Neuroscience of Human Ventral Lateral (VL) Thalamic Nucleus Related to Movement and Movement Disorders

The ventral lateral nucleus (VL) in the human ventral group exhibits activity associated with active and passive limb movements, as well as pathological movements found in patients with movement disorders. This group includes the anterior (VLa) and posterior (VLp) nuclei, which receive excitatory inputs from the deep cerebellar nuclei and inhibitory inputs from the internal segment of the globus pallidus (GPi). These nuclei primarily project to the primary and supplementary motor cortices. Despite differences in input sources, neurons in VLa and VLp often show similar activity patterns during active movements. In contrast, neurons in the cerebellar receiving nucleus respond more frequently during active movements, and microstimulation of these regions induces peripheral movements in monkeys, presumably due to their connections with the motor cortices. Neuronal activity in patients with movement disorders often mirrors the frequency of EMG activity during disordered movements, with a cross-correlation observed between neuronal firing and EMG signals. A long history of research demonstrates that stereotactic ablation of the VL nucleus can lead to sustained improvements in some movement disorders, similar to the effects achieved through high-frequency stimulation of the VL nucleus through implanted deep brain stimulation (DBS) devices.