imaging

Question 1

any ___________, _____________ particle emits ______________ radiation which can be detected

Answer 1

accelerating
charged
electromagnetic

Question 2

producing the mri signal

Answer 2

1. apply magnetic field
2. protons line up with vertical field
3. apply radio frequency pulse
4. protons rotate in sync on their axis
   - changing, magnetic field is produced
5. radio frequency pulse turned off
6. protons dephase - loss of horizontal magnetism
7. protons realign - gain in vertical magnetic signal

Question 3

T1 weighted image

Answer 3

MRI image based on realignment phase

Question 4

T2 weighted image

Answer 4

MRI image based on dephasing

Question 5

do protons dephase more quickly in dense tissue or less dense tissue?

Answer 5

dense tissue - atoms are packed together very strongly

Question 6

where are surface blood vessels located in the brain?

Answer 6

arachnoid membrane

Question 7

why is blood flow increase to the brain slow?

Answer 7

takes a long time for the diameter of the arteriole to change (time lag)

Question 8

what is the BOLD signal?

Answer 8

signal produced from MRI scanner detection of paramagnetic deoxygenated blood flowing out of a capillary bed in certain areas of the brain

Question 9

why is the nature of the BOLD signal thought to be controversial?

Answer 9

• increased blood flow exceeds requirements of the active neurons so nothing to do with nutrition
• increased blood flow = non-specific cooling system

Question 10

what is non-linear registration?

Answer 10

creating an average brain by morphing anatomical data from many peoples’ brains together
then overlaying bold signals

Question 11

advantages and disadvantages of fMRI?

Answer 11

+ high spatial resolution

- low temporal resolution

Question 12

GCaMP

Answer 12

GFP fused to m13 and calmodulin
dark conformation - not as bright as normal GFP
ca2+ present? -> m13 and calmodulin interact and stabilise GFP in bright conformation
increasing intracellular Ca2+ –> brighter GFP
active neurons = ca2+ channels open

Question 13

provide an example of high resolution microscopy

Answer 13

confocal microscopy

Question 14

how is high resolution achieved in microscopes?

Answer 14

pinhole rejects light not coming from the focal plane –> increases spatial resolution

Question 15

halorhodopsin

Answer 15

cl- channel activated by yellow light

when activated, channel opens + hyperpolarises neuron –> inhibits neuron

Question 16

channelrhodopsin

Answer 16

ion channel (k+, na+, h+) activated by blue light
when activated, channel opens + depolarises neuron --> AP fires --> activates neuron

Question 17

DEFINE: optogenetics

Answer 17

imaging and genetics involving using an ion channel activated by light