Corticostriatal Flow of Action Selection Bias

The posterior parietal cortex (PPC) performs many functions, including decision making and movement control. It remains unknown which input and output pathways of PPC support different functions. We addressed this issue in mice, focusing on PPC neurons projecting to the dorsal striatum (PPC-STR) and the posterior secondary motor cortex (PPC-pM2). Projection-specific, retrograde labeling showed that PPC-STR and PPC-pM2 represent largely distinct subpopulations, with PPC-STR receiving stronger inputs from association areas and PPC-pM2 receiving stronger sensorimotor inputs. Two-photon calcium imaging during decision making revealed that the PPC-STR population encodes history-dependent choice bias more strongly than PPC-pM2 or general PPC populations. Furthermore, optogenetic inactivation of PPC-STR neurons or their terminals in STR decreased history-dependent bias, while inactivation of PPC-pM2 neurons altered movement kinematics. Therefore, PPC biases action selection through its STR projection while controlling movements through PPC-pM2 neurons. PPC may support multiple functions through parallel subpopulations, each with distinct input-output connectivity. •PPC neurons projecting to STR (PPC-STR) and pM2 (PPC-pM2) form parallel subsystems•PPC-STR neurons represent action selection bias more strongly than PPC-pM2 neurons•PPC-STR neurons receive strong inputs from association areas and bias action selection•PPC-pM2 neurons receive strong inputs from sensorimotor areas and control movements The posterior parietal cortex (PPC) is important for both action selection and sensorimotor control. Using projection-specific anatomical tracing, activity recording, and perturbation, Hwang et al. identified two parallel subsystems in PPC, each involved in action selection and motor control, respectively.