Span of attention,backward masking,and reaction time

A test pattern consisting of 0 to 15 dots and a following random dot masking pattern were presented for 5 msec each with SOAs varying between 30 and 200 msec. The subject was asked to report the perceived number of dots in the test pattern as soon as possible and to assign a confidence rating to each report. The span of attention (upper limit for 50% correct numerosity judgments) increased from 2.4 to 9.5 as the SOA increased. Backward masking reduced the reported number of dots from the actual number in the test pattern, especially with small SOAs. Reaction time increased linearly at a low rate (approximately 40 msec/dot) up to 4 dots in the test pattern and then increased linearly at a high rate (approximately 370 msec/dot) as thereported, orperceived, number of dots increased. The two different branches of the reaction time curve were considered to represent two separate processes,subitizing andcounting, as suggested by Klahr (1973), who found similar dual increase rates as a function of the actual number of dots. These findings, as well as causal inference based on partial correlations and path analysis, indicated that the reported (perceived) number of dots and confidence rating were both determined by the number of stimulus dots and the SOA and that the reaction time was determined by the so-determined perceived number of dots and level of confidence. A multistage model is proposed.     

Relations among premorbid weight,referral weight,and psychological test scores for patients with anorexia nervosa

The purpose of this study was to test the hypothesis that, in anorexia nervosa, patients with a low premorbid weight are associated with a low weight at referral and that premorbid weight, referral weight, and weight loss are associated with mood states. The changes of Body Mass Index from premorbid to referral, the duration of illness, and the psychological scores on the Profile of Mood States and the Cornell Medical Index-Health Questionnaire were examined in 49 anorexia nervous patients. Body Mass Index at referral of patients with lower premorbid Body Mass Index was significantly lower than that of patients with higher premorbid level. For patients with a larger relative decrease, scores on depressive mood were lower. These findings suggested that in anorexia nervosa patients, lower premorbid Body Mass Index was associated with lower Body Mass Index at referral, and that the patients with higher relative decrease in Body Mass Index might be satisfied with their weight loss.     

Effects of voluntary activation on neuromuscular endurance analyzed by surface electromyography

The purpose was to examine the relation between voluntary muscle activation and neuromuscular endurance of individual subjects based on the pattern of surface electromyography (EMG). The voluntary muscle activation was estimated from the relation between voluntary force and tetanic force superimposed on the voluntary force (twitch interpolation technique). 14 male subjects (10 regular exercisers and 4 sedentary; 21-29 years old) were divided into a High Voluntary Activation group and a Low Voluntary Activation group. A significant positive correlation of .72 (p<.01) was found between maximum voluntary torque and voluntary activation. A fatigue test was conducted during isometric contractions of 60% and 20% maximum voluntary torque. The endurance time was significantly longer for the Low Voluntary Activation group than the High Voluntary Activation group. The mean power frequency of voluntary EMG obtained from the vastus lateralis muscle decreased consistently whereas the average rectified value increased. The final change of mean power frequency relative to the initial value was significantly greater in the 60% Fatigue task than in the 20% Fatigue task. For the 60% Fatigue task, the final change of mean power frequency and average rectified value relative to the initial value was significantly greater in the Low Voluntary Activation group than in the High Voluntary Activation group. These results suggest that the individual differences in voluntary activation determine the neuromuscular performance usually evaluated as maximum voluntary torque and endurance time and that the voluntary activation may depend on the daily exercise.     

Principal component analysis with external information on both subjects and variables

A method for structural analysis of multivariate data is proposed that combines features of regression analysis and principal component analysis. In this method, the original data are first decomposed into several components according to external information. The components are then subjected to principal component analysis to explore structures within the components. It is shown that this requires the generalized singular value decomposition of a matrix with certain metric matrices. The numerical method based on the QR decomposition is described, which simplifies the computation considerably. The proposed method includes a number of interesting special cases, whose relations to existing methods are discussed. Examples are given to demonstrate practical uses of the method.The work reported in this paper was supported by grant A6394 from the Natural Sciences and Engineering Research Council of Canada to the first author. Thanks are due to Jim Ramsay, Haruo Yanai, Henk Kiers, and Shizuhiko Nishisato for their insightful comments on earlier versions of this paper. Jim Ramsay, in particular, suggested the use of the QR decomposition, which simplified the presentation of the paper considerably.     

Ideal point discriminant analysis

A new method of multiple discriminant analysis was developed that allows a mixture of continuous and discrete predictors. The method can be justified under a wide class of distributional assumptions on the predictor variables. The method can also handle three different sampling situations, conditional, joint and separate. In this method both subjects (cases or any other sampling units) and criterion groups are represented as points in a multidimensional euclidean space. The probability of a particular subject belonging to a particular criterion group is stated as a decreasing function of the distance between the corresponding points. A maximum likelihood estimation procedure was developed and implemented in the form of a FORTRAN program. Detailed analyses of two real data sets were reported to demonstrate various advantages of the proposed method. These advantages mostly derive from model evaluation capabilities based on the Akaike Information Criterion (AIC).The work reported in this paper has been supported by Grant A6394 from the Natural Sciences and Engineering Research Council of Canada and by a leave grant from the Social Sciences and Humanities Research Council of Canada to the first author. Portions of this study were conducted while the first author was at the Institute of Statistical Mathematics in Tokyo on leave from McGill University. He would like to express his gratitude to members of the Institute for their hospitality. Thanks are also due to T. Komazawa at the Institute for letting us use his data, to W. J. Krzanowski at the University of Reading for providing us with Armitage, McPherson, and Copas' data, and to Don Ramirez, Jim Ramsay and Stan Sclove for their helpful comments on an earlier draft of this paper.     

An analysis of tactile letter confusions

A confusion matrix of the whole block capital letters of the alphabet was obtained so as to examine the nature of tactile letter recognition, using a 17 by 17 matrix of tactile stimulators placed against blind subjects’ backs. A hierarchical cluster analysis and a nonmetric multidimensional scaling technique were applied to the matrix. The results of the two analyses were consistent with each other and indicated that at least three independent basic letter features—enclosing shapes, vertical parallel lines, andangle of lines—play important parts in tactile letter recognition. Most confusion may be attributable to displacement of the apparent loci, omission or fusion of loci of stimulation, and failure to detect gaps in the tactile letters.     

A quantitative near-infrared spectroscopy study: a decrease in cerebral hemoglobin oxygenation in Alzheimer's disease and mild cognitive impairment

A newly developed quantitative near-infrared spectroscopy (NIRS) system was used to measure changes in cortical hemoglobin oxygenation during the Verbal Fluency Task in 32 healthy controls, 15 subjects with mild cognitive impairment (MCI), and 15 patients with Alzheimer's disease (AD). The amplitude of changes in the waveform, which was quantitatively calculated by a signal processing method, was significantly lower in the frontal, and the bilateral parietal areas in the AD group, whereas that in the MCI group was significantly lower only in the right parietal area. The NIRS system may be a potential tool for the primary screening of AD.     

Involvement of IP3 receptors in LTP and LTD induction in guinea pig hippocampal CA1 neurons

The role of inositol 1, 4, 5-trisphosphate receptors (IP3Rs) in long-term potentiation (LTP) and long-term depression (LTD) was studied in CA1 neurons in guinea pig hippocampal slices. In standard solution, short tetanic stimulation consisting of 15 pulses at 100 Hz induced LTP, while three short trains of low-frequency stimulation (LFS; 200 pulses at 1 Hz) at 18-min intervals or one long train of LFS (1000 pulses at 1 Hz) induced stable LTD in both the slope of the field EPSP (S-EPSP) and the amplitude of the population spike (A-PS). Bath application of 2-aminoethoxydiphenyl borate (2-APB), an IP3R antagonist, or of alpha-methyl-4-carboxyphenylglycine (MCPG), a wide-spectrum metabotropic glutamate receptor antagonist, during weak tetanic stimulation significantly increased the magnitude of the LTP in both the S-EPSP and A-PS. Three short trains of LFS or one long train of LFS delivered in the presence of 2-APB or MCPG did not induce LTD, but elicited LTP. Based on these results, we conclude that, in hippocampal CA1 neurons, IP3Rs play an important role in synaptic plasticity by attenuating LTP and facilitating LTD.     

Qi and phenomenology of wind

Continental Philosophy Review -