Churchland lab

This week, my lab members and I attended a mini symposium at our own Cold Spring Harbor Lab. Organized by colleagues Tony Zador and Adam Kepecs, the focus of the day was understanding how the cortex and striatum interact to guide behavior. The speakers were Rui Costa, Linda Wilbrecht, Bernardo Sabatini, Anatol Kreitzer, and Tony Zador.

Linda Wilbrecht presented data aiming to understand the “currency” that the brain uses to make decisions. The talk included data from her recent Nature Neuroscience paper about behavioral effects of stimulating each of two classes of striatal dopamine neurons (D1-expressing and D2-expressing neurons). The first finding is that the two classes exerted opposite effects: stimulating D1 neurons caused more choices in one direction, while stimulating D2 neurons caused more choices in the opposite direction. The really interesting part, though, is that she found the effect of stimulation interacted with the animals’ reward history: for example, when stimulating neurons that caused more leftwards choices, she found the effect was enhanced if the animals had just experienced a few failed trials on the left side. WIthout stimulation, they would rarely go left after so many failures. But with the stimulation, they overcame this reluctance, and went left anyway. Understanding how recent reward history and current sensory information interact might one day give us insight into why the cycle of addiction is so hard to break.

Bernardo Sabatini described his experiments that aim to understand role of the direct versus indirect pathways. He stimulates each pathway optogenetically and looks at the effects on both behavior and firing rates of neurons in the motor cortex. He finds that the two pathways are not equal in the degree to which they affect firing rates and behavior. To visualize firing rates of motor cortex neurons, which are notoriously dynamic and complex, he reduced the dimensionality of the data using PCA. This analysis makes it possible to tell whether stimulation simply modifies an ongoing trajectory in high-dimensional space, or whether the stimulation drives the network to a novel state. The ability to perturb motor cortex and watch the resulting neural activity affords insight not just into striatal projections, but into developing motor commands as well.