Electophysiological Evaluation Flashcards
This is known as an electrical potential which occurs in the cortex AFTER stimulation of a sense organ
Evoked Potential (i.e. SEP, ABR, VEP)
This records spontaneous brainwaves to ALL stimuli
Electroencephalogram (EEG)
This records brainwaves to a time-locked stimulus of interest (i.e. event). Electrodes are placed on the human scalp.
Event-Related Potential
What are the 4 goals of ERP?
- Amplification of response
- Filtering of potentials
- Segmenting response to each stimulus
- Averaging responses
Where are the electrodes placed to record the appropriate response at each location?
- Front
- Central
- Parietal
ERPs are used to index/assess the timeline ___ and ___ processing.
sensory and cognitive processing
The ERP response provides what 4 factors?
- Latency
- Amplitude
- Morphology
- Topography
This factor is the time to the first negative peak
Latency
This factor is the depth of the response (peak to peak)
Amplitude
this factor is how “nicely” the graph looks, how clear the signal was.
Morphology
This factor is where the specific activity occured.
Topography
What is the most clinically used ERP for audition?
ABR = auditory brainstem response
How many positive peaks are found in ABR? Latency?
5-7 positive peaks
8-10ms latency
This reflects the ability of the auditory nerve and pathway in the brainstem to detect sound.
Auditory Brain Response (ABR)
In this test, a patient hears a series of abrupt click sounds, bursts or phoneme.
ABR
Which peaks are crucial in ABR testing?
the first 5 peaks
When is wave 3 formed in an infant?
at 6 weeks of birth
- after 1 year, signal response is like adults
This indexes automatic detection of an auditory stimulus change; can be evoked by changes in tones, vowels and consonants; passive process
Mismatch negativity (MMN)
This can be elicited from an oddball arrangement of stimuli, when the participant ignores the stimuli (subliminal attention)
Mismatch Negativity (MMN) - passive attention
This is an important study in A.D.D patients
MMN
This assesses detection and overt discrimination of an infrequent event; can be divided into P3a and P3b; active attention
P300
This occurs to
- large differences in stimuli
- brief attention switch to variant,
- found whether participants are actively attending or not.
P3a
This occurs when:
- Participants carry out discrimination task
- Particip. is actively attending stimuli
P3b
This is elicited by an oddball paradigm; an unexpected stimulus in a series of expected stimuli
P300
This measures changes in magnetic fields that accompany electrical activity; maps brain activity, neuroimaging
Magnetoencephalography (MEG)
- via an intracellular current
This requires an injection of a positron-emitting radioactive isotope; short half-life, shows location in brain being used
Positron Emission Tomography (PET)
This uses radio frequency information given off by water, allows fast acquisition of complete image slice in 20ms, uses radio frequency information given off by water, better time and spatial resolution
Magnetic Resonance Imaging (MRI)
If a patient has a decrease in P300 latency, this means?
There’s an increase in cognitive capacity and attention skills
A PET scan shows the ________
Shows the location of the brain being used, but not the function.
What type of person is an ERP good for?
Useful for hard to test populations (non-verbal, impaired, infants)
