Fig. 1: Identification of optimal target of stimulation.

a Schema of our hypothesis: motor thalamus stimulation potentiates motor output by increasing excitability of the motor cortex. The potentiation persists also after a lesion of the CST highlighted in red. b Top: High definition fiber tracking (HDFT) from VPL, VLL, and VAL nuclei (VPL: ventral posterolateral, VLL: ventral laterolateral, VAL: ventral anterolateral) of monkey motor thalamus to cortical regions (n = 3) (S1: primary somatosensory cortex, M1: primary motor cortex, PMd: dorsal pre-motor cortex, SMA: supplementary motor area). Bottom: Volume of thalamocortical projections (mean ± standard error (SE) over 3 animals) from each nucleus to each cortical region normalized by the total volume of fibers projecting from each nucleus. c Acute experimental setup. First, a cuff electrode was implanted around the motor branch of the radial nerve for stimulation. Animals were then implanted with a DBS electrode in the internal capsule (IC) and one in the VLL using the ROSA robot and intracortical arrays over S1 and M1. An intraspinal probe was implanted at the C6 spinal segment to record spinal local field potentials and EMG needle electrodes were inserted in arm, hand, finger and face muscles. A force transducer was placed in the animal’s hand to measure grip force. Finally, a camera recorded the kinematic of the arm and hand. d Left: Example of VLL electrode implant location localized from post-mortem MRI (Cd: Caudate Nucleus, IC: Internal Capsule, Pt: Putamen). Right: Normalized volume HDFT projections from the area of stimulation to cortical regions (mean ± SE over animals, n = 4). Source data for (b and d) are provided as a Source Data file. a, c Were designed by Isabella Bushko.