Formerly known as the ascending frontal gyrus, the precentral gyrus is the home of the primary motor cortex, which works in association with other motor areas to plan and execute movement. The primary motor cortex contains a variety of pyramidal neurons whose axons extend down the spinal cord and synapse with motor neurons. Shown above are pericellular nests around pyramidal cell bodies (b,c,d) in the primary motor cortex, formed by the profusely branched axons of other neurons. Cajal noted the presence of pericellular nests in the cerebellum, hippocampus, and cortex and hypothesized that they amplify signals from the presynaptic cells to the enveloped cell body. We now know that pericellular nests allow tight control of the targeted cell, crowding out input from other, more distant axons. While the precise function of the pericellular nests above remains unknown, recent research in the hippocampus has shown that they can influence memory and reinforcement of learned behaviors.

3D print by Jeremy Swan based on an original illustration by Santiago Ramon y Cajal. Courtesy of the Cajal Institute, Spanish National Research Council or CSIC©