Connectivity of Motor Cortex, Motor Thalamus, and Striatum

Abstract Projections from motor thalamus to frontal areas, especially the primary motor cortex (Brodmann area 4 in humans), play an important role in the planning, execution, and control of motor movements. While other cortical areas and subcortical targets contribute to processes such as conscious action selection, the motor thalamus and motor cortex are more centrally important for the initiation and production of motor commands during the movement itself. Thus, understanding how long-range connections of motor thalamus and cortex target specific cell types and brain regions can help clarify the circuits by which information comes in to initiate and plan movements, as well as identify the pathways by which it leaves to regulate movement. Recent technical advances have enabled the labeling, tracing, and manipulation of specific subtypes of excitatory and inhibitory cell types in these areas, with substantial similarities across several model systems including human, nonhuman primate, and rodent. Thus, a rough draft of inputs, local connections, and long-range outputs of motor thalamus and cortex can be drawn with cell type specificity.