BOLD fMRI

Why do we need to know physics/physiology of fMRI?

Developments allowing functional MRI

Contrast Agents

External Contrast Agents

Belliveau et al., 1990

Common Contrast Agents

Hemodynamic Measures of Blood Flow

Does blood flow serve function?

Slide 10

PET Imaging

PET Studies of Brain Function

History of BOLD fMRI

Slide 14

Blood Deoxygenation affects T2 Recovery

Ogawa et al., 1990a

Ogawa et al., 1990b

Slide 18

Kwong et al., 1992

Ogawa et al., 1992

Blamire et al., 1992

BOLD Endogenous Contrast

Slide 23

Slide 24

Discarded and Deleted Acquisitions (DISDAQs)

Relation of BOLD Activity to Neuronal Activity

1. Assumptions

Slide 28

Slide 29

Slide 30

2. Measuring Deoxyhemoglobin

3. Different changes in CBF & CMRO₂

Slide 33

The Hemodynamic Response

Impulse-Response Systems

Basic Form of Hemodynamic Response

Baseline Period

Initial Dip (Hypo-oxic Phase)

Early Evidence for the Initial Dip

Rise (Hyperoxic Phase)

Peak – Overshoot

Sustained Response

Undershoot

Issues in HDR Analysis

The Hemodynamic Response Lags Neural Activity

Percent Signal Change

Amplitude of the HDR

Variability in the Hemodynamic Response

Relative vs. Absolute Measures

Detection vs. Estimation

Analyzing data using BIAC tools

Basic Steps of Analysis