NEURAL BASIS OF PERCEPTUAL ORGANIZATION OF NATURAL SCENES: EMERGENCE OF OBJECT-BASED CODING IN THE PRIMATE VISUAL CORTEX

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dc.contributor.advisorShuler, Marshall G. Hussainen_US
dc.contributor.authorWilliford, Jonathan R.en_US
dc.contributor.committeeMemberNiebur, Ernsten_US
dc.contributor.committeeMemberHendry, Stewart H.en_US
dc.contributor.committeeMemberEgeth, Howard E.en_US
dc.date.accessioned2015-09-16T03:35:00Z
dc.date.available2015-09-16T03:35:00Z
dc.date.created2015-05en_US
dc.date.issued2014-11-10en_US
dc.date.submittedMay 2015en_US
dc.description.abstractDiscerning objects from their backgrounds is a fundamental process of vision. The coding of border-ownership in the early visual cortex is a neural correlate of this process. When stimulated with the contour of a figure, border-ownership selective neurons respond more strongly when the figure is on one side of their receptive field (the cell's "preferred" side) versus the opposite side of their receptive field (Williford and von der Heydt 2013). So far, border-ownership coding has only been shown with simple displays of geometric shapes (e.g., squares). Here I studied border-ownership coding with static images of natural scenes by recording the responses of neurons in macaque visual cortex to occluding contours of objects in complex scenes. I found that subsets of neurons in visual area V2 signal the side of ownership of such contours. Decomposition of local and context influences in these neurons showed that the context-based border-ownership signals correlated with those for the edge of a square (which is locally ambiguous), but were weaker. I used stimuli with intermediate complexity along several dimensions to measure the relative influences of object shape, occlusion between objects, texture and color contrast to determine how they contribute to the border-ownership signal strength. I found that border-ownership signal decreases with the stimulus complexity. This was especially pronounced when comparing a simple isolated square with a c-shape figure, overlapping squares, and natural stimuli. There were also smaller decreases when changing from uniform squares to natural texture squares and from squares to silhouettes of natural shapes. In conclusion, subsets of neurons in V2 do code for the border-ownership in natural scenes, however, the strength and accuracy of these early estimates of border-ownership decreases with the complexity of the visual stimulus.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.urihttp://jhir.library.jhu.edu/handle/1774.2/37860
dc.languageen
dc.publisherJohns Hopkins University
dc.subjectPerceptual organizationen_US
dc.subjectV1en_US
dc.subjectV2en_US
dc.subjectrhesus macaqueen_US
dc.subjectvisual neuroscienceen_US
dc.subjectborder-ownership codingen_US
dc.subjectvisual perceptionen_US
dc.subjectelectrophysiologyen_US
dc.subjectextracellular electrode recordingen_US
dc.titleNEURAL BASIS OF PERCEPTUAL ORGANIZATION OF NATURAL SCENES: EMERGENCE OF OBJECT-BASED CODING IN THE PRIMATE VISUAL CORTEXen_US
dc.typeThesisen_US
dc.type.materialtexten_US
thesis.degree.departmentNeuroscienceen_US
thesis.degree.disciplineNeuroscienceen_US
thesis.degree.grantorJohns Hopkins Universityen_US
thesis.degree.grantorSchool of Medicineen_US
thesis.degree.levelDoctoralen_US
thesis.degree.namePh.D.en_US
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