Fiber system linking the mid-dorsolateral frontal cortex with the retrosplenial/presubicular region in the rhesus monkey.

The present study investigated the origin, course, and terminations of the association fiber system linking the frontal cortex with the hippocampal system by means of the cingulum bundle. Injections of tritiated amino acids were placed within individual cytoarchitectonic areas of the frontal cortex in the rhesus monkey. It was demonstrated that the mid-dorsolateral frontal cortex (areas 46, 9/46, and 9) and its medial extension (medial areas 9 and 9/32) is the origin of a specific fiber pathway, running posteriorly as part of the cingulum bundle, and terminating mainly in the retrosplenial area 30 and the posterior presubiculum. This fiber bundle therefore provides the anatomical substrate of a functional interaction between the mid-dorsolateral frontal cortex and the hippocampal memory system for the monitoring of information within working memory.