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1.  Local GABA concentration is related to network-level resting functional connectivity 
eLife  2014;3:e01465.
Anatomically plausible networks of functionally inter-connected regions have been reliably demonstrated at rest, although the neurochemical basis of these ‘resting state networks’ is not well understood. In this study, we combined magnetic resonance spectroscopy (MRS) and resting state fMRI and demonstrated an inverse relationship between levels of the inhibitory neurotransmitter GABA within the primary motor cortex (M1) and the strength of functional connectivity across the resting motor network. This relationship was both neurochemically and anatomically specific. We then went on to show that anodal transcranial direct current stimulation (tDCS), an intervention previously shown to decrease GABA levels within M1, increased resting motor network connectivity. We therefore suggest that network-level functional connectivity within the motor system is related to the degree of inhibition in M1, a major node within the motor network, a finding in line with converging evidence from both simulation and empirical studies.
DOI: http://dx.doi.org/10.7554/eLife.01465.001
eLife digest
Even when your body is at rest, your brain remains active. Subjects lying in brain scanners without any specific task to perform show coordinated and reproducible patterns of brain activity. Areas of the brain with similar functions, such as those involved in vision or in movement, tend to increase or decrease their activity in sync, and these coordinated patterns are referred to as resting state networks.
The functions of these networks are unclear—they may support introspection, memory recall or planning for the future, or they may help to strengthen newly acquired skills by enabling the brain to replay previous learning episodes. There is evidence that resting state networks are altered in disorders such as Alzheimer’s disease, autism and schizophrenia, but little is known about how these changes arise or what they might mean.
Now, Stagg et al. have used a type of brain scan called magnetic resonance spectroscopy to gain insights into the mechanisms by which one particular network—the resting motor network—is generated. This network consists of areas involved in planning, monitoring and executing movements, and includes the primary motor cortex, which initiates movements by sending instructions to the spinal cord.
The levels of a chemical called GABA—a neurotransmitter molecule that tends to inhibit the activity of nerve cells—were measured in the primary motor cortex of young healthy volunteers as they lay idle in a scanner. GABA levels were negatively correlated with the amount of coordinated activity within the resting motor network. By contrast, no relation was seen between coordinated activity and the levels of the neurotransmitter glutamate, which tends to increase the activity of nerve cells. Furthermore, when a weak electric current was applied through the subjects’ scalp to their primary motor cortex—a technique previously shown to lower levels of GABA in the region—the resting motor network became stronger.
In addition to providing new information on how the rhythmic patterns of activity seen in the resting brain arise, the work of Stagg et al. contributes to the more general effort to understand the complex patterns of connections within the human brain.
DOI: http://dx.doi.org/10.7554/eLife.01465.002
doi:10.7554/eLife.01465
PMCID: PMC3964822  PMID: 24668166
magnetic resonance spectroscopy; GABA; resting state fMRI; human
2.  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
3.  Visualization of altered neurovascular coupling in chronic stroke patients using multimodal functional MRI 
Evaluation of cortical reorganization in chronic stroke patients requires methods to accurately localize regions of neuronal activity. Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is frequently employed; however, BOLD contrast depends on specific coupling relationships between the cerebral metabolic rate of oxygen (CMRO2), cerebral blood flow (CBF), and volume (CBV), which may not exist following stroke. The aim of this study was to understand whether CBF-weighted (CBFw) and CBV-weighted (CBVw) fMRI could be used in sequence with BOLD to characterize neurovascular coupling mechanisms poststroke. Chronic stroke patients (n=11) with motor impairment and age-matched controls (n=11) performed four sets of unilateral motor tasks (60 seconds/30 seconds off/on) during CBFw, CBVw, and BOLD fMRI acquisition. While control participants elicited mean BOLD, CBFw, and CBVw responses in motor cortex (P<0.01), patients showed only mean changes in CBF (P<0.01) and CBV (P<0.01), but absent mean BOLD responses (P=0.20). BOLD intersubject variability was consistent with differing coupling indices between CBF, CBV, and CMRO2. Thus, CBFw and/or CBVw fMRI may provide crucial information not apparent from BOLD in these patients. A table is provided outlining distinct vascular and metabolic uncoupling possibilities that elicit different BOLD responses, and the strengths and limitations of the multimodal protocol are summarized.
doi:10.1038/jcbfm.2012.105
PMCID: PMC3493993  PMID: 22828998
arterial spin labeling; BOLD; cerebral blood flow; cerebral blood volume; cerebrovascular disease; neurovascular coupling
4.  Opioid dependence 
Clinical Evidence  2011;2011:1015.
Introduction
Dependence on opioids is a multifactorial condition involving genetic and psychosocial factors. There are three stages to treating opioid dependence. Stabilisation is usually by opioid substitution treatments, and aims to ensure that the drug use becomes independent of mental state (such as craving and mood) and independent of circumstances (such as finance and physical location). The next stage is to withdraw (detox) from opioids. The final stage is relapse prevention. This treatment process contributes to recovery of the individual, which also includes improved overall health and wellbeing, as well as engagement in society.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of drug treatments for stabilisation (maintenance) in people with opioid dependence? What are the effects of drug treatments for withdrawal in people with opioid dependence? What are the effects of drug treatments for relapse prevention in people with opioid dependence? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2011 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 26 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review, we present information relating to the effectiveness and safety of the following interventions: buprenorphine; clonidine; lofexidine; methadone; naltrexone; and ultra-rapid withdrawal regimens.
Key Points
Dependence on opioids is a multifactorial condition involving genetic and psychosocial factors.
There are three stages to treating opioid dependence. Stabilisation is usually by opioid substitution treatments, and aims to ensure that the drug use becomes independent of mental state (such as craving and mood) and independent of circumstances (such as finance and physical location).The next stage is to withdraw (detox) from opioids.The final stage is relapse prevention.
Methadone and buprenorphine help to stabilise opioid use, as they decrease heroin use and help to retain people in treatment programmes. Methadone and buprenorphine seem equally effective at stabilising opioid use.
Methadone, buprenorphine, and alpha2-adrenoceptor agonists (lofexidine, clonidine) can all help people to withdraw from dependence on illicit opioids. Lofexidine and clonidine may be less effective than methadone and buprenorphine in withdrawal, although evidence is weak. Ultra-rapid withdrawal can help in detoxification, although there are important safety risks in keeping people heavily sedated or under general anaesthesia for a day, or under general anaesthesia for a few hours, and outcomes are no better.
Naltrexone can help to prevent relapse of heroin use if combined with psychosocial treatment.
PMCID: PMC3275107  PMID: 21929827
5.  Left-Deviating Prism Adaptation in Left Neglect Patient: Reflexions on a Negative Result 
Neural Plasticity  2012;2012:718604.
Adaptation to right-deviating prisms is a promising intervention for the rehabilitation of patients with left spatial neglect. In order to test the lateral specificity of prism adaptation on left neglect, the present study evaluated the effect of left-deviating prism on straight-ahead pointing movements and on several classical neuropsychological tests in a group of five right brain-damaged patients with left spatial neglect. A group of healthy subjects was also included for comparison purposes. After a single session of exposing simple manual pointing to left-deviating prisms, contrary to healthy controls, none of the patients showed a reliable change of the straight-ahead pointing movement in the dark. No significant modification of attentional paper-and-pencil tasks was either observed immediately or 2 hours after prism adaptation. These results suggest that the therapeutic effect of prism adaptation on left spatial neglect relies on a specific lateralized mechanism. Evidence for a directional effect for prism adaptation both in terms of the side of the visuomanual adaptation and therefore possibly in terms of the side of brain affected by the stimulation is discussed.
doi:10.1155/2012/718604
PMCID: PMC3463195  PMID: 23050168
6.  Cortical activation changes underlying stimulation-induced behavioural gains in chronic stroke 
Brain  2011;135(1):276-284.
Transcranial direct current stimulation, a form of non-invasive brain stimulation, is showing increasing promise as an adjunct therapy in rehabilitation following stroke. However, although significant behavioural improvements have been reported in proof-of-principle studies, the underlying mechanisms are poorly understood. The rationale for transcranial direct current stimulation as therapy for stroke is that therapeutic stimulation paradigms increase activity in ipsilesional motor cortical areas, but this has not previously been directly tested for conventional electrode placements. This study was performed to test directly whether increases in ipsilesional cortical activation with transcranial direct current stimulation are associated with behavioural improvements in chronic stroke patients. Patients at least 6 months post-first stroke participated in a behavioural experiment (n = 13) or a functional magnetic resonance imaging experiment (n = 11), each investigating the effects of three stimulation conditions in separate sessions: anodal stimulation to the ipsilesional hemisphere; cathodal stimulation to the contralesional hemisphere; and sham stimulation. Anodal (facilitatory) stimulation to the ipsilesional hemisphere led to significant improvements (5–10%) in response times with the affected hand in both experiments. This improvement was associated with an increase in movement-related cortical activity in the stimulated primary motor cortex and functionally interconnected regions. Cathodal (inhibitory) stimulation to the contralesional hemisphere led to a functional improvement only when compared with sham stimulation. We show for the first time that the significant behavioural improvements produced by anodal stimulation to the ipsilesional hemisphere are associated with a functionally relevant increase in activity within the ipsilesional primary motor cortex in patients with a wide range of disabilities following stroke.
doi:10.1093/brain/awr313
PMCID: PMC3267983  PMID: 22155982
transcranial direct current stimulation; stroke rehabilitation; motor system
7.  Opioid dependence 
Clinical Evidence  2009;2009:1015.
Introduction
Dependence on opioids is a multifactorial condition involving genetic and psychosocial factors. There are three approaches to treating opioid dependence. Stabilisation is usually by opioid substitution treatments, and aims to ensure that the drug use becomes independent of mental state (such as craving and mood) and independent of circumstances (such as finance and physical location). The next stage is to withdraw (detox) from opioids. The final aim is relapse prevention.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of drug treatments for stabilisation (maintenance) in people with opioid dependence? What are the effects of drug treatments for withdrawal in people with opioid dependence? What are the effects of drug treatments for relapse prevention in people with opioid dependence? We searched: Medline, Embase, The Cochrane Library, and other important databases up to May 2008 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 23 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review, we present information relating to the effectiveness and safety of the following interventions: buprenorphine; clonidine; lofexidine; methadone; naltrexone; and ultra-rapid withdrawal regimes.
Key Points
Dependence on opioids is a multifactorial condition involving genetic and psychosocial factors.
There are three approaches to treating opioid dependence. Stabilisation is usually by opioid substitution treatments, and aims to ensure that the drug use becomes independent of mental state (such as craving and mood) and independent of circumstances (such as finance and physical location).The next stage is to withdraw (detox) from opioids.The final aim is relapse prevention.
Methadone and buprenorphine help to stabilise opioid use, as they decrease heroin use and help retain people in treatment programmes. Methadone and buprenorphine seem equally effective at stabilising opioid use.
Methadone, buprenorphine, and alpha2-adrenoceptor agonists (lofexidine, clonidine) can all help people withdraw from dependence on illicit opioids. Lofexidine and clonidine may be less effective than methadone and buprenorphine in withdrawal, although evidence is weak. Ultra-rapid withdrawal can help in detoxification, although there are important safety risks in keeping people heavily sedated or under general anaesthesia for a day, and outcomes are no better.
Naltrexone can help prevent relapse of heroin use if combined with psychosocial treatment.
PMCID: PMC2907824  PMID: 21696648

Results 1-7 (7)