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Abstract

One recent study showed that the insular cortex of the macaque monkey can be divided into 15 architectonic areas and sub-areas with sharp borders (Evrard et al., 2014). This
new division contradicts older studies that proposed 3 vast sectors separated by vague borders (Mesulam & Mufson, 1982). A basic principle of cortical neuroanatomy is that distinct architectonic areas must have distinct connections and functions. To validate the new architectonic map of the insula, the tracing patterns and architectonic patterns in
the insular cortex of the macaque monkey will be compared. First, the anterograde and retrograde labeling of neurons in series of coronal sections through the insular cortex will
be charted and analyzed. The sections will be obtained from monkeys that have been injected with tracers (e.g. biotinylated dextran amine) in different sites of the brain
(orbital prefrontal cortex, thalamus, etc.). Second, the patterns of anterograde and retrograde labeling with the localization of the insular architectonic borders in adjacent Nissl or Gallyas stained sections will be compared. By examining whether architectonic areas and connectivity fields overlap in the insula, this study might help support and refine the new architectonic borders of the insula. Furthermore, this project, by already presenting specific connections, will help further studies about how individual insular areas connect to other parts of the brain. The examination of the connections of each individual area will be necessary to establish a new anatomofunctional model of the primate insula.