Thursday, February 25, 2010

A chink in the mirror neuron armor?

It is yet to slow the pace of mirror neuron speculation, but at least a reference to my "Eight Problems" paper, as well as this blog, made it on the Mirror Neuron Wikipedia page (no it wasn't me who added it). It actually lists the 8 problems in the "Criticism" (singular, I note) section which is right below the section which details how mirror neurons explain understanding intentions, empathy, language, autism, theory of mind, and gender differences -- apparently the female mirror system is more robust than the male mirror neuron system. Ugh.

Tuesday, February 23, 2010

Lexical effects in speech perception

The influence of the motor system on speech perception has been getting tons of high profile attention lately and "sensorimotor theories" of speech perception are gaining popularity. For an interesting example of the such a theory, check out Jean-Luc Schwartz et al.'s, The Perception-for-Action-Control Theory (PACT): A perceptuo-motor theory of speech perception.

It is all well-and-good to understand the contribution of motor information to speech perception, but let's not forget that there is more to the brain and speech processing than the motor system. For example, there is a long history of research on lexical effects in speech perception. The Ganong (1980) effect is one: the category boundary will shift toward the lexical item in a speech continuum like gift-kift where one end of the continuum is a word. Another example comes from the phoneme restoration effect (Warren, 1970). If a speech segment is deleted in the middle of a word you can easily hear the gap. However, if that gap is replaced by a noise, the missing segment can be heard quite clearly in some cases. This effect is enhanced by lexical information (Samuel, 1981): phonemic restoration is more robust in words than nonwords and in longer words (more lexical predictability) than shorter words.

These are interesting effects that are typically interpreted as evidence for top-down modulation of lower-level auditory perception. (Note that motor effects can be explained in exactly the same way, top-down modulation; there is no need to resurrect the Motor Theory of Speech Perception.) Over the last decade or so, there is been increasing interest in identifying the neural basis of these effects. One study by Myers & Blumstein investigated the Ganong effect and another by Shahin, Bishop, & Miller investigated phonemic restoration. I love this line of work, but I'm not sure we have nailed down the best approach yet.

Myers & Blumstein used voice onset time continua involving gift-kift and a giss-kiss. They took advantage of the fact that the category boundary for these two VOT-matched continua differ because they have lexical items at opposite ends. This allowed them to compare the BOLD response in an fMRI study to same VOT matched stimuli that was either at the boundary in one continuum or in a non-boundary position in the other continuum. They reported more activity for boundary items than non-boundary items in (i) bilateral STG, (ii) L cingulate, (iii) L precentral gyrus, (iv) L mid frontal gyrus, & (v) L precuneus. They interpreted the STG activation as evidence that the lexical information influences early perceptual processes and activations in frontal/midline regions as reflections of higher order executive processes.

This conclusion seems reasonable, but I'm not sure I buy the logic that gets us there. I suppose the logic of the particular comparisons is that for ambiguous stimuli (those at the boundary) the lexical effect will be most prominent and therefore show up in the BOLD response for boundary stimuli relative to non-boundary stimuli. But one might also reason that the strongest lexical effect should be found at certain non-boundary items, namely those that are normally at the boundary but now are not at the boundary because of the lexical pull. I.e., a stimulus that used to be ambiguous is now non-ambiguous because of all the work lexical information has done to affect perception. Another possible explanation of their findings is that boundary items are more difficult to categorize and so require more executive resources (frontal/midline activations) and these executive systems in turn modulate auditory areas, e.g., by increasing attentional gain. In short, I don't think the conclusions are necessarily wrong, but I there are some questions remaining.

Shahin et al. (2009) used a pretty slick design to assess phonemic restoration effects in physically very similar stimuli in an fMRI study. Following Samuel they presented speech that either contained a gap (with noise filling the gap) or did not contain a gap (with noise superimposed over the speech segment). Subjects were asked to decide whether the stimulus was intact or contained a gap. One complication of studying phonemic restoration is that speech that contains a gap is physically different from speech that does not, so it is unclear whether any observed effects result from the illusion or the physical gap. To get around this Shahin et al. manipulated the duration of the noise burst in the stimuli such that all stimuli were right at the threshold boundary for hearing the illusion or not. This resulted in a set of highly overlapping stimuli in terms of their physical properties but a wobbly perception. They then used information about how the stimuli were actually perceived to then probe the brain response.

The primary comparisons were

(1) items that elicited an illusion (items with gaps that were perceived as intact) minus items that were intact and perceived as intact -- so both stimuli were perceived as intact but one was illusory. This contrast was assumed to identify areas involved in phonemic repair.

(2) items that elicited an illusion minus items that failed to elicit an illusion (items with gaps that were perceived as items with gaps). This contrast was assumed to identify areas that correlated with the actually perception of the illusion.

Comparison #1 resulted in activation in Broca's area (~BA44), the anterior insula bilaterally, and the left pre-SMA.
Comparison #2 resulted in activation in left angular gyrus/STS, right STS, precuneus, and bilateral superior frontal sulcus.

Both word and nonword stimuli were used and these effects were evaluated in ROI analyses. The left AG/STS showed an interaction between lexical status and perceptual condition, which the authors suggest is reflective of the use of a lexical template for filling in missing information. Broca's area and insulae also showed an interaction and further seemed to respond most robustly to illusion-failure trials within the word condition (reflecting extra work trying, but failing to repair?).

So unlike the Myers & Blumstein study, Shahin et al. do not report extensive activity in the bilateral STG (the STS activity is very posterior) but instead find "repair" activity in frontal areas and lexical effects ("template matching") in posterior STS/AG.

One complication with the AG/STS activations is that these are all sub-baseline effects (signal intensity < 0), so the differences are degrees of deactivation. One could appeal to the "default network" in explaining these patterns, but the authors argue against such an account. At the very least, the negative activation complicates the picture.

The real question here is what do these subtractions reveal. In principle, I like the idea of correlating responses with perceptual experience. But at the same time, conscious perceptual experience is a fairly high-level phenomenon, whereas many of the processes we are interested in, those down in the trenches of the processing stream that ultimately lead to perception, may be unconscious and may share computations between stimuli that are ultimately perceived one way versus another. So in the end, it is hard to know what is actually being detected and more importantly, what is not being detected.

In general, I think this is an important line of investigation and I'd like to see folks give it more attention. Who knows, it might even lead to a competitor to the sensorimotor models of speech perception: the sensory-lexical model of speech perception.


Ganong, W. F. (1980). Phonetic categorization in auditory word perception. Journal of Experimental Psychology: Human Perception and Performance, 6, 110-125.

Shahin, A., Bishop, C., & Miller, L. (2009). Neural mechanisms for illusory filling-in of degraded speech NeuroImage, 44 (3), 1133-1143 DOI: 10.1016/j.neuroimage.2008.09.045

Myers EB, & Blumstein SE (2008). The neural bases of the lexical effect: an fMRI investigation. Cerebral cortex (New York, N.Y. : 1991), 18 (2), 278-88 PMID: 17504782

Samuel, A.G. (1981). Phonemic restoration: Insights from a new methodology. JEP: General, 110, 474-94.

Warren, R.M. Perceptual restoration of missing speech sounds. Science, 1970, 167, 392-393

Wednesday, February 10, 2010

Debate topics for 2010 Neurobiology of Language Conference

Well, the preference expressed in the most recent TB poll is clear: you like scientific debate sessions! 75% of our random sample (yeah right) indicated that they would like to hear two debate sessions at the 2010 Neurobiology of Language Conference. So here's the next question: What topics would you like to hear debated? Please post comments with your suggestions! We are planning the program now...

Monday, February 8, 2010

What's an "Opinion" in journal reviews?

Some journals have subcategories of reviews that include labels like "opinion" or "perspective". For example, our 2007 paper in Nature Reviews Neuroscience (Hickok, G., & Poeppel, D. (2007). The cortical organization of speech processing Nature Reviews Neuroscience, 8 (5), 393-402 DOI: 10.1038/nrn2113) appeared in the "Perspectives" section, not the "Reviews" section, and was further branded with the dreaded label, OPINION. I find it amusing how some folks use this in their citation of our work: "Hickok, G., & Poeppel, D. (2007) Opinion - The cortical organization...." Is this because they think it is part of the title? Or an attempt to cast doubt on the ideas expressed?

More to the point, what IS an opinion in a review article? Or even more to the point, what ISN'T an opinion? Unless a review article limits itself to a list of observations of the form, "BOLD signal increases at x,y,z coordinate during the presentation of x compared to the presentation of y" or "the time it took subjects to push the button corresponding to the '/ba/' response button was longer with the TMS coil ON compared to when it was off", it is an "opinion". Put differently, unless a review is just a recapitulation of the Results sections of a set of papers, the review is the opinion (interpretation) of the authors. To the extent that an interpretation represents a theoretical explanation of the observations and therefore hypotheses that can be tested, etc., "opinions" are what we should be striving for in scientific inquiry. So why single out some review articles as being "Opinion" while others qualify as "Reviews"?

The answer is that they don't really mean "opinion" because every review, indeed every discussion section, is opinion. What they really mean is "controversial" or "non-conventional" -- ideas that shake things up a bit. I think these kinds of reviews are the most interesting and more likely to have an influence on subsequent research.

So although I think labeling some reviews as "Opinion" is a silly, even unscientific, thing to do, as long as they are doing it, I would take it as a compliment.

But that's just my opinion.

The best job in Helsinki: a post-doc

My friend Riitta Salmelin has sent this ad for a post-doc position. Riitta and her colleagues and students are, of course, at the forefront of doing this sort of connectivity research (especially in the context of language studies), and this would be a great opportunity to learn how to do this work and build new tools. A good paper exemplifying some of their approaches was in TICS:

Salmelin & Kujala. Trends Cogn Sci. 2006 Nov;10(11):519-25. Neural representation of language: activation versus long-range connectivity.

A more recent paper outlining an updated technique to evaluate sources, ideal for those of us obsessing about (quasi-)rhythmic brain activity:

Laaksonen H, Kujala J, Salmelin R. A method for spatiotemporal mapping of event-related modulation of cortical rhythmic activity. Neuroimage. 2008 Aug 1;42(1):207-17.

The lab there is amazingly well equipped, and full of smart and engaging researchers. Plus, in Finland they number their beers by strength, so, for example, you can ask for "a second #3, please" followed by "two more #2's". Very convenient. And for those of you who are metal heads, Finland has one of the best metal scenes, especially black metal. So if you like brain research, metal, and are technically skilled, this job is definitely for you.

Post-doc in Neural Connectivity in Human Cognition
Brain Research Unit, Low Temperature Laboratory

Aalto University (Espoo, Finland)

Cognition is thought to be implemented as large-scale networks of interacting and co-operating brain areas, rather than simply as activation advancing from one area to another. Brain Research Unit (BRU, is a pioneer of time-sensitive brain imaging with magnetoencephalography (MEG). We are actively developing methods for estimating interareal connectivity from MEG and applying such methods to study cognitive processing; we now seek to further strengthen that effort. In the next stage, we hope to clarify (i) the relationship between connectivity estimated from electrophysiological (MEG) and hemodynamic brain imaging data (functional magnetic resonance imaging, fMRI), (ii) the relationship between MEG connectivity measures and activation measures (phase-locked evoked responses, modulation of cortical rhythms), and (iii) the possible role of functional connectivity in the differences and similarities between MEG and fMRI activation maps in cognitive processing, such as language perception and production.

We are looking for a PhD with a deep interest in this type of questions and with training and experience well-suited to address them. The candidate will work in a multidisciplinary group (physics, mathematics, psychology, medicine) that investigates the neural basis of language, methodological and conceptual aspects of long-range neural connectivity, and relationship between MEG and fMRI measures of cognitive processing (Language group, The BRU has a state-of-the-art Vectorview 306-channel MEG system, and access to a 3T MRI scanner on the university campus.

To apply, please send an e-mail containing your CV, a summary of your skills, description of your research interests, and a list of publications to Prof. Riitta Salmelin ( Please include names of two established scientists who may be contacted for reference; you may also arrange them to send a letter of reference directly by e-mail to the above address.

The salary starts around 3300 Euro/month, and it will increase with responsibilities, depending on the performance of the candidate. The position is available from Aug 1, 2010 for 2+1 years. Consideration of applications will begin immediately and will continue until the position is filled.

Riitta Salmelin, Academy Professor
Brain Research Unit
Low Temperature Laboratory
Aalto University
P.O. Box 15100
FI-00076 AALTO, Finland
tel. +358-9-47022950
fax +358-9-47023508

For express mail:
Puumiehenkuja 2 B
FIN-02150 Espoo, Finland

Thursday, February 4, 2010

Second Annual Neurobiology of Language Conference Announced

As announced at the first Neurobiology of language Conference in October (NLC2009), we are currently planning a second Neurobiology of Language Conference, which will be held on November 11-12 2010 in San Diego, California, as a satellite of the 40th annual meeting of the Society for Neuroscience.

Abstract submission for NLC2010 will open on May 1st 2010 and will close on June 1st 2010. Detailed guidelines for abstract submission are available at

If you are interested in joining the NLC 2010 Abstract Review Committee, please send an email at

Updated information about the scientific program, abstract submission, conference registration and venue will be posted on the conference website ( as it becomes available.

We look forward to seeing you in San Diego in November!


Pascale Tremblay, Ph.D., Postdoctoral Scholar, The University of Chicago
Steven L. Small, Ph.D., M.D., Professor, The University of Chicago

The NLC2010 organizing Committee:

Jeffrey Binder
Vincent Gracco
Yosef Grodzinsky
Murray Grossman
Peter Hagoort
Greg Hickok
Marta Kutas
Alec Marantz
Howard C. Nusbaum
David Poeppel
Cathy Price
Kuniyoshi L. Sakai
Riitta Salmelin
Sharon Thompson-Schill
Kate Watkins
Richard J S Wise

Wednesday, February 3, 2010

Brodmann's Map -- 101 years old

In celebration of the centenary of the publication of Korbinian Brodmann's famous map, Karl Zilles & Katrin Amunts have just published a great little piece on its history and current influence (too bad Nature Reviews Neuroscience couldn't have brought it to press in 2009). The paper highlights some interesting tidbits, like the influence of evolutionary theory on Brodmann's work, how Brodmann's map relates to those that followed, how it lost favor and how it was given new life with the advent of functional imaging. The paper even features an interview with Korbinian himself (fictitious, of course).

Beyond the interesting historical perspective, the article underscores the pitfalls associated with over-interpreting Brodmann areas in functional imaging studies, but also emphasizes the importance of anatomy in developing models of the organization of the cerebral cortex.

Zilles K, & Amunts K (2010). Centenary of Brodmann's map - conception and fate. Nature reviews. Neuroscience, 11 (2), 139-45 PMID: 20046193