Brodmann area 10

Brodmann area 10 (BA10, frontopolar prefrontal cortex, rostrolateral prefrontal cortex, or anterior prefrontal cortex) is the anterior-most portion of the prefrontal cortex in the human brain. BA10 was originally defined broadly in terms of its cytoarchitectonic traits as they were observed in the brains of cadavers, but because modern functional imaging cannot precisely identify these boundaries, the terms anterior prefrontal cortex, rostral prefrontal cortex and frontopolar prefrontal cortex are used to refer to the area in the most anterior part of the frontal cortex that approximately covers BA10—simply to emphasize the fact that BA10 does not include all parts of the prefrontal cortex.

BA10 is the largest cytoarchitectonic area in the human brain. It has been described as "one of the least well understood regions of the human brain". Present research suggests that it is involved in strategic processes in memory recall and various executive functions. During human evolution, the functions in this area resulted in its expansion relative to the rest of the brain.

The volume of the human BA10 is about 14 cm³ and constitutes roughly 1.2% of total brain volume. This is twice what would be expected in a hominoid with a human-sized brain. By comparison, the volume of BA10 in bonobos is about 2.8 cm³, and makes up only 0.74% of its brain volume. In each hemisphere, area 10 contains an estimated 250 million neurons.

BA10 is a subdivision of the cytoarchitecturally defined frontal region of cerebral cortex. It occupies the most rostral portions of the superior frontal gyrus and the middle frontal gyrus. In humans, on the medial aspect of the hemisphere it is bounded ventrally by the superior rostral sulcus. It does not extend as far as the cingulate sulcus. Cytoarchitecturally it is bounded dorsally by the granular frontal area 9, caudally by the middle frontal area 46, and ventrally by the orbital area 47 and by the rostral area 12 or, in an early version of Brodmann's cortical map (Brodmann-1909), the prefrontal Brodmann area 11-1909.

Area 10 lies underneath the air filled frontal sinus of the skull, which has limited electrophysiology research until 2009.

In humans the frontal pole area of the prefrontal cortex includes not only area 10 but part of BA 9. BA 10 also extends beyond the pole area into its ventromedial side. In Guenon monkeys, the pole area is filled by BA 12 (and its BA 10 is found in the orbital prefrontal region).

In humans the six cortical layers of area 10 have been described as having a "remarkably homogeneous appearance". All of them are readily identified. Relative to each other, layer I is thin to medium in width making up 11% of the depth of area 10. Layer II is thin and contains small granular and pyramidal medium to dark staining cells (in terms of Nissl staining) which colors RNA and DNA. The widest layer is III. Its pyramidal neurons are smaller nearer the above layer II than the below layer IV. Like layer II its cells are medium to dark. Layers II and III make up 43% of the cortex depth. Layer IV has clear borders with layers III above and V below and it is thin. Its cells are pale to medium in staining. Layer V is wide and contains two distinct sublayers, Va and Vb. The density of cells Va is greater than in Vb and have darker staining. Layers IV and V make up 40% of cortical thickness. Layer VI below layer V and above the white matter contains dark pyramidal and fusiform neurons. It contributes 6% of area 10 thickness.

Area 10 differs from the adjacent Brodmann 9 in that the latter has a more distinct layer Vb and more prominent layer II. Neighbouring Brodmann area 11 compared to area 10 has a thinner layer IV with more prominent layers Va, Vb and II.