FMRI Flashcards
how does blood flow increase?
When a group of neurons in the brain becomes more active, the capillaries around them dilate automatically to bring more blood and hence more oxygen to them
how does an FMRI scan work?
Within the red blood cells, the oxygen is carried by a protein molecule called hemoglobin, which contains an iron atom. Once a hemoglobin molecule releases its oxygen, it is called deoxyhemoglobin and has a property called paramagnetism, which means that it causes a slight disturbance in the magnetic field of its surroundings. This disturbance is used in fMRI to detect the concentration of deoxyhemoglobin in the blood.
what happens if the deoxyhemoglobin concentration decreases as a result of oxygen demand?
It is this decline in the concentration of deoxyhemoglobin that fMRI interprets as increased activity in this area of the brain.
how is experiment used to detect where the most neural activity is located?
if one fMRI image is recorded of the brain before the subject performs a task, and another is recorded while the subject performs the task, and the intensities of the same areas in the two different images are subtracted from each other, the areas with the largest differences will appear “lit up”. These areas represent the parts of the brain that are the most heavily infused with blood, and hence the areas with the greatest neuronal activity.
