Whereas we know a fair amount on the role of the amygdala in the acute stress response, virtually nothing is known about its role during the recovery period after the stress has waned. Functional... Show moreWhereas we know a fair amount on the role of the amygdala in the acute stress response, virtually nothing is known about its role during the recovery period after the stress has waned. Functional connectivity analysis of the amygdala during this period might be useful in revealing brain circuits promoting adaptive recovery from a stressful event, as well as consolidation of emotionally relevant information in preparing for future challenges. Healthy participants were randomly assigned to either a psychosocial stress task (n = 18; stress group) or a comparable non-stressful control procedure (n = 20; controls). To study the prolonged effects of stress on amygdala functional connectivity, resting-state fMRI scans were acquired an hour after the stress task. Amygdala functional connectivity with other brain regions was assessed using seed-based correlations. The stress group exhibited a strong physiological and behavioral reaction to psychosocial stress exposure. Compared with controls the stress group showed increased amygdala functional connectivity with three cortical midline structures: the posterior cingulate cortex and precuneus (p<.05, corrected), and the medial prefrontal cortex (p<.05, small volume corrected). An hour after psychosocial stress, changes in amygdala functional connectivity were detected with cortical midline structures involved in the processing and regulation of emotions, as well as autobiographical memory. It is hypothesized that these effects could relate to top-down control of the amygdala and consolidation of self-relevant information after a stressful event. These results on functional connectivity in the recovery phase after stress might provide an important new vantage point in studying both sensitivity and resilience to stress. (C) 2011 Elsevier Inc. All rights reserved. Show less
Guroglu, B.; Bos, W. van den; Dijk, E. van; Rombouts, S.A.R.B.; Crone, E.A. 2011
In this functional magnetic resonance imaging study, we examined developmental changes in the brain regions involved in reactions to unfair allocations. Previous studies on adults suggested that... Show moreIn this functional magnetic resonance imaging study, we examined developmental changes in the brain regions involved in reactions to unfair allocations. Previous studies on adults suggested that reactions to unfairness are not only affected by the distribution itself but also by the ascribed intentionality of the proposer. In the current study, we employed the mini Ultimatum Game (Falk, Fehr, & Fischbacher, 2003) to examine responder behavior to unfair offers of varying degrees of intentionality. Sixty-eight participants from four age groups (10-, 13-, 15-, and 20-year-olds) carried out the task while fMRI data were acquired. Participants of all ages showed activation in the bilateral insula and dorsal anterior cingulate cortex (dACC) during rejection of unintentional but acceptance of intentional unfair offers. Rejection of unintentional unfair offers further involved increasing activation with age in the temporoparietal junction and the dorsolateral prefrontal cortex. These findings provide evidence for an early developing insula-dACC network involved in detecting personal norm-violations and gradually increasing involvement of temporal and prefrontal brain regions related to intentionality considerations in social reasoning. The results are discussed in light of recent findings on the development of the adolescent social brain network. (C) 2011 Elsevier Inc. All rights reserved. Show less
Zwanenburg, J.J.M.; Versluis, M.J.; Luijten, P.R.; Petridou, N. 2011
Magnetic susceptibility based (T-2* weighted) contrast in MRI at high magnetic field strength is of great value in research on brain structure and cortical architecture, but its use is hampered by... Show moreMagnetic susceptibility based (T-2* weighted) contrast in MRI at high magnetic field strength is of great value in research on brain structure and cortical architecture, but its use is hampered by the low signal-to-noise ratio (SNR) efficiency of the conventional spoiled gradient echo sequence (GRE) leading to long scan times even for a limited number of slices. In this work, we show that high resolution (0.5 mm isotropic) T-2* weighted images of the whole brain can be obtained in 6 min by utilizing the high SNR efficiency of echo-planar imaging (EPI). A volumetric (3D) EPI protocol is presented and compared to conventional 3D GRE images acquired with the same resolution, amount of T-2* weighting, and imaging duration. Spatial coverage in 3D EPI was increased by a factor of 4.5 compared to 3D GRE, while also the SNR was increased by a factor of 2. Image contrast for both magnitude and phase between gray and white matter was similar for both sequences, with enhanced conspicuity of anatomic details in the 3D EPI images due to the increased SNR. Even at 7 T, image blurring and distortion is limited if the EPI train length remains short (not longer than the T-2* of the imaged tissue). 3D EPI provides steps (speed, whole brain coverage, and high isotropic resolution) that are necessary to utilize the benefits of high field MRI in research that employs T-2* weighted imaging. (C) 2011 Elsevier Inc. All rights reserved. Show less
Ferrarini, L.; Veer, I.M.; Lew, B. van; Oei, N.Y.L.; Buchem, M.A. van; Reiber, J.H.C.; ... ; Milles, J. 2011
In recent years, graph theory has been successfully applied to study functional and anatomical connectivity networks in the human brain. Most of these networks have shown small-world topological... Show moreIn recent years, graph theory has been successfully applied to study functional and anatomical connectivity networks in the human brain. Most of these networks have shown small-world topological characteristics: high efficiency in long distance communication between nodes, combined with highly interconnected local clusters of nodes. Moreover. functional studies performed at high resolutions have presented convincing evidence that resting-state functional connectivity networks exhibits (exponentially truncated) scale-free behavior. Such evidence, however. was mostly presented qualitatively, in terms of linear regressions of the degree distributions on log-log plots. Even when quantitative measures were given, these were usually limited to the r(2) correlation coefficient. However, the r2 statistic is not an optimal estimator of explained variance, when dealing with (truncated) power-law models. Recent developments in statistics have introduced new non-parametric approaches. based on the Kolmogorov-Smirnov test, for the problem of model selection. In this work, we have built on this idea to statistically tackle the issue of model selection for the degree distribution of functional connectivity at rest. The analysis, performed at voxel level and in a subject-specific fashion, confirmed the superiority of a truncated power-law model, showing high consistency across subjects. Moreover, the most highly connected voxels were found to be consistently part of the default mode network. Our results provide statistically sound support to the evidence previously presented in literature for a truncated power-law model of resting-state functional connectivity. (C) 2011 Elsevier Inc. All rights reserved. Show less
White matter provides anatomic connections among brain regions and has received increasing attention in understanding brain intrinsic networks and neurological disorders. Despite significant... Show moreWhite matter provides anatomic connections among brain regions and has received increasing attention in understanding brain intrinsic networks and neurological disorders. Despite significant progresses made in characterizing the white matters structural properties using post-mortem techniques and in vivo diffusion-tensor-imaging (DTI) methods, its physiology remains poorly understood. In the present study, cerebral blood flow (CBF) of the white matter was investigated on a fiber tract-specific basis using MRI (n = 10, 25-33 years old). It was found that CBF in the white matter varied considerably, up to a factor of two between fiber groups. Furthermore, a paradoxically inverse correlation was observed between white matter CBF and structural and functional connectivities (P<0.001). Fiber tracts that had a higher CBF tended to have a lower fractional anisotropy in water diffusion, and the gray matter terminals connected to the tract also tended to have a lower temporal synchrony in resting-state BOLD signal fluctuation. These findings suggest a clear association between white matter perfusion and gray matter activity, but the nature of this relationship requires further investigations given that they are negatively, rather than positively, correlated. (C) 2011 Elsevier Inc. All rights reserved. Show less
Several studies have examined the neural effects of working memory practice, but due to different task demands, diverse patterns of neural changes have been reported. In the present study, we... Show moreSeveral studies have examined the neural effects of working memory practice, but due to different task demands, diverse patterns of neural changes have been reported. In the present study, we examined neural effects of practice using a task with different working memory demands within a single practice paradigm. Fifteen adults practiced during 6 weeks with a task that required maintenance and manipulation of information under low and high working memory loads. Functional magnetic resonance imaging (FMRI) data were acquired in the first week and last week of the practice period. Results were compared with results of a control group who did not practice the task. We demonstrated that practice was beneficial for both working memory maintenance and manipulation processes but that these processes were supported by different neural changes. While maintenance trials showed increased activation (i.e., less deactivation) in default-mode regions after practice, manipulation trials experienced increased activation in the striatum. Changes were also observed in left ventrolateral prefrontal cortex (VLPFC), bilateral dorsolateral prefrontal cortex (DLPFC) and left superior parietal cortex (SPC). However, for bilateral DLPFC and left SPC, these changes were not specific to the practice group. These findings illustrate the importance of controlling for test-retest effects in training or intervention studies. Behavioral follow-up tests demonstrated that practice effects lasted over a 6-month period, but the absence of transfer effects indicated that the acquired skills were specific for the practiced working memory task. (C) 2010 Elsevier Inc. All rights reserved. Show less
Versluis, M.J.; Peeters, J.M.; Rooden, S. van; Grond, J. van der; Buchem, M.A. van; Webb, A.G.; Osch, M.J.P. van 2010
The altered iron concentration in many neurodegenerative diseases such as Alzheimer's disease (AD) has led to the development of MRI sequences that are sensitive to the accompanying changes in the... Show moreThe altered iron concentration in many neurodegenerative diseases such as Alzheimer's disease (AD) has led to the development of MRI sequences that are sensitive to the accompanying changes in the transverse relaxation rate. Heavily T-2*-weighted imaging sequences at high magnetic field strength (7 T and above), in particular, show potential for detecting small changes in iron concentration. However, these sequences require a long echo time in combination with a long scanning time for high resolution and are therefore prone to image artifacts caused by physiological fluctuations, patient motion or system instabilities. Many groups have found that the high image quality that was obtained using high resolution T-2*-weighted sequences at 7 T in healthy volunteers, could not be obtained in AD patients. In this study the source of the image artifacts was investigated in phantom and in healthy volunteer experiments by incorporating movement parameters and resonance frequency (f0) variations which were measured in AD patients. It was found that image degradation caused by typical f0 variations was a factor-of-four times larger than artifacts caused by movement characteristic of AD patients in the scanner. In addition to respiratory induced f0 variations, large jumps in the f0 were observed in AD patients. By implementing a navigator echo technique to correct for f0 variations, the image quality of high resolution T-2*-weighted images increased considerably. This technique was successfully applied in five AD patients and in five subjective memory complainers. Visual scoring showed improvements in image quality in 9 out of 10 subjects. Ghosting levels were reduced by 24 +/- 13%. (C) 2010 Elsevier Inc. All rights reserved. Show less
Zarei, M.; Patenaude, B.; Damoiseaux, J.; Morgese, C.; Smith, S.; Matthews, P.M.; ... ; Jenkinson, M. 2010
Recent models hypothesize that adolescents' risky behavior is the consequence of increased sensitivity to rewards in the ventral medial (VM) prefrontal cortex (PFC) and the ventral striatum (VS),... Show moreRecent models hypothesize that adolescents' risky behavior is the consequence of increased sensitivity to rewards in the ventral medial (VM) prefrontal cortex (PFC) and the ventral striatum (VS), paired with immature cognitive control abilities due to slow maturation of the dorsal anterior cingulate cortex (ACC) and lateral PFC. We tested this hypothesis with fMRI using a gambling task in which participants chose between Low-Risk gambles with a high probability of obtaining a small reward (1 Euro) and High-Risk gambles with a smaller probability of obtaining a higher reward (2, 4, 6, or 8 Euro). We examined neural responses during choice selection and outcome processing in participants from 4 age groups (pre-pubertal children, early adolescents, older adolescents and young adults). High-Risk choices increased with rewards for all ages, but risk-taking decreased with age for low reward gambles. The fMRI results confirmed that High-Risk choices were associated with activation in VMPFC, whereas Low-Risk choices were associated with activation in lateral PFC. Activation in dorsal ACC showed a linear decrease with age, whereas activation in VMPFC and VS showed an inverted U-shaped developmental pattern, with a peak in adolescence. In addition, behavioral differences in risk-taking propensity modulated brain activation in all age groups. These findings support the hypothesis that risky behavior in adolescence is associated with an imbalance caused by different developmental trajectories of reward and regulatory brain circuitry. (C) 2010 Elsevier Inc. All rights reserved. Show less
Zarei, M.; Patenaude, B.; Damoiseaux, J.; Morgese, C.; Smith, S.; Matthews, P.M.; ... ; Jenkinson, M. 2010
Alzheimer's disease (AD) is associated with neuronal loss not only in the hippocampus and amygdala but also in the thalamus. Anterodorsal, centromedial, and pulvinar nuclei are the main sites of... Show moreAlzheimer's disease (AD) is associated with neuronal loss not only in the hippocampus and amygdala but also in the thalamus. Anterodorsal, centromedial, and pulvinar nuclei are the main sites of degeneration in AD. Here we combined shape analysis and diffusion tensor imaging (DTI) tractography to study degeneration in AD in the thalamus and its connections. Structural and diffusion tensor MRI scans were obtained from 16 AD patients and 22 demographically similar healthy Volunteers. The thalamus, hippocampus, and amygdala were automatically segmented using our locally developed algorithm, and group comparisons were carried out for each Surface vertex. We also employed Probabilistic diffusion tractography to obtain connectivity measures between individual thalamic voxels and hippocampus/amygdala voxels and to segment the internal medullary lamina (IML). Shape analysis showed significant bilateral regional atrophy in the dorsal-medial part of the thalamus in AD patients compared to controls. Probabilistic tractography demonstrated that these regions are mainly connected with the hippocampus, temporal, and prefrontal cortex. Intrathalamic FA comparisons showed reductions in the anterodorsal region of thalamus. Intrathalamic tractography from this region revealed that the IML was significantly smaller in AD patients than in controls. We suggest that these changes can be attributed to the degeneration of the anterodorsal and intralaminar nuclei, respectively. In addition, based on previous neuropathological reports, ventral and dorsal-medial shape change in the thalamus in AD patients is likely to be driven by IML atrophy. This combined shape and connectivity analysis provides MRI evidence of regional thalamic degeneration in AD. (c) 2009 Elsevier Inc. All rights reserved. Show less
Cremers, H.R.; Demenescu, L.R.; Aleman, A.; Renken, R.; Tol, M.J. van; Wee, N.J.A. van der; ... ; Roelofs, K. 2010
Neuroticism is associated with the experience of negative affect and the development of affective disorders. While evidence exists for a modulatory role of neuroticism on task induced brain... Show moreNeuroticism is associated with the experience of negative affect and the development of affective disorders. While evidence exists for a modulatory role of neuroticism on task induced brain activity, it is unknown how neuroticism affects brain connectivity, especially the crucial coupling between the amygdala and the prefrontal cortex. Here we investigate this relation between functional connectivity and personality in response to negative facial expressions. Sixty healthy control participants, from the Netherlands Study on Depression and Anxiety (NESDA), were scanned during an emotional faces gender decision task. Activity and functional amygdala connectivity (psycho-physiological interaction [PPI]) related to faces of negative emotional valence (angry, fearful and sad) was compared to neutral facial expressions, while neuroticism scores were entered as a regressor. Activity for fearful compared to neutral faces in the dorsomedial prefrontal (dmPFC) cortex was positively correlated with neuroticism scores. PPI analyses revealed that right amygdala-dmPFC connectivity for angry and fearful compared to neutral faces was positively correlated with neuroticism scores. In contrast, left amygdala-anterior cingulate cortex (ACC) connectivity for angry, fearful and sad compared to neutral faces was negatively related to neuroticism levels. DmPFC activity has frequently been associated with self-referential processing in social cognitive tasks. Our results therefore suggest that high neurotic participants display stronger self-referential processing in response to negative emotional faces. Second, in line with previous reports on ACC function, the negative correlation between amygdala-ACC connectivity and neuroticism scores might indicate that those high in neuroticism display diminished control function of the ACC over the amygdala. These connectivity patterns might be associated with vulnerability to developing affective disorders such as depression and anxiety. (C) 2009 Elsevier Inc. All rights reserved. Show less
