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42 Cards in this Set
- Front
- Back
aliasing
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a sampling rate which is too slow will make the signal appear to be running at a slower frequency than it actually is
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low pass filter
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meant only to let through waves below a cut point; for many instruments this is set at 32 HZ
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band pass filter
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frequency ranges chosen by the practitioner to use for statistical comparison or for neurofeedback
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sequential or bipolar montage
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two electrodes each attached to an active scalp site; shows the difference in activity between the two active sites on the head
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resistence
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measure of how much circuit components restrict the passage of a direct current
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Variance
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is the square of the SD/standard deviation
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Impedance
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resistance of circuit elements to the passage of alternating current (AC)
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Referential (monopolar) montage
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shows activity at one active site on head by subtracting noise or other artifact common to both sensors (ground, reference)
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Power
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voltage (v) * current (I)
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Ohm's Law
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the amount of current or amperes in a conductor is equal to the voltage (v) the "push" or "pull" divided by the resistance (R) in ohms
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sensitivity
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ratio of input voltage to the change in the signal as it is displayed
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capacitance
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storage of electrical energy on 2 parallel plates of conductive material separated by an insulating material
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electrode impedence
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resistance to alternating electrical current flow
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Gain
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refers to a ratio of the voltage of a signal at the output of the amplifier to the voltage of the signal at the input of that amplifier
10V/10uv = 1 million |
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Phase
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calculation of the time shift between EEG activity in two brain regions; delays increase with age
short front to back delays correlate with higher IQs |
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Pearson Product Correlatin Coefficient or Comodulation
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degree of association in magnitude between signals from 2 different sources or sites
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Relative Power
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comparison of frequency band power to total EEG power
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Power
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uV squared within a band or total EEG power
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Amplitude
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amount of enery of electrical discharge measured within a specific frequency band or the EEG as a whole
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Common Reference Montage
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excellent for detection of widely distributed currents and for analyzing aymmetry. Also good for the detection of artifacts
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Optical isolation
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Process where you separate the encoder from the computer by a glass wire. Digital current from the encoder is changed to an optical form for transmission to the computer
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sequential (bipolar) and Laplacian montages
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montage good for viewing highly localized activity
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montage/reformatting
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process where we take different views of the same data, refrencing one electrode site to another or combination of sites
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Fast Fourier Transform Filter (FFT)
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take the EEG information and mathmatically transform it to give it an average voltage for a specific frequency over a specified time frame.
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What are the 3 types of digital filters?
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1. Final impulse response (FIR)
2. Infinite impulse response (IIR) 3. Fast Fourier Transform (FFT) |
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Nyquist principle
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The maximum frequency that can be reconstructed in a filter is based on this. It is half the sample rate frequency
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Nyquist principle
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states that the sampling rate must be at least twice the maximum bandwidth of the analog signal in order to allow the signal to be completely represented.
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Common mode rejection
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ratio of common mode input voltage divided by the output voltage. Ratio should be greater than 100,000.
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High pass band filter
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meant to attenuate the waves or reduce the amplitude of the waves that come in at a frequency below the cut-off. It lets "pass-through" waves higher than the cut-off frequency
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Sampling
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change the alternating analog current to the digital form that the computer can work with
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Preamplifier
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Amplifies the microvolt different by more than 100,000 times and does not amplify other electrical signals
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electrical charge
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refers to the negative charge carried by electrons
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Sensitivity
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ratio of input voltage to the change in the signal as it is displayed
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Impedence is measured using:
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alternating current in the alpha range
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Impedence requires measurement of several factors including:
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resistance of the conductor, capacitance, inductance, and the frequency of the alternating current
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What does current measure?
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the rate of transfer of electric charge from one point to another
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Compares adjacent pairs of electrodes in the 10-20 system; these may be either longitudinal pairs (F3-C3) or transverse pairs, going across the head (C3-CZ)
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Sequential or Bipolar Montage
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Active reference montage using common average reference, will reference an active electrode to an average of all other electrodes
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Laplacian or Global Average Montage
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Will reference to the average of the electrodes immediately surrounding each active electrode.
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Laplacian or Hjorth Montage
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What is power?
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The square of magnitude (average amplitude for a specific epoch) within a frequency band over resistance
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Absolute amplitude in scalp EEG
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amount of electrical activity in a given frequency band
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Relative or percent power
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amount of EEG band power as a percentage of the total signal
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