Instrumentation|Electronics Flashcards
What is Ohm’s Law?
Voltage (V) = Current (I) x Resistance (R)
What is the Nyquist Theorem?
Sampling rate of an EEG amplifier should be at least 2x the highest frequency being recorded.
What is the sampling rate of most EEGs?
256 samples per second
What is aliasing?
Distortion that occurs when the sampling rate is too low to be reconstructed into its actual form
What is alternating current?
Electrical current that periodically reverses direction.
Household sockets are an example of what type of current?
Alternating
EEG originates as a ______ current but emerges as a ______ current.
direct; alternating
What word describes rate of electron flow or current?
Amperage
What is amperage?
Rate of electrical flow (electrons) or current (i.e., quantity of electrical charge).
Amperage is measured in what units?
Amps (Amperes)
What defines 1 amp/ampere?
The number of coulombs of electrical charge that travel through a conductor per second.
What defines a wave’s amplitude?
Deviation from resting state (distance between baseline and crest or trough).
Amplitude is a measure of a wave’s ______.
power
Amplitude is measured in _______.
millivolts (mV)
A millivolt (mV) is equivalent to ______ volts.
one one-thousandth (1/1000)
What is capacitance?
The ability of a system to store an electrical charge
Static shock is an example of ______.
Capacitance
Capacitance is measured in what units?
Microfarads (mfd)
What is coherence?
Co-variation of phase between a pair of signals at a specific frequency
What word describes co-variation of phase between a pair of signals at a specific frequency?
Coherence
What is direct current?
Current that only flows in one direction
Current that only flows in one direction is called what?
Direct current
Current that reverses direction is called what?
Alternating current
What term describes which frequency within a component band has the greatest share of voltage or power?
Dominant frequency
What is dominant frequency?
The frequency within a component band that has the greatest share of voltage or power
What word describes the number of cycles a wave completes per second?
Frequency
What defines a wave’s frequency?
The number of cycles it completes per second
What is the unit of measurement for frequency?
Hertz (Hz)
What is impedance?
Resistance to an alternating current
In an EEG, excessive impedance causes ______.
artifact
What word describes the amount of energy available in an electrical current?
Power
Power is measured in what units?
Watts
What does resistance refer to?
Resistance in direct current
Resistance and impedance are measured in what units?
Ohms
What is voltage?
The amount of electrical potential between two locations with different electrical charges.
What word refers to the amount of electrical potential between two locations with different electrical charges.
Voltage
Voltage is measured in ______.
Volts
What word describes wavelength?
Period
What defines a wave’s wavelength or period?
The time it takes to complete one cycle
What term describes how electrical current travels from the brain to the scalp?
Volume conduction
What is volume conduction?
How current flows from the brain to the scalp
What does phase refer to?
The degree to which waveforms rise and fall synchronously
The degree to which waveforms rise and fall synchronously is called ______.
Phase
Approximately how many neurons are required to fire synchronously to produce enough amplitude to be recorded on the scalp’s surface?
60 million
EEG has better ______ but less precise ______ than alternative forms of neuroimaging.
temporal resolution; spatial resolution
One thing that EEG can measure, which other methods cannot, is ______ .
network connections
EEG translates a ______ signal into a ______ signal.
analog, digitized
What neuroimaging technique measures electrical activity of the brain via electrodes placed on the scalp?
EEG
What neuroimaging technique provides high-resolution images of brain anatomy using magnetic fields and radio waves?
MRI
What neuroimaging technique measures changes in blood oxygenation levels to infer brain activity?
fMRI (functional Magnetic Resonance Imaging)
What neuroimaging technique involves injecting a radioactive tracer into the body which emits positrons? As positrons collide with electrons, they produce gamma rays that are detected by the scanner, allowing for the visualization of metabolic and physiological processes in the brain. Commonly used to study brain function such as glucose metabolism and neurotransmitter activity.
PET (Positron Emission Tomography)
What neuroimaging technique is similar to PET but only uses a single photon?
SPECT (Single Photon Emission Computer Tomography)
What neuroimaging technique measures the magnetic fields generated by the electrical activity of neurons, similar to EEG but with superior spatial resolution?
MEG (Magnetoencephalography)
EEG and MEG are both examples of what type of neuroimaging technique?
LORETA (Low-Resolution Electromagnetic Tomography)
What type of neuroimaging technique provides a three-dimensional reconstruction of the electrical activity of the brain, particularly useful for studying the dynamics of brain oscillations and identifying the neural sources involved in specific cognitive processes or neurological disorders?
LORETA (Low-Resolution Electromagnetic Tomography)
What does LORETA stand for?
Low-Resolution Electromagnetic Tomography
Voltages of electrical signals at the cortex are in the ______ range but, because the skull has a lot of resistance, these signals are in the ______ range at the scalp.
millivolt; microvolt
Why are differential amplifiers necessary for EEGs?
To increase the amplitude of brainwaves on the scalp to a range that is detectable.
Amplifiers ______ the amplitude of brainwaves.
increase
What is common mode rejection?
Process used by differential amplifiers in which signals common in two lines of polarity (e.g., electrode and reference point) are rejected to produce a singular output.
The process used by differential amplifiers in which signals common in two lines of polarity (e.g., electrode and reference point) are rejected to produce a singular output is called ______ .
common mode rejection
What makes a filter analog?
It has physical components.
What makes a filter digital?
It’s components are virtual.
What is the difference between infinite response filters and finite impulse filters?
Infinite response filters are faster but create distortions, while finite impulse filters are slower have little to no distortion.
Infinite response filters and finite impulse filters are both ______ filters.
Digital
Filters that have wide skirts (and are therefore less selective) are called ______ .
Low order filters
What is a low order filter?
A faster filter with a wide (less selective) skirt.
A low order filter is typically used for _______ .
beta training
What is a high order filter?
A slower filter with a narrow skirt
A slower filter with a narrow skirt is called a ______.
high order filter
What type of filter would be used for slow wave training like alpha theta?
a high order filter
_______ is the default filter in most neurofeedback software.
Butterworth
What is a high pass filter?
A filter that allows frequencies higher than .5 Hz to pass
What type of artifact can be removed by a high pass filter?
Slow wave artifacts such as eye blinks and eye movements
What is a low pass filter?
A filter that allows frequencies lower than 40 Hz to pass
What is a notch filter?
A filter that blocks out a specific frequency
Electrical outlets in the United States produce artifact at a frequency of ______ Hz.
60
Electrical outlets outside of the United States produce artifact at a frequency of ______ Hz.
50
What are two ways of calculating the magnitude of a signal?
Peak-to-Peak or Root Mean Square (RMS)
Peak-to-Peak measures magnitude from _______ to _______.
The highest peak to the lowest peak.
______ measures the average value of a signal and represents the equivalent constant value of the signal that would deliver the same power as the original signal.
Root Mean Square (RMS)
What is the mathematical relationship between Root Mean Square (RMS) and Peak-to-Peak?
RMS x 2.828 = Peak-to-Peak
A montage that uses only one sensor on the scalp is called either a ______ or ______.
monopolar montage; referential montage
In a monopolar montage, activity at a single site is compared against _______.
one or more reference points
Linked ears montage is an example of a ______ montage.
monopolar
Two-channel training actually uses ______, with each electrode connected to the ipsilateral earlobe as its reference point.
two monopolar montages
A _______ montage uses two sensors on the scalp connected to a single reference point
bipolar
What is a bipolar montage?
A montage that uses two sensors on the scalp connected to a single reference point
What is a bipolar montage used for?
Comparing activity at two different locations
Bipolar montages may be ______ or ______.
transverse (comparing hemispheres); longitudinal (comparing front to back)
What is a Laplacian montage?
A montage where multiple sensors are placed around a site to cover a localized region.
A montage that uses multiple sensors around a site to cover a localized region is called a ______.
Laplacian montage
What is the most common source of artifact?
Muscular tension
What causes electrodermal or bridging artifacts?
Sweat
Electrostatic artifacts are more common in climates with how much humidity?
<30%
What is Breach Rhythm?
Artifact caused by skull defect that shows as faster, localized rhythms
Artifact caused by EKG or pulsing arterial flow beneath the scalp is stronger in which hemisphere?
The left
Fz is located ___% from Cz (anteriorly) of the distance from ______ to ______.
20; nasion; inion
Pz is located ___% from Cz (posteriorly) of the distance from ______ to ______.
20; nasion; inion
Fp1/Fp2 are located ___% from the nasion of the distance between nasion and inion.
10
O1/O2 are located ___% from the inion of the distance between nasion and inion.
10
What points are located 10% away from the preauricular notches on each side of the head?
T3 and T4
Each point along the circumference is located ___% of the total circumference away from proximal sites.
10
What percentage of the total circumference separates Fp1 and Fp2?
10%
What point along the circumference is midway between O1 and T3?
T5
What point along the circumference is midway between O2 and T4?
T6
What point along the circumference is midway between Fp1 and T3?
F7
What point along the circumference is midway between Fp2 and T4?
F8
Where is F3 located?
Midway between Fz and F7
Where is F4 located?
Midway between Fz and F8
What point is located midway between Pz and T5?
P3
What point is located midway between Pz and T6?
P4
A derivation of the 10-20 International System that includes 74 focal sites is called the ______.
Modified Combinatorial Nomenclature
What is the Modified Combinatorial Nomenclature?
Derivation of the 10-20 International System that includes 74 focal sites
An EEG measures electrical activity occurring on what part of the brain?
Cortex/Cerebrum
In general, which anatomical region contributes the least amount of EEG activity to the recording?
Earlobes or mastoid process
What is the function of differential amplifiers?
Rejects signals that are the same to reveal only those that are different.
True or false:
After the signal is amplified with the differential amplifier, the signal is free from artifacts.
False
What type of montage records the difference between an electrode and the weighted average of the surrounding electrodes?
Laplacian montage
What is the minimum number of sensors needed to get a signal?
3 (electrode, reference, ground)
What type of montage records sequences of active electrodes?
Sequential or bipolar montage
Fp1 is what percentage of the total circumference from Fp2?
10%
Why is the 10-20 International System of Electrode Placement important?
The system is recognized universally, creating comparable measures of electrode locations for different persons.
Amplitude is a measure of _____, and wavelength defines the _____ in EEG metrics.
power; period
The initial QEEG is a _____ signal, while the final QEEG is a _____ signal.
analog; digital
What type of resolution is superior in EEG compared to other neuroimaging techniques?
Temporal
What type of resolution is inferior in EEG compared to other neuroimaging techniques?
Spatial
What defines whether two active sites are in or out of phase?
Whether or not amplitudes rise and fall together.
What is the mathematical relationship between RMS and Peak value?
RMS = .707 x Peak Value
What is the mathematical relationship between Peak and Peak-to-Peak values?
(Peak Value) x 2 = Peak-to-Peak
What is the most common location for reference electrodes to be placed?
Earlobes
True or false:
EEG can be performed using either one or two reference points.
True
True or false:
The ground electrode may be placed anywhere above the shoulders.
True
What is an alternative term for bipolar montage?
Serial montage
What is spectral analysis?
Real-time visual displays of brain wave performance during EEG
QEEG is an example of _____ analysis.
neurometric
Peak EEG power reaches its climax at around what time of day?
Noon
Fast Fourier Transforms (FFT) report what type of signals?
Digital
What term refers to the relationship between two waves with respect to synchrony?
Phase
