Biomedical subjects

Wolfgang Heide

Publications and source records attributed to Wolfgang Heide.

15 recordsLinked to original sources

PubMed2006

Different extraretinal neuronal mechanisms of smooth pursuit eye movements in schizophrenia: An fMRI study.

Smooth pursuit eye movements (SPEM) are necessary to follow slowly moving targets while maintaining foveal fixation. In about 50% of schizophrenic patients SPEM velocity is reduced. In this study we were interested in identifying the cortical mechanisms associated with extraretinal processing of SPEM in schizophrenic patients. During condition A, patients and healthy subjects had to pursue a constantly visible target (10 degrees /s). During condition B the target was blanked out for 1000 ms while subjects were instructed to continue SPEM. Eye movement data were assessed during scanning sessions by a limbus tracker. During condition A, reduced SPEM velocity in patients was associated with reduced activation of the right ventral premotor cortex and increased activation of the left dorsolateral prefrontal cortex, the right thalamus and the Crus II of the left cerebellar hemisphere. During condition B, SPEM velocity was reduced to a similar extent in both groups. While in patients a decrease in activation was observed in the right cerebellar area VIIIA, the activation of the right anterior cingulate, the right superior temporal cortex, and the bilateral frontal eye fields was increased. The results implicate that schizophrenic patients employ different strategies during SPEM both with and without target blanking than healthy subjects. These strategies predominantly involve extraretinal mechanisms.

Adult↗

PubMed2006

Evidence from increased anticipation of predictive saccades for a dysfunction of fronto-striatal circuits in obsessive-compulsive disorder.

In obsessive-compulsive disorder (OCD), a dysfunction of neuronal circuits involving prefrontal areas and the basal ganglia is discussed that implies specific oculomotor deficits. Performance during reflexive and predictive saccades, antisaccades and predictive smooth pursuit was compared between patients with OCD (n=22), patients with schizophrenia (n=21) and healthy subjects (n=24). Eye movements were recorded by infrared reflection oculography. In both patient groups, higher frequencies of anticipatory saccades with reduced amplitudes in the predictive saccade task were observed. Additionally, reduced smooth pursuit eye velocity and increased frequencies of saccadic intrusions during smooth pursuit as well as increased error rates in the antisaccade task were demonstrated for patients suffering from schizophrenia. Patients with OCD and schizophrenia revealed different patterns of oculomotor impairment: whereas increased anticipation of predictive saccades provides evidence for a dysfunction of the circuit between the frontal eye field and the basal ganglia in both groups, results from the antisaccade task imply additional deficits involving the dorsolateral prefrontal cortex in schizophrenic patients. Furthermore, the cortical network for smooth pursuit (especially the frontal eye field) is also assumed to be disturbed in schizophrenia.

Adult↗

PubMed2006

Eye-hand coordination in essential tremor.

Patients with essential tremor (ET) or with cerebellar lesions have in common oculomotor abnormalities, with the exception of saccadic eye movements, which do not seem to be involved in ET. Since grasping is prolonged in ET and might be related to saccadic dysmetria, we tested whether simultaneous hand pointing could unmask it. Twelve ET patients and 14 controls performed saccades with and without simultaneous pointing movements to the same targets, and with and without a gap between the disappearance of the fixation point and the appearance of the target. Eye movements were recorded with the magnetic search-coil method, hand movements with an ultrasound-emitting probe. ET patients did not have saccadic dysmetria, and contrary to normal subjects their saccadic latency did not decrease during combined eye-hand movements compared with saccades performed in isolation. Hand movements had a longer duration in ET patients, with decreased peak acceleration, an increased latency of the peak velocity, and peak deceleration. In conclusion, this first study on eye-hand coordination in ET revealed abnormal kinematic changes in the early phase of pointing movements. These changes might be related to cerebellar disease but they are independent of the intention tremor component and saccade performance.

Adult↗

PubMed2005

Parametric modulation of cortical activation during smooth pursuit with and without target blanking. an fMRI study.

Smooth pursuit eye movements (SPEM) are performed to track slowly moving visual targets and are accompanied by saccades whenever foveal representation is lost. In the present study, we correlated the cerebral activation as assessed by functional magnetic resonance imaging with parameters of eye movement performance in order to determine the cortical areas involved in the retinal and extraretinal processing of maintaining smooth pursuit velocity (SPV) and generating saccades in 16 healthy males. The stimulus consisted of a target moving at a constant velocity of 10 degrees/s with and without target blanking. During constant target presentation, SPV was positively correlated with the BOLD signal in the right V5 complex and negatively correlated with the BOLD response in the left dorsolateral prefrontal cortex (DLPFC). In the condition with target blanking, additional negative correlations with SPV were found in the left frontal eye field (FEF), the left parietoinsular vestibular cortex (PIVC) and the left angular gyrus. Saccadic frequency was negatively correlated with activations of the right mesial intraparietal sulcus (IPS) during both conditions and the right premotor area during continuous target presentation. We conclude that V5 is directly related to the maintenance of an optimal smooth pursuit velocity during visual feedback, whereas the FEF, PFC, angular gyrus and PIVC are involved in reconstitution and prediction whenever SPV decreases, especially during maintenance of smooth pursuit in the absence of a visual target. Furthermore, we suggest that parietal areas are related to the suppression of saccades during smooth pursuit.

Adult↗

PubMed2005

Cerebellar infarction affects visual search.

Recent studies have discussed the role of the cerebellum in not only motor but also cognitive functions, and in particular, fronto-executive operations. Similar to a previous study on hemineglect patients, we recorded eye movements during a visual search task to investigate patients with isolated infarction of the cerebellum compared with controls. Patients showed longer search durations, associated with mild saccadic dysmetria, longer single fixation durations and a higher number of repeated fixations of items. Systematic search strategies were preserved, but less frequent in patients. In conclusion, though basic mechanisms of visual search including spatial memory were not affected by cerebellar lesions, patients' search behaviour was slower and less efficient, indicating a mild deficit of visual attention and motor planning.

Adolescent↗

PubMed2005

Differential effects of sleep deprivation on saccadic eye movements.

STUDY OBJECTIVES: This study was designed to show the influence of sleep deprivation on different types of saccadic eye movements. DESIGN: Performance of saccadic eye movements was compared after normal sleep and sleep deprivation in a randomized, within-subjects paradigm. Parameters of voluntary and reflexive saccades were measured before and after experimental nights and after a night of recovery sleep. Additionally, subjects spent 1 adaptation night in the laboratory before the experiments. SETTING: Experiments took place under controlled laboratory conditions. PARTICIPANTS: Fifteen healthy male volunteers (aged 19-30 years). INTERVENTIONS: Each subject participated in 1 night of sleep deprivation followed by a night of recovery sleep and, on another occasion, in 2 successive nights of undisturbed sleep. MEASUREMENTS AND RESULTS: Horizontal prosaccades, antisaccades, and memory-guided saccades were recorded by means of electrooculography. They were analysed semiautomatically with respect to accuracy, peak velocity, and latency. Peak velocity was significantly reduced in all saccade tasks after 1 night of sleep deprivation but recovered after another night of sleep. Latency was prolonged after sleep deprivation only for memory-guided saccades; accuracy showed a decrease after 1 night without sleep only for prosaccades. CONCLUSIONS: Sleep deprivation has a general impairing effect on the peak velocity of saccades, reflecting possible dysfunction at the level of the brainstem reticular formation. Deficits of accuracy and latency point to dysfunction of specific brain sites such as the supplementary eye field and cerebellum, whereas the cardinal functions of the frontal and parietal eye fields were not affected. These results suggest the possibility of measuring fatigue by means of saccadic parameters, especially saccadic peak velocity.

Adult↗

PubMed2004

Reduced neuronal activity in the V5 complex underlies smooth-pursuit deficit in schizophrenia: evidence from an fMRI study.

Smooth-pursuit eye movements are the essential tool for a clear and stable visual perception of our environment by matching eye velocity to the velocity of moving objects. However, in about 50% of schizophrenic patients, this ability is disturbed. To reveal the cortical mechanisms that underlie this deficit, eye velocity-related neuronal activity was analyzed by functional magnetic resonance imaging (fMRI). Blocks of constant velocity ramps (10 degrees/s) were presented to 17 patients with schizophrenia and 16 matched controls while assessing smooth-pursuit velocity (SPV) during scanning sessions. Using random-effects analysis, the parametric modulation of brain hemodynamic responses related to SPV was compared between both groups. In schizophrenic patients, reduced SPV was significantly correlated with a focal decrease of the hemodynamic response in the V5 complex (t = 4.21, P(FWE-corrected) = 0.005). Our results provide direct evidence for reduced neuronal activity in V5 as one major factor underlying abnormal SPV in schizophrenia and suggest impaired motion perception. They confirm hypotheses about a V5 deficit derived from psychophysiological studies with schizophrenic patients in which deficient motion perception (especially velocity discrimination) was associated with impaired smooth-pursuit performance.

Adult↗

PubMed2004

Activation of cerebellar hemispheres in spatial memorization of saccadic eye movements: an fMRI study.

What mechanisms allow us to direct a precise saccade to a remembered target position in space? The cerebellum has been proposed to be involved not only in motor and oculomotor control, but also in perceptual and cognitive functions. We used functional MRI (Echoplanar imaging at 1.5 T) to investigate the role of the cerebellum in the control of externally triggered and internally generated saccadic eye movements of high and low memory impact, in six healthy volunteers. Memory-guided saccades to remembered locations of 3 targets (triple-step saccades) in contrast to either central fixation or to visually guided saccades activated the cerebellar hemispheres predominantly within lobuli VI-crus I. The same areas were activated when an analogous visuospatial working memory task was contrasted to the triple-step saccades. Visually guided saccades activated the posterior vermis and the triple-step saccades, contrasted to the working memory task, activated predominantly the posterior vermis and paravermal regions. Our data confirm the primary involvement of the posterior vermis for visually-triggered saccadic eye movements and present novel evidence for a role of the cerebellar hemispheres in the mnemonic and visuospatial control of memory-guided saccades.

Adult↗

PubMed2004

Focal dystonia as a presenting sign of spinocerebellar ataxia 17.

We report on the clinical manifestation of spinocerebellar ataxia 17 (SCA17) in 3 members of a German family, in whom the pathological repeat expansion in the TATA-binding protein gene ranged from 53 to 55 repeats (normal: 29-42). The main clinical features were focal dystonia as presenting sign, followed by cerebellar ataxia, and, in the later course of one case, dementia and marked spasticity with signs of cerebellar and cerebral atrophy on brain computed tomography (CT) scan. In conclusion, SCA17 mutations should be considered in the differential diagnosis of focal dystonia.

Adult↗

PubMed2004

Eye movements and psychiatric disease.

PURPOSE OF REVIEW: During the past year a number of studies have been published on eye movement dysfunction in patients with psychiatric disease. According to the mainstream of modern neuropsychiatric research, these studies cover either genetic aspects or the results of pharmacological manipulation. RECENT FINDINGS: A few studies addressed impaired smooth pursuit eye movements (eye tracking dysfunction) in unaffected relatives of psychiatric patients, and were important in excluding non-specific effects (e.g. medication) and isolating genetic predisposition to the disease. This predisposition could be demonstrated in families of schizophrenic patients irrespective of whether the index case was sporadic or familial. One large study demonstrated pathological distributions of various parameters of smooth pursuit eye movement performance in groups of schizophrenic patients and their relatives. However, another study challenged the specificity of eye tracking dysfunction as a trait marker for schizophrenia by showing that its prevalence was identical among relatives of patients with affective disorder and schizophrenia. Eye tracking dysfunction was associated with two gene polymorphisms that interfere with dopamine metabolism and are thus reasonable candidate genes for the predisposition to schizophrenia. The influence of nicotine and neuroleptic drugs on eye movement performance was studied in schizophrenic patients. Nicotine improved smooth pursuit performance in three studies, one of which attributed this finding to enhanced attention. Two groups of schizophrenic patients treated with two different atypical neuroleptic drugs, risperidone and olanzapine, did not differ in a battery of saccadic tasks. SUMMARY: Eye movements provide an important tool to measure pharmacological effects in patients and unravel genetic traits in psychiatric disease.

Dopamine↗

PubMed2004

Cortical mechanisms of smooth pursuit eye movements with target blanking. An fMRI study.

Smooth pursuit eye movements are evoked by retinal image motion of visible moving objects and can also be driven by the internal representation of a target due to extraretinal mechanisms (e.g. efference copy). To delineate the corresponding neuronal correlates, functional magnetic resonance imaging at 1.5 T was applied during smooth pursuit at 10 degrees /s with continuous target presentation and target blanking for 1 s to 16 right-handed healthy males. Eye movements were assessed during scanning sessions by infra-red reflection oculography. Smooth pursuit performance was optimal when the target was visible but decreased to a residual velocity of about 30% of the velocity observed during continuous target presentation. Random effects analysis of the imaging data yielded an activation pattern for smooth pursuit in the absence of a visual target (in contrast to continuous target presentation) which included a number of cortical areas in which extraretinal information is available such as the frontal eye field, the superior parietal lobe, the anterior and the posterior intraparietal sulcus and the premotor cortex, and also the supplementary and the presupplementary eye field, the supramarginal gyrus, the dorsolateral prefrontal cortex, cerebellar areas and the basal ganglia. We suggest that cortical mechanisms such as prediction, visuo-spatial attention and transformation, multimodal visuomotor control and working memory are of special importance for maintaining smooth pursuit eye movements in the absence of a visible target.

Adult↗

PubMed2003

Mirror apraxia affects the peripersonal mirror space. A combined lesion and cerebral activation study.

Mirror apraxia is a condition in which patients with lesions of the posterior parietal cortex have deficits in reaching to objects presented through a mirror. The aim of the present study was to investigate possible mechanisms underlying this disorder. First, we addressed the question of whether mirror apraxia is exhibited to the same extent in peripersonal and in body space. Four patients with lesions of the posterior parietal lobe on either side and with marked mirror apraxia were required to reach for objects that were presented to them through a mirror and located either in body space (i.e. on the body surface) or in peripersonal space (i.e. in the reaching distance). Whereas reaching for objects located in body space was flawless in all patients, the performance deteriorated when the same objects were transferred to the peripersonal space. Although the objects were located only a few centimetres above the body surface, the patients reached towards the virtual object in the mirror. Based on these results we suggest that mirror apraxia may originate from a dissociation between the representations of body schema and peripersonal space and that objects located on the body surface become integrated into the body schema. In the second part of the study, using positron emission tomography study (PET), we studied the cerebral activation pattern during reaching to objects presented through a mirror in the peripersonal space in healthy subjects. The results show that increased neural activity in the anterior part of the intraparietal sulcus and in the dorsal premotor cortex was bound to the transformation of the target position from the mirror space to the real space. In contrast, the activity related to object localization in the mirror occurred at the parieto-occipital junction. Both mirror and arm transformation involved the medial posterior part of the superior parietal lobule, putatively area V6a. The results demonstrate that acting through a mirror is processed in a number of cortical areas of the dorsal stream.

Aged↗

PubMed2003

Effects of same- and different-modality cues in a Posner task: extinction-type, spatial, and non-spatial deficits after right-hemispheric stroke.

The response delay to left target stimuli preceded by right-side cues, first described by Posner et al. [J. Neurosci. 4 (1984) 1863-1874] appears to be a stable marker of right-parietal injury. However, only few studies compared patients' performance to age-matched controls. Furthermore, only few studies compared visual and auditory stimuli in this task. Therefore, two groups of right-hemisphere stroke patients, with and without left visual hemineglect, and a healthy control group were studied in three versions of Posner's paradigm. Visual or auditory target stimuli were presented to the subject's left or right, following a visual or auditory cue by 150 ms. The classical 'extinction-type' effect, an increase in missing responses for right visual cue/left visual target, was specifically observed in neglect patients. In the same condition, an 'extinction-type' response delay was present in patients with neglect and in those without neglect. No such delay occurred in any group when cues were auditory. Specifically in neglect patients, response times were generally longer for left than for right visual targets, regardless of cue side and of cue modality. Response times were generally prolonged in neglect patients regardless of target modality. This suggests that three components impair neglect patients' performance in this paradigm: a non-spatial, supramodal deficit, a global, neglect-type deficit of the contralesional hemi-field, and the extinction-type impairment. The latter two deficits appear to be most marked within the visual domain.

Acoustic Stimulation↗

PubMed2003

Modulation of cerebellar activation by predictive and non-predictive sequential finger movements.

We investigated the modulation of cerebellar activation by predictive and non-predictive sequential finger movements. It is hypothesized that the prediction of desired movement sequences and adaptation to new movement parameters is mediated by the cerebellum. Using functional MRI at 1.5 T, seven normal subjects performed sequential finger to thumb opposition movements, either in predictive (repeatedly 2,3,4,5) or non-predictive (randomized) fashion at a constant frequency of 1 Hz. Performance and error rates were monitored by simultaneous recording of the finger movements. Predictive sequential finger opposition movements activated a cerebellar network including the lobuli IV-VI ipsilateral to the movements, the contralateral lobuli IV-VI, the vermis, and lobuli VIIB-VIII ipsilaterally. Non-predictive compared to predictive finger opposition movements activated a broader area within the ipsi- and contralateral anterior cerebellum, lobuli IV-VI, the vermis, and the ipsilateral lobuli VIIB-VIII. Additional activation foci were found in the contralateral lobuli VIIA and VIIB-VIII. Our study demonstrates a modulated information processing within the cerebellar network dependent on the predictability of movement sequences.

Brain Mapping↗

PubMed2002

Effects of stimulus-induced saccades on manual response times in healthy elderly and in patients with right-parietal lesions.

Response delays of hemi-neglect patients to invalidly cued left targets in Posner's visual cueing task have been interpreted as reflecting disorders of covert attention, although shifts of overt attention have so far not been systematically measured in patients performing this task. Therefore, we measured saccades (i.e., fast goal-directed eye movements) induced by cues and targets in this task in ten patients with lesions of the right posterior parietal cortex and in age-matched healthy subjects. Participants were not aware that their saccades were studied. Of greatest interest was whether the presence or absence of saccades would modify the patients' response delay with invalidly cued left targets. In both groups, saccades occurred in many trials, key-press responses were slower in saccade trials than in no-saccade trials, and the delay by invalid cues was larger in saccade trials. The patients' responses were in particular delayed if preceded by saccades to the left. Their delay to invalidly cued left targets almost doubled (144 ms vs 76 ms) when only saccade trials were analyzed compared to when only no-saccade trials were analyzed. Thus, overt shifts (saccades) have a similar but larger effect on manual responses than covert shifts of attention. In particular, overt shifts make a considerable contribution to the patients' pathological delay of responses to invalidly cued left targets.

Aged↗