Figure 4.
Theoretical model summarizing structural and functional changes in axons within the developing prefrontal cortex. Electrophysiological analyses revealed a significant developmental increase in neurotransmission speed in axons projecting from the CCFM to Layer V in the Cg1 (speed is illustrated by the number and color of arrowheads). This increase in conduction velocity is accompanied by a developmental increase in the number of myelinated fibers and no change in axonal diameter, suggesting that myelination is a key factor driving faster neuronal processing. A positive relationship between conduction velocity and transmission distance in all animals suggests longer axonal projections may have a mechanism to ensure synchronized timing of incoming signals to Cg1 neurons. This phenomenon is observed even in the young age group, which has almost no myelin in these regions. Thus, other physical parameters such as axonal diameter, which varied widely among this axonal population, could serve to synchronize the timing of incoming information to postsynaptic cells residing in different locations in the Cg1. Illustrations were created by modifying images purchased in the PPT Drawing Toolkits-BIOLOGY Bundle from Motifolio, Inc.