Graduate Student Seminar Scheduled for April 27

The Spring 2011 Beckman Institute Graduate Student Seminar Series continues on Wednesday, April 27th. The seminar will feature three short talks from students Jihye Seong, Mallory Stites, and Woojae Han. The seminar will be held in Beckman Institute Room 1005 and a pizza lunch will be served to those attending the talks.

Detect FAK Activations at Membrane Microdomains by FRET
Jihye Seong
Bioimaging Science and Technology Department. Prof. Yingxiao Wang’s lab 

Fig. 1. (a) The design of membrane compartment-targeting FAK biosensors. (b) The ECFP/YPet ratio images of the Lyn-FAK (upper panels) and KRas-FAK biosensors (lower panels) upon 10 ng/ml of PDGF stimulation.  The color bar represents the ECPF/Ypet ratio values.
Proper subcellular localization of focal adhesion kinase (FAK) is crucial for many cellular processes such as cell adhesion, migration, and mechanotransduction. Since FAK associates with membrane signaling proteins, i.e. integrins and growth factor receptors, it is expected that FAK activation is regulated at plasma membrane, which contains different microdomains e.g. lipid rafts. It remains, however, unclear how FAK activity upon physiological stimulations is regulated at subcellular compartments. We have developed a fluorescence resonance energy transfer (FRET)-based FAK biosensor, and targeted it into or outside of lipid rafts at plasma membrane by lipid modifications. Upon cell adhesion on extracellular matrix proteins or stimulation by platelet-derived growth factor, the lipid rafts-targeting FAK biosensor showed a surprisingly stronger FRET response than that outside of lipid rafts, suggesting that the FAK activation can occur at lipid rafts regions. Further experiments revealed that the PDGF-induced FAK activation is mediated and maintained by the kinase activity of Src, whereas FAK activation by cell adhesion is independent of, and in fact essential for the Src activation. Thus, our results suggest that FAK is activated at lipid rafts with distinct activation mechanisms in response to different physiological stimuli. Therefore, by this distinct signaling hierarchy, cells may be able to tune the different mode of responses upon various physiological stimulations.

Get to/the Point: How Young and Older Adults Resolve Lexical Ambiguities in Online Reading 
Mallory Stites
Cognitive Division of the Psychology Department. Prof. Kara Federmeier.

Prior work using eye-tracking and behavioral measures has suggested that while both syntactic and semantic information can facilitate the disambiguation of noun/verb (NV) homographs (e.g., park), these sources are used differently, and neither can completely eliminate the ambiguity. In an event-related potential study, Lee and Federmeier (2009) found that, when only syntactic information was available, NV-homographs elicited a sustained frontal negativity relative to unambiguous words. The presence of coherent semantics eliminates this effect. Our previous eye-tracking work using the same sentences showed inflated first fixation durations to NV homographs in the syntax-only context. These parallel effects have been posited to reflect effortful meaning selection in the absence of coherent semantics. Older adults (60+) show markedly different patterns from the younger adults. They do not show the frontal negativity effect, suggesting they do not perform on-line meaning selection (Lee and Federmeier, in press). The current study shows that older adults do not exhibit the first fixation effect, but rather spend more time rereading the NV homographs in the syntax-only context. Findings suggest that older adults employ a different ambiguity resolution strategy, using later and more deliberate rereading tactics, likely to compensate for their inability to initially suppress the word’s context-inappropriate meaning.

The limitation of using average scores in speech perception studies
Woojae Han
Department of Speech and Hearing Science. Prof. Allen

Individuals with sensorineural hearing loss (SNHL) are prescribed hearing aids and/or a cochlear-implant, based on their pure-tone threshold and speech perception scores. Although this assistive listening device does help these individuals communicate in quiet surroundings, many still have difficulty in understanding speech in noisy environments. Especially, listeners with mild-to-moderate SNHL have complained that their hearing aids do not provide enough benefit to allow understanding of normal speech. Why is it that the modern hearing aid, even with a high level of technology, does not produce one-hundred percent efficiency? We shall show that the current clinical measurements, which interpret the result as a mean score, do not deliver sufficient detailed information about the characteristics of a SNHL listener's impairment when hearing speech and thus resulting in a poor fitting hearing aid.

UIUC Human Speech Recognition (HSR) group (Prof. Jont B. Allen) addresses three key questions, fundamental to clinical audiology and fundamental hearing science: (1) How well do the results of standard clinical tests predict the speech perception ability of SNHL patients? (2) Are the existing methods of hearing aid fitting (e.g., the half-gain rule, NAL-R, etc.) appropriate for modern hearing aid technology? (3) How useful are measured error patterns of speech perception in SNHL patients in addressing these perception errors?