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Malek Adjouadi - One of the best experts on this subject based on the ideXlab platform.
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Off-line and on-line stress detection through processing of the Pupil Diameter signal
Annals of Biomedical Engineering, 2014Co-Authors: Peng Ren, Francisco R. Ortega, Armando Barreto, Ying Gao, Malek AdjouadiAbstract:The Pupil Diameter (PD), controlled by the autonomic nervous system, seems to provide a strong indication of affective arousal, as found by previous research, but it has not been investigated fully yet. In this study, new approaches based on monitoring and processing the PD signal for off-line and on-line "relaxation" vs. "stress" differentiation are proposed. For the off-line approach, wavelet denoising, Kalman filtering, data normalization, and feature extraction are sequentially utilized. For the on-line approach, a hard threshold, a moving average window and three stress detection steps are implemented. In order to use only the most reliable data, two types of data selection methods (paired t test based on galvanic skin response (GSR) data and subject self-evaluation) are applied, achieving average classification accuracies up to 86.43 and 87.20% for off-line and 72.30 and 73.55% for on-line algorithms, with each set of selected data, respectively. The GSR was also monitored and processed in our experiments for comparison purposes, with the highest classification rate achieved being only 63.57% (based on the off-line processing algorithm). The overall results show that the PD signal is more effective and robust for differentiating "relaxation" vs. "stress," in comparison with the traditionally used GSR signal.
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Affective Assessment by Digital Processing of the Pupil Diameter
IEEE Transactions on Affective Computing, 2013Co-Authors: P Ren, Armando Barreto, Malek Adjouadi, Yimin GaoAbstract:Previous research found that the Pupil Diameter (PD) can be an indication of affective state, but this approach to the detection of the affective state of a computer user has not been investigated fully. We propose a new affective sensing approach to evaluate the computer user's affective states as they transition from "relaxation” to "stress,” through processing the PD signal. Wavelet denoising and Kalman filtering were used to preprocess the PD signal. Then, three features were extracted from it and five classification algorithms were used to evaluate the overall performance of the identification of "stress” states in the computer users, achieving an average accuracy of 83.16 percent, with the highest accuracy of 84.21 percent reached with a Multilayer Perceptron and a Naive Bayes classifier. The Galvanic Skin Response (GSR) signal was also analyzed to study the comparative efficiency of affective sensing through the PD signal. We compared the discriminating power of the three features derived from the preprocessed PD signal to three features derived from the preprocessed GSR signal in terms of their Receiver Operating Characteristic curves. The results confirm that the PD signal should be considered a powerful physiological factor to involve in future automated affective classification systems for human-computer interaction.
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comparison of the use of Pupil Diameter and galvanic skin response signals for affective assessment of computer users
Biomedical sciences instrumentation, 2012Co-Authors: Peng Ren, Armando Barreto, Ying Gao, Malek AdjouadiAbstract:The implementation of Affective Computing concepts requires the assessment of the affective states in the computer user, e.g., relaxation or stress. Traditionally, the Galvanic Skin Response (GSR) signal has been analyzed as the leading indicator of the sympathetic activation that accompanies stress, when it is experienced by a computer user. However, recent research has found that the Pupil Diameter (PD), which is also controlled by the Autonomic Nervous System (ANS), can be an important indicator of sympathetic activation. This paper describes techniques for the processing of the Pupil Diameter (PD) signal to detect episodes of mental stress induced in experimental subjects, differentiating them from relaxation intervals. Our experiments also recorded and analyzed the GSR signal from the subjects, for comparison purposes. The PD signal is first pre-processed applying wavelet denoising and Kalman filtering to remove the high-frequency variations of the raw PD signal that are not representative of the subjects affective state. Then 3 features are extracted from the normalized, pre-processed PD signal and five different classification algorithms are applied on these features to differentiate the states of relaxation vs. stress in the computer user. Similarly, 3 GSR features were obtained and used for classification. PD-based classification achieved an average accuracy of 85.86%. GSR-based classification achieved an average accuracy of 60.66%. Therefore, the results indicate that the Pupil Diameter may be one of the most significant physiological signals to monitor for affective assessment and differentiation of relaxation vs. stress states of a computer user.
Sabine Schmitz - One of the best experts on this subject based on the ideXlab platform.
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comparison of three different technologies for Pupil Diameter measurement
Graefes Archive for Clinical and Experimental Ophthalmology, 2003Co-Authors: Sabine Schmitz, Sebastian Henn, F. Krummenauer, Burkhard H DickAbstract:Background The Pupil Diameter plays an important role in the occurrence of photopic phenomena after refractive surgery. Standardized estimation can be performed using a lens system with a built-in millimeter scale (Colvard, Oasis Medical, California). A new computerized technique allows dynamic and binocular measurement of the Pupil Diameter by use of infrared light (P2000SA, Procyon Instruments, London, UK). An additional approach is a wavefront aberrometer based on the Hartmann-Shack principle (WASCA; Asclepion-Meditec-Zeiss, Jena, Germany). These strategies were compared.
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Comparison of three different technologies for Pupil Diameter measurement
Graefe's Archive for Clinical and Experimental Ophthalmology, 2003Co-Authors: Sabine Schmitz, Sebastian Henn, F. Krummenauer, H. Burkhard DickAbstract:BACKGROUND: The Pupil Diameter plays an important role in the occurrence of photopic phenomena after refractive surgery. Standardized estimation can be performed using a lens system with a built-in millimeter scale (Colvard, Oasis Medical, California). A new computerized technique allows dynamic and binocular measurement of the Pupil Diameter by use of infrared light (P2000SA, Procyon Instruments, London, UK). An additional approach is a wavefront aberrometer based on the Hartmann-Shack principle (WASCA; Asclepion-Meditec-Zeiss, Jena, Germany). These strategies were compared. DESIGN: Non-randomized comparative trial. PARTICIPANTS AND METHODS: The Pupil Diameter of 56 eyes of 28 probands (18 female, mean age 23 years) was measured under scotopic conditions by three independent examiners with each measurement device. The measurement devices were compared intraindividually by pairwise sign tests. Description was based on the intraindividual differences' medians and quantiles. RESULTS: Median Pupil Diameters were 6.67 mm for the scale Pupillometer (interquartile range 6.07-6.94 mm), 6.60 mm for the dynamic Pupillometer (6.0-7.02 mm), and 6.37 mm for the wavefront-based aberrometer (5.9-6.7 mm). Pairwise comparison revealed statistically significant ( P
Thomas Kohnen - One of the best experts on this subject based on the ideXlab platform.
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intraindividual comparison of higher order aberrations after implantation of aspherical and spherical intraocular lenses as a function of Pupil Diameter
Journal of Cataract and Refractive Surgery, 2006Co-Authors: T Kasper, Jens Buhren, Thomas KohnenAbstract:Purpose To compare intraindividual higher-order wavefront aberrations after implantation of aspherical and spherical intraocular lenses (IOLs) as function of Pupil Diameter. Setting Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. Methods In this prospective study, wavefront measurements of 21 patients after implantation of a spherical IOL (AMO AR40e) in 1 eye and an aspherical IOL (AMO Tecnis) in the contralateral eye were analyzed. Third-, 4th-, 5th-, total higher-order aberration (HOA) root-mean-square (RMS), and primary spherical aberration (Z 4 0 ) were compared at different virtual Pupil Diameters of 3 to 6 mm. Results For both IOLs and each higher order analyzed, values increased with increasing Pupil Diameter. Fourth-order RMS and Z 4 0 in the aspherical IOL group were significantly lower than with the spherical IOL at all analyzed Pupil Diameters. The total HOA RMS of the aspherical IOL was significantly lower than the spherical IOL only at 6 mm Pupil Diameter. For 3rd- and 5th-order RMS, no significant difference was found between the tested IOLs at any Pupil Diameter. Conclusion In comparison to a spherical IOL, the aspherical Tecnis IOL reduced Z 4 0 and 4th-order RMS significantly for Pupil Diameters of 3 to 6 mm, whereas total HOA RMS was only significantly reduced for a Pupil Diameter of 6 mm.
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comparison of a digital and a handheld infrared Pupillometer for determining scotopic Pupil Diameter
Journal of Cataract and Refractive Surgery, 2003Co-Authors: Thomas Kohnen, Jens Buhren, E Terzi, Eva Maria KohnenAbstract:Abstract Purpose To compare a digital infrared Pupillometer with a handheld infrared Pupillometer for determining scotopic Pupil size. Setting Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. Methods In 100 eyes of 50 healthy individuals (mean age 38.8 years ± 10.7 [SD]), the scotopic Pupil size was measured with a digital (Procyon) and a handheld (Colvard) infrared Pupillometer. After dark adaptation of 1 minute, measurements were performed with both devices by 2 examiners (E1 and E2). Agreement and repeatability were analyzed using a comparison method described by Bland and Altman. Results The mean scotopic Pupil Diameter was 5.90 ± 0.97 mm (range 3.24 to 7.91 mm) with the Procyon and 5.78 ± 0.98 mm (range 3.00 to 7.30 mm) with the Colvard Pupillometer. The mean difference between the 2 devices was −0.01 mm (E1) and −0.24 mm (E2). The limits of agreement ranged from 2.84 (E1) to 3.24 (E2). The coefficients of repeatability were 0.64 (Procyon) and 1.16 (Colvard). The mean difference between E1 and E2 was −0.10 for the Procyon and 0.13 for the Colvard Pupillometer. The limits of agreement ranged from 1.28 (Procyon) to 2.32 (Colvard). Conclusions The digital infrared Pupillometer (Procyon) demonstrated better repeatability and agreement in measuring scotopic Pupil size than a handheld device (Colvard).
P Lang - One of the best experts on this subject based on the ideXlab platform.
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motivated action Pupil Diameter during active coping
Biological Psychology, 2020Co-Authors: Christopher T Sege, Margaret M Bradley, P LangAbstract:Abstract Pupil Diameter is dynamically modulated by a number of factors, including emotion, motor activity, and attention. Here, Pupil modulation was examined as it varies with locus of control during aversive processing. Participants could control aversive exposure either by escape (terminating the event) or avoidance (blocking the event entirely), or they had no control. Highly anxious (n = 19), moderately anxious (n = 23), and less anxious (n = 23) participants saw cues that signaled whether a fast button press would terminate, prevent, or not affect subsequent presentation of an aversive picture. Pupil Diameter was measured throughout the cuing interval. Pupil Diameter was larger when preparing to escape or avoid compared to anticipating uncontrollable exposure. All participants, regardless of reported anxiety, showed increased Pupil Diameter in coping, relative to uncontrollable, contexts. Results support hypotheses that Pupil Diameter reflects action preparation and that differences in trait anxiety do not modulate this aspect of coping behavior in healthy subjects.
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emotional imagery and Pupil Diameter
Psychophysiology, 2018Co-Authors: Robert R Henderson, Margaret M Bradley, P LangAbstract:Pupil Diameter is enhanced in a variety of emotional contexts, including viewing pictures, listening to sounds, and during threat of shock. In this study, we investigated Pupil Diameter changes during emotional imagery. Participants imagined scenes describing pleasant, unpleasant, or neutral events while Pupil Diameter was continuously recorded. Second by second changes in Pupil Diameter were analyzed to determine whether, and when, modulation of the Pupil as a function of hedonic content is found. Results indicated a significant effect of hedonic content beginning shortly after script onset, with enhanced Pupil Diameter when imagining emotional (pleasant or unpleasant), compared to neutral, scenes. Pupil Diameter during imagery covaried with rated emotional arousal, consistent with an interpretation that changes in Pupil Diameter during emotional imagery reflect sympathetic nervous system activity. Because emotional imagery is a key element in clinical assessment and treatment, Pupil Diameter could prove a useful index of emotional engagement in a variety of clinically pertinent contexts.
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sympathetic ans modulation of Pupil Diameter in emotional scene perception effects of hedonic content brightness and contrast
Psychophysiology, 2017Co-Authors: Margaret M Bradley, Rosemarie G Sapigao, P LangAbstract:A series of studies investigated the effects of hedonic content, brightness, and contrast on Pupil Diameter during free viewing of natural scenes, assessing the amplitude of the initial light reflex and subsequent sustained Pupil Diameter change. Hedonic picture content varied from highly arousing scenes of erotica and violence to scenes depicting nature, babies, loss, contamination, food, and more. Despite equivalent overall picture brightness and contrast, Pupil Diameter still varied as a function of the local brightness of central vision at fixation. Statistical (Experiment 1) and methodological (Experiment 2, 3) solutions produced complementary data indicating that scenes of erotica and violence reliably attenuate the amplitude of the initial light reflex and prompt enhanced late Diameter Pupil changes, compared to other scene contents. A principal components analysis supported the hypothesis that a single sympathetically mediated process enhances Pupil dilation during picture viewing, modulating both initial constriction and late Diameter changes. Rather than being a subtle index of “liking,” Pupil Diameter is primarily sensitive to events that reliably elicit measurable sympathetic nervous system activity.
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memory emotion and Pupil Diameter repetition of natural scenes
Psychophysiology, 2015Co-Authors: Margaret M Bradley, P LangAbstract:Recent studies have suggested that Pupil Diameter, like the “old-new” ERP, may be a measure of memory. Because the amplitude of the old-new ERP is enhanced for items encoded in the context of repetitions that are distributed (spaced), compared to massed (contiguous), we investigated whether Pupil Diameter is similarly sensitive to repetition. Emotional and neutral pictures of natural scenes were viewed once or repeated with massed (contiguous) or distributed (spaced) repetition during incidental free viewing and then tested on an explicit recognition test. Although an old-new difference in Pupil Diameter was found during successful recognition, Pupil Diameter was not enhanced for distributed, compared to massed, repetitions during either recognition or initial free viewing. Moreover, whereas a significant old-new difference was found for erotic scenes that had been seen only once during encoding, this difference was absent when erotic scenes were repeated. Taken together, the data suggest that Pupil Diameter is not a straightforward index of prior occurrence for natural scenes.
H. Burkhard Dick - One of the best experts on this subject based on the ideXlab platform.
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Comparison of three different technologies for Pupil Diameter measurement
Graefe's Archive for Clinical and Experimental Ophthalmology, 2003Co-Authors: Sabine Schmitz, Sebastian Henn, F. Krummenauer, H. Burkhard DickAbstract:BACKGROUND: The Pupil Diameter plays an important role in the occurrence of photopic phenomena after refractive surgery. Standardized estimation can be performed using a lens system with a built-in millimeter scale (Colvard, Oasis Medical, California). A new computerized technique allows dynamic and binocular measurement of the Pupil Diameter by use of infrared light (P2000SA, Procyon Instruments, London, UK). An additional approach is a wavefront aberrometer based on the Hartmann-Shack principle (WASCA; Asclepion-Meditec-Zeiss, Jena, Germany). These strategies were compared. DESIGN: Non-randomized comparative trial. PARTICIPANTS AND METHODS: The Pupil Diameter of 56 eyes of 28 probands (18 female, mean age 23 years) was measured under scotopic conditions by three independent examiners with each measurement device. The measurement devices were compared intraindividually by pairwise sign tests. Description was based on the intraindividual differences' medians and quantiles. RESULTS: Median Pupil Diameters were 6.67 mm for the scale Pupillometer (interquartile range 6.07-6.94 mm), 6.60 mm for the dynamic Pupillometer (6.0-7.02 mm), and 6.37 mm for the wavefront-based aberrometer (5.9-6.7 mm). Pairwise comparison revealed statistically significant ( P
