On grandmother cells and parallel distributed models

Jeff Bowers has published a paper or two arguing for the viability of grandmother cells -- cells that represent whole "objects" such as a specific face (or your grandmother's face). At issue, of course, is whether the brain represents information in a localist or distributed fashion and Jeff has used his case for grandmother cells as evidence against a basic assumption of parallel distributed processing (PDP) models. But the PDP folks don't seem to think "distributed" is a necessary property of PDP models. So in the guest post below, Jeff asks, What does the D in PDP actually mean? This is an interesting question, and Jeff would like to know your thoughts (see the new survey to respond). I'd also be interested in your thoughts on grandmother cells!

Guest Post from Jeff Bowers:
I’ve been involved in a recent debate regarding the relative merits of localist representations and the distributed representations learned in Parallel Distributed Processing (PDP) networks. By localist, I mean something like a word unit in the interactive activation (IA) model – a unit that represents a specific word (like a “grandmother cell”). By distributed, I mean that a familiar word (or an object or a face, etc.) is coded as a pattern of activation across a set of units, with no single unit sufficient for representing an item (you need to consider the complete pattern). In Bowers (2009, 2010) I argue that the neuroscience is more consistent with localist coding compared to the distributed representations in PDP networks, contrary to the widespread assumption in the cognitive science community. That is, single-cell recordings of neurons in cortex and hippocampus often reveal neurons that are remarkably selective in their responding (e.g., a neuron that responds to one face out of many). I took this to be more consistent with localist compared to distributed PDP theories.

This post, however, is not with regards to whether localist or PDP models are more biological plausible. Rather, I’m curious as to what people think is the theory behind PDP models; specifically, what is your understanding regarding the relation between distributed representations and PDP models? In Bowers (2009, 2010) I claim that PDP models are committed to the claim that information is coded in a distributed format rather than a localist format. On this view, the IA model of word identification that includes single units to code for specific words (e.g., a DOG unit) is not a PDP model. Neither are neural networks that learn localist representations, like the ART models of Grossberg. On my understanding, a key (necessary) feature of the Seidenberg and McClelland model of word naming that makes it part of the PDP family is that it learns distributed representations of words – it gets rid of localist word representations.
However, Plaut and McClelland (2010) challenge this characterization of PDP models. That is, they write:

In accounting for human behavior, one aspect of PDP models
that is especially critical is their reliance on interactivity and
graded constraint satisfaction to derive an interpretation of an input
or to select an action that is maximally consistent with all of the
system’s knowledge (as encoded in connection weights between
units). In this regard, models with local and distributed representations
can be very similar, and a number of localist models remain
highly useful and influential (e.g., Dell, 1986; McClelland &
Elman, 1986; McClelland & Rumlehart, 1981; McRae, Spivey-
Knowlton, & Tenenhaus, 1998). In fact, given their clear and
extensive reliance on parallel distributed processing, we think it
makes perfect sense to speak of localist PDP models alongside
distributed ones. (p 289).

That is, they argue that the PDP approach is not in fact committed to distributed representations. Elsewhere they write:

In fact, the approach takes no specific stance on the number of units that
should be active in representing a given entity or in the degree
of similarity of the entities to which a given unit responds.
Rather, one of the main tenets of the approach is to discover
rather than stipulate representations (p. 286)

So on this view, the PDP approach does not rule out the possibility that a neural network might actually learn localist grandmother cells in the appropriate training conditions.

With this as background, I would be interested in people’s views on this. Here is my question:

Are PDP theories of cognition committed to the claim that knowledge is coded in a distributed rather than a localist format? [see new survey]

Thanks for your thoughts,

Jeff

References

Bowers JS (2009). On the biological plausibility of grandmother cells: implications for neural network theories in psychology and neuroscience. Psychological review, 116 (1), 220-51 PMID: 19159155

Bowers JS (2010). More on grandmother cells and the biological implausibility of PDP models of cognition: a reply to Plaut and McClelland (2010) and Quian Quiroga and Kreiman (2010). Psychological review, 117 (1) PMID: 20063980

Plaut, D., & McClelland, J. (2010). Locating object knowledge in the brain: Comment on Bowers’s (2009) attempt to revive the grandmother cell hypothesis. Psychological Review, 117 (1), 284-288 DOI: 10.1037/a0017101

Multiple Research Assistant/Fellowship Positions - U. Maryland, College Park

The Department of Linguistics at the University of Maryland, College Park, is looking to fill up to three full-time positions for post-baccalaureate researchers. Starting date for all positions is summer or fall 2010. Salary is competitive, with benefits included. The positions would be ideal for individuals with a BA degree who are interested in gaining significant research experience in a very active lab as preparation for a research career. Applicants must be US or Canadian citizens or permanent residents, and should have completed a BA or BS degree by the time of appointment. Previous experience in linguistics is required, and relevant research experience is preferred.

Applicants may request to be considered for all positions. Review of applications for all positions will begin immediately, and will continue until the positions are filled. For best consideration, completed applications should be received by April 20th.

Position #1: Research Assistant in Psycholinguistics/Cognitive Neuroscience

This person will take a leading role in research projects in psycholinguistics and cognitive neuroscience of language. The person will be involved in all aspects of the design, testing and analysis of studies of language comprehension in adults, using behavioral and neuroscientific techniques, including ERP and MEG brain recordings (training provided). The person will also play a key role in the management of an active lab group and will contribute to Maryland's IGERT training program in "Biological and Computational Foundations of Language Diversity". Previous experience in linguistics and/or psycholinguistics is preferred. The ability to interact comfortably with a wide variety of people (and machines) is a distinct advantage. The position is for a one year initial appointment, with the possibility of extension beyond that time. For more information contact Dr Colin Phillips, colin@umd.edu, (301) 405-3082. http://www.ling.umd.edu/colin

Positions #2-#3: Baggett Research Fellowships 2010-2011

One-year Baggett Fellowships are full-time positions intended for individuals with a BA or BS degree who are interested in gaining significant research experience in an active interdisciplinary environment before pursuing graduate study in some area of linguistics or cognitive science. One or two fellowship positions are available for the 2010-2011 year. Salary is competitive, with benefits included.

Applicants for all positions should submit a cover letter (outlining relevant background and interests, including potential faculty mentors), a current CV, and the names and contact information for 3 potential referees (letters are not needed as part of the initial application), and a writing sample. Fuller details athttp://www.ling.umd.edu/baggett. All application materials should be submitted electronically to Jeff Lidz (jlidz@umd.edu). NOTE: Put "Baggett Fellowship" in the subject line. Prospective fellows should fel free to send a preliminary letter of interest to Dr Lidz or Dr Phillips.
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The Cognitive Neuroscience of Language Lab is a well-integrated community of over 40 faculty, students and research staff, engaged in research on a wide variety of areas of language, ranging from acoustics to semantics, in children and adults, normal and disordered populations, and covering around 10 languages. The lab has facilities for behavioral testing of infants, children and adults, two eye-tracking labs, an ERP lab and a whole-head MEG facility. The lab is affiliated with the Department of Linguistics and with the Neuroscience and Cognitive Science Program.

http://www.ling.umd.edu/

The University of Maryland is an Affirmative Action/Equal Opportunities Title IX employer. Women and minority candidates are especially encouraged to apply.

Self-destruction of the mirror neuron theory of action understanding

Rizzolatti & Sinigaglia's new Nature Reviews Neuroscience paper on the mirror system is effectively an admission that the mirror neuron theory of action understanding is wrong. The original is idea was interesting: we understand actions by mirroring those actions in our own motor system. But this is no longer the case according to R&S:

By matching individual movements, mirror processing provides a representation of body part movement that might serve various functions (for example, imitation), but is devoid of any specific cognitive importance per se. p. 269

Instead, understanding comes from matching higher-order representations of the goals of the action (the quote above continues immediately):

By contrast, through matching the goal of the observed motor act with a motor act that has the same goal, the observer is able to understand what the agent is doing. p. 269

This goal-matching, according to R&S is quite independent of any specific motor act.

...among the neurons in various areas that become active during action observation, only those that can encode the goal of the motor behaviour of another individual with the greatest degree of generality can be considered to be crucial for action understanding... Indeed, parieto-frontal mirror neurons encode the goal of observed motor acts regardless of whether they are performed with the mouth, the hand or even with tools. p. 269

So, mirror neurons, those cells that fire during specific actions such as grasping-with-the-hand and while watching the same specific action -- the very cells that got everyone SO excited -- are not involved in action understanding. Rather, according to R&S, action understanding is achieved by cells that do not code for actions at all, but something higher level, goals/intentions.

It's worth noting that R&S directly contradict themselves in the sidebar definition of "Mirror-based action understanding":

The comprehension of an observed action based on the activation of a motor programme in the observer’s brain. p. 265

A motor program presumably controls a specific action, such as grasping-with-the-hand, not an action-independent goal or intention.

Is the mirror system needed for coding all goals and intentions? No, according to R&S:

This does not mean that the parieto-frontal mirror mechanism mediates all varieties of intention understanding. p. 271

But they want to say that the system IS needed for coding motor goals/intentions. They illustrate with an example:

Mary is interacting with an object (for example, a cup). According to how she is grasping the cup, we can understand why she is doing it (for example, to drink from it or to move it). This kind of understanding can be mediated by the parieto-frontal mirror mechanism by virtue of its motor chain organization. p. 271

It is true that we can make limited inferences about what Mary's intentions are by the way she grasps the cup. But (i) these inferences are underdetermined by the movement and (ii) motor experience with grasping cups is not necessary for making these inferences. Regarding (i), if Mary grasps the handle, rather than pushing the side with her fingertips, we may infer that she intends to drink rather than move. However, Mary could just as well be moving the cup, picking it up to put it in the sink, or picking it up to give to someone. Regarding (ii), simply having perceptual experience with grasping for drinking versus pushing for moving actions will result in the same inferential ability even without motor experience with cups.

Acknowledging the point that action understanding does not require the motor system, R&S site several studies that show that understanding can be achieved without the mirror system. They conclude,

These data indicate that the recognition of the motor behaviour of others can rely on the mere processing of its visual aspects. p. 270

So, to summarize:

1. Cells that mirror specific actions (i.e., congruent mirror neurons), don't support action understanding.
2. The real work of action understanding is done by cells that abstract away from actions and instead code goals and intentions.
3. Intentions can be coded outside the mirror/motor system.
4. The recognition of actions of others can be achieved outside the mirror/motor system.

So what does the mirror system contribute?

...[it] allows an individual to understand the action of others ‘from the inside’ p. 264

What does "from the inside" mean to R&S?

...the observed action is understood from the inside as a motor possibility and not just from the outside as a mere visual experience. p. 270

In other words, it is the "understanding" that I-can-do-that-too and nothing more.

Rizzolatti, G., & Sinigaglia, C. (2010). The functional role of the parieto-frontal mirror circuit: interpretations and misinterpretations Nature Reviews Neuroscience, 11 (4), 264-274 DOI: 10.1038/nrn2805

Post-docs at NYU/NYU-AD

1. Postdoctoral Position

Cognitive Neuroscientist
Neuroscience of Language Laboratory
Departments of Linguistics and Psychology

NYU & NYU Abu Dhabi

A 1-year, potentially renewable post-doctoral position in the cognitive neuroscience of language is available for the NYU Abu Dhabi Neuroscience of Language Laboratory. The researcher will have had experience with evoked response experiments using either MEG or EEG, but preferably both. The main responsibility of the researcher will be to explore the appropriate ways to utilize participant populations of varied linguistic and educational backgrounds to address questions about linguistic universals and language-specific effects. Working with Arabic and East Asian speakers requires nuanced understanding of the linguistic situation on the ground as well as a search for necessary corpus resources and area experts on the languages and language-particular psycholinguistics. A researcher with cross-linguistic experimental experience would be ideal for the job, and someone from either the Gulf area or India would be especially suited for this project.

To apply, please send a copy of your CV and a brief statement of research interests and goals to Christine Boylan at linguistics.neurolab@nyu.edu.


2. Postdoctoral Position

Computational Researcher
Neuroscience of Language Laboratory
Departments of Linguistics and Psychology

NYU & NYU Abu Dhabi

A 1-year, potentially renewable post-doctoral position in computational research is available for the NYU Abu Dhabi Neuroscience of Language Laboratory.

The successful applicant will have had an extensive background in quantitative analysis, statistics, and/or electrophysiological signal processing. The researcher will be responsible for the laboratory’s data processing pipeline, from experimental design through final data analysis, and will create and justify statistical tools for neurolinguistic experiments with MEG/EEG data. Though the researcher is expected to work with source localization packages such as MNE and BESA, he/she will be most concerned with issues essentially statistical in nature, e.g. the covariance of stimulus variables, the way to treat data across subjects, the problem of multiple comparisons in whole-brain and whole-epoch analyses, etc.

To apply, please send a copy of your CV and a brief statement of research interests and goals to Christine Boylan at linguistics.neurolab@nyu.edu.

RA/Lab Manager Positions at NYU in Neurolinguistics

Via Alec Marantz & Liina Pylkkänen:

We have two positions here at NYU between Linguistics and Psychology for next year ideally suited for someone in transition between an undergraduate degree or an MA and a PhD program in linguistics, psychology, or neuroscience. Please distribute the advertisement to students that might be interested, and please don't hesitate to let us know about anyone we might contact directly to persuade to apply.

Thanks,
Liina Pylkkänen & Alec Marantz
Departments of Psychology and Linguistics, NYU


1. Lab Manager/Research Assistant Position

A full-time Lab Manager position is available at the NYU Neurolinguistics Laboratory, with some responsibilities extending to the NYU Abu Dhabi Neuroscience of Language Laboratory, currently under construction. A BA/BS or MA/MS in a cognitive science-related discipline (psychology, linguistics, neuroscience, etc.) or computer science is required. The lab manager will be involved in all stages of the execution and analysis of MEG and EEG experiments on language processing. Previous experience with MEG or some other cognitive neuroscience method is highly preferred. A background in statistics and some programming ability (especially Matlab) are essential.

Preferred start date is July 2010, but this is negotiable. Salary and rank will be commensurate with experience. To apply, please email CV and names of references to Prof. Liina Pylkkänen (liina.pylkkanen@nyu.edu).

Contact Information:

email: liina.pylkkanen@nyu.edu

Tel: (212) 992-8764 or (212) 998-8386

http://www.psych.nyu.edu/pylkkanen/lab/


2. Research Assistant

Full-time NSF-funded research assistant for Cognitive Neuroscience of Language projects at the KIT/NYU MEG Lab. BA/BS in cognitive science-related discipline (psychology, linguistics, etc.) or computer science. Programming and/or statistics experience a plus.

RA would help analyze data from MEG and joint MEG/fMRI experiments and help design and program additional experiments. For 2010-11, research will concentrate on lexical access and morphological decomposition in auditory and visual word perception.

Preferred start date is July 2010, but this is negotiable. Salary and rank will be commensurate with experience. To apply, please email CV and names of references to Prof. Alec Marantz (marantz@nyu.edu).

Contact Information:

email: marantz@nyu.edu

Tel: (212) 998-3593

http://www.psych.nyu.edu/meglab/

Mirror neurons support action understanding -- "from the inside"?

I think we are getting closer to understanding what mirror neurons are doing. No longer is it claimed that mirror neurons are THE basis for "action understanding". Now, according to Rizzolatti & Sinigaglia's new review (2010), there are several non-mirror mechanisms that can accomplish this:

We conclude that, although there are several mechanisms through which one can understand the behaviour of other individuals...

Mirror neurons do something else (R&S would probably prefer the term, more, but else is better I think)

the parieto-frontal mechanism is the only one that allows an individual to understand the action of others 'from the inside'

Let me explain what "from the inside" means, or at least provide an alternative to whatever R&S mean by it. In my "Eight Problems" paper (Hickok, 2009) I noted that I can understand the action of saxophone playing even though I've never performed the actions associated with saxophone playing. R&S acknowledge that, indeed, I do understand the action of saxophone playing, and do so without the benefit of mirror neurons. But they suggest my understanding is lacking something, namely that extra bit of knowledge that comes from knowing how to play a saxophone. So recognizing an action that I know how to perform = basic action understanding from non-mirror systems + mirror neuron-driven knowledge that hey I know how to make MY motor system do that!

In other words, mirror neurons support the knowledge of how to perform an action that one is observing -- that is, mirror neurons are part of the same old "how" stream that vision neuroscientists, and more recently auditory neuroscientists have been working on for more than a decade (Milner & Goodale, 1995). The "how" stream, of course, supports sensory-motor integration, or in R&S's terms, action understanding "from the inside". This is why you see motor activation during the perception of actions that you can perform: it is sensory-motor association.

Importantly, notice that there is no magical semantic knowledge that suddenly falls from heaven when we know how to perform an action. I can teach you a new word, glemph, and you can learn to reproduce it with your vocal tract so that subsequent presentations of acoustic glemph will activate your motor system by association. I could do the same with a sign language gesture. It doesn't take on meaning until you link the sensory-motor ensemble to a conceptual structure. So for example, I could define glemph (or the sign language equivalent) as 'the act of publishing on the topic of mirror neurons'. Now, the sensory-motor ensemble has meaning and you understand it, but does that mean that the meaning and the understanding is now suddenly coded or even augmented by the sensory-motor ensemble itself? Put differently, do you now have a different understanding of the concept, 'the act of publishing on the topic of mirror neurons' just because you have a new sensory-motor associate of the concept? No, you just know how to articulate the word that is associated with the concept.

I suggest that this interpretation of "understanding from the inside" explains every mirror neuron-related observation, does so more parsimoniously than Rizzolatti's account, and has more empirical support from research on aphasia and apraxia.

References

Hickok G (2009). Eight problems for the mirror neuron theory of action understanding in monkeys and humans. Journal of cognitive neuroscience, 21 (7), 1229-43 PMID: 19199415

Milner, A.D., and Goodale, M.A. (1995). The visual brain in action, Oxford: Oxford University Press.

Rizzolatti, G., & Sinigaglia, C. (2010). The functional role of the parieto-frontal mirror circuit: interpretations and misinterpretations Nature Reviews Neuroscience, 11 (4), 264-274 DOI: 10.1038/nrn2805

Mirror Neurons - The unfalsifiable theory

I recently had the pleasure of giving a lecture on mirror neurons at UC San Diego which is a very active locale for folks working on the human mirror system. I expected a lot of push-back on my critical views of mirror neurons, and I wasn't disappointed.

One of my major points of emphasis is and has been that if the mirror neuron system is really important for action understanding, then damage to action execution should result in action understanding deficits. I have pointed out that this prediction doesn't hold, either in apraxia or with more force in aphasia.

A typical response to this argument is that "the mirror system" involves lots of areas working together (George Lakoff, who was at the UCSD lecture even seemed willing to include the STS in this network) and so it is no surprise that damage to fronto-parietal areas doesn't result in the expected action understanding deficits. Along these lines, some folks pointed out that mirror responses have now been found in lots of brain areas, not just the frontal and parietal areas where they have been documented in monkeys. In other words, the mirror system is expanding.

At this point in the talk, Pat Churchland, who was my host, jumped in and said (and I paraphrase here), "Now wait a minute. If mirror neurons are all over the brain then don't they lose their explanatory power? Aren't we now just back to our old friend, the How Does the Brain Work Problem?" Very true, I think.

I ran into this same issue in my debate with Fadiga at the Neurobiology of Language Conference in Chicago. I said, here are several examples of preserved speech perception in the face of an absence of speech production ability, and the mirror neuron proponents said basically, it's a large system that's too complicated to succumb to the loss of the motor system.

A new review by Rizzolatti and Sinigaglia (2010) also pushes back against some of the critiques that have been raised lately. One concerns the observation that mirror responses in a TMS paradigm can be re-trained such that they no longer mirror and dissociated from understanding. RS: "The reason is that, in the task, there was nothing to understand: the investigated movements were meaningless." Another is the "surprising" claim (mine) that damage to the fronto-parietal motor system should be associated with deficits in action understanding. RS:" As clearly shown by electrophysiological mapping, there are motor sectors in the monkey inferior parietal lobule (and even in area PFG) with and without mirror neurons. Thus, dissociations between motor deficits and action understanding deficits can and do occur." Wait, I thought the mirror system got is magical powers from being part of the motor system. If the motor system is functionally disrupted, shouldn't the action understanding system also be disrupted? Or is there a parallel mirror motor system that can't control movement but can understand action (kind of sounds like a sensory system to me).

I think the mirror neuron folks have a serious problem on their hands: there is apparently no empirical result that can falsify the theory. If a mirror neuron shows up in an unexpected place, it is a new part of the mirror system. If a mirror neuron's activity dissociates from action understanding, it was not coding understanding at that moment. If damage to the motor system doesn't disrupt understanding, it is because that part of the motor system isn't mirroring.

Can someone from the mirror neuron camp come forward and provide us with an example of what kind of empirical result would falsify the theory? Because if you can't falsify it, it's no longer a scientific theory, it's religion.

Rizzolatti G, & Sinigaglia C (2010). The functional role of the parieto-frontal mirror circuit: interpretations and misinterpretations. Nature reviews. Neuroscience PMID: 20216547

Mis-localization of fMRI activation at the temporal-parietal boundary

In the many fMRI studies we have now done looking at sensory-motor integration for speech and related functions we have repeatedly observed that sensory-motor area Spt (i) shows up more robustly in individual subjects than in group averages and (ii) localizes to the posterior planum temporale region in individual subjects but sometimes localizes to the inferior parietal lobe in group averaged normalized data.

The results below are an example of this (data represent the work of my graduate student, Lisette Isenberg). This is a study involving 17 subjects performing a listen->covert repeat task (~shadowing) minus a listen_only condition. Data were warped to Talairach space following typical procedures and projected onto a template brain (left image below). Notice that the focus of activation is relatively small and squarely on the supramarginal gyrus. When we looked at individual subjects, however, there was no activation in the SMG but rather it was consistently ventral to this in the Sylvian fissure.



The image on the right uses ANTS (Advanced Normalization ToolS) which performs a diffeomorphic transformation to align the images based on anatomical features. The structural image you see here (right) is actually the 17 brains of the participants nicely aligned to each other. With their sulci and gyri neatly aligned, the activation in the right image is now substantially larger (functional regions are lining up better) and correctly localized to the posterior Sylvian region.

What seems to happen is that the standard template brains have a Sylvian fissure that is sometimes too flat compared to sample population, which can slope up more at the posterior boundary. Activations at the posterior margin then, as in Spt activations, end up mis-localizing to the parietal lobe. ANTS alignment seems to solve the problem though.

For this reason, anytime someone reports an SMG or inferior parietal lobe activation, I question whether it might actually be in the posterior Sylvian fissure.

Phonemic segmentation in speech perception -- what's the evidence?

It is a commonly held belief that speech perception involves the recovery of segmental information -- that is, the speech stream is analyzed in such a way that individual phonemes are recovered. So a typical story is that we analyze the spectro-temporal features to recover phonemes which are put together to form syllables then phonological words, enabling lexical-semantic access. We've suggested, as have others, that maybe the syllable is a basic unit of analysis, while at the same time leaving open the possibility that we might also access segmental information. For example, as in this figure from Hickok & Poeppel 2007:



Or this overly simplified cartoon from Hickok 2009:



So here's the question, what exactly is the evidence that we access segmental information in perception? Do we even need phonemes for speech perception? Why?

Let me play devil's advocate and claim that we don't extract or represent phonemes at all in speech perception (production is a different story). We do it all with syllables.

Convince me that I'm wrong.


Hickok, G. & Poeppel, D. (2007). The cortical organization of speech processing. Nature Reviews Neuroscience, 8, 393-402

Hickok, G. (2009). The functional neuroanatomy of language. Physics of Life Reviews, 6, 121-143.

Post-doc at USC: University of South Carolina, Columbia

A post-doctoral position is available in the Department of Communication Sciences and Disorders at the University of South Carolina (Columbia, SC, USA). Prospective hires will join a research team headed by Julius Fridriksson (www.sc.edu/comd/fridriks) whose lab is funded by two R01 grants from the NIH. The primary research focus of the lab is as follows: 1) neural basis of speech/language processing with special emphasis on brain plasticity; and 2) neurophysiology of aphasia recovery. This research relies on a range of methodologies such as functional and structural MRI, lesion-symptom mapping, transcranial magnetic stimulation (TMS), and transcranial direct current stimulation (tDCS). The University of South Carolina has a Siemens Trio MRI scanner that is primarily devoted to research and we have access to a state-of-the-art TMS setup. Columbia is centrally located in South Carolina, within a two-hour drive to the beach and the mountains. The weather in Columbia is marked by “Southern” Summers, and a mild Autumn, Winter, and Spring. The salary level for this position is very competitive but will be commensurate with experience and previous scholarship. The ideal applicant for the position will work as a part of a research team as well as have the chance to initiate and carry out independent projects. If interested, please contact Julius Fridriksson at fridriks@mailbox.sc.edu

Not on mirror neurons: Who's stuff do I have to read this week?

David Gow has published a series of papers on the cortical basis of speech perception using pretty sophisticated analytic tools that do not often get applied to the type of data we are used to.

For example, in this Cognition paper: "Articulatory mediation of speech perception: A causal analysis of multi-modal imaging data" (2009) by Gow and Segawa, Granger causality analyses are used to support the Motor Theory.

And in this NeuroImage paper: "Lexical influences on speech perception: A Granger causality analysis of MEG and EEG source estimates" by Gow, Segawa, Ahlfors, and Lin (2008), top-down effects demonstrated by Granger causality analysis appear to have a lexical origin and compelling effects on phonetic perception. This is a longstanding battle in spoken word recognition, and I'm pretty enthused to see new data of this type addressing this controversy.

Common to some of David's recent work is a demonstration of the pretty compelling contribution of top-down factors in the analysis of the speech signal. One thing that is a little less obvious is why these top-down effects should have the supramarginal gyrus as a critical ingredient. It's my homework this week to work through these papers in sufficient detail to really get my head around them. I am already predisposed to the top-down part, but I do need to understand why the SMG would be the critical node. What's really impressive is the thoughtful integration of EEG, MEG and MRI data.

David, if you're reading this, it would be great to get a bit of discussion going on this issue. For example, how deeply held is your commitment to the SMG? Did you guys find any data that challenge that conclusion, or are you willing to bet something substantial?

MEG job in Montreal -- a really good one!

The Montreal Neurological Institute of McGill University Faculty Position in Brain Imaging

The Montreal Neurological Institute (MNI) of McGill University is conducting an international search for a magnetoencephalography (MEG) Scientist to lead the MEG program within the McConnell Brain Imaging Centre (BIC). The MNI is a broad-based neuroscience research institute integrated with the Montreal Neurological Hospital and is part of one of the largest and most diverse neuroscience communities in North America. The BIC (www2.bic.mni.mcgill.ca) is a large multi-disciplinary neuro-imaging research centre with 15 faculty members, 40+ affiliated faculty members, 25 technical staff members and approximately 100 graduate students and postdoctoral fellows. BIC research-dedicated facilities include state-of-the-art human MRI/fMRI and PET scanners, animal MRI and PET, cyclotron and radiochemistry labs, and large scale computing facilities. The BIC is now expanding to include an MEG program based upon secured equipment and construction funding provided by the Canada Foundation for Innovation and private donors.

We seek applications for a tenure track faculty position as an MEG scientist. Applicants should have a PhD, MD, or the equivalent, and advanced training and experience with MEG methods, instrumentation and neuroscience applications. They should also have an established track record in obtaining research funding, teaching and working in a collaborative multi-disciplinary environment. The new recruit will be expected to establish and lead the MEG laboratory and to develop a successful research program of basic and clinical neuroscience.

We offer highly attractive salary and start-up packages and an exceedingly high quality of life in Montreal, one of North America's greatest and most lively cities. Applications should consist of a PDF file containing a letter outlining current and future research interests, CV, and the names and addresses of three references. Completed PDF files should be addressed to Dr. Robert Dunn, Associate Director Scientific Affairs at megsearch.mni@mcgill.ca and must be received by February 28, 2010. Applications will be evaluated as they are received. More information can be found at www.mni.mcgill.ca.

All qualified applicants are encouraged to apply; however, Canadians and permanent residents will be given priority. McGill University is committed to equity in employment and diversity. It welcomes applications from indigenous peoples, visible minorities, ethnic minorities, persons with disabilities, women, persons of minority sexual orientations and gender identities and others who may contribute to further diversification.