Browsing by Subject "Diffusion tensor imaging"

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Open Access
Cortical connectivity in the face of congenital structural changes—A case of homozygous LAMC3 mutation
(John Wiley & Sons Ltd., 2021-08) Demirayak, P.; Oğuz, Kader Karlı; Üstün, Fatma Seyhun; Ürgen, Buse Merve; Topaç, Yasemin; Gilani, İrtiza; Kansu, T.; Saygı, S.; Özçelik, Tayfun; Boyacı, Hüseyin; Doerschner, Katja
The homozygous LAMC3 gene mutation is associated with severe bilateral smoothening and thickening of the lateral occipital cortex . Despite this and further significant changes in gray matter structure, a patient harboring this mutation exhibited a range of remarkably intact perceptual abilities . One possible explanation of this perceptual sparing could be that the white matter structural integrity and functional connectivity in relevant pathways remained intact. To test this idea, we used diffusion tensor and functional magnetic resonance imaging to investigate functional connectivity in resting-state networks in major structural pathways involved in object perception and visual attention and corresponding microstructural integrity in a patient with homozygous LAMC3 mutation and sex, age, education, and socioeconomically matched healthy control group. White matter microstructural integrity results indicated widespread disruptions in both intra- and interhemispheric structural connections except inferior longitudinal fasciculus. With a few exceptions, the functional connectivity between the patient's adjacent gray matter regions of major white matter tracts of interest was conserved. In addition, functional localizers for face, object, and place areas showed similar results with a representative control, providing an explanation for the patient's intact face, place, and object recognition abilities. To generalize this finding, we also compared functional connectivity between early visual areas and face, place, and object category-selective areas, and we found that the functional connectivity of the patient was not different from the control group. Overall, our results provided complementary information about the effects of LAMC3 gene mutation on the human brain including intact temporo-occipital structural and functional connectivity that are compatible with preserved perceptual abilities.
Open Access
A diffusion tensor imaging study in schizophrenia patients with clozapine induced obsessive compulsive symptoms
(John Wiley and Sons, Ltd, 2022-11-16) Bıçakçı Ay, Ş.; Özçelik Eroğlu, E.; Has, Arzu Ceylan; Ertuğrul, A.; Oğuz, Kader K.
Objective The aim of this study was to evaluate brain connectivity by diffusion tensor imaging (DTI) in schizophrenia patients with clozapine-induced obsessive compulsive symptoms (OCS). Methods Eighteen schizophrenia patients, nine of which had clozapine-induced OCS (Clz-OCS (+)), 9 without OCS (Clz-OCS (−)) and 9 healthy controls were included. Psychopathology was evaluated with Positive and Negative Syndrome Scale and Yale-Brown Obsession and Compulsion Scale in the patient groups. All groups were assesed with neurocognitive tests and DTI. Results Tract-Based Spatial Statistics based comparison of DTI revealed lower fractional anisotropy in the genu of corpus callosum (CC), right cingulum, left frontal white matter (WM) in the Clz-OCS (+) group, compared to controls. Fractional anisotropy was found to be lower in the bilateral occipital WM and higher in the bilateral medial temporal regions, anterior limb of internal capsule, cingulum, frontoparietal peripheral WM, right external capsule and genu of CC in Clz-OCS (+) patients compared to Clz-OCS (−). Conclusions WM integrity in several pathways such as cortico-striato-thalamo-cortical circuitry and orbito-frontal tracts seems to be affected differently in patients with Clz-OCS (+). Different neuroplastic effects of clozapine leading to occurrence of OCS in a subgroup of patients is possible, and needs further evaluation by longitudinal follow-up studies.
Open Access
Effect of clozapine on white matter integrity in patients with schizophrenia: a diffusion tensor imaging study
(Elsevier, 2014) Ozcelik-Eroglu, E.; Ertugrul, A.; Oguz, K. K.; Has, A. C.; Karahan, S.; Yazici, M. K.
Several diffusion tensor imaging (DTI) studies have reported disturbed white matter integrity in various brain regions in patients with schizophrenia, whereas only a few studied the effect of antipsychotics on DTI measures. The aim of this study was to investigate the effect of 12 weeks of clozapine treatment on DTI findings in patients with schizophrenia, and to compare the findings with those in unaffected controls. The study included 16 patients with schizophrenia who were assessed with the Positive and Negative Syndrome Scale, a neurocognitive test battery, and DTI at baseline and 12 weeks after the initiation of clozapine treatment. Eight unaffected controls were assessed once with the neurocognitive test battery and DTI. Voxel-wise analysis of DTI data was performed via tract-based spatial statistics (TBSS). Compared with the control group, the patient group exhibited lower fractional anisotropy (FA) in 16 brain regions, including the bilateral superior longitudinal fasciculi, inferior fronto-occipital fasciculi, superior and inferior parietal lobules, cingulate bundles, cerebellum, middle cerebellar peduncles, and left inferior longitudinal fasciculus, whereas the patients had higher FA in six regions, including the right parahippocampus, left anterior thalamic radiation, and right posterior limb of the internal capsule before clozapine treatment. After 12 weeks of treatment with clozapine, white matter FA was increased in widespread brain regions. In two of the regions where FA had initially been lower in patients compared with controls (left inferior fronto-occipital fasciculus and superior parietal lobule), clozapine appeared to increase FA. An improvement in semantic fluency was correlated with the increase in FA value in the left inferior fronto-occipital fasciculus. An increase in FA following 12 weeks of treatment with clozapine suggests that this treatment alters white matter microstructural integrity in patients with schizophrenia previously treated with typical and/or atypical antipsychotics and, in some locations, reverses a previous deficit. © 2014 Elsevier Ireland Ltd.
Open Access
The effect of early life stress on brain white matter integrity and working memory performance
(2019-08) Arslan, Seda
Former studies revealed that exposure to early life adversity is correlated with alterations in the white matter structure, particularly, in the areas associated with executive functioning and memory. Those alterations include both volume and microstructural white matter integrity reductions in the brain. A vast amount of the studies focused on volume reductions, and it is not clear whether the alterations in the white matter integrity is associated with cognitive functioning. The current study investigated the influence of early life stress on white matter integrity in the anterior cingulate cortex (ACC)and corpus callosum (CC) among the forty-six healthy participants. Participants were split into two groups based on the Childhood Experience of Care and Abuse Questionnaire (CECA.Q). Participants with relatively low early life stress were compared with participants with relatively high early life stress on fractional anisotropy (FA) and mean diffusivity (MD) values in the ACC and CC. Another analysis investigated the working memory performance of the participants in the n-back task. Findings revealed that low-level early life stress did not significantly differ from high-level of early life stress in terms of FA values. However, there were significantly higher MD values in the high-level early life stress group compared to low-level early life stress group. In terms of cognitive performance, there were no performance differences between the two groups on the n-back task. The findings suggest that the high level of early life stress is associated with subtle white matter integrity changes in the brain but does not affect the performance.
Open Access
Effects of recreational cannabis use and subclinical psychosis risk on brain white matter integrity and structural connectivity in adolescence
(2022-06) Atmaca, Hande Ezgi
The impact of cannabis use on the psychosis risk in the healthy population has been less examined in the literature. Furthermore, previous diffusion tensor imag-ing and structural connectivity studies investigating the effects of cannabis use and psychosis risk offer contradictory results. To address these gaps and inconsistencies in the literature, the author examined whether recreational use of cannabis increases the risk of subclinical psychosis. The author further ex-amined the relationship between recreational cannabis use, subclinical psychosis, and white matter microstructure or structural network connectivity. Twenty-five adolescent cannabis users and 25 demographically matched controls participated in the study. The Cannabis Experience Questionnaire (CEQ) was used to assess cannabis consumption. Subclinical psychosis was evaluated with the Community Assessment of Psychic Experience (CAPE-42) questionnaire. While ROI-based Tract Based Spatial Statistics (TBSS) was used to examine white matter integrity in specified region of interests, Structural Connectivity Analysis was performed to examine brain structural topology. White matter integrity was assessed by four diffusion tensor derived measures: fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity, while structural network topology was examined by several graph-theory metrics: global efficiency, local efficiency and clustering coefficient. In order to eliminate possible confounding effects of alcohol and to-bacco use, weekly alcohol and daily tobacco consumption were also considered. The findings revealed that cannabis users scored higher on subclinical psychosis compared to non-users. ROI-based TBSS analysis indicated that cannabis use and subclinical psychosis do not affect white matter integrity in corpus collosum and superior longitudinal fasciculus. Similarly, the network connectivity parame-ters were not affected by the recreational cannabis use and psychosis risk. These results might indicate that recreational cannabis use increases the psychosis risk in adolescence, but that recreational cannabis use and subclinical psychosis risk together do not affect white matter microstructure and topology.
Open Access
Influence of cigarette smoking on white matter in patients with clinically isolated syndrome as detected by diffusion tensor imaging
(Turkish Society of Radiology, 2016) Durhan, G.; Diker, S.; Has, A. C.; Karakaya, J.; Kurne, A. T.; Oguz, K. K.
PURPOSE Cigarette smoking has been associated with increased occurrence of multiple sclerosis (MS), as well as clinical disability and disease progression in MS. We aimed to assess the effects of smoking on the white matter (WM) in patients with clinically isolated syndrome (CIS) using diffusion tensor imaging. METHODS Smoker patients with CIS (n=16), smoker healthy controls (n=13), nonsmoker patients with CIS (n=17) and nonsmoker healthy controls (n=14) were included. Thirteen regions-of-interest including nonenhancing T1 hypointense lesion and perilesional WM, and 11 normal-appearing white matter (NAWM) regions were drawn on color-coded fractional anisotropy (FA) maps. Lesion load was determined in terms of number and volume of WM hyperintensities. RESULTS A tendency towards greater lesion load was found in smoker patients. T1 hypointense lesions and perilesional WM had reduced FA and increased mean diffusivity to a similar degree in smoker and nonsmoker CIS patients. Compared with healthy smokers, smoker CIS patients had more extensive NAWM changes shown by increased mean diffusivity. There was no relationship between diffusion metrics and clinical disability scores, duration of the disease and degree of smoking exposure. CONCLUSION Smoker patients showed a tendency towards having greater number of WM lesions and displayed significantly more extensive NAWM abnormalities. © Turkish Society of Radiology 2016.
Open Access
Schizophrenia polygenic risk score influence on white matter microstructure
(Elsevier, 2020) Simões, B.; Vassos, E.; Shergill, S.; McDonald, C.; Toulopoulou, Timothea; Kalidindi, S.; Kane, F.; Murray, R.; Bramon, E.; Ferreira, H.; Prata, D.
Schizophrenia (SZ) and bipolar disorder (BD) are highly heritable, share symptomatology, and have a polygenic architecture. The impact of recent polygenic risk scores (PRS) for psychosis, which combine multiple genome-wide associated risk variations, should be assessed on heritable brain phenotypes also previously associated with the illnesses, for a better understanding of the pathways to disease. We have recently reported on the current SZ PRS's ability to predict 1st episode of psychosis case-control status and general cognition. Herein, we test its penetrance on white matter microstructure, which is known to be impaired in SZ, in BD and their relatives, using 141 participants (including SZ, BP, relatives of SZ or BP patients, and healthy volunteers), and two white matter integrity indexes: fractional anisotropy (FA) and mean diffusivity (MD). No significant correlation between the SZ PRS and FA or MD was found, thus it remains unclear whether white matter changes are primarily associated with SZ genetic risk profiles.
Open Access
Structural brain alterations of Down’s syndrome in early childhood evaluation by DTI and volumetric analyses
(Springer Verlag, 2017) Gunbey, H. P.; Bilgici, M. C.; Aslan, K.; Has, A. C.; Ogur, M. G.; Alhan, A.; Incesu, L.
Objectives: To provide an initial assessment of white matter (WM) integrity with diffusion tensor imaging (DTI) and the accompanying volumetric changes in WM and grey matter (GM) through volumetric analyses of young children with Down’s syndrome (DS). Methods: Ten children with DS and eight healthy control subjects were included in the study. Tract-based spatial statistics (TBSS) were used in the DTI study for whole-brain voxelwise analysis of fractional anisotropy (FA) and mean diffusivity (MD) of WM. Volumetric analyses were performed with an automated segmentation method to obtain regional measurements of cortical volumes. Results: Children with DS showed significantly reduced FA in association tracts of the fronto-temporo-occipital regions as well as the corpus callosum (CC) and anterior limb of the internal capsule (p < 0.05). Volumetric reductions included total cortical GM, cerebellar GM and WM volume, basal ganglia, thalamus, brainstem and CC in DS compared with controls (p < 0.05). Conclusion: These preliminary results suggest that DTI and volumetric analyses may reflect the earliest complementary changes of the neurodevelopmental delay in children with DS and can serve as surrogate biomarkers of the specific elements of WM and GM integrity for cognitive development. Key Points: • DS is the most common genetic cause of intellectual disability. • WM and GM structural alterations represent the neurological features of DS. • DTI may identify the earliest aging process changes. • DTI-volumetric analyses can serve as surrogate biomarkers of neurodevelopment in DS. © 2016, European Society of Radiology.