Glossary

Acoustic change complex☆

also: ACC

A cortical onset-like response triggered by a change — in frequency, intensity or spectrum — within an ongoing sound. It objectively shows that the auditory system can discriminate that change, making it useful for suprathreshold and aided audibility testing.

See also: Cortical auditory evoked potential, Speech token, Aided cortical assessment

Aided cortical assessment☆

also: HEARLab, aided CAEP, cortical aided testing

Recording cortical responses to free-field speech tokens while the patient wears their hearing aid, to confirm objectively that amplified speech sounds are audible at the cortex. Widely used to validate infant fittings.

See also: Speech token, Free-field testing, Acoustic change complex

Arousal state☆

also: state, wakefulness, sleep state

The patient's level of wakefulness. Unlike the ABR, the late cortical response degrades in sleep and sedation, so cortical audiometry requires an awake, relaxed but alert patient.

See also: N1, Residual noise, Signal averaging

Auditory brainstem response☆

also: ABR, BERA

The early (1–10 ms) evoked response from the auditory nerve and brainstem. The cortical response complements it: the ABR tests neural synchrony up to the brainstem, the cortical response tests detection at the cortex.

See also: Auditory steady-state response, Cortical auditory evoked potential, Auditory neuropathy spectrum disorder

Auditory neuropathy spectrum disorder☆

also: ANSD, auditory neuropathy, auditory dyssynchrony

A disorder with normal outer-hair-cell function (present OAEs) but disordered neural transmission (absent or grossly abnormal ABR). A present cortical response here can predict speech-perception potential when the ABR cannot.

See also: Auditory brainstem response, Cortical auditory evoked potential, Objective threshold estimation

Auditory steady-state response☆

also: ASSR

An evoked response to a rapidly modulated tone, analysed in the frequency domain to give frequency-specific objective thresholds — including in sleep. A common alternative or complement to cortical threshold testing.

See also: Auditory brainstem response, Objective threshold estimation, Cortical auditory evoked potential

Cortical auditory evoked potential☆

also: CAEP, cortical evoked response, late latency response, LLR, slow vertex potential, SVP

The scalp-recorded electrical response of the auditory cortex to sound, occurring roughly 50–300 ms after stimulus onset. Its presence indicates that sound has been detected and processed as far as the cortex.

See also: P1, N1, P2, Obligatory response, Cortical electric response audiometry

Cortical electric response audiometry☆

also: CERA, cortical ERA, slow vertex response audiometry

Using the cortical auditory evoked potential to estimate hearing threshold objectively. The lowest level at which a repeatable cortical response is seen approximates the behavioural threshold for that stimulus.

See also: Cortical auditory evoked potential, Objective threshold estimation, Non-organic hearing loss

Cortical maturation☆

also: central auditory maturation, P1 maturation

The age-related shortening of P1 latency as the auditory cortex develops with sound exposure. A delayed or flat P1 maturational curve signals abnormal central development.

See also: P1, Sensitive period

Electrode montage☆

also: recording montage, electrode array

The arrangement of recording electrodes — typically vertex (active), linked mastoids or earlobes (reference) and a forehead ground — chosen to maximise the cortical response and reject noise.

See also: Vertex, Signal averaging, Residual noise

Free-field testing☆

also: sound-field, aided free-field

Presenting the stimulus through a loudspeaker rather than an insert earphone, so the patient can be tested while wearing hearing aids or a cochlear implant. The mode of presentation for aided cortical assessment.

See also: Aided cortical assessment, Speech token

Hotelling's T²☆

also: Hotelling T2, automated response detection, statistical detection

A multivariate statistic that decides objectively whether a cortical response is present, by testing whether the averaged waveform differs from flat noise across several time points. It removes some of the subjectivity of visual detection.

See also: Signal averaging, Residual noise, Aided cortical assessment

Mismatch negativity☆

also: MMN

A negative response to an occasional deviant sound in a stream of standards, reflecting pre-attentive discrimination. Like the P300 it is a cognitive marker, not an audibility test, and is mainly a research tool.

See also: P300, Acoustic change complex, Obligatory response

N1☆

also: N100, N1 component

The large negative peak near 100 ms, generated mainly in and around the supratemporal auditory cortex. It dominates the adult cortical response but matures late and is unreliable in infants.

See also: Cortical auditory evoked potential, P2, Vertex, Arousal state

N2☆

also: N250

A later negative deflection near 200–300 ms, more prominent in children than adults. Part of the obligatory complex but less used clinically than N1–P2.

See also: Cortical auditory evoked potential, P1, N1

Non-organic hearing loss☆

also: functional hearing loss, pseudohypacusis, exaggerated loss

A claimed hearing loss greater than the true organic loss. Because the cortical response is a frequency-specific objective threshold test in an awake adult, it is the reference method for confirming true thresholds in medicolegal cases.

See also: Cortical electric response audiometry, Objective threshold estimation

Objective threshold estimation☆

also: objective audiometry, electrophysiological threshold

Estimating hearing thresholds from a physiological response rather than a voluntary button-press. Cortical thresholds typically lie within about 5–10 dB of behavioural thresholds in cooperative adults.

See also: Cortical electric response audiometry, Non-organic hearing loss, P2

Obligatory response☆

also: exogenous response, sensory response

A cortical response that depends on the physical properties of the stimulus rather than attention or task — the P1–N1–P2 complex. It can be recorded in a passive, non-attending listener, which is what makes it clinically practical.

See also: Cortical auditory evoked potential, P300, Mismatch negativity

P1☆

also: P50, P1 component

The first prominent positive peak of the cortical response, near 50–100 ms in adults. In young children it is the dominant, robust component and its latency is used as a biomarker of central auditory maturation.

See also: Cortical auditory evoked potential, N1, Sensitive period, Cortical maturation

P2☆

also: P200, P2 component

The positive peak near 180–200 ms that follows N1. The N1–P2 amplitude is the measure most often tracked when the cortical response is used for objective audiometry in adults.

See also: N1, Cortical auditory evoked potential, Objective threshold estimation

P300☆

also: P3, P3b, endogenous potential

A late, attention-dependent (endogenous) positive wave near 300 ms elicited when a listener detects a rare target sound. It indexes cognitive processing rather than audibility and is not used for threshold estimation.

See also: Mismatch negativity, Obligatory response, Cortical auditory evoked potential

Residual noise☆

also: EEG noise, background noise, residual EEG

The leftover non-time-locked EEG remaining in the average. Because the cortical response is large, the main task is driving residual noise low enough — through enough sweeps and good state — to see the response clearly.

See also: Signal averaging, Hotelling's T², Arousal state

Sensitive period☆

also: critical period, developmental window

The early-childhood window during which the central auditory pathways remain maximally plastic. P1 latency tracks whether stimulation has driven normal maturation, informing the timing of cochlear implantation.

See also: P1, Cortical maturation, Auditory neuropathy spectrum disorder

Signal averaging☆

also: ensemble averaging, time averaging

Repeating the stimulus many times and averaging the EEG epochs so the time-locked cortical response builds up while random EEG noise cancels out. Fewer sweeps are needed than for the much smaller ABR.

See also: Residual noise, Hotelling's T², Electrode montage

Speech token☆

also: /m/ /g/ /t/, speech stimulus

Short natural speech sounds chosen to sample different frequency regions — /m/ for low, /g/ for mid and /t/ for high frequencies. Cortical responses to each token show whether that part of the speech spectrum is audible.

See also: Aided cortical assessment, Acoustic change complex, Free-field testing

Vertex☆

also: Cz, vertex electrode

The top of the head (Cz in the 10–20 system), where the N1–P2 complex is largest. The active recording electrode for cortical audiometry sits at or near the vertex.

See also: Electrode montage, N1, Cortical auditory evoked potential

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