Q.1 What does EEG stand for in neural signal measurement?
Electroencephalogram
Electrocardiogram
Electromyogram
Electrooculogram
Explanation - EEG records the electrical activity of the brain via scalp electrodes.
Correct answer is: Electroencephalogram
Q.2 Which type of electrode is typically used for surface EMG recordings?
Needle electrode
Silver‑silver chloride (Ag/AgCl) surface electrode
Depth electrode
Microelectrode array
Explanation - Ag/AgCl surface electrodes provide low impedance and stable recordings for EMG.
Correct answer is: Silver‑silver chloride (Ag/AgCl) surface electrode
Q.3 According to the Nyquist theorem, what is the minimum sampling rate needed to accurately record a 500 Hz neural signal?
250 Hz
500 Hz
1000 Hz
2000 Hz
Explanation - Sampling rate must be at least twice the highest frequency component (2 × 500 Hz = 1000 Hz).
Correct answer is: 1000 Hz
Q.4 Which filter type is best for removing 60 Hz power‑line noise from neural recordings?
Low‑pass filter at 50 Hz
High‑pass filter at 70 Hz
Notch filter at 60 Hz
Band‑pass filter 0.1‑100 Hz
Explanation - A notch (band‑stop) filter centered at 60 Hz attenuates that specific frequency while preserving surrounding signals.
Correct answer is: Notch filter at 60 Hz
Q.5 What is the primary component of an action potential that is measured extracellularly?
Resting membrane potential
Depolarization peak
After‑hyperpolarization
Sodium influx
Explanation - Extracellular recordings capture the rapid voltage change associated with the depolarization phase.
Correct answer is: Depolarization peak
Q.6 In spike‑sorting, which algorithm is commonly used to cluster similar waveforms?
K‑means clustering
Fast Fourier Transform
Kalman filter
Wavelet denoising
Explanation - K‑means groups similar spike shapes based on Euclidean distance, aiding in unit identification.
Correct answer is: K‑means clustering
Q.7 What does the term ‘bandwidth’ refer to in the context of neural signal acquisition systems?
Number of electrodes
Frequency range over which the system accurately records
Amplitude range of recorded signals
Physical size of the electrode
Explanation - Bandwidth defines the lower and upper frequency limits the acquisition system can capture without distortion.
Correct answer is: Frequency range over which the system accurately records
Q.8 Which of the following is a major source of noise in intracellular recordings?
Thermal noise from the amplifier
Electrode polarization
Movement artifacts
Ambient light
Explanation - Polarization at the tip of a glass microelectrode introduces voltage offsets and drift.
Correct answer is: Electrode polarization
Q.9 A common reference electrode for EEG is placed at which location?
Cz (central)
Fz (frontal)
Mastoid
Nose tip
Explanation - Mastoid (behind the ear) provides a relatively neutral reference for scalp EEG.
Correct answer is: Mastoid
Q.10 What is the purpose of a differential amplifier in neural recordings?
To increase the DC offset
To amplify the difference between two inputs while rejecting common‑mode noise
To convert analog signals to digital
To filter out high‑frequency components
Explanation - Differential amplifiers boost the signal of interest and suppress noise common to both electrodes.
Correct answer is: To amplify the difference between two inputs while rejecting common‑mode noise
Q.11 Which transform is most useful for analyzing non‑stationary neural signals like event‑related potentials?
Fast Fourier Transform (FFT)
Laplace Transform
Wavelet Transform
Z‑Transform
Explanation - Wavelet analysis provides time‑frequency localization, ideal for transient neural events.
Correct answer is: Wavelet Transform
Q.12 What is the typical amplitude range of extracellular action potentials recorded with a microelectrode?
1‑5 µV
10‑100 µV
0.1‑1 mV
1‑10 mV
Explanation - Extracellular spikes are usually on the order of tens to a few hundred microvolts.
Correct answer is: 10‑100 µV
Q.13 When designing a neural recording system, why is input impedance of the amplifier important?
Higher input impedance reduces loading of the signal source
Higher input impedance increases power consumption
Lower input impedance improves signal‑to‑noise ratio
Input impedance does not affect recording quality
Explanation - A high input impedance prevents the amplifier from drawing current, preserving the weak neural signal.
Correct answer is: Higher input impedance reduces loading of the signal source
Q.14 Which of the following best describes a ‘common‑mode rejection ratio’ (CMRR) in amplifiers?
Ratio of signal gain to noise gain
Ability to reject signals present on both inputs
Maximum voltage the amplifier can output
Frequency range of the amplifier
Explanation - CMRR quantifies how well a differential amplifier suppresses common‑mode (identical) noise.
Correct answer is: Ability to reject signals present on both inputs
Q.15 In a typical EEG setup, what does the term ‘montage’ refer to?
The type of electrode material
The arrangement and referencing scheme of electrodes
The software used for analysis
The power supply voltage
Explanation - Montage defines how signals from various electrodes are combined or referenced.
Correct answer is: The arrangement and referencing scheme of electrodes
Q.16 Which method is most appropriate for reducing motion artifacts in long‑term neural recordings?
Increasing the gain of the amplifier
Applying a high‑pass filter at 0.5 Hz
Using a flexible, tethered electrode system
Implementing adaptive filtering based on motion sensor data
Explanation - Adaptive filters can dynamically cancel motion‑related noise by using reference signals from accelerometers.
Correct answer is: Implementing adaptive filtering based on motion sensor data
Q.17 What is the main advantage of using a microelectrode array (MEA) over a single microelectrode?
Lower cost
Higher spatial resolution and simultaneous multi‑site recordings
Simpler surgical implantation
Reduced power consumption
Explanation - MEAs enable parallel measurement from many neurons, providing richer spatial information.
Correct answer is: Higher spatial resolution and simultaneous multi‑site recordings
Q.18 Which of the following is a common artifact in EEG caused by eye movements?
Alpha rhythm
EOG (electrooculogram) artifact
Beta burst
Delta wave
Explanation - Eye movements generate large potentials that appear as EOG artifacts in EEG recordings.
Correct answer is: EOG (electrooculogram) artifact
Q.19 A 0.1 µF coupling capacitor is placed in series with the input of a neural amplifier. What is the effect on low‑frequency signals?
Amplifies them
Attenuates signals below approximately 1.6 kHz
Blocks DC and very low‑frequency components
Has no effect on frequency response
Explanation - The high‑pass cutoff frequency is 1/(2πRC) ≈ 1.6 kHz, so frequencies below this are attenuated.
Correct answer is: Blocks DC and very low‑frequency components
Q.20 In the context of neural signal processing, what does ‘spike‑triggered averaging’ achieve?
Enhances noise
Reduces the amplitude of spikes
Extracts the average waveform associated with a spike event
Increases the sampling rate
Explanation - Spike‑triggered averaging aligns and averages segments around spikes, improving signal‑to‑noise ratio.
Correct answer is: Extracts the average waveform associated with a spike event
Q.21 Which property of a neural signal determines the choice of a band‑pass filter between 300 Hz and 3000 Hz?
The dominant frequency of the signal
The amplitude of the signal
The electrode size
The temperature of the tissue
Explanation - Band‑pass limits are set to capture the frequency range where action potentials (spikes) have most energy.
Correct answer is: The dominant frequency of the signal
Q.22 What is the purpose of a ‘ground’ electrode in a neural recording setup?
To provide a reference potential for safety and noise reduction
To amplify the recorded signal
To inject current into the brain
To measure temperature
Explanation - Ground electrodes stabilize the circuit and help eliminate common‑mode interference.
Correct answer is: To provide a reference potential for safety and noise reduction
Q.23 Which signal processing technique can be used to detect the latency of evoked potentials?
Cross‑correlation
Principal Component Analysis
Histogram equalization
Linear regression
Explanation - Cross‑correlation aligns stimulus and response waveforms to estimate latency.
Correct answer is: Cross‑correlation
Q.24 What is the typical sampling resolution (bits) of a high‑performance neural data acquisition system?
8 bits
12 bits
16 bits
24 bits
Explanation - 24‑bit converters provide the dynamic range needed to capture both small spikes and larger field potentials.
Correct answer is: 24 bits
Q.25 During extracellular recording, why is the electrode tip size kept very small (few micrometers)?
To reduce tissue damage and improve spatial selectivity
To increase impedance and noise
To allow higher current injection
To simplify manufacturing
Explanation - A small tip minimizes disruption and captures signals from a limited neuronal population.
Correct answer is: To reduce tissue damage and improve spatial selectivity
Q.26 What does the term ‘signal‑to‑noise ratio’ (SNR) describe in neural recordings?
Ratio of electrode size to tissue size
Ratio of desired neural signal amplitude to background noise amplitude
Ratio of sampling rate to bandwidth
Ratio of DC offset to AC component
Explanation - Higher SNR means the neural signal stands out more clearly against noise.
Correct answer is: Ratio of desired neural signal amplitude to background noise amplitude
Q.27 Which type of artifact is introduced when a subject swallows during an EEG recording?
Muscle (EMG) artifact
EOG artifact
Cardiac (ECG) artifact
Motion artifact
Explanation - Swallowing activates neck muscles, producing high‑frequency EMG contamination.
Correct answer is: Muscle (EMG) artifact
Q.28 In neural signal processing, what is the purpose of ‘baseline correction’?
To increase the sampling rate
To remove DC offset before analysis
To amplify high‑frequency components
To change electrode impedance
Explanation - Baseline correction subtracts the mean (or trend) to center the signal around zero.
Correct answer is: To remove DC offset before analysis
Q.29 Which mathematical operation converts a time‑domain neural signal into its frequency‑domain representation?
Convolution
Fast Fourier Transform (FFT)
Integration
Differentiation
Explanation - FFT efficiently computes the discrete Fourier transform, revealing spectral components.
Correct answer is: Fast Fourier Transform (FFT)
Q.30 What is the main advantage of using a ‘bipolar’ electrode configuration in EMG?
It measures absolute voltage
It reduces common‑mode noise by recording the difference between two nearby sites
It increases the sampling rate
It eliminates the need for a ground electrode
Explanation - Bipolar recording subtracts signals from two electrodes, cancelling shared interference.
Correct answer is: It reduces common‑mode noise by recording the difference between two nearby sites
Q.31 A neural signal is digitized with a 12‑bit ADC and a full‑scale range of ±5 V. What is the voltage resolution per step?
0.0012 V
0.0024 V
0.0010 V
0.005 V
Explanation - Resolution = (10 V) / (2^12) ≈ 10 V / 4096 ≈ 0.00244 V; however because the range is ±5 V, the step size is 10 V / 4096 = 0.00244 V ≈ 0.0024 V. (Correct answer adjusted to 0.0024 V).
Correct answer is: 0.0012 V
Q.32 Which of the following best describes the term ‘local field potential’ (LFP)?
The voltage recorded from a single action potential
The low‑frequency (<300 Hz) component reflecting summed synaptic activity
The high‑frequency (>3000 Hz) noise floor
The DC offset of the recording system
Explanation - LFPs represent the collective, slower electrical activity of a neuronal population.
Correct answer is: The low‑frequency (<300 Hz) component reflecting summed synaptic activity
Q.33 When performing offline spike sorting, why is it common to first apply a high‑pass filter at ~300 Hz?
To remove the DC offset
To isolate the spike component from slower LFP activity
To increase the amplitude of the spikes
To reduce data size
Explanation - High‑pass filtering eliminates low‑frequency components, leaving the fast spike waveforms.
Correct answer is: To isolate the spike component from slower LFP activity
Q.34 Which electrode material is most commonly used for chronic intracortical recordings due to its biocompatibility?
Gold
Platinum‑Iridium alloy
Carbon fiber
Silver
Explanation - Pt‑Ir provides good conductivity, corrosion resistance, and tissue compatibility for long‑term implants.
Correct answer is: Platinum‑Iridium alloy
Q.35 What is the effect of increasing the gain of a neural amplifier beyond the optimal range?
Improved signal resolution
Signal clipping and distortion
Reduced noise floor
Higher sampling rate
Explanation - Excessive gain can push the signal beyond the ADC range, causing saturation.
Correct answer is: Signal clipping and distortion
Q.36 Which of the following is a typical frequency range for the alpha rhythm in EEG?
0.5‑4 Hz
4‑8 Hz
8‑13 Hz
13‑30 Hz
Explanation - Alpha waves dominate the 8‑13 Hz band, especially during relaxed wakefulness.
Correct answer is: 8‑13 Hz
Q.37 In a multi‑channel neural recording system, what does ‘crosstalk’ refer to?
Signal leakage from one channel into another
Electrical grounding failure
Electrode movement
Low battery voltage
Explanation - Crosstalk is unwanted coupling between channels, degrading isolation of recordings.
Correct answer is: Signal leakage from one channel into another
Q.38 Which algorithm can be used to denoise neural signals by exploiting sparsity in a transform domain?
Kalman filter
Wavelet thresholding
Median filter
Moving average
Explanation - Wavelet thresholding removes coefficients below a set level, preserving significant neural features.
Correct answer is: Wavelet thresholding
Q.39 What does the term ‘refractory period’ describe in the context of neuronal firing?
The time required for the neuron to recover after an action potential
The duration of the action potential
The latency between stimulus and response
The period of maximal excitability
Explanation - During the refractory period, a neuron cannot fire another action potential.
Correct answer is: The time required for the neuron to recover after an action potential
Q.40 When converting analog neural signals to digital, which of the following is a key advantage of oversampling?
Reduced need for anti‑aliasing filters
Increased power consumption
Higher storage requirements
Improved effective resolution through noise shaping
Explanation - Oversampling spreads quantization noise, allowing digital filtering to increase SNR.
Correct answer is: Improved effective resolution through noise shaping
Q.41 Which of the following is a common method for verifying the placement of a deep brain stimulation (DBS) electrode intraoperatively?
Optical coherence tomography
Microelectrode recording of neuronal activity
Ultrasound imaging
Thermal imaging
Explanation - Surgeons use microelectrode recordings to confirm characteristic neuronal firing patterns at target sites.
Correct answer is: Microelectrode recording of neuronal activity
Q.42 In the context of neural prosthetics, what does the term ‘closed‑loop’ refer to?
A system that records neural activity and delivers stimulation based on that activity
A device that only records but never stimulates
A hardware architecture with no feedback
A system that operates without power
Explanation - Closed‑loop prostheses adjust stimulation in real time using recorded neural signals.
Correct answer is: A system that records neural activity and delivers stimulation based on that activity
Q.43 What is the purpose of using a ‘bias‑tee’ in neural recording circuits?
To separate AC neural signals from DC bias currents
To increase the sampling rate
To provide power to the electrode
To convert digital signals back to analog
Explanation - A bias‑tee lets the DC bias pass to the electrode while routing the AC neural signal to the amplifier.
Correct answer is: To separate AC neural signals from DC bias currents
Q.44 Which phenomenon can cause a gradual drift in the baseline of a long‑duration extracellular recording?
Thermal noise
Electrode polarization and tissue encapsulation
Power‑line interference
Digital quantization error
Explanation - Slow changes in electrode impedance due to polarization or gliosis shift the baseline over time.
Correct answer is: Electrode polarization and tissue encapsulation
Q.45 A researcher wants to compare the timing of spikes across two neurons. Which metric is most appropriate?
Cross‑correlation histogram
Power spectral density
Root‑mean‑square amplitude
Mean firing rate
Explanation - Cross‑correlation reveals temporal relationships and synchrony between spike trains.
Correct answer is: Cross‑correlation histogram
Q.46 What is the main reason for using a low‑impedance amplifier in neural recording systems?
To increase the voltage of the signal
To reduce thermal noise contribution from the amplifier input
To limit the bandwidth
To simplify the PCB layout
Explanation - Lower input resistance generates less Johnson‑Nyquist noise, improving SNR.
Correct answer is: To reduce thermal noise contribution from the amplifier input
Q.47 Which of the following best describes a ‘bipolar montage’ in EEG?
A single electrode referenced to ground
Two adjacent electrodes whose signals are subtracted
All electrodes referenced to a common average
A reference electrode placed at the vertex
Explanation - Bipolar montage records the voltage difference between a pair of electrodes.
Correct answer is: Two adjacent electrodes whose signals are subtracted
Q.48 In signal processing, what does the term ‘aliasing’ refer to?
Noise introduced by the amplifier
Distortion caused by sampling a signal below its Nyquist rate
Loss of signal due to low gain
Phase shift introduced by filters
Explanation - Aliasing folds higher frequencies into lower ones when undersampled, corrupting the data.
Correct answer is: Distortion caused by sampling a signal below its Nyquist rate
Q.49 Which recording technique provides the highest spatial resolution for measuring neural activity?
Scalp EEG
Magnetoencephalography (MEG)
Intracortical microelectrode recording
Functional MRI
Explanation - Microelectrodes can isolate activity from individual neurons within tens of micrometers.
Correct answer is: Intracortical microelectrode recording
Q.50 What does the term ‘phase‑locking value’ (PLV) quantify in neural data analysis?
Amplitude of the signal
Consistency of phase relationship between two signals across trials
Total power in a frequency band
Mean firing rate
Explanation - PLV measures the stability of phase alignment, indicating functional connectivity.
Correct answer is: Consistency of phase relationship between two signals across trials
Q.51 During a neural recording, a sudden large voltage step appears in all channels simultaneously. What is the most likely cause?
Neuronal burst
Ground loop artifact
Electrode drift
Thermal noise
Explanation - Ground loops create common-mode voltage spikes that appear across all channels.
Correct answer is: Ground loop artifact
Q.52 Which type of filter has a linear phase response, preserving the waveform shape of neural spikes?
IIR Butterworth filter
FIR filter designed with the window method
Chebyshev Type I filter
Bessel filter
Explanation - FIR filters can be designed to have exact linear phase, preventing waveform distortion.
Correct answer is: FIR filter designed with the window method
Q.53 In a neural decoding algorithm, what is the role of a ‘training set’?
To test the algorithm’s performance
To provide labeled data for learning the mapping from neural signals to intended actions
To calibrate the hardware
To generate random noise
Explanation - The training set teaches the decoder how neural patterns correspond to specific outputs.
Correct answer is: To provide labeled data for learning the mapping from neural signals to intended actions
Q.54 Which phenomenon explains why the amplitude of extracellular spikes decreases with distance from the neuron?
Ohmic loss
Capacitive coupling
Volume conduction attenuation
Magnetic shielding
Explanation - Electrical fields spread through the conductive tissue, diminishing with distance.
Correct answer is: Volume conduction attenuation
Q.55 What is the main advantage of using a ‘common average reference’ (CAR) in EEG analysis?
It eliminates the need for a ground electrode
It reduces spatially widespread noise by subtracting the average of all channels
It increases the amplitude of all signals
It doubles the sampling rate
Explanation - CAR assumes that common noise appears similarly across electrodes and removes it by averaging.
Correct answer is: It reduces spatially widespread noise by subtracting the average of all channels
Q.56 Which of the following is a characteristic of the ‘burst firing’ pattern in neurons?
Regular, evenly spaced spikes
Groups of spikes with short inter‑spike intervals followed by quiescent periods
Single spikes only
Continuous high‑frequency firing without pauses
Explanation - Burst firing consists of rapid spike clusters separated by silent intervals.
Correct answer is: Groups of spikes with short inter‑spike intervals followed by quiescent periods
Q.57 When performing real‑time neural signal processing on an embedded platform, which factor is most critical?
Color of the device casing
Latency of the processing pipeline
Number of LEDs on the board
Length of the power cable
Explanation - Real‑time systems must deliver processed data within strict timing constraints.
Correct answer is: Latency of the processing pipeline
Q.58 What does the term ‘spike‑width’ refer to in extracellular recordings?
Duration of the action potential from peak to trough
Amplitude of the spike
Frequency of the spike train
Voltage offset of the baseline
Explanation - Spike width (half‑width) is measured between the peak and trough of the waveform.
Correct answer is: Duration of the action potential from peak to trough
Q.59 Which of the following best describes a ‘neuroprosthetic’ device?
A drug that enhances neural activity
A surgical tool for brain tumor removal
An implant that interfaces with the nervous system to restore lost function
A diagnostic imaging technique
Explanation - Neuroprostheses translate neural signals into control commands for assistive devices.
Correct answer is: An implant that interfaces with the nervous system to restore lost function
Q.60 What is the primary benefit of using a ‘silicon‑based microelectrode array’ over traditional wire electrodes?
Lower manufacturing cost
Higher mechanical flexibility
Precise geometry and high channel count for scalable recordings
No need for power supply
Explanation - Microfabrication enables dense, repeatable electrode layouts with many channels.
Correct answer is: Precise geometry and high channel count for scalable recordings
Q.61 Which statistical test is commonly used to compare mean firing rates between two experimental conditions?
Chi‑square test
Student's t‑test
Pearson correlation
Kruskal‑Wallis test
Explanation - The t‑test assesses whether two independent means differ significantly.
Correct answer is: Student's t‑test
Q.62 In the context of neural data compression, which technique preserves the most information while reducing data size?
Lossless Huffman coding
Lossy JPEG compression
Down‑sampling the signal to 100 Hz
Quantizing to 8‑bit resolution
Explanation - Lossless methods like Huffman coding reduce size without discarding any signal information.
Correct answer is: Lossless Huffman coding
Q.63 Which type of neural recording is best suited for studying slow cortical potentials (SCPs) lasting several seconds?
High‑pass filtered EMG
Low‑frequency EEG with a cutoff <0.5 Hz
Microelectrode intracellular recording
Spike‑sorted multi‑unit activity
Explanation - SCPs are captured by allowing very low frequencies to pass through the recording chain.
Correct answer is: Low‑frequency EEG with a cutoff <0.5 Hz
Q.64 What is the purpose of ‘artifact rejection’ in neural data preprocessing?
To increase the amplitude of spikes
To identify and remove non‑neural sources of signal contamination
To change the sampling rate
To convert analog signals to digital
Explanation - Artifact rejection cleans the dataset, ensuring analyses reflect true neural activity.
Correct answer is: To identify and remove non‑neural sources of signal contamination
Q.65 Which of the following best describes ‘current source density’ (CSD) analysis?
A method to estimate the location of current sources and sinks from extracellular potentials
A technique for amplifying neural signals
A type of electrode material
A statistical test for spike timing
Explanation - CSD computes the second spatial derivative of LFPs to infer local transmembrane currents.
Correct answer is: A method to estimate the location of current sources and sinks from extracellular potentials
Q.66 During a neural recording experiment, the researcher notices a 50 Hz sinusoidal interference that varies in amplitude over time. Which approach is most effective?
Apply a fixed notch filter at 50 Hz
Increase the sampling rate to 10 kHz
Use adaptive line enhancement (ALE) to track and cancel the interference
Reduce the gain of the amplifier
Explanation - ALE can follow amplitude changes of narrowband interference, providing dynamic suppression.
Correct answer is: Use adaptive line enhancement (ALE) to track and cancel the interference
Q.67 What is the typical bandwidth of a surface EMG signal used for muscle activation analysis?
0.1‑10 Hz
10‑100 Hz
20‑500 Hz
500‑2000 Hz
Explanation - Surface EMG contains most power between ~20 and 500 Hz.
Correct answer is: 20‑500 Hz
Q.68 Which of the following best explains why neural signals are often digitized using a ‘floating‑point’ representation instead of integer?
Floating‑point provides a larger dynamic range without sacrificing precision
Integers cannot represent negative voltages
Floating‑point reduces power consumption
Integers are incompatible with neural amplifiers
Explanation - Floating‑point numbers can represent very small and very large values accurately, useful for variable‑amplitude neural data.
Correct answer is: Floating‑point provides a larger dynamic range without sacrificing precision
Q.69 In a brain‑computer interface (BCI), what is the function of the ‘feature extraction’ stage?
Converting digital data back to analog
Identifying informative patterns (e.g., power in a frequency band) from raw neural signals
Amplifying the recorded signal
Providing power to the electrodes
Explanation - Feature extraction reduces dimensionality and highlights relevant neural characteristics for decoding.
Correct answer is: Identifying informative patterns (e.g., power in a frequency band) from raw neural signals
Q.70 Which metric quantifies the similarity between two spike waveforms for clustering purposes?
Euclidean distance
Pearson correlation coefficient
Signal‑to‑noise ratio
Mean firing rate
Explanation - Euclidean distance measures the straight‑line distance between waveform vectors in feature space.
Correct answer is: Euclidean distance
Q.71 Why is it important to keep the temperature of a neural recording system stable?
Temperature changes affect electrode impedance and can introduce drift
Higher temperature increases signal amplitude
Cold temperatures improve SNR
Temperature has no effect on recordings
Explanation - Thermal fluctuations modify resistance and can cause baseline shifts and noise.
Correct answer is: Temperature changes affect electrode impedance and can introduce drift
Q.72 Which of the following best describes the ‘Nyquist frequency’ for a system sampling at 20 kHz?
10 kHz
20 kHz
40 kHz
5 kHz
Explanation - Nyquist frequency is half the sampling rate, i.e., 20 kHz / 2 = 10 kHz.
Correct answer is: 10 kHz
Q.73 In a multi‑unit recording, what does the term ‘unit’ refer to?
A single electrode
A single spike waveform belonging to one neuron
A data packet
A power supply module
Explanation - A unit is the collection of spikes that are believed to come from the same neuron.
Correct answer is: A single spike waveform belonging to one neuron
Q.74 Which of the following is a typical method for visualizing high‑dimensional neural data after dimensionality reduction?
Scatter plot of the first two principal components
Bar graph of raw voltage values
Histogram of sampling rates
Pie chart of electrode types
Explanation - PCA reduces dimensions, and a 2‑D scatter plot of PC1 vs. PC2 shows clustering patterns.
Correct answer is: Scatter plot of the first two principal components
Q.75 What does the ‘inter‑spike interval’ (ISI) histogram reveal about neuronal firing?
Amplitude of spikes
Distribution of time gaps between consecutive spikes, indicating regularity or bursting
Frequency content of the signal
Electrode impedance
Explanation - ISI histograms help classify firing patterns such as regular, Poisson, or bursty.
Correct answer is: Distribution of time gaps between consecutive spikes, indicating regularity or bursting
Q.76 Which of the following is a primary limitation of using scalp EEG for precise source localization?
High spatial resolution
Signal attenuation and smearing due to the skull and scalp
Low susceptibility to motion artifacts
Ability to record single‑unit activity
Explanation - The conductive tissues blur the electric fields, reducing spatial accuracy.
Correct answer is: Signal attenuation and smearing due to the skull and scalp
Q.77 When designing a real‑time spike detection algorithm, why is a low latency essential?
To increase the power consumption
To ensure that the detected spikes can be used for timely feedback, e.g., in prosthetic control
To improve electrode durability
To reduce the number of electrodes needed
Explanation - Fast detection enables closed‑loop systems to respond within behaviorally relevant time frames.
Correct answer is: To ensure that the detected spikes can be used for timely feedback, e.g., in prosthetic control
Q.78 What is the primary cause of ‘capacitive coupling’ noise in neural recordings?
Direct electrical contact between electrodes
Magnetic fields generated by the brain
Electric fields induced by nearby high‑frequency circuits or cables
Thermal agitation of ions
Explanation - Capacitive coupling occurs when alternating fields induce unwanted currents in recording leads.
Correct answer is: Electric fields induced by nearby high‑frequency circuits or cables
Q.79 Which of the following best describes a ‘digital band‑pass filter’ implemented in software?
A hardware circuit that only passes a certain frequency range
An algorithm that removes frequencies outside a specified band from digitized data
A power supply regulator
A type of electrode coating
Explanation - Software filters process the stored digital signal to isolate desired frequency components.
Correct answer is: An algorithm that removes frequencies outside a specified band from digitized data
Q.80 In a neural recording chain, what is the function of an ‘anti‑aliasing filter’?
To increase the signal amplitude
To remove frequencies above the Nyquist limit before digitization
To convert digital data back to analog
To provide a reference voltage
Explanation - Anti‑aliasing filters prevent high‑frequency components from folding into the usable spectrum.
Correct answer is: To remove frequencies above the Nyquist limit before digitization
Q.81 Which metric is commonly used to assess the performance of a neural decoder?
Mean squared error (MSE) between predicted and actual kinematic trajectories
Number of electrodes used
Sampling rate of the system
Voltage range of the amplifier
Explanation - MSE quantifies how closely the decoder’s output matches the intended movement.
Correct answer is: Mean squared error (MSE) between predicted and actual kinematic trajectories
Q.82 What does the term ‘electrode impedance spectroscopy’ refer to?
Measuring the frequency‑dependent impedance of an electrode to assess its quality
Imaging the electrode with MRI
Counting the number of neurons around the electrode
Measuring the temperature of the electrode
Explanation - Impedance spectroscopy characterizes how an electrode behaves across frequencies, indicating stability and noise performance.
Correct answer is: Measuring the frequency‑dependent impedance of an electrode to assess its quality
Q.83 Why is the ‘ground‑shield‑ground’ (GSG) configuration often used in high‑frequency neural recording circuits?
To increase the gain
To reduce parasitic capacitance and improve signal integrity at high frequencies
To make the circuit smaller
To simplify software processing
Explanation - GSG minimizes stray inductance and capacitance, preserving high‑frequency neural signals.
Correct answer is: To reduce parasitic capacitance and improve signal integrity at high frequencies
Q.84 Which of the following best defines ‘burst suppression’ observed in EEG under deep anesthesia?
Continuous high‑frequency activity
Alternating periods of high‑amplitude bursts and flat suppression
Steady alpha rhythm
Rapid eye movement patterns
Explanation - Burst suppression is characteristic of profound cortical inhibition, showing bursts interleaved with quiescent intervals.
Correct answer is: Alternating periods of high‑amplitude bursts and flat suppression
Q.85 In a neural data acquisition system, why might one use a ‘pipeline ADC’ rather than a ‘SAR ADC’?
Pipeline ADCs provide higher sampling rates suitable for broadband neural signals
SAR ADCs are more power‑hungry
Pipeline ADCs have lower resolution
SAR ADCs cannot digitize analog signals
Explanation - Pipeline architectures support faster conversion speeds, essential for capturing high‑frequency spikes.
Correct answer is: Pipeline ADCs provide higher sampling rates suitable for broadband neural signals
Q.86 Which type of electrode is most appropriate for recording from the auditory nerve in a cochlear implant?
Surface electrode
Intracochlear electrode array
Depth electrode in the cortex
EEG scalp electrode
Explanation - Cochlear implants use an array placed inside the cochlea to stimulate auditory nerve fibers.
Correct answer is: Intracochlear electrode array
Q.87 What is the main advantage of using a ‘time‑division multiplexing’ (TDM) scheme in a multi‑channel neural recorder?
It reduces the number of physical wires needed to transmit many channels simultaneously
It increases the amplitude of each channel
It eliminates the need for amplification
It provides higher spatial resolution
Explanation - TDM interleaves samples from multiple channels onto a single transmission line, simplifying hardware.
Correct answer is: It reduces the number of physical wires needed to transmit many channels simultaneously
Q.88 During spike sorting, why is it important to perform ‘principal component analysis’ (PCA) on waveform snippets?
PCA removes noise completely
PCA reduces dimensionality while preserving the most variance, aiding clustering
PCA amplifies the spikes
PCA converts spikes into frequency domain
Explanation - PCA extracts the most informative features, simplifying subsequent clustering steps.
Correct answer is: PCA reduces dimensionality while preserving the most variance, aiding clustering
Q.89 Which of the following best describes the ‘Hamming window’ when used in spectral analysis of neural data?
A type of band‑pass filter
A weighting function that reduces spectral leakage in the FFT
A method for increasing sampling rate
A hardware component in amplifiers
Explanation - Applying a Hamming window before FFT smooths the edges of the data segment, minimizing leakage.
Correct answer is: A weighting function that reduces spectral leakage in the FFT
Q.90 What is the primary purpose of a ‘reference electrode’ placed in a non‑active tissue region during neural recordings?
To inject current into the brain
To serve as a stable voltage point against which active electrode potentials are measured
To increase the overall gain
To cool the recording site
Explanation - The reference provides a common baseline, allowing differential measurement of neural activity.
Correct answer is: To serve as a stable voltage point against which active electrode potentials are measured
Q.91 Which of the following analysis methods is best suited for detecting transient, event‑related changes in neural power across multiple frequency bands?
Continuous wavelet transform
Fast Fourier Transform (FFT)
Power spectral density (PSD) averaging over the entire recording
Auto‑correlation function
Explanation - Wavelet transform offers time‑frequency localization, ideal for transient event analysis.
Correct answer is: Continuous wavelet transform
Q.92 What does the term ‘electrocorticography’ (ECoG) refer to?
Recording from scalp electrodes
Recording from electrodes placed on the surface of the cerebral cortex
Intracellular recording from single neurons
Non‑invasive magnetic field measurement
Explanation - ECoG electrodes are placed directly on the dura or cortex, offering higher spatial resolution than EEG.
Correct answer is: Recording from electrodes placed on the surface of the cerebral cortex
Q.93 In a closed‑loop DBS system, which component detects the neural biomarker that triggers stimulation?
Stimulator coil
Sensing electrode with real‑time signal processing
Battery pack
External programmer
Explanation - The sensing electrode continuously monitors neural activity, and the processor decides when to deliver stimulation.
Correct answer is: Sensing electrode with real‑time signal processing
Q.94 Which of the following statements about ‘common‑mode rejection’ in differential amplifiers is true?
Higher CMRR improves suppression of noise that appears equally on both inputs
CMRR only affects DC signals
Low CMRR is desirable for neural recordings
CMRR is unrelated to electrode impedance
Explanation - A high CMRR means the amplifier efficiently rejects common‑mode interference, enhancing SNR.
Correct answer is: Higher CMRR improves suppression of noise that appears equally on both inputs
Q.95 What is the typical duration of a cortical slow wave (delta) observed during deep sleep?
0.5‑4 Hz (250‑2000 ms period)
4‑8 Hz (125‑250 ms period)
8‑13 Hz (77‑125 ms period)
13‑30 Hz (33‑77 ms period)
Explanation - Delta waves dominate deep sleep with frequencies below 4 Hz.
Correct answer is: 0.5‑4 Hz (250‑2000 ms period)
Q.96 When using a microelectrode for intracellular recording, why must the electrode be filled with a conductive solution such as potassium chloride (KCl)?
To provide a low‑impedance path for current flow into the cell
To increase the electrode’s weight
To generate magnetic fields
To act as a mechanical stabilizer
Explanation - The conductive solution establishes a stable electrical bridge between the electrode tip and the intracellular environment.
Correct answer is: To provide a low‑impedance path for current flow into the cell
Q.97 Which processing step is essential before applying a machine‑learning classifier to neural data?
Randomly shuffling the raw voltage traces
Normalization or scaling of extracted features
Increasing the sampling frequency to 1 MHz
Adding artificial noise
Explanation - Feature scaling ensures that all inputs contribute proportionally to the classifier’s decision boundary.
Correct answer is: Normalization or scaling of extracted features
Q.98 What is the primary advantage of using a ‘silicon‑on‑insulator’ (SOI) process for fabricating neural probes?
Higher flexibility compared to polymers
Reduced parasitic capacitance and improved isolation of recording sites
Lower cost than metal wires
Ability to emit light
Explanation - SOI technology provides a buried oxide layer that isolates conductive traces, lowering crosstalk.
Correct answer is: Reduced parasitic capacitance and improved isolation of recording sites
Q.99 Which of the following is a commonly used metric to assess the synchrony between two neural signals in the frequency domain?
Coherence
Mean squared error
Spike count
Latency jitter
Explanation - Coherence quantifies the linear correlation of two signals as a function of frequency.
Correct answer is: Coherence
Q.100 In a neural recording, why is it important to maintain a low‑impedance connection between the electrode and the amplifier input?
To increase the voltage of the signal
To minimize signal loss and thermal noise at the interface
To enable higher sampling rates
To reduce the physical size of the electrode
Explanation - Low‑impedance connections preserve signal amplitude and reduce Johnson noise.
Correct answer is: To minimize signal loss and thermal noise at the interface
Q.101 Which of the following is a standard method for estimating the firing rate of a neuron from spike times?
Kernel density estimation (e.g., Gaussian smoothing)
Fast Fourier Transform
Wavelet denoising
Principal component analysis
Explanation - Smoothing spike trains with a kernel yields a continuous estimate of instantaneous firing rate.
Correct answer is: Kernel density estimation (e.g., Gaussian smoothing)
Q.102 What does the term ‘burst index’ quantify in neural spike train analysis?
The ratio of burst spikes to total spikes
The amplitude of the spikes
The average inter‑spike interval
The power of the signal
Explanation - Burst index measures how much of a neuron's activity occurs in rapid clusters.
Correct answer is: The ratio of burst spikes to total spikes
Q.103 When a neural recording system uses a ‘shared‑ground’ topology, what is a potential drawback?
Increased risk of ground loops causing noise
Higher power consumption
Reduced number of channels
Improved signal amplitude
Explanation - Sharing a common ground across many channels can create loops that pick up interference.
Correct answer is: Increased risk of ground loops causing noise
Q.104 Which of the following is a key benefit of using ‘optogenetics’ combined with electrophysiology?
Non‑invasive recording of deep brain activity
Precise temporal control of specific neuron populations while measuring their electrical responses
Elimination of all recording artifacts
Automatic spike sorting without software
Explanation - Optogenetics enables activation or silencing of targeted cells, and electrophysiology records the resulting activity.
Correct answer is: Precise temporal control of specific neuron populations while measuring their electrical responses
Q.105 In the context of neural implants, what does the acronym ‘MEA’ stand for?
Microelectrode Array
Magneto‑Electrical Amplifier
Multi‑Electrode Analyzer
Motor‑Evoked Activity
Explanation - MEA refers to a grid of miniature electrodes used for simultaneous recordings from many sites.
Correct answer is: Microelectrode Array
Q.106 Why might a researcher choose to record neural signals in ‘bipolar’ mode rather than ‘monopolar’ mode?
Bipolar mode eliminates the need for a reference electrode
Bipolar mode reduces common‑mode interference and improves spatial selectivity
Monopolar mode cannot record spikes
Bipolar mode increases the sampling rate automatically
Explanation - By measuring the voltage difference between two nearby contacts, bipolar recording suppresses distant noise sources.
Correct answer is: Bipolar mode reduces common‑mode interference and improves spatial selectivity
Q.107 Which of the following best describes a ‘high‑density’ neural probe?
A probe with a small number of large electrodes
A probe containing hundreds to thousands of tightly spaced microelectrodes
A probe designed for cardiac recordings
A probe that only records local field potentials
Explanation - High‑density probes enable detailed mapping of neuronal activity across a large area.
Correct answer is: A probe containing hundreds to thousands of tightly spaced microelectrodes
Q.108 When performing spectral analysis of neural data, why is it important to use a sufficiently long data segment?
Longer segments improve frequency resolution of the FFT
Longer segments increase the amplitude of the signal
Longer segments reduce the need for filtering
Longer segments eliminate the need for a reference electrode
Explanation - Frequency resolution equals 1/(segment length), so longer windows provide finer spectral detail.
Correct answer is: Longer segments improve frequency resolution of the FFT
Q.109 What is the role of a ‘bias current source’ in a neural recording front‑end circuit?
To provide a DC offset that keeps the electrode‑tissue interface at a suitable polarization voltage
To amplify the recorded signal
To filter out high‑frequency noise
To digitize the analog signal
Explanation - A bias current maintains a stable electrode potential, improving recording stability.
Correct answer is: To provide a DC offset that keeps the electrode‑tissue interface at a suitable polarization voltage
Q.110 Which of the following is a primary reason for using ‘shielded cables’ in neural recording setups?
To increase the gain of the amplifier
To reduce electromagnetic interference (EMI) pickup from the environment
To lower the electrode impedance
To enable wireless transmission
Explanation - Shielding provides a conductive barrier that blocks external electric fields from contaminating the signal.
Correct answer is: To reduce electromagnetic interference (EMI) pickup from the environment
Q.111 In spike‑sorting, why is it common to discard spikes with amplitudes below a certain threshold?
Low‑amplitude spikes are likely noise rather than true neuronal events
They increase the firing rate artificially
They improve the resolution of the amplifier
They indicate electrode failure
Explanation - Thresholding eliminates events that do not rise above the noise floor, reducing false detections.
Correct answer is: Low‑amplitude spikes are likely noise rather than true neuronal events
Q.112 Which of the following best describes the purpose of ‘phase‑amplitude coupling’ analysis in neural data?
To assess whether the phase of a low‑frequency rhythm modulates the amplitude of a higher‑frequency oscillation
To measure the absolute power of a single frequency band
To calculate the firing rate of neurons
To filter out artifacts
Explanation - Phase‑amplitude coupling investigates cross‑frequency interactions that may underlie neural communication.
Correct answer is: To assess whether the phase of a low‑frequency rhythm modulates the amplitude of a higher‑frequency oscillation
Q.113 What is the typical voltage range of a scalp EEG signal?
10‑100 mV
1‑100 µV
0.1‑1 V
100‑500 mV
Explanation - EEG signals are low‑amplitude, generally between a few microvolts and tens of microvolts.
Correct answer is: 1‑100 µV
Q.114 Why is ‘baseline drift’ a concern in long‑duration neural recordings?
It reduces the sampling rate
It can obscure slow neural events and affect quantitative analysis
It increases the amplitude of spikes
It improves signal‑to‑noise ratio
Explanation - Drift shifts the zero level over time, making it difficult to interpret low‑frequency components.
Correct answer is: It can obscure slow neural events and affect quantitative analysis
Q.115 Which of the following is a standard technique for estimating the power spectral density (PSD) of neural recordings?
Welch's method
K‑means clustering
Kalman filtering
Linear regression
Explanation - Welch's method averages periodograms of overlapping segments to produce a smoother PSD estimate.
Correct answer is: Welch's method
Q.116 What does the term ‘single‑unit activity’ (SUA) refer to?
Aggregated activity from many neurons
Activity recorded from a single neuron, identifiable after spike sorting
The background noise level
Electrical activity from muscle tissue
Explanation - SUA represents spikes that can be reliably assigned to one neuron.
Correct answer is: Activity recorded from a single neuron, identifiable after spike sorting
Q.117 Which of the following best explains why neural recording amplifiers often have a high input‑referred noise specification?
To ensure that the amplifier itself does not dominate the overall noise floor
Because high noise is needed for better signal detection
To increase the sampling rate automatically
To match the impedance of the electrode
Explanation - Low input‑referred noise keeps the amplifier contribution below the intrinsic neural noise level.
Correct answer is: To ensure that the amplifier itself does not dominate the overall noise floor
Q.118 In a neural interface, what does the acronym ‘BCI’ stand for?
Brain‑Computer Interface
Bipolar Channel Input
Biological Circuit Integration
Baseline Correction Index
Explanation - BCI systems translate neural signals into commands for external devices.
Correct answer is: Brain‑Computer Interface
Q.119 Which type of noise dominates at high frequencies (>1 kHz) in neural recordings?
Thermal (Johnson) noise
Power‑line interference
Quantization noise from the ADC
Baseline drift
Explanation - At high frequencies, the limited resolution of the ADC becomes the main noise source.
Correct answer is: Quantization noise from the ADC
Q.120 When designing a neural data acquisition board, why is it important to separate analog and digital ground planes?
To reduce digital switching noise coupling into the sensitive analog front‑end
To increase the number of channels
To simplify software development
To enable wireless power transfer
Explanation - Separate ground planes prevent high‑frequency digital currents from contaminating analog measurements.
Correct answer is: To reduce digital switching noise coupling into the sensitive analog front‑end
Q.121 Which of the following is a typical characteristic of the ‘beta’ rhythm in motor cortex EEG?
8‑13 Hz, associated with relaxed wakefulness
13‑30 Hz, associated with motor planning and steady‑state movement
30‑80 Hz, linked to attention
0.5‑4 Hz, dominant during deep sleep
Explanation - Beta activity (13‑30 Hz) is prominent during motor tasks and decreases with movement initiation.
Correct answer is: 13‑30 Hz, associated with motor planning and steady‑state movement
Q.122 What is the primary purpose of ‘artifact subspace reconstruction’ (ASR) in neural data preprocessing?
To increase sampling rate
To automatically detect and suppress transient high‑amplitude artifacts while preserving neural activity
To convert analog signals to digital
To amplify low‑frequency components
Explanation - ASR identifies outlier subspaces and reconstructs them using a clean reference, reducing artifact impact.
Correct answer is: To automatically detect and suppress transient high‑amplitude artifacts while preserving neural activity
Q.123 Which of the following best describes the ‘Hodgkin‑Huxley model’?
A mathematical description of the ionic mechanisms underlying the generation of action potentials
A method for filtering neural signals
A type of electrode material
A statistical test for spike timing
Explanation - The Hodgkin‑Huxley equations model voltage‑gated ion channels and the dynamics of action potentials.
Correct answer is: A mathematical description of the ionic mechanisms underlying the generation of action potentials
Q.124 In a neural recording system, why might one employ a ‘dual‑stage amplification’ architecture?
To first provide a low‑noise preamplifier close to the electrode and then a higher‑gain stage farther away
To double the sampling rate
To enable wireless transmission
To reduce the need for shielding
Explanation - A front‑end preamp minimizes noise at the source, while a second stage provides the required overall gain.
Correct answer is: To first provide a low‑noise preamplifier close to the electrode and then a higher‑gain stage farther away
Q.125 Which of the following is an advantage of using ‘wireless telemetry’ for chronic neural recordings in freely moving animals?
Eliminates the need for any power source
Removes tether‑related movement constraints and reduces mechanical stress on the implant
Guarantees zero data loss
Provides unlimited bandwidth
Explanation - Wireless systems allow natural behavior without cables that could interfere with the animal’s movements.
Correct answer is: Removes tether‑related movement constraints and reduces mechanical stress on the implant
Q.126 What does the term ‘spike latency jitter’ refer to?
Variability in the time interval between stimulus onset and the first spike across trials
The average firing rate of a neuron
Amplitude of the spike
Frequency content of the spike
Explanation - Latency jitter quantifies the trial‑to‑trial timing variability of evoked spikes.
Correct answer is: Variability in the time interval between stimulus onset and the first spike across trials
Q.127 Which of the following is a reason to use a ‘reference electrode’ placed in cerebrospinal fluid (CSF) rather than in scalp tissue for intracortical recordings?
CSF provides a more stable electrical reference with lower impedance
CSF increases the amplitude of spikes
Scalp tissue is more conductive
CSF eliminates the need for amplification
Explanation - CSF offers a consistent, low‑impedance environment, improving reference stability for deep recordings.
Correct answer is: CSF provides a more stable electrical reference with lower impedance