The present study demonstrates that, for the development of persistent psychogenic dizziness after a peripheral vestibular disorder, the fear of bodily sensations is only relevant in interaction with the initial severity of dizziness experienced during the acute organic episode. To prevent development of persistent psychogenic dizziness, we feel that our results indicate the need to screen patients with vestibular disorders for at-risk status and offer them psychological support to deal with their symptoms.

The increased intratest variability in older subjects probably resulted from nonspecific changes in alertness and attention commonly occurring with aging, whereas the decreased gain of smooth pursuit and saccades with increasing stimulus magnitude most likely resulted from age-related neural degeneration in specific visuomotor pathways.

In this study we compare the results of quantitative oculomotor function testing in patients with Friedreich's ataxia (FA), olivopontocerebellar atrophy (OPCA) and cerebello-olivary atrophy (CA). Common features in all three syndromes included gaze-evoked nystagmus, saccade dysmetria and prolonged saccade reaction times. Patients with FA showed a characteristic combination of frequent saccadic intrusions, especially ocular flutter, relatively preserved optokinetic nystagmus (OKN) and smooth pursuit, and impaired vestibulo-ocular reflex (VOR) responses. In patients with CA saccadic intrusions were infrequent, OKN and smooth pursuit were severely impaired and VOR gain was normal or increased. Results in OPCA were more variable. When present, slowing of saccades or the combined loss of pursuit and vestibular function were characteristic for OPCA. The ability to suppress the VOR with a head fixed target was relatively preserved in FA, normal to moderately impaired in OPCA and always severely impaired in CA. We conclude that oculomotor testing is useful in the differential diagnosis of the progressive ataxia syndromes.

Modifications of the Wisconsin Card Sorting Test were established. In these new task variants, participants were asked to exert sequential control over attentional sets or over intentional sets (task domain factor). Attentional set shifting requires changing the priorities by which sensory stimuli are selected, whereas intentional set shifting requires changing the priorities by which motor responses are selected. Auditory stimuli that signaled to maintain or shift set were presented immediately before (precuing) or after (postcuing) the selection of cards (cue timing factor). Twenty-four healthy young individuals participated. Performance data (response times, error percentages) indicated that intentional tasks were easier to perform than attentional tasks. The electroencephalogram was recorded during task performance, and the N1, medial frontal negativity (MFN), P3a, and sustained potential (SP) components of the cue event-related brain potentials (ERPs) were analyzed. Irrespective of the task domain, shift precues led to increased N1 amplitudes compared to shift postcues. When intentional sets had to be shifted, the MFNs in the postcuing condition were more pronounced than in the precuing condition. On the other hand, shifts of attentional sets resulted in a more prominent P3a in response to postcues compared to precues. Irrespective of the task domain, the shift effect that was evident in SPs was more pronounced in precue ERPs compared to postcue ERPs. We conclude that ERPs provide valid measures to empirically constrain theories about the neural mechanisms of cognitive control. The domain hypothesis of the fractionation of the neural mechanisms of cognitive control is introduced.