BACKGROUND: Dystonia is a movement disorder with patterned, directional, and often sustained muscle contractions that produce abnormal postures or repetitive movements. Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective and safe treatment for medically refractory dystonia. However, recent studies reported gait problems, gait freezing and falls in patients treated with DBS. Because these symptoms may point to deficient gait initiation processes, we systematically assessed the anticipatory postural adjustments (APAs) prior to stepping in dystonia patients with GPi-DBS. METHODS: Thirteen patients with focal/segmental dystonia under GPi-DBS and twelve healthy control subjects were included in the study. Data were collected using pressure sensitive sensors and APAs were studied by centre of pressure measures. We compared APAs of both groups and analysed the influence of GPi-DBS on APAs in patients. RESULTS: Medio-lateral and antero-posterior COP displacements, total COP path, maximal APA velocity and 1st step length were all smaller in patients for both ON (p=0.006, p=0.018, p=0.002, p=0.016, p=0.04) and OFF (p=0.001, p=0.01, p=0.001, p=0.03, p=0.024) condition compared to healthy subjects. GPi-DBS did not change APA parameters in patients. CONCLUSIONS: Observations that APAs are impaired in dystonia and are at the same time not affected by the stimulation current are compatible with the assumption that APAs and dystonic symptoms may rely on distinct networks, possibly within the same cortical and basal ganglia structures. With no effect of stimulation on APAs it is unlikely that this would be a mechanism of impaired balance in the patients after the surgery.
COBISS.SI-ID: 3250604
BACKGROUND: The speed-accuracy trade-off (SAT) refers to the balancing of speed versus accuracy during decision-making. SAT is very commonly investigated with perceptual decision-making tasks such as the moving dots task (MDT). The dorsolateral prefrontal cortex (DLPFC) and the pre-supplementary motor area (pre-SMA) are two brain regions considered to be involved in the control of SAT. OBJECTIVES/HYPOTHESES: The study tested whether the DLPFC and the pre-SMA play an essential role in the control of SAT. We hypothesized that continuous theta burst stimulation (cTBS) over the right DLPFC would primarily alter the rate of accumulation of evidence, whereas stimulation of the pre-SMA would influence the threshold for reaching a decision. METHODS: Fifteen (5 females; mean age = 30, SD =5.40) healthy volunteers participated in the study. We used two versions of the MDT and cTBS over the right DLPFC, pre-SMA and sham stimulation. The drift diffusion model was fit to the behavioural data (reaction time and error rate) in order to calculate the drift rate, boundary separation (threshold) and non-decision time. RESULTS: cTBS over the right DLPFC decreased the rate of accumulation of evidence (i.e. the drift rate from the diffusion model) in high (0.35 and 0.5) but not in low coherence trials. cTBS over the pre-SMA changed the boundary separation/threshold required to reach a decision on accuracy, but not on speed trials. CONCLUSIONS: The results suggest for the first time that both the DLPFC and the pre-SMA make essential but distinct contributions to the modulation of SAT.
COBISS.SI-ID: 2933932
PURPOSE: To evaluate the reproducibility of the expression of Parkinson's Disease Related Pattern (PDRP) across multiple sets of 18F-FDG-PET brain images reconstructed with different reconstruction algorithms. METHODS: 18F-FDG-PET brain imaging was performed in two independent cohorts of Parkinson's disease (PD) patients and normal controls (NC). Slovenian cohort (20 PD patients, 20 NC) was scanned with Siemens Biograph mCT camera and reconstructed using FBP, FBP+TOF, OSEM, OSEM+TOF, OSEM+PSF and OSEM+PSF+TOF. American Cohort (20 PD patients, 7 NC) was scanned with GE Advance camera and reconstructed using 3DRP, FORE-FBP and FORE-Iterative. Expressions of two previously-validated PDRP patterns (PDRP-Slovenia and PDRP-USA) were calculated. We compared the ability of PDRP to discriminate PD patients from NC, differences and correlation between the corresponding subject scores and ROC analysis results across the different reconstruction algorithms. RESULTS: The expression of PDRP-Slovenia and PDRP-USA networks was significantly elevated in PD patients compared to NC (p(0.0001), regardless of reconstruction algorithms. PDRP expression strongly correlated between all studied algorithms and the reference algorithm (r⩾0.993, p(0.0001). Average differences in the PDRP expression among different algorithms varied within 0.73 and 0.08 of the reference value for PDRP-Slovenia and PDRP-USA, respectively. ROC analysis confirmed high similarity in sensitivity, specificity and AUC among all studied reconstruction algorithms. CONCLUSIONS: These results show that the expression of PDRP is reproducible across a variety of reconstruction algorithms of 18F-FDG-PET brain images. PDRP is capable of providing a robust metabolic biomarker of PD for multicenter 18F-FDG-PET images acquired in the context of differential diagnosis or clinical trials.
COBISS.SI-ID: 3585452