Lecture 2 - Neuroscience Methods 2 Flashcards Preview

Neuroscience > Lecture 2 - Neuroscience Methods 2 > Flashcards

Flashcards in Lecture 2 - Neuroscience Methods 2 Deck (89)
Loading flashcards...

What is the purpose of neuroscience techniques

Study relationship between brain and behaviour
Idea: spatial resolution cellular temporal resolution ms
Whole brain studied simultaneously = so much data difficult analyse
Non invasive


What is the spatial and temporal resolution for fmri

Spatial resolution excellent
Temporal resolution not as good as electrophysiological methods


What is an example of structural imaging



What are the goals of structural imaging

Study anatomy
Identify abnormalities
Follow development
Show plasticity


What are the structural imaging methods of interest to Biological psychology

Computed tomography CT scans
MRI - Sir Peter Mansfield

Rely on contrast between tissue types white matter vs gray matter vs cerebrospinal fluid


Example of studying juggling in structural MRI

Baseline scan
Then juggling boys practice daily until reach certain skill level
After 3 months scanned again


Example of studying juggling in structural MRI results

Scan increase grey matter in occipital region

After 3 fourth months told not to practice increase gray matter reversed


What does the study of juggling in structural MRI tell us

Brain plasticity after motor learning

Not be confused with fMRI

Correspond area hMT/V5 visual motion area


Outline the extrastriate visual areas

Process input from geniculostriate system

V5 = dorsal pathway = vision
E.g. visual coordination grasping

Supported brain structures dorsal pathway


How to generate structural MR contrast

Core: magnet generating strong EM field = external static magnetic field. Throughout and around scanner
Outsider scanner protons soft tissues all oriented at random. Undergo spinning movement in random order
Axis oriented vertical axis field. Not random
Protons spin axis generate own MF


How do protons spin axis to generate their own MF in generating structural MR contrast

Spin axis not completely vertical rotates about vertical axis
Precessional motion
More protons aligned parallel external (longitudinal) MF
Lower energy than antiparallel


How is 1 cell represented in structural MR contract

One cell represented by magnetic vector


What are important components in generating structural MR contrast

Radio frequency coils


Outline the net magnetisation vector

Magnetisation changes in response to radio frequency pulses


Outline use of compass and a magnet in structural MR contrast generation

Compass contained surrounding fluid
Beginning points north with earths magnetic field
Magnet applied compass point east
Remove magnet and needle returns


Apply findings of use of compass and a magnet to structural MR contrast generation

Protons in bod aligned external magnetic field = net magnetisation
Radio frequency pulse applied
Net magnetisation perpendicular external magnetic field
0% inner magnetic field line with net magnetisation vector
Radio frequency pulse removed net magnetisation vector returns to original state


What is net magnetisation vector

Protons body aligned with external magnetic field


How is MR signal measured in MR contrast generation

Radio frequency pulse removed net magnetisation vector returns original state
Net magnetisation direction external magnetic field recovers 100% pre radio frequency value
MR signal measured during recovery = readout


What does the MR contrast generation draw on to produce signal

Sequences RF pulses and readout = MR protocol
Protons different tissue types gray vs white require different time realign = basis of MR contrast


What happens when you increase vertical component in MR contrast

Increase magnetisation
Protons aligned parallel with external magnetic field
That is parallel with external magnetic field
Increase longitudinal magnetisation
Spin lattice relaxation


Outline structure specific time courses of spin lattice relaxation

Brain tissue faster relaxation than ventricles CSF T1 signal
Signal brain stronger
MR contrast tissue specific
Radio frequency coil what measures T1


What creates the resulting image in specific time courses of spin lattice relaxation

Combination specific radio frequency pulse
Specific readout time


What is the order of contrasts in specific time courses of spin lattice relaxation

T1 white matter > T1 gray > T1 CSF


Outline the effects of modifying radio frequency pulses and read out times on MR properties

T2 signal white matter < gray matter < CSF


What is the goal of a functional MRI

Identify brain areas support sensory and cognitive processes
Derive models brain function


What does an fMRI measure

Blood flow
Need contrast separates non activated vs activated tissue


What are the 3 problems of fMRIs

How measure neural activity in functional contrast?

How generate measurable functional contrast in experiment?

How identify functional contrast fMRI raw data?


Outline T2 contrast underlying fMRIs for problem 1 how to measure neural activity in fMRI contrast

Depends balance deoxygenated : oxygenated haemoglobin within blood in voxel
Then depends on local regulation arterial width
Capillaries and arteries carrying blood near inactivate neutron contain both oxygen and deoxygen haemoglobin
Near active neuroma predominantly oxygenated


Outline local neuronal activation and T2 contrast problem 1 how to measure neural activity in fMRI contrast

Flow increased more oxygen capillaries
Diamagnetic = not affect local magnetic field

Deoxygenated = paramagnetic field inhomogeneous. T2 signal different oxygenated and deoxygenated blood result. Different time pause


What occurs in an inhomogeneous field during local neuronal activation in problem 1 how to measure neural activity in fMRI contrast

Horizontal magnetisation decays fasted (T2 decay)
Slower T2 decay increased MR signal
Blood oxygen dependent = BOLD effect