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Background Activity (background + activity)
Selected AbstractsControl of the triceps surae during the postural sway of quiet standingACTA PHYSIOLOGICA, Issue 3 2007C. D. Tokuno Abstract Aim:, The present study investigated how the triceps surae are controlled at the spinal level during the naturally occurring postural sway of quiet standing. Methods:, Subjects stood on a force platform as electrical stimuli were applied to the posterior tibial nerve when the center of pressure (COP) was either 1.6 standard deviations anterior (COPant) or posterior (COPpost) to the mean baseline COP signal. Peak-to-peak amplitudes of the H-reflex and M-wave from the soleus (SOL) and medial gastrocnemius (MG) muscles were recorded to assess the efficacy of the Ia pathway. Results:, A significant increase in the Hmax : Mmax ratio for both the SOL (12 ± 6%) and MG (23 ± 6%) was observed during the COPant as compared to the COPpost condition. The source of the modulation between COP conditions cannot be determined from this study. However, the observed changes in the synaptic efficacy of the Ia pathway are unlikely to be simply a result of an altered level of background electromyographic activity in the triceps surae. This was indicated by the lack of differences observed in the Hmax : Mmax ratio when subjects stood without postural sway (via the use of a tilt table) at two levels of background activity. Conclusions:, It is suggested that the phase-dependent modulation of the triceps surae H-reflexes during the postural sway of quiet standing functions to maintain upright stance and may explain the results from previous studies, which, until now, had not taken the influence of postural sway on the H-reflex into consideration. [source] Movement-Induced Focal Motor Seizures and Choreoathetosis As- sociated with Nonketotic Hyperglycemia: A Case ReportEPILEPSIA, Issue 2000Hisashi Tanaka Case Report: We report the case of a diabetic woman who developed right-sided reflex seizures and bilateral choreoathetosis during an episode of nonketotic hyperglycemia. The patient was a 67-year-old woman with a 14-year history of HCV-related liver cirrhosis who experienced polydipsia and polyuria in January 1998. She began to have episodes of abnormal hyperkinetic movements of the right upper extremity and tonic-clonic seizures in the right arm triggered by voluntary movements of right or bilateral arms in the beginning of March 1998. The seizures increased in frequency and consequently left her disabled. She was admitted to our hospital with complaints of these abnormal motor phenomena on March 9, 1998. Neurological examinations revealed that she was alert, well-oriented, and that cranial nerve functions were normal. Slight motor weakness of the right upper limb and deep tendon hyporeflexes were observed in all extremities. Sensations and cerebellar functions were intact. Choreic or athetotic involuntary movements were seen in the bilateral upper limbs and neck. These involuntary movements were increased by voluntary movement or posturing of the upper limbs. The focal tonic-clonic seizures were easily triggered by voluntary movements such as knotting a cord. This seizure suddenly began by tonic movements in the right upper limb and gradually progressed to the right hemi-face and neck without loss of consciousness. The average duration of seizures was about one minute. The laboratory data demonstrated mild leukocytopenia, thrombocytopenia, hepatic dysfunction, and hyperglycemia without ketosis. Fasting blood glucose was 41 I mg/dl, and HbAlc was 14.5%. Blood ammonia was within normal levels. Cranial CT revealed no abnormalities. Brain MRI on T I-weighted images demonstrated bilateral high signal intensity in the putamen. An interictal EEG revealed a symmetrical slow background activity of 7,8 Hz. An ictal EEG recording showed a 2.5 4 Hz irregular sharp and slow wave discharge in the bilateral frontal-central regions. Treatment with carbamazepine was ineffective for the seizures. However, the seizures completely disappeared after the administration of insulin on March 17. Under good control of the hyperglycemia, the abnormal involuntary movements decreased gradually and then completely disappeared; the patient became neurologically asymptomatic by March 30. The follow-tip EEG demonstrated 9-Hz alpha background activity without any epileptic discharges. Conclusions: Nonketotic hyperglycemia has been rarely reported to cause stimulus-induced seizures or hyperkinetic involuntary movements such as hemichorea-ballism. To our knowledge, this is the first reported case of both induced seizures and involuntary movements simultaneously caused by hyperglycemia. Movement-induced seizures and choreoathetoid movements in this patient can be considered to result from transiently-increased activity in the basal ganglia and/or cerebral cortex associated with metaholic disorders. [source] Morphine modulation of temporomandibular joint-responsive units in superficial laminae at the spinomedullary junction in female rats depends on estrogen statusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2008A. Tashiro Abstract The influence of analgesic agents on neurons activated by stimulation of the temporomandibular joint (TMJ) region is not well defined. The spinomedullary junction [trigeminal subnucleus caudalis (Vc)/C1,2] is a major site of termination for TMJ sensory afferents. To determine whether estrogen status influences opioid-induced modulation of TMJ units, the classical opioid analgesic, morphine, was given to ovariectomized (OvX) rats and OvX rats treated for 2 days with low-dose (LE2) or high-dose (HE2) 17,-estradiol-3-benzoate. Under thiopental anesthesia, TMJ units in superficial and deep laminae at the Vc/C1,2 junction were activated by injection of ATP (1 mm) directly into the joint space. In superficial laminae, morphine inhibited evoked activity in units from OvX and LE2 rats in a dose-related and naloxone-reversible manner, whereas units from HE2 rats were not inhibited. By contrast, in deep laminae, morphine reduced TMJ-evoked unit activity similarly in all groups. Morphine reduced the background activity of units in superficial and deep laminae and resting arterial pressure similarly in all groups. Morphine applied to the dorsal surface of the Vc/C1,2 junction inhibited all units independently of E2 treatment. Quantitative polymerase chain reaction and immunoblots revealed a similar level of expression for ,-opioid receptors at the Vc/C1,2 junction in LE2 and HE2 rats. These results indicated that estrogen status differentially affected morphine modulation of TMJ unit activity in superficial, but not deep, laminae at the Vc/C1,2 junction in female rats. The site(s) for estrogen influence on morphine-induced modulation of TMJ unit activity was probably outside the medullary dorsal horn. [source] Noise-improved signal detection in cat primary visual cortex via a well-balanced stochastic resonance-like procedureEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Klaus Funke Abstract Adding noise to a weak signal can paradoxically improve signal detection, a process called ,stochastic resonance' (SR). In the visual system, noise might be introduced by the image jitter resulting from high-frequency eye movements, like eye microtremor and microsaccades. To test whether this kind of noise might be beneficial or detrimental for cortical signal detection, we performed single-unit recordings from area 17 of anaesthetized cats while jittering the visual stimulus in a frequency and amplitude range resembling the possible range of eye movements. We used weak, sub- and peri-threshold visual stimuli, on top of which we superimposed noise with variable jitter amplitude. In accordance with the typical SR effect, we found that small noise levels actually increased the signal-to-noise ratio (SNR) of previously weak cortical visual responses, while originally strong responses were little affected or even reduced. Above a certain noise level, the SNR dropped a little, but not as a result of increased background activity , as would be proposed by SR theory , but because of a lowered response to signal and noise. Therefore, it seems that the ascending visual pathway optimally utilizes signal detection improvement by a SR-like process, while at the same time preventing spurious noise-induced activity and keeping the SNR sufficiently high. [source] Homeostatic plasticity induced by chronic block of AMPA/kainate receptors modulates the generation of rhythmic bursting in rat spinal cord organotypic culturesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2001Micaela Galante Abstract Generation of spontaneous rhythmic activity is a distinct feature of developing spinal networks. We report that rat embryo organotypic spinal cultures contain the basic circuits responsible for pattern generation. In this preparation rhythmic activity can be recorded from ventral interneurons and is developmentally regulated. When chronically grown in the presence of an AMPA/kainate receptor blocker, this circuit expresses long-term plasticity consisting largely of increased frequency of fast synaptic activity and reduction in slow GABAergic events. We examined whether, once this form of homeostatic plasticity is established, the network could still exhibit rhythmicity with properties similar to controls. Control or chronically treated ventral interneurons spontaneously generated (with similar probability) irregular, network-driven bursts over a background of ongoing synaptic activity. In control cultures increasing network excitability by strychnine plus bicuculline, or by raising [K+]o, induced rapid-onset, regular rhythmic bursts. In treated cultures the same pharmacological block of Cl, -mediated transmission or high-K+ application also induced regular patterned activity, although significantly faster and, in the case of high K+, characterized by slow onset due to postsynaptic current summation. Enhancing GABAergic transmission by pentobarbital surprisingly accelerated the high-K+ rhythm of control cells (though depressing background activity), whereas it slowed it down in chronically treated cells. This contrasting effect of pentobarbital suggests that, to preserve bursting ability, chronic slices developed a distinct GABAergic inhibitory control on over-expressed bursting circuits. Conversely, in control slices GABAergic transmission depressed spontaneous activity but it facilitated bursting frequency. Thus, even after homeostatic rearrangement, developing mammalian spinal networks still generate rhythmic activity. [source] Radioguided Parathyroidectomy for Recurrent Hyperparathyroidism Caused by Forearm Graft Hyperplasia,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 5 2003Rebecca S Sippel Abstract One of the surgical options for symptomatic secondary hyperparathyroidism is a total parathyroidectomy with forearm implantation. Recurrence can occur and is most likely caused by hyperplasia of the small fragments of parathyroid tissue implanted in the forearm muscle. Forearm graft hyperplasia can be detected using Tc-99m sestamibi scanning of the forearm, which can show abnormal enhancement at the former graft site. In this report, we present the case of a 49-year-old gentleman with recurrent hyperparathyroidism caused by hyperplasia of forearm graft fragments. Unfortunately, no sutures or clips were placed at his initial surgery to identify the location of the parathyroid tissue in the forearm. Thus, we describe the first reported use of radioguided techniques using Tc-99m sestamibi injection and intraoperative gamma probe to localize parathyroid fragments in the forearm muscle. During our initial exploration, we found that injection of the tracer in the operative arm leads to prohibitively high levels of background activity. During a second exploration, the tracer was injected in the lower extremity, minimizing the background in the forearm and allowing the gamma probe to clearly identify two areas of abnormal parathyroid tissue. The intraoperative radioprobe allowed quick identification and removal of the abnormal parathyroid tissue in a case that was made particularly challenging by the absence of marking sutures. [source] Amplitude-integrated electroencephalographic changes in a newborn induced by overdose of morphine and corrected with naloxoneACTA PAEDIATRICA, Issue 1 2008HJ Niemarkt The amplitude-integrated electroencephalogram (aEEG) is a useful tool to assess brain function after perinatal asphyxia in term infants. We report a full-term newborn with moderate perinatal asphyxia, who accidentally received an overdose of morphine (5000 ,g/kg). The overdose of morphine resulted in a clear and immediate change of aEEG background activity from a continuous (C) to discontinuous (DC) background pattern. After administration of naloxone, the background activity restored immediately to continuous background pattern. The aEEG was used to monitor the stepwise reduction in continuous naloxone infusion. Conclusion: An overdose of morphine leads to clear and immediate changes in aEEG which restore after naloxone treatment. The aEEG can be used to monitor naloxone infusion. [source] | |||||||||||||