Effective Connectivity of Cortical Sensorimotor Networks During Finger Movement Tasks: A Simultaneous fNIRS,fMRI, EEG Study

Recently, interest has been growing to understand the underlying dynamic directional relationship between simultaneously activated regions of the brain during motor task performance. Such directionality analysis (or effective connectivity analysis), based on non-invasive electrophysiological (electroencephalography—EEG) and hemodynamic (functional near infrared spectroscopy—fNIRS; and functional magnetic resonance imaging—fMRI) neuroimaging modalities can provide an estimate of the motor task-related information flow from one brain region to another. Since EEG, fNIRS and fMRI modalities achieve different spatial and temporal resolutions of motor-task related activation in the brain, the aim of this study was to determine the effective connectivity of cortico-cortical sensorimotor networks during finger movement tasks measured by each neuroimaging modality. Nine healthy subjects performed right hand finger movement tasks of different complexity (simple finger tapping-FT, simple finger sequence-SFS, and complex finger sequence-CFS). We focused our observations on three cortical regions of interest (ROIs), namely the contralateral sensorimotor cortex (SMC), the contralateral premotor cortex (PMC) and the contralateral dorsolateral prefrontal cortex (DLPFC). We estimated the effective connectivity between these ROIs using conditional Granger causality (GC) analysis determined from the time series signals measured by fMRI (blood oxygenation level-dependent-BOLD), fNIRS (oxygenated-O₂Hb and deoxygenated-HHb hemoglobin), and EEG (scalp and source level analysis) neuroimaging modalities. The effective connectivity analysis showed significant bi-directional information flow between the SMC, PMC, and DLPFC as determined by the EEG (scalp and source), fMRI (BOLD) and fNIRS (O₂Hb and HHb) modalities for all three motor tasks. However the source level EEG GC values were significantly greater than the other modalities. In addition, only the source level EEG showed a significantly greater forward than backward information flow between the ROIs. This simultaneous fMRI, fNIRS and EEG study has shown through independent GC analysis of the respective time series that a bi-directional effective connectivity occurs within a cortico-cortical sensorimotor network (SMC, PMC and DLPFC) during finger movement tasks.     

Synthesis of berberine-piperazine conjugates as potential antioxidant and cytotoxic agents

Piperazine derivatives bearing different electron-withdrawing and electron-donating functional groups were linked to the well-known isoquinoline alkaloid derivative, berberine via efficient organic transformations. The entire target berberine-based analogues were examined for their in vitro antioxidant potency using 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid bioassays, and anticancer activities using sulforhodamine B assay against HeLa and CaSki cervical cancer cell lines in addition to the cytotoxicity using Madin-Darby canine kidney non-cancer cell lines and, ascorbic acid and berberine used as a control for antioxidant and anticancer activities, respectively. Bioassay results revealed that newer compounds were more active against CaSki and HeLa cell lines with therapeutic indices better than that of parent berberine and showed tolerable cytotoxicity to the normal cells. A final analogue 5a with 4-methylpiperazine substituent indicated most significant anticancer potency with a therapeutic index of 58.53 (HeLa) and 48.76 (CaSki), followed by those bearing meta-chloropiperazine rings with a therapeutic index of 41.83 (HeLa) and 47.35 (CaSki), respectively.In addition, newly synthesized analogues exerted a significant radical scavenging activity against 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid cation with IC₅₀ values of 8.917?µg/mL, and were good to moderate scavengers of 2,2-diphenyl-1-picrylhydrazyl radical with IC₅₀ values of 25.40?µg/mL. Synthesized compound was characterized using several techniques, fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, ¹³C nuclear magnetic resonance, mass spectroscopy and elemental (CHN) analyses.     

Effect of high‐frequency subthalamic neurostimulation on gait and freezing of gait in Parkinson's disease: a systematic review and meta‐analysis

The aim of this meta‐analysis was to summarize the short‐ and long‐term effects of bilateral deep brain stimulation of the subthalamic nucleus (STN‐DBS) on gait and freezing of gait (FOG) in Parkinson's disease and to detect predictors of post‐stimulation outcome. A comprehensive review of the literature was conducted up to October 2015 using Medline Ovid databases for studies analyzing the effect of bilateral STN‐DBS on FOG and/or gait. Sixteen studies with available data for the gait item (no. 29) of the Unified Parkinson's Disease Rating Scale (UPDRS) and six studies with the FOG item (no. 14) were included. Data were summarized for the following follow‐up periods: 6–15, 24–48 and >48 months. For the medication (Med)‐Off/stimulation(Stim)‐On condition compared with baseline Med‐Off, STN‐DBS significantly improved gait on average from 2.43 to 0.96, 2.53 to 1.31 and 2.56 to 1.40 points at 6–15, 24–48 and >48 months, respectively (P < 0.05). Pre‐operative levodopa responsiveness of UPDRS‐III and Med‐Off severity of gait were the predictors of this beneficial effect. STN‐DBS significantly improved FOG for the Med‐Off/Stim‐On condition compared with baseline on average from 2.26 to 0.82, 2.43 to 1.13 and 2.48 to 1.38 points at 6–15, 24–48 and >48 months, respectively (P < 0.05). There was no significant effect in the Med‐On/Stim‐On condition. This meta‐analysis showed a robust improvement of gait and FOG by STN‐DBS for more than 4 years in the Med‐Off/Stim‐On condition. No beneficial effect was found for the On state of medication. Pre‐operative levodopa responsiveness of global motor performance (UPDRS‐III) is the strongest predictor of the effect of deep brain stimulation on gait.     

Ameliorative effects of Ocimum sanctum in sciatic nerve transection-induced neuropathy in rats

Objectives

The present study was aimed at investigating the ameliorative effect of Ocimum sanctum in sciatic nerve transection (axotomy)-induced peripheral neuropathy in rats.

Materials and methods

Sciatic nerve transection-induced axonal degeneration was assessed histopathologically. Paw pressure, Von Frey Hair, tail cold-hyperalgesia, motor in-coordination tests were performed to assess the extent of neuropathy. Biochemical estimations of thiobarbituric acid reactive species (TBARS), reduced glutathione (GSH), and total calcium levels were also performed. Methanolic extract of Ocimum sanctum at different doses (50, 100 and 200 mg/kg p.o.) was administered for 10 consecutive days starting from the day of surgery.

Results

Administration of Ocimum sanctum attenuated sciatic nerve transection-induced axonal degeneration, reduction of nociceptive threshold and motor in-coordination. Moreover, it also attenuated axotomy-induced rise in TBARS, total calcium and decrease in GSH levels in a dose-dependent manner.

Conclusion

Anti-oxidant and calcium attenuating actions may be responsible for observed ameliorative effects of Ocimum sanctum in axotomy-induced neuropathy.     

Metabolic and amyloid PET network reorganization in Alzheimer’s disease: differential patterns and partial volume effects

Brain Imaging and Behavior - Alzheimer’s disease (AD) is a neurodegenerative disorder, considered a disconnection syndrome with regional molecular pattern abnormalities quantifiable by the...     

Cortical involvement in the generation of essential tremor

Conflicting results on the existence of tremor-related cortical activity in essential tremor (ET) have raised questions on the role of the cortex in tremor generation. Here we attempt to address these issues. We recorded 64 channel surface EEGs and EMGs from forearm muscles in 15 patients with definite ET. EEG and EMG power spectra, relative power of the rhythmic EMG activity, relative EEG power at the tremor frequency, and EEG-EMG and EEG-EEG coherence were calculated and their dynamics over time explored. Corticomuscular delay was studied using a new method for narrow-band coherent signals. Corticomuscular coherence in the contralateral central region at the tremor frequency was present in all patients in recordings with a relative tremor EMG power exceeding a certain level. However, the coherence was lost intermittently even with tremors far above this level. Physiological 15- to 30-Hz coherence was found consistently in 11 patients with significantly weaker EMG activity in this frequency range. A more frontal (mesial) hot spot was also intermittently coupled with the tremor and the central hot spot in five patients. Corticomuscular delays were compatible with transmission in fast corticospinal pathways and feedback of the tremor signal. Thus the tremor rhythm is intermittently relayed only in different cortical motor areas. We hypothesize that tremor oscillations build up in different subcortical and subcortico-cortical circuits only temporarily entraining each other.