The European journal of neuroscience
-
Randomized Controlled Trial
Venlafaxine and oxycodone effects on human spinal and supraspinal pain processing: a randomized cross-over trial.
Severe pain is often treated with opioids. Antidepressants that inhibit serotonin and norepinephrine reuptake (SNRI) have also shown a pain relieving effect, but for both SNRI and opioids, the specific mode of action in humans remains vague. This study investigated how oxycodone and venlafaxine affect spinal and supraspinal pain processing. ⋯ Venlafaxine exerts its effects on the modulation of spinal nociceptive transmission, which may reflect changes in balance between descending inhibition and descending facilitation. Oxycodone, on the other hand, exerts its effects at the cortical level. This study sheds light on how opioids and SNRI drugs modify the human central nervous system and where their effects dominate.
-
Randomized Controlled Trial
Systematic assessment of duration and intensity of anodal transcranial direct current stimulation on primary motor cortex excitability.
Since the initial demonstration of linear effects of stimulation duration and intensity on the strength of after-effects associated with transcranial direct current stimulation (tDCS), few studies have systematically assessed how varying these parameters modulates corticospinal excitability. Therefore, the objective of this study was to systematically evaluate the effects of anodal tDCS on corticospinal excitability at two stimulation intensities (1 mA, 2 mA) and durations (10 min, 20 min), and determine the value of several variables in predicting response. Two groups of 20 individuals received, in two separate sessions, 1 and 2 mA anodal tDCS (left primary motor cortex (M1)-right supra-orbital montage) for either 10- or 20-min. ⋯ In conclusion, the present findings are consistent with recent reports showing high levels of inter-subject variability in the neurophysiological response to tDCS, which may partly explain inconsistent group results. Furthermore, the level of variability in the neurophysiological outcome measure, i.e. MEPs, appears to be related to response.
-
Randomized Controlled Trial
Differential effects of cathodal transcranial direct current stimulation of prefrontal, motor and somatosensory cortices on cortical excitability and pain perception - a double-blind randomised sham-controlled study.
The primary aim of this study was to assess the effects of cathodal transcranial direct current stimulation (c-tDCS) over cortical regions of the pain neuromatrix, including the primary motor (M1), sensory (S1) and dorsolateral prefrontal (DLPFC) cortices on M1/S1 excitability, sensory (STh), and pain thresholds (PTh) in healthy adults. The secondary aim was to evaluate the placebo effects of c-tDCS on induced cortical and behavioural changes. Before, immediately after and 30 min after c-tDCS the amplitude of N20-P25 components of somatosensory evoked potentials (SEPs) and peak-to-peak amplitudes of motor evoked potentials (MEPs) were measured under four different experimental conditions. ⋯ Compared with baseline values, significant STh and PTh increases were observed after c-tDCS of these three sites. Decreasing the level of S1 and M1 excitability, following S1, M1 and DLPFC stimulation, confirmed the functional connectivities between these cortical sites involved in pain processing. Furthermore, increasing the level of STh/PTh after c-tDCS of these sites indicated that stimulation of not only M1 but also S1 and DLPFC could be considered a technique to decrease the level of pain in patients.
-
Randomized Controlled Trial
Anxiety-provoked gait changes are selectively dopa-responsive in Parkinson's disease.
In order to understand how dopamine modulates the effect of anxiety on gait, the goal of this study was to use virtual reality to provoke anxiety in Parkinson's disease (PD) (in both ON and OFF states) and quantify its effect on gait. Seventeen participants with PD and 20 healthy age-matched controls were instructed to walk in a virtual environment in two anxiety-provoking conditions: (i) across a plank that was located on the GROUND and (ii) across an ELEVATED plank. All participants with PD completed this experiment in both the ON and OFF states, and were then striated into groups based on baseline trait anxiety scores for further analyses. ⋯ OFF comparison). In conclusion, only highly trait anxious participants with PD benefitted from dopaminergic treatment, specifically when walking in the anxiety-provoking environment. Improvements to gait during anxious walking might be a result of dopaminergic medication acting in two ways: (i) improving the basal ganglia's capacity to process information and (ii) reducing the load from anxiety and subsequently making more resources available to effectively process other competing inputs.
-
Randomized Controlled Trial
One hertz repetitive transcranial magnetic stimulation over dorsal premotor cortex enhances offline motor memory consolidation for sequence-specific implicit learning.
Consolidation of motor memories associated with skilled practice can occur both online, concurrent with practice, and offline, after practice has ended. The current study investigated the role of dorsal premotor cortex (PMd) in early offline motor memory consolidation of implicit sequence-specific learning. Thirty-three participants were assigned to one of three groups of repetitive transcranial magnetic stimulation (rTMS) over left PMd (5 Hz, 1 Hz or control) immediately following practice of a novel continuous tracking task. ⋯ Enhanced sequence-specific learning with 1 Hz rTMS following practice was due to greater offline consolidation, not differences in online learning between the groups within practice days. A follow-up experiment revealed that stimulation of PMd following practice did not differentially change motor cortical excitability, suggesting that changes in offline consolidation can be largely attributed to stimulation-induced changes in PMd. These findings support a differential role for the PMd in support of online and offline sequence-specific learning of a visuomotor task and offer converging evidence for competing memory systems.