Graduate Student Seminar Scheduled for March 18

The Spring 2009 Beckman Institute Graduate Student Seminar series continues on Wednesday, March 18. The seminar will feature three short talks from graduate students Ben Graf, Jihye Seong, and Ruchika Shaurya Prakash. The seminar will be held in Beckman Institute Room 1005 and a pizza lunch will be served.

Multi-modal microscopy for assessing cell structure, function and dynamics
Ben Graf

Multimodal Microscopy

One goal of imaging research is to use different modalities simultaneously in order to provide the structure or location of certain functional features of interest.  Integrated optical coherence (OCM) and multiphoton microscopy (MPM) is a technique that provides cellular level resolution of the structural and functional properties of biological tissue.  OCM allows depth resolved imaging based on scattered light while MPM is based on nonlinear fluorescence excitation.  OCM and MPM are capable of visualizing cells located in thick samples that cannot be imaged using standard microscopy.  Simultaneous use of these two imaging techniques presents technical challenges which require novel solutions.  A dual spectrum laser source designed to optimize both modalities is presented along with preliminary imaging results from cultured neurons and from in vivo skin.  OCM allows structural features of skin to be visualized while MPM identifies epidermal cells and the extracellular matrix based on fluorescence of endogenous proteins.  Integrated OCM-MPM will enable new investigations in tissue engineering and cell biology.

Visualization of Src activity at different compartments of the plasma membrane by FRET imaging
Jihye Seong

FRET Imaging

Membrane compartments function as segregated signaling platforms for different cellular functions. It is not clear how Src is regulated at different membrane compartments. To visualize local Src activity in live cells, a FRET-based Src biosensor was targeted in or outside of lipid rafts at the plasma membrane, via acylation or prenylation modifications on targeting tags either directly fused to the biosensor or coupled to the biosensor through an inducible heterodimerization system. In response to growth factors and pervanadate, the induction of Src activity in rafts was slower and weaker, dependent on actin and possibly its mediated transportation of Src from perinuclear regions to the plasma membrane. In contrast, the induction of Src activity in nonrafts was faster and stronger, dependent on microtubules. Hence, Src activity is differentially regulated via cytoskeleton at different membrane compartments.

Aerobic Fitness is associated with increased neural flexibility in older adults
Ruchika Shaurya Prakash

Increasing Fitness Levels

A growing body of literature provides evidence for the prophylactic influence of cardiorespiratory fitness against cognitive decline in older adults. This study examined the neural mechanisms associated with such fitness benefits. Specifically, employing a modified version of the Stroop task, we questioned whether higher levels of cardiorespiratory fitness were associated with an increase in cortical regions responsible for imposing attentional control along with a concomitant up-regulation of task-relevant representations. To isolate regions of the ventral visual cortex involved in processing task-relevant attributes and task-irrelevant attributes, we presented our participants with localizer scans to identify areas of the brain that were sensitive to color processing and word processing and subsequently studied modulation of these regions as a function of the Stroop task. We found that our older group of participants demonstrated the Stroop Interference effect, such that incongruent trials were associated with both slower response times and more errors relative to congruent and neutral trials. Higher fitness levels were associated with improved behavioral performance on the most demanding incongruent condition of the Stroop task. This was accompanied with an increase in the recruitment of prefrontal cortices in the most challenging condition for higher-fit individuals, thus providing evidence that cardiorespiratory fitness is inversely associated with age-related neural inflexibility demonstrated in previous studies. Our results thus provide insights for the differential mechanisms by which fitness has a favorable influence on cognitive control in older adults.