Measuring visual stimulation and attention signals in human superior colliculus using high-resolution fMRI

dc.contributor.advisorRess, David Bruce
dc.creatorKatyal, Suchariten
dc.date.accessioned2014-07-14T20:15:08Zen
dc.date.issued2013-05en
dc.date.submittedMay 2013en
dc.date.updated2014-07-14T20:15:08Zen
dc.descriptiontexten
dc.description.abstractThe superior colliculus (SC) is a laminated oculomotor structure in the midbrain. In non-human primates SC has long been known to contain a retinotopically-organized map of visual stimulation in its superficial layers, which is aligned to a map of saccadic eye movements in the deeper layers. Microstimulation and electrophysiology experiments have shown that SC also plays a key role in covert visuospatial attention and suggest that attentional modulation also occurs in a retinotopic manner. Retinotopic organization of the visual field can be non-invasively mapped in humans using functional MRI with a technique called phase-encoded retinotopy. In this technique, rotating wedges and expanding rings of visual stimuli are used to map the polar angle and eccentricity dimensions of a polar coordinates system, respectively. A similar technique can also be used to map spatial attention by keeping the visual stimulus constant and cueing subjects to attend to apertures of rotating wedges and expanding rings within the stimulus. A previous study using fMRI has shown the polar angle representation of visual stimulation in human SC but was unable to find a representation of eccentricity. This work uses high-resolution fMRI along with special surface analysis techniques developed in our lab to demonstrate maps of both polar angle and eccentricity for visual stimulation. Moreover, visual attention is also shown to be topographically organized within SC and in registration with visual stimulation. Finally, in human visual cortex, fMRI is known to show activity for sustained spatial attention even in the absence of a significant visual stimulus, an attentional "base response". In this work, SC is shown to exhibit a similar sustained attention base response using a threshold-contrast detection paradigm. This base response was compared with a response for attention with visual stimulation. The peak amplitude of the base response occurred more deeply within SC tissue than the peak for attention with stimulation. It is proposed that this reflects the specific attentional enhancement of the deeper visuomotor neurons, which are hypothesized to be a direct neuronal correlate of the oculomotor theory of attention.en
dc.description.departmentPsychologyen
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/2152/25179en
dc.subjectVisionen
dc.subjectAttentionen
dc.subjectfMRIen
dc.subjectSuperior colliculusen
dc.subjectOculomotoren
dc.subjectBase responseen
dc.titleMeasuring visual stimulation and attention signals in human superior colliculus using high-resolution fMRIen
dc.typeThesisen
thesis.degree.departmentPsychologyen
thesis.degree.disciplinePsychologyen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen

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