Wong & Lomber, 2019, Stable Delay Period Representations in the Posterior Parietal Cortex Facilitate Working-Memory-Guided Obstacle Negotiation, Curr Bio.
This group has previously implicated parietal area 5 of the cat in working memory (WM). While before they only showed this through behavioral deficits after inactivation of area 5, here they want to dig deeper into the specific contributions by investigating the dynamics of neural activity within area 5 during a WM task.
The findings are very interesting, but I really love the task from this study! It seems a very creative paradigm, especially due to the naturalistic behavior involved. They have a cat walk over a small wall (obstacle) to get to a food bowl. The obstacle is placed such that when they are eating, it lies directly between the forelegs and hindlegs (underneath the stomach). The great idea is that WM is required to maintain knowledge of the obstacle, which they will have to clear with their hindlegs after eating. So during the delay period the cat gets a snack. (Thus it becomes clear they are using cats because they are quadrupedal.)
They find that some neurons are stable throughout the delay, some neurons only fire in the early delay, and still others prefer the late delay. An interesting analysis is the behavioral correlate of step-height with neural firing. They find that early-delay neurons correlate with the foreleg step height (as in, they just stepped over the obstacle), and late-delay neurons correlate with hindleg step height (they are about to step over the obstacle, “executing” the WM). They bring it all together by suggesting that the neurons that show persistent delay-period activity might serve as a “bridge” to pass information from early-to-late delay neurons.