This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Working memory (WM) refers to a neural system that holds and manipulates a relatively small amount of information for pending action and is crucial for resourceful cognitive processing. Clearly, selective attention mechanisms interact with WM from encoding relevant stimuli from all modalities to orchestrating retention of information resulting in goal-oriented behavior. A large body of previous research has focused on the limited capacity of WM and intriguing insights about the nature of WM come from studies investigating inter-individual differences and attention-related capacity deficits in clinical populations like patients suffering from schizophrenia. The classic procedure to probe visual WM is straightforward and elegant: A bilateral array of varying complexity is presented twice separated by a brief interval. The participants'task is to indicate whether both presentations are identical or different with respect to a particular feature. This task is easy with few stimuli but becomes more difficult as the number of elements in the array is increased. The capacity of WM has typically been estimated using behavioral tasks. Recently, however, Vogel and Machizawa (2004) reported an electrophysiological measure that is highly correlated with the amount of information being held in WM during a visual discrimination task. These authors used bilateral visual arrays with various numbers of bars in a cued attention paradigm and their participants had to look for a change in color of one of the squares on the attended side. I plan to investigate the generality of their original findings using behavioral data and high-density 168-channel EEG/ERP recordings by varying the number of spatial locations instead of changes in color. Encouraged by preliminary behavioral data that revealed striking similarities between auditory and visual WM capacity as a function of stimulus complexity, I will use also auditory, visual, and audio-visual stimuli to investigate the capacity limits of auditory and visual WM. These results will help to clarify a long-standing controversy as to whether the contents of WM are modality-specific or not. Dr. Ed Vogel served as Dr. Teder-Salejarvi's Individual Project Mentor.
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