Compromised late-stage motion processing in schizophrenia.

BACKGROUND: Visual motion processing is compromised in schizophrenia, as shown in deficient velocity discrimination. Processing of motion signals comprises progressive stages along the geniculate-striate-extrastriate-cortex pathway. Based on neurophysiologic and brain lesion studies, a velocity discrimination deficit can implicate early-stage motion processing if it is contrast-dependent or late-stage motion processing if it is contrast-independent. METHODS: To determine which stage underlies the deficient velocity discrimination in schizophrenia, we examined the effects of visual contrast on velocity discrimination. We measured velocity discrimination thresholds in schizophrenia patients (n = 34) and normal control subjects (n = 17) at both low and high contrasts, using each subject's contrast detection threshold to equate contrast levels. RESULTS: Schizophrenia patients showed poor velocity discrimination that improved little with high contrast, whereas normal control subjects showed enhanced velocity discrimination with increased contrast. CONCLUSIONS: The finding that the velocity discrimination deficit in schizophrenia is independent of contrast modulation implicates the later, rather than the earlier, stages of motion processing, which is mediated in the extrastriate cortex.     

The Prospective Assessment of Autonomic Nerve Function by Pupillometry in Adolescents with Type 1 Diabetes Mellitus

The study aimed to compare the longitudinal assessment of autonomic nerve function by computerized infrared pupillometry and standard cardiovascular tests in adolescents with diabetes. Adolescents (n = 150) were assessed at two time points (T1 and T2). The median time interval between assessments was 1.5 (range 0.9–3) years. At T1 the median age was 14.5 (range 8.3–19.5) years and the median duration was 6.5 (range 1.1–16) years. The pupillary variables assessed included the resting pupil diameter, the maximum constriction velocity, and the reflex amplitude of constriction. Heart rate reflexes were assessed in response to deep breathing, the Valsalva manoeuvre, and on standing from a lying position (30/15 ratio). Between visits there was a significant decrease in maximum constriction velocity (6.0 mm s^?1 vs 6.3 mm s^?1, p = 0.0001) and resting pupil diameter (6.2 mm vs 6.3 mm, p = 0.001). At reassessment pupillary abnormalities increased from 32 (21 %) to 45 (30%), with 17 (54 %) of the initial abnormalities persisting. Adolescents with abnormally slow maximum constriction velocity compared to those with normal maximum constriction velocity had a higher glycated haemoglobin (HbA_1c%) at T2 (p = 0.02) and between assessments (p = 0.01). Cardiovascular test abnormalities did not increase between visits and the persistence of initial abnormalities was low (21 %). In summary, pupillometry appears a more sensitive test of autonomic nerve dysfunction in adolescents with diabetes than assessment of cardiovascular reflexes.     

Peak velocities of visually and nonvisually guided saccades in smooth-pursuit and saccadic tasks

 Smooth pursuit typically includes corrective catch-up saccades, but may also include such intrusive saccades away from the target as anticipatory or large overshooting saccades. We sought to differentiate catch-up from anticipatory and overshooting saccades by their peak velocities, to see whether the higher velocities of visually rather than nonvisually guided saccades in saccadic tasks may be found also in saccades in pursuit. In experiment 1, 12 subjects showed catch-up, anticipatory, and overshooting saccades to comprise 70.4% of all saccades in pursuit of periodic, 30°/s constant-velocity targets. Catch-up saccades were faster than the others. Saccadic tasks were run as well, on 19 subjects, including the 12 whose pursuit data were analyzed, with target-onset, target-remaining (saccade to the remaining target when the other three extinguish), and antisaccade tasks. For 17 of the 19 subjects, antisaccade velocities were lower than for either target-onset or target-remaining tasks. Velocities for the target-remaining task were near those for target onset, indicating that target presence, not its onset, defines visually guided saccades. Error and reaction-time data suggest greater cognitive difficulty for target remaining than for target onset, so that the cognitive difficulty of typical nonvisually guided saccade tasks is not sufficient to produce their lowered velocity. To produce reliably, in each subject, catch-up and anticipatory saccades with comparable amplitude distributions, nine new subjects were asked in experiment 2 to make intentional catch-up and anticipatory saccades in pursuit, and were presented with embedded target jumps to elicit catch-up saccades, all with periodic target trajectories of 15°/s and 30°/s. Velocities of intentional anticipatory saccades were lower than velocities of intentional catch-up saccades, while velocities of intentional and embedded catch-up saccades were similar. Target-onset and remembered-target saccadic tasks were run, showing the expected higher velocity for the target-onset task in each subject. Both experiments demonstrate higher peak velocities for catch-up saccades than for anticipatory saccades, suggesting that cortical structures preferentially involved in nonvisually guided saccades may initiate the anticipatory and overshooting saccades in pursuit. Received: 1 December 1995 / Accepted: 25 February 1997     

The CellSoft computerized semen analysis system: sperm image sizes and velocity measurements, and the consequences for internal running conditions

The CellSoft computer-assisted sperm analysis system was evaluated as to the optimal setting of three components of the internal running conditions. These 'set up' parameters were the lower setting for cell size range (PIXMIN), threshold velocity (MINVEL) and maximum velocity (MAXVEL). The decision for the PIXMIN setting was founded on observed sizes of sperm with low instant velocities combined with a study of the relationship between false positive observations for sperm and the PIXMIN setting. Our recommendation for this setting is three pixels. From the observation that 97.5% of immobilized sperm exhibit instant velocities of less than 15 microns sec-1, this is our proposal for the MINVEL setting. Correspondingly, the 97.5 percentile for instantaneous velocities in a population of some 14,000 cells (30 men with type 'a' motility, WHO) was 168 microns sec-1. We recommend that MAXVEL be set at this limit. Alternative settings for both MINVEL and MAXVEL are presented as some users may wish to apply other percentiles. From the above results a setting for PIXMAX at 25 pixels could be inferred. We recommend that these settings be applied in semen laboratories analysing human native samples at room temperature.     

彩色多普勒和磁共振对健康人颅内动脉影像学的比较研究

目的通过彩色多普勒和磁共振血管成像对健康人颅内动脉的检测,初步确定其操作规范及衡量标准。方法正常人200例,按照检查方法分为彩色多普勒血流显像(ColourDopplerFlowImaging,CDFI)组及磁共振血管成像(MagneticReso-nanceAngiography,MRA)组。CDFI组观察大脑中动脉(MiddleCerebralArtery,MCA)、椎动脉(VertebralArtery,VA)各段的血流动力学改变和相应点的血流束内径。MRA组检测相应血管对应部位的血管内径。结果同一条血管不同位置的血流速率有差异(P<0.05);同名血管相应位置的血流速率左侧略高于右侧,女组高于男组,但无统计学意义(P>0.05)。按年龄分组,相邻组间无显著性差异,相隔组间有显著性差异。CDFI所测血流束内径较MRA所测血管内径值偏高,且P<0.05,差异有显著性。结论a)应用CDFI能显示MCA,VA走行,可检测血管的血流动力学的改变。b)要提高临床脑血管疾病诊断的准确性,必须有规范的临床操作和可靠的检测指标。c)对血管内径的测量MRA更佳。     

Die dopplersonographische Bestimmung der maximalen Blutströmungsgeschwindigkeit in der Diagnostik peripherer arterieller Verschlußkrankheiten bei Diabetes mellitus

Summary Seventy-five diabetic and 40 nondiabetic subjects who where suffering from peripheral vascular disease were studied in order to determine whether the degree of the severity of their disease can be better calculated by Doppler ultrasound examinations of the peak velocity than by the systolic pressure of the peripheral bloodstream. In 46 examinations of normal controls the mean value of the peak velocity was 13.3±3.3 cm/s with a standard deviation of 15.4%±13.2% on one day and 16.1%±15.9% on different days. Considering patients with or without diabetes mellitus the velocity was significantly decreased in correlation to an increasing degree of severity of the vascular disease (P<0.001); however, the decrease was lower in diabetic than in nondiabetic subjects (6.9±2.8 vs 4.6±6.2,P<0.05). The systolic pressure hardly decreased, but remained higher in all stages of peripheral vascular disease of diabetics than in the nondiabetic subject (P<0.05 toP<0.005). There was a significant decrease of the systolic pressure only in diabetic subjects with the most advanced degree of the disease, i.e. stage IV (P<0.05).It is concluded from this study that Doppler ultrasound measurements of the peak velocity of the peripheral bloodstream are a useful parameter to calculate the degree of severity of the peripheral vascular disease. In addition, it is concluded than peak velocity is an even better prognostic indicator of peripheral vascular disease than is measurement of the systolic blood pressure at the feet.

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Abkürzungen AVK periphere arterielle Verschlußkrankheit - USDI Ultraschall-Doppler-Index - MSBG maximale Blutströmungsgeschwindigkeit - HFV Herzfrequenzvariation     

定量组织速度成像对右室起搏患者左室收缩运动的研究

目的　应用定量组织速度成像 (QTVI)评价右室心尖起搏 (RVAP)VVI型对左心收缩功能的影响。方法　应用GEVivid 7彩色多普勒超声显像仪对 2 0例RVAP患者和 2 0例正常人的心尖四腔切面的室间隔和左室外侧壁速度和位移曲线进行观察 ,测量心电图Q波分别至室间隔和左室外侧壁收缩期峰速度的时间 ,并除以R R间期进行校正。结果　QTVI显示右室起搏器置入者的室间隔与左室外侧壁速度曲线的收缩期S波非同步出现。Q波至室间隔收缩期峰速度的时间短于Q波至左室外侧壁收缩期峰速度的时间 ,两者分别为 ( 0 .12± 0 .0 2 )s和 ( 0 .14± 0 .0 2 )s,P <0 .0 5。结论　右室起搏后早期的左室整体收缩功能虽未见明显下降 ,但QTVI可以发现室间隔与左室壁收缩明显的不协调 ,可作为早期分析左室收缩运动的定量方法。     

Vertical profile of Cs in soil

In this paper, a vertical distribution of ¹³⁷Cs in undisturbed soil was investigated experimentally and theoretically. Soil samples were taken from the surroundings of the city of Kragujevac in central Serbia during spring-summer of 2001. The sampling locations were chosen in such a way that the influence of soil characteristics on depth distribution of ¹³⁷Cs in soil could be investigated. Activity of ¹³⁷Cs in soil samples was measured using a HpGe detector and multi-channel analyzer. Based on vertical distribution of ¹³⁷Cs in soil which was measured for each of 10 locations, the diffusion coefficient of ¹³⁷Cs in soil was determined. In the next half-century, ¹³⁷Cs will remain as the source of the exposure. Fifteen years after the Chernobyl accident, and more than 30 years after nuclear probes, the largest activity of ¹³⁷Cs is still within 10 cm of the upper layer of the soil. This result confirms that the penetration of ¹³⁷Cs in soil is a very slow process. Experimental results were compared with two different Green functions and no major differences were found between them. While both functions fit experimental data well in the upper layer of soil, the fitting is not so good in deeper layers. Although the curves obtained by these two functions are very close to each other, there are some differences in the values of parameters acquired by them.     

New ways of performing in vivo flow velocity measurements in the basilar artery

The basilar artery is the only large artery in which two flows merge, and this is reflected in the flow downstream. We report quantitative flow — velocity measurements with a phase-based MR technique, i.e. the Fourier velocity encoding method, in the basilar artery of a volunteer. To our knowledge, this has not previously been performed successfully. A comparison is made with the results of flow velocity measurements in the basilar artery with transcranial Doppler ultrasonography; the techniques agreed very well. Although Doppler ultrasonography is still most widely used, no information on the flow rate and the flow velocity distribution in the basilar artery can be provided. MR flow measurement techniques appear promising when detailed information on the flow velocity distribution and flow rate is needed.     

Reduction in Internal Carotid Arterial Blood Flow Velocity in Children During Antiepileptic Drug Therapy with Clinical Dosages

Summary: We studied the effect of antiepileptic drugs (AEDs) on internal carotid artery (ICA) blood flow velocity, as an index of total cerebral blood flow (CBF). The subjects were 45 newly diagnosed children with febrile convulsion or epilepsy who were seizure-free for a period long enough not to affect the results. They had no neurologic deficit, received fixed monotherapy, and were examined by a noninvasive Doppler ultrasound method, in comparisonwith 13 age-matched normal volunteers with no AED. In 30 patients, the measurements were performed before and after AED administration [10 with phenobarbital (PB), 10 with carbamazepine (CBZ), and 10 with valproate (VPA)], and performed before and after AED discontinuation in the remaining 15 patients (all with PB). Normal volunteers underwent the two consecutive examinations with a mean interval equal to that of the entire patient group, and there was no difference in velocity values between the measurements. In patients receiving CBZ or VPA, a significant reduction was noted in blood flow velocity after drug administration. Although velocity values in the patients receiving PB did not change after drug administration, they were significantly increased after complete discontinuation. In the present study, a slight but significant reduction in CBF caused by AED administration at therapeutic doses in children was suggested.