Purkinje cells in awake behaving animals operate at the upstate membrane potential.
Explore the source record for details and available documents.
Anesthesia, General↗
Biomedical subjects
Maarten A Frens
Publications and source records attributed to Maarten A Frens.
Saccade adaptation in Williams-Beuren Syndrome.
PURPOSE: To investigate the capacity for rapid saccade adaptation in Williams-Beuren Syndrome (WBS), a genetic neurodevelopmental disorder, in which it has been observed that saccadic accuracy is severely reduced. METHODS: Saccade amplitude modification was elicited by backward steps (30% of target eccentricity) during the primary saccade in a classic saccade-adaptation paradigm. RESULTS: Patients with WBS showed a significant decrease in saccade amplitude. Furthermore, we observed that higher saccade accuracy before adaptation was related to more adaptation. CONCLUSIONS: The increased variability in motor performance does not abolish the ability for saccadic adaptation in subjects with WBS. Our results are congruent with the notion that part of the behavioral deficits observed in WBS may have a cerebellar origin.
Adaptation, Ocular↗
Interaction between ocular stabilization reflexes in patients with whiplash injury.
PURPOSE: In the past few decades, the automobile has become an increasingly more popular means of transport, which has led to an increasing number of rear-end collisions and consequently has resulted in more patients with whiplash-associated disorders (WADs). Recently, it was found that the gain of one of the ocular stabilization reflexes-the cervico-ocular reflex (COR)-is elevated in patients with whiplash injury. The COR responds to proprioceptive signals from the neck and acts in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) to preserve stable vision on the retina during head motion. Therefore, an investigation was conducted to determine whether the reported elevation of the COR in WADs is accompanied by changes in VOR or OKR. METHODS: Eye movements of 13 patients and 18 age-matched healthy controls were recorded with an infrared eye-tracking device. RESULTS: Analysis confirmed a significant increase in COR gain in whiplash patients. Meanwhile the VOR and OKR gains remained the same. No correlation was found between the gains of the reflexes in individual patients. This is in contrast to earlier observations in elderly subjects and subjects with labyrinthine defects, who showed increases in COR gain and decreases in VOR gain. CONCLUSIONS: Impaired neck motion, altered proprioception of the neck, or disorganization in the process of VOR plasticity could explain the lack of change in VOR gain.
Adult↗
Inhibition of return is not a foraging facilitator in saccadic search and free viewing.
The ability to search and scan the environment effectively is a prerequisite for spatial behavior. A longstanding theory proposes that inhibition of previously attended loci (Inhibition of return; IOR) serves to facilitate exploration by increasing the likelihood to inspect new areas instead of returning to locations that have been inspected before. In this eye movement study we tested whether we could find evidence in favor of this hypothesis. Here we report that IOR does occur during search and free viewing, because we found increased fixation times preceding return saccades (eye movements that return to previously fixated locations). Meanwhile we observed no influence of IOR on the search strategy. Rather than the predicted low number we found many return saccades. Therefore, IOR does not serve as a foraging facilitator in saccadic search and free viewing. We hypothesize that IOR is an intrinsic aspect of shifting attention and gaze direction and furthermore that it is not always advantageous to prevent return saccades.
Attention↗
Mechanisms underlying cerebellar motor deficits due to mGluR1-autoantibodies.
Patients with Hodgkin's disease can develop paraneoplastic cerebellar ataxia because of the generation of autoantibodies against mGluR1 (mGluR1-Abs). Yet, the pathophysiological mechanisms underlying their motor coordination deficits remain to be elucidated. Here, we show that application of IgG purified from the patients' serum to cerebellar slices of mice acutely reduces the basal activity of Purkinje cells, whereas application to the flocculus of mice in vivo evokes acute disturbances in the performance of their compensatory eye movements. In addition, the mGluR1-Abs block induction of long-term depression in cultured mouse Purkinje cells, whereas the cerebellar motor learning behavior of the patients is affected in that they show impaired adaptation of their saccadic eye movements. Finally, postmortem analysis of the cerebellum of a paraneoplastic cerebellar ataxia patient showed that the number of Purkinje cells was significantly reduced by approximately two thirds compared with three controls. We conclude that autoantibodies against mGluR1 can cause cerebellar motor coordination deficits caused by a combination of rapid effects on both acute and plastic responses of Purkinje cells and chronic degenerative effects.
Adult↗
Throwing darts: timing is not the limiting factor.
It has been argued that precision in throwing is limited by the precision in the timing of the release. When precision is the only goal, as in throwing darts, one could therefore expect people to throw in a way that reduces sensitivity for imprecision in timing. We show that subjects do not do so, but throw in a way that reduces the sensitivity for speed errors instead. They even appear to vary the timing of release to compensate for the errors in the hand's movement. Thus timing does not appear to be the limiting factor.
Adult↗