Week 1 - Methods Flashcards
what are the four main coordinates or bearing of the vertebrate NS?
- Dorsal - top of the brain or back of the human spine (back)
- Ventral - bottom of the brain or front of the human spine (belly)
- Anterior - Front of the brain or the direction travelling up the spine
- Posterior - back of the brain or the direction travelling down the spine
What are some other terms for:
1. above versus below
2. towards the head and towards the tail
3. both sides and one side
4. close the main body mass and far from the main body mass?
5. other side vs same side
- SUPERIOR (above) versus INFERIOR (below)
- ROSTRAL (towards the head) versus CAUDAL (towards
the tail) - BILATERAL (both sides) versus UNILATERAL (one side)
- PROXIMAL (close to the main body mass) versus
DISTAL (far from the main body mass) - CONTRALATERAL (other side) versus IPSILATERAL
(same side)
What are the four synonyms for ““below” in NS?
Inferior
Sub
Hypo
Infra
e.g. inferior colliculus
e.g. subdural space
e.g. hypothalamus
e.g. infratentorial tumour
What is the difference between structure and function?
Structure
* tells about the morphology or form of things
* CT scan may show brain structure and indicate a
tumour that may be causing some observable
behaviour
Function
* tells us about activity
* an EEG may show abnormal brain activity that is
indicative of a seizure
How do you determine the quality of spatial resolution (high or low)?
EEG, fMRI or Single cell recording, which one has the highest SR?
How precisely can you determine where something is
or occurred – more precise, higher the SR
To how small a region in space can you resolve 2
locations – smaller the region, higher the SR
WHERE – smaller the region, higher the SR
- EEG can provide information about brain activity
localised to several centimetres – low SR - fMRI can provide information at the mm level –
high SR - Single cell recordings provide information at the
micro level – super high SR
How do you determine the quality of temporal resolution (high or low)?
EEG, fMRI or Single cell recording, which one has the highest TR?
How precisely can you determine when something
happened – more precise, higher the TR
To how small an interval of time can you resolve 2 events
– smaller the interval, higher the TR
WHEN – smaller the interval, higher the TR
* fMRI can tell you when something occurred within
seconds – low TR
* EEG can tell you when something occurred within ms –
high TR
* Single cell recordings can tell you when something
occurred within microseconds (or faster) – super high
TR
What is a startle response? and what does it measure?
Measures physiological response.
* Loud noise -> BLINK
* Brainstem reflex for
protection
* The fear-potentiated
startle - amplitude is
increased when
presented with a cue
that has been
previously paired with
an aversive stimulus
* Measure fear
conditioning
what are the four ways of measuring a behavioural response in the brain?
- Reaction times
- Detection thresholds
- Stimulus discrimination
- Psychophysics – relationship between physical
stimuli and mental phenomena
What is Electrodermal Activity? and what does it measure?
- Fight or flight response
- Index of autonomic activity
– measure of emotional
arousal - Skin momentarily becomes
a better conductor
What is stimulating/disrupting activity? and what kind of information does it provide?
- tDCS
- Drug blocks
- Cryogenic block
- TMS
Stimulating or disrupting activity typically provides
CAUSAL information
What is TDCS? what is the role of cathode and anode in behavioural performance of the brain?
Transcranial Direct Current Stimulation
* Small current between anode (+) and
cathode (-)
* Transiently disrupt neural activity
* Neurons under anode become
depolarised – more likely to fire
* Neurons under cathode become
hyperpolarised – less likely to fire
* Changes in behavioural performance –
general – anodal improves, cathodal
hinders
What is the function of “drug blocks” and “cryogenic block”?
Drug Blocks
* Injection of local anaesthetics
* Wada test
* Prior to ablative surgery – determine
lateralisation of vital functions (e.g. speech)
* Inject left or right internal carotid then assess
Cryogenic Block
* Cryoprobe cools neurons near tip so they
stop firing – virtual lesion
* Invasive
Transcranial Magnetic Stimulation
Single magnetic pulses are
applied to specific locations on
the scalp at specific times during
a behavioural task; or
repetitively prior to task
performance (rTMS).
- Magnetic activity causes
neurons to fire – focal
stimulation - cognitive or
behavioural consequences are
then observed
what is the stimulation disruption and repetitive effects of TMS?
- Stimulation effects (e.g. motor or
visual activation) - Disruption effects - synchronised
discharge interferes with normal
activity – timing important (e.g.
disrupt letter recognition) - Repetitive (rTMS) – longer effects
– maybe related to LTP/LTD but
unclear - Permits causal inference about
the necessity of a specific brain
region for performing a given
task. - rTMS in clinical – depression and
neuropathic pain
What is MEG?
Magneto-encephalography (MEG)
* Electric currents generate small magnetic fields
* Measure at the scalp
* Very high temporal resolution
* Relativity direct measure of activity
* But … no good for subcortical, hard to model
sources, very expensive equipment
What is EEG?
Electroencephalography (EEG)
* Electrical activity generates electric
fields which can be measured
* Scalp – measures gross electrical activity
of the brain
* Sum of electrical events – action
potentials, postsynaptic potentials,
muscle activity, etc
* Measured electrical activity correlates
with underlying neural activity
What is ERP?
- Research – waveforms that
accompany an event (onset of a
stimulus or response – evoked) - Time lock to the event
- Small signal embedded in noise – so
average lots of trials to clean and
extract signal - Best for time course of events rather
than location (but can do source
modelling) - Name peaks based on polarity – N (negative) or P (positive)
- But note – weird convention that N is up!
What are the advantages of EEG?
Advantages
* High temporal resolution
* Measure of activity
* No drugs, tracers - non invasive
* Relatively low cost
What are the disadvantages of EEG?
Disadvantages
* Low spatial resolution (although
source modelling possible)
* Poor for activity below
superficial layers (cortex – gyri)
* Low signal to noise and signals
easily contaminated – need lots
of trials and lots of subjects –
time consuming
What is Diffusion Tensor Imaging (DTI)?
- Variant of MRI
- Measures density
and motion of water
molecules –
restricted movement
along axon fibres - Measure diffusion
anisotropy
What is Neurovascular coupling in fMRI?
coordinated response to brain activation
involving local capillary dilation and a transitory surge in the flow of
oxygenated, glucose-containing blood across the neurovascular unit,
thereby replenishing ATP used in neurotransmission
How does fMRI capture a functional image of the brain?
Measures neural activity (indirectly)
Neurovascular coupling
Active neurons – blood flow increases bringing oxyhemoglobin
* Oxyhemoglobin increase greater than oxygen consumption increase so
increased ratio oxy to deoxy in veins
* Oxy and deoxy different magnetic properties
* Less deoxy relative to oxy – MR signal increased intensity – BOLD – blood
oxygen level dependent contrast
What are the four advantages of fMRI?
Compared to PET - no tracers,
better temporal and spatial
resolution, faster acquisition.
* No known health risks.
* Structural and functional
information in the same image.
* 3-D images of activity over the
whole brain
What are the four disadvantages of fMRI?
Low temporal resolution
* Indirect measure of neuronal
activity – correlated but
relationship between BOLD and
neural activity complex and
variable
* 2-3 seconds to create an image
* Not causal
