Large-scale analysis of structural brain asymmetries during neurodevelopment: Associations with age and sex in 4265 children and adolescents.

Only a small number of studies have assessed structural differences between the two hemispheres during childhood and adolescence. However, the existing findings lack consistency or are restricted to a particular brain region, a specific brain feature, or a relatively narrow age range. Here, we investigated associations between brain asymmetry and age as well as sex in one of the largest pediatric samples to date (n = 4265), aged 1-18 years, scanned at 69 sites participating in the ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) consortium. Our study revealed that significant brain asymmetries already exist in childhood, but their magnitude and direction depend on the brain region examined and the morphometric measurement used (cortical volume or thickness, regional surface area, or subcortical volume). With respect to effects of age, some asymmetries became weaker over time while others became stronger; sometimes they even reversed direction. With respect to sex differences, the total number of regions exhibiting significant asymmetries was larger in females than in males, while the total number of measurements indicating significant asymmetries was larger in males (as we obtained more than one measurement per cortical region). The magnitude of the significant asymmetries was also greater in males. However, effect sizes for both age effects and sex differences were small. Taken together, these findings suggest that cerebral asymmetries are an inherent organizational pattern of the brain that manifests early in life. Overall, brain asymmetry appears to be relatively stable throughout childhood and adolescence, with some differential effects in males and females.

The role of stress in the pathogenesis and maintenance of obsessive-compulsive disorder.

Individuals with OCD often identify psychosocial stress as a factor that exacerbates their symptoms, and many trace the onset of symptoms to a stressful period of life or a discrete traumatic incident. However, the pathophysiological relationship between stress and OCD remains poorly characterized: it is unclear whether trauma or stress is an independent cause of OCD symptoms, a triggering factor that interacts with a preexisting diathesis, or simply a nonspecific factor that can exacerbate OCD along with other aspects of psychiatric symptomatology. Nonetheless, preclinical research has demonstrated that stress has conspicuous effects on corticostriatal and limbic circuitry. Specifically, stress can lead to neuronal atrophy in frontal cortices (particularly the medial prefrontal cortex), the dorsomedial striatum (caudate), and the hippocampus. Stress can also result in neuronal hypertrophy in the dorsolateral striatum (putamen) and amygdala. These neurobiological effects mirror reported neural abnormalities in OCD and may contribute to an imbalance between goal-directed and habitual behavior, an imbalance that is implicated in the pathogenesis and expression of OCD symptomatology. The modulation of corticostriatal and limbic circuits by stress and the resultant imbalance between habit and goal-directed learning and behavior offers a framework for investigating how stress may exacerbate or trigger OCD symptomatology.

Refined methodology for implantation of a head fixation device and chronic recording chambers in non-human primates.

The present study was aimed at developing a new strategy to design and anchor custom-fitted implants, consisting of a head fixation device and a chronic recording chamber, on the skull of adult macaque monkeys. This was done without the use of dental resin or orthopedic cement, as these modes of fixation exert a detrimental effect on the bone. The implants were made of titanium or tekapeek and anchored to the skull with titanium screws. Two adult macaque monkeys were initially implanted with the head fixation device several months previous to electrophysiological investigation, to allow optimal osseous-integration, including growth of the bone above the implant's footplate. In a second step, the chronic recording chamber was implanted above the brain region of interest. The present study proposes two original approaches for both implants. First, based on a CT scan of the monkey, a plastic replicate of the skull was obtained in the form of a 3D print, used to accurately shape and position the two implants. This would ensure a perfect match with the skull surface. Second, the part of the implants in contact with the bone was coated with hydroxyapatite, presenting chemical similarity to natural bone, thus promoting excellent osseous-integration. The longevity of the implants used here was 4 years for the head fixation device and 1.5 years for the chronic chamber. There were no adverse events and daily care was easy. This is clear evidence that the present implanting strategy was successful and provokes less discomfort to the animals.

[The EEG preferential frequency as an indicator of the degree of wakefulness]. / Die EEG-Vorzugsfrequenz als Indikator des Wachheitsgrades.

Ever since electroencephalographic research began, interest has been focused on problems of the physiology, pathology, and symptomatology of the relationship between sleep and wakefulness. Following preliminaries, the present paper describes a combined procedure for the determination of the EEG preferential frequency, and by random sampling statistically examines its suitability for indicating the fluctuations of activation level as a control measure. A trained volunteer gradually increased his degree of wakefulness, reliably producing parallel changes in the preferential frequency in three frequency bands. A standardised manual period analysis as control produced largely the same results. The preferential frequency has considerable value for indicating the degree of wakefulness.

An approach for representing EEG activity.

A method for the representation of EEG-parameters by means of a bidimensional plot of two signals is described. A block diagram is given for the recording of figures with phase-sensitive parameter variations, using an oscilloscope or an X-Y graphic recorder as a display. Charts for the determination of the setting parameters of a digital as well as an analog phase-shifting arrangement are submitted. The method is capable of reflecting individual properties of a single wave and typical characteristics of the epoch as well. It is felt that it may be of benefit in the immediate estimation of EEG-activity changes.

[Electroencephalogram in standardized mental stress: variable trends in the theta, alpha and beta band]. / Das Elektroenzephalogramm bei standardisierter geistiger Belastung: Variablentrends im Theta-, Alpha- und Beta- Band.

The results, gained in previous studies by means of computer-assisted interval analysis and amplitude analysis, of power spectra as well as of visuomanual pattern evaluation of the EEG during standardized mental load, were related to each other. Described are the significantly requirement-dependent trends of data in there three frequency bands. Under consideration of methodological rules (complementarity, non-reactive measuring, multivariate representation, balanced change-over design, multidimensional data analysis etc.) a characterization of the EEG functional test (graded cognitive strain, eyes opened) is given.

[Periods and amplitude distribution parameters of the EEG in mental stress--on the concordance of mechanical and visuomanual methods of evaluation]. / Perioden und Amplitudenverteilungs-parameter des EEGs bei geistiger Belastung - zur Konkordanz maschineller und visumanueller Auswertungsmethoden.

Mean frequency, % index and mean amplitudes in 3 frequency bands served as basis for a dynamic comparison of manual and computer assisted EEG analyses in healthy adults. In spite of inevitable methodical deviations it was possible to assume quite a good concordance for the significant data trends with but one exception. Among others the mean frequencies proved to be predicative variables in the EEG functional test with eyes opened. The satisfactory result provides arguments for a greater involvement of automated methods for quantitative description of the EEG activity in clinical practice.

[Influence of anatomical variations of the pancreatic artery on the surgical technic of segmental pancreas transplantation in dogs]. / Einfluss der anatomischen Variationen der Arteria pancreatica auf die chirurgische Technik der segmentalen Pankreastransplantation beim Hund.

The surgical technique in clinical pancreas transplantation is still not standardized. Animal experimentation should allow a reproducible and reliable model by choosing the cervical region in dogs as the site of segmental grafting. A goal of the experiments was to determine the influence of preservation, operation technique, duct occlusion, immunosuppression, and gastrointestinal hormones (Somatostatin, Cyclosporin A). 50 grafts have been transplanted. It could be clearly demonstrated that in 54% the vascularization of the left lobe of the canine pancreas differs extremely from man. Successful results are to expect being aware of the anatomical variations. The varieties of the arterial blood supply indicate which technique has to be performed to avoid ischemic grafts due to inadequate preservation.

[About the adjustment of filters and comparators for the automatic interval-analysis (author's transl)]. / Zur Einstellung von Filtern und Komparatoren für die maschinelle Intervallanalyse.

The selective effect produced by an analog filter followed by a comparator, is represented in the voltage-frequency-plane by a frequency-dependent threshold of sensitivity and a scatter-diagramm, which is characterising the signal. The variation of the threshold, caused by differentiation of the signal, is described. Following this model it is discussed, how deviations of real circuits and real signals from certain assumptions influence the formation of intervals and the interval-histogram. It is stated, which values of the parameters of adjustment should be set, on the one hand, in order to minimize errors of the interval-length and maximize frequencies of intervals in the pass-band and, on the other hand, to provide for the chance of separating from the histogram such intervals which are inevitably subject to bigger faults.--Other criteria of optimization are pointed out. Technically caused limitations for the variation of parameters are mentioned. The application of the model, which is valid for analog signals in general, is demonstrated by two examples from the automatic analysis of EEG.

[Activation-dependent characteristics of the electroencephalogram during visual information processing: II Results of an automatic amplitude analysis based on momentary values of signal voltage (author's transl)]. / Aktivierungsabhängige Kenngrössen des Elektroenzephalogramms während visueller Informationsverarbeitungsleistungen.

EEG was recorded in 16 Ss. under conditions of a modified "Konzentrations-Leistung-Test" including four levels of performance (balanced change-over design), and histograms of the momentary values of the signal voltages (derivation F3/01) constructed for frequency bands 4...8 Hz, 8...13 Hz and 13...26 Hz. The type of performance affected significantly standard deviations and the excesses in all frequency bands (multivariate analysis of variance, F-Test). Similar to the results of an interval analysis (Activ. ner. sup. 18, 1976, p. 244), the differences in mean values indicated the preponderant relevance of perceptual factors (NEWMAN-KEULS-Test). Four characteristics showed a significant activation dependence: the standard deviations of the amplitude distributions in the frequency bands 4...8 Hz and 13...26 Hz, corresponding to the root-mean--square values of the signal voltages, as well as the excesses in the frequency bands 8...13 Hz and 13...26 Hz. Only and amplitude of the theta waves were influenced notably by mental arithmetics, significantly though only when this was done under conditions of time stress.

[Activation-dependent characteristics of the electroencephalogram during visual information--processing: Results of an automatic interval analysis (author's transl)]. / Aktivierungsabhängige Kenngrössen des Elektroenzephalogramms bei visuellen Informationsverarbeitunsleistungen: Ergebnisse der maschinellen Intervallanalyse

EEG signal from fronto-occipital derivation was recorded in 16 Ss during a mental performance test (modified "Konzentrations-Leistungs-Test" including four levels of performance). A balanced changer-over design was used. Interval histograms in four frequency bands (theta, alpha, beta-1 and beta-2 bands) were determined on the basis of peak detection. A total of 44 characteristics were derived and tested (multi-factor analyses of variance, multiple mean comparison and rank tests). Twenty eight of these characteristics were proved to be dependent on activation. In the visual information-processing performances chosen, it could be demonstrated that the intraindividual changes of the spontaneous EEG activity were related predominantly to the perceptual components of the performance. On the other hand, the influence of the performance rate and of the mental-arithmetic itself was of minor relevance. During higher activation an increase in the relative abudance of the theta-band activity was also observed.