Auditory Evoked Potentials (AEPs)
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Questions and Answers

Which category of auditory evoked potentials (AEPs) includes both the N1 – P2 complex and P300?

  • Exogenous potentials
  • Brainstem AEPs
  • Short latency responses
  • Cortical AEPs (correct)

What is primarily reflected by the latency epoch of an AEP?

  • The subject's attention level
  • The anatomical structures of the auditory system
  • The speed of stimulus presentation
  • The level of the auditory system involved (correct)

Which potential is categorized as transient?

  • ABR (correct)
  • MLR
  • P300
  • Cochlear microphonics

Which response relies predominantly on the physical features of the stimulus?

<p>Exogenous potentials (C)</p> Signup and view all the answers

What is the origin of the first peak in an Auditory Brainstem Response (ABR)?

<p>Auditory nerve (AN) (A)</p> Signup and view all the answers

Which of the following is an example of a sustained potential?

<p>EcochG responses (A)</p> Signup and view all the answers

What characteristic distinguishes endogenous potentials from exogenous potentials?

<p>Responsiveness to patient consciousness (D)</p> Signup and view all the answers

Which auditory evoked potential is typically used in an oddball paradigm?

<p>P300 (B)</p> Signup and view all the answers

What term is used to refer to the electrical responses of the nervous system elicited by a stimulus?

<p>Evoked potentials (B)</p> Signup and view all the answers

Which of the following is NOT an advantage of using Auditory Evoked Potentials (AEPs)?

<p>They are invasive. (C)</p> Signup and view all the answers

What is the latency epoch for Early or Short Latency Responses (SLR)?

<p>10-15 ms (C)</p> Signup and view all the answers

Which component is most prominent in the Middle Latency Response (MLR)?

<p>40Hz steady state potential (SSP) (B)</p> Signup and view all the answers

How are Auditory Evoked Potentials (AEPs) primarily classified?

<p>Latency epoch (A)</p> Signup and view all the answers

What is the range of latency for Long Latency Responses (LLR)?

<p>50-80 ms (D)</p> Signup and view all the answers

Which auditory evoked potential occurs within the 0-10 ms range?

<p>ABR (D)</p> Signup and view all the answers

Which of the following classifications of AEPs is characterized by components generated beyond 80 ms post stimulus?

<p>Long latency response (C)</p> Signup and view all the answers

Which electrode positions are used for single channel recordings in the 10-20 system?

<p>Cz, A1/M1, and Fpz (A)</p> Signup and view all the answers

What is the primary function of preamplifiers in the AEP recording system?

<p>To amplify low amplitude signals (A)</p> Signup and view all the answers

What is indicated by excessive activity in the waveform display during AEP recording?

<p>External electrical artifacts are present (C)</p> Signup and view all the answers

How much amplification is typically provided by the accompanying amplifier and preamplifier for AEP signals?

<p>100,000 times (B)</p> Signup and view all the answers

What role does the ground electrode play during AEP recordings?

<p>It acts as a reference point for recordings (A)</p> Signup and view all the answers

What characterizes near field recordings in AEPs?

<p>They involve electrodes positioned close to or on the neural generators. (B)</p> Signup and view all the answers

Which of the following describes far field recordings in AEPs?

<p>They have a larger distance between electrodes and response generators. (C)</p> Signup and view all the answers

What is the primary purpose of the stimulus generator in AEP instrumentation?

<p>To produce stimuli that elicit evoked potentials. (A)</p> Signup and view all the answers

What is a key feature of the clicks used in AEP testing?

<p>They provide maximal stimulation primarily within the 2000Hz to 4000Hz range. (D)</p> Signup and view all the answers

What equipment is notably recommended for acquiring AEPs?

<p>Insert earphones like ER 3A. (C)</p> Signup and view all the answers

What essentially constitutes the recording system in AEP instrumentation?

<p>A combination of electrodes, amplifiers, and signal processing components. (B)</p> Signup and view all the answers

What is a significant challenge when using AEPs to estimate hearing sensitivity?

<p>The requirement for specific adjustment of pulse frequency, duration, and rise/fall times. (D)</p> Signup and view all the answers

Which of the following components is NOT typically part of AEP instrumentation?

<p>Noise canceling features (B)</p> Signup and view all the answers

What is one advantage of insert receivers in audiometric tests?

<p>They help to reduce signal crossover to the non-test ear. (B)</p> Signup and view all the answers

Which is a common disadvantage of supra aural earphones?

<p>They may create ear canal collapse. (A)</p> Signup and view all the answers

What purpose does a trigger serve in auditory evoked potentials?

<p>It marks the beginning of the recording epoch. (D)</p> Signup and view all the answers

What is one of the primary uses of bone vibrators in audiometric testing?

<p>For threshold estimation of hearing sensitivity. (B)</p> Signup and view all the answers

Which of the following is true regarding electrode placement for AEP recordings?

<p>One electrode is positioned at the vertex and others at the mastoids. (C)</p> Signup and view all the answers

Which of the following characteristics is more reliable for insert receivers compared to supra aural earphones?

<p>Temporal and spectral characteristics. (D)</p> Signup and view all the answers

Why is it important to ensure precise electrode placement in AEP recordings?

<p>To achieve accurate interaural comparisons. (D)</p> Signup and view all the answers

What major disadvantage do insert receivers have compared to supra aural earphones?

<p>They can be difficult to insert and remove. (B)</p> Signup and view all the answers

Flashcards

Auditory Evoked Potentials (AEPs)

Electrical signals in the nervous system triggered by sound, recorded using electrodes on the head.

Early/Short Latency Response (SLR)

AEP components within the first 10-15 milliseconds after a sound.

Middle Latency Response (MLR)

AEP components occurring between 10-50 milliseconds after a sound.

Long Latency Response (LLR)

AEP components appearing after 50-80 milliseconds following a sound stimulus.

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Latency Epoch

Time period after stimulus onset when the AEP response occurs.

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Electrode Placement

Position of electrodes on the head during AEP recording.

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Stimulus-Response Relationship

Connection between the sound stimulus and the resulting AEP.

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AEP Advantages

Evaluates auditory system integrity, predicts hearing capabilities, and generally a non-invasive measurement.

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Short Latency Responses (SLR)

AEPs originating from the auditory periphery and brainstem.

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Transient Potential

AEPs evoked by short, rapid stimuli.

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Sustained Potential

AEPs evoked by prolonged stimuli.

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Exogenous Potential

AEP dependent on stimulus's physical features, not on patient's attention.

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Endogenous Potential

AEP based on stimulus context and meaning, depending on patient's attention.

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P300

An example of an endogenous potential, often linked to an oddball paradigm.

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Cz

The electrode position at the vertex of the head, according to the 10-20 system.

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Vertex Electrode

Electrode placed on the top of the head, used in AEP recordings.

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Single-Channel Recordings

AEP recordings that use 3 electrodes: vertex (Cz), one ear (A1/M1), and the other ear (Fpz) as ground.

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Preamplifier's Role

Amplifies the weak AEP signals before they reach the main amplifier, increasing their strength.

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Artifact Reduction

The ability to identify and discard recordings affected by movement or external electrical noise.

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AEP Recording Types

AEPs are categorized by electrode placement relative to response generators.

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Near-field Recordings

Electrodes placed near or on the neural generators; electrode placement greatly affects the shape of the response.

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Far-field Recordings

Electrodes are far from neural generators; electrode placement has less impact.

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AEP Instrumentation

AEPs use computer-based systems, divided into stimulus and recording systems.

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Click Stimulus

A brief, rapid stimulus used in AEP, mostly in hearing sensitivity tests.

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Stimulus Generator

Part of AEP systems that creates the stimuli, like clicks or tones.

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Insert Earphones

Used in AEP recordings, typically ER 3A, preferred for clarity of the response.

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Hearing Sensitivity Tests

Tests using AEPs, that measure the ear sensitivity by presenting tone bursts at different frequencies and durations.

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Insert Receivers

Earphones that fit directly into the ear canal, providing a tight seal and reducing outside noise.

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Interaural Attenuation

The reduction of sound crossing over from one ear to the other when wearing earphones.

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Supra-Aural Earphones

Earphones that sit over the ears, covering the pinna but not entering the ear canal.

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Pinna

The visible part of the outer ear, also called the auricle.

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Bone Vibrators

Devices that transmit sound vibrations through the skull to the inner ear, bypassing the outer and middle ear.

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Trigger Pulse

A signal sent to the recording device indicating the start of the stimulus, allowing captured data to be time-aligned with the stimulus onset.

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Vertex

The highest point on the top of the head, used as a reference point for electrode placement.

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Study Notes

Auditory Evoked Potentials (AEPs)

  • AEPs are electrical signals produced by the nervous system in response to a stimulus, typically sound.
  • The signals are picked up by electrodes placed on the head and displayed on a recording device (e.g., EEG).
  • A change in nervous system activity, caused by the stimulus, results in changes in the electrical signals detected by the electrodes.
  • These responses to a stimulus are called evoked potentials.
  • When the stimulus is sound, they're called Auditory Evoked Potentials (AEPs).

Advantages of AEPs

  • Used to evaluate the integrity of the auditory system.
  • Used to gather information about hearing.
  • Generally non-invasive, measured externally using electrodes on the skin.

Classification of AEPs

  • Classification approaches vary but aren't standardized.
  • AEPs are generally categorized based on these aspects:
    • Latency epochs (time from stimulus onset)
    • Anatomic origins (brainstem or cortical)
    • Stimulus-response relationships (transient or sustained, endogenous or exogenous)
    • Electrode placement (near-field or far-field)

AEPs based on Latency Epoch

  • Latency epoch is the time domain within which a response occurs after stimulus onset.
  • AEPs are divided into three categories:
    • Early/Short Latency Responses (SLRs): Occur within 10-15 milliseconds after stimulus onset. Examples include ECochG, ABR, SN10, and FFR.
    • Middle Latency Responses (MLRs): Occur between 10-50 milliseconds after stimulus onset; prominent feature is 40Hz steady-state potential.
    • Long Latency Responses (LLRs): Occur beyond 50-80 milliseconds after stimulus onset, often referred to as slow or late responses; examples include N1-P2 complex and P300.

AEPs based on Anatomic Origin

  • AEPs are categorized as either brainstem or cortical based on their origin.
  • Short latency responses originate in the brainstem
  • Long latency responses originate in the cortex
  • Note that some responses, like the ABR's initial peak, originated from structures not consistently categorized as brainstem.

AEPs Based on Stimulus-Response Relationship

  • AEPs are further categorized by whether their responses are:
    • Transient or Sustained: based on the rise and fall time/pattern of the stimulus and response
    • Endogenous or Exogenous: Exogenous responses are influenced by the physical characteristics of the stimulus. Endogenous responses aren't dependent on the stimulus's physical characteristics, but rather the patient's perception and arousal of that stimulus.

AEPs based on Electrode Placement

  • AEP classification is also based on the location of recording electrodes relative to the site of the response generators.
  • Two categories exist:
    • Near-field recordings: Obtained when electrodes are placed near or on the neural generators. Slight changes in electrode placement significantly affect resultant wave morphology. Example: intra-operative recordings.
    • Far-field recordings: Large distance between electrodes and generators. Site location has less of an impact on resulting morphology. Examples common scalp-level AEPs (ABR, MLR, LLR, etc.).

Instrumentation of AEPS

  • Sophisticated computer-based systems are used for clinical AEP recordings.
  • AEPs use a "stimulus system" and a "recording system."
  • The stimulus system includes:
    • Stimulus generator (clicks, tones)
    • Attenuator (control stimulus intensity)
    • Transducers (earphones, bone vibrators)
  • The recording system includes:
    • Electrodes (surface electrodes on scalp)
    • Amplifiers (boost signal strength)
    • Filters (remove unwanted noise)
    • Averager (reduce background noise)
    • Display unit (waveform visualization)
    • Response processing unit (processing and saving the data)

Transducers in AEPs

  • Earphones: Insert earphones (ER-3A) are often used due to reduced stimulus artifacts and better isolation of the signal, despite the potential for aural discomfort and risk of canal collapse. Supra-aural and bone conduction transducers are also used.

Triggering in AEPS

  • A trigger pulse triggers the recording system to begin recording at the stimulus onset.
  • It is used to isolate the signal from background noise.

Electrodes in AEPS

  • Electrodes are placed on the scalp to capture the AEP signal.
  • Common montages used include two or four electrodes.
  • Specific electrode placements and configurations are important for properly capturing and interpreting the AEP signal.

Amplifiers and Preamplifiers, Display and Print, AEP

  • Preamplifiers increase the strength of the evoked signal, necessary to overcome background noise.
  • These waveforms can be viewed or averaged; artifacts are typically identifiable and discarded.
  • Printed recordings offer a permanent record for later analysis.

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Description

This quiz explores Auditory Evoked Potentials (AEPs), the electrical signals produced by our auditory system in response to sound stimuli. Learn about their significance in assessing hearing integrity, their non-invasive measurement methods, and various classification approaches. Test your knowledge on the functioning and application of AEPs in auditory assessments.

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