It is generally agreed that the cerebral cortex can be segregated into structurally and functionally distinct areas. Anatomical subdivision of Broca's area has been achieved using different ...microanatomical criteria, such as cytoarchitecture and distribution of neuroreceptors. However, brain function also strongly depends upon anatomical connectivity, which therefore forms a sensible criterion for the functio-anatomical segregation of cortical areas. Diffusion-weighted magnetic resonance (MR) imaging offers the opportunity to apply this criterion in the individual living subject. Probabilistic tractographic methods provide excellent means to extract the connectivity signatures from diffusion-weighting MR data sets. The correlations among these signatures may then be used by an automatic clustering method to identify cortical regions with mutually distinct and internally coherent connectivity. We made use of this principle to parcellate Broca's area. As it turned out, 3 subregions are discernible that were identified as putative Brodmann area (BA) 44, BA45, and the deep frontal operculum. These results are discussed in the light of previous evidence from other methods in both human and nonhuman primates. We conclude that plausible results can be achieved by the proposed technique, which cannot be obtained by any other method in vivo. For the first time, there is a possibility to investigate the anatomical subdivision of Broca's area noninvasively in the individual living human subject.
Older individuals typically display stronger regional brain activity than younger subjects during motor performance. However, knowledge regarding age-related changes of motor network interactions ...between brain regions remains scarce. We here investigated the impact of ageing on the interaction of cortical areas during movement selection and initiation using dynamic causal modelling (DCM). We found that age-related psychomotor slowing was accompanied by increases in both regional activity and effective connectivity, especially for ‘core’ motor coupling targeting primary motor cortex (M1). Interestingly, younger participants within the older group showed strongest connectivity targeting M1, which steadily decreased with advancing age. Conversely, prefrontal influences on the motor system increased with advancing age, and were inversely correlated with reduced parietal influences and core motor coupling. Interestingly, higher net coupling within the prefrontal-premotor-M1 axis predicted faster psychomotor speed in ageing. Hence, as opposed to a uniform age-related decline, our findings are compatible with the idea of different age-related compensatory mechanisms, with an important role of the prefrontal cortex compensating for reduced coupling within the core motor network.
•Enhanced motor network activity and connectivity in ageing•Parietal-premotor and premotor-M1 coupling decreases with advancing age.•Prefrontal influences on the motor system increase with advancing age.•Prefrontal cortex compensates for age-related decline in other motor connections.•Prefrontal-premotor-M1 coupling predicts psychomotor speed in ageing.
Highlights ► We investigated three groups of amphetamine and MDMA users. ► Data on cortical thickness, cortical volume and subcortical structures have been collected. ► Heavy users displayed cortical ...thinning and volume reduction in frontal and parietal regions. ► Drug naïve controls did not differ from low exposure users. ► Neuronal degeneration might be associated with the use of amphetamine derivates.
Two eye fields have been described in the human lateral frontal cortex: the frontal eye field (FEF) and the inferior frontal eye field (iFEF). The FEF has been extensively studied and has been found ...to lie at the ventral part of the superior precentral sulcus. Much less research, however, has focused on the iFEF. Recently, it was suggested that the iFEF is located at the dorsal part of the inferior precentral sulcus. A similar location was proposed for the inferior frontal junction area (IFJ), an area thought to be involved in cognitive control processes. The present study used fMRI to clarify the topographical and functional relationship of the iFEF and the IFJ in the left hemispheres of individual participants. The results show that both the iFEF and the IFJ are indeed located at the dorsal part of the inferior precentral sulcus. Nevertheless, the activations were spatially dissociable in every individual examined. The IFJ was located more towards the depth of the inferior precentral sulcus, close to the junction with the inferior frontal sulcus, whereas the iFEF assumed a more lateral, posterior and superior position. Furthermore, the results provided evidence for a functional double dissociation: the iFEF was activated only in a comparison of saccades vs. button presses, but not in a comparison of incongruent vs. congruent Stroop conditions, while the opposite pattern was found at the IFJ. These results provide evidence for a spatial and functional dissociation of two directly adjacent areas in the left posterior frontal lobe.
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► Functional and topographic relationship of iFEF and IFJ is an open question. ► Both areas suggested to be located at the dorsal inferior precentral sulcus (IPrCS). ► We show that, despite proximity, activations of both areas only marginally overlap. ► IFJ is located at the depth of the IPrCS and is involved in cognitive control. ► iFEF is found further laterally and posteriorly and is activated by eye movements.
Stereotactic surgery is based on a high degree of accuracy in defining and localising intracranial targets and placing surgical tools. Brain shift can influence its accuracy significantly. Deep brain ...stimulation of the subthalamic nucleus can markedly change the quality of life of patients with advanced Parkinson’s disease, but the outcome depends on the quality of electrode placement. A patient is reported in whom the placement of the second electrode was not successful. Deformation field analysis of pre- and postoperative three dimensional magnetic resonance images showed an intraoperative brain movement of 2 mm in the region of the subthalamic nucleus (the target point). Electrode repositioning resulted in efficient stimulation effects. This case report shows the need to reduce risk factors for intraoperative brain movement and demonstrates the ability of deformation field analysis to quantify this complication.
The interaction of basal ganglia and other brain regions is more complex regarding anatomic and functional perspectives than previously assumed. Hence, the classical basal ganglia model has to be ...extended to at least four satellite systems modulating motor-executive, associative and limbic-motivational brain regions: (i) an indirect projection system, (ii) a striato-nigro-striatal loop, (iii) a "hyperdirect" projection system as well as additional projections to the subthalamic nucleus and (iv) multisynaptic connections from the cerebellum exerting influence on the indirect projection system. The investigation of these satellite systems would be invaluable to foster our understanding of basal ganglia circuitries and may yield a better appreciation of largely opaque symptoms like resting tremor in Parkinson's disease; analysis of these anatomic pathways and functional implications may facilitate explanatory model approaches to side effects due to dopaminergic therapy and deep brain stimulation in humans and thereby offer the possibility for new therapeutic approaches in movement disorders.
Areas activated in the high load vs. low load contrast were located in the pre-supplementary motor area, the bilateral intraparietal sulcus, and the precuneus.
G.P.130 Merkel, C; Minnerop, M; Roeske, S ...
Neuromuscular disorders : NMD,
10/2014, Letnik:
24, Številka:
9
Journal Article
Recenzirano
It is unknown whether brain affection in myotonic dystrophy type 1 (DM1) and 2 (DM2) is due to neurodevelopmental defects, neurodegeneration or both. Longitudinal imaging studies are missing to date. ...We performed a longitudinal study to compare changes in cognitive functioning and brain morphology including 16 DM1 (m/f: 6/10, age at baseline 42.48 ± 6.46 years/y, disease duration/DD 13.4 ± 7.5 y), 16 DM2 patients (m/f: 9/7, age 48.49 ± 8.36 y, DD 11.4 ± 9.1 y), and 17 healthy controls (m/f: 9/8, age 50.54 ± 9.78 y). At baseline and 5.45 ± 0.41 y follow-up all subjects underwent neurological and neuropsychological (NP) examinations and 3T-brain magnetic resonance imaging using the identical hard- and software. Diffusion tensor imaging (DTI, Tract Based Spatial Statistics) was conducted to analyse white matter (WM) affection with respect to fractional anisotropy (FA), axial, radial, and mean diffusivity. We used 2-sample t-tests (TT) for group comparisons between patients and controls, and paired t -tests (PT) for longitudinal analyses within each group ( p < 0.05, corrected for multiple comparisons). DTI group comparisons (TT) showed almost identical FA reduction patterns at baseline and follow-up. In DM1 compared to controls, FA was reduced along the corpus callosum (CC), association (AF), and projection fibres. In DM2, we found mild affection of CC and forceps minor, and minor additional changes at follow-up. At follow-up, the number of voxels showing FA reduction was particularly increased in DM1 indicating progressive WM disintegrity. Analysing longitudinal differences within each group (PT), we found significant FA changes only in DM1 affecting frontal and posterior AF. These findings were accompanied by a decline in motor tasks in DM1, and a mild deterioration of NP performance in DM1 more than DM2 over time. Our data indicate a mild -however significant-progress of WM affection predominantly in DM1 which might point towards a neurodegenerative component of WM changes.
The human amygdala is reliably activated by facial expressions 1, but the precise functional relevance of such activity change is not well understood, because most previous studies did not allow for ...separating effects of the emotional expression from the distribution of specific facial features and neglected corresponding attentional processes. Findings on rare patients with bilateral amygdala damage indicate that the amygdala might be involved in triggering shifts of overt attention towards specific facial features such as the eyes 2. Moreover, it was reported that healthy individuals show a preference for attending to the eye region across different emotional expressions 3. This early attentional bias was linked to amygdala activity 4, and was found to be most pronounced for fearful faces and less pronounced for happy facial expressions 3,5. These findings indicate that healthy individuals show a tendency to automatically attend to facial features that are diagnostic of the current emotional state of conspecifics 6. Here, we examined an otherwise healthy, male adult individual (MW) with unilateral right-sided amygdala loss in a novel, eye-tracking-based face perception task in order to clarify the functional role of the amygdala complex in driving attentional orienting. Compared to a sample of matched controls, MW showed an isolated deficit in reflexive gaze shifts towards diagnostic emotional facial features during brief stimulus presentations as compared to normal performance during longer viewing periods. These results suggest that the amygdala is implicated in quickly detecting diagnostic facial features in the visual periphery and driving reflexive saccades towards these locations.
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