Cognitive, Mood, and Electroencephalographic Effects of Noninvasive Cortical Stimulation With Weak Electrical Currents

Objectives: The use of noninvasive cortical electrical stimulation with weak currents has significantly increased in basic and clinical human studies. Initial, preliminary studies with this technique have shown encouraging results; however, the safety and tolerability of this method of brain stimulation have not been sufficiently explored yet. The purpose of our study was to assess the effects of direct current (DC) and alternating current (AC) stimulation at different intensities in order to measure their effects on cognition, mood, and electroencephalogram. Methods: Eighty-two healthy, right-handed subjects received active and sham stimulation in a randomized order. We conducted 164 ninety-minute sessions of electrical stimulation in 4 different protocols to assess safety of (1) anodal DC of the dorsolateral prefrontal cortex (DLPFC); (2) cathodal DC of the DLPFC; (3) intermittent anodal DC of the DLPFC and; (4) AC on the zygomatic process. We used weak currents of 1 to 2 mA (for DC experiments) or 0.1 to 0.2 mA (for AC experiment). Results: We found no significant changes in electroencephalogram, cognition, mood, and pain between groups and a low prevalence of mild adverse effects (0.11% and 0.08% in the active and sham stimulation groups, respectively), mainly, sleepiness and mild headache that were equally distributed between groups. Conclusions: Here, we show no neurophysiological or behavioral signs that transcranial DC stimulation or AC stimulation with weak currents induce deleterious changes when comparing active and sham groups. This study provides therefore additional information for researchers and ethics committees, adding important results to the safety pool of studies assessing the effects of cortical stimulation using weak electrical currents. Further studies in patients with neuropsychiatric disorders are warranted.

Cortical mapping with navigated transcranial magnetic stimulation in low-grade glioma surgery

Transcranial magnetic stimulation (TMS) is a promising method for both investigation and therapeutic treatment of psychiatric and neurologic disorders and, more recently, for brain mapping. This study describes the application of navigated TMS for motor cortex mapping in patients with a brain tumor located close to the precentral gyrus. Materials and methods: In this prospective study, six patients with low-grade gliomas in or near the precentral gyrus underwent TMS, and their motor responses were correlated to locations in the cortex around the lesion, generating a functional map overlaid on three-dimensional magnetic resonance imaging (MRI) scans of the brain. To determine the accuracy of this new method, we compared TMS mapping with the gold standard mapping with direct cortical electrical stimulation in surgery. The same navigation system and TMS-generated map were used during the surgical resection procedure. Results: The motor cortex could be clearly mapped using both methods. The locations corresponding to the hand and forearm, found during intraoperative mapping, showed a close spatial relationship to the homotopic areas identified by TMS mapping. The mean distance between TMS and direct cortical electrical stimulation (DES) was 4.16 +/- 1.02 mm (range: 2.56-5.27 mm). Conclusion: Preoperative mapping of the motor cortex with navigated TMS prior to brain tumor resection is a useful presurgical planning tool with good accuracy.

Stimulation of peripheral Kappa opioid receptors inhibits inflammatory hyperalgesia via activation of the PI3K gamma/AKT/nNOS/NO signaling pathway

Background: In addition to their central effects, opioids cause peripheral analgesia. There is evidence showing that peripheral activation of kappa opioid receptors (KORs) inhibits inflammatory pain. Moreover, peripheral mu-opioid receptor (MOR) activation are able to direct block PGE(2)-induced ongoing hyperalgesia However, this effect was not tested for KOR selective activation. In the present study, the effect of the peripheral activation of KORs on PGE(2)-induced ongoing hyperalgesia was investigated. The mechanisms involved were also evaluated. Results: Local (paw) administration of U50488 (a selective KOR agonist) directly blocked, PGE(2)-induced mechanical hyperalgesia in both rats and mice. This effect was reversed by treating animals with L-NMMA or N-propyl-L-arginine (a selective inhibitor of neuronal nitric oxide synthase, nNOS), suggesting involvement of the nNOS/NO pathway. U50488 peripheral effect was also dependent on stimulation of PI3K gamma/AKT because inhibitors of these kinases also reduced peripheral antinociception induced by U50488. Furthermore, U50488 lost its peripheral analgesic effect in PI3K gamma null mice. Observations made in vivo were confirmed after incubation of dorsal root ganglion cultured neurons with U50488 produced an increase in the activation of AKT as evaluated by western blot analyses of its phosphorylated form. Finally, immunofluorescence of DRG neurons revealed that KOR-expressing neurons also express PI3K gamma (congruent to 43%). Conclusions: The present study indicates that activation of peripheral KORs directly blocks inflammatory hyperalgesia through stimulation of the nNOS/NO signaling pathway which is probably stimulated by PI3K gamma/AKT signaling. This study extends a previously study of our group suggesting that PI3K gamma/AKT/nNOS/NO is an important analgesic pathway in primary nociceptive neurons.

Stimulation of peripheral Kappa opioid receptors inhibits inflammatory hyperalgesia via activation of the PI3Kγ/AKT/nNOS/NO signaling pathway

Abstract Background In addition to their central effects, opioids cause peripheral analgesia. There is evidence showing that peripheral activation of kappa opioid receptors (KORs) inhibits inflammatory pain. Moreover, peripheral μ-opioid receptor (MOR) activation are able to direct block PGE2-induced ongoing hyperalgesia However, this effect was not tested for KOR selective activation. In the present study, the effect of the peripheral activation of KORs on PGE2-induced ongoing hyperalgesia was investigated. The mechanisms involved were also evaluated. Results Local (paw) administration of U50488 (a selective KOR agonist) directly blocked, PGE2-induced mechanical hyperalgesia in both rats and mice. This effect was reversed by treating animals with L-NMMA or N-propyl-L-arginine (a selective inhibitor of neuronal nitric oxide synthase, nNOS), suggesting involvement of the nNOS/NO pathway. U50488 peripheral effect was also dependent on stimulation of PI3Kγ/AKT because inhibitors of these kinases also reduced peripheral antinociception induced by U50488. Furthermore, U50488 lost its peripheral analgesic effect in PI3Kγ null mice. Observations made in vivo were confirmed after incubation of dorsal root ganglion cultured neurons with U50488 produced an increase in the activation of AKT as evaluated by western blot analyses of its phosphorylated form. Finally, immunofluorescence of DRG neurons revealed that KOR-expressing neurons also express PI3Kγ (≅ 43%). Conclusions The present study indicates that activation of peripheral KORs directly blocks inflammatory hyperalgesia through stimulation of the nNOS/NO signaling pathway which is probably stimulated by PI3Kγ/AKT signaling. This study extends a previously study of our group suggesting that PI3Kγ/AKT/nNOS/NO is an important analgesic pathway in primary nociceptive neurons.

Inhibitory control of the human dorsolateral prefrontal cortex during the anti-saccade paradigm--a transcranial magnetic stimulation study

In the anti-saccade paradigm, subjects are instructed not to make a reflexive saccade to an appearing lateral target but to make an intentional saccade to the opposite side instead. The inhibition of reflexive saccade triggering is under the control of the dorsolateral prefrontal cortex (DLPFC). The critical time interval at which this inhibition takes place during the paradigm, however, is not exactly known. In the present study, we used single-pulse transcranial magnetic stimulation (TMS) to interfere with DLPFC function in 15 healthy subjects. TMS was applied over the right DLPFC either 100 ms before the onset of the visual target (i.e. -100 ms), at target onset (i.e. 0 ms) or 100 ms after target onset (i.e. +100 ms). Stimulation 100 ms before target onset significantly increased the percentage of anti-saccade errors to both sides, while stimulation at, or after, target onset had no significant effect. All three stimulation conditions had no significant influence on saccade latency of correct or erroneous anti-saccades. These findings show that the critical time interval at which the DLPFC controls the suppression of a reflexive saccade in the anti-saccade paradigm is before target onset. In addition, the results suggest the view that the triggering of correct anti-saccades is not under direct control of the DLPFC.

Single-pulse transcranial magnetic stimulation over the frontal eye field can facilitate and inhibit saccade triggering

The aim of this study was to investigate the effect of single-pulse transcranial magnetic stimulation on the triggering of saccades. The right frontal eye field was stimulated during modified gap and overlap paradigms with flashed presentation of the lateral visual target of 80 ms. In order to examine possible facilitating or inhibitory effects on saccade triggering, three different time intervals of stimulation were chosen, i.e. simultaneously with onset of the target, during the presentation and after target end. Stimulation applied simultaneously with target onset significantly decreased the latency of contralateral saccades in the gap but not in the overlap paradigm. Stimulation after target end significantly increased saccade latency for both sides in the gap paradigm and for the contralateral side in the overlap paradigm. Stimulation during presentation had no effect in either paradigm. The results show that, depending on the time interval and the paradigm tested, a facilitation or inhibition of saccade triggering can be achieved. The results are discussed in a context of two probable transcranial magnetic stimulation effects, a direct interference with the frontal eye field on the one hand and a remote interference with the superior colliculus on the other hand.

A three-dimensional histological atlas of the human basal ganglia. II. Atlas deformation strategy and evaluation in deep brain stimulation for Parkinson disease

OBJECT: The localization of any given target in the brain has become a challenging issue because of the increased use of deep brain stimulation to treat Parkinson disease, dystonia, and nonmotor diseases (for example, Tourette syndrome, obsessive compulsive disorders, and depression). The aim of this study was to develop an automated method of adapting an atlas of the human basal ganglia to the brains of individual patients. METHODS: Magnetic resonance images of the brain specimen were obtained before extraction from the skull and histological processing. Adaptation of the atlas to individual patient anatomy was performed by reshaping the atlas MR images to the images obtained in the individual patient using a hierarchical registration applied to a region of interest centered on the basal ganglia, and then applying the reshaping matrix to the atlas surfaces. RESULTS: Results were evaluated by direct visual inspection of the structures visible on MR images and atlas anatomy, by comparison with electrophysiological intraoperative data, and with previous atlas studies in patients with Parkinson disease. The method was both robust and accurate, never failing to provide an anatomically reliable atlas to patient registration. The registration obtained did not exceed a 1-mm mismatch with the electrophysiological signatures in the region of the subthalamic nucleus. CONCLUSIONS: This registration method applied to the basal ganglia atlas forms a powerful and reliable method for determining deep brain stimulation targets within the basal ganglia of individual patients.

Feasibility of Using EMG for Early Detection of the Facial Nerve During Robotic Direct Cochlear Access

HYPOTHESIS Facial nerve monitoring can be used synchronous with a high-precision robotic tool as a functional warning to prevent of a collision of the drill bit with the facial nerve during direct cochlear access (DCA). BACKGROUND Minimally invasive direct cochlear access (DCA) aims to eliminate the need for a mastoidectomy by drilling a small tunnel through the facial recess to the cochlea with the aid of stereotactic tool guidance. Because the procedure is performed in a blind manner, structures such as the facial nerve are at risk. Neuromonitoring is a commonly used tool to help surgeons identify the facial nerve (FN) during routine surgical procedures in the mastoid. Recently, neuromonitoring technology was integrated into a commercially available drill system enabling real-time monitoring of the FN. The objective of this study was to determine if this drilling system could be used to warn of an impending collision with the FN during robot-assisted DCA. MATERIALS AND METHODS The sheep was chosen as a suitable model for this study because of its similarity to the human ear anatomy. The same surgical workflow applicable to human patients was performed in the animal model. Bone screws, serving as reference fiducials, were placed in the skull near the ear canal. The sheep head was imaged using a computed tomographic scanner and segmentation of FN, mastoid, and other relevant structures as well as planning of drilling trajectories was carried out using a dedicated software tool. During the actual procedure, a surgical drill system was connected to a nerve monitor and guided by a custom built robot system. As the planned trajectories were drilled, stimulation and EMG response signals were recorded. A postoperative analysis was achieved after each surgery to determine the actual drilled positions. RESULTS Using the calibrated pose synchronized with the EMG signals, the precise relationship between distance to FN and EMG with 3 different stimulation intensities could be determined for 11 different tunnels drilled in 3 different subjects. CONCLUSION From the results, it was determined that the current implementation of the neuromonitoring system lacks sensitivity and repeatability necessary to be used as a warning device in robotic DCA. We hypothesize that this is primarily because of the stimulation pattern achieved using a noninsulated drill as a stimulating probe. Further work is necessary to determine whether specific changes to the design can improve the sensitivity and specificity.

Validation of targeting the ventrointermediate thalamic nucleus using Q-ball calculation in deep brain stimulation for tremor

Objective: Identification of the ventrointermediate thalamic nucleus (Vim) in modern 3T high-field MRI for image-based targeting in deep brain stimulation (DBS) is still challenging. To evaluate the usefulness and reliability of analyzing the connectivity with the cerebellum using Q-ball-calculation we performed a retrospective analysis. Method: 5 patients who underwent bilateral implantation of electrodes in the Vim for treatment of Essential Tremor between 2011 and 2012 received additional preoperative Q-ball imaging. Targeting was performed according to atlas coordinates and standard MRI. Additionally we performed a retrospective identification of the Vim by analyzing the connectivity of the thalamus with the dentate nucleus. The exact position of the active stimulation contact in the postoperative CT was correlated with the Vim as it was identified by Q-ball calculation. Results: Localization of the Vim by analysis of the connectivity between thalamus and cerebellum was successful in all 5 patients on both sides. The average position of the active contacts was 14.6 mm (SD 1.24) lateral, 5.37 mm (SD 0.094 posterior and 2.21 mm (SD 0.69) cranial of MC. The cranial portion of the dentato-rubro-thalamic tract was localized an average of 3.38 mm (SD 1.57) lateral and 1.5 mm (SD 1.22) posterior of the active contact. Conclusions: Connectivity analysis by Q-ball calculation provided direct visualization of the Vim in all cases. Our preliminary results suggest, that the target determined by connectivity analysis is valid and could possibly be used in addition to or even instead of atlas based targeting. Larger prospective calculations are needed to determine the robustness of this method in providing refined information useful for neurosurgical treatment of tremor.

NO-dependent CaMKII activation during -adrenergic stimulation of cardiac muscle

AIMS:During β-adrenergic receptor (β-AR) stimulation, phosphorylation of cardiomyocyte ryanodine receptors by protein kinases may contribute to an increased diastolic Ca(2+) spark frequency. Regardless of prompt activation of protein kinase A during β-AR stimulation, this appears to rely more on activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), by a not yet identified signalling pathway. The goal of the present study was to identify and characterize the mechanisms which lead to CaMKII activation and elevated Ca(2+) spark frequencies during β-AR stimulation in single cardiomyocytes in diastolic conditions. METHODS AND RESULTS:Confocal imaging revealed that β-AR stimulation increases endogenous NO production in cardiomyocytes, resulting in NO-dependent activation of CaMKII and a subsequent increase in diastolic Ca(2+) spark frequency. These changes of spark frequency could be mimicked by exposure to the NO donor GSNO and were sensitive to the CaMKII inhibitors KN-93 and AIP. In vitro, CaMKII became nitrosated and its activity remained increased independent of Ca(2+) in the presence of GSNO, as assessed with biochemical assays. CONCLUSIONS:β-AR stimulation of cardiomyocytes may activate CaMKII by a novel direct pathway involving NO, without requiring Ca(2+) transients. This crosstalk between two established signalling pathways may contribute to arrhythmogenic diastolic Ca(2+) release and Ca(2+) waves during adrenergic stress, particularly in combination with cardiac diseases. In addition, NO-dependent activation of CaMKII is likely to have repercussions in many cellular signalling systems and cell types.

DIRECT INPUTS TO OFF Α AND G9 GANGLION CELLS FROM AII AMACRINE CELLS IN RABBIT RETINA

In the mammalian retina, AII amacrine cells are essential in the rod pathway for dark-adapted vision. But they also have a “day job”, to provide inhibitory inputs to certain OFF ganglion cells in photopic conditions. This is known as crossover inhibition. Physiological evidence from several different labs implies that AII amacrine cells provide direct input to certain OFF ganglion cells. However, previous EM analysis of the rabbit retina suggests that the dominant output of the AII amacrine cell in sublamina a goes to OFF cone bipolar cells (Strettoi et al., 1992). Two OFF ganglion cell types in the rabbit retina, OFF α and G9, were identified by a combination of morphological criteria such as dendritic field size, dye coupling, mosaic properties and stratification depth. The AII amacrine cells (AIIs) were labeled with an antibody against calretinin and glycine receptors were marked with an antibody against the α1 subunit. This material was analyzed by triple-label confocal microscopy. We found the lobules of AIIs made close contacts at many points along the dendrites of individual OFF α and G9 ganglion cells. At these potential synaptic sites, we also found punctate labeling for the glycine receptor α1 subunit. The presence of a post-synaptic marker such as the α1 glycine receptor at contact points between AII lobules and OFF ganglion cells supports a direct inhibitory input from AIIs. This pathway provides for crossover inhibition in the rabbit retina whereby light onset provides an inhibitory signal to OFF α and G9 ganglion cells. Thus, these two OFF ganglion cell types receive a mixed excitatory and inhibitory drive in response to light stimulation.

Modulating presence and impulsiveness by external stimulation of the brain

BACKGROUND "The feeling of being there" is one possible way to describe the phenomenon of feeling present in a virtual environment and to act as if this environment is real. One brain area, which is hypothesized to be critically involved in modulating this feeling (also called presence) is the dorso-lateral prefrontal cortex (dlPFC), an area also associated with the control of impulsive behavior. METHODS In our experiment we applied transcranial direct current stimulation (tDCS) to the right dlPFC in order to modulate the experience of presence while watching a virtual roller coaster ride. During the ride we also registered electro-dermal activity. Subjects also performed a test measuring impulsiveness and answered a questionnaire about their presence feeling while they were exposed to the virtual roller coaster scenario. RESULTS Application of cathodal tDCS to the right dlPFC while subjects were exposed to a virtual roller coaster scenario modulates the electrodermal response to the virtual reality stimulus. In addition, measures reflecting impulsiveness were also modulated by application of cathodal tDCS to the right dlPFC. CONCLUSION Modulating the activation with the right dlPFC results in substantial changes in responses of the vegetative nervous system and changed impulsiveness. The effects can be explained by theories discussing the top-down influence of the right dlPFC on the "impulsive system".

DIRECT EFFECT OF MELATONIN UPON THE RELEASE OF GONADOTROPINS FROM THE SUPERFUSED PITUITARY GLAND OF THE MALE GOLDEN HAMSTER

The pineal gland is known to be light sensitive and to be involved in the seasonal reproduction of male golden hamster Mesocricetus auratus. In general, the pineal gland has been demonstrated to be inhibitory to the reproductive system of the male golden hamster. Melatonin is a pineal hormone which can mimic the action of the pineal gland upon the reproductive system. However, the actual site(s) of melatonin action in the hamster has not been demonstrated. In this study a direct effect of melatonin on the release of FSH and LH from superfused hamster pituitary glands was investigated.^ The superfused pituitary glands showed a stable in vitro basal release of FSH and LH for up to 10 hours. The superfused pituitaries demonstrated reproducible responses to repeated pulses of 10('-8) M LHRH, and a dose-dependent response to stimulation with different concentrations of LHRH.^ Melatonin inhibited the basal release of FSH and LH from superfused hamster pituitary glands. This effect of melatonin was specific and not a general indolamine or catecholamine effect.^ The superfused pituitaries had a diurnal differential responsiveness to physiological concentrations of melatonin with respect to FSH and LH release which were related to the light cycle used to maintain the experimental animals. A LD 14:10 photoperiod cycle was used with light on from 5 a.m. till 7 p.m.. With pituitary glands obtained at 8:30 a.m., the basal release of FSH exhibited an initial inhibition, a gradual rebound at approximately two hours after the beginning of melatonin superfusion, and a significant overshoot of FSH release after the cessation of infusion with melatonin (Morning Response). If the pituitary glands were obtained from hamsters which were sacrificed at 3:30 p.m., the release rate of FSH exhibited an inhibition during the entire period of melatonin infusion with a rebound effect appearing only after melatonin infusion was discontinued (Afternoon Response). There was no significant difference in the responsiveness of the pituitary gland to infusion with melatonin at either 8:30 a.m. or 3:30 p.m. with respect to LH release. Also, melatonin could not inhibit the gonadotropins response to continuous superfusion with 10('-9) M LHRH in pituitaries obtained at either 8:30 a.m. or 3:30 p.m., nor inhibit the stimulatory effect of pulsatile 10('-9) M LHRH. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI^

Direct visualization of antigen-specific T cells: HTLV-1 Tax11–19- specific CD8+ T cells are activated in peripheral blood and accumulate in cerebrospinal fluid from HAM/TSP patients

Human T lymphotropic virus type 1 (HTLV-1) -associated myelopathy/tropic spastic paraparesis is a demyelinating inflammatory neurologic disease associated with HTLV-1 infection. HTLV-1 Tax11–19-specific cytotoxic T cells have been isolated from HLA-A2-positive patients. We have used a peptide-loaded soluble HLA-A2–Ig complex to directly visualize HTLV-1 Tax11–19-specific T cells from peripheral blood and cerebrospinal fluid without in vitro stimulation. Five of six HTLV-1-associated myelopathy/tropic spastic paraparesis patients carried a significant number (up to 13.87%) of CD8+ lymphocytes specific for the HTLV-1 Tax11–19 peptide in their peripheral blood, which were not found in healthy controls. Simultaneous comparison of peripheral blood and cerebrospinal fluid from one patient revealed 2.5-fold more Tax11–19-specific T cells in the cerebrospinal fluid (23.7% vs. 9.4% in peripheral blood lymphocyte). Tax11–19-specific T cells were seen consistently over a 9-yr time course in one patient as far as 19 yrs after the onset of clinical symptoms. Further analysis of HTLV-1 Tax11–19-specific CD8+ T lymphocytes in HAM/TSP patients showed different expression patterns of activation markers, intracellular TNF-α and γ-interferon depending on the severity of the disease. Thus, visualization of antigen-specific T cells demonstrates that HTLV-1 Tax11–19-specific CD8+ T cells are activated, persist during the chronic phase of the disease, and accumulate in cerebrospinal fluid, showing their pivotal role in the pathogenesis of this neurologic disease.

Neuropeptides, by direct interaction with T cells, induce cytokine secretion and break the commitment to a distinct T helper phenotype

Searching for nervous system candidates that could directly induce T cell cytokine secretion, I tested four neuropeptides (NPs): somatostatin, calcitonin gene-related peptide, neuropeptide Y, and substance P. Comparing neuropeptide-driven versus classical antigen-driven cytokine secretion from T helper cells Th0, Th1, and Th2 autoimmune-related T cell populations, I show that the tested NPs, in the absence of any additional factors, directly induce a marked secretion of cytokines [interleukin 2 (IL-2), interferon-γ, IL-4, and IL-10) from T cells. Furthermore, NPs drive distinct Th1 and Th2 populations to a “forbidden” cytokine secretion: secretion of Th2 cytokines from a Th1 T cell line and vice versa. Such a phenomenon cannot be induced by classical antigenic stimulation. My study suggests that the nervous system, through NPs interacting with their specific T cell-expressed receptors, can lead to the secretion of both typical and atypical cytokines, to the breakdown of the commitment to a distinct Th phenotype, and a potentially altered function and destiny of T cells in vivo.