PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-6 (6)
 

Clipboard (0)
None
Journals
Year of Publication
Document Types
1.  Gray matter volume is associated with rate of subsequent skill learning after a long term training intervention 
Neuroimage  2014;96(100):158-166.
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 6 weeks, 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 4 weeks 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.
Highlights
•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.
doi:10.1016/j.neuroimage.2014.03.056
PMCID: PMC4075341  PMID: 24680712
Structural plasticity; Skill learning; MRI
2.  Polarity-specific effects of motor transcranial direct current stimulation on fMRI resting state networks☆ 
Neuroimage  2014;88(100):155-161.
Transcranial direct current stimulation (tDCS) has been used to modify motor performance in healthy and patient populations. However, our understanding of the large-scale neuroplastic changes that support such behavioural effects is limited. Here, we used both seed-based and independent component analyses (ICA) approaches to probe tDCS-induced modifications in resting state activity with the aim of establishing the effects of tDCS applied to the primary motor cortex (M1) on both motor and non-motor networks within the brain. Subjects participated in three separate sessions, during which resting fMRI scans were acquired before and after 10 min of 1 mA anodal, cathodal, or sham tDCS. Cathodal tDCS increased the inter-hemispheric coherence of resting fMRI signal between the left and right supplementary motor area (SMA), and between the left and right hand areas of M1. A similar trend was documented for the premotor cortex (PMC). Increased functional connectivity following cathodal tDCS was apparent within the ICA-generated motor and default mode networks. Additionally, the overall strength of the default mode network was increased. Neither anodal nor sham tDCS produced significant changes in resting state connectivity. This work indicates that cathodal tDCS to M1 affects the motor network at rest. In addition, the effects of cathodal tDCS on the default mode network support the hypothesis that diminished top-down control may contribute to the impaired motor performance induced by cathodal tDCS.
Highlights
•Resting state BOLD fMRI data was acquired before and after tDCS applied to M1.•Cathodal tDCS increased inter-hemispheric correlations between the M1 hand areas.•Cathodal tDCS increased connectivity in ICA-generated motor and default networks.•Cathodal tDCS increased the overall strength of the default network.
doi:10.1016/j.neuroimage.2013.11.037
PMCID: PMC3991849  PMID: 24287440
Transcranial direct current stimulation; Resting state connectivity; Functional MRI; Independent component analysis; Motor; Default mode
3.  Predicting behavioural response to TDCS in chronic motor stroke☆ 
Neuroimage  2014;85(Pt 3):924-933.
Transcranial direct current stimulation (TDCS) of primary motor cortex (M1) can transiently improve paretic hand function in chronic stroke. However, responses are variable so there is incentive to try to improve efficacy and or to predict response in individual patients. Both excitatory (Anodal) stimulation of ipsilesional M1 and inhibitory (Cathodal) stimulation of contralesional M1 can speed simple reaction time. Here we tested whether combining these two effects simultaneously, by using a bilateral M1–M1 electrode montage, would improve efficacy. We tested the physiological efficacy of Bilateral, Anodal or Cathodal TDCS in changing motor evoked potentials (MEPs) in the healthy brain and their behavioural efficacy in changing reaction times with the paretic hand in chronic stroke. In addition, we aimed to identify clinical or neurochemical predictors of patients' behavioural response to TDCS. There were three main findings: 1) unlike Anodal and Cathodal TDCS, Bilateral M1–M1 TDCS (1 mA, 20 min) had no significant effect on MEPs in the healthy brain or on reaction time with the paretic hand in chronic stroke patients; 2) GABA levels in ipsilesional M1 predicted patients' behavioural gains from Anodal TDCS; and 3) although patients were in the chronic phase, time since stroke (and its combination with Fugl–Meyer score) was a positive predictor of behavioural gain from Cathodal TDCS. These findings indicate the superiority of Anodal or Cathodal over Bilateral TDCS in changing motor cortico-spinal excitability in the healthy brain and in speeding reaction time in chronic stroke. The identified clinical and neurochemical markers of behavioural response should help to inform the optimization of TDCS delivery and to predict patient outcome variability in future TDCS intervention studies in chronic motor stroke.
Highlights
•Ipsilesional M1 GABA levels predict motor gains from Anodal TDCS in chronic stroke.•Time since stroke and Fugl–Meyer score jointly predict response to Cathodal TDCS.•Bilateral motor cortex TDCS did not reliably change motor evoked potentials.•Bilateral motor cortex TDCS did not reliably change manual reaction time.
doi:10.1016/j.neuroimage.2013.05.096
PMCID: PMC3899017  PMID: 23727528
Motor stroke; Plasticity; TDCS; Brain stimulation; Magnetic resonance spectroscopy; GABA
4.  Diffusion imaging of whole, post-mortem human brains on a clinical MRI scanner 
Neuroimage  2011;57(1-4):167-181.
Diffusion imaging of post mortem brains has great potential both as a reference for brain specimens that undergo sectioning, and as a link between in vivo diffusion studies and “gold standard” histology/dissection. While there is a relatively mature literature on post mortem diffusion imaging of animals, human brains have proven more challenging due to their incompatibility with high-performance scanners. This study presents a method for post mortem diffusion imaging of whole, human brains using a clinical 3-Tesla scanner with a 3D segmented EPI spin-echo sequence. Results in eleven brains at 0.94 × 0.94 × 0.94 mm resolution are presented, and in a single brain at 0.73 × 0.73 × 0.73 mm resolution. Region-of-interest analysis of diffusion tensor parameters indicate that these properties are altered compared to in vivo (reduced diffusivity and anisotropy), with significant dependence on post mortem interval (time from death to fixation). Despite these alterations, diffusion tractography of several major tracts is successfully demonstrated at both resolutions. We also report novel findings of cortical anisotropy and partial volume effects.
Research highlights
► Acquisition and processing protocols for diffusion MRI of post-mortem human brains. ► Effect of post-mortem and scan intervals on diffusion indices. ► Tractography in post-mortem human brains. ► Radial diffusion anisotropy in cortical gray matter.
doi:10.1016/j.neuroimage.2011.03.070
PMCID: PMC3115068  PMID: 21473920
Diffusion tensor imaging; Tractography; Post mortem; Human; Brain
5.  Age-related changes in grey and white matter structure throughout adulthood 
Neuroimage  2010;51(3-2):943-951.
Normal ageing is associated with gradual brain atrophy. Determining spatial and temporal patterns of change can help shed light on underlying mechanisms. Neuroimaging provides various measures of brain structure that can be used to assess such age-related change but studies to date have typically considered single imaging measures. Although there is consensus on the notion that brain structure deteriorates with age, evidence on the precise time course and spatial distribution of changes is mixed. We assessed grey matter (GM) and white matter (WM) structure in a group of 66 adults aged between 23 and 81. Multimodal imaging measures included voxel-based morphometry (VBM)-style analysis of GM and WM volume and diffusion tensor imaging (DTI) metrics of WM microstructure. We found widespread reductions in GM volume from middle age onwards but earlier reductions in GM were detected in frontal cortex. Widespread age-related deterioration in WM microstructure was detected from young adulthood onwards. WM decline was detected earlier and more sensitively using DTI-based measures of microstructure than using markers of WM volume derived from conventional T1-weighted imaging.
doi:10.1016/j.neuroimage.2010.03.004
PMCID: PMC2896477  PMID: 20211265
6.  Topography of connections between human prefrontal cortex and mediodorsal thalamus studied with diffusion tractography 
Neuroimage  2010;51(2):555-564.
Studies in monkeys show clear anatomical and functional distinctions among networks connecting with subregions within the prefrontal cortex. Three such networks are centered on lateral orbitofrontal cortex, medial frontal and cingulate cortex, and lateral prefrontal cortex and all have been identified with distinct cognitive roles. Although these areas differ in a number of their cortical connections, some of the first anatomical evidence for these networks came from tracer studies demonstrating their distinct patterns of connectivity with the mediodorsal (MD) nucleus of the thalamus. Here, we present evidence for a similar topography of MD thalamus prefrontal connections, using non-invasive imaging and diffusion tractography (DWI–DT) in human and macaque. DWI–DT suggested that there was a high probability of interconnection between medial MD and lateral orbitofrontal cortex, between caudodorsal MD and medial frontal/cingulate cortex, and between lateral MD and lateral prefrontal cortex, in both species. Within the lateral prefrontal cortex a dorsolateral region (the principal sulcus in the macaque and middle frontal gyrus in the human) was found to have a high probability of interconnection with the MD region between the regions with a high probability of interconnection with other parts of the lateral prefrontal cortex and with the lateral orbitofrontal cortex. In addition to suggesting that the thalamic connectivity in the macaque is a good guide to human prefrontal cortex, and therefore that there are likely to be similarities in the cognitive roles played by the prefrontal areas in both species, the present results are also the first to provide insight into the topography of projections of an individual thalamic nucleus in the human brain.
doi:10.1016/j.neuroimage.2010.02.062
PMCID: PMC2877805  PMID: 20206702
Anatomy; DTI; Human; Macaque; Thalamus

Results 1-6 (6)