CORRELATION OF SKIN POTENTIAL AND SKIN RESISTANCE MEASURES

Simultaneous measurements of skin potential (SP) and skin resistance (SR) obtained from 20 male and 20 female adult subjects during 2 sessions held 2 to 9 days apart were used in studying (1) the correlation of change measurements and prestimulus level in the two measures, and (2) the amount of correlation between SP and SR using both simple difference and residual change scores in which the regression of poststimulus values on initial level (prestimulus) has been controlled. Correlations within Ss and correlations among Ss showed large individual variability, correlation differences between males and females, and high correlation between SP and SR change scores. Although the law of initial value (LIV) seemed to have little applicability to the measurement of electrodermal responses, the results underscored the need to control for contamination of change measures by initial level regardless of direction.     

SELECTIVE HABITUATION OF GALVANIC SKIN RESPONSE COMPONENT OF THE ORIENTATION REACTION TO AN AUDITORY STIMULUS

The prediction from Sokolov's (1960) theory that, following OR habituation, size of OR return is proportional to the amount of difference between the new stimulus and the habituating stimulus was tested using an auditory stimulus varying in frequency and intensity. Five Ss were allocated to each of 16 conditions, three conditions involving changes in frequency, three involving changes in intensity, nine involving changes in both frequency and intensity, with one control condition involving a repetition of the habituating stimulus. Following habituation of the GSR component of the OR to a criterion of response failure for three successive trials, magnitude of GSR under the 16 conditions was measured. Contrary to Sokolov's theory, only increase in intensity had a significantly different effect on OR return. More importantly, it was found that Ss habituating rapidly to the initial stimulus were less likely to show OR return to stimulus change. It was concluded that individual differences in habituation rate may be more important than stimulus difference effects in selective habituation.     

SELECTIVE ATTENTION AND INSTRUMENTAL MODIFICATION OF THE GSR

A series of experiments were conducted on instrumental modification of the Galvanic Skin Response (GSR) in a discrimination procedure where preparatory signals indicated which discriminative stimulus was to occur. When shock avoidance was contingent upon the presence of a response the GSR was enhanced; when shock avoidance was contingent upon the inhibition of a response there was a decrement in reactivity. Heart rate acceleration occurred to Respond stimuli while deceleration occurred to Inhibit stimuli. Various types of cognitive strategies were reported by the subjects from attempts to control attention by attending less to stimuli associated with inhibition to attempts to arouse a response by thinking of exciting events and to inhibit by thinking of calming events. Postexperimental recognition of words tended to be negatively related to magnitude of response. When the verbal stimuli served directly as discriminative stimuli, however, these relationships tended to be reversed.     

SIRT3 regulation of mitochondrial oxidative stress

Mitochondria play a central role in the production of reactive oxygen species as byproducts of metabolism and energy production. In order to protect cellular structures from oxidative stress-induced damage, cells have evolved elegant mechanisms for mitochondrial ROS detoxification. The mitochondrial sirtuin, SIRT3, is emerging as a pivotal regulator of oxidative stress by deacetylation of substrates involved in both ROS production and detoxification. This review will summarize recent findings on the regulation of mitochondrial ROS homeostasis by SIRT3.     

A SYSTEM FOR REGISTERING BOTH TRUE AND FALSE FEEDBACK OF THE GALVANIC SKIN RESPONSE

A system has been presented which allows the presentation of either true galvanic skin responses (GSRs) or false GSRs to a recorder viewed by a subject (S). Transistor circuitry is used to produce a double RC circuit using a common capacitor with two variable resistors which control the time constants of the rise and decay of a pulse such that it reflects changes in time of a true GSR. An attenuator controls the proportion of true resistance change of the S which is passed through or added to the response of the false feedback generator. This provides a means of projecting to the S either completely false GSR responding, completely true GSR activity, or a mixture of both. A record of the true responses of the S is obtained by a second recorder viewed only by the experimenter.     

Activation of the prefrontal cortex to trauma-related stimuli measured by near-infrared spectroscopy in posttraumatic stress disorder due to terrorism

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.     

Effects of grip force on skin conductance measured from a handheld device

Skin conductance (SC) reflects stimulus significance and can be measured by integrating electrodes directly onto a smartphone housing such that they are naturally contacted when gripped. However, grip artifacts naturally arise during operation since grip forces can vary. We explored the effects of grip force on SC to determine feasibility and to draw guidelines on artifact mitigation. For this purpose, a prototype was built with integrated SC electrodes with colocated force sensors, and data was collected from 24 participants gripping the prototype across different grip force conditions. Our analysis showed that static forces greater than 2.0 N were associated with significant SC distortion, and artifacts induced from dynamic grip forces were buffered if the SC level was at least 1.1 microsiemens. Our findings are relevant for future applications of SC sensing on smartphones, which may enable interesting and highly contextual user experiences.     

Effects of Feedback in a Forced-Choice GSR Detection Task

Previous studies of the detection of internal events have failed to assess adequately the effects of external feedback on detection and identification of internal events. The purpose of the present study was to make use of a signal detection paradigm in an evaluation of feedback effects on the detection and identification of galvanic skin responses (GSRs). GSR detection was measured by the absolute difference between the areas above and below the receiver operating characteristic (ROC) curve, and reflected the extent to which subjects were able to differentiate between GSR and no-GSR trials. GSR identification was measured by the area below the ROC curve and reflected the labeling strategy (accurate or reversed) chosen by the subjects. It was found that external feedback as to the presence or absence and relative magnitude of GSRs was not necessary for differentiation of GSR and no-GSR trials, and that such feedback was detrimental to increased differentiation over sessions. External feedback may, however, have been useful in directing the attachment of identifying responses to the differentiated internal events. The similarity of these findings to findings reported in the schematic concept formation (SCF) literature was discussed. It was concluded that internal event detection tasks such as that used in the present study may be seen as examples of SCF involving internal stimulus events.