Perception of acoustically complex phonological features in vowels is reflected in the induced brain-magnetic activity

Abstract

A central issue in speech recognition is which basic units of speech are extracted by the auditory system and used for lexical access. One suggestion is that complex acoustic-phonetic information is mapped onto abstract phonological representations of speech and that a finite set of phonological features is used to guide speech perception. Previous studies analyzing the N1m component of the auditory evoked field have shown that this holds for the acoustically simple feature place of articulation. Brain magnetic correlates indexing the extraction of acoustically more complex features, such as lip rounding (ROUND) in vowels, have not been unraveled yet. The present study uses magnetoencephalography (MEG) to describe the spatial-temporal neural dynamics underlying the extraction of phonological features. We examined the induced electromagnetic brain response to German vowels and found the event-related desynchronization in the upper beta-band to be prolonged for those vowels that exhibit the lip rounding feature (ROUND). It was the presence of that feature rather than circumscribed single acoustic parameters, such as their formant frequencies, which explained the differences between the experimental conditions. We conclude that the prolonged event-related desynchronization in the upper beta-band correlates with the computational effort for the extraction of acoustically complex phonological features from the speech signal. The results provide an additional biomagnetic parameter to study mechanisms of speech perception.

Assessing the effect of physical differences in the articulation of consonants and vowels on audiovisual temporal perception

“…A similar analysis of the PSS data revealed a significant main effect of Backness/Roundedness [ F (1, 10) = 18.60, p < 0.01], with larger auditory leads being required for rounded vowels articulated at the back of the tongue (M = 51 ms) than for unrounded vowels articulated at the front (M = 12 ms; see Figure 8B ). The large auditory leads observed for Roundedness agrees with research showing that the recognition of rounded stimuli is difficult for both automatic speech recognition systems, with the systems being blind to roundedness, and humans who recruit more subtle physical cues and possibly more complex operations along the auditory pathway in perceiving rounded vowels (e.g., Eulitz and Obleser, 2007 ).…”

Internalized Timing of Isochronous Sounds Is Represented in Neuromagnetic Beta Oscillations

“…form of auditory-motor transformation such as voice perceptions involving posterior auditory cortices (Warren et al, 2005) could also activate beta modulation, in line with available evidence for speech perception based on articulatory characteristics (Eulitz and Obleser, 2007) and audiovisual multimodal integration (Fingelkurts et al, 2007).…”

The influence of rhythmic (ir)regularities on speech processing: Evidence from an ERP study on German phrases

“…Sentence part 1 Sentence part 2 explanation is supported by the component's position in the frontocentral area, where auditory working memory is supposed to be located (e.g., Kaiser & Lutzenberger, 2004;Eulitz & Obleser, 2007). However, the connection between a pronounced effect in the frontocentral area measured by an EEG and working memory regions is very speculative, since the spatial resolution of ERPs is poor.…”