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1,116 result(s) for "Gray Matter - physiology"
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Cerebral blood flow and arterial transit time responses to exercise training in older adults
•Home-based high-intensity interval training increases cardiorespiratory fitness in older adults.•High cardiorespiratory fitness gains were associated with cerebral blood flow reductions.•Exercise training did not affect arterial transit time or cognitive function in older adults. Brain vascular health worsens with age, as is made evident by resting grey matter cerebral blood flow (CBFGM) reductions and lengthening arterial transit time (ATTGM). Exercise training can improve aspects of brain health in older adults, yet its effects on CBFGM and ATTGM remain unclear. This randomised controlled trial assessed responses of CBFGM and ATTGM to a 26 week exercise intervention in 65 healthy older adults (control: n = 33, exercise: n = 32, aged 60–81 years), including whether changes in CBFGM or ATTGM were associated with changes in cognitive functions. Multiple-delay pseudo-continuous arterial spin labelling data were used to estimate resting global and regional CBFGM and ATTGM. Results showed no between-group differences in CBFGM or ATTGM following the intervention. However, exercise participants with the greatest cardiorespiratory gains (n = 17; ∆V̇O2peak >2 mL/kg/min) experienced global CBFGM reductions (-4.0 [-7.3, -0.8] mL/100 g/min). Cognitive functions did not change in either group and changes were not associated with changes in CBFGM or ATTGM. Our findings indicate that exercise training in older adults may induce global CBFGM reductions when high cardiorespiratory fitness gains are induced, but this does not appear to affect cognitive functions.
A longitudinal, randomized experimental pilot study to investigate the effects of airborne infrasound on human mental health, cognition, and brain structure
Airborne infrasound (IS; emitted by e.g., large machinery, wind farms) is ubiquitous in technologized environments. Health hazards are controversially discussed at present. This study investigated long-term effects of IS on brain (regional grey matter volume; rGMV) and behavior in humans. Specifically engineered infrasonic (6 Hz, 80–90 dB) vs. sham devices were installed in participants’ (N = 38) bedrooms and active for 28 nights. Somatic and psychiatric symptoms, sound-sensitivity, sleep quality, cognitive performance, and structural MRI were assessed pre-post. Null findings emerged for all behavioral variables. Exploratory analyses revealed a trend ( p  = .083) with individuals exposed to IS reporting more physical weakness at post-test ( d  = 0.38). Voxel-based morphometry (VBM) revealed no rGMV increases, but there were decreases within clusters in the cerebellum VIIIa (bilateral) and left angular gyrus (BA39) in verum. In conclusion, IS does not affect healthy individuals on a global scale. However, future trials should consider more fine-grained specific effects, combining self-report with physiological assessments, particularly directed at bodily sensations and perception. As no brain-behavior-links could be established, the identified grey matter decline cannot be interpreted in terms of potential harmfulness vs. improvement through IS-exposure. Parameters that may best reflect brain changes as established in the present study include motor function, sensory processing/ bodily- and motor-perceptions, working memory, and higher auditory processing (i.e., language-related tasks), which are hence potential target variables for further research.
Gray matter volume is associated with rate of subsequent skill learning after a long term training intervention
The ability to predict learning performance from brain imaging data has implications for selecting individuals for training or rehabilitation interventions. Here, we used structural MRI to test whether baseline variations in gray matter (GM) volume correlated with subsequent performance after a long-term training of a complex whole-body task. 44 naïve participants were scanned before undertaking daily juggling practice for 6weeks, following either a high intensity or a low intensity training regime. To assess performance across the training period participants' practice sessions were filmed. Greater GM volume in medial occipito-parietal areas at baseline correlated with steeper learning slopes. We also tested whether practice time or performance outcomes modulated the degree of structural brain change detected between the baseline scan and additional scans performed immediately after training and following a further 4weeks without training. Participants with better performance had higher increases in GM volume during the period following training (i.e., between scans 2 and 3) in dorsal parietal cortex and M1. When contrasting brain changes between the practice intensity groups, we did not find any straightforward effects of practice time though practice modulated the relationship between performance and GM volume change in dorsolateral prefrontal cortex. These results suggest that practice time and performance modulate the degree of structural brain change evoked by long-term training regimes. •Inter-individual differences in brain structure correlate with subsequent performance outcome.•Performance outcome plays an important role in positive structural brain change.•Performance outcome and amount of practice modulate structural brain change.
Tai Chi Chuan vs General Aerobic Exercise in Brain Plasticity: A Multimodal MRI Study
This study contrasted the impact of Tai Chi Chuan and general aerobic exercise on brain plasticity in terms of an increased grey matter volume and functional connectivity during structural magnetic resonance imaging (sMRI) and resting-state functional magnetic resonance imaging (rs-fMRI), explored the advantages of Tai Chi Chuan in improving brain structure and function. Thirty-six college students were grouped into Tai Chi Chuan (Bafa Wubu of Tai Chi), general aerobic exercise (brisk walking) and control groups. Individuals were assessed with a sMRI and rs-fMRI scan before and after an 8-week training period. The VBM toolbox was used to conduct grey matter volume analyses. The CONN toolbox was used to conduct several seed-to-voxel functional connectivity analyses. We can conclude that compared with general aerobic exercise, eight weeks of Tai Chi Chuan exercise has a stronger effect on brain plasticity, which is embodied in the increase of grey matter volume in left middle occipital gyrus, left superior temporal gyrus and right middle temporal gyrus and the enhancement of functional connectivity between the left middle frontal gyrus and left superior parietal lobule. These findings demonstrate the potential and advantages of Tai Chi Chuan exercises in eliciting brain plasticity.
Behavioral correlates of changes in hippocampal gray matter structure during acquisition of foreign vocabulary
Experience can affect human gray matter volume. The behavioral correlates of individual differences in such brain changes are not well understood. In a group of Swedish individuals studying Italian as a foreign language, we investigated associations among time spent studying, acquired vocabulary, baseline performance on memory tasks, and gray matter changes. As a way of studying episodic memory training, the language learning focused on acquiring foreign vocabulary and lasted for 10weeks. T1-weighted structural magnetic resonance imaging and cognitive testing were performed before and after the studies. Learning behavior was monitored via participants' use of a smartphone application dedicated to the study of vocabulary. A whole-brain analysis showed larger changes in gray matter structure of the right hippocampus in the experimental group (N=33) compared to an active control group (N=23). A first path analyses revealed that time spent studying rather than acquired knowledge significantly predicted change in gray matter structure. However, this association was not significant when adding performance on baseline memory measures into the model, instead only the participants' performance on a short-term memory task with highly similar distractors predicted the change. This measure may tap similar individual difference factors as those involved in gray matter plasticity of the hippocampus. •We compared 10weeks of vocabulary learning with an active control condition.•Gray matter volume was measured with structural MR before and after training.•Vocabulary learning led to an increase in gray matter volume in right hippocampus.•Volume increases were predicted by baseline performance on a short-term memory task.
No long-term benefits from resistance training on brain grey matter volumes in active older adults at retirement age
Background Resistance training and other forms of physical exercise are commonly suggested to promote brain health, yet the relationship between resistance training and brain structure in aging is poorly understood. We examined the short- and long-term influence of one year of supervised resistance training at two different loadings on brain structure in aging. Methods In the LISA (LIve active Successful Ageing) study, well-functioning older adults at retirement age (mean age: 66 ± 2 years) were randomized to one year of heavy resistance training (HRT), moderate intensity training (MIT), or a non-exercising control group (CON). Magnetic resonance imaging (MRI) of the brain was performed at baseline, 1-, 2-, and 4-years follow ups. Trajectories of total grey matter, hippocampus, dorsolateral prefrontal cortex (dlPFC), ventrolateral prefrontal cortex (vlPFC), and white matter hyperintensities were analyzed in relation to changes in muscle strength. Results Individuals ( n  = 276) with MRI scans at all 4 timepoints were included (HRT, n  = 96; MIT, n  = 95; CON, n  = 85). Total grey matter volume decreased with time across all groups (F 3,819  = 231.549, p  < 0.001, η 2 = 0.46), as did hippocampal (F 3,819  = 310.07, p  < 0.001, η 2 = 0.53), vlPFC (F 3,818  = 74.380, p  < 0.001, η 2 = 0.21), and dlPFC (F 3,818  = 3.640, p = 0.013, η 2 = 0.01) volumes. White matter hyperintensity volumes increased (F 3,819  = 101.876, p  < 0.001, η 2 = 0.27). There were no significant group x time interactions for any of the brain structures. Additional cortical and subcortical vertex-wise analyses showed no group differences. Change in isometric leg strength was weakly associated with change in white matter hyperintensity volume across all individuals (r 2  = 0.01, p  = 0.048). Conclusions One year of resistance training in well-functioning older adults at retirement age did not influence volume changes in selected brain regions over a 4-year period. Trial registration The study was approved by the regional ethics committee and registered on clinicaltrials.gov 2014–04-24 (NCT02123641).
The Effect of Mindfulness Meditation on Impulsivity and its Neurobiological Correlates in Healthy Adults
Interest has grown in using mindfulness meditation to treat conditions featuring excessive impulsivity. However, while prior studies find that mindfulness practice can improve attention, it remains unclear whether it improves other cognitive faculties whose deficiency can contribute to impulsivity. Here, an eight-week mindfulness intervention did not reduce impulsivity on the go/no-go task or Barratt Impulsiveness Scale (BIS-11), nor produce changes in neural correlates of impulsivity (i.e. frontostriatal gray matter, functional connectivity, and dopamine levels) compared to active or wait-list control groups. Separately, long-term meditators (LTMs) did not perform differently than meditation-naïve participants (MNPs) on the go/no-go task. However, LTMs self-reported lower attentional impulsivity, but higher motor and non-planning impulsivity on the BIS-11 than MNPs. LTMs had less striatal gray matter, greater cortico-striatal-thalamic functional connectivity, and lower spontaneous eye-blink rate (a physiological dopamine indicator) than MNPs. LTM total lifetime practice hours (TLPH) did not significantly relate to impulsivity or neurobiological metrics. Findings suggest that neither short- nor long-term mindfulness practice may be effective for redressing impulsive behavior derived from inhibitory motor control or planning capacity deficits in healthy adults. Given the absence of TLPH relationships to impulsivity or neurobiological metrics, differences between LTMs and MNPs may be attributable to pre-existing differences.
A longitudinal, randomized experimental pilot study to investigate the effects of airborne ultrasound on human mental health, cognition, and brain structure
Ultrasound-(US) emitting sources are highly present in modern human environments (e.g., movement sensors, electric transformers). US affecting humans or even posing a health hazard remains understudied. Hence, ultrasonic (22.4 kHz) vs. sham devices were installed in participants’ bedrooms, and active for 28 nights. Somatic and psychiatric symptoms, sound-sensitivity, sleep quality, executive function, and structural MRI were assessed pre-post. Somatization (possible nocebo) and phasic alertness increased significantly in sham, accuracy in a flexibility task decreased significantly in the verum condition (indicating hastier responses). Effects were not sustained after p -level adjustment. Exploratory voxel-based morphometry (VBM) revealed regional grey matter (rGMV) but no regional white matter volume changes in verum (relative to placebo). rGMV increased in bilateral cerebellum VIIb/Crus II and anterior cingulate (BA24). There were rGMV decreases in two bilateral frontal clusters: in the middle frontal gyri/opercular part of inferior frontal gyrus (BA46, 44), and the superior frontal gyri (BA4 ,6, 8). No brain-behavior-links were identified. Given the overall pattern of results, it is suggested that ultrasound may particularly induce regional gray matter decline in frontal areas, however with yet unclear behavioral consequences. Given the localization of clusters, candidate behavioral variables for follow-up investigation are complex motor control/coordination, stress regulation, speech processing, and inhibition tasks. Trial registration : The trial was registered at NIH www.clinicaltrials.gov , trial identifier: NCT03459183, trial name: SonicBrain01, full trial protocol available here: https://clinicaltrials.gov/ct2/show/NCT03459183 .
Gray matter and intrinsic network changes in the posterior cingulate cortex after selective serotonin reuptake inhibitor intake
Preclinical studies have demonstrated that serotonin (5-HT) challenge changes neuronal circuitries and microarchitecture. However, evidence in human subjects is missing. Pharmacologic magnetic resonance imaging (phMRI) applying selective 5-HT reuptake inhibitors (SSRIs) and high-resolution structural and functional brain assessment is able to demonstrate the impact of 5-HT challenge on neuronal network morphology and functional activity. To determine how SSRIs induce changes in gray matter and neuronal activity, we conducted a longitudinal study using citalopram and escitalopram. Seventeen healthy subjects completed a structural and functional phMRI study with randomized, cross-over, placebo-controlled, double-blind design. Significant gray matter increases were observed (among other regions) in the posterior cingulate cortex (PCC) and the ventral precuneus after SSRI intake of 10days, while decreases were observed within the pre- and postcentral gyri (all P<0.05, family-wise error [FWE] corrected). Furthermore, enhanced resting functional connectivity (rFC) within the ventral precuneus and PCC was associated with gray matter increases in the PCC (all FWE Pcorr<0.05). Corroborating these results, whole-brain connectivity density, measuring the brain's functional network hubs, was significantly increased after SSRI-intake in the ventral precuneus and PCC (all FWE Pcorr<0.05). Short-term administration of SSRIs changes gray matter structures, consistent with previous work reporting enhancement of neuroplasticity by serotonergic neurotransmission. Furthermore, increased gray matter in the PCC is associated with increased functional connectivity in one of the brain's metabolically most active regions. Our novel findings provide convergent evidence for dynamic alterations of brain structure and function associated with SSRI pharmacotherapy. •Multimodal assessment using structural and functional pharmacological MRI•Gray matter increases in posterior cingulate cortex after SSRI intake•Structural findings are associated with resting state network changes.•Pharmacological MRI reveals network restructuration effects of SSRIs.
Imaging the neuroplastic effects of ketamine with VBM and the necessity of placebo control
In the last years a plethora of studies have investigated morphological changes induced by behavioural or pharmacological interventions using structural T1-weighted MRI and voxel-based morphometry (VBM). Ketamine is thought to exert its antidepressant action by restoring neuroplasticity. In order to test for acute impact of a single ketamine infusion on grey matter volume we performed a placebo-controlled, double-blind investigation in healthy volunteers using VBM. 28 healthy individuals underwent two MRI sessions within a timeframe of 2 weeks, each consisting of two structural T1-weighted MRIs within a single session, one before and one 45min after infusion of S-ketamine (bolus of 0.11mg/kg, followed by an maintenance infusion of 0.12mg/kg) or placebo (0.9% NaCl infusion) using a crossover design. In the repeated-measures ANOVA with time (post-infusion/pre-infusion) and medication (placebo/ketamine) as factors, no significant effect of interaction and no effect of medication was found (FWE-corrected). Importantly, further post-hoc t-tests revealed a strong “decrease” of grey matter both in the placebo and the ketamine condition over time. This effect was evident mainly in frontal and temporal regions bilaterally with t-values ranging from 4.95 to 5.31 (FWE-corrected at p<0.05 voxel level). The vulnerabilities of VBM have been repeatedly demonstrated, with reports of influence of blood flow, tissue water and direct effects of pharmacological compounds on the MRI signal. Here again, we highlight that the relationship between intervention and VBM results is apparently subject to a number of physiological influences, which are partly unknown. Future studies focusing on the effects of ketamine on grey matter should try to integrate known influential factors such as blood flow into analysis. Furthermore, the results of this study highlight the importance of a carefully performed placebo condition in pharmacological fMRI studies. •The study aimed to evaluate the effects of ketamine on brain structure using VBM.•No effects of ketamine using a double-blind, placebo-controlled, cross-over design.•Drug-unspecific strong “decrease” of grey matter over time.•VBM results are influenced by a parameters independent of “real” changes of brain structure.•Study highlights the importance of placebo condition in pharmacological MRI studies.