1 / 16

BOLD fMRI

BOLD fMRI. What is fMRI ?. fMRI stands for Functional MRI Functional MRI measures a physiological process in real time; it looks at the function rather than the structure. What is BOLD fMRI ?. BOLD stands for Blood Oxygen Level Dependent

beate
Télécharger la présentation

BOLD fMRI

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BOLD fMRI

  2. What is fMRI? • fMRI stands for Functional MRI • Functional MRI measures a physiological process in real time; it looks at the function rather than the structure

  3. What is BOLD fMRI? • BOLD stands for Blood Oxygen Level Dependent • BOLD fMRI measures brain activity by measuring blood oxygen level • When an area of the brain is more active, it calls for more blood flow to supply glucose and oxygen

  4. How does it work? • Hemodynamic response MRI Signal Neuron Time Blood vessel Ratio of O2 to no O2 = 10:4 Red Blood Cell (without O2) Red Blood Cell (with O2)

  5. How does it work? • Hemodynamic response Neuron Activates MRI Signal I NEED FOOD!!!! Time Blood vessel Ratio of O2 to no O2 = 7:7 Red Blood Cell (without O2) Red Blood Cell (with O2)

  6. How does it work? • Hemodynamic response MRI Signal That’s better! Time Blood vessel dilates Ratio of O2 to no O2 = 21:7 More blood flow

  7. How does it work? • Hemodynamic response Neuron rests MRI Signal I’m good now! Time Blood vessel returns to normal Blood vessel Ratio of O2 to no O2 = 10:4

  8. Hemodynamic Response, Step by Step • Brain Activates and begins to use more glucose and oxygen • Brain calls for more glucose and oxygen • Blood vessels dilate to increase blood flow • Brain deactivates • Blood vessel returns to normal

  9. Back to BOLD • So, our signal increases when blood flow increases • And we know that blood flow increases when brain activity increases • Therefore, we can measure brain activity by looking at our BOLD fMRI signal

  10. HOWEVER: • The brain is never completely inactive, and we always have blood flow • We also don’t know what a “normal” level of blood flow is from person to person, so we don’t know what a “normal” signal level is • Let’s call our MRI signal our dependent variable since that’s what we’re really measuring, and we know that it represents blood flow. So what do we need now?

  11. CONTROL! • We need to know what the signal looks like when we are sure that the part of the brain we’re looking at is not activated • Let’s look at how we design a BOLD fMRI experiment

  12. Experiment Design • Let’s say we want to look at motor activation

  13. Experiment Design • If blood is always flowing through the brain, how can we design our experiment?

  14. Block Design Active Active Active Active Rest Rest Rest Rest

  15. Block Design • So we subtract the signal during rest blocks from the signal during active blocks • If there is a significant difference, then we conclude that the brain is activating as a result of our activity • We can then divide the brain into a grid to see exactly where the activation is taking place

  16. Results

More Related