Methods of measuring brain function Flashcards
what are single cell recordings used for
to measure electrical signals (action potentials) from a single neuron or a few neurons
what species are single cell recordings often used in
typically animals such as rats and monkeys, but can also be used in epilepsy patients
what can single cell recordings tell us
what a specific neuron responds to
what can’t single cell recordings tell us
anything about the neural network or populations of neurons
are single cell recordings invasive
yes
is the spatial resolution of single cell recordings good
yes
what is meant by spatial resolution
how accurately a method can tell us where something is happening in the brain
what does it mean if a method has good spatial resolution
it can pinpoint brain activity to a very specific region or structure of the brain
what is temporal resolution
how accurately a method can tell us when something is happening
what does it mean if a method has high temporal resolution
we can detect changes in brain activity in milliseconds
what does it mean if a method has low temporal resolution
there is a lag between the brain activity and when we detect it
what is a direct measure
measures brain activity as it is happening
what is an indirect measure
doesn’t record neural activity itself, but instead infers activity from something associated with it - such as changes in blood flow or oxygen levels
what is a structural measure
a structural method looks at the anatomy or physical structure of the brain.
what does a structural method tell us
what the brain looks like, rather than what its doing
what is a functional method
measures brain activity (what the brain is doing during tasks, rest, or in response to stimuli)
what is meant by an invasive method
involves entering the body or penetrating the skull
what is a non-invasive method
does not require surgery or physical intrusion
what is the temporal resolution like in single cell recordings
good
are single cell recordings direct or indirect
direct
are single cell recordings structural or functional
functional
what brain property do single cell recordings measure
electrical activity
what are the two electophysiology methods
- EEG
- Single cell recordings
what does EEG measure
the electrical activity of large populations of neurons
what are two typical uses of EEG
- measuring oscillations (e.g. during sleep)
- neuronal responses to stimuli (e.g. ERP studies)
what is an ERP study
a type of EEG study that measures brain responses that are directly related to specific sensory, cognitive, or motor events by averaging EEG data across multiple trials
what does ERP stand for
event related potential
what does an ERP study measure
brain’s electical activity in response to a specific task or stimulus
how does an ERP study improve signal to noise ratio
by averaging EEG signals across many trials (typically 50-100), the consistent signal (event related activity) emerges while random noise is averaged out
example of an ERP component
the N170 component
what is the N170 component
a negative voltage spike occurring 170ms after seeing a face, associated with face perception
what can EEG tell us
when groups of neurons respond and aid in diagnosis
what diagnoses can EEG aid in
sleep disorders, epilepsy
what can’t EEG tell us
activity of individual neurons or precise source locations of the signals
what is the signal to noise problem in EEG
the desired neuronal signal is often overpowered by background brain activity (noise)
how do we overcome EEG signal to noise problem
by averaging multiple trials (usually 50-100) using Event Related Potentials
is EEG invasive
no
is spatial res good for EEG
no
is temporal res good for EEG
yes
is EEG structural or functional
functional
what brain property does EEG measure
electrical activity
what does MRI measure
structural properties in the brain
what does MRI do
detects how hydrogen protons in water and fat realign with a magnetic field after bing distributed
how big is an MRI magnet
typically 3 Tesla, approx. 50,000 Times stronger than earth’s magnetic field
what can structural MRI tell us
anatomy,, brain volume (in voxels), structural abnormalities such as tumours or degeneration
can MRI detect brain activity
no, its structural
is MRI invasive
no
is MRI estrutural or functional
structural
what brain property does MRI rely on
magnetic properties of Hydrogen atoms
what does fMRI stand for
Functional MRI
what does fMRI measure
blood oxygenation levels (BOLD signal), an indirect measure of neural activity
what is the bold signal
B - blood
0 - Oxygen
L - Level
D - dependent
what does the bold symbol do
reflects changes in oxyhemoglobin and deoxyhemoglobin
what is the makeup of oxyhemoglobin
haemoglobin + oxygen
what is the makeup of deoxyhemogolbin
haemoglobin - oxygen
why is haemoglobin magnetic
it contains iron
why does neural activity increase the BOLD signal
active neurons consume more oxygen, and the brain overcompensates by increasing oxygen-rich blood flow
what can fMRI tell us
which brain areas are active during a task and how they interact as networks
what can’t fMRI tell us
whether a brain area is essential to a task or the exact timing of activity
is fMRI invasive
no
what is the spatial resolution of fMRI
good
does fMRI have good or bad temporal resolution
poor
is fMRI direct or indirect
indirect
is fMRI structural or functional
functional
what brain property does fMRI measure
hemodynamic (blood flow and oxygen)
what is the hemodynamic response function (HRF)
it describes how blood flow changes in response to neural activity, forming the basis of the BOLD signal in fMRI
what are the stages of the HRF
- begins 1-2 seconds after neural activity
- returns to baseline around 12-20 seconds
- may include an initial undershoot
why is HRF important for fMRI interpretation
it shows the delay and indirect nature of fMRI signals, explaining its poor temporal resolution
what does TMS stand for
transcranial magnetic stimulation
what does TMS do
stimulates brain regions using a magnetic field to induce neuron firing - creating a “virtual lesion”
why use magnetic rather than electrical stimulation
magnetic fields pass through the skull more effectively than electrical currents
what can TMS tell us
which brain areas are involved and essential for spatial tasks
what can’t TMS do
stimulate deep brain regions
how deep can TMS stimulate
limited to 2cm beneath the scalp
is TMS invasive
no
is spatial resolution good or bad in TMS
moderate
temporal resolution in tMS
good
is TMS direct or indirect
direct
is TMS structural or functional
functional
what brain property does TMS interact with
electromagnetic properties (induces action potentials)
example of TMS in research
disrupting the right occipital face area impaired face recognition, showing its role in early face processing
what does N170 stand for
N = negative
170 = time after stimulus onset (ms)
what in our cells contain protons
hydrogen atoms
what happens when MRI is turned on
makes the protons from our cells line up, then the scanner gives the body a blast of radio waves, which changes the orientation of the protons by 90 degrees
what is the mr signal
when hydrogen protons return to their original alignment
what does the mr signal stand for
magnetic resonance signal
why do tissues look different on MRI scan
protons in different tissue relax at different rates
difference between fat and water cells relaxation times
water: long relaxation times
fat: short relaxation times
what does fNIRS stand for
functional near infrared spectroscopy
what does fNIRS do
detect blood oxygenation changes
how does fNIRS work
near-infrared light emitted into the scalp and absorbed differently by oxy- and deoxyhemoglobin. detectors measure the light that returns, allowing estimation of blood oxygenation
is fNIRS direct or indirect
indirect
is fNIRS invasive
no
advantages of fNIRS
portable, cheap, good for studying infants or during movement
limitations of fNIRS
limited to cortical surface, slower than EEG
what kind of brain property does fNIRS measure
hemodynamic
is MRI invasive
no
does MRI use ionising radiation
no
what is a voxel
a 3d pixel, a small cube representing a volume of brain tissue in an MRI scan
how is the spatial resolution of fMRI
high - can detect fine anatomical details (often 1mm cubed voxels or smaller)
how is the temporal resolution of MRI
very poor
