Bradley Schlaggar, MD, PhD
Adjunct Professor of Neurology
The development and plasticity of human cognition and language Read More
|Keywords:||Tourette Syndrome, reading, language, development, fMRI, network, graph theory|
Functional Connectivity and Network properties in the brain
Advances in magnetic resonance imaging technology have enabled precise measurements of correlated activity throughout the brain. This technique is done by correlating spontaneous BOLD activity, measured with resting state functional connectivity (rs-fcMRI), across the cortex. We have found that putative areal boundaries can be reliably detected in individual subjects as well as in group data using rs-fcMRI. Additionally, combining surface-based analysis techniques with image processing algorithms allows automated mapping of putative areal boundaries across large expanses of cortex without the need for prior information about a region’s function or topography.
This tool has led to the first comprehensive descriptions of functional brain networks in humans. We have embarked on an effort to collect resting state functional connectivity MRI data from a large pool of subjects over a range of ages. We are exploring a powerful framework for analyzing networks, called graph theory. We aim to characterize the development of brain systems (e.g. the default mode network) in a way that is comprehensive within a given system, as well as the relationships between systems in a wider network context. Our recent efforts have focused on the ways in which functional connectivity and network properties change across development, in aging, and in neuropsychiatric disorders.
Development of language and reading
Reading involves a range of processing steps such as orthographic, phonological and semantic processing. Our research explores the neural correlates of those concomitant functions in order to better understand reading as a whole. We use methods that facilitate direct statistical comparison between child and adult imaging data (e.g. performance matching) to characterize language development. We have also explored the effects of early brain injury on lexical processing and sex differences in adult language processing.
Our research suggests that task performance is instantiated by at least three distinct types of task-related signals: 1) signals tied to the start of a specific task condition, which should be, at least in part, related to the instantiation of task parameters; 2) prolonged fMRI signals that span the entirety of a task and likely reflects task set maintenance; and 3) error-related feedback activity, to monitor processing and encourage adjustment of top-down signals. We have implemented mixed blocked/event-related designs in a number of experiments as a means of elucidating different task-related signals that occur simultaneously in the course of completing a task or switching between tasks.
In conjunction with resting state functional connectivity MRI, we have discovered that task control regions (ROIs involved in at least one of the three signals mentioned) form two distinct networks in the brain. We are currently probing the ways in which these networks differ.
Updated January 2014