Disengagement of motor cortex from movement control during long-term learning.

Motor learning involves reorganization of the primary motor cortex (M1). However, it remains unclear how the involvement of M1 in movement control changes during long-term learning. To address this, we trained mice in a forelimb-based motor task over months and performed optogenetic inactivation and two-photon calcium imaging in M1 during the long-term training. We found that M1 inactivation impaired the forelimb movements in the early and middle stages, but not in the late stage, indicating that the movements that initially required M1 became independent of M1. As previously shown, M1 population activity became more consistent across trials from the early to middle stage while task performance rapidly improved. However, from the middle to late stage, M1 population activity became again variable despite consistent expert behaviors. This later decline in activity consistency suggests dissociation between M1 and movements. These findings suggest that long-term motor learning can disengage M1 from movement control

Visualization 2: Fast volumetric imaging with patterned illumination via digital micro-mirror device-based temporal focusing multiphoton microscopy

Video 2 Originally published in Biomedical Optics Express on 01 May 2016 (boe-7-5-1727

Visualization 1: Fast volumetric imaging with patterned illumination via digital micro-mirror device-based temporal focusing multiphoton microscopy

Video 1 Originally published in Biomedical Optics Express on 01 May 2016 (boe-7-5-1727

Media 1: Nonlinear structured-illumination enhanced temporal focusing multiphoton excitation microscopy with a digital micromirror device

Originally published in Biomedical Optics Express on 01 August 2014 (boe-5-8-2526

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