The bilateral Right Cerebrum.Frontal Lobe.Postcentral Gyrus.Gray Matter.Brodmann area 4 corresponds to primary motor cortex localized in the precentral gyrus of the frontal lobe, though the Talairach label here appears to misattribute it to the postcentral gyrus. Brodmann area 4 is characterized by agranular cortex with a high density of large pyramidal neurons (Betz cells) in layer V, which give rise to the corticospinal and other descending motor pathways. This region is somatotopically organized into a motor homunculus, with distinct cortical territories controlling voluntary movement of different body parts via projections to spinal and brainstem motor nuclei. Functionally, it is critical for initiation and execution of fine, fractionated movements, especially of the distal limbs, and integrates input from premotor and supplementary motor areas as well as somatosensory cortex to modulate force, timing, and coordination of motor output. There is no direct Wikipedia article for this exact Talairach composite label; a closely related and encompassing structure is Primary motor cortex.
The bilateral Right Cerebrum.Frontal Lobe.Postcentral Gyrus.Gray Matter.Brodmann area 4 region—corresponding roughly to primary motor cortex in the Talairach 2 mm atlas—is implicated in multiple genetic and GWAS findings, although studies more often reference “precentral gyrus” or “primary motor cortex” rather than this exact composite label. Large neuroimaging GWAS (e.g., ENIGMA, UK Biobank) have identified variants in genes such as HMGA2, IGF1, microtubule and synaptic genes (e.g., MAPT region, BDNF-related pathways), and loci near METTL15, KIAA0586, and others associated with cortical thickness and surface area in motor and adjacent somatosensory regions, including BA4. Motor cortex structure and activation in this area have been genetically linked to general cognitive ability, reaction time, educational attainment, and physical activity traits, as well as to handedness through loci in genes like PCSK6 and MAP2 affecting hemispheric motor organization. Disorders with robust genetic components involving this region include amyotrophic lateral sclerosis (ALS) and hereditary spastic paraplegia, in which risk variants (e.g., C9orf72, SOD1, TARDBP, FUS, SPAST) are associated with degeneration or dysfunction of corticospinal neurons whose cell bodies lie within BA4; childhood-onset motor disorders (e.g., cerebral palsy susceptibility loci, DYT1/TOR1A dystonia) and Parkinson’s disease risk variants (e.g., SNCA, LRRK2, GBA) show altered motor cortical activation or structure in imaging-genetic studies. Additionally, polygenic risk for schizophrenia, bipolar disorder, ADHD, and autism has been associated with subtle structural and functional variation in motor and premotor regions including BA4, suggesting shared neurodevelopmental genetic influences on motor circuitry and broader cognitive–behavioral phenotypes.
Overview generated by GPT-4o (2026).
Region ID: 836
Hemisphere: bilateral
Atlas: Talairach labels 2mm
Full Quality Version: Download MP4
Full Quality Version: Download MP4
Wali Sidiqyar*, Gaurav Rudravaram*, Elyssa M. McMaster, Trent M. Schwartz, Adam M. Saunders, Kurt G. Schilling, Bennett A. Landman "Introducing SPINS: A Shared Public Visualization Library of Neuroanatomical Structures." Medical Imaging with Deep Learning- short paper
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