5. Techniques in Neuroscience Flashcards
Define electrophysiology
Branch of physiology that deals with electrical phenomena associated with nervous and other bodily activity
Define single unit recording
Studies the electrical activity of individual neurons (one single neurone) - in animals
Define multi-unit recording
Studies the composite electrical activity of groups of neurons (e.g. fiber pathway) - neurons acting at the same time - in animals
Define EEG recording
Studies the low frequency, composite electrical activity of unspecified origin at select brain regions
What does single unit recording use and electrode for?
To record the electrophysiological activity from a single neuron
What does the electrode detect (single unit recording)?
Electrical activity generated by the neurons adjacent to the electrode tip
What does single unit recoding allow researchers to understand?
How individual neurons code information
Are Electroencephalograms (EEG) invasive?
No
What do EEGs measure?
Voltage differences at the scalp in the microvolt range
Describe EEGs in terms of spatial resolution
Spatial resolution is poor as multiple neurons are under one electrode so they aren’t very specific
Describe EEGs in terms of temporal resolution
Terrific - 1ms delay
Why are EEGs used?
Detecting changes in brain patterns
Can average several readings to obtain evoked potential
Often used for detecting epilepsy
EEG signals reflect what?
Global brain states
Large background oscillations of the EEG trace make it impossible to do what?
Detect evoked response from a single trial
By averaging from hundreds of trials, the background EEG is removed, which leaves what?
Event-related potentials
What is an event-related potential (ERP)?
The measured brain response that is the direct result of a specific sensory, cognitive or motor event
EEGs measure the population responses of how many neurons?
Millions
EEG signal is directed related to what type of activity?
Neural activity
Neural activity consumes what as well as generating electrical signals?
Oxygen
What does PET measure?
The blood flow in a region
What does fMRI measure?
Blood oxygenation
The time taken for changes in blood flow is slow (several seconds) so therefore imagine has poor….
Temporal resolution
Cerebral blood flow (CBF) is the basis of what type of technique?
fMRI
The cortex is densely packed with…
Blood vessels
What does the distribution of blood vessels mirror?
Neuronal organisation
At what level does PET measure blood flow?
Locally
PET is a form of what type of functional brain imagine?
Hemodynamically-based
Before PET, a subject is given a radioactively….
Tagged substance
PET will compute the locations of…
Decaying radioisotopes that emit game rays
From PET we can infer higher regional cerebral blood flow in areas that emit what?
Many positrons
How long does the tracer take to peak for PET?
up to 30 seconds
Give 4 limitations of PET
- Limited spatial resolution
- No temporal resolution
- Exposure to radiation
- Access to a cyclotron
What does fMRI stand for?
Functional Magnetic Resonance Imagine
What does fMRI measure?
Local blood flow
fMRI measures the concentration of what in the blood?
Deoxyhemoglobin
What is the BOLD response?
the Blood Oxygen Level Dependent contrast
The change in BOLD response over time is called the…
Haemodynamic response function
How many seconds does it take the haemodynamic response function to peak and what does this mean for temporal solution?
6-8 seconds and therefore a low temporal solution
Magnetic field strength is measured in what?
Tesla (T) Gauss (G)
1 Tesla = n G
n = 10,000
The brain has a constant supply of blood flow and therefore to determine if an area is active, one must compare…
Relative differences in brain activity between two or more conditions
fMRI determines that a region is ‘active’ if it shows what?
A greater response in one condition relative to another
List 4 limitations of fMRI
- Lacks spatial and temporal resolution
- Is not a direct measure of neural activity
- The precise link between CBF and neural activity is not yet known
- Caution must be taken in the interpretation of fMRI measurements
What does TMS stand for and what does it do?
Transcranial Magnetic Stimulation & it uses electro-magnetic induction via coils to temporarily disrupt cortical function
What does TMS impair and how is this useful to infer?
It impairs local processing and we can therefore infer what this area is used for
The TMS coil contains a wire carrying…
Electrical current
A rapid change in current creates what?
A magnetic field
The magnetic field induces what?
A current in the nearby neurons
Which areas can TMS stimulate?
Those near the cortical surface
