The grand-averaged amplitude of the N1m elicited by the vowels /a/ and /u/ with periodic, aperiodic, and tonal excitation (due to hemispheric symmetry, the left- and right-hemispheric data has been averaged). The vowels with periodic glottal excitation (/a/per & /u/per) elicited the most prominent N1m responses, and the amplitude difference between the two was statistically significant. In all cases, the vowels with aperiodic (/a/aper & /u/aper) and tonal (/a/tone & /u/tone) excitation resulted in N1m responses with significantly smaller amplitudes than did vowels with periodic excitation. Bars indicate standard error of the mean.
Tiitinen et al. BMC Neuroscience 2005 6:62 doi:10.1186/1471-2202-6-62