Determining fundamental mechanisms of oculomotor working memory

Oculomotor working memory tasks are known to generate persistent activity in regions of the primate brain, including the lateral intraparietal area (LIP). This persistent activity is thought to reflect the active maintenance of behaviorally relevant information. The mechanisms that underlie this persistent activity have been the focus of a great deal of research, but several key principles remain untested due to practical difficulties recording from these circuits in the macaque. To address this issue, we implanted chronic high density electrode arrays in the common marmoset, an emerging model species amenable to large-scale recordings. However, while marmoset LIP has been firmly localized, few studies have functionally explored marmoset parietal cortex and their ability to perform oculomotor working memory tasks was unknown. In this thesis, I developed methods for training marmosets to perform memory-guided saccades and characterized the activity of LIP during this task. I found strong visual and saccadic activity, as well as evidence of persistent activity comparable to macaque LIP, establishing marmoset LIP during memory-guided saccades as a viable model for studying persistent activity. This project was greatly aided by the development of a novel “supersession” analysis method with Jens-Oliver Muthmann and others that allows units on chronic arrays to be easily tracked over weeks or months of behavioral sessions. In addition, I have helped adapt numerous techniques for use in the marmoset, including 2-photon calcium imaging and ultraflexible electrode arrays. Combined with the behavioral paradigms we developed, these approaches will allow persistent activity in primate cortex to be studied in ways that have previously been infeasible.Neuroscienc