The haemodynamic blood response

Question 1

What is the ‘dip’?

Answer 1

At the start of the stimulus there is transient increase in deoxyhemoglobin (Hbr) due to increased oxygen consumption at a time when CBF hasn’t increased enough to ‘over compensate’.
Produces a decrease (dip) in BOLD fMRI signal.

Question 2

Why is the ‘dip’ useful?

Answer 2

Allows greater spatial localisation (resolution) of BOLD fMRI image

Question 3

What is optical imaging spectroscopy used for?

Answer 3

Used to measure haemoglobin concentration and oxygenation in specific parts of the brain.

Question 4

What is laser doppler flowmetry (LDF) used for?

Answer 4

To detect increases or decreases in cerebral blood flow

Question 5

What colour is oxyhaemoglobin?

Answer 5

Red

Question 6

What colour is deoxyhaemoglobin?

Answer 6

Blue

Question 7

Give an example of optical techniques used on animal models?

Answer 7

The Rodent Whisker Barrel Cortex

Question 8

How does Optical imaging Spectroscopy work?

Answer 8

Illuminate the cortex with lots of different colours

As oxyhaemoglobin and deoxyhaemoglobin are different colours they have a different absorption spectra

By comparing the data to the known absorption spectra of oxy and deoxyhaemoglobin we can use estimate changes