5 results on '"Lindner, Axel"'
Search Results
2. Sustained bias of spatial attention in a 3 T MRI scanner.
- Author
-
Smaczny, Stefan, Behle, Leonie, Kuppe, Sara, Karnath, Hans-Otto, and Lindner, Axel
- Subjects
ATTENTIONAL bias ,SCANNING systems ,UNILATERAL neglect ,MAGNETIC resonance imaging ,VISUAL perception ,EYE movements ,VESTIBULAR stimulation - Abstract
When lying inside a MRI scanner and even in the absence of any motion, the static magnetic field of MRI scanners induces a magneto-hydrodynamic stimulation of subjects' vestibular organ (MVS). MVS thereby not only causes a horizontal vestibular nystagmus but also induces a horizontal bias in spatial attention. In this study, we aimed to determine the time course of MVS-induced biases in both VOR and spatial attention inside a 3 T MRI-scanner as well as their respective aftereffects after participants left the scanner. Eye movements and overt spatial attention in a visual search task were assessed in healthy volunteers before, during, and after a one-hour MVS period. All participants exhibited a VOR inside the scanner, which declined over time but never vanished completely. Importantly, there was also an MVS-induced horizontal bias in spatial attention and exploration, which persisted throughout the entire hour within the scanner. Upon exiting the scanner, we observed aftereffects in the opposite direction manifested in both the VOR and in spatial attention, which were statistically no longer detectable after 7 min. Sustained MVS effects on spatial attention have important implications for the design and interpretation of fMRI-studies and for the development of therapeutic interventions counteracting spatial neglect. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Human posterior parietal and dorsal premotor cortex encode the visual properties of an upcoming action
- Author
-
Pilacinski, Artur, Wallscheid, Melanie, and Lindner, Axel
- Subjects
Male ,genetic structures ,Eye Movements ,Vision ,Physiology ,Visual System ,Sensory Physiology ,lcsh:Medicine ,Social Sciences ,Diagnostic Radiology ,Mathematical and Statistical Techniques ,Functional Magnetic Resonance Imaging ,Parietal Lobe ,Medicine and Health Sciences ,Psychology ,lcsh:Science ,Musculoskeletal System ,Cerebral Cortex ,Brain Mapping ,Radiology and Imaging ,Statistics ,Motor Cortex ,Brain ,Magnetic Resonance Imaging ,Sensory Systems ,Physical Sciences ,Visual Perception ,Sensory Perception ,Female ,Anatomy ,psychological phenomena and processes ,Research Article ,Imaging Techniques ,Cognitive Neuroscience ,Movement ,Prefrontal Cortex ,Neuroimaging ,Research and Analysis Methods ,behavioral disciplines and activities ,Diagnostic Medicine ,Reaction Time ,Humans ,Statistical Methods ,Vision, Ocular ,Analysis of Variance ,lcsh:R ,Biology and Life Sciences ,Cognitive Science ,lcsh:Q ,Mathematics ,Photic Stimulation ,Psychomotor Performance ,Neuroscience - Abstract
Behavioral studies show that motor actions are planned by adapting motor programs to produce desired visual consequences. Does this mean that the brain plans these visual consequences independent of the motor actions required to obtain them? Here we addressed this question by investigating planning-related fMRI activity in human posterior parietal (PPC) and dorsal premotor (PMd) cortex. By manipulating visual movement of a virtual end-effector controlled via button presses we could dissociate motor actions from their sensory outcome. A clear representation of the visual consequences was visible in both PPC and PMd activity during early planning stages. Our findings suggest that in both PPC and PMd action plans are initially represented on the basis of the desired sensory outcomes while later activity shifts towards representing motor programs.
- Published
- 2018
4. Cerebrocerebellar Circuits for the Perceptual Cancellation of Eye-movement-induced Retinal Image Motion.
- Author
-
Lindner, Axel, Haarmeier, Thomas, Erb, Michael, Grodd, Wolfgang, and Thier, Peter
- Subjects
- *
EYE movements , *VISUAL perception , *MAGNETIC resonance imaging , *DIAGNOSTIC imaging , *VISION - Abstract
Despite smooth pursuit eye movements, we are unaware of resultant retinal image motion. This example of perceptual invariance is achieved by comparing retinal image slip with an internal reference signal predicting the sensory consequences of the eye movement. This prediction can be manipulated experimentally, allowing one to vary the amount of self-induced image motion for which the reference signal compensates and, accordingly, the resulting percept of motion. Here we were able to map regions in CRUS I within the lateral cerebellar hemispheres that exhibited a significant correlation between functional magnetic resonance imaging signal amplitudes and the amount of motion predicted by the reference signal. The fact that these cerebellar regions were found to be functionally coupled with the left parieto-insular cortex and the supplementary eye fields points to these cortical areas as the sites of interaction between predicted and experienced sensory events, ultimately giving rise to the perception of a stable world despite self-induced retinal motion. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
5. Initiation of smooth-pursuit eye movements to first-order and second-order motion stimuli.
- Author
-
Lindner, Axel and Ilg, Uwe J.
- Subjects
EYE movements ,BENDER-Gestalt Test ,AVERSIVE stimuli ,HUMAN behavior ,VISUAL perception ,VISION - Abstract
Since normal human subjects can perform smooth-pursuit eye movements only in the presence of a moving target, the occurrence of these eye movements represents an ideal behavioural probe to monitor the successful processing of visual motion. It has been shown previously that subjects can execute smooth-pursuit eye movements to targets defined by luminance and colour, the first-order stimulus attributes, as well as to targets defined by derived, second-order stimulus attributes such as contrast, flicker or motion. In contrast to these earlier experiments focusing on steady-state pursuit, the present study addressed the course of pre-saccadic pursuit initiation (less than 100 ms), as this early time period is thought to represent open-loop pursuit, i.e. the eye movements are exclusively driven by visual inputs proceeding the onset of the eye movement itself. Eye movements of five human subjects tracking first- and second-order motion stimuli had been measured. The analysis of the obtained eye traces revealed that smooth-pursuit eye movements could be initiated to first-order as well as second-order motion stimuli, even before the execution of the first initial saccade. In contrast to steady-state pursuit, the initiation of pursuit was not exclusively determined by the movement of the target, but rather due to an interaction between dominant first-order and less-weighted second-order motion components. Based on our results, two conclusions may be drawn: first and specific for initiation of smooth-pursuit eye movements, we present evidence supporting the notion that initiation of pursuit reflects integration of all available visual motion information. Second and more general, our results further support the hypothesis that the visual system consists of more than one mechanism for the extraction of first-order and second-order motion. [ABSTRACT FROM AUTHOR]
- Published
- 2000
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.