Does the cerebellum contribute to specific aspects of attention?

We present data on attentional and neuropsychological functions of 16 patients with focal cerebellar lesions (13 tumours, 3 haematomas) compared to normative test data, and to 11 control subjects matched for age, gender, and years of education. Patients showed distinct deficits in qualitative aspects of a divided attention task, and in a working memory task. Performance in selective attention was unimpaired. The results support the concept that the cerebellum plays a role not only in motor, but also in higher cognitive functions. They are discussed on the basis of the idea that prediction and preparation are fundamental functions of the cerebellum. Therefore, the results confirm the idea that cerebellar lesions lead to reduced performance in specific attention tasks.     

Factors influencing the outcome after the operative treatment of cerebral aneurysms of anterior circulation

BACKGROUND: The influence of various factors on the outcome after the operative occlusion of the cerebral aneurysm was to be defined through the retrospective study on 111 surgically treated patients with aneurysm of anterior cerebral circulation. METHODS: Preoperative clinical condition was graded from 0 to V, according to Hunt & Hess. Postoperative outcome, defined as good or bad according to modified Glasgow Outcome Scale, was correlated in homogenous experimental groups with the following factors: gender, age, aneurysmal size, preoperative interval, nimodipine therapy, experience of surgical team and existence of chronic vascular diseases. RESULTS: Surgical outcome was good in 74.4% of males and 71.4% of females (p > 0.05); in 83.3% of patients with and 41.2% of patients without chronic diseases (p < 0.01); in 71.4% of patients underwent early, 83.3% of ones underwent postponed and 85% of those underwent late surgery (p > 0.05); in 81.5% of patients treated by nimodipine and in 41.7% of those untreated by the same drug (p < 0.01); in 78.9% of patients operated by the experienced surgical team and in 40% of those operated by less experienced surgical team (p < 0.01). In patients with both good and bad outcome, the mean age was 50.6 and 47.6 years (p > 0.05), and the mean aneurysmal size was 12.3 mm and 13.3 mm, respectively (p > 0.05). Before rupture, the mean size for aneurysms on the bifurcation of the middle cerebral artery was 14.3 mm, and for posterior communicating artery aneurysms only 9.7 mm (p < 0.05). CONCLUSION: Surgical outcome was significantly influenced by the existence of chronic diseases, nimodipine therapy and experience of surgical team, whereas gender, age, timing for surgery and aneurysmal size were not of significant influence.     

ECG changes in humans exposed to 50 Hz magnetic fields

Possible health issues of ELF EMFs include cardiovascular effects since both electrocardiogram and heart-rate changes have been reported in the literature. A non-linear relationship between field strength and biological response has been reported in some studies. In this study, a total of 59 subjects, divided into three independent magnetic field strength groups, were compared. A calculated 12-hour time weighted average (TWA) value of the fields was used as an exposure metric for each of the three locations ("low": 0.067 muT, "medium": 1.18 muT and "high": 5.2 muT) and subsequently used to estimate workers' exposure at these sites. Electrocardiograms were recorded in the resting position. Five parameters were derived from the ECG: heart rate (HR), duration of P wave and QRS wave, and duration of PR and QT intervals. The QT intervals were normalized to a heart rate of 60 (QTc). The obtained data were analyzed first by means of multivariate analysis of covariance and then oneway univariate analyses of covariances (ANCOVA) using exposure duration as a covariate. Only the ANCOVA on the QTc interval was significant. Our results suggest that the relationship between field strength and response is non-linear: the adjusted mean QTc values are similar between the "low" and the "high" group, but significantly lower in the "medium" group. One possible interpretation of our results is that a specific exposure pattern might be responsible for the non-linear effects observed, so that generally, characterizing exposure to electric and magnetic fields using simple metrics such as TWA may be insufficient.     

Semi-chronic motorized microdrive and control algorithm for autonomously isolating and maintaining optimal extracellular action potentials

A system was developed that can autonomously position recording electrodes to isolate and maintain optimal quality extracellular signals. The system consists of a novel motorized miniature recording microdrive and a control algorithm. The microdrive was designed for chronic operation and can independently position four glass-coated Pt-Ir electrodes with micrometer precision over a 5-mm range using small (3 mm diam) piezoelectric linear actuators. The autonomous positioning algorithm is designed to detect, align, and cluster action potentials and then command the microdrive to optimize and maintain the neural signal. This system is shown to be capable of autonomous operation in monkey cortical tissue.     

Electrical synapse formation disrupts calcium-dependent exocytosis, but not vesicle mobilization

Electrical coupling exists prior to the onset of chemical connectivity at many developing and regenerating synapses. At cholinergic synapses in vitro, trophic factors facilitated the formation of electrical synapses and interfered with functional neurotransmitter release in response to photolytic elevations of intracellular calcium. In contrast, neurons lacking trophic factor induction and electrical coupling possessed flash-evoked transmitter release. Changes in cytosolic calcium and postsynaptic responsiveness to acetylcholine were not affected by electrical coupling. These data indicate that transient electrical synapse formation delayed chemical synaptic transmission by imposing a functional block between the accumulation of presynaptic calcium and synchronized, vesicular release. Despite the inability to release neurotransmitter, neurons that had possessed strong electrical coupling recruited secretory vesicles to sites of synaptic contact. These results suggest that the mechanism by which neurotransmission is disrupted during electrical synapse formation is downstream of both calcium influx and synaptic vesicle mobilization. Therefore, electrical synaptogenesis may inhibit synaptic vesicles from acquiring a readily releasable state. We hypothesize that gap junctions might negatively interact with exocytotic processes, thereby diminishing chemical neurotransmission.     

Melatonin modulates intercellular communication among cultured chick astrocytes

Melatonin, a pineal neurohormone, mediates circadian and seasonal processes in birds and mammals. Diencephalic astrocytes are sites of action, at least in birds, since they express melatonin receptors and melatonin affects their metabolism. We tested whether astrocytic calcium waves are also modulated by melatonin. Calcium waves, which we found to be regulated in cultured chick glial cells by an IP(3)-dependent mechanism, were potentiated by physiological concentrations of melatonin. Melatonin also increased resting calcium levels and reduced gap junctional coupling among astrocytes, at concentrations that facilitated calcium waves. These modulatory effects were diminished by melatonin receptor blockade and pertussis toxin (PTX). Thus, melatonin induced a functional shift in the mode of intercellular communication, between junctional coupling and calcium waves, among glial cells. We suggest a mechanism where neuroglial physiology, involving GTP-binding protein signaling pathways, links rhythmic circadian outputs to pervasive neurobehavioral states.     

Effects of circumferential rigid wrist orthoses in rehabilitation of patients with radius fracture at typical site

BACKGROUND: The use of orthoses is a questionable rehabilitation method for patients with the distal radius fracture at typical site. The aim of this study was to compare the effects of the rehabilitation on patients with radius fracture at the typical site, who wore circumferential static wrist orthoses, with those who did not wear them. METHODS: Thirty patients were divided into 3 equal groups, 2 experimental groups, and 1 control group. The patients in the experimental groups were given the rehabilitation program of wearing serially manufactured (off-the-shelf), as well as custom-fit orthoses. Those in the control group did not wear wrist orthoses. Evaluation parameters were pain, edema, the range of the wrist motion, the quality of cylindrical, spherical, and pinch-spherical grasp, the strength of pinch and hand grasp, and patient's assessment of the effects of rehabilitation. RESULTS: No significant difference in the effects of rehabilitation on the patients in experimental groups as opposed to control group was found. Patients in the first experimental group, and in control group were more satisfied with the effects of rehabilitation, as opposed to the patients in the second experimental group (p<0.05). CONCLUSION: The effects of circumferential static wrist orthoses in the rehabilitation of patients with distal radius fracture at the typical site were not clinically significant. There was no significant difference between the custom and off-the-shelf orthoses.