Recently, with a data set dating back to my time in Angela Friederici’s department, we proposed the idea that auditory signal degradation would affect the exact configuration of activity along the main processing streams of language, in the superior temporal and inferior frontal cortex. We tentatively coined this process “upstream delegation”: The activations that were driven by increasing syntactic demands, with the challenge of decreasing signal quality coming on top, were all of a sudden found more “upstream” from where we had located them with improvingsignal quality.
Author: Jonas
In addition to the exciting consonantal mismatch negativity work Mathias and Alexandra will be showing (TUESDAY AM session, posters UU10 and UU11), we will have the following posters this year. Come by!
Chris Petkov and I are showing our brand new data in the TUESDAY PM session, poster LL14.
I myself will be presenting in the WEDNESDAY AM session, XX15 – more alpha oscillations in working memory under speech degradation.
Finally, I also have the pleasure to be a co-author on Sarah Jessen’s, who is showing très cool multimodal integration data on voices and bodies under noisy conditions in the WEDNESDAY PM session, XX15.
There will be two poster presentations at SFN in Washington, DC., on the topic of auditory predictions in speech perception. The first poster, authored by Alexandra Bendixen, Mathias Scharinger, and Jonas Obleser, summarizes as follows:
Speech signals are often compromised by disruptions originating from external (e.g., masking noise) or internal (e.g., sluggish articulation) sources. Speech comprehension thus entails detecting and replacing missing information based on predictive and restorative mechanisms. The nature of the underlying neural mechanisms is not yet well understood. In the present study, we investigated the detection of missing information by occasionally omitting the final consonants of the German words “Lachs” (salmon) or “Latz” (bib), resulting in the syllable “La” (no semantic meaning). In three different conditions, stimulus presentation was set up so that subjects expected only the word “Lachs” (condition 1), only the word “Latz” (condition 2), or the words “Lachs” or “Latz” with equal probability (condition 3). Thus essentially, the final segment was predictable in conditions 1 and 2, but unpredictable in condition 3. Stimuli were presented outside the focus of attention while subjects were watching a silent video. Brain responses were measured with multi-channel electroencephalogram (EEG) recordings. In all conditions, an omission response was elicited from 125 to 165 ms after the expected onset of the final segment. The omission response shared characteristics of the omission mismatch negativity (MMN) with generators in auditory cortical areas. Critically, the omission response was enhanced in amplitude in the two predictable conditions (1, 2) compared to the unpredictable condition (3). Violating a strong prediction thus elicited a more pronounced omission response. Consistent with a predictive coding account, the processing of missing linguistic information appears to be modulated by predictive context.
The second poster looks at similar material, but contrasts coronal [t] with dorsal [k], yielding interesting asymmetries in MMN responses:
Research in auditory neuroscience has lead to a better understanding of the neural bases of speech perception, but the representational nature of speech sounds within words is still a matter of debate. Electrophysiological research on single speech sounds provided evidence for abstract representational units that comprise information about both acoustic structure and articulator configuration (Phillips et al., 2000), thereby referring to phonological categories. Here, we test the processing of word-final consonants differing in their place of articulation (coronal [ts] vs. dorsal [ks]) and acoustic structure, as seen in the time-varying formant (resonance) frequencies. The respective consonants distinguish between the German nouns Latz (bib) and Lachs (salmon), recorded from a female native speaker. Initial consonant-vowel sequences were averaged across the two nouns in order to avoid coarticulatory cues before the release of the consonants. Latz and Lachs served as standard and deviant in a passive oddball paradigm, while the EEG from 20 participants was recorded. The change from standard [ts] to deviant [ks] and vice versa was accompanied by a discernible Mismatch Negativity (MMN) response (Näätänen et al., 2007). This response showed an intriguing asymmetry, as seen in a main effect condition (deviant Latz vs. deviant Lachs, F(1,1920) = 291.84, p < 0.001) of an omnibus mixed-effect model. Crucially, the MMN for the deviant Latz was on average more negative than the MMN for the deviant Lachs from 135 to 185 ms post deviance onset (p < 0.001). We interpret these findings as reflecting a difference in phonological specificity: Following Eulitz and Lahiri, 2004, we assume coronal segments ([ts]) to have less specific (‘featurally underspecified’) representations than dorsal segments ([ks]). While in standard position, Lachs activated a memory trace with a more specific final consonant for which the deviant provided a stronger mismatch than vice versa, i.e. when Latz activated a memory trace with a less specific final consonant. Our results support a model of speech perception where sensory information is processed in terms of discrete units independent of higher lexical properties, as the asymmetry cannot be explained by differences in lexical surface frequencies between Latz and Lachs (both log-frequencies of 0.69). We can also rule out a frequency effect on the segmental level. Thus, it appears that speech perception involves a level of processing where individual segmental representations within words are evaluated.
We are happy to announce that our paper “Asymmetries in the processing of vowel height” will be appearing in the Journal of Speech, Language, & Hearing Research, authored by Philip Monahan, William Idsardi and Mathias Scharinger. A short summary is given below:
[Update]Purpose: Speech perception can be described as the transformation of continuous acoustic information into discrete memory representations. Therefore, research on neural representations of speech sounds is particularly important for a better understanding of this transformation. Speech perception models make specific assumptions regarding the representation of mid vowels (e.g., [
]) that are articulated with a neutral position in regard to height. One hypothesis is that their representation is less specific than the representation of vowels with a more specific position (e.g., [æ]).
Method: In a magnetoencephalography study, we tested the underspecification of mid vowel in American English. Using a mismatch negativity (MMN) paradigm, mid and low lax vowels ([
]/[æ]), and high and low lax vowels ([I]/[æ]), were opposed, and M100/N1 dipole source parameters as well as MMN latency and amplitude were examined.
Results: Larger MMNs occurred when the mid vowel [
] was a deviant to the standard [æ], a result consistent with less specific representations for mid vowels. MMNs of equal magnitude were elicited in the high–low comparison, consistent with more specific representations for both high and low vowels. M100 dipole locations support early vowel categorization on the basis of linguistically relevant acoustic–phonetic features.
Conclusion: We take our results to reflect an abstract long-term representation of vowels that do not include redundant specifications at very early stages of processing the speech signal. Moreover, the dipole locations indicate extraction of distinctive features and their mapping onto representationally faithful cortical locations (i.e., a feature map).
The paper is available here.
References
- Scharinger M, Monahan PJ, Idsardi WJ. Asymmetries in the processing of vowel height. J Speech Lang Hear Res. 2012 Jun;55(3):903–18. PMID: 22232394. [Open with Read]
New lab members joining
As of December 1, we will have two new members joining the Lab.
Björn Herrmann very recently received his Dr. rer. nat. from the University of Leipzig, after doing methodologically advanced worked on MEG and fMRI correlates of early auditory–syntactic interactions in language comprehension.
Dunja Kunke is a trained audiologist and will help us gear up the auditory testing routines in our lab; also, she will be of great help when we begin working with hearing-impaired listeners.
A warm welcome to both of you!
Obleser, J., Weisz, N. (in press) Suppressed alpha oscillations predict intelligibility of speech and its acoustic details. Cerebral Cortex.
[Update]Paper is available here.
References
- Obleser J, Weisz N. Suppressed alpha oscillations predict intelligibility of speech and its acoustic details. Cereb Cortex. 2012 Nov;22(11):2466–77. PMID: 22100354. [Open with Read]
![acgroup_web](https://auditorycognition.com/wordpress/storage/2012/11/acgroup_web-300x105.png)
I am glad to report that the lab is in full flight. (From left to right: ) Anna Wilsch, Julia Erb, Dr. Mathias Scharinger, Dr. Molly Henry, and Antje Strauß have joined forces with me. We are having a splendid time finding out more about speech, degradation of it, and the neural processing of it all. Stay tuned for great project work coming from these bright minds in the years to come.
NB – I hope you don’t mind that we chose the charming back sides of Leipzig rather than our postmodern Institute building as a background. We actually do work just 100 meters from this spot. Maybe we should make it our new hang-out spot and bring neuroscience to the streets?
Phonetic cues instantaneously mapped onto dialectal categories appear to be extracted at early moments in auditory speech perception, as we try to show in our paper
You had me at “Hello”: Rapid extraction of dialect information from spoken words
to appear in NeuroImage (Mathias Scharinger, Philip Monahan, William Idsardi).
In a modified passive oddball design, we compare the Mismatch Negativity (MMN) to deviants in one American English dialect (Standard American English or African-American Vernacular English) to the standards of the respective other dialect. In a control condition, deviants within the same dialects have the same averaged acoustic distance to their standards than the cross-dialectal averaged acoustic distance. Standards and deviants were always spoken exemplars of ‘Hello’ in both dialects (ca. 500 ms). MMN effects are significant in the cross-dialectal condition only, implying that a pure acoustic standard-deviant distance is not sufficient to elicit substantial mismatch effects. We interpret these findings, together with N1m source localization data, as evidence for a rapid extraction of dialect information via salient acoustic-phonetic cues. From the location and orientation of the N1m source activity, we can infer that dialect switches from standards to deviants engage areas in superior temporal sulcus/gyrus.
References
- Scharinger M, Monahan PJ, Idsardi WJ. You had me at “Hello”: Rapid extraction of dialect information from spoken words. Neuroimage. 2011 Jun 15;56(4):2329–38. PMID: 21511041. [Open with Read]