Lifespan trajectories of relative corpus callosum thickness: Regional differences and cognitive relevance.

The cerebral hemispheres are specialized for different cognitive functions and receive divergent information from the sensory organs, so that the interaction between the hemispheres is a crucial aspect of perception and cognition. At the same time, the major fiber tract responsible for this interaction, the corpus callosum, shows a structural development across the lifespan which is over-proportional. That is, compared to changes in overall forebrain volume, the corpus callosum shows an accentuated growth during childhood, adolescence, and early adulthood, as well as pronounced decline in older age. However, this over-proportionality of growth and decline along with potential consequences for cognition, have been largely overlooked in empirical research. In the present study we systematically address the proportionality of callosal development in a large mixed cross-sectional and longitudinal sample (1867 datasets from 1014 unique participants), covering the human lifespan (age range 4-93 years), and examine the cognitive consequences of the observed changes. Relative corpus callosum thickness was measured at 60 segments along the midsagittal surface, and lifespan trajectories were clustered to identify callosal subsections of comparable lifespan development. While confirming the expected inverted u-shaped lifespan trajectories, we also found substantial regional variation. Compared with anterior clusters, the most posterior sections exhibited an accentuated growth during development which extends well into the third decade of life, and a protracted decline in older age which is delayed by about 10 years (starting mid to late 50s). We further showed that the observed longitudinal changes in relative thickness of the mid splenium significantly mediates age-related changes in tests assessing verbal knowledge and non-verbal visual-spatial abilities across the lifespan. In summary, we demonstrate that analyzing the proportionality of callosal growth and decline offers valuable insight into lifespan development of structural connectivity between the hemispheres, and suggests consequences for the cognitive development of perception and cognition.

Healthy minds from 0-100 years: Optimising the use of European brain imaging cohorts ("Lifebrain").

The main objective of "Lifebrain" is to identify the determinants of brain, cognitive and mental (BCM) health at different stages of life. By integrating, harmonising and enriching major European neuroimaging studies across the life span, we will merge fine-grained BCM health measures of more than 5,000 individuals. Longitudinal brain imaging, genetic and health data are available for a major part, as well as cognitive and mental health measures for the broader cohorts, exceeding 27,000 examinations in total. By linking these data to other databases and biobanks, including birth registries, national and regional archives, and by enriching them with a new online data collection and novel measures, we will address the risk factors and protective factors of BCM health. We will identify pathways through which risk and protective factors work and their moderators. Exploiting existing European infrastructures and initiatives, we hope to make major conceptual, methodological and analytical contributions towards large integrative cohorts and their efficient exploitation. We will thus provide novel information on BCM health maintenance, as well as the onset and course of BCM disorders. This will lay a foundation for earlier diagnosis of brain disorders, aberrant development and decline of BCM health, and translate into future preventive and therapeutic strategies. Aiming to improve clinical practice and public health we will work with stakeholders and health authorities, and thus provide the evidence base for prevention and intervention.

Selectively reduced posterior corpus callosum size in a population-based sample of young adults born with low birth weight.

BACKGROUND AND PURPOSE: Several studies suggest that VLBW is associated with a reduced CC size later in life. We aimed to clarify this in a prospective, controlled study of 19-year-olds, hypothesizing that those with LBWs had smaller subregions of CC than the age-matched controls, even after correcting for brain volume. MATERIALS AND METHODS: One hundred thirteen survivors of LBW (BW <2000 grams) without major handicaps and 100 controls underwent a 3T MR examination of the brain. The cross-sectional area of the CC (total callosal area, and the callosal subregions of the genu, truncus, and posterior third) was measured. Callosal areas were adjusted for head size. RESULTS: The posterior third subregion of the CC was significantly smaller in individuals born with a LBW compared with controls, even after adjusting for size of the forebrain. Individuals who were born with a LBW had a smaller CC (mean area, 553.4 mm(2)) than the controls (mean area, 584.1 mm(2)). Differences in total area, however, did not remain statistically significant after adjusting for FBV. CONCLUSIONS: The uncorrected callosal size in 19-years-olds born with LBW was smaller than that of normal controls. However, after adjusting for FBV, the group difference was restricted to the posterior third. The clinical impact of a smaller posterior part needs further investigation.

Sex differences in cognitive control are associated with midcingulate and callosal morphology.

Sex differences in the processing of cognitively demanding tasks have attracted much attention in recent years. While there seems to be some agreement on differences between males and females concerning spatial abilities and language skills, a consensus regarding executive functions or cognitive control has not been reached yet. In the present study, male and female subjects participated in a lateralized, tactile Stop-Signal task. Although the behavioral data did not show any differences between sexes, event-related potentials pointed to varieties in neurocognitive processing. As inferred from N200 amplitudes, differences between left- and right-hand stimulation suggested a strong degree of functional lateralization in males in accordance with a left-hemispheric dominance. Females, on the other hand, rather seemed to exhibit a functionally symmetric organization of relevant processes. The P300 did also show evidence of sex-related differences, reflecting disparities in the degree or quality of interhemispheric interaction. In addition, behavioral and electrophysiological parameters were correlated with individual metrics concerning the degree of midcingulate folding asymmetry and the morphology of the corpus callosum. Differential associations of these morphological characteristics with the N200 and P300, respectively, underscore the notion of relevant structure-function associations of the midcingulate cortex and the N200 on the one hand, and the corpus callosum and the P300 on the other hand. Obviously, these variations in neuroanatomy contribute to the observed behavioral and electrophysiological differences between women and men.

The role of the cingulate cortex as neural generator of the N200 and P300 in a tactile response inhibition task.

Both the N200 and P300, which are, for example, evoked by Go/Nogo or Stop-Signal tasks, have long been interpreted as indicators for inhibition processes. Such interpretations have recently been challenged, and interest in the exact neural generators of these brain responses is continuously growing. Using recent methodological advancements, source estimations for the N200 and P300 as evoked by a tactile response inhibition task were computed. Current density reconstructions were also calculated accounting for interindividual differences in head geometry by incorporating information from T1-weighted magnetic resonance images. To ease comparability with relevant paradigms, the task was designed to mimic important characteristics of both Go/Nogo and Stop-Signal tasks as prototypes for a larger set of paradigms probing response inhibition. A network of neural generators was revealed, which has previously been shown to act in concert with executive control processes and thus is in full agreement with observations from other modalities. Importantly, a spatial segregation of midcingulate sources was observed. Our experimental data indicate that a left anterior region of the midcingulate cortex (MCC) is a major neural generator of the N200, whereas the midcingulate generator of the P300 is located in the right posterior MCC. Analyses of the P300 also revealed several areas, which have previously been associated with motor functions, for example, the precentral region. Our data clearly suggest a neuroanatomical and therefore also functional dissociation of the N200 and P300, a finding that cannot easily be provided by other imaging techniques.

[High resolution contrast-enhanced 3D MR-angiography of renal arteries using parallel imaging (SENSE)]. / Hochauflösende Kontrastmittel-gestützte 3D-MR-Angiographie (MRA) der Nierenarterien mit paralleler Bildgebung (SENSE).

PURPOSE: To compare three dimensional contrast enhanced MR angiography with parallel imaging technique (sensitivity encoding) to standard MR angiography technique. MATERIAL AND METHODS: CE-3D MRA of renal arteries was performed in 22 patients (23 examinations) on a 1.5 T MR- scanner (Gyroscan Intera, Philips, Netherlands). For contrast enhanced MRA a single dose of Gd-DTPA (0.1 mmol/kg b.w.) was administered. Group I: The following standard 3D gradient echo (GE) sequence was performed in 9 of the 22 patients: TR: 4.3 ms, TE: 1.5 ms, flip angle: 40, 40 slices, scan duration: 19 seconds. A spatial resolution of 1.96 x 1.76 x 3.0 mm (3) (1.76 x 1.76 x 1.5 mm (3) interpolated) was obtained. Group II: 14 examinations were acquired in 13 patients: TR, TE and flip angle were equal compared to the first protocol. The k-space lines were acquired with CENTRA (contrast-enhanced time robust angiography) and parallel imaging technique (SENSE). 60 slices were acquired, scan duration was 24 seconds. The spatial resolution of this sequence was 1.19 x 1.08 x 2.0 mm (3) (0,84 x 0,84 x 1,0 mm (3) interpolated). Original images and calculated maximum intensity projection (MIP) images were analysed by two radiologists. Image quality and the visibility of renal arteries were rated on a four-point scale. RESULTS: In the first group the image quality was rated "good" in 8/9 patients. The renal arteries were detected in all cases and rated "good". The anterior and posterior segments were rated "good" in only 5/9 and the lobar arteries were detectable only in 3 of 9 cases. The interlobar arteries could not be seen in these patients. In the second group the image quality was rated excellent in 5 examinations and good in 9 of 14 examinations. The rating for the renal arteries was excellent in all examinations (14/14). The results of the anterior and posterior segment were as followed: excellent 5/14, good 7/14, insufficient 2/14; the lobar arteries: good 6/14, insufficient 6/14 and not detectable 2/14. Interlobar arteries could be seen in 7/14 examinations, but the quality was insufficient. In 7/14 the interlobar arteries could not be detected. CONCLUSION: The use of parallel imaging technique improves image quality and the delineation of small vessels in renal MRA.