Dept. of Neurology

Objective: Xenomelia, that is, the nonacceptance of one’s own limb, is an intriguing but little understood
condition. We sought to further test the most prominent neuroscientific hypothesis that suggests
xenomelia results from a breakdown in multisensory integration for the affected body part. Method: A
“rubber foot illusion” paradigm was developed and tested in healthy participants and in individuals with
a desire for left foot amputation (xenomelia). Behavioral and physiological responses quantified illusory
ownership of a fake foot after synchronous and asynchronous stroking of a visible rubber foot and the
subject’s own hidden foot. Results: Healthy participants (n  15) showed a rubber foot illusion similar
to the well-known rubber hand illusion. Individuals with xenomelia (n  9) experienced the rubber foot
illusion in a way comparable to healthy controls. The only difference in the individuals with xenomelia
was an increase in the vividness of the illusion for the undesired limb. This vividness of the illusion
correlated positively with the strength of amputation desire. Conclusion: These findings might reflect the
malleable sense of the body in xenomelia and suggest a weakened representation of the affected body
part. These findings may support the use of multisensory stimulation in therapeutic settings

Introduction: At the centenary of research on anosognosia, the time seems ripe to supplement work in anosognosic patients with empirical studies on nosognosia in healthy participants. To this end, we adopted a signal detection framework to investigate the lateralized recognition of illness words e an operational measure of nosognosia e in healthy participants. As posi- tively biased reports about one's current health status (anosognosia) and future health status (unrealistic optimism) have both been associated with deficient right hemispheric func- tioning, and conversely with undisturbed left hemispheric functioning, we hypothesised that more optimistic participants would adopt a more conservative response criterion, and/ or display less sensitivity, when identifying illnesses in our nosognosia task; especially harmful illnesses presented to the left hemisphere via the right visual field.
Material and methods: Thirty-two healthy right-handed men estimated their own relative risk of contracting a series of illnesses in the future, and then completed a novel computer task assessing their recognition of illness names presented to the left or right visual field. To check that effects were specific to the recognition of illness (rather than reflecting recognition of lexical items per se), we also administered a standard lateralized lexical decision task.
Results: Highly optimistic participants tended to be more conservative in detecting ill- nesses, especially harmful illnesses presented to the right visual field. Contrary to expec- tation, they were also more sensitive to illness names in this half-field.
Conclusions: We suggest that, in evolutionary terms, unrealistic optimism may be an adaptive trait that combines a high perceptual sensitivity to threat with a high threshold for acknowledging its presence. The signal detection approach to nosognosia developed here may open up new avenues for the understanding of anosognosia in neurological patients.

The purpose of the present study was to examine the impact of the congenital absence of one hand on cortical organization of the sensorimotor cortex (S1/M1). We investigated the tongue representation in S1/M1 in nine participants with normally developed limbs, comprising the control group, and in eight persons with a congenitally completely missing hand (i.e. unilateral hand amelia). All participants were examined by fMRI while performing horizontal tongue movements. The significantly activated clusters covering S1/M1 in both hemispheres were analyzed with respect to the number and intensity of activated voxels, as well as the location of the activation. In the right-handed control group, the number of activated voxels was significantly higher in the left as compared to the right hemisphere demonstrating a clear left hemispheric motor dominance for horizontal tongue movements. In the amelic individuals, no such hemispheric lateralization effect was observed. The neural activation pa...

Exceptional experiences (EE) are experiences that deviate from ordinary experiences, for example precognition, supernatural appearances, or déjà vues. In spite of the high frequency of EE in the general population, little is known about their effect on mental health and about the way people cope with EE. This study aimed to assess the quality and quantity of EE in persons from the Swiss general population, to identify the predictors of their help-seeking, and to determine how many of them approach the mental health system. An on-line survey was used to evaluate a quota sample of 1580 persons representing the Swiss general population with respect to gender, age, and level of education. Multinomial logistic regression was applied to integrate help-seeking, self-reported mental disorder, and other variables in a statistical model designed to identify predictors of help-seeking in persons with EE. Almost all participants (91%) experienced at least one EE. Generally, help-seeking was mor...

Dopamine (DA) is suggested to improve perceptual and cognitive decisions by increasing the signal-to-noise ratio. Somewhat paradoxically, a hyperdopaminergia (arguably more accentuated in the right hemisphere) has also been implied in the genesis of unusual experiences such as hallucinations and paranormal thought. To test these opposing assumptions, we used two lateralized decision tasks, one with lexical (tapping left-hemisphere functions), the other with facial stimuli (tapping right-hemisphere functions). Participants were 40 healthy right-handed men, of whom 20 reported unusual, "paranormal" experiences and beliefs ("believers"), whereas the remaining participants were unexperienced and critical ("skeptics"). In a between-subject design, levodopa (200 mg) or placebo administration was balanced between belief groups (double-blind procedure). For each task and visual field, we calculated sensitivity (d') and response tendency (criterion) derived from signal detection theory. Results showed the typical right visual field advantage for the lexical decision task and a higher d' for verbal than facial stimuli. For the skeptics, d' was lower in the levodopa than in the placebo group. Criterion analyses revealed that believers favored false alarms over misses, whereas skeptics displayed the opposite preference. Unexpectedly, under levodopa, these decision preferences were lower in both groups. We thus infer that levodopa (1) decreases sensitivity in perceptual-cognitive decisions, but only in skeptics, and (2) makes skeptics less and believers slightly more conservative. These results stand at odd to the common view that DA generally improves signal-to-noise ratios. Paranormal ideation seems an important personality dimension and should be assessed in investigations on the detection of signals in noise.