# Evoked Potential Practice Exam

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Review questions for the ABRET EP examination

• 1.

### The nucleus of an atom contains

• A.

Anions

• B.

Electrons

• C.

Protons

• D.

Cations

C. Protons
Explanation
The nucleus of an atom contains protons. Protons are positively charged particles found in the nucleus of an atom. They have a mass of approximately 1 atomic mass unit. Electrons, on the other hand, are negatively charged particles that orbit around the nucleus. Anions and cations are charged ions that result from the gain or loss of electrons, but they are not found in the nucleus itself.

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• 2.

### If a 4 ohm resistor and a 2 ohm resistor are wired in series across a 6 volt battery, what is the curernt across each resistor?

• A.

1 amp

• B.

2 amps

• C.

1.5 amps across the larger adn 3 amps across the smaller

• D.

4 amps across the larger and 1.5 amps across the smaller

A. 1 amp
Explanation
When resistors are connected in series, the total resistance is the sum of the individual resistances. In this case, the total resistance is 4 ohms + 2 ohms = 6 ohms. According to Ohm's Law (V = I * R), the current (I) is equal to the voltage (V) divided by the resistance (R). Therefore, the current across each resistor is 6 volts / 6 ohms = 1 amp.

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• 3.

### If the volrage in a circuit is 400 volts and the resistance is 50 ohms, the current equals

• A.

8 ohms

• B.

20,000 ohms

• C.

8 amperes

• D.

20,000 amperes

C. 8 amperes
Explanation
The current in a circuit can be calculated using Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the voltage is given as 400 volts and the resistance is given as 50 ohms. By dividing 400 volts by 50 ohms, we get a current of 8 amperes.

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• 4.

### Somatosensory Evoked Potential

• A.

Dorsal root

• B.

Ventral root

• C.

Choroid plexus

• D.

Anterior horn cell

A. Dorsal root
Explanation
The dorsal root is the correct answer because it is a part of the somatosensory system. It is responsible for carrying sensory information from the peripheral nerves to the spinal cord. The dorsal root contains sensory nerve fibers that transmit signals such as touch, pain, and temperature from the body to the central nervous system. This information is then processed and interpreted by the brain, allowing us to perceive and respond to sensory stimuli.

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• 5.

### Afferent Nerves

• A.

Control ability to speak

• B.

Control emotional responses

• C.

Conduct impulses toward the central nervous system

• D.

Conduct impules away from the central nervous system

C. Conduct impulses toward the central nervous system
Explanation
Afferent nerves are responsible for conducting impulses toward the central nervous system. These nerves transmit sensory information from the body's periphery, such as touch, temperature, and pain, to the brain and spinal cord. This allows the central nervous system to receive and process sensory input, which is essential for various functions, including speech and emotional responses.

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• 6.

### Which of the folowing is involved in the visual system?

• A.

Lateral geniculate

• B.

Dorsal column

• C.

Pyramidal tract

• D.

Medial Lemniscus

A. Lateral geniculate
Explanation
The correct answer is "Lateral geniculate." The visual system involves several structures, including the lateral geniculate nucleus (LGN). The LGN is a part of the thalamus and plays a crucial role in relaying visual information from the optic nerve to the visual cortex in the brain. It receives input from the retina and sends visual signals to the primary visual cortex for further processing. The dorsal column, pyramidal tract, and medial lemniscus are not directly involved in the visual system, making them incorrect options.

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• 7.

### Blind Spot

• A.

Lens

• B.

Fovea

• C.

Macula

• D.

Optic Disc

D. Optic Disc
Explanation
The optic disc is the correct answer because it is a part of the eye that does not contain any photoreceptor cells, making it a blind spot in our visual field. It is the area where the optic nerve exits the eye and connects to the brain, transmitting visual information. This area lacks the ability to detect light, resulting in a blind spot in our vision. The other options, such as lens, fovea, and macula, are all important structures in the eye but do not represent the blind spot.

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• 8.

### Posterior Fossa

• A.

Knee

• B.

Brain stem

• C.

Cauda equina

• D.

Temporal lobe

B. Brain stem
Explanation
The brain stem is the correct answer because the posterior fossa is a part of the skull that houses the brain stem. The brain stem is responsible for many vital functions such as controlling breathing, heart rate, and blood pressure. It also serves as a pathway for nerve fibers traveling between the brain and spinal cord. The other options, knee, cauda equina, and temporal lobe, are not located in the posterior fossa.

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• 9.

### Which of the following cranial nerves is purely sensory?

• A.

III

• B.

VI

• C.

VIII

• D.

X

C. VIII
Explanation
Cranial nerve VIII, also known as the vestibulocochlear nerve, is purely sensory. It is responsible for transmitting auditory and vestibular information from the inner ear to the brain. This nerve plays a crucial role in hearing and balance, making it purely sensory in function. Cranial nerves III, VI, and X have both sensory and motor functions, making them not purely sensory.

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• 10.

### The decussation of the pyramids take place at what level?

• A.

Pons

• B.

Cervial medullary junction

• C.

Cerebellum

• D.

Diencephalon

B. Cervial medullary junction
Explanation
The decussation of the pyramids refers to the crossing over of nerve fibers in the medulla oblongata, which is located at the cervial medullary junction. This crossing over is important for the coordination of motor functions in the body. The other options, such as the pons, cerebellum, and diencephalon, are not specifically associated with the decussation of the pyramids.

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• 11.

### Resting Membrane Potential

• A.

-7uV

• B.

-70uV

• C.

-7mV

• D.

-70mV

D. -70mV
Explanation
The resting membrane potential refers to the electrical potential difference across the cell membrane when the cell is at rest. This potential difference is maintained by the active transport of ions, particularly sodium and potassium ions, across the membrane. The value of -70mV indicates that the inside of the cell is negatively charged compared to the outside. This negative charge is essential for various cellular processes, including the transmission of nerve impulses and the regulation of ion channels.

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• 12.

### Which of the following most likely results in increased firing of a neuron?

• A.

Inhibitory presynaptic potential

• B.

Inhibitory postsynaptic potential

• C.

Excitatory postsynaptic potential

• D.

Hyperpolarization of resting membrane potential

C. Excitatory postsynaptic potential
Explanation
An excitatory postsynaptic potential (EPSP) is a temporary depolarization of the postsynaptic membrane that brings the neuron closer to its threshold and increases the likelihood of firing an action potential. This occurs when neurotransmitters bind to receptors on the postsynaptic membrane, causing ion channels to open and allowing positive ions to enter the cell. As a result, the membrane potential becomes less negative, making it easier for the neuron to reach the threshold and generate an action potential.

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• 13.

### Amplitude of an evoked potential depends on which of the following physiiological actions in a sensory pathway?

• A.

The velocity of the neural impulses

• B.

The synchrony with which neural impulses travel

• C.

The number of normal neural generators sequentially excited

• D.

The number of cortical or subcortical generators simultaneously activated.

D. The number of cortical or subcortical generators simultaneously activated.
Explanation
The amplitude of an evoked potential depends on the number of cortical or subcortical generators simultaneously activated. This means that the more generators that are activated at the same time, the larger the amplitude of the evoked potential will be. The other options, such as the velocity of neural impulses or the synchrony of neural impulses, do not directly affect the amplitude of the evoked potential. The number of normal neural generators sequentially excited may have an impact, but it is not the primary factor determining the amplitude.

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• 14.

### All components of brainstem auditory evoked potential waveforms reach adult configuratiion by what age?

• A.

1-2 months

• B.

3-6 months

• C.

1-2 years

• D.

3-4 years

B. 3-6 months
Explanation
The brainstem auditory evoked potential (BAEP) waveforms refer to the electrical activity generated by the auditory nerve and brainstem in response to sound. The given answer, 3-6 months, suggests that all components of the BAEP waveforms reach their adult configuration by this age. This means that the auditory system in infants develops and matures during the first few months of life, and by 3-6 months, it resembles the patterns seen in adults. This is an important milestone in auditory development as it indicates the establishment of normal auditory functioning.

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• 15.

### In what age group do early symptoms of multiple sclerosis usually occur?

• A.

Under 10 years

• B.

15-40 years

• C.

50-60 years

• D.

Over5 70 years

B. 15-40 years
Explanation
Early symptoms of multiple sclerosis usually occur in the age group of 15-40 years. Multiple sclerosis is a chronic autoimmune disease that affects the central nervous system. It is most commonly diagnosed in young adults, with symptoms typically appearing between the ages of 15 and 40. These early symptoms can vary widely but often include fatigue, difficulty walking, numbness or tingling in the limbs, muscle weakness, and problems with coordination and balance.

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• 16.

### Paresthesia

• A.

Fainting

• B.

Tingling

• C.

Weakness

• D.

Dizziness

B. Tingling
Explanation
Tingling is a sensation often described as pins and needles or a prickling feeling. It is commonly associated with paresthesia, a condition characterized by abnormal sensations in the body. While fainting, weakness, and dizziness can also be symptoms of various medical conditions, tingling specifically refers to the abnormal sensation of pins and needles, making it the correct answer in this context.

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• 17.

### A patient with a left homonymous hemianopsia most likely has a lesion of the

• A.

Right midbrain

• B.

Right optic tract

• C.

Left temporal lobe

• D.

Left occipital cortex

B. Right optic tract
Explanation
A patient with a left homonymous hemianopsia, which is a loss of vision in the left visual field of both eyes, most likely has a lesion of the right optic tract. The optic tracts carry visual information from the optic chiasm to the brain. Since the left visual field is processed in the right side of the brain, a lesion in the right optic tract would disrupt the transmission of visual information from the left visual field to the right side of the brain, resulting in a loss of vision in the left visual field.

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• 18.

### Which of the following is a partial paralysis of the lower extremities?

• A.

Hemiplegia

• B.

Hemiparesis

• C.

Paraplegia

• D.

Paraparesis

D. Paraparesis
Explanation
Paraparesis refers to a partial paralysis of the lower extremities. It is characterized by weakness or loss of voluntary movement in the legs, but not a complete loss of function. This condition can be caused by various factors such as spinal cord injuries, nerve damage, or diseases affecting the motor system. Unlike paraplegia, which is a complete paralysis of the lower body, paraparesis allows for some degree of movement and sensation in the affected areas.

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• 19.

### Compared to electrode impedance, the input impedance of the amplifier should be

• A.

Equal

• B.

Lower

• C.

Higher

• D.

Variable

C. Higher
Explanation
The input impedance of the amplifier should be higher compared to electrode impedance because a higher input impedance ensures that the amplifier does not load or disturb the signal coming from the electrodes. It allows for better signal transfer and minimizes any distortion or loss of signal during amplification. A higher input impedance also helps in maintaining the accuracy and fidelity of the amplified signal.

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• 20.

### What is the typical MINIMUM common mode rejction ratio of in-phase signals recommended for evoked potential instruments?

• A.

1,000:1

• B.

5,000:1

• C.

10,000:1

• D.

50,000:1

C. 10,000:1
Explanation
The typical MINIMUM common mode rejection ratio of in-phase signals recommended for evoked potential instruments is 10,000:1. This means that the instrument is capable of rejecting common mode noise by a factor of 10,000. This high rejection ratio is important in evoked potential measurements as it helps to minimize interference from external sources and improve the accuracy of the recorded signals.

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• 21.

### Which of the following is the usual polarity convention for recording a brainstem auditory evoked potential?

• A.

Positivity at the ear produces an upward deflection

• B.

Negativity at the ear produces a downward deflection

• C.

Negativity at the vertex produces an upward deflection

• D.

Positivity at the vertex produces a downward deflection

D. Positivity at the vertex produces a downward deflection
Explanation
The correct answer states that positivity at the vertex produces a downward deflection. This means that when there is a positive electrical signal at the vertex (the top of the head), it will result in a downward deflection on the recording. This polarity convention is commonly used when recording brainstem auditory evoked potentials, where changes in electrical activity in response to auditory stimuli are measured.

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• 22.

### Using an amplification factor of 500,000, a 1uV brainstem auditory evoked potential waveform will be amplified to

• A.

0.05 v

• B.

0.50 v

• C.

5.00 v

• D.

50.00 v

B. 0.50 v
Explanation
An amplification factor of 500,000 means that the input signal is multiplied by 500,000. Therefore, a 1uV brainstem auditory evoked potential waveform will be amplified to 500,000 * 1uV = 500,000uV = 0.50V.

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• 23.

### When recording evoked potentials, which of the following filters does NOT produce a phase shift?

• A.

60Hz

• B.

Notch

• C.

Digital

• D.

Passive RC

C. Digital
Explanation
Digital filters do not produce a phase shift. Unlike analog filters such as the 60Hz, notch, and passive RC filters, which can introduce a phase shift in the recorded evoked potentials, digital filters process the signal in the digital domain and do not alter the phase of the signal. Therefore, when recording evoked potentials, digital filters are preferred over analog filters to avoid any phase distortion in the recorded data.

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• 24.

### Which of the following would best enhance resolution of evoked potential waveforms?

• A.

Decrease sensitivity

• B.

Decrease filter band width

• C.

Increase stimulation rate

• D.

Increase number of averaged stimuli

D. Increase number of averaged stimuli
Explanation
Increasing the number of averaged stimuli would best enhance resolution of evoked potential waveforms. Averaging multiple stimuli helps to reduce random noise and improve the signal-to-noise ratio, resulting in a clearer and more accurate representation of the evoked potential waveform. By increasing the number of stimuli that are averaged together, the overall signal strength increases, making it easier to identify and analyze the waveform. This technique is commonly used in neurophysiology and can be particularly useful when studying weak or subtle evoked potentials.

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• 25.

### Positive Delay

• A.

Averaging starts before stimulus onset

• B.

Averaging starts after stimulus onset

• C.

Averaging and stimulus onset occur simultaneously

• D.

Averaging and stimulus onset are independently triggered

B. Averaging starts after stimulus onset
Explanation
The correct answer is "Averaging starts after stimulus onset" because in order to average the responses to a stimulus, the averaging process needs to begin after the stimulus has been presented. If the averaging were to start before the stimulus onset, it would include unrelated or baseline activity, which would not accurately reflect the response to the stimulus. Therefore, it is necessary for the averaging to begin after the stimulus onset to capture the specific response to the stimulus.

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• 26.

### If an evoked potential has a voltage of 10uV and the associated noise has a voltage of 50uV, what is the signal to noise ratio after 100 averaged responses?

• A.

1:1

• B.

1:2

• C.

2:1

• D.

5:1

C. 2:1
D. 5:1
Explanation
The signal to noise ratio is a measure of the strength of the desired signal compared to the background noise. In this case, the signal has a voltage of 10uV and the noise has a voltage of 50uV. To calculate the signal to noise ratio after 100 averaged responses, we need to consider the effect of averaging on the noise. Averaging multiple responses can help reduce the effect of random noise, resulting in a higher signal to noise ratio. Therefore, after 100 averaged responses, the signal to noise ratio would be improved, resulting in a ratio of either 2:1 or 5:1.

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• 27.

### Which of the following results from averaging an evoked potential?

• A.

Noise is reduced

• B.

Random activity summates

• C.

Signal amplitude decreases

• D.

Stimulus artifact appears smaller

A. Noise is reduced
Explanation
Averaging an evoked potential involves combining multiple trials of the same stimulus to reduce random variations and enhance the underlying signal. By averaging, the random noise that is present in each individual trial gets cancelled out, resulting in a reduction of noise. This allows for a clearer and more reliable representation of the evoked potential, making it easier to detect and analyze the true signal of interest.

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• 28.

### Which of the folowing is the most sensitive setting?

• A.

10 millivolts per division

• B.

20 millivolts per division

• C.

10 microvolts per division

• D.

20 microvolts per division

C. 10 microvolts per division
Explanation
The most sensitive setting is 10 microvolts per division. This is because microvolts are smaller than millivolts, so a smaller change in voltage can be detected. Therefore, with a setting of 10 microvolts per division, the device will be able to detect and display smaller voltage changes compared to the other options.

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• 29.

### Voltage information is changed into numerical values for averaging by means of

• A.

Analog to analog conversion

• B.

Digital to digital conversion

• C.

Analog to digital conversion

• D.

Digital to analog conversion

C. Analog to digital conversion
Explanation
Analog to digital conversion is the process of converting voltage information, which is an analog signal, into numerical values, which are digital signals. This conversion allows for easier manipulation, storage, and processing of the voltage information. It involves sampling the analog signal at regular intervals and quantizing the sampled values into discrete digital values. This enables the signal to be represented by a series of numbers that can be averaged or processed using digital systems or algorithms.

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• 30.

### What is the approximate amplitude resolution of a 10-bit digitizer witha range of plus or minus 5 uv?

• A.

0.01uV

• B.

0.10uV

• C.

1.00uV

• D.

10.00uV

A. 0.01uV
Explanation
The approximate amplitude resolution of a 10-bit digitizer can be calculated by dividing the total range of the digitizer (plus or minus 5uV) by the number of possible values (2^10). Therefore, the approximate amplitude resolution would be 10uV / 1024 = 0.01uV.

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• 31.

### The recommended amplitude resolution of the analog to digital converter must be a MINIMUM of

• A.

2 bits

• B.

4 bits

• C.

8 bits

• D.

16 bits

C. 8 bits
Explanation
The recommended amplitude resolution of the analog to digital converter must be a minimum of 8 bits because an 8-bit ADC can represent 2^8 = 256 different levels or values. This level of resolution allows for more accurate and precise conversion of analog signals into digital data. With a higher number of bits, the ADC can capture and distinguish smaller changes in the analog signal, resulting in a more faithful representation of the original signal. Therefore, a minimum of 8 bits is necessary for most applications to ensure sufficient resolution and accuracy.

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• 32.

### If the fastest component of a complex waveform is near 100Hz, which of the following is the most appropriate dwell time?

• A.

5 msec

• B.

10 msec

• C.

20 msec

• D.

50 msec

A. 5 msec
Explanation
The fastest component of a complex waveform is near 100Hz, which means that the waveform has a frequency of 100Hz. Dwell time refers to the amount of time spent at each data point in a waveform. In order to accurately capture the fastest component of the waveform, the dwell time should be less than or equal to the period of the waveform. The period of a waveform with a frequency of 100Hz is 1/100 seconds, which is equal to 10 milliseconds. Therefore, the most appropriate dwell time would be 5 milliseconds, as it is less than the period of the waveform.

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• 33.

### Which of the following is the time from the beginning to the end of each evoked potential sweep?

• A.

Rate

• B.

Latency

• C.

Real Time

• D.

Analysis Time

D. Analysis Time
Explanation
The analysis time refers to the duration from the start to the end of each evoked potential sweep. This is the period during which the data is being processed and analyzed. It is different from the other options provided, such as rate, latency, and real time, which do not specifically pertain to the duration of the evoked potential sweep.

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• 34.

### In which of the following is the sampling rate of an averager at least twice the frequency fo the fastest sine wave compoenent in the signal to be resolved?

• A.

Ohm's Law

• B.

Wiener filtering

• C.

Nyquist frequency

• D.

Fourier analysis

C. Nyquist frequency
Explanation
The Nyquist frequency is the highest frequency that can be accurately represented in a digital signal. According to the Nyquist-Shannon sampling theorem, the sampling rate must be at least twice the frequency of the highest frequency component in the signal in order to avoid aliasing and accurately reconstruct the original signal. Therefore, in order for the sampling rate of an averager to be at least twice the frequency of the fastest sine wave component in the signal, the Nyquist frequency concept is relevant.

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• 35.

### Which of the following refers to the phenomenon of fast frequency components of an artifact or signal showing up on an evoked potential at slower frequencies?

• A.

Delay

• B.

Smoothing

• C.

Aliasing

• D.

Blocking

C. Aliasing
Explanation
Aliasing refers to the phenomenon where fast frequency components of an artifact or signal appear as slower frequencies in an evoked potential. This occurs when the sampling rate is too low to accurately capture the high-frequency components, leading to a distorted representation in the slower frequencies.

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• 36.

### If a signal averager samples every millisecond, what is the theoretical maximum frequency resolution?

• A.

100 Hz

• B.

500 Hz

• C.

1000 Hz

• D.

2000 Hz

B. 500 Hz
Explanation
The theoretical maximum frequency resolution is determined by the Nyquist-Shannon sampling theorem, which states that in order to accurately represent a signal, the sampling rate should be at least twice the highest frequency component of the signal. In this case, if the signal averager samples every millisecond, the sampling rate is 1000 samples per second. According to the Nyquist-Shannon theorem, the theoretical maximum frequency resolution would be half of the sampling rate, which is 500 Hz.

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• 37.

### Compared to surface electrodes, needle recording electrodes tend to have

• A.

Higher impedance

• B.

Better high frequency responses

• C.

Less risk of transmitting diseases

• D.

Less distortion of low frequencies

A. Higher impedance
Explanation
Needle recording electrodes tend to have higher impedance compared to surface electrodes. Impedance refers to the opposition of an electrical circuit to the flow of current. Higher impedance means that the electrode has more resistance to the flow of electrical signals. In the case of needle recording electrodes, the higher impedance allows for more precise and accurate recording of electrical activity in the body. This is because higher impedance reduces the interference from surrounding tissues and minimizes signal distortion.

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• 38.

### Which of the following is a key factor in the common mode rejection ratio?

• A.

Electrode length

• B.

Electrode placement

• C.

Far field generators

• D.

Electrode impedance balance

D. Electrode impedance balance
Explanation
The key factor in the common mode rejection ratio is the electrode impedance balance. Common mode rejection ratio (CMRR) is a measure of how effectively a device can reject common mode signals, which are unwanted signals that appear on both input terminals. Electrode impedance balance refers to the equality of impedance between the two electrodes used in a device. A balanced impedance ensures that the device can effectively cancel out common mode signals, resulting in a higher CMRR.

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• 39.

### Using the International 10-20 electrode placements, if the measurement from nasion to inion is 30 cm, what is the distance from Fz to Cz?

• A.

6 cm

• B.

9 cm

• C.

12 cm

• D.

18 cm

A. 6 cm
Explanation
The International 10-20 electrode placement system is a standardized method used to accurately position electrodes on the scalp for EEG recordings. The nasion is the bridge of the nose, and the inion is the external bump at the base of the skull. The distance between these two points is 30 cm. In the 10-20 system, Fz is the electrode placement on the midline of the forehead, and Cz is the electrode placement on the midline of the scalp. Since Fz and Cz are both on the midline, their distance should be half of the nasion to inion measurement. Therefore, the distance from Fz to Cz would be 6 cm.

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• 40.

### For posterior tibial somatosensory evoked potentials, which of the following would be the best ipsilateral location for the ground electrode?

• A.

Arm

• B.

Calf

• C.

Mastoid

• D.

Sole of the foot

B. Calf
Explanation
The calf would be the best ipsilateral location for the ground electrode because it is closer to the posterior tibial nerve, which is the nerve being stimulated in this test. Placing the ground electrode in the calf allows for more accurate measurement of the somatosensory evoked potentials generated by the posterior tibial nerve. The arm, mastoid, and sole of the foot are not as close to the nerve and may not provide as accurate results.

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• 41.

### Smaller surface of stimulating electrodes:

• A.

Higher current density

• B.

Lower current density

• C.

Constant current stimulation

• D.

Constant voltage stimulation

A. Higher current density
Explanation
A smaller surface area of stimulating electrodes results in a higher current density. This is because the same amount of current is being delivered through a smaller area, leading to a higher concentration of current. This can be beneficial in certain applications where a more focused or intense stimulation is desired.

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• 42.

### An electrode recording from Erb's point is placed

• A.

On the shoulder

• B.

2-3 cm above the clavicle

• C.

Over the trapezius muscle

• D.

At the axilla

B. 2-3 cm above the clavicle
Explanation
The correct answer is "2-3 cm above the clavicle." This is the correct placement for an electrode recording from Erb's point. Erb's point is located in the brachial plexus, which is a network of nerves that innervate the upper limb. Placing the electrode 2-3 cm above the clavicle ensures that it is in the correct position to record electrical activity from the brachial plexus and surrounding muscles.

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• 43.

### Accurate electrode placment of CP4 is most critical for simulaton of what nerves?

• A.

Left median

• B.

Right median

• C.

Left tibial

• D.

Right tibial

A. Left median
Explanation
The accurate electrode placement of CP4 is most critical for the simulation of the left median nerves.

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• 44.

### Accuracy of electrode placement is MOST critical for which type of response?

• A.

Near field

• B.

Far field

• C.

Subcortical

• D.

Brainstem

A. Near field
Explanation
The accuracy of electrode placement is most critical for near field responses. Near field responses refer to the electrical activity that is detected close to the site of stimulation or recording. In order to accurately measure and interpret these responses, the electrodes need to be placed precisely and in close proximity to the target area. Any slight deviation in electrode placement can lead to inaccurate recordings and misinterpretation of the results. Therefore, ensuring the accuracy of electrode placement is crucial for obtaining reliable and meaningful near field responses.

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• 45.

### The number of recording channels for full-field VEP should be

• A.

One

• B.

Two

• C.

Three

• D.

Four

D. Four
Explanation
The correct answer is four because full-field VEP (Visual Evoked Potential) is a technique used to measure the electrical activity in the visual cortex of the brain in response to visual stimuli. It requires multiple recording channels to accurately capture the signals from different areas of the brain. Having four recording channels allows for a more comprehensive and detailed analysis of the brain's response to visual stimuli.

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• 46.

### Subdermal electrodes

• A.

Are more susceptible to noise due to high impedance

• B.

Have low impedance due to small contact area

• C.

Require that electrode resistance be measured

• D.

Have long time constants compared to silver electrodes

A. Are more susceptible to noise due to high impedance
Explanation
Subdermal electrodes are placed beneath the skin and have a higher impedance compared to other types of electrodes. This higher impedance makes them more susceptible to noise interference, which can affect the accuracy of the recorded signals. Noise can be caused by various factors such as muscle activity or electromagnetic interference, and the high impedance of subdermal electrodes makes them more prone to picking up these unwanted signals.

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• 47.

### The impedance of cup electrodes is:

• A.

Higher than needle elecrodes because of their size

• B.

Lower than needle electrodes because of metal type

• C.

Higher than needle electordes because of metal type

• D.

Lower than needle electrodes because of their size

D. Lower than needle electrodes because of their size
Explanation
The impedance of cup electrodes is lower than needle electrodes because of their size. Cup electrodes have a larger surface area compared to needle electrodes, which allows for better contact with the skin and reduces the impedance. This larger surface area allows for more efficient electrical signal transmission, resulting in lower impedance.

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• 48.

### The N13 of the median nerve somatosensory evoked potential is generated in the

• A.

Brachial plexus

• B.

Medial lemniscus

• C.

Cervical spinal cord

• D.

Primary somatosensory cortex

C. Cervical spinal cord
Explanation
The N13 of the median nerve somatosensory evoked potential is generated in the cervical spinal cord. This is because the N13 component represents the electrical activity generated when the sensory information from the median nerve reaches the cervical spinal cord. The brachial plexus is responsible for the transmission of the nerve signals from the upper limb to the spinal cord, but it is not where the N13 component is generated. The medial lemniscus is a pathway in the brainstem that carries sensory information to the thalamus, but it is not involved in the generation of the N13 component. The primary somatosensory cortex is responsible for processing sensory information, but it is not where the N13 component is generated.

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• 49.

### Where is the P100 waveform generated?

• A.

Optic nerve

• B.

Broca's area

• C.

Striate cortex

• D.

Lateral geniculate

C. Striate cortex
Explanation
The P100 waveform is generated in the striate cortex. The striate cortex, also known as the primary visual cortex or V1, is located in the occipital lobe of the brain. It is responsible for processing visual information received from the eyes. The P100 waveform refers to a positive deflection in the electroencephalogram (EEG) that occurs approximately 100 milliseconds after the onset of a visual stimulus. This waveform reflects the neural activity in the striate cortex, specifically the processing of early visual information such as basic features and orientation of objects.

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• 50.

### Which of the following is characteristic of alternating click polarity?

• A.

Produces abnormal I-V latencies

• B.

Has no effect on wave I amplitude

• C.

Is recommended for testing premature infants

• D.

Cancels the stimulus artifact

D. Cancels the stimulus artifact
Explanation
Alternating click polarity refers to the technique of reversing the polarity of the stimulus click between consecutive presentations. This method is used to cancel out the stimulus artifact, which is an electrical artifact that occurs when the stimulus is presented. By reversing the polarity, the artifact is effectively eliminated, allowing for more accurate measurement of the auditory evoked potentials. Therefore, the given answer that alternating click polarity cancels the stimulus artifact is correct.

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