (SDQ) is a short assessment instrument which addresses positive and negative behavioural attributes of children and adolescents and generates scores for clinically relevant aspects. Although this brief questionnaire has been widely used in Germany to gather information from parents, teachers, and older children themselves, normative results obtained with the German version have not yet been reported to the international scientific community. To allow comparisons with SDQ findings in other countries, normative data for the German parent-rated form as well as a community-based evaluation of scale properties are summarised and complemented by results obtained in a number of clinical samples. METHODS: Parent ratings were collected for a community-based sample of 930 children and adolescents aged between 6 and 16 years, in which both genders and all age levels were equally represented. Statistical evaluation of psychometric properties included a factor analysis verifying the proposed scale structure, assessment of scale homogeneities, and determination of age, gender and social class effects. Based on the distributions of SDQ scores observed in this normative sample, recommended bandings identifying normal, borderline, and clinical ranges were defined for each scale. RESULTS: Exact replication of the original scale structure, satisfactory internal reliabilities, and observation of the expected associations with age and gender confirmed the equivalence of the German SDQ parent questionnaire with the English original. Differences between community-based results and clinical groups provided descriptive evidence of a dramatic impact of clinically defined psychiatric status on SDQ scores. CONCLUSIONS: After evaluating parent ratings obtained in a community-based sample, the German SDQ was shown to possess favourable psychometric properties. Thus, the German translation of this popular and versatile instrument seems to be a similarly reliable and useful assessment tool as the original English questionnaire.

Validation of the parent and teacher SDQ in a clinical sample.

OBJECTIVES: This study examines whether the German translation of the Strengths and Difficulties Questionnaire (SDQ) is a reliable and valid screening instrument and whether it is as effective a tool for clinical diagnostics and scientific applications as the CBCL/TRF. METHODS: We examined 543 children and adolescents (147 girls and 396 boys) with ages ranging from 5 to 17 years and correlated the results of the parent and teacher SDQ as well as the CBCL/TRF with clinical diagnoses. Furthermore, the adequacy of the scale structure of the SDQ was tested using confirmatory and exploratory factor analyses. RESULTS: It was demonstrated that the scales of the parent and teacher versions were sufficiently homogeneous (0.72-0.83). Correlations between SDQ scales and corresponding CBCL/TRF scales showed a high degree of congruence, while an exact replication of the original SDQ scale structure could also be achieved. Parent and teacher versions of both questionnaires presented with good validity, not only with regard to the discrimination between child psychiatric patients and a representative community sample, but also in the identification of different categories of disorders within the clinical sample. CONCLUSION: The parent and teacher SDQs proved to be valid and helpful questionnaires for use in the framework of a multi-dimensional behavioural assessment, and appear to be well suited for screening purposes, longitudinal monitoring of therapeutic effects, and scientific research purposes.

Evaluation of the self-reported SDQ in a clinical setting: do self-reports tell us more than ratings by adult informants?

OBJECTIVES: The aim of this study was to evaluate the German self-reported Strengths and Difficulties Questionnaire (SDQ) in a clinical setting. We also investigated whether this additional information gathered directly from older children and adolescents improves the prediction of clinical status when external ratings from their parents and/or teachers are already available. METHODS: SDQ self-reports were collected from 214 in- and outpatients (81 girls and 133 boys) aged 11 to 17 years who were seen at the department of child and adolescent psychiatry of the University of Göttingen. Results obtained with the self-rated questionnaire were compared with the parent and teacher SDQs, corresponding CBCL/YSR scores, and the clinical diagnostic classification. Finally, the additional diagnostic benefits of the self-reports were examined. RESULTS: The scales of the SDQ self-report proved to be sufficiently homogeneous, and acceptable correlations were found with the equivalent parent and teacher ratings. The self-rated version of the SDQ demonstrated good validity with respect to the differentiation between clinically defined cases and non-cases and in detecting various subcategories of psychiatric disorders within the clinic sample. SDQ self-reports significantly contributed to the prediction of diagnostic status, specifically if only parent or teacher ratings were available. CONCLUSIONS: The self-rated version of the SDQ was shown to be a reliable and valid method for the assessment of behavioural problems in children and adolescents. In the absence of adult informant reports from parents and teachers, the diagnostic value of self-ratings was also demonstrated.

The Strengths and Difficulties Questionnaire overseas: evaluations and applications of the SDQ beyond Europe.

BACKGROUND: During the few years that have passed since it became available, the Strengths and Difficulties Questionnaire (SDQ) has been extensively evaluated and widely applied to assess behaviour disorders of children and adolescents in European countries. In contrast, relatively few reports have published SDQ results obtained in other parts of the world, although its briefness and availability in over 40 languages make this instrument particularly attractive for international collaborations and cross-cultural comparisons concerning clinical and epidemiological issues. OBJECTIVES: This initial overview summarises some of these non-European experiences with the SDQ by presenting a selection of projects that have either psychometrically evaluated this novel questionnaire, applied it to screen for behaviour disorders, or employed its parent-, teacher- or self-rated versions as research tools. Since a large part of the mentioned studies are ongoing or have only recently been completed, much of the work reported here is still unpublished. CONCLUSIONS: Across a huge variety of cultures and languages, experience gained with the SDQ in other continents has supported European evidence of good psychometric properties and clinical utility of this questionnaire. Since worldwide usage of the SDQ can be expected to increase in the future, more international coordination is encouraged, in order to fully exploit the promising potentials of this versatile assessment tool and systematically investigate cross-cultural differences and similarities in child and adolescent behaviour.

[German version of the Strength and Difficulties Questionnaire (SDQ-German)--overview and evaluation of initial validation and normative results]. / Die deutsche Fassung des Strengths and Difficulties Questionnaire (SDQ-Deu)--Ubersicht und Bewertung erster Validierungs- und Normierungsbefunde.

The Strengths and Difficulties Questionnaire (SDQ) is a short behavioural screening questionnaire which can be completed in about five minutes by parents and teachers of 4- to 16-year-olds or as self-report by 11- to 16-year-olds. The English original has already been fully evaluated and is widely used in research and clinical practice. The instrument was translated into German in 1997, and several evaluative studies have since been completed. The present paper gives an overview of this novel instrument and summarizes the normative and validation studies to date. A normative study on a field sample of 930 children demonstrated that the distributions of raw scores in the German parent SDQ closely resemble those found in the English version, while a factor analysis of the German data yielded a pattern of loadings which convincingly replicated the original scale structure. Initial validation studies showed that the parent-, teacher-, and self-completed SDQ-Deu correlates well with the considerably longer German versions of the Child Behavior Checklist (CBCL) and respective teacher and self-report derivatives (TRF, YSR). Both parent-rated instruments are equally able to distinguish between a community and a clinic sample, and between subgroups with and without specified categories of disorders within a clinic sample. After discussing possible uses of the SDQ-Deu as well as similarities and differences to other scales, we conclude that the German SDQ is just as useful and valid an instrument for many clinical and research purposes as the English original.

Premonitory sensory phenomena and suppressibility of tics in Tourette syndrome: developmental aspects in children and adolescents.

Although premonitory sensory phenomena (PSP) and suppressibility of tics (SPT) are important in Tourette syndrome not only when behavioural therapeutic approaches in children are considered, there is a lack of developmental information on these phenomena. Therefore, a cross-sectional survey of these factors in children and adolescents was carried out. Rates of PSP and SPT were gathered using a questionnaire for the assessment of Tourette syndrome. The 254 outpatients (212 males, 42 females) with Tourette syndrome investigated had an age range of 8 to 19 years, normal intelligence, and diagnosis according to DSM-IV-TR/ICD-10. To test for developmental effects, the total group was stratified into three age groups (8 to 10, 11 to 14, and 15 to 19 years). Data were statistically evaluated using chi2 tests. Of the 254 participants, 37% reported PSP, while 64% were able to suppress their tics. Only a subgroup of 119 patients gave unequivocal answers to both questions and only 60% of these experienced both PSP and SPT. Statistically significant stepwise increases were found at two different age levels. One was around 10 years (PSP 'Yes' or 'No' and SPT), the other around age 14 (PSP 'Yes'). There was no influence of tic duration and age at tic onset on PSP/SPT. The reported data suggest that PSP is experienced rarely in younger children with Tourette syndrome and is not a necessary prerequisite for SPT. Increasing PSP with age merely seems to reflect cognitive development rather than intrinsic aspects of Tourette syndrome. In children under 10 years of age, SPT might require more awareness of tics than in older age groups. Developmental aspects of PSP and SPT should be taken into consideration when studies of cognitive behavioural treatment for children and adolescents with Tourette syndrome are planned.

Disturbed sleep in children with Tourette syndrome: a polysomnographic study.

OBJECTIVE: To evaluate objective data on sleep quantity/quality and motor activity during night sleep in children with Tourette syndrome (TS). METHOD: Polysomnography of 17 unmedicated TS children (ages: 7;11-15;5, mean: 11;10 years) without comorbid attention-deficit hyperactivity disorder (ADHD) was compared with 16 age-, sex- and IQ-matched healthy controls. Sleep analyses according to the procedure of Rechtschaffen and Kales were supplemented by counting epochs with short arousal-related movements (

Developmental event-related gamma oscillations: effects of auditory attention.

This study describes maturational changes in topographical patterns, stability, and functional reactivity of auditory gamma band (31-63 Hz) responses (GBRs) as brain electrical correlates relevant for cognitive development during childhood. GBRs of 114 healthy children from 9 to 16 years were elicited in an auditory focused attention task requiring motor responding to targets, and analyzed by means of the wavelet transform (WT). The effects of age and task variables (attended side and stimulus type relevance) were examined for GBR power and phase-locking within 120 ms after stimulation. Similar to the spontaneous gamma band power, the power and phase-synchronization of GBRs did not depend on the age. However, the functional reactivity of GBRs at specific locations changed in the course of development. In 9-12-year-old children, GBRs at frontal locations were larger and better synchronized to target than to nontarget stimulus type, and were larger over the left hemisphere (contralateral to the responding hand), thus manifesting sensitivity to external stimulus features and motor task. In 13-16-year-old adolescents, GBRs at parietal sites were enhanced by active attending to the side of stimulation, thus being associated with a maintenance of attentional focus to stimulus location. The results indicate that (i) specific aspects of task-stimulus processing engage distinct spatially localized gamma networks at functionally relevant areas, and (ii) the neuronal substrates of gamma band networks and the ability to synchronize them in relation to task-specific processes are available in all age groups from 9 to 16 years. However, the mode and efficiency with which gamma networks can be entrained depends on the age. This age-dependent reactivity of GBRs to different task variables may reflect a transition in processing strategies emerging at approximately 12-13 years in relation to the maturation of cognitive and executive brain functions.