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Updated: Jul 14, 2026
Infant Auditory Processing and Event-related Brain Oscillations
Published on: July 1, 2015
On and Off magnetic auditory evoked responses in early infancy: a possible marker of brain immaturity
R T Wakai1, W J Lutter, M Chen
1Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, USA. rtwakai@wisc.edu
Insights
Auditory evoked responses (AERs) in infants show prominent off-responses, especially in pre-term babies. Measuring these off-responses may help assess infant neurodevelopment and brain immaturity.
Area of Science:
- Neuroscience
- Developmental Biology
- Auditory Neuroscience
Background:
- Auditory evoked responses (AERs) are crucial for assessing auditory pathway development.
- Understanding infant AERs, particularly on- and off-responses, is vital for tracking neurodevelopment.
Purpose of the Study:
- To investigate the developmental trajectory of auditory evoked on- and off-responses in early infancy.
- To characterize the characteristics of infant AERs in relation to conceptional age (CA).
Main Methods:
- Serial AERs were recorded in 17 healthy infants from 39 to 66 weeks CA.
- Stimuli included 1.0-second tones (1.5 kHz) and varying tone durations (0.2-2.0 s) to examine on- and off-responses.
- Substudies focused on off-responses to tones of different durations.
Main Results:
- Infant on- and off-responses showed similar amplitudes, unlike adults where on-responses are larger.
- Off-responses dominated AERs in infants younger than 38 weeks CA and were prominent up to 47 weeks CA.
- Off-responses were observed for brief tones (0.2 s), though a specific component (P400m) was often absent for durations ≤0.5 s.
- Interactions between on- and off-response components were noted, with suppression occurring when they overlapped.
Conclusions:
- Infant auditory off-responses are significantly more prominent than in adults, particularly in preterm infants and at earlier conceptional ages.
- Infant AERs display complex behavior, with individual components interacting and functioning independently.
- Auditory off-response measurement offers a potential biomarker for assessing infant neurodevelopment and brain immaturity.
Objective:
To follow the development of the auditory evoked on- and off-responses in early infancy.
Methods:
The subjects were healthy infants, studied at conceptional age (CA) 39-66 weeks. Serial auditory evoked responses (AERs) were recorded in 17 subjects in response to tones of frequency 1.5 kHz and duration 1.0 s in order to follow the development of the AERs. Two small substudies were performed to examine off-responses evoked by tones of varying duration. The first used 0.2, 0.3, 0.4, and 0.5s tones; the second used 0.5, 1.0, and 2.0 s tones.
Results:
For the 1.0 s tones, the on- and off-responses consisted of three components: P250, P400, and N750 m. The on- and off-responses had similar amplitude, in contrast to adult AERs in which the on-responses are typically much larger. Prior to about CA 47 weeks, the on-responses were actually smaller on average than the off-responses, and in infants born prior to CA 38 weeks the AERs were dominated by the off-response. Off-responses were seen for tones as brief as 0.2 s; however, the P400m component was often absent in the off-responses for tone durations < or = 0.5 s. An interaction was observed in which the N750 m-On component was strongly suppressed when it overlapped the P250 m-Off.
Conclusions:
Off-responses are much more prominent in infant than in adult AERs, especially in pre-term infants and at early CAs. On- and off-responses also exhibit more complex behavior in infants than in adult; the individual components can interact and behave independently.
Significance:
Measurement of auditory off-responses can improve the assessment of infant neurodevelopment, potentially providing a marker of brain immaturity.
