All ETDs from UAB

Advisory Committee Chair

Rajesh K Kana

Advisory Committee Members

Maria I Hopkins

David C Knight

Document Type

Thesis

Date of Award

2010

Degree Name by School

Master of Arts (MA) College of Arts and Sciences

Abstract

Visual information in the brain is processed by two distinct pathways, the dorsal and the ventral visual streams, which operate in a parallel and distributed manner. While the dorsal stream, associated with locating objects in space, extends from the occipital towards the parietal lobe, the ventral stream, associated with recognizing objects, projects from occipital to the temporal lobes (Ungerleider & Mishkin, 1982). This division of labor evidenced from lesion studies in monkeys may be rather reductionistic in the context of humans where the experience-driven knowledge base is rich and may prompt neural integration (Mesalum, 2008). The present fMRI study investigated the specialization and integration of dorsal and ventral streams in eighteen healthy adult volunteers using two simple tasks of object recognition and location detection. The stimuli consisted of grays-cale photographs of common household objects presented in a blocked design format. In the object recognition task, the participants named an object from four choices, and in the location detection task, they located the position of a given object relative to a cross pre-sented on the screen. While the location detection task elicited greater activation in the dorsal visual stream (precuneus, right angular gyrus, superior parietal lobule), recognizing objects showed greater activation in several cortical (left inferior frontal gyrus) and subcortical (bilateral thalami) areas previously found to be associated with tasks of object recognition. Although there were no differences found in functional connectivity between the two tasks, we found preliminary evidence for a group of regions, such as frontal and parietal cortex, working together in this task. Overall, the results of this study indicate the existence of specialized modules for object recognition and location detection, and possible interactions between areas beyond the visual cortex that may play a role in such tasks.

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