Graduate Student Seminar Scheduled for March 26

The Beckman Institute Spring 2008 Graduate Student Seminar Series  will feature the following presentations: "Decoding Natural Scene Categories From Distributed Patterns of fMRI Activity" by Eamon Caddigan; "A General Method for Discovering Inhibitors of Protein-DNA Interactions Using Photonic Crystal Biosensors" by Leo L. Chan; and "Aging in Different Cultural Environments: Visual Brain Activity and Eye-Movements" by Joshua Goh.

The Beckman Institute Graduate Student Seminar Series presents the work of outstanding graduate students working in Beckman research groups. The seminars begin at Noon in Beckman Institute Room 1005 and are open to the public. Lunch will be served.

Decoding Natural Scene Categories From Distributed Patterns of fMRI Activity
Eamon Caddigan

Human observers are able to quickly and efficiently extract information, such as the "gist," from images of natural scenes (Potter & Levy, 1969). Previous studies have identified brain regions that respond selectively to images of natural scenes, including the parahippocampal place area (PPA; Epstein & Kanwisher, 1998) and retrosplenial cortex (RSC; O'Craven & Kanwisher, 2000). However, it is not known to what extent these place-selective regions participate in the categorization of natural scenes. As a means of testing for the presence of scene-category information in these regions, we used fMRI and statistical pattern recognition algorithms (Cox & Savoy, 2003) to identify distributed patterns of activity associated with natural scene categories (beaches, mountains, forests, tall buildings, highways, and industrial scenes). In a leave-one-run-out (LORO) cross-validation procedure, we found that statistical pattern recognition algorithms were able to predict the categories of the scene viewed by the participants at rates significantly above chance using voxels in the PPA. In contrast to a recent report of decoding individual images from activity in area V1 (Kay et al. 2008), the regions we are interested in (PPA and RSC) are not retinotopically organized. Hence, classifier performance does not rely solely on differences in simple visual features of the stimuli, but on a more abstract representation of scene category.

A General Method for Discovering Inhibitors of Protein-DNA Interactions Using Photonic Crystal Biosensors
Leo L. Chan

Protein-DNA interactions are essential for fundamental cellular processes such as transcription, DNA damage repair, and apoptosis. As such, small molecule disruptors of these interactions could be powerful tools for investigation of these biological processes, and such compounds would have great potential as therapeutics. Unfortunately, there are few methods available for the rapid identification of compounds that disrupt protein-DNA interactions. Here we show that photonic crystal (PC) technology can be utilized to detect protein-DNA interactions, and can be used in a high-throughput screening mode to identify compounds that prevent protein-DNA binding. The PC technology is used to detect binding between protein-DNA interactions that are DNA sequence-dependent (the bacterial toxin-antitoxin system MazEF), and those that are DNA sequence-independent (the human Apoptosis Inducing Factor (AIF)). The PC technology was further utilized in a screen for inhibitors of the AIF-DNA interaction, and through this screen aurin tricarboxylic acid (ATA) was identified as the first in vitro inhibitor of AIF. The generality and simplicity of the photonic crystal method should enable this technology to find broad utility for identification of compounds that inhibit protein-DNA binding.

Aging in Different Cultural Environments: Visual Brain Activity and Eye-Movements
Joshua Goh

A number of studies show that East Asian culture emphasizes collectivistic and holistic processing, whereas Western culture is associated with individualistic and analytical approaches. These cultural biases have been related to more context-oriented visual processing in East Asians compared to more object-oriented processing in Westerners. With aging, more cultural experience is accumulated, which shapes our cognitive development over the lifespan in specific ways. In this talk, I will review these cultural differences in visual processing, and its effect on aging, as revealed by functional magnetic resonance imaging of the ventral visual brain areas and eye-tracking while young and older, East Asians and Westerners viewed complex pictures. The complex pictures consisted of selectively repeated objects or background scenes that differentially engage context and object visual processing, allowing us to probe the neural activity associated with these processes. Briefly, in the imaging data, we found significantly reduced engagement in object processing brain regions in older East Asians more so than young East Asians and Westerners, reflecting a greater bias for context-oriented processing. These findings suggest that external environmental experiences do impact aging brain functional development over and above typical biological changes associated with age.