Convergence of occipital nerve and superior sagittal sinus input in the cervical spinal cord of the cat

Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches.     

AC/A ratios in myopic and emmetropic Hong Kong children and the effect of timolol§

Purpose: Caucasian children with myopia have elevated response accommodative vergence to accommodation (AC/A) ratios. The purpose of this study was twofold: to determine if response AC/A ratios vary with refractive error and with myopic progression rate in Hong Kong Chinese children, and to determine the effect of beta‐adrenergic antagonism with topical timolol application on AC/A ratios. Methods: Thirty children aged eight to 12 years participated in the study. All refractive errors were corrected with spectacle lenses. Accommodative responses were measured using a Shin‐Nippon autorefractor and concurrent changes in vergence were assessed using a vertical prism and a Howell‐Dwyer card at three metres and 0.33 metre. Accommodative demand was altered using plus or minus two dioptre lenses and lens‐ and distance‐induced response AC/A ratios were calculated. Measurements were repeated 30 minutes after the instillation of topical timolol maleate (0.5 per cent). Results: AC/A ratios appeared higher in progressing myopic children but the difference was not statistically significant. Timolol application reduced accommodative convergence (AC) in the stable myopes (reduction = ‐3 ± 1.14^A) but not in the emmetropes (0.69 ± 0.9^P) or progressing myopes (0.16 ± 0.43^A) and this difference between refractive groups was statistically s ignificant (F^2,27= 3.766; P= 0.036). However, timolol did not produce a significant change in the accommodative response to positive or negative lenses or response AC/A ratios. Conclusions: We did not find that AC/A ratios in myopic Chinese children were elevated and therefore, it is unlikely that elevated AC/A ratios are responsible for the high levels of myopia that occur in Hong Kong. The finding that timolol reduced AC in the stable myopes suggests that the autonomic control of accommodative convergence in these children may be different from that in emmetropic children and those with progressing myopia.     

Neural Correlates of the Results-of-Action Acceptor in a Functional Biotechnical Complex

This report presents data illustrating the neurophysiological features of efferent-afferent convergence on cortical neurons. During combination of stimulus of pyramidal tract axons with electrocutaneous reinforcement, some of the study neurons were found to change the parameters of their activity evoked by stimulation of this tract: evoked responses started to reproduce the structure of responses to the reinforcement. The most dynamic rearrangements of pyramidal tract responses were obtained in experiments in which the study neurons were included in a biotechnical complex with feedback, the complex consisting of neuron-computer-stimulator-animal and actually being an analog of a natural functional system. The role of efferent-afferent convergence on CNS neurons in the development of the results-of-action acceptor of a functional system for a voluntary behavioral act is discussed.     

Synaptic Connections of Different Strength Between Wind-sensitive Hairs and an Identified Projection Interneuron in the Locust

An identified intersegmental interneuron in Locusta and Schistocerca, with its cell body in the fourth abdominal ganglion and an axon which projects to the brain is excited by mechanosensory inputs from receptors on the head and neck. The organization of its receptive field, the types of sensory receptors which contribute to it and the patterns and strengths of the afferent connections were investigated by intracellular recording from the axon of the interneuron close to a spike-initiating site in the prothoracic ganglion. The receptive field of the interneuron consists of a small patch of hairs on the head ipsilateral to the axon, and from hairs on two regions of the prosternum (a cuticular structure on the ventral surface of the prothoracic segment), first an ipsilateral, lateral region and second a medial but contralateral region. Hairs on the pronotum (dorsal neck) also contribute but were not investigated here. Each spike in the afferent from a hair with a filiform appearance and with a pigmented base on the prosternum consistently evokes an EPSP in the interneuron. These have a short and constant latency, indicating that the connection is probably direct. The head hairs also appear to make direct connections with the interneuron in the prothoracic ganglion, so that the spike-initiating site here can integrate signals evoked by wind on the head and on the prosternum. Stiff tactile hairs on the prosternum do not connect with the interneuron. The EPSPs evoked by the long filiform hairs are consistently larger than those produced by the short filiform hairs and a single spike in some of the afferents from the long filiform hairs can evoke a spike in the interneuron. The effectiveness of an afferent is therefore correlated with the length of the filiform hair it innervates. The hairs with the most powerful effects are always the longest and occur in the same position on every locust. The shape of the receptive field and the different strengths of connections are apparent even in early larval instars. The axonal branches of the interneuron are restricted to the same side of the ganglion as the axon itself. Afferents from filiform hairs on the medial region of the prosternum project contralaterally, and those from the lateral region project ipsilaterally. Afferents from some of the head hairs project ipsilaterally directly to the prothoracic ganglion. The terminals of all these afferents overlap with the branches of the interneuron. By contrast, the afferents of tactile hairs which do not connect, project to different regions of neuropile. The connections ensure that the high sensitivity of the filiform hairs is maintained at the first stage in the central processing and suggest a role for this interneuron in supplying information about small changes in air currents that may be of use in controlling steering manoeuvres during flight.     

Subthalamic neuron activity related to tremor and movement in Parkinson's disease

Single cell activity recorded in the subthalamic nucleus (STN) of Parkinson's patients and the effect of tremor, passive and voluntary movement upon the same cells are described. Three types of cells were distinguished by the pattern of discharge: tonic, phasic and rhythmic. They all demonstrated high mean firing rates (65, 59 and 69 Hz, respectively). Simultaneous recordings of muscle activity and tremor helped in defining cell activity. The implantation of the definitive stimulating electrode in the patients was based on the number of STN cells related to tremor, active and passive movements (mean = 68%) along the track chosen. Cells were related to tremor (n = 21; 11%), modified the discharge with differences in the amplitude of tremor (n = 4), and changed the rate and pattern when tremor stopped spontaneously or artificially (n = 6). Movement-related cells (n = 97; 51%) showed a cyclic activity correlated with phases of the movement, or modified the firing rate along the performance of the movement. Tremor and movement-related cells (n = 11; 6%) revealed an interesting sensory-motor integrative function.     

再次LASIK治疗屈光回退和欠矫38例分析

目的　探讨再次准分子激光原位角膜磨镶术 (LASIK)矫治屈光回退和欠矫的疗效。方法　收集 2 0 0 0年 12月～2 0 0 2年 8月因屈光回退和欠矫在我院行再次LASIK者 3 8例 ( 70眼 ) ,随访 1年 ,观察术中术后并发症 ,术眼的屈光度。探讨再次LASIK的安全性、疗效及手术时机。结果　 3 8例 ( 70眼 )术中术后无不良并发症发生 ,术后 1年裸眼视力达术前最佳矫正视力者 68眼 ( 97 14 %) ,残余屈光度在± 1 0 0D以内者 69眼 ( 98 5 7%) ,术后 3月和 6月屈光度分别为 ( -0 3 5± 1 12 )D和( -0 5 2± 1 0 1)D ,术后 1年无角膜膨隆或圆锥角膜发生。结论　在保留角膜基质床的厚度≥ 2 5 0 μm的前提下行再次LASIK ,安全性及有效性均较理想     

单眼一退一缩术式矫正集合不足型间歇性外斜视短期效果分析

目的：观察一退一缩术式对集合不足型间歇性外斜视的效果和术后回退程度。

方法：对45例集合不足型间歇性外斜视患者由同一术者进行单眼一退一缩术式后,检查术后1d,2wk的斜视度,并进行统计分析。

结果：集合不足型间歇性外斜视患者45例进行单眼一退一缩术式后,术后1d,视远平均过矫8.27±7.17PD,视近平均过矫2.40±8.86PD,术后2wk视远平均欠矫1.18±6.98PD,视近平均欠矫4.36±7.83PD。术后2wk内,视远平均回退9.45±6.40PD,视近平均回退6.77±7.92PD。视远及视近回退呈正相关。术后2wk视远视近斜视度差异(3.18±5.60PD)较术前(7.65±6.55PD)明显减小,两者呈正相关。

结论：集合不足型间歇性外斜视患者适合一退一缩术式,适当加大内直肌手术量可减少术后远近斜视度的差异,且不改变患者内外直肌的张力状态。术后视远视近回退呈同步状态,视远约回退10PD,术后近期过矫10PD可有利于远期正位。     

Validation of the Proximal Isovelocity Surface Area Method for Assessing Mitral Regurgitation in Children

The proximal isovelocity surface area (PISA) method for calculating volume flow through the regurgitant orifice has attracted significant attention. A number of in vitro studies and clinical studies in adults suggest that the method is accurate. However, when applying the method to children it must be noted that the absolute regurgitation volume is small, and the range of body sizes is wide. This study investigated the accuracy of the PISA method for quantitative assessment of the severity of mitral regurgitation in children. Twenty children aged 7 months to 12 years (average 4.7 years) with mitral regurgitation but without interventricular shunt or aortic stenosis were selected for this study. Underlying cardiac diseases included atrioventricular septal defects in nine, isolated mitral regurgitation in five, and association with other heart defects in six. The PISA radius (r) and the duration of regurgitation (T) were measured on color M-mode recordings, with the M line passing through the center of the PISA. Assuming that the PISA is a hemisphere, maximal regurgitant flow rate (MFR: ml/s) was calculated as MFR = 2π×~ r ²×~ V (r= maximal radius, V= aliasing velocity), and regurgitant stroke volume (RSVpisa) as RSVpisa = 2π×~ MSR ×~ V×~ T (MSR = mean square of the PISA radius during regurgitation). As a validating standard, total stroke volume (TSV) using two-dimensional echocardiography determined by the area–length volumetry method and forward stroke volume (FSV) by the pulsed Doppler method were measured, and regurgitant stroke volume (RSV_D: RSV_D= TSV − FSV) and regurgitant fraction (RF: RF = RSV_D/TSV) were calculated. A linear correlation was found between MFR, RSVpisa, and RSV_D (X) (MFR = 4.2X + 54.0, r= 0.84. RSVpisa = 1.0X + 9.8, r= 0.90), and both RSVpisa and MFR divided by body surface area (BSA: m²) revealed a significant correlation with regurgitant fraction (X) by nonlinear regression analysis (RSVpisa/BSA = 26.2 ×~ X/(1 − X) + 16.8, r= 0.85. MFR/BSA = 121.8 ×~ X/(1 − X) + 92.2, r= 0.79). It is concluded that maximal regurgitant flow rate, regurgitant stroke volume, and regurgitant fraction can be accurately predicted in children using the PISA method by Doppler echocardiography.     

Convergence of Physics-Informed Neural Networks Applied to Linear Second-Order Elliptic Interface Problems

With the remarkable empirical success of neural networks across diversescientific disciplines, rigorous error and convergence analysis are also being developed and enriched. However, there has been little theoretical work focusing on neural networks in solving interface problems. In this paper, we perform a convergenceanalysis of physics-informed neural networks (PINNs) for solving second-order elliptic interface problems. Specifically, we consider PINNs with domain decompositiontechnologies and introduce gradient-enhanced strategies on the interfaces to deal withboundary and interface jump conditions. It is shown that the neural network sequenceobtained by minimizing a Lipschitz regularized loss function converges to the uniquesolution to the interface problem in $H^2$ as the number of samples increases. Numericalexperiments are provided to demonstrate our theoretical analysis.