Reliability of Functional MRI for Motor and Language Cortex Activation

John W. Haller, Ph.D., Principal Investigator
Adjunct Assistant Professor & Assistant Research Scientist
Department of Radiology, College of Medicine
The University of Iowa
john-haller@uiowa.edu

Introduction

Functional magnetic resonance imaging (fMRI) based on blood oxygen level-dependent (BOLD) contrast is a useful technique for mapping brain functions, and can be used to map brain activity in patients with brain tumors. The purpose of this study is to reliably activate areas of language and motor cortex and demonstrate consistency of results. The ultimate goal of this project is to use these techniques to map brain functions in patients with brain tumors, and to spare these regions during brain surgery.

Methods

Three language tasks and a motor task (hand squeeze) will be performed using a block design with normal subjects and patients with brain tumors. Subjects are asked to squeeze their hand once per second for 30 seconds during the activation phase, and keep their hand motionless during a 30 second rest period. During the three language tasks subjects are asked to 1) think of words that began with a single letter that is visually presented for 30 seconds, 2) Complete a three letter word stem that presented every two seconds over a 30 second period and 3) generate a verb that associated with a noun presented every two seconds over a period of 30 seconds. During the 30 second rest phase of the language tasks, subjects are asked to visualize the sky at dusk or simply look at a fixation point. Echo planar imaging (EPI) and anatomic images are collected on a 1.5 T Signa CV/i scanner (GE Medical Systems, Milwaukee, WI). Different language tasks described above are used to demonstrate the consistency (overlap) of brain areas activated during these tasks. To demonstrate the reliability of the tasks to activate similar regions between subjects, correlation images from different subjects are non-linearly warped into a standard atlas image. Correlation images of the brain are generated with a criterion threshold of 0.4 for language tasks, and 0.7 for motor cortex activation.

Outcome of Learning Experience

By the end of these studies, a student will learn a variety of tasks and become familiar with the acquisition of MRI data in a behavioral experiment. The primary responsibility of the student will be to post-process images of brain function (fMRI) and brain anatomy (MRI). The student will become familiar with the real-time acquisition of these images being developed at the University of Iowa Hospitals and Clinics. Finally, an introduction to the operation of an MRI scanner will also be part of the learning experience.