Citation: Nitz (2014). The Posterior Parietal Cortex: Interface Between Maps of External Spaces and the Generation of Action Sequences. In Space, Time, and Memory in the Hippocampal Formation. Ch2 (pg. 27-54)
Part 1 of this book discusses the inputs to the hippocampus and their roles in spatial processing. It seems each chapter in this book is packed with a ton of data (making it a gold-mine for cool papers), yet the authors (at least Nitz) do a good job of making it highly readable. Rather than go deep into specifics, I’ll present overviews of what I’m taking away from each chapter.
This chapter focuses on the posterior parietal cortex, which, sandwiched between sensory and motor areas makes it an interesting candidate for translating sensation into cognition and cognition into action (PPC). This cortical subregion is a very high-level associational area that receives input from many secondary sensory cortices as well as the hippocampus. Through gain mechanisms, the PPC has the ability to represent multiple specific allocentric (world-centered, with reference to external environmental cues) and/or egocentric (self-centered, with reference to one’s own body) reference frames. For instance, PPC neurons may be significantly active whenever an organism is turning left, but may be most active when turning left at a particular location, and less active at others. This type of mechanism would be important, for example, for simultaneously determining your location within a building within a city (such as knowing how to leave your lab and get home (to a bar)).
Additionally, the PPC’s position adjacent to motor areas suggests its involvement in translating its cognition to action. PPC projects to premotor areas involved in planning and initiating movement.
Looking forward to the rest of the book, there are chapters on topics such as hippocampal modulation, time cells, remapping, splitter cells…I wish I read this a while ago.