All ETDs from UAB

Advisory Committee Chair

Kristina M Visscher

Advisory Committee Members

Paul D Gamlin

Jhon J Hablitz

Louis B Justament

Adrienne C Lahti

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Due to the changing demands of the environment and our behavioral intentions the brain has to adapt in order to produce task appropriate responses. Part of the challenge is the large amount of sensory information received by the brain. Depending on individu-al goals, the brain must select and react to task appropriate stimuli while ignoring other irrelevant sensory input. Since behavioral intentions are dynamic, this requires the re-sponses within the brain to also be dynamic. Cognitive control, exerted by higher centers on sensory cortex allow for selection of task relevant stimuli. In this study we find that intrinsic, non-stimulus driven activity in sensory cortex allows for selection of task ap-propriate stimuli. This thesis details three projects that explore different timecourses of intrinsic activity in sensory cortex using fMRI. In project 1, we examine different timecourses of intrinsic activity in retinotopi-cally mapped visual cortex (V1, V2, V3 and V4h), and how they are influenced by atten-tion to visual stimuli. We compare intrinsic activity associated with task initiation to in-trinsic activity associated with maintaining a task set. We find that early visual cortex is involved in maintaining attention to visual stimuli, and also involved in task switching. In addition, we show that these task-set-related, but stimulus-independent signals influ-ence a participant's performance. In project 2, we examine the different intrinsic activity timecourses across the ec-centricity of V1 during auditory tasks. We find that peripheral V1 responds to attended auditory stimuli but unlike central V1, does not show activity associated with task antic-ipation. In project 3, we show that part of the process of selecting task relevant stimuli in sensory cortex, both visual and auditory, involves increased connectivity with fronto-parietal regions. During simultaneous presentation of auditory and visual stimuli the vis-ual cortex showed an increase an increase in connectivity to fronto-parietal regions when attention was directed to visual while auditory cortex showed an increase in connectivity when attention was directed to auditory stimuli. These fronto-parietal regions are in-volved in cognitive control, and the increase in connectivity with task relevant sensory cortex suggests that this is a mechanism for driving selection of relevant stimuli.

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