Influence of pre-target cortical potentials on saccadic reaction times

 Saccades elicited by suddenly appearing targets show a broad distribution of reaction times. This may depend on variations in the subject’s state of preparation before target onset. To test this hypothesis, we recorded scalp event-related potentials from eight human subjects to investigate whether differences in saccadic reaction times (SRTs) are related to differences in cortical slow potentials prior to target onset. Compared with trials with medium SRTs (180–230 ms), trials with fast SRTs (130–180 ms) were found to be preceded by a more negative slow potential and trials with slow SRTs (230–280 ms) were found to be preceded by a more positive slow potential. These results support the hypothesis that cortical activation prior to target appearance influences SRTs. Received: 21 June 1996 / Accepted: 15 January 1997     

Three antidepressants (amitriptyline,dothiepin, fluoxetine), with and without alcohol,compared with placebo on tests of psychomotor ability related to car driving

Eight female volunteers received acute doses of amitriptyline 50 mg (AMI), dothiepin 50 mg (DOT), fluoxetine 40 mg (FLU) or placebo both with and without a ‘social’ dose of alcohol (ALC) equivalent to 0·5 g/kg body weight absolute alcohol. Performance on a variety of tests of psychomotor ability and cognitive function (critical flicker fusion, choice reaction time, tracking, Maddox Wing and simulated car steering) were performed at 1·5 and 4 hours following treatment. AMI and DOT both with and without ALC impaired performance on a range of tests at either or both 1·5 and 4 hours, although the effects of AMI and AMI + ALC were more widespread and severe than those found with either DOT or DOT + ALC. FLU and FLU + ALC showed no evidence of impairment on any test at either the 1·5 or the 4 hours assessments. The results suggest that there are differences between the experimental substances, at the doses used, in their intrinsic potential for impairing aspects of psychomotor performance and cognitive function.     

A dose–response study of total sleep time and the ability to maintain wakefulness

The apparent connection between sleep debt, performance decrements and workplace accidents has generated a need for feasible vigilance tests that focus on the quantification of daytime sleepiness in occupational settings. The objective of this study was to evaluate the sensitivity of the Maintenance of Wakefulness Test (MWT) to acute sleep deprivation of various doses. Eight healthy female volunteers, mean age 28.9 years (range 23–36), participated in this laboratory study. After an adaptation night, the subjects were assigned to four counterbalanced, randomly ordered night sleep conditions. These four conditions allowed for a time in bed (TIB) of 0, 2, 4 or 8 h, producing a total sleep time of 0, 113, 218 and 427 min, respectively. The ability to sustain wakefulness was measured after the TIB period at 11.00 and 17.00 hours by the MWT. Analysis of variance with repeated measures was used to study the dependence of MWT sleep latencies on the immediately prior TIB period. Both the latency of stage 1 sleep onset and the appearance of slow eye movements reduced significantly with increased sleep loss. The quantitative relationship between the previous total sleep time and the subsequent MWT sleep latencies followed an exponentially decaying function showing a high sensitivity to acute, severe night sleep loss but low sensitivity to less severe sleep restrictions. It is concluded that the MWT seems to be a sensitive method for the estimation of acute sleep deprivation. The test results appear, however, non-linearly related to the earlier sleep debt.     

Heart rate variability and apnea during sleep in Down's syndrome

Autonomic system dysfunction has been reported to occur frequently in patients with Down's syndrome (DS) and is constituted mainly by an imbalance between the sympathetic and vagal systems. The analysis of heart rate variability (HRV) during sleep is a quantitative reliable method for studying such a mechanism, but it has not yet been extensively and adequately applied in DS. In this study, HRV during sleep was evaluated in seven DS patients and in six normal controls, by also controlling for the presence of sleep apnea or arousal. The main results were an increased sympathetic function (low-frequency component of HRV) and a decreased vagal activity (high-frequency component of HRV) in DS with respect to normal controls, during apnea-free periods. Moreover, the presence of apnea, in DS, induced a further significant increase in low-frequency and very low-frequency components of HRV during sleep Stage 2. This study provides additional evidence of a brainstem dysfunctioning in DS, responsible for the abnormal imbalance between the sympathetic and vagal systems and confirms the brainstem involvement already suggested in the literature in order to explain brainstem-auditory evoked potential abnormalities and central sleep apnea in these patients.     

Management of infant sleep problems in a residential unit

Torrens House provides a short residential programme for families with a baby (8–12 months of age) identified by parents as having a sleep problem such as waking frequently at night and being difficult to settle. The programme involves the promotion of infant self-settling by the use of a controlled crying technique, together with wrapping, cessation of night feeds and establishment of a day-time routine. Twenty families (with 23 babies) were followed through the programme and for 3 months afterwards. There were significant decreases in the number of times the babies woke, the number of night-feeds and the length of time awake at night at 1 month follow-up, with a reduction in depressive symptomatology of the parents and a perceived improvement in their infants' behaviour. Twenty of the 23 babies were sleeping well at 3 month follow-up.     

Microstructure of the non-rapid eye movement sleep electroencephalogram in patients with newly diagnosed Parkinson's disease: effects of dopaminergic treatment.

We investigated non-rapid eye movement (non-REM) sleep in patients with newly diagnosed Parkinson's disease (PD) who had never previously received dopaminergic medication. There were no significant differences in the conventional sleep parameters between de novo patients with PD and a healthy control group, but the length of stage 1 sleep and the number of awakenings increased significantly upon administration of dopaminergic drugs. Analyzing the quantitative electroencephalogram (EEG), we observed a significant reduction in the low-delta frequency range and a nonsignificant increase in the sigma frequency range in de novo patients with PD. The dopaminergic medication also nonsignificantly reduced the low-delta and sigma frequencies, the latter to the level of the controls. Possible mechanisms that may account for the observed differences are discussed. It is suggested that Parkinson's disease as well as the application of dopaminergic drugs exerts a desynchronizing effect on the sleep EEG that is reflected in a disruption of sleep continuity.     

Intraoperative measurement of activated partial thromboplastin time and prothrombin time with a new compact monitor

A prospective study was conducted to evaluate a new compact portable coagulation monitor (Ciba–Corning Biotrack 512 Monitor), which enables the clinician to perform instantaneous activated partial thromboplastin time (APTT) and prothrombin time (PT). 126 patients scheduled for heparinized and nonheparinized vascular surgery, and gynaecological surgery, were included. A drop of capillary or venous whole blood was applied in disposable cartridges to successively perform APTT and PT, and the results of the tests were compared with conventional laboratory methods, performed in two different laboratories (Lab. A and B). Comparisons between Lab. A. and Lab. B. enables determination of the bias, precision, and percent of outliers (patients whose values differed more than 20%) in conventional methods. The reference value was defined as the mean of Lab. A. and Lab. B. values. For PT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias, the precision and the proportion of outliers. For APTT, there were no statistical differences between the capillary and venous samples performed with the portable monitor, and the reference value, for the bias and the precision. The percent of outliers, however, was significantly greater with the venous sample of the compact monitor than with the reference (48 versus 22%), and even if it did not reach the statistical significance ( P = 0.07) it was also higher with the capillary sample performed with the Ciba Monitor than with the reference (33%). In conclusion the assessment of blood coagulation using this new compact monitor could be of major interest during the intraoperative period when immediate results are mandatory, even if PT is more accurate than APTT with this new method.     

A method for partitioning cancer mortality trends by factors associated with diagnosis: An application to female breat cancer

U.S. cancer mortality data derived from information recorded on death certificates are frequently relied upon as an indicator of progress against cancer. A limitation of this measure is the lack of information pertaining to the onset of disease, such as year-of-diagnosis, age-at-diagnosis, stage of disease at diagnosis and histology of lesions. However, population-based cancer registries collect these types of data and allow the calculation of an incidence-file based mortality rate. This incidence-based mortality rate allows a partitioning of mortality by variables associated with the cancer onset. Breast cancer incidence-based mortality measures are created and compared to mortality rates based on death certificates over a comparable time period. Novel mortality measures, such as mortality rates by stage-at-diagnosis, age-at-diagnosis and year-of-diagnosis, are used to illustrate the value of this approach.     

Testosterone not associated with violent dreams or REM sleep behavior disorder in men with Parkinson's.

We examined the relationship between testosterone levels, violent dreams, and REM sleep behavior disorder (RBD) in 31 men with Parkinson's disease (PD): 12 with clinical RBD and 19 without. All PD patients with clinical RBD experienced violent dreams, but none of the 19 non-RBD patients reported violent dreams. While dream content appears to be more aggressive in PD patients with clinical RBD, the presence of violent dreams or clinical RBD is not associated with testosterone levels in men with PD.     

老龄者视觉运动反应时状态观察

通过对不同年龄段人群视觉运动反应时的测定，确认伴随增龄反应时明显呈梯度延长，而且与心电图ＳＴ－Ｔ改变以及甲皱微循环指标无明确的相关关系，视觉运动反应时具有独立地反映老上得衰老程度的生物标志意义。