Small vessel cerebrovascular disease (SVCD) is one of the most frequent vessel disorders in the aged brain. Among the spectrum of neurological disturbances related to SVCD, oculomotor dysfunction is a not well understood symptom- in particular, it remains unclear whether vascular lesion load in specific brain regions affects oculomotor function independent of cognitive decline in SVCD patients or whether the effect of higher brain function deficits prevails. In this study, we examined a cohort of 25 SVCD patients and 19 healthy controls using video-oculographic eye movement recording in a laboratory environment, computer-based MRI assessment of white matter lesion load (WMLL), assessment of extrapyramidal motor deficits, and psychometric testing.
View Article and Find Full Text PDFBackground: The basal ganglia (BG) are thought to play an important role in the control of eye movements. Accordingly, the broad variety of subtle oculomotor alterations that has been described in Parkinson's disease (PD) are generally attributed to the dysfunction of the BG dopaminergic system. However, the present study suggest that dopamine substitution is much less effective in improving oculomotor performance than it is in restoring skeletomotor abilities.
View Article and Find Full Text PDFWe investigated the relative weighting of vestibular, optokinetic and podokinetic (foot and leg proprioceptive) cues for the perception of self-turning in an environment which was either stationary (concordant stimulation) or moving (discordant stimulation) and asked whether cue weighting changes if subjects (Ss) detect a discordance. Ss (N = 18) stood on a turntable inside an optokinetic drum and turned either passively (turntable rotating) or actively in space at constant velocities of 15, 30, or 60°/s. Sensory discordance was introduced by simultaneous rotations of the environment (drum and/or turntable) at ±{5, 10, 20, 40, 80}% of self-turning velocity.
View Article and Find Full Text PDFBecause of the large overlap and quantitative similarity of eye movement alterations in Parkinson's disease (PD) and multiple system atrophy (MSA), a measurement of eye movement is generally not considered helpful for the differential diagnosis. However, in view of the pathophysiological differences between MSA and PD as well as between the cerebellar (MSA-C) and Parkinsonian (MSA-P) subtypes of MSA, we wondered whether a detailed investigation of oculomotor performance would unravel parameters that could help to differentiate between these entities. We recorded eye movements during sinusoidal pursuit tracking by means of video-oculography in 11 cases of MSA-P, 8 cases of MSA-C and 27 cases of PD and compared them to 23 healthy controls (CTL).
View Article and Find Full Text PDFUsing fMRI we wished to identify brain areas subserving the conversion of velocity signals into estimates of self-displacement (velocity-to-displacement integration, VDI), a function which is a prerequisite for the ability to navigate without landmarks. As real self-motion is not feasible in an fMRI environment, we presented subjects with a ride along a circular path in virtual reality devoid of usable landmarks. We asked subjects to try and feel as if actually moving in the scene and to either detect and count changes in driving speed (V-task) or to estimate the angular displacement achieved during a ride (D-task).
View Article and Find Full Text PDFVertical gaze palsy is a highly relevant clinical sign in parkinsonian syndromes. As the eponymous sign of progressive supranuclear palsy (PSP), it is one of the core features in the diagnosis of this disease. Recent studies have suggested a further differentiation of PSP in Richardson's syndrome (RS) and PSP-parkinsonism (PSPP).
View Article and Find Full Text PDFThe evidence for involvement of extramotor cortical areas in non-demented patients with amyotrophic lateral sclerosis (ALS) has been provided by recent neuropsychological and functional brain imaging studies. The aim of this study was to investigate possible alterations in selective attention, as an important constituent part of frontal brain function in ALS patients. A classical dichotic listening task paradigm was employed to assess event-related EEG potential (ERPs) indicators of selective attention as well as preattentive processing of mismatch, without interference by motor impairment.
View Article and Find Full Text PDFThe perception of angular displacement during self turning is generally based on a combination of redundant signals from different sources. For example, during active turning in a visually structured environment devoid of landmarks, podokinesthetic, vestibular, and optokinetic velocity signals are fused and integrated over time to yield a unitary percept of the ongoing change in angular position ('podokinesthetic' refers to proprioceptive and corollary signals related to leg and foot movement). Previously we have shown that the fusion of two of these afferents improves perceptual accuracy and reliability in comparison to when only one is available.
View Article and Find Full Text PDFAmyotrophic lateral sclerosis (ALS) is a fatal disease, leaving the patient in a partially or completely deafferented state. In an explorative study, we investigated responses to visual socio-emotional stimuli in ALS patients. Pictures from the International Affective Picture System (IAPS) were verbally judged by 12 moderately affected ALS patients with a spinal onset and a slow progression and 18 age-matched controls, and data were compared with psychophysiological responses.
View Article and Find Full Text PDFWe investigated the behaviour of vision-deprived human subjects who try to maintain their horizontal alignment in space on a rotating platform by stepping about their own axis in counter-direction ('podomotor counter-rotation'), and we ask which of two alternative hypotheses best explains this behaviour. (1) The feedback hypothesis assumes that the podomotor counter-rotation is controlled by negative feedback of vestibular signals from the horizontal canals. (2) The reconstruction hypothesis holds that the vestibular cue first is combined with leg proprioceptive afferents signalling the individual's rotation on the platform ('podokinesthetic cue') in a way that reconstructs the platform's motion in space for internal representation; a negative (direction-inverted) copy of this representation then would drive the counter-rotation.
View Article and Find Full Text PDFThe ability to perceive sounds and correctly categorize them within a scale is the result of the interaction between inherited capabilities and acquired rules. If a subject listens to a melody, occasional and unexpected endings of the melody typically evoke characteristic auditory evoked responses in the latency range of 300-400 ms (P300). Also, earlier stages of auditory information processing have been exhaustively investigated by means of mismatch negativity (MMN), a deflection that occurs in the auditory evoked response at a latency of about 200 ms, whenever a deviance is randomly inserted in a series of otherwise equal stimuli.
View Article and Find Full Text PDFWe ask how vestibular and optokinetic information is combined ("fused") when human subjects who are being passively rotated while viewing a stationary optokinetic pattern try to tell when they have reached a previously instructed angular displacement ("targeting task"). Inevitably such a task entices subjects to also draw on cognitive mechanisms such as past experience and contextual expectations. Specifically, because we used rotations of constant angular velocity, we suspected that they would resort, consciously or unconsciously, to extrapolation strategies even though they had no explicit knowledge of this fact.
View Article and Find Full Text PDFOptokinetic circular vection (CV) was investigated in 12 subjects using an optokinetic pattern rotating at 15 degrees /s, 30 degrees /s, or 60 degrees /s, and four viewing conditions: FOL, subjects attentively followed details of pattern; STA, subjects stared at the pattern; SUP, subjects suppressed their optokinetic reflex (OKR) voluntarily (this was facilitated by a white, featureless band at eye level which separated the pattern in an upper and lower half); FIX, subjects suppressed OKR by fixating at a stationary fixation point (FP). To quantify CV, subjects pressed a signal button each time they felt rotated by a further 90 degrees; OKR was recorded by electro-oculography. Voluntary suppression of OKR was achieved during 2-70% of stimulus duration.
View Article and Find Full Text PDFWhen observers step about their vertical axis ("active turning") without vision they dispose of essentially two sources of information that can tell them by how much they have turned: the vestibular cue which reflects head rotation in space and the "podokinesthetic" cue, a compound of leg proprioceptive afferents and efference copy signals which reflects the observer's motion relative to his support. We ask how these two cues are fused in the process leading to the perception of self-displacement during active turning. To this end we compared the performance of observers in three angular navigation tasks which differed with regard to the number and type of available motion cues: (1) Passive rotation, vestibular cue ( ves) only; observers are standing on a platform which is being rotated.
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