| 51. |
- Kotilahti, Kalle, et al.
(författare)
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Hemodynamic Responses to Speech and Music in Newborn Infants
- 2010
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 31:4, s. 595-603
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Tidskriftsartikel (refereegranskat)abstract
- We used near-infrared spectroscopy (NIRS) to study responses to speech and music on the auditory cortices of 13 healthy full-term newborn infants during natural sleep. The purpose of the study was to investigate the lateralization of speech and music responses at this stage of development. NIRS data was recorded from eight positions on both hemispheres simultaneously with electroencephalography, electrooculography, electrocardiography, pulse oximetry, and inclinometry. In 11 subjects, statistically significant (P < 0.02) oxygenated (HbO(2)) and total hemoglobin (HbT) responses were recorded. Both stimulus types elicited significant HbO(2) and HUT responses on both hemispheres in five subjects. Six of the 11 subjects had positive HbO(2) and HbT responses to both stimulus types, whereas one subject had negative responses. Mixed positive and negative responses were observed in four neonates. On both hemispheres, speech and music responses were significantly correlated (r = 0.64; P = 0.018 on the left hemisphere (LH) and r = 0.60; P = 0.029 on the right hemisphere (RH)). On the group level, the average response to the speech stimuli was statistically significantly greater than zero in the LH, whereas responses on the RH or to the music stimuli did not differ significantly from zero. This suggests a more coherent response to speech on the LH. However, significant differences in lateralization of the responses or mean response amplitudes of the two stimulus types were not observed on the group level. Hum Brain Mapp 31:595-603, 2010. (C) 2009 Wiley-Liss, Inc.
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| 52. |
- Kühn, Simone, et al.
(författare)
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The dynamics of change in striatal activity following updating training
- 2013
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 34:7, s. 1530-1541
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Tidskriftsartikel (refereegranskat)abstract
- Increases in striatal activity have been suggested to mediate training-related improvements in working-memory ability. We investigated the temporal dynamics of changes in task-related brain activity following training of working memory. Participants in an experimental group and an active control group, trained on easier tasks of a constant difficulty in shorter sessions than the experimental group, were measured before, after about 1 week, and after more than 50 days of training. In the experimental group an initial increase of working-memory related activity in the functionally defined right striatum and anatomically defined right and left putamen was followed by decreases, resulting in an inverted u-shape function that relates activity to training over time. Activity increases in the striatum developed slower in the active control group, observed at the second posttest after more than 50 days of training. In the functionally defined left striatum, initial activity increases were maintained after more extensive training and the pattern was similar for the two groups. These results shed new light on the relation between activity in the striatum (especially the putamen) and the effects of working memory training, and illustrate the importance of multiple measurements for interpreting effects of training on regional brain activity.
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| 53. |
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| 54. |
- Kurth, F, et al.
(författare)
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Large-scale analysis of structural brain asymmetries during neurodevelopment : Associations with age and sex in 4265 children and adolescents.
- 2024
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Ingår i: Human Brain Mapping. - 1065-9471 .- 1097-0193. ; 45:11, s. e26754-
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 55. |
- Lampinen, Björn, et al.
(författare)
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Searching for the neurite density with diffusion MRI : Challenges for biophysical modeling
- 2019
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 40:8, s. 2529-2545
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Tidskriftsartikel (refereegranskat)abstract
- In vivo mapping of the neurite density with diffusion MRI (dMRI) is a high but challenging aim. First, it is unknown whether all neurites exhibit completely anisotropic (“stick-like”) diffusion. Second, the “density” of tissue components may be confounded by non-diffusion properties such as T2 relaxation. Third, the domain of validity for the estimated parameters to serve as indices of neurite density is incompletely explored. We investigated these challenges by acquiring data with “b-tensor encoding” and multiple echo times in brain regions with low orientation coherence and in white matter lesions. Results showed that microscopic anisotropy from b-tensor data is associated with myelinated axons but not with dendrites. Furthermore, b-tensor data together with data acquired for multiple echo times showed that unbiased density estimates in white matter lesions require data-driven estimates of compartment-specific T2 values. Finally, the “stick” fractions of different biophysical models could generally not serve as neurite density indices across the healthy brain and white matter lesions, where outcomes of comparisons depended on the choice of constraints. In particular, constraining compartment-specific T2 values was ambiguous in the healthy brain and had a large impact on estimated values. In summary, estimating neurite density generally requires accounting for different diffusion and/or T2 properties between axons and dendrites. Constrained “index” parameters could be valid within limited domains that should be delineated by future studies.
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| 56. |
- Lassalle, Amandine, et al.
(författare)
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Hypersensitivity to low intensity fearful faces in autism when fixation is constrained to the eyes.
- 2017
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Ingår i: Human brain mapping. - : Wiley. - 1097-0193 .- 1065-9471. ; 38:2, s. 5943-57
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies that showed decreased brain activation in people with autism spectrum disorder (ASD) viewing expressive faces did not control that participants looked in the eyes. This is problematic because ASD is characterized by abnormal attention to the eyes. Here, we collected fMRI data from 48 participants (27 ASD) viewing pictures of neutral faces and faces expressing anger, happiness, and fear at low and high intensity, with a fixation cross between the eyes. Group differences in whole brain activity were examined for expressive faces at high and low intensity versus neutral faces. Group differences in neural activity were also investigated in regions of interest within the social brain, including the amygdala and the ventromedial prefrontal cortex (vmPFC). In response to low intensity fearful faces, ASD participants showed increased activation in the social brain regions, and decreased functional coupling between the amygdala and the vmPFC. This oversensitivity to low intensity fear coupled with a lack of emotional regulation capacity could indicate an excitatory/inhibitory imbalance in their socio-affective processing system. This may result in social disengagement and avoidance of eye-contact to handle feelings of strong emotional reaction. Our results also demonstrate the importance of careful control of gaze when investigating emotional processing in ASD. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.
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| 57. |
- Lebedev, Alexander V., et al.
(författare)
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Finding the self by losing the self : Neural correlates of ego-dissolution under psilocybin
- 2015
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 36:8, s. 3137-3153
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Tidskriftsartikel (refereegranskat)abstract
- Ego-disturbances have been a topic in schizophrenia research since the earliest clinical descriptions of the disorder. Manifesting as a feeling that one's self, ego, or I is disintegrating or that the border between one's self and the external world is dissolving, ego-disintegration or dissolution is also an important feature of the psychedelic experience, such as is produced by psilocybin (a compound found in magic mushrooms). Fifteen healthy subjects took part in this placebo-controlled study. Twelve-minute functional MRI scans were acquired on two occasions: subjects received an intravenous infusion of saline on one occasion (placebo) and 2 mg psilocybin on the other. Twenty-two visual analogue scale ratings were completed soon after scanning and the first principal component of these, dominated by items referring to ego-dissolution, was used as a primary measure of interest in subsequent analyses. Employing methods of connectivity analysis and graph theory, an association was found between psilocybin-induced ego-dissolution and decreased functional connectivity between the medial temporal lobe and high-level cortical regions. Ego-dissolution was also associated with a disintegration of the salience network and reduced interhemispheric communication. Addressing baseline brain dynamics as a predictor of drug-response, individuals with lower diversity of executive network nodes were more likely to experience ego-dissolution under psilocybin. These results implicate MTL-cortical decoupling, decreased salience network integrity, and reduced inter-hemispheric communication in psilocybin-induced ego disturbance and suggest that the maintenance of selfor ego, as a perceptual phenomenon, may rest on the normal functioning of these systems. Hum Brain Mapp 36:3137-3153, 2015.
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| 58. |
- Lebedev, Alexander V., et al.
(författare)
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LSD-Induced Entropic Brain Activity Predicts Subsequent Personality Change
- 2016
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 37:9, s. 3203-3213
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Tidskriftsartikel (refereegranskat)abstract
- Personality is known to be relatively stable throughout adulthood. Nevertheless, it has been shown that major life events with high personal significance, including experiences engendered by psychedelic drugs, can have an enduring impact on some core facets of personality. In the present, balanced-order, placebo-controlled study, we investigated biological predictors of post-lysergic acid diethylamide ( LSD) changes in personality. Nineteen healthy adults underwent resting state functional MRI scans under LSD ( 75 mu g, I. V.) and placebo ( saline I. V.). The Revised NEO Personality Inventory ( NEO-PI-R) was completed at screening and 2 weeks after LSD/placebo. Scanning sessions consisted of three 7.5-min eyes-closed resting-state scans, one of which involved music listening. A standardized preprocessing pipeline was used to extract measures of sample entropy, which characterizes the predictability of an fMRI time-series. Mixed-effects models were used to evaluate drug-induced shifts in brain entropy and their relationship with the observed increases in the personality trait openness at the 2-week follow-up. Overall, LSD had a pronounced global effect on brain entropy, increasing it in both sensory and hierarchically higher networks across multiple time scales. These shifts predicted enduring increases in trait openness. Moreover, the predictive power of the entropy increases was greatest for the music-listening scans and when ego-dissolution was reported during the acute experience. These results shed new light on how LSD-induced shifts in brain dynamics and concomitant subjective experience can be predictive of lasting changes in personality.
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| 59. |
- Lenfeldt, Niklas, et al.
(författare)
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Alterations in white matter microstructure are associated with goal-directed upper-limb movement segmentation in children born extremely preterm
- 2017
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Ingår i: Human Brain Mapping. - Hoboken : Wiley-Blackwell. - 1065-9471 .- 1097-0193. ; 38:10, s. 5051-5068
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Tidskriftsartikel (refereegranskat)abstract
- Altered white matter microstructure is commonly found in children born preterm (PT), especially those born at an extremely low gestational age (GA). These children also commonly show disturbed motor function. This study explores the relation between white matter alterations and upperlimb movement segmentation in 41 children born PT (19 girls), and 41 children born at term (18 girls) at 8 years. The PT group was subdivided into extremely PT (E-PT; GA = 25–27 weeks, N = 10), very PT (V-PT; GA = 28–32 weeks, N = 13), and moderately PT (M-PT; GA = 33–35 weeks, N = 18). Arm/hand preference (preferred/non-preferred) was determined through object interactions and the brain hemispheres were designated accordingly. White matter alterations were assessed using diffusion tensor imaging in nine areas, and movement segmentation of the body-parts head, shoulder, elbow, and wrist were registered during a unimanual goal-directed task. Increased movement segmentation was demonstrated consistently on the preferred side in the E-PT group compared with the term born group. Also compared with the term born peers, the E-PT group demonstrated reduced fractional anisotropy (FA) in the cerebral peduncle (targeting the corticospinal tract) in the hemisphere on the non-preferred side and in the splenium of corpus callosum. In contrast, in the anterior internal capsule on the preferred side, the E-PT group had increased FA. Lower FA in the cerebral peduncle, but higher FA in the anterior internal capsule, was associated with increased movement segmentation across body-parts in a contralateral manner. The results suggest that impaired development of sensorimotor tracts in E-PT children could explain a sub-optimal spatiotemporal organization of upper-limb movements.
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| 60. |
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