Friday, February 29, 2008

Talking Brains Live in Cardiff and London

Just a quick report on my mini (whirlwind) tour to the UK.

University of Cardiff. First stop was in Wales -- homeland of Katherine Zeta-Jones, I learned -- in the capitol city of Cardiff. There I gave a talk at the School of Psychology. The School is impressively large, taking up an entire multistory building, plus a few other bits of space. AND they've got an equally impressive brand new, within-school center for brain imaging, the Cardiff University Brain Research Imaging Centre (CUBRIC), which houses all the tools of the trade: fMRI, MEG, EEG, and TMS. I had a nice chat there with Derek Jones, who has been doing some very interesting DTI work on language-related fiber (or shall I say, fibre) pathways. E.g., check out Catani et al. (2005), Ann. Neurology, 2005 Jan;57(1):8-16. Keep your on eye of research coming out of this place in the near future!

I spent most of my time, however, hanging out with Dylan Jones (pictured on right) and Bill Macken (pictured on left). These guys have been promoting, for some time now, the idea that Baddeley's phonological store, is neither phonological nor a much of a store (in the sense of a separate buffer or module). And they've got some pretty nice behavioral data to back it up. They suggest instead that, "A reformulation of short-term memory theory needs to embody (or indeed focus exclusively upon) perceptual and effector systems rather than bespoke storage modules" (Jones et al. 2007, Q J of Exp Psy 60:505-11). I completely agree, and have proposed a similar view (although without fancy words like "bespoke") on the basis of our fMRI findings. Have a look at anything authored by former TB West grad student, now D'Esposito/Berkeley post doc, Brad Buchsbaum, for details on our view. More importantly however, Dylan and Bill are very entertaining hosts. I highly recommend a visit!

Wellcome Trust Centre for Neuroimaging, University College London. After leaving an up-and-coming center (oops, centre) for functional imaging, I headed to a one of the most well-established and productive centres, the Functional Imaging Lab in Queen Square, London. Here I had the great pleasure of meeting (for the first time!) Cathy Price. Cathy, of course, is one of the superstars of language neuroscience, generating tons of important publications (did I seriously count 19 pubs in 2005, Cathy?), including some very nice and highly cited review papers. Basically, you need to read pretty much everything that comes out of Cathy's lab. I have always admired her work, but now, after hanging out for a few hours with Cathy and some of her colleagues and students, I can say in addition that she is one of my favorite people in the field. Hmmm... We could use a Talking Brains London... Ever blog before, Cathy? ;-)

While in London, I also had a chance to have coffee with Celia Heyes and Caroline Catmur, who authored a recent paper on mirror neurons that I highlighted in a Scientific American blog. Celia has been studying imitation since long before the mirror neuron craze made it a hot topic, and has produced an impressive body of work. Caroline is a grad student working with Celia who is just finishing up an fMRI study related to their TMS-based mirror neuron paper. We had a nice discussion, and found that we essentially had the same views on the nature of the mirror system. I'm looking forward to seeing their fMRI paper in print! Oh, and if anyone is needs a good post doc, Caroline will be on the market soon!

Thanks much to my hosts at both locales for a great trip!

Wednesday, February 27, 2008

UC Irvine Workshop on the Evolution of Psychological Categories

Some interesting talks if you happen to be in the area. Follow the link below for more information.

Title: "The Evolution of Psychological Categories"
Event Dates: 3/14/2008 - 3/16/2008
Location: SSPA 2112 Luce Conference Room
AGENDA link: http://www.imbs.uci.edu/CONFERENCES/2008/080314%20Evol.%20Psy%20Categ/AGENDA.htm

Description: How do individuals learn language and semantic systems? What features of language categories are shared by communicating individuals? How do language and meaning evolve over time in human and artificial individuals, and in groups? These are some of the questions that this IMBS workshop will address through presentations and discussion on topics of learning; language evolution; semantic cognition; and how individuals and groups construe meaning. The meeting will be multidisciplinary, bringing together experts from the diverse areas of Psychology and Cognitive Science, Mathematical Behavioral Science, Logic and Philosophy of Science, Computer Science & Statistics, Evolutionary Dynamics, and Mathematics. During this meeting we will focus on the formalization of these listed topics, using approaches from neural and artificial systems modeling, Bayesian modeling, computational and statistical psychology, mathematics and evolutionary game theory. Expect the presentations to range from the empirical to the theoretical and mathematical.

Featured presenters include:
Paul Kay, Linguistics, UCB
Terry Regier, Psychology, University of Chicago
Greg Ashby, Psychology, UCSB
Tom Griffiths, Pyschology, UCB
Partha Niyogi, Computer Science, University of Chicago
Luc Steels, SONY, Paris
Jay McClelland, Psychology, Stanford
Kimberly Jameson, Mathematical Behavioral Sciences, UCI
Natalia Komarova, Mathematics, UCI
Michael Lee, Psychology, UCI
Andrea Baronchelli, Universitat Polithcnica de Catalunya
Vittorio Loreto, Universita di Roma
Lisa Pearl, Cognitive Sciences, UCI
Rory Smead, Logic and Philosophy of Science, UCI

Tired of Mirror Neurons yet?

J. Neuroscience has a "Journal Club" article on M1 activity during action perception. I haven't looked at it in detail yet, but you can check it out here:

Action-Coding Neurons in Primary Motor Cortex: Making Sense of M1 Activity
during Action Perception
Jean-Francois Lepage, Melissa Lortie, and Francois Champoux
J. Neurosci. 2008;28 1995-1996
http://www.jneurosci.org/cgi/content/full/28/9/1995?etoc

Btw, my teaching duties next quarter include a grad course on mirror neurons. I'll simulcast that course here as well. Should be fun.

P.s., still intend to post comments on the SD readings, but gotta get a grant resubmitted first!

Tuesday, February 26, 2008

Semantics and Brain -- Reading set #7

The goal with these readings to determine whether aphasics have "semantic" deficits that are, or can be, modality/language specific. In other words, is there any evidence to support the Hickok/Poeppel claim that the posterior MTG region is performing a sound-to-meaning mapping function? My prediction is that it should be possible to find aphasic patients who have semantic deficits in language comprehension and production, but do much better with say visually presented stimuli. Or are semantic deficits in aphasia amodal?
Goodglass H, Baker E.
Semantic field, naming, and auditory comprehension in aphasia.
Brain Lang. 1976 Jul;3(3):359-74.
Gainotti G, Miceli G, Caltagirone C.
The relationships between conceptual and semantic-lexical disorders in aphasia.
Int J Neurosci. 1979;10(1):45-50.

Caramazza A, Berndt RS, Brownell HH.
The semantic deficit hypothesis: perceptual parsing and object classification by
aphasic patients.
Brain Lang. 1982 Jan;15(1):161-89.

Butterworth B, Howard D, Mcloughlin P.
The semantic deficit in aphasia: the relationship between semantic errors in
auditory comprehension and picture naming.
Neuropsychologia. 1984;22(4):409-26.

Hart J Jr, Gordon B.
Delineation of single-word semantic comprehension deficits in aphasia, with
anatomical correlation.
Ann Neurol. 1990 Mar;27(3):226-31.

Chertkow H, Bub D, Deaudon C, Whitehead V.
On the status of object concepts in aphasia.
Brain Lang. 1997 Jun 15;58(2):203-32.
Goodglass H, Wingfield A, Ward SE.
Judgments of concept similarity by normal and aphasic subjects: relation to
naming and comprehension.
Brain Lang. 1997 Jan;56(1):138-58.

Syntactic and phonological abilities in semantic dementia

One of the big take-home messages from the last set of readings on semantic dementia, is that these patients indeed seem to have relatively spared syntactic and phonological abilities. In one case, reported by Saffran & Schwartz (1994), the patient could perform grammaticality judgments, showed a normal advantage for structured over scrambled sentences in a word monitoring task (but was insensitive to semantically anomalous items unlike controls), and was able to use syntactic information to identify noun referents. McCarthy & Warrington (2001, Neurocase, 7:77-87) report another case in which semantic knowledge was severely affected, yet digit span was normal, and in a variety of repetition tasks showed normal sensitivity to phonological factors and lexicality, but insensitivity to semantic factors. Detailed reports like these, coupled with the more standard language assessment tests reported in the group studies we’ve read over during the last few weeks, strongly suggests that syntactic and phonological abilities are relatively spared in SD patients.

Monday, February 25, 2008

JUST SAY NO to methods-at-the-end journals

At least that's what more than 70% of our poll respondents said when asked if they like the methods-last format. Of course, our sample of Talking Brains readers may not be entirely unbiased, but it doesn't matter because... their right.

Methods at the end makes no sense. What is the argument for organizing articles this way? Well, some people don't read the methods, and it is very inconvenient to flip a page or two to get past them, so let's put them at the end. Seriously? Just leave the article in its proper order for those of us who want to read the whole article, and if someone wants to skip the methods, a simple flip is all is takes.

Research Positions in Language at Maryland (post-doc & post-bac levels)

Post-doctoral position in Psycholinguistics/Neurolinguistics/Language 
Acquisition
University of Maryland

The Cognitive Neuroscience of Language (CNL) Lab at the University of
Maryland at College Park (suburb of Washington DC) is looking for a
postdoctoral researcher to participate in all aspects of research.
The CNL Lab comprises around 40 faculty, staff, and students engaged
in research that spans language acquisition, language processing, and
neurolinguistics, including the study of acquired and genetic
disorders. The lab has on-site facilities for whole-head MEG
recordings, high-density EEG, head-mounted and stationary eye-
trackers, and a variety of behavioral paradigms. Lab members have
access to an on-campus laboratory preschool and infant testing
facilities. Lab members have also conducted fMRI and PET studies
through local collaborations. CNL Lab faculty include Valentine
Hacquard, Bill Idsardi, Jeff Lidz, Colin Phillips, David Poeppel, Amy
Weinberg, and Andrea Zukowski, and there are close ties to labs in
Psychology, Computer Science, Hearing & Speech Science, Electrical
Engineering, and Second Language Acquisition. The post-doc position
is not linked to a specific project, and the ideal candidate will be
able to contribute to more than one of the lab's research foci and to
the Department of Linguistics' other strengths in theoretical and
computational linguistics. This is primarily a research position, but
some limited teaching may be required. Initial appointment is for 1
year, with the possibility of renewal for a second year. Anticipated
starting date is September 1, 2008, and PhD should be in hand by
starting date. Salary is competitive. For best consideration, submit
a letter of application and current CV, and arrange for 3 references
to be submitted electronically.

Inquiries may be directed to any CNL Lab faculty member. Please note
that all application materials, including letters of recommendation,
should be submitted electronically if at all possible (PDF files
preferred). Application materials should be sent to Bill Idsardi,
idsardi@umd.edu. The last-resort mailing address is: CNL Post-doc
Search, c/o Bill Idsardi, Department of Linguistics, 1401 Marie Mount
Hall, University of Maryland, College Park, MD 20742. Review of
applications will begin on March 24th, but the position will remain
open until filled.
=======================================================================
Multiple Research Assistant/Fellowship Positions

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 2008. 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 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 March 14th.

Position #1: Research Assistant in Cognitive Neuroscience of Language

This person will take a leading role in research projects on the
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. 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 2008-2009

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 2008-2009 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 at http://
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. Prospective fellows who are currently applying to MA and
Ph.D. programs should indicate this in their application, and should
inform us if they accept an offer from a graduate program and wish to
withdraw their application.
=======================================================================
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 children and adults, two eye-tracking labs,
a high-density ERP lab and a whole-head MEG facility. The lab is
affiliated with the Departments of Linguistics and Biology, 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.
=======================================================================

Tuesday, February 19, 2008

Talking Brains Live -- UK Mini Tour

For those of you in the Cardiff or London areas who might want to grill me in person, here's your chance. I'll be giving talks at Cardiff University (Psychology) and University College London (FIL) on Thursday, Feb. 21 and 22 respectively. Thanks to London-based "Jerry" for coming up with the tongue-in-cheek, "TB Live" title for the visit. So if my laptop crashes, or the projector fails on me, maybe we could call it "Talking Brains Unplugged"? :-) It should be a really fun visit at both locales. I'm looking forward to it!

Comments on our semantics and brain readings still forthcoming... Will work on a few blog entries during the flight -- after I get my talk done, that is. ;-)

Wednesday, February 13, 2008

Semantics and Brain course - reading set #6

We're getting a bit tired of reading about semantic dementia (as interesting as it is), so for our next meeting we will be reading papers on semantic memory/organization in the brain that aren't necessarily derived from SD research. Our next meeting will be Monday Feb. 25, so commentaries on these papers will appear after that date. (Comments on the last set of readings will start appearing this week...)

There are 7 papers here, representing (hopefully) a range of ideas. We will start with one of my favorite theorists on the neural organization of semantic memory: Carl Wernicke. Yes, that's right, he didn't just do language. Although Wernicke hinted at his views on the topic in his classic language writings, his most thorough description of his theory was published in 1900 in a volume titled, Grundriss der Psychiatrie. This volume has not been translated into English except for a few portions which appear in Gage & Hickok (2005). Skip the commentary and just read the excerpts -- I think you will find Wernicke's ideas to be extremely modern-sounding.

Gage N, Hickok G.
Multiregional cell assemblies, temporal binding and the representation of
conceptual knowledge in cortex: a modern theory by a "classical" neurologist,
Carl Wernicke.
Cortex. 2005 Dec;41(6):823-32. Review.

Saumier D, Chertkow H.
Semantic memory.
Curr Neurol Neurosci Rep. 2002 Nov;2(6):516-22. Review.

Caramazza A, Mahon BZ.
The organization of conceptual knowledge: the evidence from category-specific
semantic deficits.
Trends Cogn Sci. 2003 Aug;7(8):354-361.

Thompson-Schill SL.
Neuroimaging studies of semantic memory: inferring "how" from "where".
Neuropsychologia. 2003;41(3):280-92. Review.

Patterson K.
The reign of typicality in semantic memory.
Philos Trans R Soc Lond B Biol Sci. 2007 May 29;362(1481):813-21. Review.
Martin A.
The representation of object concepts in the brain.
Annu Rev Psychol. 2007;58:25-45.

Hart J Jr, Anand R, Zoccoli S, Maguire M, Gamino J, Tillman G, King R, Kraut
MA.
Neural substrates of semantic memory.
J Int Neuropsychol Soc. 2007 Sep;13(5):865-80. Review.

Job Posting: Research Scientist in Acquired Disorders of Language/Communication

Moss Rehabilitation Research Institute (MRRI) is seeking to fill an opening
in Fall ¹08 or later for an Institute Scientist in the area of acquired
disorders of language and/or communication. This is a full-time research
position at the equivalent of Assistant or Associate Professor level. The
new Institute Scientist will join a productive team of investigators who
study cognitive neuroscience, cognitive rehabilitation, and motor
control/motor learning. Language and aphasia are particular strengths of
MRRI, as represented by the active research program led by Myrna Schwartz
and the multi-faceted activities of the MossRehab Aphasia Center, directed
by Ruth Fink.

The candidate should have research experience in a topic related to human
language and/or communication after CNS damage. While area of
specialization is open, preference will be given to investigators who
complement our faculty¹s interest in one or more of the following: models of
(re)learning relevant to rehabilitation, techniques for promoting brain
plasticity, and model-driven diagnosis and treatment. A large pool of
patient volunteers with communication disorders secondary to stroke and TBI
is available for subject recruitment. MossRehab, our sister facility and
one of the nation¹s leading rehabilitation hospitals, offers a venue for
clinical trials research. Access to fMRI, TMS, ERP, and voxel-based
lesion-symptom mapping is available through existing collaborations with the
University of Pennsylvania¹s Center for Functional Neuroimaging.

Candidates must have a Ph.D. in a relevant area. Post-doctoral training,
evidence of research productivity, and prior grant funding are highly
desirable, as salaries and labs at MRRI are largely grant supported. A
multi-year start-up package is available to facilitate extramural funding.

Interested candidates should submit a cover letter, CV, and 3 letters of
reference to Kevin Whelihan, Administrator, MRRI, MossRehab @ Elkins Park,
60 E. Township Line Road, 2nd Floor West Building, Elkins Park, PA 19027 or
whelihank@einstein.edu. Applications will be accepted until the position is
filled.

Thursday, February 7, 2008

Semantics and Brain - Comment on Hodges et al. 2000 - object use in SD

As I mentioned previously, one problem with the claim the semantic dementia involves an amodal semantic deficit is that the vast majority of the tests use visual, auditory, and language related measures, all of which rely on temporal lobe systems. And as Johnathan Peelle suggested in a comment, most of the stimuli in these tests seem to be weighted toward visually-based concepts (camels, pyramids, etc.), ie, things you can draw or make picture judgments on. If similar semantic deficits could be demonstrated in a modality that is not so visual, auditory, or language based, the case for a truly amodal deficit would be much stronger.

In support of this idea are anecdotal observations that SD patients, despite severe semantic deficits, can nonetheless engage in hobbies, cook, and demonstrate correct object use even for objects that they fail to name or provide correct semantic judgments on.

Hodges et al. (2000, Brain, 123:1913-25) put these anecdotal observations to a rigorous test in an attempt to provide evidence for the amodal semantic deficit idea. They asked SD patients to demonstrate the use of various real objects. Patients were impaired, and performance on the object use task was correlated with the patient's semantic assessment measures. The authors conclude that the patients' deficits arise from disruption of a common semantic system that affects recognition, naming, ... and object use. They explain the apparent preservation of object use in anecdotal reports to "affordances, problem solving, available context, etc." p. 1923.

Does this prove that the deficit is amodal? No.

Problem #1: The task has a strong visual component.

If they are having trouble recognizing the objects because of degraded visual-object representations, they might have trouble knowing what to do with them. But, you might ask, they are touching the objects too, why can't they recognize by touch? They should be able to, but only if the objects were fully explored tactilely (and it is not clear they were), and are familiar to the subject by touch alone. If you look through the list of objects, many of them are very similar tactilely on their grasping region: bottle opener, toothbrush, pencil, whisk, hairbrush, spoon, hammer, potato peeler are all objects that have handles and would be difficult to differentiate if only the handle was grasped. Other objects, such as a pencil sharpener and a corkscrew (depending on the type) -- two objects that generated many errors -- may be hard to identify by touch.

But if this is right, wouldn't patients be expected to have the same trouble in their hobbies and everyday object use? Yes, they should have the same trouble visually, but as Hodges et al. point out, there is context to aid in constraining object use. And this brings us to:

Problem #2: They weren't actually asked to use the objects!

Despite what I said about visual recognition being a possible source of the deficit, I think the fact that patients were not actually asked to use the objects is the main problem with this study. Here is a description of the methods: "Subjects were given each object ... in isolation and asked to demonstrate its use." p. 1916 As there were no bottles to be opened, pencils to be sharpened, ingredients to whisk, potatoes to peel, etc., patients effectively had to quasi-pantomime the actions with object in hand. This differs from actually using the objects in a real context such as cooking, and differs from the investigators' "novel object test" where they had to actually use novel tools in the performance of a task (SD patients were not impaired on this task).

A much better design would have been to give subjects a task to actually perform on each trial (opening a wine bottle, whisking an egg) and giving them three objects to choose from just as in the novel object test. I bet performance would have been much better!

Tuesday, February 5, 2008

Semantics and Brain - Is semantic dementia an impairment to "conceptual knowledge"?

The claim is that semantic dementia, true to its name, is a selective deficit of semantic knowledge. The papers we read over last week constitute at least some of the evidence supporting this claim. So is it true? Well, it depends on what you mean by "semantic knowledge." As long as we restrict our definition to knowledge of relatively concrete concepts, then I think the evidence is decent (not rock solid, though).

So what is the evidence? Here's my outsider's assessment based on what we've read so far. I would, of course, welcome comment/correction from the experts!

1. Naming impairment is largely independent of input modality (picture, word, verbal description, environmental sound), and output modality (spoken, written response).

2. Relatedly, not only is naming affected, but so too is comprehension. Here there is a bit of a dissociation in that naming problems tend to be more severe than comprehension problems, but this is not surprising given that production in general seems to be more difficult than recognition. The paper we read by Matt Lambon Ralph et al. (2001, JoCN, 13:341-56) had a nice analysis of the relation between naming and comprehension in SD, particularly in relation to primarily left vs. right dominant atrophy.

3. Performance on "semantic judgment" tasks (such as the pyramid and palm trees test) is (sorta-kinda) modality independent as well. I say sorta-kinda because there are modality differences, but these, like the naming-comprehension asymmetry, are assumed to be easily explainable. For example, both Bozeat et al. (2000, Neuropsychologia, 38:1207-15) and Benedet et al. (2006, Neurocase, 12:15-26) report better performance on the picture than word version of the pyramid & palm tree/camel & cactus test. On the face of it, this is a bit puzzling because if the deficit involves central semantic representations and not the mechanisms that access them, then one should not expect any difference. This difference is explained away, however, by assuming that pictures have a more direct access route (a more systematic mapping) to the semantic system than do words (see Bozeat et al. p. 1213 for a paragraph on the topic). Kind of sounds like a mapping problem rather than a representation problem, doesn't it? But I suppose the idea is that a picture will produce a bigger jolt of activation than a word, thus making it more likely that the correct semantic representation in a degraded network is activated. Probably open to discussion, but let's grant it to them for now.

3. Breakdown of semantic abilities is hierarchical. SD patients tend to make superordinate errors (calling a FROG an animal) and tend to have more difficulty with subordinate features. These deficits transcend modality, affecting both input and output. I find myself having a hard time specifically stating how this observation argues for a semantic knowledge deficit above and beyond the modality effect, but it feels like it does. Maybe Warrington (1975; Quart. J. of Exp. Psy., 27:635-57) had the same sense when she wrote, without further argument, "The findings using probe recognition tasks [that assess judgments of super- vs. sub-ordinate semantic knowledge] suggest that the deficit is not merely in the retrieval of semantic information but that the storage systems are damaged." p.652. I guess the point is that since these patients can retrieve some semantic information successfully (i.e., the superordinate stuff), then retrieval per se cannot be affected. But why couldn't retrieval of details be differentially affected? Or maybe it's just the general sense that this pattern of deficit really feels like a degradation of semantically specific features, which in turn feels like a general knowledge problem (not exactly a crisp argument). If someone can clarify, please do!

Taken together, evidence of this sort feels like a pretty strong case for a general semantic deficit in the sense that it is clearly not just aphasia, or visual object agnosia.

Here's what I'm wondering though: is the semantic information that is lost, specific to the visual and auditory modalities? That is, how truly general is it?

The tests of modality generality of these deficits have involved predominantly, visual, auditory, and language functions. All of these abilities have been associated with temporal lobe function. Is it possible that the (no so focal) temporal lobe dysfunction in SD is causing disruptions to somewhat separable visual object systems, auditory object systems, and language systems? Or are these deficits a result of damage to a single semantic hub? I know that many SD researchers believe and argue for the later, but I'm not convinced yet that at least a portion of the deficit profile isn't due to modality specific dysfunction. Murray Grossman appears to have similar thoughts (based on looking ahead to future readings).

I'll elaborate on these thoughts in subsequent posts, in the context of summarizing some of the papers we read last week. For example, the paper by Hodges et al. (2000, Brain, 123:1913-25) showing that SD patients have deficits in object use (a less-visual/non-auditory/non-language ability that presumably involves parietal-frontal circuits) would seem to make a strong case for a more general deficit. But I think that study, while very interesting, is flawed. I'll explain in the next post.

Semantics and Brain course - reading set #5

This week's set of readings is aimed at more linguistic aspects of the semantic dementia pattern of sparing and loss. I will post some comments on last week's readings soon.

Saffran EM, Schwartz MF.
Impairment of sentence comprehension.
Philos Trans R Soc Lond B Biol Sci. 1994 Oct 29;346(1315):47-53. Review.

McCarthy RA, Warrington EK.
Repeating without semantics: surface dysphasia?
Neurocase. 2001;7(1):77-87.

Garrard P, Carroll E, Vinson D, Vigliocco G.
Dissociation of lexical syntax and semantics: evidence from focal cortical
degeneration.
Neurocase. 2004 Oct;10(5):353-62.

Grossman M, Moore P.
A longitudinal study of sentence comprehension difficulty in primary progressive
aphasia.
J Neurol Neurosurg Psychiatry. 2005 May;76(5):644-9.

Grossman M, Rhee J, Moore P.
Sentence processing in frontotemporal dementia.
Cortex. 2005 Dec;41(6):764-77.

Cappelletti M, Butterworth B, Kopelman M.
The understanding of quantifiers in semantic dementia: a single-case study.
Neurocase. 2006 Jun;12(3):136-45.

Yi HA, Moore P, Grossman M.
Reversal of the concreteness effect for verbs in patients with semantic dementia.
Neuropsychology. 2007 Jan;21(1):9-19.

Friday, February 1, 2008

What's with methods at the end of a journal article? New survey question

A number of journals are now putting methods sections at the end of the article. Is this a good practice? Nobody likes to slog through a tedious methods section, but shouldn't we have a look if we are going to properly evaluate a research paper? Or are these methodological details only relevant to the small fraction of folks who are actually directly involved in the area of research described? I have my opinions, but let's hear what you think first. Cast your vote in TB's latest survey...