Visual working memory, the process involved in actively maintaining visual information over a short period of time, is essential for numerous everyday behaviors. A substantial amount of research has gone into characterizing the exact nature of one of the defining characteristics of visual working memory, its seemingly-counterintuitive limited capacity. Typically, these studies involve testing the memory for the value of a feature of some number of stimuli (e.g., the orientation of one of four oriented stimuli).
However, more recent studies have shown that visual working memory holds more than just a point estimate of a stimulus feature, implying that the previous methods investigating visual working memory limits are underestimating the capacity and flexibility of this process. In my dissertation, I use psychophysical, computational, and neuroimaging methods to investigate how people maintain and use two additional pieces of information: an item's uncertainty, or the knowledge of the noise associated with its memory, and its priority, or behavioral relevance.
In the first two chapters, I investigate how priority is maintained and used in working memory. In the first chapter, I investigate how we allocate our working memory resource across items with different priorities. I show that people allocate resources consistent with a loss-minimizing strategy. In the second chapter, I ask how priority is maintained in the brain during a delay. I find that, in visual areas, priority is maintained through the amount of delay-period activity of the same neural populations maintaining each item’s location.
In the third chapter, I investigate uncertainty in working memory, showing that people maintain an accurate representation of item-specific uncertainty over a delay and use it optimally when deciding if a stimulus has changed in orientation.
In the final chapter, I investigate both priority and uncertainty, replicating and extending findings from previous chapters. First, I show that people allocate resource in a way consistent with a loss-minimizing strategy, even when incentivized to use a different strategy. Second, I show that people maintain an item-specific representation of uncertainty, which isn’t affected by priority information. Finally, I show that people use item-specific uncertainty optimally when placing a wager about the accuracy of their memory.
Together, my studies demonstrate different ways in which working memory maintains and uses information that is helpful with interacting effectively with our environment.
|Advisor:||Ma, Wei Ji|
|Commitee:||Curtis, Clayton, Landy, Michael, Savin, Cristina, Wolpert, Daniel|
|School:||New York University|
|School Location:||United States -- New York|
|Source:||DAI-B 81/5(E), Dissertation Abstracts International|
|Subjects:||Experimental psychology, Psychology, Neurosciences|
|Keywords:||Bayesian, fMRI, Psychophysics, Visual working memory|
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