Wednesday, September 26, 2007

Post Doc opening at Talking Brains West!

Department of Cognitive Sciences
Center for Cognitive Neuroscience
Position: Postdoctoral Scholar

The Department of Cognitive Sciences and the Center for Cognitive Neuroscience announce a Postdoctoral Scholar position in the Laboratory for Cognitive Brain Research.

A postdoctoral position is available in the laboratory of Dr. Greg Hickok at the University California, Irvine. The postdoctoral fellow will collaborate in NIH-funded research investigating the functional anatomy of language and complementary pursuits. Ongoing research projects in the lab employ a variety of methods, including traditional behavioral and neuropsychological studies, as well as techniques such as fMRI, EEG/MEG, and TMS. Opportunities also exist for collaboration with other cognitive science faculty and with faculty in the Center for Cognitive Neuroscience.

Candidates should have a Ph.D. in a relevant discipline and experience with functional MRI, preferably in the area of speech and language. Familiarity with computational and statistical methods for neuroimaging (e.g. MatLab, SPM, AFNI) is advantageous.

Candidates should send a CV, a letter of interest (including research skills), and a list of 3 references to the address below. The position start date is flexible, available beginning Fall 2007 for a period of 3 years.

Salary will be commensurate with experience, minimum annual stipend: $36,012.

Contact information:
Lisette Isenberg
Department of Cognitive Sciences and Center for Cognitive Neuroscience
3151 Social Science Plaza
University of California, Irvine
Irvine, CA 92697-5100

The University of California, Irvine is an equal opportunity employer committed to excellence through diversity.

Sunday, September 23, 2007

Meta-ling tasks - Lt. Columbo Finale II ("Just one more thing ...")

As Greg showed very clearly in the last few posts -- and as we have argued in our papers, as well -- one has to be very *very* careful to interpret the task-related cognitive neuroscience data, because the execution of the speech tasks can mask, disguise, or distort the findings vis-a-vis speech processing in its ecologically natural form.

[Greg: nice job with the historical argumentation :-) I like how you nail Lichtheim and show how his approach led to a modification of the Wernicke model for all the wrong reasons.]

I wanted to add one more small point, as we leave this issue (just like Peter Falk as Columbo). Even 'early' cortical responses are changed dramatically during the execution of experimental task demands, a phenomenon exploited extensively in the attention literature. One example comes from work we did 10+ years ago at UCSF, using MEG to characterize the neuromagnetic responses evoked by CV syllables. In a within-subjects design, we recorded neuronal activity while participants listened to CV syllables passively (no explicit task required) and when they listened to the very same material when making a phonological judgment. When we examined the N100m (M100) response, the pattern of data showed that executing the task differentially modulated the N100m amplitude and lateralization. The critical finding in the context of speech perception research was that -- compared to the baseline (same stimuli but no meta-linguistic task -- lateralization was induced by the task when in the passive case there was none! ** This illustrates that even temporally early cortical responses are affected by tasks in a way that complicate the interpretation of how speech perception is implemented in the brain.

**Poeppel, D., Yellin, E., Phillips, C., Roberts, T.P.L., Rowley, H., Wexler, K., Marantz, A. (1996). Task-induced asymmetry of the auditory evoked M100 neuromagnetic field elicited by speech sounds. Cognitive Brain Research 4: 231-242.

Thursday, September 20, 2007

Meta-ling tasks -- Finale: How Lichtheim's meta-ling task helped bring down Wernicke's Model

Hopefully, the first three parts of this thread on metalinguistic tasks has shown that reliance on data from such tasks can lead one astray from an accurate understanding of speech processing in the context of more ecologically valid situations. There seems to be a prominent historical precedent for language research being misled by metalinguistic tasks. In particular, it seems to be Lichtheim's use of such a task that contributed to the downfall of the classical model of aphasia...

In Wernicke’s original model, volitional speech production consisted of two parallel pathways. A direct pathway from conceptual representations to motor word memories, and an indirect pathway from conceptual representations to auditory word memories to motor word memories. The indirect pathway, was thought to exert a “corrective” influence on the selection of motor word memories. As such this pathway explained the occurrence of selection errors (paraphasias) in the speech production of sensory (Wernicke’s) and conduction aphasics.

Lichtheim, in his 1885 development of Wernicke's model, concurred with his predecessor that auditory word representations were indeed activated during speech production, and that this activation helped constrain motor word selection. He even devised a (metalinguistic) task to assess the ability to activate these auditory representations in patients who could not speak.

"…this is the method I use: I ask the patient to press my hand as often as there are syllables in the word to which an object corresponds. Those who have not lost the auditory representations can do this, even if their intelligence be limited, as I have been able to satisfy myself even under the least favourable circumstances. For instance, a patient who, besides a focal lesion of the right hemisphere, had had a haemorrhage in the left half of the pons, and suffered, among other pseudo-bulbar symptoms, from complete speechlessness, preserved the faculty of fulfilling the test to the very last." p. 441.

He applied this test to Broca’s aphasics (although he admits they were not pure forms), and found that they could not perform the task. From this he concluded that these patients “lost the innervation of the auditory word-representations” (p. 441), and therefore that in Broca’s aphasia “the path from concept- to sound-centre must be interrupted” (p. 441). This conclusion forced Lichtheim to reject Wernicke’s position that conceptual representations can directly activate auditory word representations. Instead, Lichtheim proposed that the auditory activation in volitional speech production must pass through Broca’s region; i.e., concept → motor → auditory. An alternative interpretation, which Lichtheim did not consider, is that it is Broca's region that somehow supports the ability to perform his syllables task. On this interpretation, he would not have had to reject Wernicke's original position that conceptual systems can activate both motor and sensory representations of speech directly, and in parallel.

Lichtheim's conclusions from his metalinguistic task led him to several awkward claims and logical contradictions, for example, how to explain paraphasias in transcortical sensory aphasia. These problems were targeted by subsequent authors (e.g., Freud) as serious problems for the general connectionist (i.e., classical) approach. If Lichtheim had stuck with Wernicke’s original claim, these problems would not have arisen, and perhaps the classical models would not have fallen out of favor.

Monday, September 17, 2007

Georgetown Tenure Track Job Opening

Georgetown University Tenure Track Position in Cognitive Neuroscience: The Department of Psychology at Georgetown University anticipates a tenure-track assistant professor position, effective August 1, 2008.

Applications in any area of cognitive neuroscience are welcome, but we are especially interested in candidates specializing in the neural bases of language or in social/affective neuroscience, with a focus on any area of lifespan development. Successful applicants should bring an active research program with potential for external funding. They should also be prepared to teach courses in cognitive neuroscience and other areas related to their specialty, as well as general psychology, our introductory course. Excellent teaching skills, a strong publication record, and previous demonstration of funding will be advantageous.Georgetown University has a state-of-the-art brain imaging facility with a research-dedicated 3T magnet and technical support for fMRI, DTI, and MRS. The Psychology Department offers an undergraduate major in psychology, an honors program, and a doctoral degree with concentrations in Lifespan Cognitive Neuroscience and in Human Development and Public Policy. In addition, Psychology faculty may mentor Ph.D. students in other programs such as the Interdisciplinary Program in Neuroscience based in the adjacent Georgetown University Medical Center. For more information about our department, visit our website at **.

Please send a letter of interest, a curriculum vita, teaching statement, and three letters of reference to: Chandan Vaidya, Chair, Cognitive Neuroscience Search Committee, Department of Psychology, 306 White Gravenor Hall, Georgetown University, 37^th & O Streets, NW, Washington, D.C. 20057. For administrative questions, contact Amber Matzke at .Applications will be accepted until the position is filled, but we aim to complete the search as early as possible. Georgetown University, the oldest Catholic University in the United States, is an Affirmative Action/Equal Opportunity employer.

Friday, September 7, 2007

UMass Amherst Open Rank Job

invites applications for an open-rank, tenure track position in COGNITIVE PSYCHOLOGY beginning Fall 2008. Candidates in any area of Cognitive are encouraged to apply, but we have special interests in human memory, categorization, judgment and decision making, and language processing. Use of computational modeling techniques is particularly desirable. Candidates applying at the junior level must have a strong record of research, clear potential to obtain support for and maintain an active research program, and strong teaching skills. Senior
candidates must additionally have a record of extramural support. Candidates will be expected to collaborate with other faculty members with similar interests across campus. Rank and salary are dependent on experience and qualifications. Applicants should send a vita, a statement of research and teaching interests, reprints of recent publications, and at least three letters of recommendation to: Cognitive Search Committee, Department of Psychology, University of Massachusetts, Amherst, MA 01003-7710. Applications are due on November 1, 2007. The search committee will begin reviewing applications on that date, and will continue until the position is filled. Hiring is contingent upon the availability of funds. The University of Massachusetts is an Affirmative Action/Equal Opportunity Employer. Women and members of
minority groups are strongly encouraged to apply.

Tuesday, September 4, 2007

Metalinguistic Tasks -- Part 4

It is clear that speech sound processing as measured by metalinguistic speech perception tasks such as syllable discrimination and identification can double dissociate from speech sound processing as measured by auditory comprehension tasks. This means that at some stage of processing, these two abilities rely on different neural systems. Does this mean that the two tasks rely on entirely segregated neural systems? Of course not! It is a good bet, for example that the two classes of tasks do not differentially engage the cochlea. But at what level in the nervous system do they diverge? We don't know.

We have suggested that the divergence occurs at fairly advanced stages of auditory processing, in non-primary cortical auditory regions. The speculation is that whatever basic auditory and phonetic/phonological processing goes on in auditory cortex -- as opposed to meta-phonological processes supported by say frontal systems, such as phonological working memory or attentional processing -- is common to the two tasks. This predicts that damage to auditory regions that disrupts these superior temporal lobe auditory/speech sound processing networks should lead to some degree of correlation between deficits on the two types of tasks. I believe there is some support for this speculation from studies of word deafness, where speech comprehension deficits have been linked to relatively low level speech sound processing.