The bilateral GM Primary motor cortex BA4p R, as defined in the Juelich maxprob thr25 2mm Atlas, corresponds to the posterior subdivision of Brodmann area 4 within the precentral gyrus, forming part of the primary motor cortex and contributing critically to the execution of voluntary movements. This agranular cortical region is characterized by large pyramidal neurons (including Betz cells) in layer V, which give rise to corticospinal and corticobulbar projections essential for fine motor control, particularly of distal musculature. Functionally, BA4p is implicated in motor output rather than higher-order planning, integrating inputs from premotor and somatosensory cortices to generate precise motor commands. There is no direct Wikipedia article for “BA4p”; a closely related and encompassing structure is the Primary motor cortex.
The bilateral GM primary motor cortex BA4p (Juelich maxprob thr25 2mm) has been implicated indirectly in genetic studies of motor function, neurodevelopmental and movement disorders, and brain structure, though few GWAS explicitly target this cytoarchitectonic subfield. Variants in genes involved in motor system development and maintenance—such as those affecting corticospinal tract integrity, synaptic plasticity, and myelination (e.g., BDNF, CNTNAP2, FOXP2, and various ion-channel and axon-guidance genes)—have been associated with alterations in motor cortex structure or excitability in imaging–genetics and neurophysiological studies. Large-scale GWAS of cortical surface area and thickness (e.g., ENIGMA and UK Biobank–based studies) have linked common variants in loci related to neurodevelopmental pathways to structural variability in precentral gyrus regions encompassing BA4, while polygenic risk for disorders such as amyotrophic lateral sclerosis, multiple sclerosis, and schizophrenia has been associated with subtle volumetric or microstructural changes in primary motor areas. In addition, GWAS of motor-related traits (grip strength, reaction time, gait measures, and motor learning) and of neurodevelopmental conditions with motor components (ADHD, autism spectrum disorder) implicate distributed gene networks whose expression patterns include primary motor cortex, though associations are typically at the level of broader motor networks rather than BA4p specifically.
Overview generated by GPT-4o (2026).
Region ID: 50
Hemisphere: bilateral
Atlas: Juelich maxprob thr25 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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