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Abstract:
It has been demonstrated that the auditory N1 undergoes
significant developmental changes. As well, the components of the
N1 follow different developmental timelines; specifically, the
vertex N1b becomes identifiable after age 9 [1] whereas the
t-complex N1 shows earlier, but asymmetrical, development. Over the
left hemisphere, both the N1a and N1c are mature by 3 years, while
the right hemisphere t-complex N1 does not reach maturity until
after 7-8 years [2]. We were interested in whether the left
hemisphere t-complex N1 was observable in infants. Methods: Data
were collected from fifteen 8-month-old infants using a
12-electrode montage referenced to Cz with a re-computed averaged
reference. Infants listened to a phoneme (/da/) and a tone (2kHz).
Results: As expected, the vertex N1b and the right hemisphere
t-complex N1 were not observed in the infants. Interestingly, over
the left hemisphere, the t-complex N1a was present; however, the
N1c was not observed. Discussion: This study has dissociated the
developmental timelines for the two components of the left
hemisphere t-complex N1. The data suggest that the neural processes
underlying stimulus detection (reflected by the N1a) are mature by
8 months, whereas the processes underlying auditory discrimination
(N1c) mature between 8-months and 3 years.
References:
[1] CW Ponton, JJ Eggermont, B Kwong and M Don. (2000). Clinical
Neurophysiology,111,220-236.
[2] EW Pang and MJ Taylor. (2000). Clinical Neurophysiology,
111,388-397.
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