Abstract
Auditory change detection is crucial for the development of the auditory system and a prerequisite for language development. In neonates, stimuli with broad spectral width like white noise (WN) elicit the highest response compared to pure tone and combined tone stimuli. In the current study we addressed for the first time the question how fetuses react to “WN” stimulation. Twenty-five fetuses (Mage = 34.59 weeks GA, SD ± 2.35) and 28 healthy neonates and infants (Mage = 37.18 days, SD ± 15.52) were tested with the first paradigm, wherein 500 Hz tones, 750 Hz tones, and WN segments were randomly presented and auditory evoked responses (AERs) were measured using fetal magnetoencephalography (fMEG). In the second paradigm, 12 fetuses (Mage = 25.7 weeks GA, SD ± 2.4) and 6 healthy neonates (Mage = 23 days and SD ± 6.2) were presented with two auditory oddball conditions: condition 1 consisted of attenuated WN as standard and 500 Hz tones and WN as deviants. In condition 2, standard 500 Hz tones were intermixed with WN and attenuated WN. AERs to volume change and change in spectral width were evaluated. In both paradigms, significantly higher AER amplitudes to WN than to pure tones replicated prior findings in neonates and infants. In fetuses, no significant differences were found between the auditory evoked response amplitudes of WN segments and pure tones (both paradigms). A trend toward significance was reached when comparing the auditory evoked response amplitudes elicited by attenuated WN with those elicited by WN (loudness change, second paradigm). As expected, we observed high sensibility to spectral width in newborns and infants. However, in the group of fetuses, no sensibility to spectral width was observed. This negative finding may be caused by different attenuation levels of the maternal tissue for different frequency components.
Highlights
Auditory change detection is an important prerequisite for a functional auditory system as well as for the development of language perception and can serve as an indicator for healthy cognitive functioning and development
In the current study we addressed for the first time the question how fetuses react to “white noise (WN)” stimulation.Twenty-five fetuses (Mage = 34.59 weeks GA, SD ± 2.35) and 28 healthy neonates and infants (Mage = 37.18 days, SD ± 15.52) were tested with the first paradigm, wherein 500 Hz tones, 750 Hz tones, and WN segments were randomly presented and auditory evoked responses (AERs) were measured using fetal magnetoencephalography
Most studies investigating change detection used oddball paradigms and evaluated AERs elicited by individual stimuli and mismatch negativity (MMN) responses determined by the difference between AERs elicited by standard and deviant stimuli
Summary
Auditory change detection is an important prerequisite for a functional auditory system as well as for the development of language perception and can serve as an indicator for healthy cognitive functioning and development. It has been repeatedly shown that humans possess already at birth the capacity to process acoustic regularities and react to violations of such regularities, meaning that they are able to detect and discriminate different patterns of sound (Carral et al, 2005). AERs are neurophysiologic indices of sensory functioning and their different components reflect basic cognitive functions. MMN (Näätänen, 2001) – a negative component which in adults peaks at around 150 ms after change onset – is considered as an indicator of automatic change detection reflecting discriminatory capacity. Kushnerenko et al (2002) studied the development of change detection in neonates over the first 12 months and did not find statistically significant differences between the Frontiers in Human Neuroscience www.frontiersin.org
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