Q.1 Which type of electrode is most commonly used for chronic recording of neuronal activity in the human brain?
Surface (ECoG) electrode
Microelectrode array (MEA)
Silicon nanowire electrode
Suction electrode
Explanation - Microelectrode arrays provide high spatial resolution and can be implanted for long‑term recordings, making them the standard for chronic neural interfacing.
Correct answer is: Microelectrode array (MEA)
Q.2 What is the primary purpose of a charge‑balanced biphasic stimulation pulse in neural prostheses?
To increase stimulation amplitude
To reduce electrode corrosion
To minimize tissue damage
To improve signal bandwidth
Explanation - Charge‑balanced biphasic pulses ensure that net injected charge is zero, which reduces electrochemical reactions at the electrode-tissue interface and prevents tissue injury.
Correct answer is: To minimize tissue damage
Q.3 Which material is most widely used for the substrate of flexible neural interface devices because of its biocompatibility and low Young's modulus?
Silicon
Polyimide
Gallium arsenide
Aluminum oxide
Explanation - Polyimide offers flexibility, good mechanical strength, and biocompatibility, making it ideal for conformable neural interfaces.
Correct answer is: Polyimide
Q.4 In a closed‑loop deep brain stimulation (DBS) system, what is the typical feedback signal used to adjust stimulation parameters?
Blood oxygen level
Local field potentials (LFPs)
Heart rate variability
Skin temperature
Explanation - LFPs reflect the summed activity of neuronal populations near the electrode and are commonly used as feedback for adaptive DBS.
Correct answer is: Local field potentials (LFPs)
Q.5 Which of the following is a major advantage of using optogenetic stimulation over electrical stimulation in neural interfacing?
Higher spatial resolution
Lower power consumption
Simpler surgical implantation
No need for genetic modification
Explanation - Optogenetics allows activation of specific neuron types with light, offering millisecond timing and cellular‑level spatial precision that electrical stimulation cannot achieve.
Correct answer is: Higher spatial resolution
Q.6 What does the term "electrode impedance" primarily describe in the context of neural recordings?
The resistance to ion flow at the electrode‑tissue interface
The voltage required to trigger an action potential
The capacitance of the recording cable
The inductance of the lead wire
Explanation - Electrode impedance reflects the combined resistive and capacitive properties of the electrode surface and surrounding tissue, influencing signal quality.
Correct answer is: The resistance to ion flow at the electrode‑tissue interface
Q.7 Which signal processing technique is most effective for removing power‑line noise (50/60 Hz) from neural recordings?
Fast Fourier Transform (FFT)
Notch filtering
Wavelet denoising
Principal component analysis
Explanation - A notch filter attenuates a narrow band of frequencies, efficiently suppressing the fixed 50/60 Hz interference without affecting surrounding neural signals.
Correct answer is: Notch filtering
Q.8 In a brain‑computer interface (BCI) that decodes motor intent from the motor cortex, which feature is commonly extracted from the recorded spikes?
Spike amplitude histogram
Mean firing rate
Spike width distribution
Inter‑spike interval variance
Explanation - Mean firing rate provides a robust, time‑averaged measure of neuronal activity that correlates well with intended movement and is widely used for decoding.
Correct answer is: Mean firing rate
Q.9 What is the main safety concern when delivering high‑frequency stimulation (>1 kHz) through implanted neural electrodes?
Thermal heating of tissue
Electrolytic corrosion of the electrode
Generation of magnetic fields
Increased synaptic plasticity
Explanation - High‑frequency currents can cause Joule heating, potentially damaging surrounding neural tissue if not properly controlled.
Correct answer is: Thermal heating of tissue
Q.10 Which classification algorithm is frequently used for real‑time decoding of EEG signals in non‑invasive BCIs?
Support Vector Machine (SVM)
K‑means clustering
Gaussian mixture model
Hidden Markov Model (HMM)
Explanation - SVMs handle high‑dimensional EEG feature spaces well and provide good generalization for binary or multi‑class motor imagery tasks.
Correct answer is: Support Vector Machine (SVM)
Q.11 Which of the following best describes a ‘neurotrophic factor’ used in neural prostheses?
A molecule that conducts electricity
A protein that promotes neuron survival and growth
A synthetic polymer for electrode coating
A type of magnetic field generator
Explanation - Neurotrophic factors (e.g., BDNF, NGF) are biological agents that support neuronal health and are sometimes incorporated into implants to improve chronic performance.
Correct answer is: A protein that promotes neuron survival and growth
Q.12 What is the primary function of a 'reference electrode' in a neural recording system?
To deliver stimulation pulses
To provide a stable ground potential
To amplify the neural signal
To filter out high‑frequency noise
Explanation - The reference electrode establishes a common electrical baseline, allowing differential measurement of neural activity relative to a known potential.
Correct answer is: To provide a stable ground potential
Q.13 Which of the following is a key advantage of using wireless telemetry for neural implants?
Unlimited power supply
Elimination of infection risk from percutaneous leads
Higher data transmission rates than wired links
Simpler signal processing algorithms
Explanation - Wireless telemetry removes the need for transcutaneous cables, reducing the chance of infection at the skin–device interface.
Correct answer is: Elimination of infection risk from percutaneous leads
Q.14 In the context of neural prosthetic design, what does the term "bio‑fouling" refer to?
Accumulation of scar tissue around the electrode
Loss of battery life due to high current draw
Cross‑talk between adjacent channels
Electrical shorting caused by moisture
Explanation - Bio‑fouling describes the body’s reaction (glial scarring, protein adsorption) that degrades electrode performance over time.
Correct answer is: Accumulation of scar tissue around the electrode
Q.15 Which parameter is most critical when designing the geometry of a penetrating microelectrode to minimize tissue damage?
Electrode tip radius
Copper trace thickness
Lead wire length
Connector pin spacing
Explanation - A smaller tip radius reduces insertion force and limits disruption of neural tissue, lowering chronic inflammatory response.
Correct answer is: Electrode tip radius
Q.16 What does the Shannon equation predict for neural stimulation safety?
Maximum charge per phase based on pulse width
Optimal electrode spacing for recording
Minimum voltage required for action potential generation
Relationship between temperature and impedance
Explanation - The Shannon equation (Q = k·W^0.5) relates charge density to pulse width, providing a safety limit to avoid tissue damage.
Correct answer is: Maximum charge per phase based on pulse width
Q.17 Which type of neural signal is most suitable for decoding speech intentions in a cortical implant?
Local field potentials (LFPs)
Single‑unit spikes
Electromyographic (EMG) activity
Electrooculogram (EOG) signals
Explanation - LFPs capture the synchronized activity of neuronal ensembles involved in higher‑order functions like speech planning, offering stable decoding over longer periods.
Correct answer is: Local field potentials (LFPs)
Q.18 Which of the following is NOT a commonly used method for reducing motion artifacts in wearable neural sensors?
Mechanical isolation of the sensor
Adaptive filtering algorithms
Increasing stimulus amplitude
Using stretchable substrate materials
Explanation - Higher stimulus amplitude does not mitigate motion artifacts; instead, mechanical design and signal processing techniques are employed.
Correct answer is: Increasing stimulus amplitude
Q.19 What is the purpose of coating neural electrodes with iridium oxide (IrOx)?
To increase mechanical rigidity
To improve charge injection capacity
To make the electrode transparent
To reduce manufacturing cost
Explanation - Iridium oxide provides a high reversible charge storage capability, allowing safe stimulation at lower voltages.
Correct answer is: To improve charge injection capacity
Q.20 Which neural interface technology is most appropriate for recording from peripheral nerves with minimal invasiveness?
Intraneural Utah array
Cuff electrode
Penetrating silicon probe
Surface EEG cap
Explanation - Cuff electrodes wrap around the nerve, providing chronic access without penetrating the epineurium, thus reducing tissue damage.
Correct answer is: Cuff electrode
Q.21 In the context of neural prosthetics, what does the term "closed‑loop" mean?
Device operates without any external power source
Stimulation parameters are automatically adjusted based on recorded feedback
System uses only pre‑programmed stimulation patterns
All signals are transmitted wirelessly
Explanation - Closed‑loop systems sense neural activity, process it, and modify stimulation in real time to achieve desired outcomes.
Correct answer is: Stimulation parameters are automatically adjusted based on recorded feedback
Q.22 Which metric is commonly used to assess the quality of a neural recording channel?
Signal‑to‑noise ratio (SNR)
Battery voltage
Connector pin count
Cable length
Explanation - SNR quantifies how well the neural signal stands out above background noise, directly reflecting recording quality.
Correct answer is: Signal‑to‑noise ratio (SNR)
Q.23 What is the main advantage of using a high‑density micro‑LED array for optogenetic stimulation in cortical implants?
It eliminates the need for genetic modification
Provides sub‑millisecond temporal resolution
Enables simultaneous stimulation of thousands of neurons with spatial precision
Reduces power consumption compared to electrical stimulation
Explanation - High‑density micro‑LEDs can address many distinct sites, delivering light to specific neuronal populations with fine spatial control.
Correct answer is: Enables simultaneous stimulation of thousands of neurons with spatial precision
Q.24 Which phenomenon describes the gradual loss of recording amplitude over weeks after electrode implantation?
Electrochemical drift
Glial scarring
Capacitive coupling loss
Thermal diffusion
Explanation - Reactive astrocytes and microglia form a dense scar around the electrode, increasing impedance and attenuating recorded signals.
Correct answer is: Glial scarring
Q.25 For a neural implant that uses inductive coupling for power transfer, which parameter primarily determines the efficiency of power delivery?
Frequency of the carrier signal
Length of the lead wires
Number of recording channels
Size of the data logger
Explanation - Higher frequencies improve coupling efficiency up to a limit, but also increase tissue heating; thus, selecting an optimal frequency is crucial.
Correct answer is: Frequency of the carrier signal
Q.26 Which computational model is frequently used to simulate the electrical behavior of a neuron during extracellular stimulation?
Hodgkin–Huxley model
Kalman filter
Monte Carlo simulation
Fourier series expansion
Explanation - The Hodgkin–Huxley framework describes ion channel dynamics and can predict how external electric fields affect membrane potentials.
Correct answer is: Hodgkin–Huxley model
Q.27 What is the function of a 'current source' in a neural stimulation circuit?
To maintain a constant voltage across the electrode
To provide a fixed charge per phase regardless of tissue impedance
To amplify incoming neural signals
To filter out high‑frequency noise
Explanation - A current source ensures that the same amount of charge is delivered even if the impedance varies, improving safety and repeatability.
Correct answer is: To provide a fixed charge per phase regardless of tissue impedance
Q.28 Which regulatory body in the United States is responsible for approving neural prosthetic devices for clinical use?
Food and Drug Administration (FDA)
National Institutes of Health (NIH)
Center for Disease Control (CDC)
American Medical Association (AMA)
Explanation - The FDA evaluates safety and efficacy of medical devices, including neural prostheses, before they can be marketed.
Correct answer is: Food and Drug Administration (FDA)
Q.29 Which method is used to calibrate the amplitude of an implanted neural stimulator after surgery?
Visual inspection of the device
Threshold testing using patient feedback
Measuring battery voltage
Analyzing electrode temperature
Explanation - Clinicians gradually increase stimulation until the patient reports a perceptible but comfortable sensation, establishing safe operating limits.
Correct answer is: Threshold testing using patient feedback
Q.30 What is the primary reason for using differential amplification in neural recording circuits?
To increase the overall gain of the system
To reject common‑mode noise and improve signal quality
To convert AC signals to DC
To reduce power consumption
Explanation - Differential amplifiers subtract signals from two inputs, canceling noise common to both lines (e.g., motion artifacts) while preserving the neural signal.
Correct answer is: To reject common‑mode noise and improve signal quality
Q.31 In a neural interface, which term describes the delay between the onset of a stimulus and the recorded neural response?
Latency
Amplitude
Bandwidth
Phase shift
Explanation - Latency measures the time interval between stimulus delivery and the observed neural activity, critical for timing‑sensitive applications.
Correct answer is: Latency
Q.32 Which of the following is a typical symptom of electrode‑induced inflammation in brain tissue?
Increased signal amplitude
Decreased impedance
Glial scar formation
Reduced battery life
Explanation - Inflammatory response leads to astrocytic and microglial activation, resulting in a dense glial scar around the implant.
Correct answer is: Glial scar formation
Q.33 What does the term "bandpass filter" refer to in the context of neural signal processing?
A filter that allows only a specific range of frequencies to pass through
A filter that completely blocks all frequencies
A device that amplifies the signal
A method for digitizing analog signals
Explanation - Bandpass filters are used to isolate neural activity (e.g., 300–3000 Hz for spikes) while removing low‑frequency drift and high‑frequency noise.
Correct answer is: A filter that allows only a specific range of frequencies to pass through
Q.34 Which of the following is an advantage of using a flexible printed circuit board (FPCB) in neural implants?
Higher thermal conductivity
Better conformity to brain surface
Increased electrode size
Simpler soldering process
Explanation - FPCBs can bend to match the curvature of neural tissue, reducing mechanical mismatch and chronic injury.
Correct answer is: Better conformity to brain surface
Q.35 When designing a neural implant for the spinal cord, why is it important to consider the cerebrospinal fluid (CSF) layer?
CSF provides nutrients to the electrodes
CSF acts as an electrical insulator affecting stimulation thresholds
CSF changes the device's mechanical stiffness
CSF eliminates the need for a power source
Explanation - CSF has high conductivity and can shunt current, requiring higher voltages or specific electrode designs to achieve effective stimulation.
Correct answer is: CSF acts as an electrical insulator affecting stimulation thresholds
Q.36 What is the main function of a 'stimulus artifact rejection' algorithm in a closed‑loop neural device?
To increase the amplitude of the stimulus
To remove the stimulation‑induced waveform from recorded data
To amplify the neural response
To adjust battery usage
Explanation - Stimulus artifacts can obscure the underlying neural signal; rejection algorithms isolate and subtract the artifact for accurate feedback.
Correct answer is: To remove the stimulation‑induced waveform from recorded data
Q.37 Which of the following is a common approach to achieve bi-directional communication in a neural prosthetic system?
Separate wires for input and output
Time‑division multiplexing of stimulation and recording
Using a single electrode for both functions
Operating at optical frequencies
Explanation - By alternating short intervals of stimulation and recording, the same hardware can perform both functions without interference.
Correct answer is: Time‑division multiplexing of stimulation and recording
Q.38 Which characteristic of a neural recording channel determines its ability to capture rapid action potentials?
Sampling rate
Battery voltage
Connector size
Cable color
Explanation - A higher sampling rate provides finer temporal resolution, essential for accurately representing fast spikes.
Correct answer is: Sampling rate
Q.39 In the context of neural interfacing, what does the term "chronaxie" refer to?
The minimum current needed for stimulation
The time constant of neuronal membrane recovery
The pulse width at which twice the rheobase current is needed
The latency between stimulus and response
Explanation - Chronaxie is a measure of neuronal excitability, indicating the stimulus duration required for effective activation.
Correct answer is: The pulse width at which twice the rheobase current is needed
Q.40 What is the primary advantage of using a 'soft' neural probe made of polymeric materials over a traditional silicon probe?
Higher electrical conductivity
Reduced mechanical mismatch with brain tissue
Lower production cost
Greater thermal resistance
Explanation - Soft polymers better match the modulus of neural tissue, decreasing chronic inflammation and improving long‑term recording stability.
Correct answer is: Reduced mechanical mismatch with brain tissue
Q.41 Which type of neural data is most commonly used for controlling a robotic prosthetic hand in a motor cortex BCI?
Electrocorticography (ECoG) signals
Functional MRI (fMRI) images
Local field potentials (LFPs)
Single‑unit spike rates
Explanation - Spike rates provide high‑resolution, rapid information about intended finger movements, enabling fine motor control of prosthetic hands.
Correct answer is: Single‑unit spike rates
Q.42 What does the term "electrochemical window" define for an implanted electrode material?
The range of voltages where the material remains stable without water electrolysis
The maximum current the electrode can deliver
The bandwidth of recorded neural signals
The physical size limits of the electrode
Explanation - Operating within the electrochemical window prevents harmful reactions like gas formation or electrode degradation.
Correct answer is: The range of voltages where the material remains stable without water electrolysis
Q.43 Which of the following best describes a 'neuroprosthetic' device?
A drug delivery system for the brain
An implant that replaces or augments lost neural function
A diagnostic imaging tool
A wireless router for neural data
Explanation - Neuroprostheses are engineered to restore sensory, motor, or cognitive abilities by interfacing directly with neural tissue.
Correct answer is: An implant that replaces or augments lost neural function
Q.44 In neural signal acquisition, what is the effect of increasing the analog‑to‑digital converter (ADC) bit depth from 12‑bit to 24‑bit?
Higher sampling frequency
Reduced quantization noise and higher resolution
Lower power consumption
Decreased data storage requirements
Explanation - More bits allow finer voltage steps, improving the fidelity of digitized neural signals.
Correct answer is: Reduced quantization noise and higher resolution
Q.45 Which physiological phenomenon can cause a gradual increase in electrode impedance over weeks after implantation?
Electrode corrosion
Glial encapsulation
Temperature rise
Battery depletion
Explanation - Reactive glial cells form a dense layer around the electrode, increasing the overall impedance and reducing signal quality.
Correct answer is: Glial encapsulation
Q.46 What is the role of a 'ground plane' in the PCB design of a neural recording system?
To provide a reference for analog signals and reduce EMI
To increase the size of the device
To store charge for stimulation
To act as a battery
Explanation - A solid ground plane minimizes electromagnetic interference and provides a stable reference for differential measurements.
Correct answer is: To provide a reference for analog signals and reduce EMI
Q.47 Which stimulation waveform is most commonly used to activate peripheral nerves while minimizing charge buildup?
Monophasic rectangular pulse
Biphasic symmetric pulse
Sinusoidal wave
Triangular pulse
Explanation - A symmetric biphasic pulse balances positive and negative phases, preventing net charge accumulation at the electrode–tissue interface.
Correct answer is: Biphasic symmetric pulse
Q.48 Which parameter is critical when selecting a wireless frequency band for transmitting neural data from an implanted device?
Band‑gap voltage of the transceiver
Regulatory limits on specific absorption rate (SAR)
Color of the implant housing
Number of electrodes
Explanation - SAR limits ensure that radiofrequency energy does not cause unsafe tissue heating, dictating allowable transmission power and frequencies.
Correct answer is: Regulatory limits on specific absorption rate (SAR)
Q.49 What is the main purpose of using a 'shielded cable' in neural recording setups?
To increase signal amplitude
To prevent electromagnetic interference from external sources
To reduce battery consumption
To make the cable more flexible
Explanation - Shielding blocks external electric fields, preserving the integrity of low‑amplitude neural signals.
Correct answer is: To prevent electromagnetic interference from external sources
Q.50 Which computational approach is frequently used to decode intended speech from cortical neural activity?
Hidden Markov Models (HMM)
Finite Element Analysis (FEA)
Particle Swarm Optimization (PSO)
Linear Discriminant Analysis (LDA)
Explanation - HMMs model temporal sequences and have been effective in translating neural firing patterns into phoneme or word predictions.
Correct answer is: Hidden Markov Models (HMM)
Q.51 Which of the following best describes the concept of 'neuroplasticity' relevant to neural prosthetic training?
The ability of neural tissue to conduct electricity
Changes in synaptic strength and circuitry in response to experience
The degradation of electrodes over time
The process of generating action potentials
Explanation - Neuroplasticity enables the brain to adapt to the artificial inputs from a prosthetic, improving functional outcomes with training.
Correct answer is: Changes in synaptic strength and circuitry in response to experience
Q.52 Why is the 'Nyquist theorem' important for designing the sampling rate of a neural data acquisition system?
It dictates the maximum voltage a sensor can handle
It ensures the sampling rate is at least twice the highest frequency of interest to avoid aliasing
It defines the power consumption limits of the device
It determines the size of the electrode array
Explanation - Nyquist sampling prevents high‑frequency components from being misrepresented as lower frequencies in the digitized signal.
Correct answer is: It ensures the sampling rate is at least twice the highest frequency of interest to avoid aliasing
Q.53 Which safety standard specifically addresses the maximum allowable charge density for neural stimulation electrodes?
ISO 13485
IEC 60601-1
IEEE 802.15.4
ASTM F1840
Explanation - IEC 60601-1 includes limits on charge density to ensure safe electrical stimulation of neural tissue.
Correct answer is: IEC 60601-1
Q.54 In a neural recording system, what is the purpose of a 'common‑mode rejection ratio' (CMRR)?
To increase the voltage gain
To quantify the ability to reject noise common to both inputs
To measure battery life
To determine electrode size
Explanation - High CMRR indicates effective suppression of interference that appears equally on both leads, preserving the differential neural signal.
Correct answer is: To quantify the ability to reject noise common to both inputs
Q.55 Which of the following describes the main function of a 'feedback controller' in a closed‑loop neural stimulation device?
To store recorded neural data
To adjust stimulation intensity based on real‑time neural activity
To power the implant via solar cells
To encrypt transmitted data
Explanation - The feedback controller processes the sensed signal and modulates stimulation parameters to achieve desired therapeutic outcomes.
Correct answer is: To adjust stimulation intensity based on real‑time neural activity
Q.56 What is the primary advantage of using a 'silicon carbide' (SiC) coating on neural electrodes?
Increased optical transparency
Enhanced biocompatibility and chemical stability
Reduced electrical resistance to zero
Ability to emit light
Explanation - SiC forms a hard, inert layer that protects the underlying metal from corrosion and reduces tissue reaction.
Correct answer is: Enhanced biocompatibility and chemical stability
Q.57 Which term refers to the process of converting neural action potentials into a digital code for external processing?
Spike sorting
Signal averaging
Frequency modulation
Amplitude clipping
Explanation - Spike sorting identifies and classifies individual neuronal spikes from multi‑unit recordings, creating discrete digital events.
Correct answer is: Spike sorting
Q.58 During chronic implantation, which factor most influences the long‑term stability of the electrode–tissue interface?
Electrode thickness
Mechanical flexibility of the probe
Color of the connector
Operating system of the external controller
Explanation - Flexibility reduces micromotion relative to brain tissue, limiting chronic inflammation and preserving signal quality.
Correct answer is: Mechanical flexibility of the probe
Q.59 What is the main purpose of using a 'Faraday cage' during in‑vitro neural electrode testing?
To keep the electrodes warm
To shield the setup from external electromagnetic interference
To increase the voltage applied to the electrodes
To store data securely
Explanation - A Faraday cage blocks external electric fields, ensuring that measured signals reflect only the intended test conditions.
Correct answer is: To shield the setup from external electromagnetic interference
Q.60 Which type of neural interface is typically used for high‑resolution mapping of sensory cortex activity in animal studies?
Utah microelectrode array
Surface EEG cap
Intracochlear electrode
Peripheral nerve cuff
Explanation - The Utah array provides dense, penetrating contacts suitable for capturing fine-grained cortical activity.
Correct answer is: Utah microelectrode array
Q.61 In the context of neural implants, what does 'encapsulation' refer to?
The process of coating the device with a biocompatible polymer
Embedding the device in a metal case for protection
Connecting the implant to an external computer
Generating action potentials
Explanation - Encapsulation provides a barrier against bodily fluids and improves biocompatibility, extending device lifespan.
Correct answer is: The process of coating the device with a biocompatible polymer
Q.62 Which parameter is most directly affected by increasing the 'sampling depth' (i.e., number of bits) of an ADC in neural recordings?
Dynamic range
Signal latency
Wireless transmission range
Power consumption of the battery
Explanation - More bits increase the range between the smallest and largest representable voltages, enhancing signal fidelity.
Correct answer is: Dynamic range
Q.63 What is a primary benefit of using a 'dual‑supply' architecture (positive and negative rails) in neural signal amplifiers?
Allows amplification of both positive and negative neural potentials without bias
Reduces the size of the device
Increases battery life
Simplifies the PCB layout
Explanation - Dual‑supply amplifiers can handle bipolar signals centered around zero volts, improving linearity and reducing distortion.
Correct answer is: Allows amplification of both positive and negative neural potentials without bias
Q.64 Which of the following is a typical symptom that may indicate a failure of a neural prosthetic's power source?
Sudden loss of recorded signals
Increased signal amplitude
Improved battery indicator
Reduced electrode size
Explanation - Power depletion can cause the device to stop acquiring or transmitting data, leading to abrupt signal loss.
Correct answer is: Sudden loss of recorded signals
Q.65 What does the term 'neuronal recruitment' describe in the context of electrical stimulation?
The process of generating new neurons
Activation of additional neurons as stimulus intensity increases
Removal of dead neurons
Measurement of blood flow in the brain
Explanation - Higher current or voltage recruits more axons and cell bodies, broadening the area of activation.
Correct answer is: Activation of additional neurons as stimulus intensity increases
Q.66 Which technology is used to fabricate high‑density electrode arrays with feature sizes below 10 µm?
3‑D printing
Photolithography
Molding
Laser cutting
Explanation - Photolithographic processes enable sub‑micron patterning essential for dense microelectrode arrays.
Correct answer is: Photolithography
Q.67 In a neural interface, what is the function of a 'bias‑tee'?
To separate AC (signal) and DC (stimulation) components on a single line
To amplify the signal
To store energy for later use
To convert digital data to analog
Explanation - A bias‑tee allows simultaneous delivery of stimulation current (DC) and recording of neural signals (AC) over the same electrode.
Correct answer is: To separate AC (signal) and DC (stimulation) components on a single line
Q.68 Which physiological measurement is commonly used to assess the effectiveness of a cochlear implant?
Auditory brainstem response (ABR)
Electrocardiogram (ECG)
Blood glucose level
Pupil dilation
Explanation - ABR evaluates the neural activity of the auditory pathway in response to acoustic stimulation, indicating implant performance.
Correct answer is: Auditory brainstem response (ABR)
Q.69 What does the term "artifact" refer to in neural recordings?
A true neuronal spike
Unwanted signal from external sources or stimulation
A type of electrode
The battery indicator
Explanation - Artifacts are non‑neural signals that can obscure or mimic genuine neural activity and must be removed during analysis.
Correct answer is: Unwanted signal from external sources or stimulation
Q.70 Which of the following best describes a 'brain‑machine interface' (BMI)?
A system that records brain activity and translates it into commands for external devices
A type of MRI scanner
A surgical instrument for brain biopsies
A pharmaceutical drug that enhances cognition
Explanation - BMIs decode neural signals to control computers, prosthetic limbs, or other external hardware.
Correct answer is: A system that records brain activity and translates it into commands for external devices
Q.71 In neural stimulation, what does the term "rheobase" refer to?
The minimum current needed for an infinitely long pulse to elicit an action potential
The maximum voltage a device can output
The duration of a stimulus pulse
The frequency of the stimulation
Explanation - Rheobase is a fundamental excitability parameter defining the lowest current that can trigger a response with a very long stimulus.
Correct answer is: The minimum current needed for an infinitely long pulse to elicit an action potential
Q.72 Which feature of a neural prosthetic system helps to conserve energy during periods of inactivity?
Continuous high‑frequency stimulation
Dynamic power‑down or sleep mode
Increasing sampling rate
Adding more electrodes
Explanation - Sleep modes reduce power draw when the device is idle, extending battery life.
Correct answer is: Dynamic power‑down or sleep mode
Q.73 What is a typical consequence of using a stimulation pulse width that is too short (< 20 µs) for a given neural target?
Insufficient charge delivery leading to ineffective stimulation
Excessive heating of tissue
Rapid battery depletion
Increased signal-to-noise ratio
Explanation - Short pulses may not deliver enough charge to reach the activation threshold of the target neurons.
Correct answer is: Insufficient charge delivery leading to ineffective stimulation
Q.74 Which type of data compression is most appropriate for reducing bandwidth of recorded neural spikes before wireless transmission?
Lossless Huffman coding
JPEG image compression
MP3 audio compression
Run‑length encoding of spike timestamps
Explanation - Spike timestamps are sparse; run‑length encoding efficiently represents intervals between spikes without loss of information.
Correct answer is: Run‑length encoding of spike timestamps
Q.75 Which characteristic of an electrode influences its selectivity for recording from a specific neuronal population?
Electrode diameter
Cable color
Connector type
Battery voltage
Explanation - Smaller diameters sample a more confined volume of tissue, improving selectivity for nearby neurons.
Correct answer is: Electrode diameter
Q.76 What is the main purpose of using a 'grounded Faraday shield' around the analog front‑end of a neural recording circuit?
To increase the gain of the amplifier
To protect the circuit from static discharge
To block external electromagnetic fields and reduce noise
To cool the device
Explanation - A grounded shield acts as a barrier to EMI, preserving the low‑amplitude neural signals.
Correct answer is: To block external electromagnetic fields and reduce noise
Q.77 Which of the following is a common metric used to assess the performance of a neural decoder?
Mean squared error (MSE)
Battery discharge rate
Connector pin count
Device weight
Explanation - MSE quantifies the difference between predicted and actual movement trajectories, indicating decoding accuracy.
Correct answer is: Mean squared error (MSE)
Q.78 In the context of neural implants, what does the acronym "MEG" stand for?
Microelectrode Grid
Magnetoencephalography
Motor Evoked Gradient
Maximum Energy Gain
Explanation - MEG measures magnetic fields generated by neuronal currents and is a non‑invasive technique complementary to EEG.
Correct answer is: Magnetoencephalography
Q.79 Which factor most directly influences the 'charge injection capacity' of an electrode material?
Surface roughness and electrochemical properties
Length of the connecting wire
Color of the electrode
Operating system of the controller
Explanation - Rougher surfaces increase effective area, allowing more charge to be transferred safely during stimulation.
Correct answer is: Surface roughness and electrochemical properties
Q.80 What is a key advantage of using a 'high‑impedance' recording electrode in neural sensing?
Allows larger currents to pass
Improves selectivity to nearby neuronal sources
Reduces power consumption
Increases the physical size of the electrode
Explanation - High impedance limits the recording volume, making the electrode more sensitive to local activity and reducing distant noise.
Correct answer is: Improves selectivity to nearby neuronal sources
Q.81 Which of the following describes a primary challenge when integrating a neural interface with a smartphone for data display?
Ensuring compatible screen resolution
Managing secure and low‑latency wireless data transfer
Matching the color scheme of the app
Increasing the phone's battery capacity
Explanation - Real‑time neural data requires fast, encrypted transmission to preserve privacy and usability.
Correct answer is: Managing secure and low‑latency wireless data transfer
Q.82 Which type of neural prosthesis is designed to restore vision by directly stimulating the retina?
Cochlear implant
Retinal implant
Deep brain stimulator
Spinal cord stimulator
Explanation - Retinal prostheses bypass damaged photoreceptors and stimulate remaining retinal neurons to convey visual information.
Correct answer is: Retinal implant
Q.83 What does the term "neural latency" specifically refer to in the context of evoked potentials?
The time between stimulus onset and the recorded neural response peak
The duration of the stimulus pulse
The interval between two consecutive spikes
The frequency of the stimulus
Explanation - Neural latency measures the speed of neural conduction and processing, useful for diagnosing pathway integrity.
Correct answer is: The time between stimulus onset and the recorded neural response peak
Q.84 Which design approach can reduce the risk of "wire breakage" in long‑term implanted neural leads?
Using rigid metal wires
Embedding the wires in a flexible polymer matrix
Increasing the wire diameter drastically
Adding extra connectors
Explanation - A flexible polymer absorbs mechanical stress, protecting the conductors from fatigue and breakage.
Correct answer is: Embedding the wires in a flexible polymer matrix
Q.85 In a neural prosthetic system, which component typically performs the conversion from analog neural signals to digital data?
Microcontroller unit (MCU)
Analog‑to‑Digital Converter (ADC)
Power management IC
Wireless transceiver
Explanation - The ADC samples the continuous analog voltage and converts it into a digital code for processing and transmission.
Correct answer is: Analog‑to‑Digital Converter (ADC)
Q.86 What is the primary reason for applying a "reference ground" electrode on the scalp during EEG recordings?
To deliver stimulation pulses
To serve as a stable voltage baseline for differential measurement
To increase the amplitude of brain signals
To power the EEG amplifier
Explanation - The reference ground provides a consistent point against which all active electrodes are compared, reducing common‑mode noise.
Correct answer is: To serve as a stable voltage baseline for differential measurement
Q.87 Which of the following is a typical symptom indicating that an implanted neural stimulator may be delivering excessive charge?
Mild tingling that disappears quickly
Persistent pain or tissue burning sensations
Improved motor function
Reduced battery usage
Explanation - Over‑stimulation can cause discomfort, heating, or tissue damage, signaling that charge limits are exceeded.
Correct answer is: Persistent pain or tissue burning sensations
Q.88 Which method is commonly used to assess the biocompatibility of a new electrode material before chronic implantation?
In‑vivo mouse implantation followed by histology
Measuring the material's color under a microscope
Testing the material's electrical conductivity in air
Evaluating its cost
Explanation - Histological analysis reveals inflammatory responses, scar formation, and cell viability around the implanted material.
Correct answer is: In‑vivo mouse implantation followed by histology
Q.89 What does the term "spike‑sorting" refer to in neural data analysis?
Classifying recorded spikes into distinct neuronal sources
Sorting electrodes by size
Ordering data packets for transmission
Filtering out high‑frequency noise
Explanation - Spike‑sorting algorithms assign each detected action potential to an individual neuron based on waveform features.
Correct answer is: Classifying recorded spikes into distinct neuronal sources
Q.90 Which of the following best describes the role of a 'compliant' substrate in a neural electrode array?
To increase electrical resistance
To match the mechanical properties of brain tissue and reduce chronic injury
To make the device heavier
To enhance magnetic coupling
Explanation - Compliance minimizes micromotion‑induced damage and improves long‑term stability of the neural interface.
Correct answer is: To match the mechanical properties of brain tissue and reduce chronic injury
Q.91 In a brain‑computer interface, which feature is most critical for real‑time control of a cursor on a screen?
High spatial resolution of recorded signals
Low latency between intention detection and command output
Large number of electrodes (>10,000)
Complexity of the decoding algorithm
Explanation - Fast response times are essential for intuitive and effective real‑time interaction with the cursor.
Correct answer is: Low latency between intention detection and command output
Q.92 Which phenomenon can cause an increase in recorded signal amplitude when an electrode is moved closer to an active neuron?
Signal attenuation
Volume conduction
Far‑field effect
Near‑field amplification
Explanation - Proximity reduces the distance for the electric field, increasing the observed amplitude due to near‑field effects.
Correct answer is: Near‑field amplification
Q.93 What is the main purpose of a 'cuff' electrode when used on peripheral nerves?
To record cortical activity
To wrap around the nerve and provide chronic stimulation or recording
To deliver drugs to the nerve
To measure blood flow
Explanation - Cuff electrodes encircle the nerve, allowing stable interface without penetrating the epineurium.
Correct answer is: To wrap around the nerve and provide chronic stimulation or recording
Q.94 Which safety metric is used to ensure that a neural stimulator does not exceed safe temperature limits in tissue?
Specific Absorption Rate (SAR)
Battery voltage rating
Electrode diameter
Signal-to-noise ratio
Explanation - SAR quantifies the rate at which RF energy is absorbed, ensuring that tissue heating stays within safe limits.
Correct answer is: Specific Absorption Rate (SAR)
Q.95 What does the term "field‑potential" generally refer to in neuroengineering?
The electrical potential measured at the surface of the skin
The summed extracellular voltage generated by a population of neurons
The voltage across a single ion channel
The magnetic field generated by the heart
Explanation - Field potentials (e.g., LFPs, EEG) represent the collective activity of many neurons within a region.
Correct answer is: The summed extracellular voltage generated by a population of neurons
Q.96 Which of the following is a common method to reduce the size of a neural implant’s power supply while maintaining functionality?
Using a larger battery
Implementing energy‑harvesting techniques (e.g., inductive or kinetic)
Increasing the voltage of the existing battery
Adding more LEDs
Explanation - Energy harvesting can supplement or replace bulky batteries, allowing smaller, lighter implants.
Correct answer is: Implementing energy‑harvesting techniques (e.g., inductive or kinetic)
Q.97 Which of the following best describes the role of a 'digital signal processor' (DSP) in a neural prosthetic system?
To amplify analog signals
To perform real‑time filtering and decoding of neural data
To store long‑term memory of the user
To provide power to the electrodes
Explanation - DSPs are optimized for rapid mathematical operations required for signal conditioning and decoding in closed‑loop systems.
Correct answer is: To perform real‑time filtering and decoding of neural data
Q.98 What is a primary advantage of using a 'multi‑modal' neural interface that combines electrical and optical stimulation?
Reduced cost of the device
Ability to target distinct neuronal populations with complementary modalities
Simplified surgical implantation
Elimination of the need for power
Explanation - Electrical stimulation offers depth, while optical stimulation provides cell‑type specificity; together they expand therapeutic possibilities.
Correct answer is: Ability to target distinct neuronal populations with complementary modalities
Q.99 Which of the following is a typical symptom of a malfunctioning neural recording front‑end amplifier?
Sudden increase in battery voltage
Flatline (no signal) on the display despite known neural activity
Improved signal clarity
Reduced device weight
Explanation - A failed amplifier cannot amplify incoming neural potentials, resulting in a loss of recorded data.
Correct answer is: Flatline (no signal) on the display despite known neural activity
Q.100 What does the term "chronaxie" characterize in the context of neural stimulation safety?
The maximum allowable voltage
The time constant for charge decay
The pulse duration at which twice the rheobase current is needed for excitation
The latency of the neural response
Explanation - Chronaxie provides a practical measure of excitability, informing safe pulse width selections.
Correct answer is: The pulse duration at which twice the rheobase current is needed for excitation
Q.101 Which design feature helps to mitigate "micro‑motion" induced damage in brain‑implanted electrode arrays?
Rigid titanium casing
Floating (compliant) anchor system
Increasing electrode length
Using thicker wires
Explanation - A floating anchor allows the device to move with the brain, reducing shear forces on the tissue‑electrode interface.
Correct answer is: Floating (compliant) anchor system
Q.102 In neural engineering, what does the term "closed‑loop" specifically imply about system operation?
The system operates without any external power source
Stimulation parameters are dynamically adjusted based on recorded neural feedback
All components are permanently fixed in place
The device only records, never stimulates
Explanation - Closed‑loop control uses ongoing measurements to modify stimulation in real time, enhancing efficacy and safety.
Correct answer is: Stimulation parameters are dynamically adjusted based on recorded neural feedback
Q.103 Which of the following is a key consideration when selecting the frequency of a wireless link for a neural implant?
The color of the device housing
Regulatory limits on tissue absorption and SAR
The number of electrodes
The brand of the microcontroller
Explanation - Frequency determines how much energy is absorbed by tissue; regulatory standards ensure safe exposure levels.
Correct answer is: Regulatory limits on tissue absorption and SAR
Q.104 What is the primary benefit of using a 'high‑impedance' electrode for extracellular recording?
Allows higher stimulation currents
Reduces thermal noise and improves signal isolation from distant sources
Increases the physical size of the electrode
Enables direct intracellular access
Explanation - High impedance limits the recording volume, making the electrode more selective for nearby neuronal activity.
Correct answer is: Reduces thermal noise and improves signal isolation from distant sources
Q.105 Which of the following best defines "neuroprosthetic"?
A device that records blood pressure
An implant that restores or replaces lost neural function
A medication that enhances cognition
A software tool for brain imaging
Explanation - Neuroprosthetics interface with the nervous system to restore sensory, motor, or cognitive abilities.
Correct answer is: An implant that restores or replaces lost neural function
Q.106 Why is a 'low‑pass filter' often applied to neural spike recordings?
To remove high‑frequency noise and preserve the spike shape
To increase the amplitude of the signal
To convert the signal to digital format
To amplify low‑frequency components
Explanation - Low‑pass filtering attenuates frequencies above the spike bandwidth, reducing high‑frequency artifacts while retaining the spike waveform.
Correct answer is: To remove high‑frequency noise and preserve the spike shape
Q.107 Which of the following is an essential step before chronic implantation of a neural electrode array in humans?
Running a computer simulation only
Performing sterilization and biocompatibility testing
Painting the device in bright colors
Attaching a large external antenna
Explanation - Ensuring sterility and biocompatibility is critical to prevent infection and adverse tissue reactions.
Correct answer is: Performing sterilization and biocompatibility testing
Q.108 What does the term "neural integration" refer to in the context of biomedical devices?
Combining multiple neural recordings into one file
The process by which an implanted device becomes functionally and biologically compatible with host neural tissue
Merging EEG and EMG signals
Connecting two computers together
Explanation - Neural integration involves both mechanical and biochemical compatibility, allowing stable long‑term operation.
Correct answer is: The process by which an implanted device becomes functionally and biologically compatible with host neural tissue
Q.109 Which of the following is a typical method for delivering power to a fully implanted neural device without transcutaneous wires?
Solar cells
Inductive coupling (wireless charging)
Battery swapping through a skin opening
Manual cranking
Explanation - Inductive coils can transfer energy across the skin non‑invasively, recharging implanted batteries or powering devices directly.
Correct answer is: Inductive coupling (wireless charging)