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Conductance Responses (conductance + response)
Kinds of Conductance Responses Selected AbstractsLosses disguised as wins in modern multi-line video slot machinesADDICTION, Issue 10 2010Mike J. Dixon ABSTRACT Aims Players can wager on multiple lines of modern slot machines. When they spin and fail to gain any credits, the machine goes into a state of relative quiet. By contrast, when they spin and win, these spins are accompanied by reinforcing sights and sounds. Such reinforcement also occurs when the amount won is less than the spin wager. We sought to show that these ,losses disguised as wins', or LDWs, would be as arousing as wins, and more arousing than regular losses. Measurement and participants We measured skin conductance response (SCR) amplitudes and heart-rate changes following wins, LDWs and losses for 40 novices playing a multi-line slot machine. Findings SCR amplitudes were similar for wins and LDWs,both were significantly larger than for regular losses. Conclusions For novice players, the reinforcing sights and sounds of the slot machine triggered arousal on wins, where the number of credits gained was greater than the spin wager, but also on ,losses disguised as wins' where the amount ,won' was less than the spin wager. Despite the fact that players lost money on these spins, these outcomes were more arousing than regular losses where no credits were gained. Although these findings involve novice players, the heightened arousal associated with these losses may have implications for the development of problem gambling, as arousal has been viewed as a key reinforcer in gambling behaviour. [source] Electrocortical and electrodermal responses covary as a function of emotional arousal: A single-trial analysisPSYCHOPHYSIOLOGY, Issue 4 2008Andreas Keil Abstract Electrophysiological studies of human visual perception typically involve averaging across trials distributed over time during an experimental session. Using an oscillatory presentation, in which affective or neutral pictures were presented for 6 s, flickering on and off at a rate of 10 Hz, the present study examined single trials of steady-state visual evoked potentials. Moving window averaging and subsequent Fourier analysis at the stimulation frequency yielded spectral amplitude measures of electrocortical activity. Cronbach's alpha reached values >.79, across electrodes. Single-trial electrocortical activation was significantly related to the size of the skin conductance response recorded during affective picture viewing. These results suggest that individual trials of steady-state potentials may yield reliable indices of electrocortical activity in visual cortex and that amplitude modulation of these indices varies with emotional engagement. [source] Activation of the prefrontal cortex to trauma-related stimuli measured by near-infrared spectroscopy in posttraumatic stress disorder due to terrorismPSYCHOPHYSIOLOGY, Issue 4 2003Koji Matsuo Abstract To develop a noninvasive method for psychophysiological assessment of posttraumatic stress disorder (PTSD), 34 victims of the Tokyo Subway Sarin Attack in 1995 including 8 diagnosed as PTSD and 12 controls were examined by a multichannel near-infrared spectroscopy (NIRS) system. Hemodynamic response in the prefrontal cortex was monitored during the presentation of trauma-related and control stimuli by video images. Skin conductance response (SCR) was also examined. Oxygenated hemoglobin significantly increased during the trauma-related image in the victims with or without PTSD. Deoxygenated hemoglobin significantly decreased only in victims with PTSD. No significant alteration was found in controls. Significantly enhanced SCR was also observed in the victims with PTSD during trauma-related stimuli. The findings suggest that measurement of cerebral hemodynamic response by NIRS is useful for psychophysiological assessment of PTSD. [source] Photosynthetic responses of Mojave Desert shrubs to free air CO2 enrichment are greatest during wet yearsGLOBAL CHANGE BIOLOGY, Issue 2 2003Elke Naumburg Abstract It has been suggested that desert vegetation will show the strongest response to rising atmospheric carbon dioxide due to strong water limitations in these systems that may be ameliorated by both photosynthetic enhancements and reductions in stomatal conductance. Here, we report the long-term effect of 55 Pa atmospheric CO2 on photosynthesis and stomatal conductance for three Mojave Desert shrubs of differing leaf phenology (Ambrosia dumosa,drought-deciduous, Krameria erecta,winter-deciduous, Larrea tridentata,evergreen). The shrubs were growing in an undisturbed ecosystem fumigated using FACE technology and were measured over a four-year period that included both above and below-average precipitation. Daily integrated photosynthesis (Aday) was significantly enhanced by elevated CO2 for all three species, although Krameria erecta showed the greatest enhancements (63% vs. 32% for the other species) enhancements were constant throughout the entire measurement period. Only one species, Larrea tridentata, decreased stomatal conductance by 25,50% in response to elevated CO2, and then only at the onset of the summer dry season and following late summer convective precipitation. Similarly, reductions in the maximum carboxylation rate of Rubisco were limited to Larrea during spring. These results suggest that the elevated CO2 response of desert vegetation is a function of complex interactions between species functional types and prevailing environmental conditions. Elevated CO2 did not extend the active growing season into the summer dry season because of overall negligible stomatal conductance responses that did not result in significant water conservation. Overall, we expect the greatest response of desert vegetation during years with above-average precipitation when the active growing season is not limited to ,2 months and, consequently, the effects of increased photosynthesis can accumulate over a biologically significant time period. [source] Covariations among fMRI, skin conductance, and behavioral data during processing of concealed informationHUMAN BRAIN MAPPING, Issue 12 2007Matthias Gamer Abstract Imaging techniques have been used to elucidate the neural correlates that underlie deception. The scientifically best understood paradigm for the detection of deception, however, the guilty knowledge test (GKT), was rarely used in imaging studies. By transferring a GKT-paradigm to a functional magnetic resonance imaging (fMRI) study, while additionally quantifying reaction times and skin conductance responses (SCRs), this study aimed at identifying the neural correlates of the behavioral and electrodermal response pattern typically found in GKT examinations. Prior to MR scanning, subjects viewed two specific items (probes) and were instructed to hide their knowledge of these. Two other specific items were designated as targets and required a different behavioral response during the experiment and eight items served as irrelevant stimuli. Reaction times and SCR amplitudes differed significantly between all three item types. The neuroimaging data revealed that right inferior frontal and mid-cingulate regions were more active for probe and target trials compared to irrelevants. Moreover, the differential activation in the right inferior frontal region was modulated by stimulus conflicts. These results were interpreted as an increased top-down influence on the stimulus-response-mapping for concealed and task-relevant items. Additionally, the influence of working memory and retrieval processes on this activation pattern is discussed. Using parametric analyses, reaction times and SCR amplitudes were found to be linearly related to activity in the cerebellum, the right inferior frontal cortex, and the supplementary motor area. This result provides a first link between behavioral measures, sympathetic arousal, and neural activation patterns during a GKT examination. Hum Brain Mapp 2007. © 2007 Wiley-Liss, Inc. [source] Amygdala,prefrontal dissociation of subliminal and supraliminal fearHUMAN BRAIN MAPPING, Issue 8 2006Leanne M. Williams Abstract Facial expressions of fear are universally recognized signals of potential threat. Humans may have evolved specialized neural systems for responding to fear in the absence of conscious stimulus detection. We used functional neuroimaging to establish whether the amygdala and the medial prefrontal regions to which it projects are engaged by subliminal fearful faces and whether responses to subliminal fear are distinguished from those to supraliminal fear. We also examined the time course of amygdala-medial prefrontal responses to supraliminal and subliminal fear. Stimuli were fearful and neutral baseline faces, presented under subliminal (16.7 ms and masked) or supraliminal (500 ms) conditions. Skin conductance responses (SCRs) were recorded simultaneously as an objective index of fear perception. SPM2 was used to undertake search region-of-interest (ROI) analyses for the amygdala and medial prefrontal (including anterior cingulate) cortex, and complementary whole-brain analyses. Time series data were extracted from ROIs to examine activity across early versus late phases of the experiment. SCRs and amygdala activity were enhanced in response to both subliminal and supraliminal fear perception. Time series analysis showed a trend toward greater right amygdala responses to subliminal fear, but left-sided responses to supraliminal fear. Cortically, subliminal fear was distinguished by right ventral anterior cingulate activity and supraliminal fear by dorsal anterior cingulate and medial prefrontal activity. Although subcortical amygdala activity was relatively persistent for subliminal fear, supraliminal fear showed more sustained cortical activity. The findings suggest that preverbal processing of fear may occur via a direct rostral,ventral amygdala pathway without the need for conscious surveillance, whereas elaboration of consciously attended signals of fear may rely on higher-order processing within a dorsal cortico,amygdala pathway. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Mapping the time course of nonconscious and conscious perception of fear: An integration of central and peripheral measuresHUMAN BRAIN MAPPING, Issue 2 2004Leanne M. Williams Abstract Neuroimaging studies using backward masking suggest that conscious and nonconscious responses to complex signals of fear (facial expressions) occur via parallel cortical and subcortical circuits. Little is known, however, about the temporal differentiation of these responses. Psychophysics procedures were first used to determine objective thresholds for both nonconscious detection (face vs. blank screen) and discrimination (fear vs. neutral face) in a backward masking paradigm. Event-related potentials (ERPs) were then recorded (n = 20) using these thresholds. Ten blocks of masked fear and neutral faces were presented under each threshold condition. Simultaneously recorded skin conductance responses (SCRs) provided an independent index of stimulus perception. It was found that Fear stimuli evoked faster SCR rise times than did neutral stimuli across all conditions, indicating that emotional content influenced responses, regardless of awareness. In the first 400 msec of processing, ERPs dissociated the time course of conscious (enhanced N4 component) from nonconscious (enhanced N2 component) perception of fear, relative to neutral. Nonconscious detection of fear also elicited relatively faster P1 responses within 100 msec post-stimulus. The N2 may provide a temporal correlate of the initial sensory processing of salient facial configurations, which is enhanced when top-down cortical feedback is precluded. By contrast, the N4 may index the conscious integration of emotion stimuli in working memory, subserved by greater cortical engagement. Hum. Brain Mapping 21:64,74, 2004. © 2003 Wiley-Liss, Inc. [source] Skin conductance and heart-rate responses as indices of covert face recognition in preschool childrenINFANT AND CHILD DEVELOPMENT, Issue 5 2004Kjell Morten Stormark Abstract Covert face recognition was examined in 12 young preschoolers (age range 26,48 months) by comparing their autonomic functions to slides depicting former playmates from a family nursery school that the preschoolers had attended earlier with slides of their present playmates and unfamiliar children. While all preschoolers reported corroborated overt recognition of present playmates after the experiment, only three of them did so in relation to former playmates. The distribution of yes,no responses on the overt recognition task to former playmates was not significantly different from the responses to unfamiliar children. Nevertheless, the preschoolers evidenced increased skin conductance responses (SCRs) and more pronounced heart rate (HR) deceleration to the slides depicting former classmates compared to unfamiliar children. Thus, although the preschoolers' verbal responses did not differentiate between former playmates and unfamiliar children, their autonomic functions did. These findings suggest that young children can retain memories of past experiences in an implicit form without corroborated overt recognition. Copyright © 2004 John Wiley & Sons, Ltd. [source] Decision making in Parkinson's disease: Analysis of behavioral and physiological patterns in the Iowa gambling taskMOVEMENT DISORDERS, Issue 4 2008Mutsutaka Kobayakawa PhD Abstract Recent studies suggest that social recognition processes are affected by Parkinson's disease (PD). However, whether PD patients exhibit behavioral changes is still controversial. The purpose of the present study was to examine the decision making of PD patients performing the Iowa Gambling Task (IGT). We recruited a large number of early, nondemented PD patients for the IGT. We also recorded the skin conductance responses (SCRs) during the task as a measure of emotional arousal. Compared with the normal control (NC) subjects, PD patients selected more disadvantageous decks in the IGT, and their SCRs were lower than those of NC subjects before making decisions and after receiving reward or punishment. The tendency toward risky choices was not correlated with age, education, global cognitive function, or the severity of the disease. These results confirmed that the decision making of PD patients was affected by the disease, rather than by other cognitive functions; moreover, such behavior was related to lower emotional responses. Behavioral and SCR patterns of PD patients were similar to those of amygdala-damaged patients. The response bias toward risky choices in PD may be explained by the dysfunction of the amygdala, which is known to be involved in risk evaluation. © 2007 Movement Disorder Society [source] The effects of smoking on selective attention as measured by startle reflex, skin conductance, and heart rate responses to auditory startle stimuliPSYCHOPHYSIOLOGY, Issue 1 2010Justin E. Greenstein Abstract The present study examined the effects of cigarette smoking on attentional processing by measuring nondeprived smokers' (n=39), minimally deprived smokers' (n=36), and nonsmokers' (n=34) startle eyeblink reflex, heart rate, and skin conductance responses (SCR) to acoustic startle stimuli (105 dB) during directed attention tasks. Whereas smokers demonstrated smaller startle responses than nonsmokers during a directed attention visual task, no difference in startle response magnitude emerged between the two smoking groups, nor did we observe an effect of smoking on SCR or heart rate response to the startle stimuli. Our findings suggest that smokers differ from nonsmokers in their selective attention abilities and that smoking does not enhance minimally deprived smokers' selective attention. [source] The skin conductance orienting response to semantic stimuli: Significance can be independent of arousalPSYCHOPHYSIOLOGY, Issue 1 2008Lilian Dindo Abstract The characteristics of stimuli that elicit skin conductance responses (SCRs) have been conceptualized in varied ways, with strong emphasis on the significance or arousing quality of stimuli. Our goal was to determine whether "significance" can be shown to have an effect on SCRs independent of "arousal," using words as stimuli. Ratings of words indicated that significance is partially independent of arousal. In Study 1, SCRs from 43 participants during presentation of 20 significant, nonarousing words with a negative valence that were either depression related or potentially self-referent and 20 nonsignificant words matched on valence and arousal showed a main effect of significance. In Study 2 (N=44), significant, nonarousing words were sampled more broadly to examine the effects of self-reference and valence. Significance, rather than just negativity or self-reference, elicited SCRs independently of arousal. SCRs to significant words may reflect cognitive and attentional processes that, in turn, might prove useful for the assessment of the cognitive aspects of anxiety. [source] Schedule-induced electrodermal responding in childrenPSYCHOPHYSIOLOGY, Issue 6 2006Robert D. Latzman Abstract The current studies were designed to determine whether different intermittent schedules of reinforcement would have a differential effect on the skin conductance responses (SCRs) of children in the 8,12-year-old age range. Results of two experiments indicated that the amplitude of children's SCRs immediately following the occurrence of reinforcement were a function of the schedule of reinforcement, with larger SCRs associated with longer inter-reinforcement intervals. The findings are consistent with the research literature suggesting that long inter-reinforcement intervals can be evocative of aversively motivated emotions, as well as with research on the effects of interstimulus intervals on SCRs. Possible implications for these findings are discussed. [source] Pericranial muscular, respiratory, and heart rate components of the orienting responsePSYCHOPHYSIOLOGY, Issue 6 2002J.J. Stekelenburg We have earlier found that voluntary attention to weak auditory stimuli induces inhibition of respiration, heart rate, and electromyographic (EMG) activity of masticatory and lower facial muscles and that these responses lower the auditory threshold for low-frequency sounds. In the current study, we examined whether this inhibitory response pattern also occurs during involuntary orienting to novel, nonsignal sounds. Environmental sounds of low intensity were presented unexpectedly during the performance of a reading task. Orienting responses (ORs) were elicited as indicated by heart rate deceleration and skin conductance responses. Inhibitory respiratory and pericranial EMG responses appeared to be intrinsic components of the OR. Together with the autonomic responses, they habituated when a nonsignal auditory stimulus was repeatedly presented. Our results also suggest that eye and pinna movements occurred toward the sound source. The results of the current study are consistent with the hypothesis of Sokolov (1963) that the primary function of the OR is enhancement of sensory sensitivity. [source] The temporal stability of electrodermal variables over a one-year period in patients with recent-onset schizophrenia and in normal subjectsPSYCHOPHYSIOLOGY, Issue 2 2002Anne M. Schell Test,retest stability of electrodermal (EDA) variables indexing both general autonomic arousal (e.g., skin conductance level, number of nonspecific skin conductance responses) and attention to external stimuli (e.g., number of skin conductance orienting responses, electrodermal responder/nonresponder status) was assessed in 71 young, recent-onset schizophrenia patients and 36 demographically matched normal subjects. Significant stability over a 1-year period was found for both patients and normal subjects for most EDA variables and for responder/nonresponder status, with test,retest correlations generally being higher for normal subjects. The lower reliability for patients was not attributable to symptomatic fluctuations during the follow-up period and may reflect poorer arousal regulation among the patients. Among measures of responding to nontask stimuli, a simple count of the number of orienting responses occurring was more stable than was a traditional trials-to-habituation measure. [source] Masked fear words produce increased SCRs: An anomaly for Öhman's theory of pre-attentive processing in anxietyPSYCHOPHYSIOLOGY, Issue 3 2000M.A. van den Hout A. Öhman and J.J.F. Soares (1994) demonstrated that masked presentation of phobic pictures produces increased skin conductance responses (SCRs) in phobic subjects. A. Öhman (1993) explained this phenomenon in terms of a hypothetical "feature detector" that identifies physical characteristics of stimuli and activates the arousal system without involving significance evaluation or consciousness. By exposing spider phobics to spider words, general threat words, and neutral words instead of pictures, this explanation was tested. Words were presented both masked and unmasked while electrodermal activity was measured. Under unmasked conditions, SCRs were largest for spider words followed by general threat words, then neutral words. When masked, the difference between spider words and general threat words disappeared but SCRs remained significantly smaller for neutral words. It is concluded that activation of the arousal system by masked threat cues does not necessarily depend on their perceptual characteristics. [source] | ||||||||||||||||