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Brain Insulin Action in the Control of Metabolism in Humans
Published in André Kleinridders, Physiological Consequences of Brain Insulin Action, 2023
Thanks to neuroimaging techniques, brain insulin action can be spatially localized by evaluating the brain’s response to cognitive demanding tasks such as, for example, the investigation of the role of insulin in memory or reward-related processes. Since the brain is active even in the absence of external cues, spontaneous BOLD fluctuations are located in all brain regions. Brain activity can therefore be evaluated under the so-called “resting-state” or “intrinsic condition”. To this end, subjects lie in the MRI scanner with their eyes open or closed without performing any task. Resting-state fMRI thus greatly enhances the translation of fMRI into clinical care (for review, see (59)).
Positron Emission Tomography and Neuropsychological Studies in Dementia
Published in Robert E. Becker, Ezio Giacobini, Alzheimer Disease, 2020
Randolph W. Parks, Robert E. Becker, Kathryn L. Dodrill, Bettina A. Bennett, David J. Crockett, Trevor A. Hurwitz, Patrick L. McGeer, Edith G. McGeer
The major problem with resting state studies is that there is no opportunity to observe simultaneous brain behavior relationships. Recent advances in testing procedures allow the examiner to obtain two separate PET scans during a single testing session (Gur et al., 1983) or to perform statistical corrections that account for covariance (Cronbach & Furby, 1970; Weisberg, 1979; Bartlett et al., 1987). At this point, it should be noted that much of the PET scan data does not meet the assumptions necessary to allow the data to be analyzed using regression analysis. In these cases, it might be much more appropriate to use Multiple Classification Analysis (Andrews, 1973). This type of analysis is associated with much less stringent set of assumptions regarding the nature of the data and still allows for the examination of general differences in patterns of analysis.
Magnetic Resonance Imaging
Published in Shoogo Ueno, Bioimaging, 2020
Block design, event-related design, and resting state are the three main approaches by which brain activity is induced and then measured. In block design, the blocks that continuously produce brain activity by providing stimulation over several consecutive seconds or minutes to test subjects and the subsequent blocks that do not provide stimulation for several seconds or minutes are alternately arranged. The MRI signals between these two blocks are statistically analyzed, and then, the regions presenting significant differences are extracted. In event-related design, one-time stimulation is delivered, and subsequently, MRI signal responses, including time changes, are acquired. Thereafter, second-time or further stimulation is delivered with sufficient intervals. The advantage of this method is that timely information is also acquired. Resting state is a technique that was established recently. It deals with brain activity that is spontaneously produced without any particular external stimulation. Focusing on periodic fluctuations in individual voxel BOLD signals in places with spontaneously occurring activity enables the extraction of combinations of voxels with high correlation to these periodic fluctuations. A high correlation means some type of coupling between neurons, making it possible to locate neural network structures in the brain from measured results.
Altered resting-state cerebellar-cerebral functional connectivity in patients with end-stage renal disease
Published in Renal Failure, 2023
Jie Fang, Yingying Miao, Fan Zou, Yarui Liu, Jiangle Zuo, Xiangming Qi, Haibao Wang
Resting-state fMRI is a method that indirectly infers information about brain activity by measuring Blood-Oxygen-Level Dependent (BOLD) signal. The temporal correlations of BOLD signals in different brain regions can be used to reflect brain FC [30]. The abnormalities in resting-state fMRI connectivity reflect alterations in the interactions among different brain regions [31]. Considering that DMN, ECN, ALN, and SMN are abnormal in ESRD, and that cerebellar sub-regions can identify the cerebellar-cerebral DMN, ECN, ALN, and SMN, we hypothesized that the cerebellum-cerebral FC is abnormal and related to cognitive impairment in ESRD patients. Therefore, the present study aimed to explore whether the cerebellar-cerebral FC is altered in ESRD patients with cerebellar sub-regions as seeds using resting-state fMRI, and further investigate the relationship between the altered FC, neuropsychological function, and clinical parameters in patients with ESRD.
Altered connectivity of default mode and executive control networks among female patients with persistent post-concussion symptoms
Published in Brain Injury, 2023
Jimmy K. Y. Wong, Nathan W. Churchill, Simon J. Graham, Andrew J. Baker, Tom A. Schweizer
This study provided novel insights into brain function and structure for a comparatively understudied cohort, consisting of female mTBI patients with persistent symptoms, drawn from the general population. Although significant effects were identified, the study had some limitations that should be acknowledged. The modest sample size may have contributed to the limited correlations with clinical indices, and future replication studies are needed to confirm the observed findings. This will also be important given the clinical and pathophysiological heterogeneity of individuals with persistent post-concussion symptoms. Future work should also include measures of cerebral blood flow and/or cerebrovascular reactivity, to understand to what extent FC effects are driven by cerebrovascular changes, as opposed to neurometabolic effects. Similarly, more advanced models of water diffusion, such as diffusion kurtosis imaging (DKI) and neurite orientation dispersion and density imaging (NODDI), may help to better interpret the observed microstructural effects. Finally, the present study is an observational study with resting-state functional imaging. As such, any inferences about whether hyperconnectivity represents compensation or pathology are indirect, supported by a combination of clinical data and prior literature. To better address these issues, prospective longitudinal studies are needed, to track the evolution of cognition and brain function from early injury (pre-injury), through to the development of persistent post-concussion symptoms.
Problem-solving training modifies cognitive functioning and related functional connectivity in healthy adults
Published in Neuropsychological Rehabilitation, 2023
Béatrice Alescio-Lautier, Caroline Chambon, Claire Deshayes, Jean-Luc Anton, Guy Escoffier, Marie-Hélène Ferrer, Véronique Paban
Successful problem-solving training seemed to have an effect on regional functional connectivity in brain networks involving the DMN, the AN, and the VN. Changes in the connectivity of resting state-networks following problem-solving-based training corroborate studies using different cognitive training programmes (Cao et al., 2016; Chapman et al., 2017; Fink et al., 2015; 2018; Jolles et al., 2013). In studies conducted by Fink et al., these brain changes occurred after 3 weeks of verbal divergent thinking training consisting of 144 exercises organized in 18 training modules of 20 min each. For these authors, as exposures occur, the subject will refine his strategy until his potential is fully optimized, which will lead to changes in brain function. These modifications could reflect changes in the brain assessed by resting-state functional connectivity. We used a similar number of exercises (between 120 and 150 closed-ended problems) and training sessions (24 training sessions). However, our training was more widely distributed, with two sessions per week compared to six sessions per week in the study by Fink et al. Although the nature of the training was different between the two studies, our results support the idea that training must be long enough to cause changes in the resting state connectivity. We observe these changes 6 weeks after training indicating that they can be maintained over time. This result is in agreement with data from Cao et al. (2016) showing changes in brain connectivity up to 1 year after training.