Psychophysical Analysis Research Articles

Temporal summation of heat pain: A psychophysical analysis

Temporal summation of heat pain: A psychophysical analysis

Comparison of Gradation Characteristics between Three Typical Medical Imaging Display Devices Using Psychophysical Analysis

Although there are remarkable differences in maximum luminance in cathode ray tube (CRT) and liquid crystal display (LCD) monitors and film/viewer systems, these differences cannot be recognized in our perception of them. To clarify the reason for this conflict, we analyzed the psychophysical gradient (delta), which is based on the minimum perceptible luminance difference (DeltaL(min)) and can express contrast visually recognized by observers. In this study, we first confirmed the compatibility of the psychophysical analysis to the CRT and the LCD monitors by using their threshold contrasts (C(t)s). Second, we calculated and compared the delta's of the above output devices. The C(t)s values of each device were in good agreement. Moreover, the Moon & Spencer model, which expressed the perceptibility of luminance change, was well suited to the measured C(t)s over the whole luminance range. The psychophysical analysis is therefore available not only for the film/viewer system, but also for the CRT and LCD systems. The difference of physical gradient G of the luminance characteristics curve among the output devices was larger than 20 times, whereas that of d was within 3 times. The display devices listed in the order of decreasing delta were film/viewer>LCD>CRT. These results corresponded to the visual contrast sensation and our clinical experience, which cannot recognize remarkable differences in perception. By using the psychophysical analysis, we clarified the reason for the conflict between the results of physical evaluation and the contrast visually recognized by observers.

Psychophysical and Tractarian Analysis

This paper argues for a physicalistic interpretation of Wittgenstein's Tractatus Logico-Philosophicus. Wittgenstein's general conception of world and language analysis is interpreted and exemplified in relation to the historical background of the psychophysical analysis of sense data and, in particular, color analysis. Three of his main principles of analysis—the principle of independence, the context principle and the principle of atomism—are interpreted and justified on the background of physicalism. From his proof of color exclusion in the Tractatus, it is shown that Wittgenstein had a detailed conception of how philosophy should fulfil the task of distinguishing between sense and nonsense using physicalistic presuppositions.

An irrelevant light enhances auditory detection in humans: a psychophysical analysis of multisensory integration in stimulus detection

Physiological and behavioral studies in animal models have revealed that information from the different senses can be used synergistically to enhance the detection of objects and events. Although a great deal of evidence exists which demonstrates the synergistic use of multisensory cues in human behavior and perception, there is conflicting evidence about whether such interactions can be used to aid in stimulus detection. To examine this issue, we had volunteers indicate the presence or absence of a brief, low-intensity sound that was either presented alone or paired with a simultaneous light in a one-interval signal detection task. In the first experiment, the task-irrelevant light was found to enhance the detectability of the sound, but also to increase the subject’s willingness to report the presence of a sound (i.e., response bias). In the second experiment, designed to eliminate this response bias, we found an improvement in stimulus detectability in the absence of any change in bias. These findings demonstrate the presence of a significant multisensory-mediated gain in stimulus detection in human subjects.

Reproducibility of human brain activity following repeated oesophageal stimulation

S. J. Coen, L. J. Gregory, L. Yaguez, D. Hall, E. Amaro, S. Smale, S. C. Williams, D. G. Thompson, Q. Aziz Institute of Psychiatry, London, United Kingdom, University of Manchester, Manchester, United Kingdom, Kings College Hospital, London, United Kingdom Synopsis Despite the recent growth in studies on the central processing of visceral sensations, the test-retest reliability of the neural correlates of visceral sensation remain unclear. In order to test the variance between scan sessions, at the group level, volunteers underwent a modified box-car functional magnetic resonance imaging (fMRI) experiment, involving periods of non-painful and painful oesophageal stimulation on three separate occasions. Painful stimulation produced robust activation in many cerebral regions previously associated with visceral processing. Non-painful stimulation activated a similar network but showed greater variability between scans. Introduction Previous studies have identified various cerebral regions involved in the processing of visceral sensations (1). It is often assumed that activations obtained during these studies are inherently reliable, and therefore the conclusions drawn are based on this assumption. In fact, the cerebral activation during fMRI sessions can be influenced by many variables including scanner noise, subject movement and cognition, such as habituation, attention and learning. While the cerebral processing of visceral sensation has been studied, information regarding test-retest reliability of fMRI studies applied to this area of research remains unclear. Aims: The purpose of this study was to assess the reproducibility of the neural correlates of oesophageal sensation, using fMRI. Methods Subjects: 7 healthy volunteers (5 male, mean age 22 years, +7 months) participated in the study. All subjects gave informed, written consent prior to intubation and scanning. The study was approved by the local ethics committee for research. Oesophageal stimulation: a standard manometry catheter with a silicone balloon attached was passed trans-nasally into the lower oesophagus (35cm from the nostril). The catheter was attached to a pump that inflated the balloon with air at regular intervals. The experiment examined two conditions; non-painful, (50% of the difference between sensory and pain thresholds), and painful (pain threshold) stimulation intensities, using phasic balloon distension in the distal oesophagus. The order of presentation of these intensities was counterbalanced across scans. A modified block design was employed for each intensity, where “active” and “rest” phases were repeated five times. Behavioural data measuring the subjective perception of the stimulus (0 = non-painful, 5 = discomfort, 10 = extreme pain) were also acquired after each active epoch, using visual analogue scales (VAS). This experimental procedure was repeated on two additional occasions (three scans in total) to investigate the consistency of cerebral activation over time. fMRI acquisition: Functional Magnetic Resonance Imaging was performed using a GE Neuro-optimised 1.5 Tesla system (General Electric, Milwaukee WI, USA), based at the Maudsley Hospital, London. Sixteen 7mm slices (0.7 mm gap) parallel to the bicomissural plane were acquired, with a repetition time (TR) of 3 seconds and an echo time (TE) of 40ms, flip angle 90o. A total of 122 T2* weighted images per slice, depicting BOLD contrast (Ogawa et al, 1990) were collected over a six minute and six second period of continuous acquisition during which, subjects received localised phasic distensions to the oesophagus. Image Analysis: Spatially realigned BOLD responses were modelled as the weighted sum of the input function convolved with two Poisson functions. A goodness of fit statistic was computed and a voxel-wise inference was carried out non-parametrically. At the group level, individual statistic maps were transformed into standard stereotactic space and median activation images constructed. Results Analysis of mean VAS ratings for painful stimulation revealed a significant (χ2 = 27.67, df 2, P=0.001) progressive decrease in perceived intensity of stimulus from the first scanning occasion to the third scanning occasion (mean VAS (+SEM); scan 1 = 7.3+0.45, scan 2 = 6.1 +0.86, scan 3 = 4.8+0.81), which was not seen following non-painful stimulation. In response to painful stimulation, highly reproducible activation was seen in the anterior cingulate gyrus (ACG) (BA24 & 32), bilateral insula, supplementary motor area (SMA), thalamus, bilateral primary and secondary sensory cortices (SIS 114: 559-578 2. Porro CA, Cettolo V, Pia Francescato M, Baraldi P. Temporal and intensity coding in of pain in the human cortex. Journal neurophysiology 1998;80:3312-3320. 3. Ploghaus, A & Tracey, I (2001) Exacerbation of pain by anxiety is associated with activity in the hippocampal network. J neuroscience 2001; 21(24): 9896-9903. 4. Strigo IA, Bushnell MC, Boivin M, Duncan GH. Psychophysical analysis of visceral and cutaneous pain in human subjects. Pain 2002; 97: 235-246.

Comparison of Gradation Characteristics of Various Output Devices for X-Ray Images Using Psychophysical Analysis

Comparison of Gradation Characteristics of Various Output Devices for X-Ray Images Using Psychophysical Analysis

Psychophysical analysis of sound and vibration in the cabin of passenger aircrafts

The vibroacoustics within the fuselage of several types of aircrafts is recorded with microphones, ear-related devices, and accelerometers at different locations of passengers seats, and the workplace of the cabin and cockpit crew. The signals are analyzed according to standard psychoacoustic and vibration parameters. The requirements for the reproduction of the signals in a ground-based test-bed (e.g., mock-up) are identified. Results are reported on how well test facilities at ground meet real-flight conditions. [Work supported by the European Community (www.heace.org).]

Psychophysical analysis of visceral and cutaneous pain in human subjects

Clinical evidence suggests that cutaneous and visceral pain differ in sensory, affective, and motivational realms, yet there has been little comparative characterization of these types of pain. This study uses psychophysical measures to compare directly visceral and cutaneous pain and sensitivity. Healthy subjects (10 males, seven females, age 19–29) evaluated perceptions evoked by balloon distention of the distal esophagus and contact heat on the upper chest. Subjects gave continuous ratings of pain intensity using an on-line visual analog scale (VAS), reported maximum pain intensity and unpleasantness on printed VASs, chose phrases from the McGill Pain Questionnaire and Spielberger State-Trait Anxiety Inventory, and drew the area of perceived sensation. For esophageal distention, the threshold for pain intensity was higher than that observed for unpleasantness, whereas for contact heat, pain and unpleasantness thresholds did not differ for either phasic (10 s) or tonic (36 s) stimulus application. The relative unpleasantness, calculated as the difference between the unpleasantness and the intensity ratings, was higher during esophageal distention than during either phasic or tonic cutaneous heat; this difference in relative unpleasantness was seen at all intensities of esophageal stimulation. Subjects chose significantly more affective words and reported more anxiety during visceral pain than during phasic cutaneous heat pain. A similar tendency was observed when visceral pain was compared to tonic cutaneous heat pain. Subjects also chose a wider range of words to describe visceral than cutaneous pain. On-line VAS ratings revealed greater pain sensation after stimulus termination during visceral than during phasic cutaneous pain; likewise, a similar tendency was observed between visceral and tonic cutaneous pain. Finally, visceral pain led to a more spatially diffuse sensation and was referred to the entire chest and sometimes to the back. Our results show that visceral pain is more unpleasant, diffuse, and variable than cutaneous pain of similar intensity, independent of the duration of the presented stimuli. The data suggest the likelihood of both similarities and differences in the neural substrates underlying visceral and cutaneous pain.

Just noticeable differences in 2D and 3D bar charts: a psychophysical analysis of chart readability.

The comparative readability of 2-dimensional (2D) and 3-dimensional (3D) bar charts was assessed using the method of constant stimuli, and the corresponding Weber constants and just-noticeable-differences were computed. It was predicted that the just-noticeable-difference for 3D charts would be larger than for 2D charts. 36 bar charts (18 2D and 18 3D) were prepared for individual presentation on an overhead projector. Each chart contained two bars, one of standard size (25 units) and a second that varied in size from 24 to 26 units in increments of 0.25 units (1% of the standard). 57 undergraduates in psychology were shown the 36 charts in a random sequence for 3 sec. each, separated by 3-sec. intervals. Participants recorded comparative size judgements of bars for each chart. Multivariate analyses identify an advantage in accuracy (in the order of magnitude of approximately 10%) for 2D rather than 3D bar charts, after controlling for sex, age, and use of corrective lenses. The computed Weber constants for these judgements were similar to those computed for visual intensity over 100 years ago, but--as predicted--the just-noticeable-difference for 3D charts was larger (implying that larger differences are needed on 3D charts to distinguish closely related bars). Furthermore, the use of traditional psychophysical approaches (such as the method of constant stimuli) in assessing graphical aids would appear to be justified.

An In vitro assay useful to determine the potency of several bitter compounds.

Gustducin and transducin are guanine nucleotide binding regulatory proteins (G proteins) expressed in taste receptor cells and implicated in transducing taste cell responses to certain compounds that humans consider bitter or sweet. These G proteins can be activated in vitro by taste receptor-containing membranes plus any of several bitter compounds. This activation can be monitored using limited trypsin digestion, sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Scanning of the autoradiograms enables one to quantitate the level of activation (defined as an activation index), obtain dose-response profiles and estimate the potency of the tastant. This assay may provide a useful substitute for, or adjunct to, the time-consuming human psychophysical analysis and costly animal studies typically used in taste sensory analysis. It may be used to identify and determine the concentration-response function of many bitter components of oral pharmaceuticals and food ingredients. A potential limitation of the assay is that only about half of all bitter compounds tested demonstrated in vitro activity, perhaps due to the presence of multiple transduction pathways. Nevertheless, the rapid throughput and microsample handling capability of this assay make it an ideal method to screen for high-potency bitterness inhibitors.

Psychophysical and behavioral characteristics of olfactory adaptation.

Sensory adaptation allows organisms to reach behavioral equilibrium with the ambient environment and respond primarily to changes in stimulation. Given its functional significance, it is not surprising that adaptation in the olfactory system exhibits many of the same characteristics as adaptation in other sensory systems, including vision. Repeated or prolonged exposure to an odorant typically leads to stimulus-specific decreases in olfactory sensitivity to that odorant, but sensitivity recovers over time in the absence of further exposure. Psychophysical analysis shows that olfactory adaptation results in elevations in odor thresholds and in reduced responsiveness to suprathreshold stimulation. Further, the magnitude of the decrease and the time course of adaptation and recovery are dependent on the concentration of the odor and on the duration of exposure. It is generally agreed that olfactory adaptation can occur at multiple levels in the olfactory system and can involve both peripheral (receptor level) and more central (post-receptor) components. Evidence for peripheral and central involvement comes from studies showing that monorhinal stimulation results in adaptation in both the ipsilateral and contralateral nostril, although the degree of adaptation in the ipsilateral nostril is more profound and recovery is slower. Additional evidence for central involvement comes from studies that have found relatively small decreases in peripheral response following repeated stimulation despite substantial reductions in perceived intensity. Most psychophysical studies of adaptation, however, have not differentiated the peripheral and central processes. Although relatively few in number, studies of the parametric features of olfactory adaptation in both vertebrate (e.g. rat) and invertebrate (e.g. Drosophila, Caenorhabditis elegans) animal models appear to replicate the findings in psychophysical studies of adult humans. Despite the broad overall similarity of olfactory adaptation to adaptation in other sensory systems, olfactory adaptation exhibits some unique features. Adaptation in olfaction has been shown to be very long-lasting in some cases and may be modulated by the contribution of pre-neural events and physico-chemical properties of the odorant molecules that govern diffusion to receptor sites and post-receptor clearance.

Pure word deafness following bilateral lesions. A psychophysical analysis

Pure word deafness following bilateral lesions. A psychophysical analysis

Contrast discrimination, non-uniform patterns and change blindness.

Change blindness--our inability to detect large changes in natural scenes when saccades, blinks and other transients interrupt visual input--seems to contradict psychophysical evidence for our exquisite sensitivity to contrast changes. Can the type of effects described as 'change blindness' be observed with simple, multi-element stimuli, amenable to psychophysical analysis? Such stimuli, composed of five mixed contrast elements, elicited a striking increase in contrast increment thresholds compared to those for an isolated element. Cue presentation prior to the stimulus substantially reduced thresholds, as for change blindness with natural scenes. On one hand, explanations for change blindness based on abstract and sketchy representations in short-term visual memory seem inappropriate for this low-level image property of contrast where there is ample evidence for exquisite performance on memory tasks. On the other hand, the highly increased thresholds for mixed contrast elements, and the decreased thresholds when a cue is present, argue against any simple early attentional or sensory explanation for change blindness. Thus, psychophysical results for very simple patterns cannot straightforwardly predict results even for the slightly more complicated patterns studied here.

Masked hearing thresholds of a beluga whale ( Delphinapterus leucas) in icebreaker noise

An experiment is presented that measured masked hearing thresholds of a beluga whale at the Vancouver Aquarium. The masked signal was a typical beluga vocalization; the masking noise included two types of icebreaker noise and naturally occurring icecracking noise. Thresholds were measured behaviorally in a go/no-go paradigm. Results were that bubbler system noise exhibited the strongest masking effect with a critical noise-to-signal ratio of 15.4 dB. Propeller cavitation noise completely masked the vocalization for noise-to-signal ratios greater than 18.0 dB. Natural icecracking noise showed the least interference with a threshold at 29.0 dB. A psychophysical analysis indicated that the whale did not have a consistent decision bias.

Pure word deafness following bilateral lesions: a psychophysical analysis

Pure word deafness following bilateral lesions: a psychophysical analysis

Evaluation of Radiographic Mottle of Asymmetric Screen-Film System Using Psychophysical Analysis

Evaluation of Radiographic Mottle of Asymmetric Screen-Film System Using Psychophysical Analysis

Detection and discrimination of propionic acid after removal of its 2-DG identified major focus in the olfactory bulb: a psychophysical analysis

Prior 2-deoxyglucose and c- fos studies have demonstrated increased metabolic activity in a rostral dorsomedial area of the olfactory bulb in response to the vapor of propionic acid. We used psychophysical tests to assess the effect of removing this area of the bulb on odor sensitivity and discrimination. Normal rats, those with lesions of the rostral dorsomedial bulb or with control lesions of the lateral olfactory bulb were tested for propionic acid absolute detection and intensity difference thresholds and ability to discriminate propionic acid from other odors. There were no differences among groups for absolute or intensity difference threshold or on simple 2-odor discrimination tests but both groups with bulbar lesions made more errors than controls on a relatively difficult odor-mixture task. The results demonstrate that removal of an area of the bulb identified as responsive to propionic acid is essentially without effect on sensitivity to that odor or ability to discriminate it from other odors.

Evaluation of radiographic mottle using psychophysical analysis

Evaluation of radiographic mottle using psychophysical analysis

Optimum Tube Voltage of Chest Radiographs obtained by Psychophysical Analysis

Optimum Tube Voltage of Chest Radiographs obtained by Psychophysical Analysis

Enhancement of Perceived Visual Intensity by Auditory Stimuli: A Psychophysical Analysis

Abstract Judgments of the intensity of a stimulus are dependent on the level of central nervous system activity it generates. Generally, it is assumed that such judgments are based on activity along modality-specific pathways. Thus, visual intensity judgments would be based on unimodal visual activity. However, many neurons do not fit neatly within modality-specific categories, but can be influenced by more than one sensory modality. Often the "multisensory" effect is quite pronounced. If these multisensory neurons participate in such fundamental functions as perceived intensity, the presence of a nonvisual (i.e., auditory) cue may have a significant effect on the perceived intensity of a visual cue. The results of the present study were consistent with such a hypothesis. A brief, broad-band auditory stimulus was found to significantly enhance the perceived intensity of an LED. The effect was most pronounced at the lowest visual intensities, and was evident regardless of the location of the auditory cue. However, it was present only at the location of visual fixation. Yet, despite the significant influence of the auditory cue, and its differential effect at different visual intensities, a power function that maintains the proportionality among perceived visual intensities was retained.