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Rate and adaptation effects on the auditory evoked brainstem response in human newborns and adults
1The University of Wisconsin-Madison Medical School, Department of Neurology, 53792-5132, USA.
Insights
Auditory evoked brainstem response (ABR) testing reveals developmental differences in how newborns and adults adapt to sound. Newborns show slower adaptation to repetitive auditory stimuli at the brainstem level compared to adults.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Developmental Neuroscience
Background:
- Auditory evoked brainstem response (ABR) is a key tool for assessing auditory pathway function.
- Understanding auditory adaptation is crucial for diagnosing hearing impairments and developmental disorders.
Purpose of the Study:
- To investigate developmental differences in auditory adaptation at the brainstem level in human newborns and adults.
- To compare the effects of stimulus repetition rate on ABR latencies and amplitudes between age groups.
Main Methods:
- Recorded auditory evoked brainstem responses (ABRs) in human newborns and adults.
- Varied stimulus repetition rates and intensities to assess adaptation.
- Analyzed wave V latency and amplitude changes.
Main Results:
- Both newborns and adults showed increased ABR latencies and decreased amplitudes with higher repetition rates.
- Newborns exhibited larger wave V latency increases and smaller amplitude decreases than adults.
- Newborns displayed a slower, two-stage adaptation process, particularly at short inter-stimulus intervals.
Conclusions:
- Significant developmental differences exist in brainstem auditory adaptation to repetitive stimulation.
- These findings suggest unique neural processing characteristics in the developing auditory system of newborns.
Abstract:
Auditory evoked brainstem response (ABR) latencies increased and amplitudes decreased with increasing stimulus repetition rate for human newborns and adults. The wave V latency increases were larger for newborns than adults. The wave V amplitude decreases were smaller for newborns than adults. These differences could not be explained by developmental differences in frequency responsivity. The transition from the unadapted to the fully adapted response was less rapid in newborns than adults at short (= 10 ms) inter stimulus intervals (ISIs). At longer ISIs (= 20 ms) there were no developmental differences in the transition to the fully adapted response. The newborn transition occurred in a two stage process. The rapid initial stage observed in adults and newborns was complete by about 40 ms. A second slower stage was observed only in newborns although it has been observed in adults in other studies (Weatherby and Hecox, 1982; Lightfoot, 1991; Lasky et al., 1996). These effects were replicated at different stimulus intensities. After the termination of stimulation the return to the wave V unadapted response took nearly 500 ms in newborns. Neither the newborn nor the adult data can be explained by forward masking of one click on the next click. These results indicate human developmental differences in adaptation to repetitive auditory stimulation at the level of the brainstem.