Saccades, smooth pursuit and vergence eye movements either shift or maintain gaze on objects of interest so that the image of the object is, respectively, either brought to, or maintained on the fovea for detailed analysis. To date, the neural substrates of these eye movements have been characterized individually using a variety of techniques including electrophysiology, positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) both in non-human primates (NHPs) and humans. The non-invasive nature of fMRI allows us to use the same tasks and techniques in both humans and nonhuman primates. The purpose of the present study was to use blood oxygenation level-dependent (BOLD) fMRI to explore the cortical and subcortical regions involved in saccades, smooth pursuit and vergence eye movements from a comparative point of view in humans.
Visual stimuli were presented using a custom-made polarization-based stereoscopic visual display. Eighteen participants performed saccadic, smooth pursuit, vergence tracking, and vergence step eye movements in response to solid targets and cyclopean targets during functional imaging sessions in a Philips Achieva 3T scanner. The positions of both eyes were tracked using an EyeLink 1000 eye tracker.
All types of eye movements in response to either type of target (solid and cyclopean) evoked BOLD responses in core regions of the previously defined oculomotor network, such as early visual cortical areas, posterior parietal cortex (PPC), human middle temporal cortex (hMT+), the frontal eye fields (FEF) and the supplementary eye fields (SEF). In addition, we observed task-dependent activations in the cingulate gyrus, the anterior insula, paracentral lobule and the supramarginal gyrus. Target-dependent variations were observed in the early visual areas, subcortical structures and the right superior temporal gyrus. Cerebellar activation was also observed in all types of eye movements.
This is the first study to directly compare these four types of eye movement, using fMRI. In addition, to our knowledge, this is the first study to use cyclopean targets in an eye movement paradigm. The results are consistent with the findings of previous eye movement studies in humans as well as in NHPs obtained using PET, fMRI or electrophysiology.
|Advisor:||Gamlin, Paul D.|
|Commitee:||Cox, James E., Knight, David C., Lahti, Adrienne C., Liu, Lei, Weller, Rosalyn E.|
|School:||The University of Alabama at Birmingham|
|School Location:||United States -- Alabama|
|Source:||DAI-B 73/10(E), Dissertation Abstracts International|
|Keywords:||Cyclopean, Eye movements, Eye-tracking, Fmri, Human, Neural networks, Vergence|
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