Short-Term Habituation of Auditory N1 in Spoken Word-Forms Is Modulated by Phonological Information.

Short-term auditory habituation is typically reflected by decreased but recoverable amplitudes of the N1 component of event-related potentials to repeated stimuli. It remains less well understood whether and how N1 habituation is modulated by the human cognition. The current study aims to further test for the potential modulatory roles of phonological information carried by spoken word-forms. Two phonological variables, namely lexicality (real versus pseudoword-form) and usage frequency (high versus low frequency), are considered and combined factorially, yielding four types of monosyllabic Mandarin spoken word-forms. Each type consists of 10 items (i.e., word-forms). The stimuli were passively presented to native Mandarin speakers in trains of five (S1-S5), while their EEG was recorded. The peak amplitudes of N1 to the same type of speech stimuli were calculated for each position by averaging the trains extracted from the EEG recording. Then, the N1 habituation was quantified for the two electrodes of interest (C3 and C4) in each repetitive presentation position (S2-S5). The results showed that the N1 habituation in low-frequency pseudo word-forms was consistently greater than in low-frequency real word-forms and high-frequency pseudo word-forms, respectively, at the fourth presentation (S4). The results suggest the first evidence that different types of phonological information (i.e., lexicality and usage frequency) modulate N1 habituation, interactively. Sensory filtering is proposed as a candidate mechanism for mediating between the processing of phonological information and the short-term habituation of auditory N1.