Premotor cortex

Premotor cortex
Name	Premotor cortex
Latin	Cortex praemotorius
Caption	Lateral view of human cerebral cortex
Location	Frontal lobe
Neighbors	Primary motor cortex; Supplementary motor area; Prefrontal cortex
Artery	Middle cerebral artery
Veins	Superficial cortical veins
Nerves	Corticospinal tract

Premotor cortex is a region of the human cerebral cortex located anterior to the primary motor cortex in the frontal lobe. It contributes to planning, selection, and coordination of voluntary movements and integrates multisensory information to guide action. Historically studied by neurosurgeons and neurophysiologists, the premotor cortex has been investigated in relation to behavior, disease, and rehabilitation by laboratories at institutions such as Harvard Medical School, Massachusetts Institute of Technology, University College London, Max Planck Society, and Johns Hopkins University.

Anatomy

The premotor cortex occupies the lateral and medial surfaces of the superior frontal gyrus and the precentral gyrus anterior to the central sulcus and adjacent to the hand knob region described at Harvard Medical School and in atlases from Brodmann and Brodmann areas. Gross anatomical borders are defined relative to the primary motor cortex, the inferior frontal gyrus near the region studied by Paul Broca, and the superior frontal sulcus noted in classic maps from Korbinian Brodmann. Vascular supply is primarily from branches of the middle cerebral artery with venous drainage to the superior sagittal and superficial cortical veins addressed in surgical texts from Mayo Clinic and Cleveland Clinic.

Subdivisions and Cytoarchitecture

Cytoarchitectonic studies by researchers associated with Korbinian Brodmann and groups at the Max Planck Institute for Human Cognitive and Brain Sciences subdivide the premotor cortex into dorsal and ventral regions (premotor dorsal, premotor ventral) and a medial supplementary motor area historically delineated in work at University College London. Brodmann area parcellations (including areas 6 and neighboring areas) and more recent probabilistic maps from consortia such as the Human Connectome Project and teams at Washington University in St. Louis reveal heterogeneity in layer thickness, pyramidal cell density, and modular organization. Histological staining methods developed at The Johns Hopkins Hospital and by laboratories at Columbia University highlight distinctions between granular and agranular cortical zones and the presence of specialized columns noted in classic primate studies from Yale University and Stanford University.

Connectivity

The premotor cortex is richly connected via corticocortical and corticospinal pathways. Major reciprocal connections include projections to and from the primary motor cortex characterized in tract-tracing studies at University of Oxford and long-range association fibers cataloged by the Human Connectome Project consortium. Subcortical connections include inputs from the thalamus and outputs to the spinal cord through the corticospinal tract studied by groups at Karolinska Institute and University of California, San Francisco. Basal ganglia loops involving the caudate and putamen, investigated at Massachusetts General Hospital and Mount Sinai Hospital, and cerebellar relays mapped by researchers at ETH Zurich and University of Geneva support sensorimotor integration. Functional connectivity studies using fMRI from teams at University of Michigan and Imperial College London demonstrate network coactivation with parietal regions, premotor homologues in nonhuman primates studied at Rikagaku Kenkyūjo (RIKEN), and homologous areas described in primate atlases from National Institutes of Health.

Function and Motor Control

Neurophysiological recordings from laboratories at California Institute of Technology and Princeton University show that premotor neurons encode movement intention, selection rules, and sensorimotor transformations, with task-dependent tuning reported in experiments from Cold Spring Harbor Laboratory. The ventral premotor area is implicated in grasping and object-directed actions, paralleling findings linked to mirror neuron research originating at Institute of Neuroscience, CNR and reported by teams at University of Parma and University of Milan. Dorsal premotor regions participate in movement sequencing and externally cued actions, as demonstrated in behavioral paradigms developed at University of Pennsylvania and Duke University. Clinical neurostimulation studies at Mount Sinai School of Medicine and Rush University show modulation of motor learning and recovery after stroke through targeted protocols.

Development and Plasticity

Developmental studies from cohorts at University of Cambridge and longitudinal neuroimaging initiatives such as the NIH MRI Study of Normal Brain Development reveal protracted maturation of premotor cortical circuits through adolescence, paralleling myelination patterns reported by research teams at University of California, Los Angeles and Brown University. Experience-dependent plasticity has been demonstrated in skill learning paradigms performed at Ecole Normale Supérieure and in constraint-induced movement therapy trials conducted at Sheba Medical Center and Walter Reed National Military Medical Center, showing structural and functional reorganization documented by diffusion MRI and transcranial magnetic stimulation work at University of Toronto.

Clinical Significance and Lesions

Lesions involving the premotor cortex, reported in case series from Mayo Clinic and epidemiological studies at Johns Hopkins Hospital, can produce deficits in motor planning (apraxia), impaired sensorimotor coordination, and focal dystonia described in clinical literature from National Institutes of Health and movement disorder centers such as Rush University Medical Center. Stroke, tumor resection, and degenerative disorders impacting premotor circuits manifest with impaired reaching, grasping, and speech-related motor planning as reported in rehabilitation trials at Massachusetts General Hospital and Guy's and St Thomas' NHS Foundation Trust. Therapeutic interventions including neurorehabilitation, invasive and noninvasive brain stimulation pioneered at University of California, Berkeley and University of Pennsylvania, and pharmacological strategies trialed at University of Toronto target premotor-driven networks to restore function.

Category:Cerebral cortex