Results 1  10
of
24
The psychometric function: I. Fitting, sampling, and goodness of fit
, 2001
"... The psychometric function relates an observer’s performance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric funct ..."
Abstract

Cited by 219 (11 self)
 Add to MetaCart
The psychometric function relates an observer’s performance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function’s parameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximumlikelihood method of parameter estimation and developing several goodnessoffit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulusindependent errors (or lapses). We show that failure to account for this can lead to serious biases in estimates of the psychometric function’s parameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditional c 2 methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods. The performance of an observer on a psychophysical
Adaptive procedures in psychophysical research
 Percept. Psychophys
, 2001
"... As research on sensation and perception has grown more sophisticated during the last century, new adaptive methodologies have been developed to increase efficiency and reliability of measurement. An experimental procedure is said to be adaptive if the physical characteristics of the stimuli on each ..."
Abstract

Cited by 42 (0 self)
 Add to MetaCart
As research on sensation and perception has grown more sophisticated during the last century, new adaptive methodologies have been developed to increase efficiency and reliability of measurement. An experimental procedure is said to be adaptive if the physical characteristics of the stimuli on each trial are determined by the stimuli and responses that occurred in the previous trial or sequence of trials. In this paper, the general development of adaptive procedures is described, and three commonly used methods are reviewed. Typically, a threshold value is measured using these methods, and, in some cases, other characteristics of the psychometric function underlying perceptual performance, such as slope, may be developed. Results of simulations and experiments with human subjects are reviewed to evaluate the utility of these adaptive procedures and the special circumstances under which one might be superior to another.
LATERALIZATION DISCRIMINATION OF INTERAURAL TIME DELAYS IN FOURPULSE SEQUENCES IN ELECTRIC AND ACOUSTIC HEARING
, 2005
"... This study examined the sensitivity of four CI listeners to ITD in different portions of fourpulse sequences in lateralization discrimination. ITD was present either in all the pulses (referred to as condition Wave), the two middle pulses (Ongoing), the first pulse (Onset), the last pulse (Offset ..."
Abstract

Cited by 6 (0 self)
 Add to MetaCart
This study examined the sensitivity of four CI listeners to ITD in different portions of fourpulse sequences in lateralization discrimination. ITD was present either in all the pulses (referred to as condition Wave), the two middle pulses (Ongoing), the first pulse (Onset), the last pulse (Offset), or both the first and last pulse (Gating). All ITD conditions were tested at different pulse rates (100, 200, 400, and 800 pulses per second, pps). Also, five normal hearing (NH) subjects were tested, listening to an acoustic simulation of CI stimulation. All CI and NH listeners were sensitive in condition Gating at all pulse rates for which they showed sensitivity in condition Wave. The sensitivity in condition Onset increased with the pulse rate for three CI listeners as well as for all NH listeners. The performance in condition Ongoing varied over the subjects. One CI listener showed sensitivity up to 800 pps, two up to 400 pps, and one at 100 pps only. The group of NH listeners showed sensitivity up to 200 pps. The result that CI listeners detect ITD from the middle pulses of short trains indicates the relevance of fine timing of stimulation pulses in lateralization and therefore in CI stimulation strategies.
Colored motifs reveal computational building blocks in the C. elegans brain
 PLoS ONE
, 2011
"... Background: Complex networks can often be decomposed into less complex subnetworks whose structures can give hints about the functional organization of the network as a whole. However, these structural motifs can only tell one part of the functional story because in this analysis each node and edge ..."
Abstract

Cited by 4 (1 self)
 Add to MetaCart
(Show Context)
Background: Complex networks can often be decomposed into less complex subnetworks whose structures can give hints about the functional organization of the network as a whole. However, these structural motifs can only tell one part of the functional story because in this analysis each node and edge is treated on an equal footing. In real networks, two motifs that are topologically identical but whose nodes perform very different functions will play very different roles in the network. Methodology/Principal Findings: Here, we combine structural information derived from the topology of the neuronal network of the nematode C. elegans with information about the biological function of these nodes, thus coloring nodes by function. We discover that particular colorations of motifs are significantly more abundant in the worm brain than expected by chance, and have particular computational functions that emphasize the feedforward structure of information processing in the network, while evading feedback loops. Interneurons are strongly overrepresented among the common motifs, supporting the notion that these motifs process and transduce the information from the sensor neurons towards the muscles. Some of the most common motifs identified in the search for significant colored motifs play a crucial role in the system of neurons controlling the worm’s locomotion. Conclusions/Significance: The analysis of complex networks in terms of colored motifs combines two independent data sets to generate insight about these networks that cannot be obtained with either data set alone. The method is general
Problems of Measurement
"... Proposed measures of autonomic nervous system functioning within an individual were reviewed. An important factor in the choice of such measures is the recognition that the magnitude response to stimulation is influenced, to a large extent, by the state of the individual prior to stimulation. From ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
Proposed measures of autonomic nervous system functioning within an individual were reviewed. An important factor in the choice of such measures is the recognition that the magnitude response to stimulation is influenced, to a large extent, by the state of the individual prior to stimulation. From the point of view of informational content, there is little difference between the use of the magnitude change score and response level as the basic response datum when used in conjunction with the initial level. Consideration of the concept of the autonomic lability score as well as the mean response score reveals that neither measure adequately corrects nor compensates for the effect of prestimulus level. Several magnitude measures suggested for the comparison of individuals include the slope of the regression of change score on initial level, variability around this line, a measure of discriminability, and a measure of maximal reactivity. The temporal aspects of the autonomic response are discussed and, because of their lack of dependence on prestimulus level, two measures are extracted for each aspect—the mean and variability. 1 / UNDAMENTAL to many investigations in the field of psychophysiology is the ability to identify differences between individuals. This requires not only the appropriate instrumentation for the measurement of various autonomic re
An approach to combine the logistic threshold model of psychophysics with the Bradley–Terry–Luce models of choice theory
, 2005
"... ..."
The
"... scalp p brisk e study physio specify spatial interva ment o of the B Then t at the distrib Onset activit ment o and 1.5 the spa there w located proper tions C curren trode p signific and in the lat no sign cluded whom over m (0.6 to 0.5 s before movement onset), significant current sinks were found ..."
Abstract
 Add to MetaCart
scalp p brisk e study physio specify spatial interva ment o of the B Then t at the distrib Onset activit ment o and 1.5 the spa there w located proper tions C curren trode p signific and in the lat no sign cluded whom over m (0.6 to 0.5 s before movement onset), significant current sinks were found in 13 subjects in medial and in 10 subjec ered to in a m activat nizing Surfac specifi curren ture of and of a en ar in ely nc
Augmentation of Actinobacillus actinomycetemcomitans Invasion
, 2003
"... It has recently been shown that human salivary glands constitutively express CD14, an important molecule in innate immunity, and that a soluble form of CD14 is secreted in saliva. The concentration of CD14 in parotid (a serous gland) saliva was comparable to that in normal serum and 10fold the amou ..."
Abstract
 Add to MetaCart
(Show Context)
It has recently been shown that human salivary glands constitutively express CD14, an important molecule in innate immunity, and that a soluble form of CD14 is secreted in saliva. The concentration of CD14 in parotid (a serous gland) saliva was comparable to that in normal serum and 10fold the amount in whole saliva, although the physiological function of saliva CD14 remained unclear. Actinobacillus actinomycetemcomitans is a periodontopathic bacterium and is able to invade oral epithelial cells. The present study showed that upon exposure to live A. actinomycetemcomitans Y4 for 2 h, human oral epithelial HSC2 cells produced interleukin8 (IL8) for a further 24 h and whole saliva augmented the production induced by A. actinomycetemcomitans Y4. Parotid saliva showed a more pronounced effect on the production of IL8 than whole saliva. Neither saliva preparation itself had IL8inducing activity. Parotid saliva exhibited antibacterial activity against a low concentration of A. actinomycetemcomitans Y4, but recombinant CD14 did not show the activity. The internalization of A. actinomycetemcomitans Y4 into HSC2 cells was inhibited by cytochalasin B, indicating that the process was actin dependent, and depletion of CD14 from parotid saliva inhibited the invasion and, as a consequence, inhibited production of IL8. Furthermore, human recombinant CD14 augmented invasion and IL8 production. These results suggest that saliva CD14 promoted the invasion of oral epithelial cells by A.
PRIME POLYNOMIAL SEQUENCES
, 1976
"... Let F(x) be a polynomial with integral coefficients of degree d> _ 2 such that F(n)> _ 1 for all it 3 1. Let OF = {F(n)Í „ ,. Then F(tr) is called prime in OF if F(u) is not the product of strictly smaller terms of &F. It is proved that if F(x) is not of the form a(bx+c)d, then almost all ..."
Abstract
 Add to MetaCart
Let F(x) be a polynomial with integral coefficients of degree d> _ 2 such that F(n)> _ 1 for all it 3 1. Let OF = {F(n)Í „ ,. Then F(tr) is called prime in OF if F(u) is not the product of strictly smaller terms of &F. It is proved that if F(x) is not of the form a(bx+c)d, then almost all terms of (! r are prime in O F. Let 0 = be a sequence of positive integers. Then a,, E & is called composite in 0 if a „> I and a „ can be written as a product of terns a t c 0 with a; < a,,. If a „> 1 and a „ is not composite in 0, then a,, is called pritne in O. In this note we consider sequences of the form O F = {F(n);n 1, where F(x) is a polynomial with integral coefficients of degree d> 2 such that F(n)> I for all n> 1. We shall prove that if F(x) is not of the form F(x) = a(bx+c)'', then almost all terms of the sequence O F are prime in O F. Notation. Let F(x) be a polynomial with integral coefficients. Let p,(in) denote the number of solutions of the congruence F(n) = 0 (mod in) with I < ti < nz, and let 8F (in, x) denote the number of solutions of the congruence F(n) 0 (niod in) with I < n < x. The polynomial F(x) is (t+ 1)free if F(x) is not divisible by the (t+ I)st power of any nonconstant polynomial. We write f < g if I f (x) I < c lg(x) I for some constant c and all sufficiently large x. THEOREM. Let F(x) be a polynomial with integral coefficients of degree d y 2 such that F(n)> 1 for all it> I and such that F(x) is (t+1) free, where 1 < t < d1. Let OF = {F(n)),=, and let C(x) denote the number of F(n) in OF with it < x which are composite in O F. Then C(x) < x (d+I)Ad+2)+e_j x.(r/d)(2rld)+c for every e> 0. In particular, if F(.x) is nor a constant multiple of a linear polynomial, then 2) +f C(x) < x ' ( 11d.for every c> 0. We shall require the following result.