RESUMEN
The purpose of this study was to develop and evaluate a new, open-source MR-compatible device capable of assessing unipedal and bipedal lower extremity movement with minimal head motion and high test-retest reliability. To evaluate the prototype, 20 healthy adults participated in two magnetic resonance imaging (MRI) visits, separated by 2-6 months, in which they performed a visually guided dorsiflexion/plantar flexion task with their left foot, right foot, and alternating feet. Dependent measures included: evoked blood oxygen level-dependent (BOLD) signal in the motor network, head movement associated with dorsiflexion/plantar flexion, the test-retest reliability of these measurements. Left and right unipedal movement led to a significant increase in BOLD signal compared to rest in the medial portion of the right and left primary motor cortex (respectively), and the ipsilateral cerebellum (FWE corrected, p < .001). Average head motion was 0.10 ± 0.02 mm. The test-retest reliability was high for the functional MRI data (intraclass correlation coefficients [ICCs]: >0.75) and the angular displacement of the ankle joint (ICC: 0.842). This bipedal device can robustly isolate activity in the motor network during alternating plantarflexion and dorsiflexion with minimal head movement, while providing high test-retest reliability. Ultimately, these data and open-source building instructions will provide a new, economical tool for investigators interested in evaluating brain function resulting from lower extremity movement.
Asunto(s)
Cerebelo/fisiología , Técnicas de Diagnóstico Neurológico/instrumentación , Diseño de Equipo/normas , Neuroimagen Funcional , Movimientos de la Cabeza/fisiología , Extremidad Inferior/fisiología , Actividad Motora/fisiología , Corteza Motora/fisiología , Red Nerviosa/fisiología , Desempeño Psicomotor/fisiología , Adulto , Cerebelo/diagnóstico por imagen , Femenino , Neuroimagen Funcional/normas , Humanos , Imagen por Resonancia Magnética , Masculino , Corteza Motora/diagnóstico por imagen , Red Nerviosa/diagnóstico por imagen , Reproducibilidad de los Resultados , Adulto JovenRESUMEN
BACKGROUND: Poorly controlled chronic pain can lead to non-prescription use of opiates, which is a growing crisis in our communities. Transcranial magnetic stimulation (TMS) is a non-invasive therapeutic tool which has emerged as a potential treatment option for these patients. It is still unclear, however, if the dorsolateral prefrontal cortex (DLPFC) or the motor cortex (MC) is a more effective treatment location. The purpose of this study was to directly compare the effects of DLPFC versus MC TMS on pain severity and the urge to use opiates among chronic pain patients. METHODS: Twenty-two individuals with chronic pain currently using prescription opiates were randomized to receive 10, 3000 pulse sessions of 10 Hz repetitive TMS (rTMS) to the left DLPFC (110% resting motor threshold) or left MC (90% resting motor threshold). Multivariate linear models were used to evaluate the effect of TMS on pain and opiate use, including items from the Brief Pain Inventory (BPI) as well as subjective ratings of pain, distress, and the urge for opiates. RESULTS: Twenty participants (91%) completed all 10 treatment sessions and follow up visits. There was a main effect of stimulation site (F7,210 = 3.742, p = 0.001), wherein MC stimulation decreased pain interference significantly more than DLPFC stimulation (F1,216 = 8.447, p = 0.004). While both sites had comparable effect sizes on stress, pain, and discomfort, MC stimulation had larger effects on pain interference (Cohen's d: 0.7) and urge to use opiates (Cohen's d: 0.5) than DLPFC stimulation. CONCLUSION: These data suggest that the MC may be a promising target for decreasing opiate dependence and pain interference among chronic pain patients.
Asunto(s)
Dolor Crónico/terapia , Trastornos Relacionados con Opioides/terapia , Estimulación Magnética Transcraneal , Adulto , Analgésicos Opioides , Dolor Crónico/etiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Corteza Motora , Alcaloides Opiáceos , Dimensión del Dolor , Corteza Prefrontal/fisiología , Descanso , Resultado del TratamientoRESUMEN
Theta-burst stimulation (TBS) is a form of non-invasive neuromodulation which is delivered in an intermittent (iTBS) or continuous (cTBS) manner. Although 600 pulses is the most common dose, the goal of these experiments was to evaluate the effect of higher per-dose pulse numbers on cortical excitability. Sixty individuals were recruited for 2 experiments. In Experiment 1, participants received 600, 1200, 1800, or sham (600) iTBS (4 visits, counterbalanced, left motor cortex, 80% active threshold). In Experiment 2, participants received 600, 1200, 1800, 3600, or sham (600) cTBS (5 visits, counterbalanced). Motor evoked potentials (MEP) were measured in 10-min increments for 60 min. For iTBS, there was a significant interaction between dose and time (F = 3.8296, p = 0.01), driven by iTBS (1200) which decreased excitability for up to 50 min (t = 3.1267, p = 0.001). For cTBS, there was no overall interaction between dose and time (F = 1.1513, p = 0.33). Relative to sham, cTBS (3600) increased excitability for up to 60 min (t = 2.0880, p = 0.04). There were no other significant effects of dose relative to sham in either experiment. Secondary analyses revealed high within and between subject variability. These results suggest that iTBS (1200) and cTBS (3600) are, respectively, the most effective doses for decreasing and increasing cortical excitability.
Asunto(s)
Excitabilidad Cortical , Ritmo Teta/fisiología , Adulto , Electromiografía , Potenciales Evocados Motores/fisiología , Femenino , Humanos , Masculino , Estimulación Magnética Transcraneal/métodos , Adulto JovenRESUMEN
Optogenetically evoked local field potential (LFP) recorded from the medial prefrontal cortex (mPFC) of mice during basal conditions and following a systemic cocaine administration were analyzed. Blue light stimuli were delivered to mPFC through a fiber optic every 2 s and each trial was repeated 100 times. As in the previous study, we used a surrogate data method to check that nonlinearity was present in the experimental LFPs and only used the last 1.5 s of steady activity to measure the LFPs phase resetting induced by the brief 10 ms light stimulus. We found that the steady dynamics of the mPFC in response to light stimuli could be reconstructed in a three-dimensional phase space with topologically similar "8"-shaped attractors across different animals. Therefore, cocaine did not change the complexity of the recorded nonlinear data compared to the control case. The phase space of the reconstructed attractor is determined by the LFP time series and its temporally shifted versions by a multiple of some lag time. We also compared the change in the attractor shape between cocaine-injected and control using (1) dendrogram clustering and (2) Frechet distance. We found about 20% overlap between control and cocaine trials when classified using dendrogram method, which suggest that it may be possible to describe mathematically both data sets with the same model and slightly different model parameters. We also found that the lag times are about three times shorter for cocaine trials compared to control. As a result, although the phase space trajectories for control and cocaine may look similar, their dynamics is significantly different.