284 Neuroanatomy: Draw It to Know It
Brodmann Areas
Here, we will draw select, fundamental Brodmann areas.
First, draw lateral and medial surfaces of the cerebrum.
Next, include certain key sulci. On the lateral hemi-
spheric face, include the precentral, central, and postcen-
tral sulci, and then the Sylvian fi ssure with its anterior
horizontal and anterior ascending rami, and also include
the lateral parietotemporal line. On the medial face,
include the corpus callosum, cingulate sulcus, and pars
marginalis, and then the paracentral, central, parieto-
occipital, and calcarine sulci.
Now, within the postcentral and posterior paracen-
tral g yri, from anterior to posterior, label Brodmann
areas 3, 1, 2; they constitute the primary sensory area.
Th en, within the precentral and anterior paracentral
g yri, label area 4, which is the primary motor area.
Within the primary motor and sensory areas, cortical
representation of the face and body is somatotopically
arranged in what is referred to as the homunculus (see
Drawing 19-4).
Now, in front of area 4, label area 6. On the lateral
hemisphere, area 6 is called the premotor area, and it lies
in the anterior precentral g yrus and posterior superior
and middle frontal g yri. On the medial hemisphere, area
6 is called the supplementary motor area, and it lies in
the medial aspect of the superior frontal g yrus. Th e pre-
motor and supplementary motor areas help assemble
complex motor programs.^19
Next, in front of area 6, label area 8. Th e most notable
feature of area 8 is that on its lateral surface it contains
the human homologue to the rhesus monkey frontal eye
fi elds — the animal model for human eye movements. In
humans, however, volitional control of eye movements is
derived from the anterior wall of the precentral sulcus
and portions of many additional disparate Brodmann
areas, including areas 4, 6, 8, and 9.^14 , 20 , 21
Now, label area 44 in the pars opercularis and area 45
in the pars triangularis of the inferior frontal g yrus. Areas
44 and 45 make up Broca’s area — the speech output area.
Next, peel back the superior temporal g yrus and label
areas 41 and 42 in the transverse temporal g yri (Heschl’s
g yri); these g yri form the primary auditory cortex. Th en,
label the superior temporal g yrus as area 22. Wernicke’s
area, the language reception area, lies in the posterior
portion of area 22 (and it also extends into the angular
g yrus, Brodmann area 39 [not drawn]).^22
Next, antero-inferior to area 8, along the surface of
the lateral and medial faces of the cerebrum, from supe-
rior to inferior, label areas 9, 10, and 11; then, in between
area 45 and area 10, label area 46; then, beneath area 46,
label area 47; and fi nally, in the anterior cingulate
g yrus, label area 24. Th ese areas form the prefrontal
cortex, which is subdivided into dorsolateral prefrontal,
orbitofrontal, and anterior cingulate (medial frontal)
cortices; each subdivision governs a discrete cognitive
domain. Although the exact anatomy of these divisions
is inconsistently defi ned, there is consensus regarding
their functions. Indicate that, generally, the dorsolateral
prefrontal cortex encompasses areas 9, 46, and a portion
of area 10; the orbitofrontal cortex comprises areas 11,
47, and a portion of area 10; and the anterior cingulate
cortex comprises area 24. Indicate that dorsolateral pre-
frontal cortex mediates executive function and task
sequencing — injury here results in organizational defi -
cits; that orbitofrontal cortex governs social behavior —
damage here results in impulsivity; and that anterior
cingulate (medial frontal) cortex mediates motivation —
injury here results in a lack of motivation (abulia).^23 , 24
Finally, within the occipital lobe, label the visual
cortex. On the medial surface, indicate that area 17, the
primary visual cortex, lies on the banks of the calcarine
sulcus; and then show that area 18, the secondary visual
cortex, lies above and below area 17; and then that area
19, the tertiary visual cortex, lies above and below area- On the lateral surface, show that area 17 lies at the
occipital pole, that area 18 lies anterior to area 17, and
that area 19 lies anterior to area 18.^25 , 26