Florian Schaefer

Dissociation of decision-making under ambiguity and decision-making under risk in patients with Parkinson's disease: A neuropsychological and psychophysiological study

Decision-making impairments in Parkinsons disease (PD) are most likely associated with dysfunctions in fronto-striatal loops. Recent studies examined decision-making in PD either in ambiguous situations with implicit rules, using the Iowa Gambling Task (IGT), or in risky situations with explicit rules, using the Game of Dice Task (GDT). Both tasks have been associated with the limbic-orbitofrontal-striatal loop, involved in emotional processing. However, the GDT has additionally been highly associated with the dorsolateral prefrontal-striatal loop, being involved in executive functions. The present study is the first one which examined decision-making in PD patients with both, IGT and GDT. We studied 21 non-demented PD patients on dopaminergic medication and 23 healthy controls with both tasks and a neuropsychological test battery with focus on executive functions. To analyse possible abnormalities in emotional processing, electrodermal responses (EDRs) were assessed while performing the tasks. We found that PD patients were significantly impaired in the GDT, but not in the IGT. Executive dysfunctions correlated with GDT but not with IGT performance. In both tasks, PD patients showed significantly reduced feedback EDRs after losses, but not after gains, indicating a primary decline of sensitivity to negative feedback. Our behavioural data suggest that dysfunctions in the dorsolateral prefrontal loop might be stronger than in the limbic loop, resulting in deficits in executive functions and GDT performance but unimpaired IGT performance. Reduced sensitivity to negative feedback is discussed with regard to dysfunctions in the limbic loop, which may result from pathology of limbic structures or dopaminergic medication.

Effects of stimulus intensity, risetime, and duration on autonomic and behavioral responding: implications for the differentiation of orienting, startle, and defense responses.

The effects of stimulus intensity, duration, and risetime on the autonomic and behavioral components of orienting, startle, and defense responses were investigated. Six groups of 10 students were presented with 15 white noise stimuli at either 60 or 100 dB, with controlled risetimes of either 5 or 200 ms, and at stimulus durations of 1 or 5 s (1 s only in the case of the 60-dB groups). A dishabituation stimulus consisting of a 1000 Hz tone was also presented. Measures consisted of skin conductance and heart rate, together with ratings of facial expressions and upper torso movement obtained using video recording. Increased intensity resulted in greater amplitudes and frequencies of electrodermal and behavioral responses, and a change from cardiac deceleration to acceleration. Faster risetimes elicited larger electrodermal responses, greater frequencies of eye-blinks, head and body movements, and larger cardiac accelerations. The effects of duration for the 100-dB stimuli were less clear-cut. Overall, the results are discussed in relation to the differentiation of orienting, startle, and defense responses.

Experimental investigation of psychophysiological stress-reactions induced by different system response times in human-computer interaction∗

In human-computer interaction, system response times are considered to have important effects on operator performance and stress response. To evaluate the effects of short (2s) and long (8s), as well as constant and variable, system response times, a laboratory study was conducted with 68 subjects in four independent groups working at a simulated computer workplace. Subjects had to perform a simple detection and correction task at a visual display terminal in six trials of 20min each, the first being a training trial with identical conditions for all subjects. Performance and physiological measures (heart rate, electrodermal activity, and blood pressure) were taken during the trials, and subjective measures of mood and physical state as well as physiological measures were done in the resting periods iiftcr the trials. In addition to a general adaptation effect over the trials, experimental effects were shown mainly for the duration factor: subjects under conditions of long, as compared to those under shor...

Combining electrodermal responses and cardiovascular measures for probing adaptive automation during simulated flight

Adaptive automation increases the operators workload in case of hypovigilance and takes over more responsibility if workload becomes too high. Two consecutive studies were conducted to construct a biocybernetic adaptive system for a professional flight simulator, based on autonomic measures. Workload was varied through different stages of turbulences. In a first study with 18 participants, electrodermal responses of experimental subjects oscillated very close to the individual set point, demonstrating that workload level was adjusted as a result of adaptive control, which was not the case in yoked control subjects without adaptive automation. Combining electrodermal responses with heart rate variability in a second study with 48 participants further enhanced the adaptive power which was seen in even smaller set point deviations for the experimental compared to the yoked control group. We conclude that the level of arousal can be adjusted to avoid hypovigilance by combining autonomic measures in a closed loop.

Physiological changes during computer tasks: responses to mental load or to motor demands?

Cardiac and electrodermal measures are regarded as indicators of user strain during computer work, not taking the possible influence of finger and hand movements on these measures into account. For the evaluation of such effects, motor demands and mental load were both varied as independent factors in two experiments. As a motor task, subjects had to produce compensatory keystrokes at different speed levels to keep a moving mark within a target area on the computer screen. Mental load was varied in experiment 1 by manipulation of keystroke synchronization accuracy, and in experiment 2 by manipulation of memory load. Physiological measures were affected by motor activity only at a very high typing speed. At lower levels of motor activity physiological effects were dependent exclusively on mental load. Frequency of skin conductance responses was the most sensitive indicator of the emotional consequences of mental load and mean heart period reflected its attentional aspects. The study supports the assumption that physiological effects of motor activity can be neglected during typical computer tasks, demanding keystrokes at intervals of 300 ms or longer.

The color-vision approach to emotional space: Cortical evoked potential data

A framework for accounting for emotional phenomena proposed by Sokolov and Boucsein (2000) employs conceptual dimensions that parallel those of hue, brightness, and saturation in color vision. The approach that employs the concepts of emotional quality, intensity, and saturation has been supported by psychophysical emotional scaling data gathered from a few trained observers. We report cortical evoked potential data obtained during the change between different emotions expressed in schematic faces. Twenty-five subjects (13 male, 12 female) were presented with a positive, a negative, and a neutral computer-generated face with random interstimulus intervals in a within-subjects design, together with four meaningful and four meaningless control stimuli made up from the same elements. Frontal, central, parietal, and temporal ERPs were recorded from each hemisphere. Statistically significant outcomes in the P300 and N200 range support the potential fruitfulness of the proposed color-vision-model-based approach to human emotional space.

Comparison of electrodermal constant voltage and constant current recording techniques using the phase angle between alternating voltage and current

If electrodermal activity is recorded with direct current, constant voltage and constant current measurements result in different dependencies of electrodermal reactions on the actual electrodermal level. The present study demonstrates empirically that such a problem does not exist when instead the phase angle changes between alternating current and voltage are obtained. Forty subjects were subjected to a 20-trial habituation series on two different occasions, in which electrodermal level variations were induced by room temperature changes. A multiplexing system was used to enable quasi-simultaneous constant current and constant voltage recording under both direct and alternating current measurement conditions. If the alternating current technique was applied and electrodermal responses were expressed as changes of phase angle between voltage and current, electrodermal recordings with constant voltage and with constant current provided equivalent results, even if electrodermal levels were considerably different. Therefore, using the phase angle method instead of the conventional direct current methods will finally resolve the problem of differential level dependency in electrodermal recording. A further advantage will be that electrode and skin polarization are prevented by the use of alternating current.

Objective emotional assessment of tactile hair properties and their modulation by different product worlds.

Tactile properties of cosmetic products constitute weak stimuli and thus can be expected to be easily modified by mental images. In order to enhance an intended positive‐emotion‐inducing effect of such a product, its experience can be embedded in a certain ‘world’ that generates a positive emotional imagination. The present study investigated such an influence in 12 males and 12 females, half of each being laymen and experts in sensory assessment. Two product worlds (emotional and technical) and three different hair samples, two of them treated with different shampoos and an untreated one as control, were presented to each subject in counter‐balanced order of all six combinations. An objective emotional assessment using a psychophysiological technique developed in an earlier study was applied and compared with a traditional sensory assessment. Among the physiological measures, peripheral blood volume and facial muscular activity were the most sensitive in revealing effects of and interactions between the product worlds and hair samples. A multivariate evaluation of the physiological data revealed three discriminant functions that explained 78.4% of the total variance and enabled a re‐classification considerably better than chance. The first discriminant function clearly separated the treated from the untreated hair samples which was not possible by subjective ratings or traditional sensory assessment. The two other discriminant functions comprised a hedonistic and a product world factor. The emotional product world exerted the largest influence in case of the weakest tactile differences between the hair samples, and its influence was larger on laymen than on experts. Gender effects were most prominent in the subjective domain. In conclusion, multivariate psychophysiological methodology is superior to traditional sensory assessment in revealing subtle differences in the tactile perception of cosmetic products.

The Usability of Cardiovascular and Electrodermal Measures for Adaptive Automation

In case of adaptive automation, a system automatically increases the operator’s workload if there are signs of hypovigilance, reflected in psychophysiological arousal measures such as spontaneous electrodermal activity, and takes over more responsibility in case of workload becoming too high. Adaptive automation is currently discussed for long-term operations such as intercontinental flights according to instrumental flight rules. We constructed a closed-loop adaptive system for varying the strength of turbulence in a professional simulator. In the experimental condition, nine subjects flew thirty 60-s flight sections, keeping altitude and course while facing different turbulences. The number of nonspecific skin conductance responses was calculated every 60 s and was used for triggering the turbulence strength for the next 60s, dependent on the set point of the individual subject. The other nine subjects belonged to the yoked control condition, flying the same sequence of turbulences as the corresponding experimental subject, however without adaptive automation. Our results indicate that the skin conductance responses of experimental subjects oscillated very close to the individual set point, indicating that the subjects maintained an optimal vigilance/workload level as a result of adaptive control in contrast to yoked control subjects.

Objective Emotional Assessment of Industrial Products

We developed an objective emotional assessment to detect subtle emotion-eliciting properties of products. Electrodermal activity, electrocardiogram, peripheral blood volume, and the activity of three facial muscles (zygomaticus, levator labii, corrugator) are continuously recorded, amended by subjective ratings of various emotional properties induced by interactions with the product. Among the physiological measures, finger pulse volume, skin conductance, and facial muscular activity were most sensitive in revealing tactile effects and their interactions with product worlds being introduced to generate a positive emotional experience. In particular, multivariate evaluation techniques were most successful in revealing subtle differences in products that could not be detected by a traditional sensory assessment.