Comprehension, intelligibility, neural oscillations: two interesting new papers

There are two new papers on the neurophysiological correlates of speech and language processing that are quite interesting. They are closely related to each other and are fun to read (and discuss) as a pair. Both compare the responses to intelligible versus unintelligible speech using neuronal oscillations as the metric. One group focuses on the gamma band, one on the theta band. Both papers do a terrific job motivating the study, and both show some nice analyses.

One paper is by Marcela Peña and Lucia Melloni and just appeared in the Journal of Cognitive Neurocience. Brain Oscillations during Spoken Sentence Processing, May 2012, Vol. 24, No. 5, Pages 1149-1164.

Marcela and Lucia used high-density EEG and employed a cross-linguistic design. They recorded from Spanish and Italian participants while they were listening to Spanish, Italian, or Japanese. The study derives from the perspective of 'binding by synchrony,' a position that continues to receive a lot of attention in systems and cognitive neuroscience - but is not yet as widely investigated in speech/language studies. The assumption is that when listening to a language that the listener understands (i.e. there is comprehension at the sublexical, lexical, syntactic, semantic levels), whatever neural signal reflects 'binding' across the populations that need to be coordinated will be enhanced in the intelligible conditions (i.e. Spanish for Spanish speakers, Italian for Italian speakers). What they observe is that the gamma band is selectively enhanced during the sentence when it is comprehended. (Their figures 1 and 5 tell the whole story.) They conclude that the low-frequency, theta activity tracks lower-level information, the (lower) gamma band reflects what happens in intelligible speech, i.e. binding of higher level representations. Overall, this supports a binding-by-synchrony style view for language processing.

And a  slightly different perspective/conclusion ...

The other paper is by Jonathan Peelle, Joachim Gross, and Matt Davis and is in Cerebral Cortex. Phase-Locked Responses to Speech in Human Auditory Cortex are Enhanced During Comprehension, doi: 10.1093/cercor/bhs118.

Jonathan, Joachim, and Matt used MEG and presented listeners with vocoded speech that was either intelligible (16 channels), partially intelligible (4 channels), or unintelligible (1 channel). They also presented a 4 channel unintelligible condition (spectrally rotated). They calculate a quantity they call 'cerebro-acoustic coherence', used to quantify the relation between the envelopes of the stimuli and the low-frequency (4-7 Hz) neural response. They show that when a sentence is intelligible, the coherence is systematically higher. (Their figures 1 and 4 pretty much tell the story.) Of special interest is their observation that there is an MTG-centered, left lateralized activation when comparing 4 channel intelligible versus unintelligible stimuli. This adds further support to the key role MTG plays for (lexically mediated) intelligibility. Moreover, their data challenge what some of my collaborators and I have argued (theta tracking is acoustic; e.g. Howard & Poeppel 2010, 2012 etc.)

A little whining, some small regrets ... There are three things I would like to hear about from Marcela and Lucia. (i) Why not analyze the low frequency response components in more detail? (ii) Why not look at the phase, and focus solely on power? (iii) Why did the gamma band response in the intelligible conditions not start till 1000 ms after the sentence has started? Presumably the first second of a sentence is also understood ... And from Jonathan, Joachim and Matt, I would have liked to know (i) Why no analyses of the higher frequencies, e.g. the low gamma band? (ii) Why no analyses of power? (iii) Why are the behavioral data for 4 channels (fig 1E) so different from the rest of the literature using such materials (Shannon, Drullman etc.)?

Notwithstanding a little complaining, these are very cool papers! So, if we could have these two articles date, and have them generate a paper-offspring, baby paper, I could imagine seeing some interesting alignments between theta and gamma that reflect intelligibility. Maybe we need both regimes of neuronal oscillations to generate usable representations ....

POSTDOCTORAL POSITION - CENTER FOR LANGUAGE SCIENCE - The Pennsylvania State University

POSTDOCTORAL POSITION
CENTER FOR LANGUAGE SCIENCE
The Pennsylvania State University

The Center for Language Science (CLS) at The Pennsylvania State University (http://cls.psu.edu/) invites applications for an anticipated postdoctoral position. The CLS is home to a cross-disciplinary research program that includes a new NSF training program, Partnerships for International Research and Education (PIRE): Bilingualism, mind, and brain: An interdisciplinary program in cognitive psychology, linguistics, and cognitive neuroscience. The program provides training in research on bilingualism that includes an international perspective and that exploits opportunities for collaborative research conducted with one of our international partner sites in the UK (Bangor, Wales), Germany (Leipzig), Spain (Granada and Tarragona), The Netherlands (Nijmegen), Sweden (Lund) and China (Hong Kong and Beijing) and in conjunction with our two domestic partner sites at Haskins Labs and the VL2 Science of Learning Center at Gallaudet University. The successful postdoctoral candidate will have an opportunity to engage in collaborative research within the Center's international network.

We welcome applications from candidates with preparation in any of the disciplines that contribute to our program. The successful candidate will benefit from a highly interactive group of faculty whose interests include bilingual language processing, language acquisition in children and adults, and language contact, among other topics. Applicants with interests in these topics and with an interest in extending their expertise within experimental psycholinguistics and cognitive neuroscience are particularly welcome to apply. There is no expectation that applicants will have had prior experience in research on bilingualism but we expect candidates to make a commitment to gain expertise in research on bilingualism and also in using neuroscience methods, including both fMRI and ERPs. There is also a possibility of teaching one course during the academic year in the Program in Linguistics.

Questions about faculty research interests may be directed to relevant core training faculty: Psychology: Judith Kroll, Ping Li, Janet van Hell, and Dan Weiss; Spanish: Rena Torres Cacoullos, Giuli Dussias, John Lipski, and Karen Miller; Communication Sciences and Disorders:  Carol Miller; German: Carrie Jackson, Mike Putnam, and Richard Page. Administrative questions can be directed to the Director of the Center for Language Science, Judith Kroll:  jfk7@psu.edu. More information about the Center for Language Science (CLS), about the PIRE program, and faculty research programs can be found at http://cls.psu.edu or http://cls.psu.edu/PIRE.

The initial appointment will be for one year, with a strong possibility of renewal for the next year. Salary and benefits follow NSF/NIH guidelines. The search is open to all eligible candidates regardless of citizenship.
Applicants should send a CV, several reprints or preprints, and a statement of research interests. This statement should indicate two or more core faculty members as likely primary and secondary mentors and should describe the candidate's goals for research and training during a postdoctoral position, including previous experience and directions in which the candidate would like to develop his/her expertise in the language science of bilingualism. Candidates interested in gaining teaching experience should include information on teaching experience and preparation. Applicants should arrange for three letters of recommendation to be sent separately.

Application materials and letters of recommendation should be sent electronically to pirepostdoc@gmail.com.  We will begin to review applications by June 10, 2012. We will consider applications until the position is filled. The appointment can begin as soon as August 1, 2012. We encourage applications from individuals of diverse backgrounds.  Penn State is committed to affirmative action, equal opportunity and the diversity of its workforce.

Why are speech/language neuroscientists NOT concerned about bias in their behavioral measurements?

Perceptual decisions involve two processes, perceptual analysis and response selection, both of which can affect typical behavioral measures such as percent correct or reaction time.  Crucially, response selection is strongly affected by response bias, the criterion that a given subject sets for responding one way or another under a particular set of task conditions.  For example, if I ask you to tell me when you hear the syllable /ba/ in a noisy environment, and I tell you that I will give you $100 each time you say "yes" correctly (a hit), but will charge you $500 each time you say "yes" incorrectly (a false positive), you will be biased to be very conservative in saying "yes". I can push around your bias depending on how I set up the task.  Presumably, brain damage or temporary modulation of neural activity (e.g., TMS) could also, in principle, change the task conditions for the subject and bias responses, so we have to be equally careful when we manipulate the system neurophysiologically.

Happily, there is a well-worked out method for measuring the perceptual and decision components of the task.  It's called signal detection theory.  Yet most speech/language neuroscientist fail to use SDT methods to control for response bias.  The results of such studies are potentially contaminated.

For example, this is true of ALL of the TMS studies of the role of the motor system in speech perception/recognition.  And it is true of the latest study in this line of experiments.  I've pasted the abstract in below.

This study stimulated with theta-burst TMS the hand motor area and showed a change in response times in lexical decision to hand action verbs but not non-action verbs.  They conclude that "premotor cortex has a functional role in action-language understanding."

Here's why you can't conclude this from the study: the dependent measure, RT, is susceptible to response bias and therefore can be modulated either by perceptual/recognition processes (the process under investigation) OR by biasing the decision process.  The result is therefore ambiguous and as a result cannot lead to the conclusion the authors wish to make.

Psychol Sci. 2011 Jul;22(7):849-54. Epub 2011 Jun 24.

A functional role for the motor system in language understanding: evidence from theta-burst transcranial magnetic stimulation.

Willems RM, Labruna L, D'Esposito M, Ivry R, Casasanto D.

Source

1Helen Wills Neuroscience Institute, University of California, Berkeley, USA. roel.willems@donders.ru.nl

Abstract

Does language comprehension depend, in part, on neural systems for action? In previous studies, motor areas of the brain were activated when people read or listened to action verbs, but it remains unclear whether such activation is functionally relevant for comprehension. In the experiments reported here, we used off-line theta-burst transcranial magnetic stimulation to investigate whether a causal relationship exists between activity in premotor cortex and action-language understanding. Right-handed participants completed a lexical decision task, in which they read verbs describing manual actions typically performed with the dominant hand (e.g., "to throw," "to write") and verbs describing nonmanual actions (e.g., "to earn," "to wander"). Responses to manual-action verbs (but not to nonmanual-action verbs) were faster after stimulation of the hand area in left premotor cortex than after stimulation of the hand area in right premotor cortex. These results suggest that premotor cortex has a functional role in action-language understanding.

Two Positions - MARCS Institute, Univ of Western Sydney

Ref 453/12:

Career Development Fellowship in Multisensory Processing (Behaviour based methods), MARCS Institute

MARCS Institute is a vibrant interdisciplinary research institute of the University of Western Sydney. Research at MARCS is conducted in five interdisciplinary research programs: Speech & Language, Music Cognition & Action, Bioelectronics & Neuroscience, Multisensory Processing, and Human Machine Interaction. MARCS is located on the Bankstown, Campbelltown, Kingswood and Parramatta Campuses.

MARCS is seeking to fill a Career Development Fellowship in Multisensory Processing (Behaviour based methods). The successful applicant would be involved in experimentally-based research investigating multisensory processing involving behavioural methods, including the development of experimental protocols and specialised analyses, e.g., Bayesian approaches, motion tracking analysis.

Eligibility: To apply for this position you must have recently completed a PhD qualification in cognitive psychology or cognate discipline and are required to submit a research and scholarly activity plan.

Importantly, we seek an energetic, forward thinking, dynamic, and innovative scholar to take on this Career Development Fellowship. The successful applicant is expected to be developing a strong international standing and research reputation, an excellent research background in the area of cognitive psychology and multisensory processing, the potential to win competitive research income, and an excellent publication record.

Fixed term for a period of two years with the possibility for a further fixed term appointment of two years (subject to satisfactory assessment).

The position will be based on the Bankstown campus.

Remuneration Package: Academic Level B $101,761 to $120,078 p.a. (comprising Salary $85,989 to $101,538 p.a., 17% Superannuation and Leave Loading).

Position Enquiries: Professor Christopher Davis, on (02) 9772 6855 or emailchris.davis@uws.edu.au

Closing Date: 17 June 2012

For a copy of the Position Description and information on how to apply, go tohttps://uws.nga.net.au/cp/

-----------------

Ref 454/12:

Career Development Fellowship in Multisensory Processing (Brain based methods), MARCS Institute

MARCS Institute is a vibrant interdisciplinary research institute of the University of Western Sydney. Research at MARCS is conducted in five interdisciplinary research programs: Speech & Language, Music Cognition & Action, Bioelectronics & Neuroscience, Multisensory Processing, and Human Machine Interaction. MARCS is located on the Bankstown, Campbelltown, Kingswood and Parramatta Campuses.

MARCS is seeking to fill a Career Development Fellowship in Multisensory Processing (Brain based methods). The successful applicant would be involved in experimental based research investigating multisensory processing involving behavioural and functional image-based, e.g., EEG/ERP/fMRI or neuro-activation methods and development of experimental protocols.

Eligibility: To apply for this position you must have recently completed a PhD qualification in cognitive neuroscience, neuroscience, and/or cognitive psychology and are required to submit a research and scholarly activity plan.

Importantly, we seek an energetic, forward thinking, dynamic, and innovative scholar to take on this Career Development Fellowship. The successful applicant is expected to be developing a strong international standing and research reputation, an excellent research background in the area of cognitive neuroscience, neuroscience, and/or cognitive psychology, the potential to win competitive research income, and an excellent publication record.

Fixed term for a period of two years with the possibility for a further fixed term appointment of two years (subject to satisfactory assessment).

The position will be based on the Bankstown campus.

Remuneration Package: Academic Level B $101,761 to $120,078 p.a. (comprising Salary $85,989 to $101,538 p.a., 17% Superannuation and Leave Loading).

Position Enquiries: Professor Christopher Davis, on (02) 9772 6855 or emailchris.davis@uws.edu.au

Closing Date: 17 June 2012

For a copy of the Position Description and information on how to apply, go tohttps://uws.nga.net.au/cp/