During my talk I will present my postdoctoral research on rat Parametric Working Memory (PWM), and show formal algorithmic behavioral analysis, optogenetic inactivations, and electrophysiological recordings to suggest Posterior Parietal Cortex (PPC) as a central node in the representation and use of prior sensory experience in PWM. If time permits, I will bridge these findings to the research work we are building in my new lab at SWC.

Earlier proposals that PPC supports working memory predict that optogenetic silencing of the PPC would lead to a behavioral impairment in our working memory task. Contrary to this prediction, silencing PPC produced a significant performance improvement. Quantitative analyses of behavior revealed that this improvement was due to the selective reduction of the effects of prior sensory stimuli. Electrophysiological recordings showed that PPC neurons carried far more information about sensory stimuli of previous trials than about stimuli of the current trial. Furthermore, an increase in the amount of this information was associated with greater behavioral effects of sensory history, suggesting a tight link between behavior and PPC representations of stimulus history. Lastly, encoding of the sensory history in PPC was contrasted with striatum and frontal pre-motor areas in a series of decision making tasks. Together, the data reveal the PPC as a causally necessary and important node in the representation and use of prior sensory stimulus information.