The efferent and afferent connections of the supplementary motor area

Abstract

The efferent and afferent connections of the supplementary motor area (SMA)ere studied in 6 squirrel monkeys using [ 3H]leucine and horseradish peroxidase, respectively. Efferent projections, common to all leucine-injected animals, were found to the cortical areas, 9, 8, 6, 44, 4, 2, 5, 7, 24 and 23. Subcortically, efferents were found to the putamen, caudate nucleus, claustrum, the thalamic nuclei reticularis, ventralis anterior, ventralis lateralis, medialis dorsalis, centralis lateralis, paracentralis, centrum medianum, parafascicularis, centralis superior lateralis, centralis inferior and lateralis posterior, the subthalamic nucleus, field H of Forel, nucl. ruber, reticular formation of midbrain, pons and medulla, the pontine gray and nucl. reticularis tegmenti pontis. Afferent connections exist with the cortical areas 9, 8, 6, 44, 4, 1, 2, 5, 7, 24 and 23, insula, fronto-parietal operculum and superior temporal sulcus. Subcortical afferent connections exist with the claustrum, nucleus of the diagonal band, nucl. basalis Meynert, basolateral amygdaloid nucleus, the thalamic nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, centralis lateralis, paracentralis, centrum medianum, centralis superior lateralis, centralis inferior, lateralis posterior and pulvinaris, the posterior hypothalamus, ventral tegmental area, nucl. ruber pars parvicellularis, reticular formation of midbrain and pons, locus coeruleus and nucl. centralis superior Bechterew. The projections are discussed with respect to the possible role SMA plays in the voluntary initiation of motor actions.