BCIA Instrumentation & Technology 1 — Questions and Answers
Question 1: What is the primary purpose of a differential amplifier in biofeedback instrumentation?
- To increase signal frequency
- To reject common-mode noise and amplify the difference between two inputs (Correct answer)
- To convert analog signals to digital
- To store biosignal data
Correct answer: To reject common-mode noise and amplify the difference between two inputs
A differential amplifier rejects common-mode electrical noise while amplifying the difference between the active and reference electrodes.
Question 2: Which electrode placement standard is most commonly used in EEG-based neurofeedback?
- American Montage
- International 10-20 System (Correct answer)
- Bipolar Referential Array
- Modified Combinatorial Nomenclature
Correct answer: International 10-20 System
The International 10-20 System is the universally accepted standard for electrode placement in EEG and neurofeedback practice.
Question 3: What does impedance checking before a biofeedback session primarily ensure?
- The client is relaxed
- Good electrical contact between electrodes and skin (Correct answer)
- The equipment is calibrated
- Signal bandwidth is correct
Correct answer: Good electrical contact between electrodes and skin
Low impedance between electrodes and skin ensures minimal signal distortion and high-quality biosignal acquisition.
Question 4: EMG biofeedback electrodes are typically placed how far apart on a muscle?
- 1 cm
- 2–4 cm (Correct answer)
- 10 cm
- 20 cm
Correct answer: 2–4 cm
A spacing of 2–4 cm between surface EMG electrodes captures localized muscle activity with minimal cross-talk from adjacent muscles.
Question 5: What artifact commonly contaminates surface EMG recordings?
- Cardiac artifact (ECG) (Correct answer)
- Respiration artifact
- Eye blink artifact
- Thermal artifact
Correct answer: Cardiac artifact (ECG)
The electrical signal from the heart (ECG) can superimpose on surface EMG, particularly when recording from trunk muscles.
Question 6: A sampling rate of at least twice the highest frequency of interest is described by which principle?
- Ohm's Law
- Nyquist Theorem (Correct answer)
- Fourier Transform
- Weber's Law
Correct answer: Nyquist Theorem
The Nyquist Theorem states that the sampling rate must be at least twice the highest signal frequency to accurately reconstruct the waveform.
BCIA Instrumentation & Technology 1
What is the primary purpose of a differential amplifier in biofeedback instrumentation?