The association of macro- and microstructure of the corpus callosum and language lateralisation

The present study aimed to examine how differences in functional lateralisation of language are related to interindividual variations in interhemispheric connectivity. Utilising an fMRI silent word-generation paradigm, 89 left- and right-handed subjects were subdivided into four lateralisation subgroups. Applying morphological and diffusion-tensor MRI, midsagittal cross-sectional area as well as quantitative measures of molecular diffusion (anisotropy, mean diffusion) of the corpus callosum were determined to assess interhemispheric connectivity. Statistical analyses revealed group differences in molecular diffusion but not in callosal size, which may be interpreted to reflect a stronger and/or faster interhemispheric connection in strongly left-lateralised subjects as compared to moderately left-lateralised, bilateral, or moderately right-lateralised subjects.     

Perception of the head transversal plane and the subjective horizontal during gondola centrifugation

The subjective visual horizontal (SVH) and the subjective head transversal plane (STP) were measured by means of an adjustable luminous line in darkness during centrifuging. Subjects (N = 10) were seated upright, facing forward in a swing-out gondola. After acceleration of the centrifuge to 2G (vectorial sum of the earth's gravity and the centrifugal force; gondola inclination 60 degrees), subjects had to set the line either so that it was perceived as gravitoinertially horizontal (SVH) or so that it was perceived as parallel with the transversal ("horizontal") plane of the head (STP). Initially after acceleration, the SVH was tilted with respect to the gravitoinertial horizontal of the gondola (M = 16.6 degrees). This tilt was compensatory with respect to the gondola inclination. However, the STP was tilted in the opposite direction (M = 12.4 degrees), which might suggest a vestibular-induced distortion of the mental representation of one's own body. Similar results were obtained when measuring the subjective visual vertical (SVV) and the subjective midsagittal plane (SSP) in 5 subjects. The perceived roll angle (obtained as SVH-STP or SVV-SSP) was considerably larger than had previously been reported. Time constants for exponential decay of the tilt of the SVH or SVV were often 2-3 min, indicating a memory for semicircular canal information on changes in head orientation--a position-storage mechanism.     

Zum referat Grelling-Oppenheim

Ohne Zusammenfassung     

Behold the wrath: Psychophysiological responses to facial stimuli

The complex musculature of the human face has been shaped by natural selection to produce gestures that communicate information about intentions and emotional states between senders and receivers. According to the preparedness hypothesis, different facial gestures are differentially prepared by evolution to become associated with different outcomes. As attested by psychophysiological responses in Pavlovian conditioning experiments, expressions of anger and fear more easily become signals for aversive stimuli than do expression of happiness. Consistent with the evolutionary perspective, the superior conditioning to angry faces is stronger for male than for female faces, for adult than for child faces, and for faces directed toward the receiver rather than directed away. Furthermore, it appears to be primarily located in the right cerebral hemisphere. The enhanced autonomic activity to angry faces signaling electric shock is not mediated by conscious cognitive activity, but is evident also when recognition of the facial stimulus is blocked by backward masking procedures. Similarly, conditioned responses can be established to masked angry, but not to masked happy faces. Electromyographic measurement of facial muscle activity reveals a tendency for emotional facial expression to rapidly and automatically elicit its mirror image in the face of the receiver, typically accompanied by the appropriate emotional experience. The research reviewed in this paper supports the proposition that humans have been evolutionarily tuned to respond automatically to facial stimuli, and it is suggested that such early automatic reactions shape the subsequent conscious emotional processing of the stimulus.The responsibility for this paper is shared equally between the authors. The research reviewed in the paper has been supported by separate grants to both authors from the Swedish Council for Research in the Humanities and Social Sciences, The Swedish Council for the Coordination and Planning of Research, and the Bank of Sweden Tercentennial Fund.     

Electrocortical Responses to ecologically relevant visual stimuli among professional drivers with and without cardiovascular disease

Electrocortical responses were assessed using two simulated aspects of visual signals encountered in traffic: the Glare Pressor Test (GPT) and Event-Related Potential Avoidance Task (ERPAT) among four groups of male professional drivers: 12 with ischemic heart disease (IHD), 12 hypertensives, 10 borderline hypertensives, 34 who were apparently healthy and 23 nonprofessional driver healthy control subjects. The blood pressure (BP) responses immediately after the ERPAT were also measured. There was a significant between groups effect for the amplitude of the target N2 component in the ERPAT (p=0.02), with the lowest means among the drivers with IHD and the highest among those with hypertension. Drivers with IHD also showed the highest diastolic BP reactivity to the ERPAT. Significantly more than the expected number of drivers with IHD failed to recover alpha activity after the first glare impulse of the GPT. Professional drivers who failed to recover baseline levels of alpha activity after the GPT showed a significantly smaller N2 amplitude compared to those who recovered (p=0.01). There was a positive correlation between abundance of alpha activity at rest with P300 amplitude (p=0.02). An inverse relation was found between number of work hours behind the wheel and the amplitude of the target P300 (p=0.04). Results are interpreted in light of recent advances concerning integrative mechanisms of defence versus vigilance response patterns. The findings in this study justify further applications of these psychophysiologic methods to assess the relationship between simulated signals of the work environment and mechanisms of cardiac risk in this occupational group.     

Mother-child communication about location: giving and following directions for finding hidden objects

We conducted 2 experiments to examine how mothers structure directions to young children for finding hidden objects and how young children use these directions to guide their searches. In Experiment 1, we examined the reference frames mothers use to communicate with their 2.5-, 3-, and 3.5-year-old children about location by asking mothers to verbally disambiguate a target hiding container from an identical nontarget hiding container. We found that mothers' reference frame use was primarily governed by the relative proximity of the target container to the landmark and themselves. Older children were more successful in following directions than were younger children, and children were more likely to search successfully in response to a person than to a landmark frame of reference. In Experiment 2, we further investigated how 3-year-old children follow directions involving person and landmark frames of reference by asking mothers to use either only themselves or only the landmark to describe the target location. Children in the person reference frame condition successfully followed their mother's directions when the target was relatively close to the mother, but not when the target was relatively far from the mother. Children in the landmark reference frame condition were at chance regardless of the relative proximity of the target to the landmark. The discussion focuses on the roles of spatial proximity and reference frames in mother-child spatial communication.