Event-Related Potential Correlates of Two Stages of Information Processing in Physical and Semantic Discrimination Tasks

Event-related potentials were studied while subjects performed physical and semantic discrimination tasks. Two negative components, N_A and N2, were observed in both kinds of discriminations. The earlier component, N_A, had a constant onset latency, but its peak latency varied as a function of stimulus complexity. N2 latency varied in relation to changes in the peak of N_A. RT and P3 followed N2 by similar amounts of time across tasks. The N_A and N2 components were interpreted as reflecting partially overlapping sequential stages of processing associated with pattern recognition and stimulus classification, respectively.     

A Parametric Approach to Measuring Cerebral Blood Flow Autoregulation from Spontaneous Variations in Blood Pressure

Autoregulation maintains cerebral blood flow (CBF) almost constant in the face of changes in arterial blood pressure (ABP). Tests for impairment of this process using only spontaneous fluctuations in ABP, without provoking large variations, are of great clinical interest, and a range of different approaches have previously been applied. Extending earlier work based on linear filters, we propose a simple parametric method using a first order finite impulse response filter. We evaluate the method on ABP and CBF velocity [(CBFV), from trancranial Doppler ultrasound] signals collected in 60 patients with stenosis or occlusion of the carotid arteries. Data were collected during the inspiration of ambient air, a 5% CO2/air mixture, and finally the return to ambient air. Equivalent data were collected in 15 normal subjects. The filters estimated from the data segments with constant inspiratory pCO2 showed the expected high-pass characteristic, which was reduced during hypercapnia and also in patients. Highly significant correlation between the filter parameters and cerebrovascular reactivity (percent increase in CBFV per unit change in end-tidal pCO2) gives further evidence that the filters reflect autoregulation. The method allows simple parametrization of the dynamic autoregulatory responses in CBFV, and the analysis of short (1 min) data segments. © 2001 Biomedical Engineering Society. PAC01: 8719Uv, 4762+q, 4380Qf     

Reduced visuospatial performance in children with the D2 dopamine receptor A1 allele

Previous studies suggest a reduced dopaminergic function in subjects with the A1 (minor) allele of the D2 dopamine receptor (DRD2) gene. To explore influences on visuospatial ability as a function of the DRD2 gene, 182 alcohol- and other drug-naive sons (age 10–14) of active alcoholic, recovered alcoholic, and nonalcoholic fathers were administered a visuospatial task (Benton's Judgment of Line Orientation Test) which makes minimal motoric/verbal demands. Visuospatial scores were lower for boys with the A1 allele and for sons of active alcoholics. A1-allele boys made more errors than A2 boys on all 11 of the template lines, with the effect being largest for the rightmost presentations. In contrast, the effect of family history for alcoholism was strongest on both right and left midquadrant presentations. Moreover, separate analyses of the two types of errors produced allele but not family history of alcoholism effects when the two lines were misjudged as farther apart than they actually were and family history but not allele effects where the two lines were misjudged as closer together. These results suggest that polymorphism of the DRD2 gene and family history of alcoholism are dissociable determinants of visuospatial ability and that visuospatial defects previously observed in alcoholics may, in part, be antecedent to their drinking behavior.     

Electrodermal Lability and Visual Information Processing

Individual differences in electrodermal lability have been related to performance in vigilance and reaction time tasks. The goal of the present study was to employ an "additive factors" approach to identify the stages of information processing that might underlie these effects. Nineteen labile and 17 stabile subjects performed a choice reaction time task in which a visual imperative stimulus was presented under two conditions of intensity (presumed to affect the speed of pre-processing operations) X three conditions of degradation (which influences later encoding processes related to feature extraction). Measures of both reaction time and movement time were obtained. The major findings were: (a) labile subjects had faster reaction times than stabiles, and (b) lability interacted significantly with stimulus degradation. Labiles also tended (p less than .10) to have faster movement times. This pattern indicates that labiles and stabiles differ in the performance of later encoding operations, and possibly in the speed of motor processes as well. However, they do not appear to differ in the early pre-processing of the simple physical attributes of a stimulus.     

New algorithmic-based digital filter processing system for real-time continuous blood pressure measurement and analysis in conscious rats

A new algorithmic-based digital filter processing system for real-time continuous blood pressure (BP) measurement and analysis in freely-moving conscious rats has been developed. Real-time recognition of BP waveforms, real-time noise rejection and determination of representative waveform indexes (WIs) at indicated time points using digital filters and Smirnov's rejection test were realized with this system. Digital filters were applied for two different purposes: waveform segmentation and smoothing the calculations of representative WIs. Smirnov's rejection test was used for real-time noise rejection and yielded an accurate rejection rate of 99.99%. The result was that the digital filter processing and Smirnov's rejection test realized accurate real-time BP measurement and analysis in freely-moving conscious rats using a personal computer.     

How to Optimize Radiological Images Captured from Digital Cameras, Using the Adobe Photoshop 6.0 Program

Over the past decade, the technology that permits images to be digitized and the reduction in the cost of digital equipment allows quick digital transfer of any conventional radiological film. Images then can be transferred to a personal computer, and several software programs are available that can manipulate their digital appearance. In this article, the fundamentals of digital imaging are discussed, as well as the wide variety of optional adjustments that the Adobe Photoshop 6.0 (Adobe Systems, San Jose, CA) program can offer to present radiological images with satisfactory digital imaging quality.     

Electronic data processing in the Danish Cytogenetic Central Register and EDP problems of registers in general

A brief introduction to the Danish Cytogenetic Central Register (DCCR) is given, and possibilities, principles and problems concerning the establishment and maintenance of a national cytogenetic register are presented.
Various data carrier media for registers in general are discussed, of which the magnetic disc is considered most appropriate. General principles for programs capable of performing insertions, deletions and other modifications in the data base are outlined as well as the principles for the programs in the DCCR.
The individual records should preferably be identified by aid of a central person registration number (CPR) rather than by name. The data should be stored and sorted by this identification in order to facilitate retrieval of a desired record. The structure of the records is discussed with regard to prevention of the occurrence of certain errors as well as the optimization of processing.
Flexibility and economy of space are achieved by using programs able to handle records of unequal length, and problems occurring in connection with this are discussed. The question of how to protect sensitive data is dealt with, and two different methods used in the DCCR are outlined. Programs capable of analyzing karyotypes with the purpose of recognizing various cytogenetic syndromes have been developed for use in the DCCR. Various examples of computing times of typical program runs are presented.     

New image-processing system for analysis,display and measurement of static and dynamic foot pressures

A new image-processing system, using a video digitiser with an IBM-compatible PC/AT, is developed for acquisition and processing of low-contrast, lowintensity barographic images of both feet for assessment of pressure distribution during standing and walking. Data displays, in the form of centres of pressures, isopressures contours, perspective views of pressures, grey scale image and walking pressure patterns, combined image of walking pressures, paths of centres of pressures and pressure variations with time, are developed. These have provided very useful and early information regarding the internal structural changes in the bones of the foot and sites at risk of ulcer development in leprosy subjects and enable suitable corrective orthopaedic procedures to be adopted. unitl the end of November 1990, and will then return to the Indian Institute of Technology.