Distinct population code for movement kinematics and changes of ongoing movements in human subthalamic nucleus

The subthalamic nucleus (STN) is theorized to globally suppress movement
through connections with downstream basal ganglia structures. Current
theories are supported by increased STN activity when subjects withhold an
uninitiated action plan, but a critical test of these theories requires
studying STN responses when an ongoing action is replaced with an
alternative. We perform this test in subjects with Parkinson’s disease
using an extended reaching task where the movement trajectory changes
mid-action. We show that STN activity decreases during action switches,
contrary to prevalent theories. Further, beta oscillations in the STN
local field potential, which are associated with movement inhibition, do
not show increased power or spiking entrainment during switches. We report
an inhomogeneous population neural code in STN, with one sub-population
encoding movement kinematics and direction and another encoding unexpected
action switches. We suggest an elaborate neural code in STN that
contributes to planning actions and changing the plans.