Responsiveness patterns and handedness differences in bilateral electrodermal asymmetry

Why Behavioral Indicators May Fail to Reveal Mental States: Individual Differences in Arousal-Movement Pattern Relationships

It is commonly assumed that behavior reflects the mental states of individuals. However, recent attempts to detect human states of mind via behavioral indicators have not always been successful; behavioral indicators may be unreliable and invalid. In this study we show that one of the common behavioral indicators, change in the overall amount of movement, correlated well with changes in the skin conductance level (SCL) at the group level, which reflects changes in arousal. At the individual level, however, changes in the SCL were related to movement patterns only in about half of the individuals. It is also noteworthy that the level of movement-SCL correlation was very highly predictable by certain social and cognitive characteristics of the individuals. Our results suggest that behavioral indicators may in many cases fail to predict mental states at the individual level.

Lateralization in human nasal chemoreception: differences in bilateral electrodermal responses related to olfactory and trigeminal stimuli

The study of olfactory lateralization in humans has given rise to many publications, but the findings have often been contradictory. There is growing evidence to suggest that the nature of the olfactory stimulus influences the processes of lateralization. An important factor could be the trigeminal component. Indeed, most odorants simultaneously stimulate both olfactory (CN I) and trigeminal (CN V) systems which differ in terms of their central projections, ipsilaterally for CN I and contralaterally for CN V. The aim of this study was to investigate variations in psychophysiological measurements between a nasal input with low (phenyl ethyl alcohol (PEA)) and high (allyl isothiocyanate (AIC)) intranal trigeminal stimulation. In a first experiment (20 subjects), the intensity, hedonicity and irritation levels of stimulus were tested with a psychophysical evaluation to study the possible influences of perceptual characteristics. A second experiment (37 subjects) used bilateral electrodermal recordings and compared the skin conductance responses (SCRs) for both nasal inputs on either monorhinal and birhinal stimulations. Firstly, the electrodermal activity (EDA) results showed no differences between the two nostrils for PEA as well as AIC, but differences in relation to the type of stimulus, e.g. higher amplitude in response to AIC versus PEA. Secondly, the results indicated bilateral differences in EDA recordings related to the nature of the stimulus and are discussed in terms of hemispheric asymmetric activation.

Quality of odor and olfactory lateralization processes in humans

The study of olfactory lateralization processes in humans has given rise to many publications, but the resulting data have not been homogeneous. Sensorial cerebral asymmetry depends on several factors (nature of task, characteristics of subjects, etc.) and could also depend on the quality of the stimulus, especially in olfaction. This field appears to be widely unexplored and the quality of odor is a complex property. The aim of this study was to investigate variations in psychophysiological measurements (bilateral electrodermal recordings) related to the quality of odors. Electrodermal asymmetries were used as a function of differential hemispheric activation. Two major characteristics of odor were explored, the hedonic valence (pleasant/unpleasant) and the trigeminal component (irritant/non-irritant). The results obtained in a sample of 30 right-handed subjects (15 males and 15 females) showed a predominance of the right hemisphere in the treatment of olfactory information not depending on the quality of odor, except the trigeminal-nerve activation.

Comparison between monorhinal and birhinal olfactory stimulations in bilateral electrodermal recordings

The study of olfactory lateralization in human subjects has given rise to many publications, but the findings have often been contradictory. Most research used either birhinal or monorhinal stimulations, but rarely a comparison between these two types of olfactory input. The aim of this study was to investigate variations in psychophysiological measurements and test each side of the nose and binasal performances. This work used bilateral electrodermal recordings and compared the skin conductance responses (SCRs) for a pleasant odorant (isoamyl acetate) and an unpleasant odorant (triethylamine) in a suprathreshold concentration on 30 dextral subjects (16 females and 14 males). First, the results reported no differences between the two nostrils but differences in electrodermal activity (EDA) in relation to the odorant: 1) higher amplitude in response to unpleasant versus pleasant odorant; 2) no differences between monorhinal and birhinal stimulations for the unpleasant odour but higher amplitude in response to birhinal versus monorhinal for the pleasant odour. Second, the results showed constant bilateral differences in EDA recordings and are discussed in terms of hemispheric asymmetry activation.

Bilateral electrodermal activity: relationships to state and trait characteristics of hemisphere asymmetry

Influences of trait and state characteristics of individual brain lateralization on bilateral electrodermal activity (EDA) were examined. EDA was observed in two different recording conditions: (1) non-specific skin conductance responses (ns.SCRs) were obtained during a stimulus-free recording period of 5 min; and (2) stimulus evoked skin conductance responses (SCRs) were elicited by 80 dichotically presented pairs of pure tones which--at the same time--constituted the items of a test to estimate subject's lateral ear dominance. In addition to ear dominance, degree of right-handedness and hemispheric preference, i.e. preferred direction of conjugate lateral eye movements (CLEMs) were assessed as trait-like characteristics of individual laterality. With respect to asymmetry of ns.SCRs, no effects of the laterality variables were observed. Analysis of SCRs, however, resulted in significant interactions of ear dominance and hemispheric preference with degree of right-handedness indicating higher SCR amplitudes on the hand contralateral to the preferred hemisphere in strong dextrals. Weak right-handers showed a different pattern of bilateral asymmetries, partly in the opposite direction. Additionally, phasic effects of cortical asymmetry on SCRs seem to be modified by trait characteristics of individual laterality. Results underline the importance of precisely controlling degree of handedness in studies of bilateral electrodermal activity. Furthermore, the observed effects support the assumption of cortical influences on EDA, but argue against the existence of a single cortical mechanism modulating asymmetries in the electrodermal system.

Bilateral electrodermal activity: reliability, laterality and individual differences

A first aim of the present study was to estimate the short- and long-term stability of individual response patterns in bilateral electrodermal activity (EDA). A second aim was to examine the relationship of individual brain laterality to both peak amplitude and peak time based electrodermal asymmetry. Additionally, subjects were presented with verbal and spatial tasks to estimate the balance of left/right asymmetry in cerebral activation at time of testing. Finally, the influence of smoking, coffee consumption and subjective circadian phase (morningness/eveningness, subjects' rise time) on bilateral asymmetry and EDA lability was examined. Results indicated moderate to high short-term reliabilities of EDA laterality coefficients, but insufficient long-term stability. Handedness and conjugate lateral eye movements (CLEMs) were not related to asymmetry of EDA, but a significant interaction between CLEM tendency and smoking/nonsmoking on laterality of both EDA parameters was observed. Amount of coffee consumption was also significantly related to electrodermal asymmetry. Analysis of performance data demonstrated that intraindividual shifts of EDA laterality from one recording session to a following one were associated with corresponding shifts in accuracy of verbal/spatial performance. Degree of subjects' electrodermal lability differentiated significantly between speed and accuracy of performance in both verbal and spatial tasks, and was substantially related to subjects' rise time.