Q.1 What is the primary purpose of a neural interface?
To generate electrical power for the brain
To record or stimulate neural activity
To cool the brain tissue
To deliver nutrients to neurons
Explanation - Neural interfaces are designed to either sense (record) or influence (stimulate) the electrical activity of neurons.
Correct answer is: To record or stimulate neural activity
Q.2 Which type of electrode is commonly used for chronic brain recordings?
Carbon fiber microelectrode
Gold-plated surface electrode
Silicon Utah array
Liquid metal electrode
Explanation - Silicon Utah arrays are microfabricated electrode arrays designed for stable, long‑term implantation in the cortex.
Correct answer is: Silicon Utah array
Q.3 What does the term 'charge density' refer to in neural stimulation?
The number of neurons activated per second
The amount of electrical charge delivered per unit electrode area
The voltage applied across the electrode
The speed of the stimulation pulse
Explanation - Charge density (µC/cm²) is a safety metric that limits how much charge can be safely delivered through an electrode to avoid tissue damage.
Correct answer is: The amount of electrical charge delivered per unit electrode area
Q.4 Which of the following is a non‑invasive neural stimulation technique?
Deep brain stimulation (DBS)
Transcranial magnetic stimulation (TMS)
Intracortical microstimulation (ICMS)
Optogenetic stimulation
Explanation - TMS uses magnetic fields applied over the scalp to induce electric currents in the brain without surgery.
Correct answer is: Transcranial magnetic stimulation (TMS)
Q.5 In a biphasic stimulation pulse, why are two phases used?
To increase the amplitude of stimulation
To reduce net charge accumulation on the electrode
To double the number of neurons activated
To shorten the pulse duration
Explanation - A biphasic pulse delivers equal and opposite charges, minimizing net DC offset and reducing the risk of electrode corrosion and tissue damage.
Correct answer is: To reduce net charge accumulation on the electrode
Q.6 Which material is widely used for coating neural electrodes to improve biocompatibility?
Silicone rubber
Polyimide
Iridium oxide
Aluminum foil
Explanation - Iridium oxide coatings increase charge injection capacity and are more stable in biological environments.
Correct answer is: Iridium oxide
Q.7 What is the typical frequency range used for therapeutic deep brain stimulation (DBS) in Parkinson’s disease?
1‑10 Hz
20‑50 Hz
130‑200 Hz
500‑1000 Hz
Explanation - High‑frequency stimulation (≈130 Hz) in DBS alleviates motor symptoms in Parkinson’s disease.
Correct answer is: 130‑200 Hz
Q.8 Which of the following best describes a ‘closed‑loop’ neural interface?
An implant that only records neural activity
A system that records and then automatically adjusts stimulation based on feedback
A device that delivers constant stimulation regardless of brain state
A wireless charger for neural implants
Explanation - Closed‑loop interfaces use recorded signals to adapt stimulation parameters in real time, improving efficacy and safety.
Correct answer is: A system that records and then automatically adjusts stimulation based on feedback
Q.9 What is the primary advantage of using microelectrode arrays (MEAs) for cortical stimulation?
They can stimulate the entire brain simultaneously
They provide spatially selective stimulation of small neuronal populations
They do not require any power source
They are completely immune to corrosion
Explanation - MEAs consist of many small electrodes, allowing precise targeting of specific cortical regions.
Correct answer is: They provide spatially selective stimulation of small neuronal populations
Q.10 Which neural signal is most commonly used for brain‑computer interfaces (BCIs) that rely on non‑invasive recording?
Local field potentials (LFPs)
Electroencephalography (EEG) signals
Single‑unit spikes
Magnetoencephalography (MEG) signals
Explanation - EEG captures voltage fluctuations at the scalp and is widely used in non‑invasive BCIs.
Correct answer is: Electroencephalography (EEG) signals
Q.11 What is the typical pulse width range for safe peripheral nerve stimulation?
0.1‑0.5 µs
10‑100 µs
200‑500 µs
1‑5 ms
Explanation - Peripheral nerve stimulation often uses pulse widths in the 200‑500 µs range to efficiently activate axons without excess charge.
Correct answer is: 200‑500 µs
Q.12 Which phenomenon describes the decrease in neural response after continuous stimulation?
Synaptic potentiation
Neural adaptation
Action potential amplification
Electrode polarization
Explanation - Neural adaptation (or habituation) reduces the response of neurons to constant or repetitive stimuli.
Correct answer is: Neural adaptation
Q.13 What is the main safety concern when delivering high‑current stimulation through an implanted electrode?
Magnetic field distortion
Electrode heating leading to tissue damage
Loss of electrode conductivity
Signal amplification
Explanation - Excessive current can cause Joule heating, potentially damaging surrounding neural tissue.
Correct answer is: Electrode heating leading to tissue damage
Q.14 Which of the following is a key advantage of optogenetic stimulation over electrical stimulation?
It can be applied without any genetic modification
It provides cell‑type specific activation
It requires lower power consumption
It does not need any external hardware
Explanation - Optogenetics uses light‑sensitive proteins introduced genetically, allowing precise control of specific neuron types.
Correct answer is: It provides cell‑type specific activation
Q.15 What does the term ‘cortical spreading depression’ refer to?
A rapid increase in cortical temperature
A wave of neuronal depolarization that suppresses activity
The propagation of a seizure across the cortex
A type of electrode malfunction
Explanation - Cortical spreading depression is a slowly propagating wave of depolarization followed by a period of neural silence, implicated in migraine aura.
Correct answer is: A wave of neuronal depolarization that suppresses activity
Q.16 Which of the following is NOT a typical component of a neural stimulator circuit?
Current source
Voltage regulator
Digital-to-analog converter (DAC)
Laser diode
Explanation - Laser diodes are used in optical stimulation, not in standard electrical neural stimulators.
Correct answer is: Laser diode
Q.17 In the context of neural interfaces, what does the acronym 'FES' stand for?
Fast Electrical Sensing
Functional Electrical Stimulation
Frequency Emission System
Fiber‑optic Electro‑Stimulation
Explanation - FES refers to the use of electrical currents to activate muscles in individuals with paralysis, restoring functional movement.
Correct answer is: Functional Electrical Stimulation
Q.18 Which of the following describes the ‘Rheobase’ of a neuron?
The maximum firing rate of a neuron
The minimum current required to elicit an action potential with a long pulse duration
The time it takes for a neuron to recover after an action potential
The resistance of the neuronal membrane
Explanation - Rheobase is a fundamental electrophysiological parameter used to characterize neuronal excitability.
Correct answer is: The minimum current required to elicit an action potential with a long pulse duration
Q.19 What is the purpose of a ‘reference electrode’ in a neural recording system?
To deliver stimulation pulses
To provide a stable voltage baseline for differential measurements
To power the implant wirelessly
To cool the recording site
Explanation - Reference electrodes serve as a stable point of comparison, allowing accurate measurement of neural potentials.
Correct answer is: To provide a stable voltage baseline for differential measurements
Q.20 Which signal processing technique is commonly used to extract spike timings from raw neural recordings?
Fourier transform
Wavelet denoising
Band-pass filtering followed by threshold detection
Principal component analysis
Explanation - Spikes are high‑frequency events; band‑pass filtering isolates them, and a voltage threshold identifies individual spikes.
Correct answer is: Band-pass filtering followed by threshold detection
Q.21 What is the typical impedance range for a well‑functioning microelectrode used for chronic recording?
1‑10 Ω
10‑100 kΩ
1‑10 MΩ
100‑500 MΩ
Explanation - Impedance in the tens of kilo‑ohms balances signal quality and charge injection capacity for chronic implants.
Correct answer is: 10‑100 kΩ
Q.22 Which neural stimulation paradigm is most effective for restoring vision in retinal prostheses?
Continuous high‑frequency stimulation
Pulsed charge‑balanced biphasic stimulation
Direct current (DC) stimulation
Magnetic induction
Explanation - Biphasic pulses reduce electrochemical damage while providing precise activation of retinal ganglion cells.
Correct answer is: Pulsed charge‑balanced biphasic stimulation
Q.23 In a neural interface, what does the term ‘crosstalk’ refer to?
Electrical interference between adjacent electrode channels
Communication between the implant and an external device
The spread of stimulation to unintended brain regions
Both A and C
Explanation - Crosstalk can occur electrically between channels and physiologically when stimulation spreads beyond the target area.
Correct answer is: Both A and C
Q.24 Which of the following is a key factor influencing the selectivity of peripheral nerve stimulation?
Electrode material only
Pulse amplitude, pulse width, and electrode geometry
Temperature of the surrounding tissue
Color of the electrode
Explanation - These parameters determine which nerve fibers (size, type) are activated during stimulation.
Correct answer is: Pulse amplitude, pulse width, and electrode geometry
Q.25 What does the term ‘neuroplasticity’ mean in the context of neural stimulation therapies?
Permanent damage to neural tissue
The brain’s ability to reorganize and form new connections
An increase in neuron temperature
A type of electrode coating
Explanation - Neurostimulation can harness neuroplasticity to promote functional recovery after injury.
Correct answer is: The brain’s ability to reorganize and form new connections
Q.26 Which of the following is a common metric for evaluating the performance of a brain‑computer interface?
Bit‑rate (bits per minute)
Voltage drop across the electrode
Impedance spectroscopy
Stimulation pulse shape
Explanation - Bit‑rate quantifies how much information can be transmitted from the brain to the computer per unit time.
Correct answer is: Bit‑rate (bits per minute)
Q.27 In a cochlear implant, the electrode array is inserted into which part of the inner ear?
Semicircular canals
Cochlear duct (scala tympani)
Eustachian tube
Otic capsule
Explanation - The electrode array is placed in the scala tympani to stimulate auditory nerve fibers directly.
Correct answer is: Cochlear duct (scala tympani)
Q.28 Which stimulation waveform is most energy‑efficient for activating excitable tissue?
Square pulse
Sinusoidal wave
Triangular pulse
Exponential decay pulse
Explanation - Square pulses deliver a constant amplitude for the duration of the pulse, minimizing energy wasted in rising/falling edges.
Correct answer is: Square pulse
Q.29 What is the typical latency (time delay) between a stimulation pulse and the evoked muscle response in peripheral nerve stimulation?
1‑2 ms
5‑10 ms
20‑30 ms
100‑200 ms
Explanation - Peripheral motor responses usually appear within 5–10 ms after a suprathreshold stimulus.
Correct answer is: 5‑10 ms
Q.30 Which of the following is a major challenge for long‑term implantable neural interfaces?
Battery depletion
Immune response and gliosis
Signal attenuation due to humidity
Excessive heat generation from surrounding muscles
Explanation - The body's immune reaction can encapsulate electrodes with glial scar tissue, degrading signal quality over time.
Correct answer is: Immune response and gliosis
Q.31 In the context of neural stimulation, what does the term ‘strength‑duration curve’ depict?
The relationship between stimulus amplitude and pulse duration required to elicit an action potential
The decay of voltage over time after a stimulus
The power consumption of the stimulator
The frequency response of the neural tissue
Explanation - The strength‑duration curve shows how lower currents can be effective if the pulse is sufficiently long, and vice versa.
Correct answer is: The relationship between stimulus amplitude and pulse duration required to elicit an action potential
Q.32 Which type of neural interface uses a flexible polymer substrate to conform to brain surface anatomy?
Utah array
ECoG (electrocorticography) grid
Intracortical needle electrode
Deep brain probe
Explanation - ECoG grids are thin, flexible arrays placed on the cortical surface, offering high spatial resolution with reduced invasiveness.
Correct answer is: ECoG (electrocorticography) grid
Q.33 Which safety standard provides guidelines for charge density limits in neural stimulation?
ISO 9001
IEC 60601‑1
IEEE 802.11
ASTM D3359
Explanation - IEC 60601‑1 includes limits for safe charge density to prevent tissue injury during electrical stimulation.
Correct answer is: IEC 60601‑1
Q.34 What is the main advantage of using a ‘current‑controlled’ stimulator over a ‘voltage‑controlled’ stimulator?
It consumes less power
It automatically adjusts to changes in tissue impedance
It can deliver higher voltages
It does not require a power source
Explanation - Current‑controlled devices maintain a constant current regardless of impedance fluctuations, ensuring consistent stimulation dose.
Correct answer is: It automatically adjusts to changes in tissue impedance
Q.35 Which neurophysiological phenomenon can be used as a feedback signal for a closed‑loop DBS system treating essential tremor?
Local field potentials (LFPs) in the subthalamic nucleus
Electrocardiogram (ECG) amplitude
Skin temperature
Blood oxygen saturation
Explanation - LFPs reflect pathological oscillations; their amplitude can be monitored to adapt DBS parameters in real time.
Correct answer is: Local field potentials (LFPs) in the subthalamic nucleus
Q.36 What is the function of a ‘charge‑balancing capacitor’ in a neural stimulator circuit?
To increase the voltage of the stimulation pulse
To store and release charge, ensuring net zero DC over each pulse cycle
To cool the electrode during stimulation
To amplify recorded neural signals
Explanation - Charge‑balancing capacitors help create biphasic pulses that prevent net charge accumulation.
Correct answer is: To store and release charge, ensuring net zero DC over each pulse cycle
Q.37 Which of the following best describes the term ‘neural decoding’?
Converting neural signals into meaningful commands or information
Breaking down neurons into smaller components
Measuring the temperature of brain tissue
Stimulating neurons with laser light
Explanation - Neural decoding extracts intended actions or thoughts from recorded brain activity for BCI applications.
Correct answer is: Converting neural signals into meaningful commands or information
Q.38 When designing an implanted neural interface, why is hermetic sealing important?
To prevent water ingress that could short‑circuit electronics
To make the device visible on X‑ray
To increase the flexibility of the implant
To improve the electrode’s conductivity
Explanation - Hermetic packages protect sensitive electronics from the corrosive bodily environment, ensuring long‑term functionality.
Correct answer is: To prevent water ingress that could short‑circuit electronics
Q.39 Which neural interface technology utilizes microwire bundles for recording from deep brain structures?
Silicon micro‑LED array
Carbon fiber microelectrode array
Neuropixels probe
Transcranial Doppler sensor
Explanation - Neuropixels probes contain thousands of densely packed recording sites along a thin shank, enabling high‑density recordings.
Correct answer is: Neuropixels probe
Q.40 What is the primary purpose of a ‘stimulus artifact’ removal algorithm in neural data processing?
To enhance the amplitude of recorded spikes
To eliminate the large voltage deflection caused by the stimulation pulse
To increase the stimulation current
To reduce the power consumption of the stimulator
Explanation - Stimulus artifacts can mask underlying neural activity; removal algorithms recover the true neural response.
Correct answer is: To eliminate the large voltage deflection caused by the stimulation pulse
Q.41 Which of the following is a common method for wireless power transfer to an implanted neural device?
Inductive coupling
Radio‑frequency (RF) telemetry
Acoustic (ultrasound) power transfer
All of the above
Explanation - Inductive, RF, and ultrasonic methods have all been demonstrated for wireless powering of neural implants.
Correct answer is: All of the above
Q.42 In the context of cortical stimulation, what does the term ‘phosphene’ refer to?
A type of electrode material
A visual sensation (light flash) induced by stimulating the visual cortex
A measurement of electrode impedance
An auditory artifact
Explanation - Phosphenes are perceived when electrical stimulation activates visual pathways, useful for visual prosthesis research.
Correct answer is: A visual sensation (light flash) induced by stimulating the visual cortex
Q.43 Which of the following best explains why low‑frequency stimulation (≤10 Hz) can be used to induce long‑term depression (LTD) in synaptic connections?
It increases the temperature of the tissue
It reduces calcium influx leading to synaptic weakening
It creates a large electric field that destroys synapses
It triggers massive action potential firing
Explanation - Low‑frequency stimulation leads to modest calcium rise, favoring LTD mechanisms over LTP.
Correct answer is: It reduces calcium influx leading to synaptic weakening
Q.44 What is the role of ‘glial scar’ formation around chronic neural implants?
To improve electrical conductivity
To protect neurons from stimulation
To electrically isolate the electrode, degrading signal quality
To enhance the mechanical stability of the implant
Explanation - Glial scar tissue is insulating and hampers both recording and stimulation efficacy over time.
Correct answer is: To electrically isolate the electrode, degrading signal quality
Q.45 Which parameter is most directly associated with the perceptual intensity of an electrically evoked tactile sensation?
Stimulation frequency
Pulse amplitude
Electrode material
Implant size
Explanation - Higher current amplitudes recruit more nerve fibers, leading to stronger perceived sensations.
Correct answer is: Pulse amplitude
Q.46 Which computational model is frequently used to predict neural activation thresholds during electrical stimulation?
Hodgkin‑Huxley model
Navier‑Stokes equations
Lotka‑Volterra model
Miller‑Abrahams hopping model
Explanation - The Hodgkin‑Huxley equations describe the ionic currents underlying action potential generation, useful for threshold estimation.
Correct answer is: Hodgkin‑Huxley model
Q.47 What does the acronym ‘ECoG’ stand for?
Electro‑cortical oscillation generator
Electrocorticography
Electrical conduction gauge
Electrochemical oxygen graph
Explanation - ECoG records electrical activity directly from the cortical surface, offering higher spatial resolution than scalp EEG.
Correct answer is: Electrocorticography
Q.48 Which of the following is a key limitation of surface (non‑invasive) EEG for neural interfacing?
High spatial resolution
Low signal‑to‑noise ratio due to skull attenuation
Inability to detect any brain activity
Requirement for surgical implantation
Explanation - The skull and scalp dampen neural signals, reducing the fidelity of surface EEG recordings.
Correct answer is: Low signal‑to‑noise ratio due to skull attenuation
Q.49 In the context of neural prosthetics, what is ‘sensory feedback’?
A visual display of the prosthetic’s status
Electrical stimulation that conveys tactile information back to the user
A warning alarm when battery is low
The sound emitted by the device
Explanation - Sensory feedback involves delivering patterned stimulation to the peripheral nervous system to recreate a sense of touch.
Correct answer is: Electrical stimulation that conveys tactile information back to the user
Q.50 Which factor primarily determines the spatial resolution of an intracortical microstimulation (ICMS) site?
Electrode tip diameter
Battery voltage
External magnetic field strength
Cable length to the stimulator
Explanation - Smaller tip diameters confine the electric field, allowing more precise activation of local neuronal populations.
Correct answer is: Electrode tip diameter
Q.51 What is the main purpose of a ‘ground’ electrode in a neural recording setup?
To deliver the stimulation pulse
To provide a reference point that reduces common‑mode noise
To increase the amplitude of the recorded signal
To power the recording amplifier
Explanation - A ground electrode helps eliminate environmental electrical interference by establishing a stable reference.
Correct answer is: To provide a reference point that reduces common‑mode noise
Q.52 Which neural interface technology is most appropriate for chronic monitoring of slow cortical potentials?
Microneedle electrode array
ECoG grid
Single‑unit microelectrode
Transcranial magnetic coil
Explanation - ECoG grids are well‑suited for recording low‑frequency cortical activity over extended periods.
Correct answer is: ECoG grid
Q.53 Why is ‘charge recovery’ important after delivering a stimulation pulse?
To prevent electrode corrosion and tissue damage
To increase the power consumption of the device
To amplify the recorded neural signal
To speed up the stimulation pulse
Explanation - Recovering charge (often via a reverse pulse) neutralizes net DC, preserving electrode integrity and biocompatibility.
Correct answer is: To prevent electrode corrosion and tissue damage
Q.54 Which of the following best describes ‘electrochemical impedance spectroscopy’ (EIS) in the context of neural electrodes?
A method to measure the mechanical strength of an electrode
A technique to assess the frequency‑dependent impedance of the electrode‑tissue interface
A way to record neural spikes
A protocol for wireless data transmission
Explanation - EIS characterizes how the electrode’s impedance varies with frequency, informing design and safety.
Correct answer is: A technique to assess the frequency‑dependent impedance of the electrode‑tissue interface
Q.55 Which phenomenon can cause a decrease in stimulation efficacy over time due to tissue reaction?
Electrode drift
Glial encapsulation
Battery depletion
Signal aliasing
Explanation - Glial scar formation insulates the electrode, raising impedance and reducing effective stimulation.
Correct answer is: Glial encapsulation
Q.56 What is the typical sampling rate needed to accurately capture action potentials in neural recordings?
<500 Hz
1‑2 kHz
10‑20 kHz
100‑200 kHz
Explanation - Action potentials have fast rising edges (~0.5 ms), requiring sampling rates of at least 10 kHz to avoid aliasing.
Correct answer is: 10‑20 kHz
Q.57 In neural stimulation, what does the term ‘chronaxie’ refer to?
The minimum pulse width needed to evoke a response at twice the rheobase current
The time between two consecutive spikes
The latency of the evoked response
The duration of the electrode’s lifespan
Explanation - Chronaxie is a key parameter derived from the strength‑duration curve, indicating tissue excitability.
Correct answer is: The minimum pulse width needed to evoke a response at twice the rheobase current
Q.58 Which of the following is a major advantage of using a ‘flexible’ neural probe over a rigid silicon probe?
Higher electrical conductivity
Better mechanical compliance with brain tissue, reducing chronic damage
Ability to deliver higher currents
Simpler fabrication process
Explanation - Flexible probes conform to brain motion, mitigating micromotion‑induced injury and scar formation.
Correct answer is: Better mechanical compliance with brain tissue, reducing chronic damage
Q.59 What is the purpose of a ‘shunt resistor’ in a current‑controlled stimulator circuit?
To limit the maximum voltage across the electrode
To measure the actual current delivered to the electrode
To increase the stimulation frequency
To provide a reference ground
Explanation - A shunt resistor creates a voltage drop proportional to current, enabling precise current monitoring.
Correct answer is: To measure the actual current delivered to the electrode
Q.60 Which of the following describes the ‘neuronal recruitment order’ during electrical stimulation of a peripheral nerve?
Large‑diameter fibers are recruited before small‑diameter fibers
Small‑diameter fibers are recruited before large‑diameter fibers
All fibers are recruited simultaneously
Recruitment depends only on electrode material
Explanation - Larger axons have lower thresholds and are activated first during extracellular stimulation.
Correct answer is: Large‑diameter fibers are recruited before small‑diameter fibers
Q.61 Which type of neural interface is used to record from the auditory nerve after cochlear implantation?
Surface EEG electrode
Intracochlear electrode array
Transcranial magnetic coil
Optical fiber probe
Explanation - Cochlear implants contain electrode arrays inserted into the scala tympani to stimulate the auditory nerve.
Correct answer is: Intracochlear electrode array
Q.62 What is the main reason for using a ‘bipolar’ recording configuration rather than a ‘monopolar’ one?
To increase the amplitude of the recorded signal
To reduce common‑mode interference and improve spatial selectivity
To lower the power consumption of the amplifier
To simplify the wiring
Explanation - Bipolar recordings subtract signals from two nearby electrodes, canceling far‑field noise and focusing on local activity.
Correct answer is: To reduce common‑mode interference and improve spatial selectivity
Q.63 Which of the following is a common method to test the functionality of a newly implanted neural electrode before chronic use?
Applying a high‑frequency magnetic field
Measuring electrode impedance in situ
Running a battery endurance test
Performing a visual inspection only
Explanation - Impedance testing verifies that the electrode‑tissue interface is intact and suitable for recording/stimulation.
Correct answer is: Measuring electrode impedance in situ
Q.64 Which of the following best describes the purpose of a ‘neural prosthesis’?
To replace a damaged neural structure with an artificial device that restores function
To amplify brain signals for better hearing
To cool the brain during surgery
To generate electricity from brain activity
Explanation - Neural prostheses aim to restore lost sensory, motor, or cognitive functions by interfacing with the nervous system.
Correct answer is: To replace a damaged neural structure with an artificial device that restores function
Q.65 In a neural stimulation experiment, why might a researcher use a ‘ramp‑up’ protocol for current amplitude?
To gradually adapt the tissue and reduce sudden shock
To increase the power consumption of the device
To shorten the duration of each pulse
To improve the wireless data transmission
Explanation - A ramp‑up helps avoid abrupt high‑current delivery that could cause discomfort or tissue injury.
Correct answer is: To gradually adapt the tissue and reduce sudden shock
Q.66 Which of the following neural signals is most suitable for decoding intended hand movements in a motor BCI?
Local field potentials (LFPs)
Single‑unit spike activity
Electrooculogram (EOG)
Electrocardiogram (ECG)
Explanation - Spike trains from motor cortex neurons provide high‑resolution information about movement intention.
Correct answer is: Single‑unit spike activity
Q.67 What is the typical safety limit for charge density per phase in microelectrode stimulation for chronic use?
0.1 µC/cm²
1 µC/cm²
10 µC/cm²
100 µC/cm²
Explanation - Most chronic neural stimulation guidelines recommend staying below ~10 µC/cm² per phase to avoid tissue damage.
Correct answer is: 10 µC/cm²
Q.68 Which neural interface technology employs micro‑LEDs to optogenetically stimulate specific neuron populations?
Optrode array
Silicon microelectrode array
ECoG grid
Deep brain stimulator
Explanation - Optrodes combine optical fibers or micro‑LEDs with recording electrodes for simultaneous optical stimulation and electrical recording.
Correct answer is: Optrode array
Q.69 Which of the following best explains why higher stimulation frequencies (>100 Hz) can lead to a phenomenon called ‘neural fatigue’?
Neurons cannot repolarize quickly enough, leading to decreased excitability
The electrode temperature rises dramatically
The battery runs out faster
The pulse amplitude automatically decreases
Explanation - At high frequencies, refractory periods limit the ability of neurons to fire on every pulse, causing reduced response.
Correct answer is: Neurons cannot repolarize quickly enough, leading to decreased excitability
Q.70 What is the primary advantage of using a ‘digital signal processor’ (DSP) in a real‑time neural interface system?
To increase the voltage of stimulation pulses
To perform fast, on‑chip filtering and decoding of neural signals
To store large amounts of data for later analysis
To provide wireless power to the implant
Explanation - DSPs enable low‑latency processing essential for closed‑loop neural interfaces.
Correct answer is: To perform fast, on‑chip filtering and decoding of neural signals
Q.71 Which of the following is a typical symptom of over‑stimulation in deep brain stimulation therapy?
Improved motor function
Seizure activity
Speech and gait disturbances
Reduced heart rate
Explanation - Excessive DBS current can spread to adjacent structures, causing side effects such as dysarthria and gait problems.
Correct answer is: Speech and gait disturbances
Q.72 In the design of a neural stimulator, what is the purpose of a ‘compliance voltage’ specification?
The maximum voltage the device can supply to maintain the desired current across varying impedances
The voltage required to turn on the device
The voltage needed for wireless communication
The voltage used for battery charging
Explanation - Compliance voltage ensures the stimulator can deliver the set current even when electrode impedance changes.
Correct answer is: The maximum voltage the device can supply to maintain the desired current across varying impedances
Q.73 Which of the following is an example of a ‘bio‑electronic medicine’ application?
Implantable insulin pump
Vagus nerve stimulation for inflammatory disease treatment
Pacemaker for heart rhythm control
Cochlear implant for hearing loss
Explanation - Vagus nerve stimulation modulates immune responses and is a key bio‑electronic medicine approach.
Correct answer is: Vagus nerve stimulation for inflammatory disease treatment
Q.74 Which term describes the phenomenon where the brain adapts to a constant level of stimulation, reducing its effectiveness over time?
Neurogenesis
Habituation
Synaptic pruning
Neuroinflammation
Explanation - Habituation is a form of neural adaptation where responsiveness declines with persistent stimulation.
Correct answer is: Habituation
Q.75 What is the primary benefit of using a ‘multichannel’ neural stimulator for cortical mapping?
It can deliver higher current levels
It can stimulate multiple brain regions independently, enabling detailed functional maps
It reduces the need for a power source
It eliminates the need for surgical implantation
Explanation - Multichannel devices allow precise, simultaneous stimulation across many sites, facilitating comprehensive cortical mapping.
Correct answer is: It can stimulate multiple brain regions independently, enabling detailed functional maps
Q.76 Which of the following best defines the term ‘neural interfacing latency’?
The time it takes for an electrode to be fabricated
The delay between a recorded neural event and the system’s response (e.g., stimulation)
The duration of the stimulation pulse
The time required for battery charging
Explanation - Latency is critical in closed‑loop systems; lower latency leads to more accurate and timely interventions.
Correct answer is: The delay between a recorded neural event and the system’s response (e.g., stimulation)
Q.77 In the context of neural stimulation safety, what does the ‘Shannon equation’ predict?
Maximum permissible pulse frequency
Safe charge density limits based on pulse width and electrode surface area
Battery life of an implanted device
Optimal electrode placement
Explanation - Shannon’s model relates charge per phase, pulse width, and electrode area to estimate safe stimulation parameters.
Correct answer is: Safe charge density limits based on pulse width and electrode surface area
Q.78 Which of the following is a common method to reduce the size of a neural implant’s power consumption?
Using high‑frequency stimulation
Employing duty‑cycled operation and low‑power ASICs
Increasing the stimulation amplitude
Adding more electrodes
Explanation - Duty cycling and custom low‑power application‑specific integrated circuits (ASICs) extend battery life.
Correct answer is: Employing duty‑cycled operation and low‑power ASICs
Q.79 What is the main challenge of using ‘optogenetics’ in human neural interfaces compared to animal models?
Lack of suitable light sources
Difficulty delivering genes encoding light‑sensitive proteins safely and effectively
Insufficient power in human brain tissue
Inability to record neural activity
Explanation - Gene delivery for opsins raises safety, regulatory, and ethical concerns in humans.
Correct answer is: Difficulty delivering genes encoding light‑sensitive proteins safely and effectively
Q.80 Which of the following best explains why ‘micro‑LEDs’ are advantageous for high‑resolution optical neural stimulation?
They emit higher intensity light than conventional LEDs
Their small size enables precise spatial targeting of individual neurons
They require no power source
They are transparent to neural signals
Explanation - Micro‑LEDs can be integrated directly onto probes, delivering light to specific microscopic regions.
Correct answer is: Their small size enables precise spatial targeting of individual neurons
Q.81 Which computational technique is commonly used to model electric fields generated by neural stimulation electrodes in heterogeneous brain tissue?
Finite element method (FEM)
Monte Carlo simulation
Molecular dynamics
Discrete Fourier transform
Explanation - FEM allows detailed modeling of electric fields accounting for tissue conductivity variations.
Correct answer is: Finite element method (FEM)
Q.82 What does the term ‘bidirectional’ neural interface refer to?
A device that can both record neural activity and deliver stimulation
An electrode that can operate in both AC and DC modes
A system that works in both wet and dry environments
A wireless protocol supporting uplink and downlink
Explanation - Bidirectional interfaces enable closed‑loop operation by sensing and modulating neural circuits.
Correct answer is: A device that can both record neural activity and deliver stimulation
Q.83 Which of the following best describes the purpose of ‘artifact suppression’ in a closed‑loop neural stimulator?
To increase stimulation current
To prevent stimulation pulses from corrupting the recorded neural signal used for feedback
To reduce battery consumption
To enhance wireless data transmission
Explanation - Artifact suppression techniques ensure that the feedback signal reflects true neural activity, not stimulation-induced noise.
Correct answer is: To prevent stimulation pulses from corrupting the recorded neural signal used for feedback
Q.84 In a neural interface, which of the following is a typical method for achieving ‘spatial multiplexing’ of stimulation channels?
Using time‑division multiplexing (TDM) to address multiple electrodes sequentially
Increasing the voltage of each channel
Reducing the pulse width to zero
Employing a single large electrode for all channels
Explanation - TDM allows a limited number of driver circuits to control many electrodes by rapidly switching between them.
Correct answer is: Using time‑division multiplexing (TDM) to address multiple electrodes sequentially
Q.85 Which of the following neural signal modalities is most suitable for decoding slow cortical potentials associated with attention states?
Spike trains
Local field potentials (LFPs)
Electromyography (EMG)
Electrocardiogram (ECG)
Explanation - LFPs capture low‑frequency activity (0.5–30 Hz) linked to cognitive states like attention.
Correct answer is: Local field potentials (LFPs)
Q.86 What is a key advantage of using ‘hydrogel’ coatings on neural electrodes?
They make the electrode completely rigid
They improve biocompatibility and reduce inflammatory response
They increase the electrode's electrical resistance
They enable the electrode to emit light
Explanation - Hydrogels are soft, water‑rich materials that better match brain tissue mechanics, mitigating scar formation.
Correct answer is: They improve biocompatibility and reduce inflammatory response
Q.87 Which of the following is a commonly used metric to evaluate the energy efficiency of a neural stimulator?
Charge per pulse (µC)
Power consumption per pulse (µJ)
Stimulation frequency (Hz)
Electrode impedance (kΩ)
Explanation - Energy per pulse quantifies how much power the device uses for each stimulation event, critical for battery‑operated implants.
Correct answer is: Power consumption per pulse (µJ)
Q.88 Which phenomenon can cause an implanted electrode to shift position over time, potentially degrading signal quality?
Electrode corrosion
Brain micromotion due to pulsatile blood flow and respiration
Battery depletion
Signal aliasing
Explanation - Micromotion can lead to relative movement between the electrode and neural tissue, affecting recording stability.
Correct answer is: Brain micromotion due to pulsatile blood flow and respiration
Q.89 What is the purpose of using a ‘cuff electrode’ around a peripheral nerve?
To record the nerve’s temperature
To provide a stable electrical interface for stimulation or recording while minimizing tissue damage
To deliver drugs directly into the nerve
To measure blood flow in the nerve
Explanation - Cuff electrodes wrap around nerves, offering chronic access with reduced invasiveness compared to penetrating electrodes.
Correct answer is: To provide a stable electrical interface for stimulation or recording while minimizing tissue damage
Q.90 Which of the following describes the main goal of a ‘brain‑spine interface’ (BSI)?
To record spinal cord activity for diagnostic purposes only
To restore motor function by linking cortical signals directly to spinal cord stimulation
To monitor heart rate via the spinal column
To deliver medication to the brain through the spinal fluid
Explanation - BSI systems decode cortical intent and use that to drive spinal stimulation, bypassing damaged pathways.
Correct answer is: To restore motor function by linking cortical signals directly to spinal cord stimulation
Q.91 What does the term ‘neural dust’ refer to in emerging neural interface technologies?
Microscopic particles that emit light when stimulated
Wireless, sub‑millimeter sensor nodes that can be implanted and powered by ultrasound
A type of biodegradable electrode material
A computational model of neural activity
Explanation - Neural dust devices are tiny, untethered sensors that can record or stimulate and are powered remotely.
Correct answer is: Wireless, sub‑millimeter sensor nodes that can be implanted and powered by ultrasound
Q.92 Which of the following is a major limitation of using high‑frequency (>1 kHz) stimulation for peripheral nerve activation?
Inability to activate any axons
Increased risk of heating and tissue damage
Reduced selectivity for fiber type
Both B and C
Explanation - High frequencies can cause excessive heating and tend to recruit larger fibers, reducing selectivity.
Correct answer is: Both B and C
Q.93 In a neural prosthetic system, why is ‘latency jitter’ undesirable?
It causes the implant to overheat
It leads to unpredictable timing of stimulation relative to neural events, degrading closed‑loop performance
It increases the battery consumption
It reduces the amplitude of recorded signals
Explanation - Consistent timing is crucial for effective feedback; jitter introduces variability that can compromise therapeutic outcomes.
Correct answer is: It leads to unpredictable timing of stimulation relative to neural events, degrading closed‑loop performance
Q.94 Which of the following is a typical use case for a ‘micro‑electrocorticography (µECoG)’ array?
Recording deep brain activity from the thalamus
Providing high‑resolution surface recordings for BCI control in motor cortex
Stimulating the spinal cord for gait restoration
Measuring blood oxygen levels
Explanation - µECoG arrays sit on the cortical surface, offering higher spatial resolution than standard ECoG, ideal for motor BCIs.
Correct answer is: Providing high‑resolution surface recordings for BCI control in motor cortex
Q.95 What is the main advantage of using ‘current steering’ in a multi‑electrode stimulation array?
It reduces the power consumption of the device
It allows shaping the electric field to target specific neural populations while avoiding others
It increases the overall stimulation amplitude
It eliminates the need for a ground electrode
Explanation - Current steering adjusts the relative amplitudes across electrodes to focus the stimulation field, improving selectivity.
Correct answer is: It allows shaping the electric field to target specific neural populations while avoiding others
Q.96 Which safety concern is specifically addressed by limiting the ‘maximum pulse amplitude’ in neural stimulation protocols?
Preventing electrode corrosion
Avoiding activation of off‑target brain regions
Minimizing the risk of electrochemical damage and tissue injury
Reducing the size of the implant
Explanation - Higher amplitudes increase charge per phase, potentially exceeding safe charge density limits and causing damage.
Correct answer is: Minimizing the risk of electrochemical damage and tissue injury
Q.97 Which of the following best characterizes the role of ‘machine learning’ in modern neural interfaces?
Generating electrical currents for stimulation
Decoding complex neural patterns to predict user intent or disease states
Fabricating electrode arrays
Charging the implant’s battery
Explanation - Machine learning algorithms can interpret high‑dimensional neural data for BCI control or diagnostics.
Correct answer is: Decoding complex neural patterns to predict user intent or disease states
Q.98 What is a typical consequence of ‘over‑driving’ a stimulation electrode beyond its safe charge injection limit?
Improved stimulation selectivity
Electrode corrosion and possible tissue necrosis
Reduced power consumption
Increased battery life
Explanation - Excessive charge leads to irreversible electrochemical reactions, damaging both the electrode and surrounding tissue.
Correct answer is: Electrode corrosion and possible tissue necrosis
Q.99 Which neural interface technology uses a thin, flexible polymer film with embedded metal traces to record from the cortical surface?
Silicon Utah array
Polyimide micro‑ECoG sheet
Deep brain stimulator lead
Cuff electrode
Explanation - Polyimide substrates are flexible, enabling conformal contact with cortical folds for high‑resolution recordings.
Correct answer is: Polyimide micro‑ECoG sheet
Q.100 In the context of neural stimulation, what does ‘frequency modulation’ (FM) refer to?
Changing the amplitude of the stimulation pulse over time
Varying the pulse frequency within a stimulation train to encode information
Altering the electrode material during stimulation
Switching between AC and DC stimulation
Explanation - FM can be used to convey different stimulation patterns or therapeutic effects by changing the inter‑pulse interval.
Correct answer is: Varying the pulse frequency within a stimulation train to encode information
Q.101 Which of the following is a key factor limiting the bandwidth of wireless data transmission from an implanted neural recorder?
Electrode impedance
Battery voltage
Tissue attenuation of radiofrequency signals
Stimulation pulse shape
Explanation - Biological tissue absorbs RF energy, reducing the achievable data rate for wireless telemetry.
Correct answer is: Tissue attenuation of radiofrequency signals
Q.102 What is the purpose of ‘synchronization pulses’ in a multi‑channel neural recording system?
To calibrate electrode impedance
To align timing across channels for accurate reconstruction of neural events
To increase the stimulation current
To power the recording amplifiers
Explanation - Synchronization ensures that data from different channels can be combined accurately in time.
Correct answer is: To align timing across channels for accurate reconstruction of neural events
Q.103 Which of the following best describes the ‘charge‑balanced biphasic pulse’ commonly used in neural stimulation?
Two pulses of opposite polarity with equal area (charge) to avoid net DC
A single high‑voltage pulse followed by a low‑voltage rest period
A pulse train with random polarity
A pulse with gradually increasing amplitude
Explanation - Charge‑balanced biphasic pulses prevent net charge buildup, reducing risk of electrochemical damage.
Correct answer is: Two pulses of opposite polarity with equal area (charge) to avoid net DC
Q.104 Which of the following is an advantage of using a ‘digital’ (instead of analog) stimulation waveform generator?
Higher power consumption
Precise control over pulse parameters and easy re‑programming
Inability to generate biphasic pulses
Reduced ability to interface with microcontrollers
Explanation - Digital generators allow fine‑grained, repeatable control of stimulation parameters via software.
Correct answer is: Precise control over pulse parameters and easy re‑programming
Q.105 What is the primary reason for using ‘high‑Z’ (high‑impedance) electrodes for recording single‑unit activity?
They allow larger currents to pass
They improve signal‑to‑noise ratio for small extracellular spikes
They reduce the need for amplification
They simplify the surgical implantation
Explanation - High‑impedance electrodes have smaller surface area, increasing voltage generated by a single neuron’s spike.
Correct answer is: They improve signal‑to‑noise ratio for small extracellular spikes
Q.106 Which of the following neural interface modalities can directly measure neurotransmitter concentrations in real time?
Fast‑scan cyclic voltammetry (FSCV) microsensors
Standard EEG electrodes
Surface EMG electrodes
Optogenetic probes
Explanation - FSCV uses rapid voltage sweeps to detect electroactive neurotransmitters like dopamine.
Correct answer is: Fast‑scan cyclic voltammetry (FSCV) microsensors
Q.107 Which of the following best defines ‘neuroprosthetic embodiment’?
The process of physically attaching a prosthetic limb to bone
The subjective feeling that a neural prosthesis is part of one’s own body
The surgical technique used to implant electrodes
The method of charging the prosthetic device
Explanation - Embodiment refers to the user’s sense of ownership over the artificial limb or device, important for functional integration.
Correct answer is: The subjective feeling that a neural prosthesis is part of one’s own body
Q.108 Which of the following is a key challenge when designing neural interfaces for pediatric patients?
Higher bone density
Rapid growth requiring adaptable implant designs
Reduced neural activity
Increased blood flow to the brain
Explanation - Children’s skulls and brain structures change over time, demanding flexible or replaceable interface solutions.
Correct answer is: Rapid growth requiring adaptable implant designs
Q.109 What does the term ‘electroencephalographic (EEG) alpha rhythm’ refer to?
High‑frequency spikes (>100 Hz)
A 8‑13 Hz oscillation associated with relaxed wakefulness
A constant DC offset in recordings
A type of muscle artifact
Explanation - The alpha band is prominent when eyes are closed and the subject is relaxed.
Correct answer is: A 8‑13 Hz oscillation associated with relaxed wakefulness
Q.110 Which of the following is a primary advantage of using ‘ultrasonic power transfer’ for deep brain implants?
Higher efficiency through bone compared to RF
No need for any external hardware
Ability to transmit data at gigabit speeds
It eliminates the need for an internal battery
Explanation - Ultrasound penetrates bone more effectively than RF, delivering more power to deep implants.
Correct answer is: Higher efficiency through bone compared to RF
Q.111 Which of the following best explains why ‘cortical stimulation’ can evoke motor responses?
It directly activates spinal motor neurons
It excites corticospinal tract fibers projecting from the motor cortex
It changes blood flow in the motor cortex
It releases neurotransmitters into the bloodstream
Explanation - Stimulation of motor cortex neurons triggers downstream pathways that produce muscle activation.
Correct answer is: It excites corticospinal tract fibers projecting from the motor cortex
Q.112 What is the main purpose of implementing ‘adaptive stimulation’ algorithms in DBS systems?
To keep the stimulation parameters constant regardless of symptom changes
To modify stimulation parameters in real time based on sensed neural activity, improving efficacy and reducing side effects
To increase the battery size
To enable the device to function without any programming
Explanation - Adaptive DBS uses feedback signals (e.g., LFPs) to automatically adjust stimulation, optimizing therapeutic outcomes.
Correct answer is: To modify stimulation parameters in real time based on sensed neural activity, improving efficacy and reducing side effects
Q.113 Which of the following is an example of a ‘sensory substitution’ neural interface?
A visual prosthesis that converts camera images into electrical stimulation of the visual cortex
A cochlear implant that restores hearing
A pacemaker that regulates heart rhythm
A deep brain stimulator for Parkinson’s disease
Explanation - Sensory substitution replaces one sensory modality with another, such as vision with electrical patterns.
Correct answer is: A visual prosthesis that converts camera images into electrical stimulation of the visual cortex
Q.114 Which neural interface component typically defines the ‘spatial resolution’ of recorded signals?
Battery capacity
Electrode size and inter‑electrode spacing
Wireless transmission frequency
Stimulation pulse width
Explanation - Smaller electrodes placed closer together capture more localized neural activity, increasing spatial resolution.
Correct answer is: Electrode size and inter‑electrode spacing
Q.115 What is the typical effect of increasing the ‘pulse frequency’ of a motor cortex stimulation while keeping amplitude constant?
Decreased muscle force
Increased muscle fatigue and higher force output up to a point
No change in motor output
Immediate tissue damage
Explanation - Higher frequencies can summate to produce stronger contractions but also lead to faster fatigue.
Correct answer is: Increased muscle fatigue and higher force output up to a point