DEVELOPMENTAL NEUROBIOLOGY, Issue 2 2005
Masako Isokawa
Abstract We studied electrophysiological and morphological properties of astrocytes in the dentate gyrus of the rat hippocampus in slices. Intracellular application of Lucifer yellow revealed two types of morphology: one with a long process extruding from the cell body, and the other with numerous short processes surrounding the cell body. Their electrophysiological properties were either passive, that is, no detectable voltage-dependent conductance, or complex, with Na+/K+ currents similar to those reported in the Ammon's horn astrocytes. We did not find any morphological correlate to the types of electrophysiological profile or dye coupling. Chelation of cytoplasmic calcium ([Ca2+]i) by BAPTA increased the incidence of detecting a low Na+ conductance and transient outward K+ currents. However, an inwardly rectifying K+ current (Kir), a hallmark of differentiated CA1/3 astrocytes, was not a representative K+ -current in the complex dentate astrocytes, suggesting that these astrocytes could retain an immature form of K-currents. Dentate astrocytes may possess a distinct current profile that is different from those in CA1/3 Ammon's horn. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005 [source]

Electrophysiological and behavioural evidence for an antagonistic modulatory role of adenosine A2A receptors in dopamine D2 receptor regulation in the rat dopamine-denervated striatum

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2000
Ingrid Strömberg
Abstract It has been shown that striatal adenosine A2A receptors can antagonistically interact with dopamine D2 receptors at the membrane level leading to a decrease in the affinity and efficacy of D2 receptors. Extracellular recordings and rotational behaviour were employed to obtain a correlate to these findings in an animal model of Parkinson's disease (PD). The recordings were performed in rats with unilateral 6-hydroxydopamine (6-OHDA)-induced catecholamine depletion. While recording in the dopamine-depleted striatum, local applications of the dopamine D2 agonist quinpirole reduced neuronal activity. However, when the adenosine A2A antagonist MSX-3 was applied simultaneously with quinpirole, the inhibition of neuronal firing seen after quinpirole alone was significantly potentiated (P < 0.001, n = 11). In contrast, local application of CGS 21680 attenuated the effect of quinpirole. The doses of MSX-3 and CGS 21680 used to achieve the modulation of quinpirole action had no effect per se on striatal neuronal firing. Furthermore, rotational behaviour revealed that MSX-3 dose-dependently increased the number of turns when administrated together with a threshold dose of quinpirole while no enhancement was achieved when MSX-3 was combined with SKF 38393. MSX-3 alone did not induce rotational behaviour. In conclusion, this study shows that low ineffective doses of MSX-3 enhance the effect of quinpirole on striatal firing rate, while the A2A agonist exerts the opposite action. This mechanism gives a therapeutic potential to A2A antagonists in the treatment of PD by enhancing D2 receptor function. [source]

Synaptic plasticity in the basolateral amygdala in transgenic mice expressing dominant-negative cAMP response element-binding protein (CREB) in forebrain

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2000
G. Rammes
Abstract Electrophysiological and behavioural experiments were performed in transgenic mice expressing a dominant-negative form of cAMP response element-binding protein (CREBA133) in the limbic system. In control littermate in vitro slice preparation, tetanizing the lateral amygdala,basolateral amygdala (BLA) pathway with a single train (100 Hz for 1 s) produced short-term potentiation (STP) in the BLA. Five trains (10-s interstimulus interval) induced long-term potentiation (LTP), which was completely blocked by the N-methyl- d -aspartate (NMDA) receptor antagonist d(,)-2-amino-5-phosphonopentanoic acid (AP5; 50 ,m). When GABAergic (,-aminobutyric acid) inhibition was blocked by picrotoxin (10 ,m), LTP became more pronounced. Low-frequency stimulation (1 Hz for 15 min) induced either long-term depression (LTD) or depotentiation. LTD remained unaffected by AP5 (50 ,m) or by the L- and T-type Ca2+ -channel blockers nifedipine (20 ,m) and Ni2+ (50 ,m), but was prevented by picrotoxin (10 ,m), indicating a GABAergic link in the expression of LTD in the BLA. When conditioned fear was tested, a mild impairment was seen in one of three transgenic lines only. Although high levels of mRNA encoding CREBA133 lead to downregulation of endogenous CREB, expression of LTP and depotentiation were unaltered in BLA of these transgenic animals. These results could suggest that residual CREB activity was still present or that CREB per se is dispensable. Alternatively, other CREB-like proteins were able to compensate for impaired CREB function. [source]

Random fields,Union intersection tests for detecting functional connectivity in EEG/MEG imaging

HUMAN BRAIN MAPPING, Issue 8 2009
Felix Carbonell
Abstract Electrophysiological (EEG/MEG) imaging challenges statistics by providing two views of the same underlying spatio-temporal brain activity: a topographic view (EEG/MEG) and tomographic view (EEG/MEG source reconstructions). It is a common practice that statistical parametric mapping (SPM) for these two situations is developed separately. In particular, assessing statistical significance of functional connectivity is a major challenge in these types of studies. This work introduces statistical tests for assessing simultaneously the significance of spatio-temporal correlation structure between ERP/ERF components as well as that of their generating sources. We introduce a greatest root statistic as the multivariate test statistic for detecting functional connectivity between two sets of EEG/MEG measurements at a given time instant. We use some new results in random field theory to solve the multiple comparisons problem resulting from the correlated test statistics at each time instant. In general, our approach using the union-intersection (UI) principle provides a framework for hypothesis testing about any linear combination of sensor data, which allows the analysis of the correlation structure of both topographic and tomographic views. The performance of the proposed method is illustrated with real ERP data obtained from a face recognition experiment. Hum Brain Mapp 2009. © 2009 Wiley-Liss, Inc. [source]

Septal Dyskinesia and Global Left Ventricular Dysfunction in Pediatric Wolff-Parkinson-White Syndrome with Septal Accessory Pathway

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2010
BO SANG KWON M.D.
LV Dysfunction in WPW Syndrome.,Introduction: Echocardiographic studies have shown that some patients with Wolff-Parkinson-White (WPW) syndrome have myocardial dyskinesia in the segments precociously activated by an accessory pathway (AP). The aim of the present study was to determine the extent to which the AP contributes to global left ventricular (LV) dysfunction. Methods: Electrophysiological and echocardiographic data from 62 children with WPW (age at diagnosis = 5.9 ± 4.2 years) were retrospectively analyzed. Results: The left ventricular ejection fraction (LVEF) of patients with septal APs (53 ± 11%) was significantly lower than that of patients with right (62 ± 5%) or left (61 ± 4%) APs (P = 0.001). Compared to patients with normal septal motion (n = 56), patients with septal dyskinesia (n = 6) had a reduced LVEF (61 ± 4% and 42 ± 5%, respectively) and an increased LV end diastolic dimension (P < 0.001 for both comparisons). Multivariate analysis identified septal dyskinesia as the only significant risk factor for reduced LVEF. All 6 patients with septal dyskinesia had right septal APs, and a preexcited QRS duration that was longer than that of patients with normal septal motion (140 ± 18 ms and 113 ± 32 ms, respectively; P = 0.045). After RFA there were improvements in both intraventricular dyssynchrony (septal-to-posterior wall motion delay, from 154 ± 91 ms to 33 ± 17 ms) and interventricular septal thinning (from 3.0 ± 0.5 mm to 5.3 ± 2.6 mm), and a significant increase in LVEF (from 42 ± 5% to 67 ± 8%; P = 0.001). Conclusion: The dyskinetic segment activated by a right septal AP in WPW syndrome may lead to ventricular dilation and dysfunction. RFA produced mechanical resynchronization, reverse remodeling, and improvements in LV function. (J Cardiovasc Electrophysiol, Vol. 21, pp. 290,295, March 2010) [source]

Encoding of electrophysiology and other signals in MR images

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2007
Lars G. Hanson PhD
Abstract Purpose To develop a gradient insensitive, generic technique for recording of non-MR signals by use of surplus scanner bandwidth. Materials and Methods Relatively simple battery driven hardware is used to transform one or more signals into radio waves detectable by the MR scanner. Similar to the "magstripe" technique used for encoding of soundtracks in motion pictures, the electrical signals are in this way encoded as artifacts appearing in the MR images or spectra outside the region of interest. The encoded signals are subsequently reconstructed from the signal recorded by the scanner. Results Electrophysiological (EP) eye and heart muscular recording (electrooculography [EOG] and electrocardiography [ECG]) during fast echo planar imaging (EPI) is demonstrated with an expandable, modular 8-channel prototype implementation. The gradient artifacts that would normally be dominating EOG are largely eliminated. Conclusion The method provides relatively inexpensive sampling with inherent microsecond synchronization and it reduces gradient artifacts in physiological recordings significantly. When oversampling is employed, the method is compatible with all MR reconstruction and postprocessing techniques. J. Magn. Reson. Imaging 2007;25:1059,1066. © 2007 Wiley-Liss, Inc. [source]

Novel Polysaccharide-derived hydrogel prevents perineural adhesions in a rat model of sciatic nerve adhesion

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2010
Michiro Yamamoto
Abstract We investigated the effects of a novel carboxymethylcellulose (CMC)-derived hydrogel, in which phosphatidylethanolamine (PE) was introduced into the carboxyl groups of CMC, for preventing perineural adhesion after extensive internal neurolysis of rat sciatic nerve. Sciatic nerves were randomly assigned to one of the following groups: the Control group, operated but no treatment; the HA group, operated and treated with 1% hyaluronan; the CMC,PE(L) group, operated and treated with low-viscosity CMC,PE hydrogel; and the CMC,PE(H) group, operated and treated with high-viscosity CMC,PE hydrogel. Perineural adhesions were evaluated at 6 weeks. Nerves were also subjected to biomechanical testing to assess ultimate breaking strength. Electrophysiological and wet muscle weight measurements were performed. Breaking strengths were significantly lower for the CMC,PE(L) group than for the Control and HA groups. Latency was significantly longer for the Control group than for the CMC,PE(L) group at 20 days. The mean percentage of wet muscle weight to body weight was significantly lower for the Control group than for the CMC,PE(L) group at 6 weeks. Low-viscosity CMC,PE hydrogel appears to prevent perineural adhesions and allow early restoration of nerve function. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:284,288, 2010 [source]

Neuropathy Associated With Anti-Chondroitin Sulfate C IgM Antibodies

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 1 2001
B Bossi
Chondroitin Sulfate C (ChS-C), is a glycosaminoglycan present in the membranes of neurons and axons. Anti-ChS-C IgM antibodies have been reported in patients with predominantly sensory neuropathy (PN) often associated with IgM monoclonal gammopathy, but also in some neurological controls. In order to evaluate the frequency and clinical correlate of anti-ChS-C IgM antibodies, we tested them by a new Covalink ELISA technique in sera from 206 patients with IgM monoclonal gammopathy including 79 with PN (PN+IgM) with unknown IgM reactivity, 65 with PN with antibodies to the myelin-associated glycoprotein and 62 without PN, and from 33 patients with PN of other causes, 30 with other neurological and non-neurological diseases and 23 normal subjects. We only found high titers of anti-ChS-C IgM in two patients (1/128,000 and 1/256,000 respectively) with IgM monoclonal gammopathy: one had Waldenström Macroglobulinemia diagnosed seven years before and a 3 year history of slowly progressive limb weakness, finger paresthesias, unsteady gait and occasional nocturnal cramps. Neurological examination revealed a predominantly large-fiber sensory neuropathy with mild distal atrophy and weakness in upper and lower limbs. Electrophysiological and morphological studies were suggestive of a predominantly demyelinating neuropathy. The other patient had IgM MGUS without PN at the time of antibody testing but developed finger paresthesias seven years later, when he had decreased position sense and abnormal sensory nerve conduction studies. In conclusion high titers of anti-ChS-C IgM, though infrequent, were always associated with the presence or development of sensory PN in patients with IgM M-protein, supporting a possible role for these antibodies in the neuropathy. [source]

Electrophysiological and neuropsychological tests for the diagnosis of subclinical hepatic encephalopathy and prediction of overt encephalopathy

LIVER INTERNATIONAL, Issue 3 2002
Nandini Saxena
Abstract: Background: Subclinical hepatic encephalopathy (SHE) features in 30,84% of patients with cirrhosis of the liver. Its clinical significance with regards to progression to overt encephalopathy has however, not been established. Aims: The present study was conducted (i) to compare the diagnostic usefulness of neuropsychological tests with that of electrophysiological (EP) tests in detection of SHE, and (ii) to examine the natural course of SHE. Methods: Seventy-five-nonencephalopathic cirrhotics (11 females, 64 males; mean (± SD) age 43.6 (± 11.7) years; mean (± SD) education 11(± 3) years) were studied using a battery of tests for intelligence and memory, the number connection test (NCT), and EP tests viz. electroencephalogram (EEG) and auditory P300 event related potentials (P3ERP). All the patients were followed up for a period of 6 months to 2 years for development of overt encephalopathy. Results: Thirty-five out of 75(47%) patients were diagnosed to have SHE based on at least one abnormal test result. The P3ERP latencies detected SHE in maximum number of patients (23%) followed by EEG (21%). Nearly 59% of patients with SHE progressed to overt encephalopathy within a mean duration of 4 months. Multivariate analysis showed that prior episode of encephalopathy (RR = 6.3; 95% CI = 2.0,19.7), abnormality on EEG (RR = 7.5; 95% CI = 2.2,25.3), abnormal performance on psychometric battery of tests (RR = 35.2; 95% CI = 4.3,287.3), occurrence of gastrointestinal bleed (RR = 19.3; 95% CI = 4.1,88.9), occurrence of dehydration (RR = 10.7; 95% CI = 2.5,45.4) and infection (RR = 11.4; 95% CI = 2.0,64.4) had significantly higher risk for development of overt encephalopathy. Conclusions: EP methods were more sensitive in detection of SHE. Amongst all the tests used, presence of only an abnormal EEG was significantly associated with development of overt encephalopathy along with the precipitating factors. [source]

Experimental study of vascularized nerve graft: Evaluation of nerve regeneration using choline acetyltransferase activity

MICROSURGERY, Issue 2 2001
Makoto Iwai M.D.
A comparative study of nerve regeneration was performed on vascularized nerve graft (VNG) and free nerve graft (FNG) in Fischer strain rats. A segment of the sciatic nerve with vascular pedicle of the femoral artery and vein was harvested from syngeneic donor rat for the VNG group and the sciatic nerve in the same length without vascular pedicle was harvested for the FNG group. They were transplanted to a nerve defect in the sciatic nerve of syngeneic recipient rats. At 2, 4, 6, 8, 12, 16, and 24 weeks after operation, the sciatic nerves were biopsied and processed for evaluation of choline acetyltransferase (CAT) activity, histological studies, and measurement of wet weight of the muscle innervated by the sciatic nerve. Electrophysiological evaluation of the grafted nerve was also performed before sacrifice. The average CAT activity in the distal to the distal suture site was 383 cpm in VNG and 361 cpm in FNG at 2 weeks; 6,189 cpm in VNG and 2,264 cpm in FNG at 4 weeks; and 11,299 cpm in VNG and 9,424 cpm in FNG at 6 weeks postoperatively. The value of the VNG group was statistically higher than that of the FNG group at 4 weeks postoperatively. Electrophysiological and histological findings also suggested that nerve regeneration in the VNG group was superior to that in the FNG group during the same period. However, there was no significant difference between the two groups after 6 weeks postoperatively in any of the evaluations. The CAT measurement was useful in the experiments, because it was highly sensitive and reproducible. © 2001 Wiley-Liss, Inc. MICROSURGERY 24:43,51 2001 [source]

Electrophysiological mapping for the implantation of deep brain stimulators for Parkinson's disease and tremor

MOVEMENT DISORDERS, Issue S14 2006
Robert E. Gross MD
Abstract The vast majority of centers use electrophysiological mapping techniques to finalize target selection during the implantation of deep brain stimulation (DBS) leads for the treatment of Parkinson's disease and tremor. This review discusses the techniques used for physiological mapping and addresses the questions of how various mapping strategies modify target selection and outcome following subthalamic nucleus (STN), globus pallidus internus (GPi), and ventralis intermedius (Vim) deep brain stimulation. Mapping strategies vary greatly across centers, but can be broadly categorized into those that use microelectrode or semimicroelectrode techniques to optimize position prior to implantation and macrostimulation through a macroelectrode or the DBS lead, and those that rely solely on macrostimulation and its threshold for clinical effects (benefits and side effects). Microelectrode criteria for implantation into the STN or GPi include length of the nucleus recorded, presence of movement-responsive neurons, and/or distance from the borders with adjacent structures. However, the threshold for the production of clinical benefits relative to side effects is, in most centers, the final, and sometimes only, determinant of DBS electrode position. Macrostimulation techniques for mapping, the utility of microelectrode mapping is reflected in its modification of electrode position in 17% to 87% of patients undergoing STN DBS, with average target adjustments of 1 to 4 mm. Nevertheless, with the absence of class I data, and in consideration of the large number of variables that impact clinical outcome, it is not possible to conclude that one technique is superior to the other in so far as motor Unified Parkinson's Disease Rating Scale outcome is concerned. Moreover, mapping technique is only one out of many variables that determine the outcome. The increase in surgical risk of intracranial hemorrhage correlated to the number of microelectrode trajectories must be considered against the risk of suboptimal benefits related to omission of this technique. © 2006 Movement Disorder Society [source]

Morvan's syndrome: Clinical, laboratory, and in vitro electrophysiological studies

MUSCLE AND NERVE, Issue 2 2004
Wolfgang N. Löscher MD
Abstract Morvan's syndrome is a rare disorder characterized by neuromyotonia, hyperhidrosis, and central nervous system dysfunction. We report a patient with features of this syndrome, but who initially presented with breathing difficulties. Concentric needle electromyography showed an abundance of myokymic and neuromyotonic discharges. Exercise tests and repetitive nerve stimulation showed a decrement,increment response of compound muscle action potentials. Antibodies against voltage-gated potassium channels were not detected on repeated testing, but the presence of oligoclonal bands in the cerebrospinal fluid (CSF) suggested an autoimmune etiology. At follow-up over 3 years, no cancer was found. Electrophysiological in vitro studies of effects of patient serum and CSF on rat nerves provided no evidence of altered voltage-gated sodium or potassium conductances. We conclude that putative humoral factors do not block ion channels acutely but may cause channel dysfunction with chronic exposure. Muscle Nerve 30: 157,163, 2004 [source]

Neurofibromatosis 2 with peripheral neuropathies: Electrophysiological, pathological and genetic studies of a Taiwanese family

NEUROPATHOLOGY, Issue 5 2010
Hung-Chou Kuo
The objective of this study was to assess peripheral nerve involvement and DNA mutation of the neurofibromatosis type 2 (NF2) gene (NF2) in a Taiwanese family with classic NF2. Eleven members (six symptomatic and five asymptomatic) of a family carrying NF2 underwent clinical examination, neuroimaging, and electrophysiological analysis. Mutation and linkage analyses were conducted on DNA samples prepared from peripheral blood (all individuals), a sural nerve biopsy specimen (one symptomatic member), and a tumor specimen (another symptomatic member). Six of the 11 members were diagnosed with classic NF2. DNA sequencing of the tumor specimen demonstrated a frameshift mutation with 756delC on exon 8 of NF2. Three affected subjects showed clinical variability of the neuropathic disorders. Electrophysiological studies demonstrated variation in the disease pattern and severity of peripheral nerve involvement in five affected subjects. The morphometric assessment of the sural nerve biopsy specimen showed a marked reduction in both large myelinated and unmyelinated fibre density and increased density of non-myelinating Schwann cell nuclei. Apart from numerous pathological nuclei of isolated Schwann cells, multiple profiles of non-myelinating Schwann cell subunits were apparent in the endoneurium. Schwann cell proliferation in association with first-hit mutation of the merlin gene might be responsible for the NF2-associated neuropathy. Sural nerve biopsy showed a progressive neuropathy in the disease. Further, we suggest nonmyelinating Schwann cells are involved in NF2 neuropathy. [source]

Electrophysiological and behavioural identification of host kairomones as olfactory cues for Culicoides impunctatus and C. nubeculosus

PHYSIOLOGICAL ENTOMOLOGY, Issue 1 2000
A. Bhasin
Summary Electroantennograms (EAGs) were recorded from wild-caught parous, female Culicoides impunctatus (Goetghebuer) in response to components of host odour. Nine synthetic compounds were found to be electrophysiologically active, eliciting EAGs which were significantly different from solvent control. An EAG hierarchy was established, in which 1-octen-3-ol elicited the highest amplitude EAGs, followed by acetone, lactic acid and butanone. The overall responses to phenolic compounds were reduced compared to the non-phenolics. Subsequent behavioural analyses of the effects of these compounds when tested singly revealed 1-octen-3-ol, acetone and butanone to be attractive over specific stimulus doses. Exposure to supra-optimal doses modified the insects' behaviour; insects either ceased to respond or were repelled. Lactic acid was attractive at the lowest dose tested but was repellent at high doses. Behavioural responses to the phenolic components of host odour and lactic acid were similar, generally causing arrestment at low doses and repelling at the higher doses tested. A comparison of EAG profiles and behavioural assays between laboratory-reared Culicoides nubeculosus (Meigen) and C. impunctatus suggested that the same kairomones are utilized by both species, with C. nubeculosus being less sensitive than C. impunctatus. The EAG hierarchy of C. nubeculosus to the four non-phenolics was identical to that of C. impunctatus. [source]

Electrophysiological correlates of decreasing and increasing emotional responses to unpleasant pictures

PSYCHOPHYSIOLOGY, Issue 1 2009
Jason S. Moser
Abstract We examined event-related brain potential (ERP) modulations during the anticipation and processing of unpleasant pictures under instructions to cognitively decrease and increase negative emotion. Instructions to decrease and increase negative emotion modulated the ERP response to unpleasant pictures in the direction of emotional intensity beginning around 400 ms and lasting several seconds. Decrease, but not increase, instructions also elicited enhanced frontal negativity associated with orienting and preparation prior to unpleasant picture onset. Last, ERP modulation by unpleasant pictures began around 300 ms, just prior to regulation effects, suggesting that appraisal of emotion occurs before emotion regulation. Together, the current findings underscore the utility of ERPs in illuminating the time course of emotion modulation and regulation that may help to refine extant theoretical models. [source]

Electrophysiological correlates of direct selection by color

PSYCHOPHYSIOLOGY, Issue 4 2008
Esther Vierck
Abstract We report an experiment using event-related potentials (ERPs) to study selection by color uncontaminated from selection by location. Participants monitored an RSVP sequence for a given target letter that could appear in upper- or lowercase. Prior to the sequence, a cue indicated the most likely color of the target letter. Replicating E. Vierck and J. Miller (2005), upper-/lowercase discrimination accuracy was higher following valid than invalid color cues. Within the ERPs, the target onset produced a negative component between 150 and 350 ms at occipital sites, with shorter latencies following valid than invalid cues. We also found larger amplitude components for valid than invalid color cues at central and parietal sites between 150 and 325 ms. The results not only demonstrate clear effects of color cuing on both behavior and ERPs but also suggest that the observed ERP differences between valid versus invalid trials mediate the behavioral effects. [source]

Electrophysiological correlates of response inhibition in children and adolescents with ADHD: Influence of gender, age, and previous treatment history

PSYCHOPHYSIOLOGY, Issue 6 2007
Mario Liotti
Abstract Deficits in response inhibition may be at the core of the cognitive syndrome in ADHD. Here, inhibitory control mechanisms were studied in 36 ADHD-combined type and 30 healthy children by exploring the event-related brain activity during the Stop Signal task. The influence of age, gender, and previous treatment history was evaluated. The ADHD group showed reduced N200 wave amplitudes. For successful inhibitions, the N200 reduction was greatest over right inferior frontal scalp, and only the control group showed a success-related enhancement of such right frontal N200. Source analysis identified a source of the N200 group effect in right dorsolateral prefrontal cortex. Finally, a late positive wave to failed inhibitions was selectively reduced only in treatment-naïve ADHD children, suggesting that chronic stimulants may normalize late conscious error recognition. Both effects were independent of gender and age. [source]

Music and emotion: Electrophysiological correlates of the processing of pleasant and unpleasant music

PSYCHOPHYSIOLOGY, Issue 2 2007
Daniela Sammler
Abstract Human emotion and its electrophysiological correlates are still poorly understood. The present study examined whether the valence of perceived emotions would differentially influence EEG power spectra and heart rate (HR). Pleasant and unpleasant emotions were induced by consonant and dissonant music. Unpleasant (compared to pleasant) music evoked a significant decrease of HR, replicating the pattern of HR responses previously described for the processing of emotional pictures, sounds, and films. In the EEG, pleasant (contrasted to unpleasant) music was associated with an increase of frontal midline (Fm) theta power. This effect is taken to reflect emotional processing in close interaction with attentional functions. These findings show that Fm theta is modulated by emotion more strongly than previously believed. [source]

Electrophysiological correlates of threat processing in spider phobics

PSYCHOPHYSIOLOGY, Issue 5 2005
Iris-Tatjana Kolassa
Abstract The electrocortical correlates of the processing of feared/fear-relevant and neutral stimuli were investigated in a pictorial emotional Stroop paradigm with spider phobic, social phobic, and nonphobic subjects. Subjects identified either the color of red or blue pictures of spiders, birds, or flowers (emotional Stroop task) or the object itself (identification task) by pressing different buttons. No emotional Stroop interference was found for spider phobic subjects when identifying the color of spiders as opposed to neutral stimuli. However, in the object identification task, spider phobic subjects identified spiders significantly faster than birds or flowers. Parietal P300 and P400 amplitudes were enhanced independent of task in spider phobic but not in nonphobic subjects when viewing pictures of spiders, which is consistent with previous studies showing that highly unpleasant and arousing pictures affect parietal late positive potentials. [source]

Muscarinic cationic current in gastrointestinal smooth muscles: signal transduction and role in contraction

AUTONOMIC & AUTACOID PHARMACOLOGY, Issue 3 2006
T. Unno
Summary 1 The muscarinic receptor plays a key role in the parasympathetic nervous control of various peripheral tissues including gastrointestinal tract. The neurotransmitter acetylcholine, via activating muscarinic receptors that exist in smooth muscle, produces its contraction. 2 There is the opening of cationic channels as an underlying mechanism. The opening of cationic channels results in influxes of Ca2+ via the channels into the cell and also via voltage-dependent Ca2+ channels which secondarily opened in response to the depolarization, providing an amount of Ca2+ for activation of the contractile proteins. 3 Electrophysiological and pharmacological studies have shown that the cationic channels as well as muscarinic receptors exist in many visceral smooth muscle cells. However, the activation mechanisms of the cationic channels are still unclear. 4 In this article, we summarize the current knowledge of the muscarinic receptor-operated cationic channels, focusing on the receptor subtype, G protein and other signalling molecules that are involved in activation of these channels and on the molecular characterisitics of the channel. This will improve strategies aimed at developing new selective pharmacological agents and understanding the activation mechanism and functions of these channels in physiological systems. [source]

Electrophysiological and Neurochemical Evidence for Voltage-Dependent Ca2+ Channel Blockade by a Novel Neuroprotective Agent NS-7,

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2001
Michiko Oka
In rat dorsal root ganglion neurones, NS-7 (0.3,100 ,M) inhibited the whole-cell Ba2+ currents (IBa) in a voltage-dependent manner, in which the compound more potently blocked the IBa elicited from the holding potential of ,40 mV than that induced from ,80 mV. In slices of rat cerebral cortex, KCl-evoked nitric oxide synthesis was markedly inhibited by ,-conotoxin GVIA and ,-agatoxin IVA, but only slightly attenuated by nifedipine, suggesting that the response is mediated predominantly through activation of N-type and P/Q-type Ca2+ channels. NS-7 (1,100 ,M) inhibited the KCl-stimulated nitric oxide synthesis in a manner dependent on the intensity of the depolarizing stimuli. Moreover, weak but significant inhibitory effect of NS-7 was observed even after wash-out. Similar voltage-dependent inhibition of the KCl response was observed by a limited concentration (10 ,M) of verapamil. These findings indicate that NS-7 in several concentrations blocks Ca2+ channel in a voltage-dependent manner. [source]

Critical role of Nitric Oxide on Nicotine-Induced Hyperactivation of Dopaminergic Nigrostriatal System: Electrophysiological and Neurochemical evidence in Rats

CNS: NEUROSCIENCE AND THERAPEUTICS, Issue 3 2010
Vincenzo Di Matteo
Nicotine, the main psychoactive ingredient in tobacco, stimulates dopamine (DA) function, increasing DA neuronal activity and DA release. DA is involved in both motor control and in the rewarding and reinforcing effects of nicotine; however, the complete understanding of its molecular mechanisms is yet to be attained. Substantial evidence indicates that the reinforcing properties of drugs of abuse, including nicotine, can be affected by the nitric oxide (NO) system, which may act by modulating central dopaminergic function. In this study, using single cell recordings in vivo coupled with microiontophoresis and microdialysis in freely moving animals, the role of NO signaling on the hyperactivation elicited by nicotine of the nigrostriatal system was investigated in rats. Nicotine induced a dose-dependent increase of the firing activity of the substantia nigra pars compacta (SNc) DA neurons and DA and 3,4-dihydroxyphenylacetic acid (DOPAC) release in the striatum. Pharmacological manipulation of the NO system did not produce any change under basal condition in terms of neuronal discharge and DA release. In contrast, pretreatments with two NO synthase (NOS) inhibitors, N-,-nitro- l -arginine methyl ester (l -NAME) and 7-nitroindazole (7-NI) were both capable of blocking the nicotine-induced increase of SNc DA neuron activity and DA striatal levels. The effects of nicotine in l -NAME and 7-NI-pretreated rats were partially restored when rats were pretreated with the NO donor molsidomine. These results further support the evidence of an important role played by NO on modulation of dopaminergic function and drug addiction, thus revealing new pharmacological possibilities in the treatment of nicotine dependence and other DA dysfunctions. [source]

Scn3b knockout mice exhibit abnormal sino-atrial and cardiac conduction properties

ACTA PHYSIOLOGICA, Issue 1 2010
P. Hakim
Abstract Aim:, In contrast to extensive reports on the roles of Nav1.5 , -subunits, there have been few studies associating the , -subunits with cardiac arrhythmogenesis. We investigated the sino-atrial and conduction properties in the hearts of Scn3b,/, mice. Methods:, The following properties were compared in the hearts of wild-type (WT) and Scn3b,/, mice: (1) mRNA expression levels of Scn3b, Scn1b and Scn5a in atrial tissue. (2) Expression of the ,3 protein in isolated cardiac myocytes. (3) Electrocardiographic recordings in intact anaesthetized preparations. (4) Bipolar electrogram recordings from the atria of spontaneously beating and electrically stimulated Langendorff-perfused hearts. Results:,Scn3b mRNA was expressed in the atria of WT but not Scn3b,/, hearts. This was in contrast to similar expression levels of Scn1b and Scn5a mRNA. Immunofluorescence experiments confirmed that the ,3 protein was expressed in WT and absent in Scn3b,/, cardiac myocytes. Lead I electrocardiograms from Scn3b,/, mice showed slower heart rates, longer P wave durations and prolonged PR intervals than WT hearts. Spontaneously beating Langendorff-perfused Scn3b,/, hearts demonstrated both abnormal atrial electrophysiological properties and evidence of partial or complete dissociation of atrial and ventricular activity. Atrial burst pacing protocols induced atrial tachycardia and fibrillation in all Scn3b,/, but hardly any WT hearts. Scn3b,/, hearts also demonstrated significantly longer sinus node recovery times than WT hearts. Conclusion:, These findings demonstrate, for the first time, that a deficiency in Scn3b results in significant atrial electrophysiological and intracardiac conduction abnormalities, complementing the changes in ventricular electrophysiology reported on an earlier occasion. [source]

Development of three-dimensional architecture of the neuroepithelium: Role of pseudostratification and cellular ,community'

DEVELOPMENT GROWTH & DIFFERENTIATION, Issue 2008
Takaki Miyata
This review discusses the development of the neuroepithelium (NE) and its derivative ventricular zone (VZ), from which the central nervous system (CNS) is formed. First, the histological features of the NE and VZ are summarized, highlighting the phenomenon of pseudostratification, which is achieved by polarization and interkinetic nuclear migration (INM) of neural progenitor cells. Next, our current understanding of the cellular and molecular mechanisms and biological significance of INM and pseudostratification are outlined. The recent three-dimensional time-lapse observations revealing heterogeneity in cell lineages within the NE and VZ are also described, focusing on the neuronal lineage. Finally, the necessity of comprehensive studies on cell-cell interactions in the NE/VZ is discussed, as well as the importance of electrophysiological and biomechanical approaches. In particular, we suggest that a systems biology approach to the NE/VZ as a cellular ,community' may be fruitful. [source]

The role of epilepsy in early language development in a child with a congenital lesion in the right hemisphere

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 11 2008
C Mayor-Dubois MA
Early epilepsy is known to worsen the developmental prognosis of young children with a congenital focal brain lesion, but its direct role is often very difficult to delineate from the other variables. This requires prolonged periods of follow-up with simultaneous serial electrophysiological and developmental assessments which are rarely obtained. We studied a male infant with a right prenatal infarct in the territory of the right middle cerebral artery resulting in a left spastic hemiparesis, and an epileptic disorder (infantile spasms with transient right hemihypsarrhythmia and focal seizures) from the age of 7 months until the age of 4 years. Pregnancy and delivery were normal. A dissociated delay of early language acquisition affecting mainly comprehension without any autistic features was documented. This delay was much more severe than usually expected in children with early focal lesions, and its evolution, with catch-up to normal, was correlated with the active phase of the epilepsy. We postulate that the epilepsy specifically amplified a pattern of delayed language emergence, mainly affecting lexical comprehension, reported in children with early right hemisphere damage. [source]

Electrophysiological and morphological characterization of dentate astrocytes in the hippocampus

Ophthalmological, cognitive, electrophysiological and MRI assessment of visual processing in preterm children without major neuromotor impairment

DEVELOPMENTAL SCIENCE, Issue 5 2010
Michelle O'Reilly
Many studies report chronic deficits in visual processing in children born preterm. We investigated whether functional abnormalities in visual processing exist in children born preterm but without major neuromotor impairment (i.e. cerebral palsy). Twelve such children (< 33 weeks gestation or birthweight < 1000 g) without major neuromotor impairment and 12 born full-term controls were assessed at 8,12 years of age by means of ophthalmological assessment (visual acuity, colour vision, stereopsis, stereoacuity, visual fields, ocular motility, motor fusion), cognitive tests of visual-motor, visual-perceptual and visual-spatial skills and pattern-reversal visual evoked potentials (PR-VEPs). All participants also underwent magnetic resonance imaging (MRI) of the brain and neuromotor assessments. No significant differences were found between the groups on the ophthalmological, visual cognitive, neurological, neuromotor or MRI measures. The P100 component of the PR-VEP showed a significantly shorter latency in the preterm compared with the full-term participants. Whilst this P100 finding suggests that subtle abnormalities may exist at the neurophysiological level, we conclude that visual dysfunction is not systematically associated with preterm birth in the context of normal neurological status. [source]

Molecular Neuropathology of Temporal Lobe Epilepsy: Complementary Approaches in Animal Models and Human Disease Tissue

EPILEPSIA, Issue 2007
Michael Majores
Summary:, Patients with temporal lobe epilepsies (TLE) frequently develop pharmacoresistance to antiepileptic treatment. In individuals with drug-refractory TLE, neurosurgical removal of the epileptogenic focus provides a therapy option with high potential for seizure control. Biopsy specimens from TLE patients constitute unique tissue resources to gain insights in neuropathological and molecular alterations involved in human TLE. Compared to human tissue specimens in most neurological diseases, where only autopsy material is available, the bioptic tissue samples from pharmacoresistant TLE patients open rather exceptional preconditions for molecular biological, electrophysiological as well as biochemical experimental approaches in human brain tissue, which cannot be carried out in postmortem material. Pathological changes in human TLE tissue are multiple and relate to structural and cellular reorganization of the hippocampal formation, selective neurodegeneration, and acquired changes of expression and distribution of neurotransmitter receptors and ion channels, underlying modified neuronal excitability. Nevertheless, human TLE tissue specimens have some limitations. For obvious reasons, human TLE tissue samples are only available from advanced, drug-resistant stages of the disease. However, in many patients, a transient episode of status epilepticus (SE) or febrile seizures in childhood can induce multiple structural and functional alterations that after a latency period result in a chronic epileptic condition. This latency period, also referred to as epileptogenesis, cannot be studied in human TLE specimens. TLE animal models may be particularly helpful in order to shed characterize new molecular pathomechanisms related to epileptogenesis and open novel therapeutic strategies for TLE. Here, we will discuss experimental approaches to unravel molecular,neuropathological aspects of TLE and highlight characteristics and potential of molecular studies in human and/or experimental TLE. [source]

The patterns of spontaneous Ca2+ signals generated by ventral spinal neurons in vitro show time-dependent refinement

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
Sara Sibilla
Abstract Embryonic spinal neurons maintained in organotypic slice culture are known to mimic certain maturation-dependent signalling changes. With such a model we investigated, in embryonic mouse spinal segments, the age-dependent spatio-temporal control of intracellular Ca2+ signalling generated by neuronal populations in ventral circuits and its relation with electrical activity. We used Ca2+ imaging to monitor areas located within the ventral spinal horn at 1 and 2 weeks of in vitro growth. Primitive patterns of spontaneous neuronal Ca2+ transients (detected at 1 week) were typically synchronous. Remarkably, such transients originated from widespread propagating waves that became organized into large-scale rhythmic bursts. These activities were associated with the generation of synaptically mediated inward currents under whole-cell patch-clamp. Such patterns disappeared during longer culture of spinal segments: at 2 weeks in culture, only a subset of ventral neurons displayed spontaneous, asynchronous and repetitive Ca2+ oscillations dissociated from background synaptic activity. We observed that the emergence of oscillations was a restricted phenomenon arising together with the transformation of ventral network electrophysiological bursting into asynchronous synaptic discharges. This change was accompanied by the appearance of discrete calbindin immunoreactivity against an unchanged background of calretinin-positive cells. It is attractive to assume that periodic oscillations of Ca2+ confer a summative ability to these cells to shape the plasticity of local circuits through different changes (phasic or tonic) in intracellular Ca2+. [source]

Inter-hemispheric inhibition is impaired in mirror dystonia

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
S. Beck
Abstract Surround inhibition, a neural mechanism relevant for skilled motor behavior, has been shown to be deficient in the affected primary motor cortex (M1) in patients with focal hand dystonia (FHD). Even in unilateral FHD, however, electrophysiological and neuroimaging studies have provided evidence for bilateral M1 abnormalities. Clinically, the presence of mirror dystonia, dystonic posturing when the opposite hand is moved, also suggests abnormal interhemispheric interaction. To assess whether a loss of inter-hemispheric inhibition (IHI) may contribute to the reduced surround inhibition, IHI towards the affected or dominant M1 was examined in 13 patients with FHD (seven patients with and six patients without mirror dystonia, all affected on the right hand) and 12 right-handed, age-matched healthy controls (CON group). IHI was tested at rest and during three different phases of a right index finger movement in a synergistic, as well as in a neighboring, relaxed muscle. There was a trend for a selective loss of IHI between the homologous surrounding muscles in the phase 50 ms before electromyogram onset in patients with FHD. Post hoc analysis revealed that this effect was due to a loss of IHI in the patients with FHD with mirror dystonia, while patients without mirror dystonia did not show any difference in IHI modulation compared with healthy controls. We conclude that mirror dystonia may be due to impaired IHI towards neighboring muscles before movement onset. However, IHI does not seem to play a major role in the general pathophysiology of FHD. [source]