Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Biology and Biomedical Sciences: Neurosciences

Language

English (en)

Date of Award

Spring 3-8-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Steven E Petersen

Abstract

Reading is an important, phylogenetically new skill. While neuroimaging studies have identified brain regions used in reading, it is unclear to what extent these regions become specialized for use predominantly in reading versus other tasks. The goal of this dissertation is to investigate the extent to which reading specialization exists at the region and network level, with a focus on orthography, the visual processing of words and letters.

I used task-based and resting state functional connectivity: rs-fcMRI) studies to investigate the specialization of orthographic processing, purportedly localized to a left occipito-temporal fusiform cortex region. In Chapter 2, we find no visual region specialized for words or letter strings as compared to line drawn pictures and Amharic character strings: which compose the Ethiopian writing system). Rather, the region appears to be generally involved in visual processing with properties useful for reading, including the ability to process complex stimuli in groups.

In Chapter 3, we use rs-fcMRI to demonstrate functional relationships between the left occipito-temporal fusiform cortex and spatial attention regions rather than regions consistently activated in reading tasks.

In Chapter 4, we extend these findings by looking at the pattern of functional connectivity in a large network of reading-related regions found in a meta-analysis of reading studies. Using graph theoretic measures on resting state data, we did not find preferential functional connections between regions predominantly used in reading. Rather, we showed the network was basically composed of previously described, more general communities. Comparing the network structure of children and adults also shows few reading specific changes, but rather a change from local to distributed network structure, also seen previously.

In Chapter 5, we describe a comparison of activity during matching and naming tasks, and show task-dependent processing differences in reading-related regions. Such differences also indicate a lack of specificity for reading, and suggest the need for careful task design.

Together these results indicate a lack of neural specialization for reading at either the regional or network level, suggesting that fluent reading is instead performed by co-opting existing neural systems.

Comments

Permanent URL: http://dx.doi.org/10.7936/K78K773G

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