Neuroscience methods 2 Flashcards
What is a T1 image
An image of brain anatomy.
Resolved from an MRI when hydrogen protons return to normal magnetism
What is DTI used for
Mapping white matter & brain connectivity
What is fMRI used for
Mapping brain activation
What is MRS used for
Mapping metabloic activity
How does TMS work?
A coil induces a magnetic field that induces an electrical field in the brain and causes ells to fire
What is TMS
Trans-magnetic stimulation.
A non-invasive method of stimulating cortical tissues by administration of a brief magnetic pulse to the scalp
What is BOLD
Blood Oxygen level dependence.
A measure of ration of oxygenated to deoxygenated blood
What is a T2 image
An image of connectivity through the fluid (CSF) in the brain resolved when the hydrogen protons relax their spinning
Does EEG have better spatial or temporal resolution
Temporal
Does fMRI have better spatial or temporal resolution
Spatial
What connections does fMRI measure
functional connections between brain regions
What connections does DTI measure
Structural connections between brain regions
What is temporal resolution
The time course of various neural events
What is spatial resolution
Ability to discern elementary units of activated brain networks
Who should not use TMS
- People with a history of seizures
- People with metal in the head
- People with history of serious head injury
Explain the trade-off in network connectivity in the brain
Regular networks have low metabolic cost but low efficiency
Random networks have high metabolic cost but high high efficiency
What is spatial normalisation
Averaging out individual differences in brain structure
What is a limitation of voxel-based morphology
Limited to locating abnormalities. Can not explain them (e.g. neurons or synapse loss)
Are tracts in DTI axons?
No, they are estimates of the trajectory of a fiber pathway
What are explanations for variation in tract diffusion in DTI?
- altered fibre integrity/myelin
- altered organisation
- noise
What is a limitation of DTI
- not a direct physiological meaningful measure of connectivity
- cannot distinguish efferent/afferent connection
What does DTI measure
Water diffusion in the brain
- anisotropic diffusion along axons
What is radial diffusivity?
Less diffusion - an index of myelin integriy
What is axial diffusivity?
Breakdown of fibre organisation
What are the limitations of fMRI?
- BOLD response may reflect neuronal exhitation/inhibition or a combination
- BOLD response is much slower than neuronal activity
What is does fMRI measure
The ratio of oxygenated to deoxygenated blood
What is a block design?
Trial with a condition are presented together
What is a event-related design?
Randomised presentation of trials
Which has higher power: block or event-related design
Block
What have animal studies revealed about the BOLD measure
It is correlated with input into a brain region (local field potential) not output (multi unit activity)
What does resting state fMRI measure
Brain activity in the absence of a task
How much energy consumption is from base activity in the brain?
80%
How long does it take for the brain to return to baseline after task
Up to 15 minutes
What is a connectome
A comprehensive map of neural connections
What is graph theory
A mathmatical field that looks at how networks interact with each other
What neurotransmitter is involved with TMS measurement of cortical inhibition
GABA
In TMS, what frequency is used to create a virtual lesion
1Hz
In TMS, what frequency is used to enhance brain activity
5Hz or greater
What is the therapeutic application of TMS to schizophrenia
An inhibitory pulse is used to treat auditory hallucinations in schizophrenia
What is the therapeutic application of TMS to depression
An excitation pulse is used for treatment resistant depression
