Description
The parietal lobe is the region of cerebral cortex between the frontal and occipital
lobes, underlying the parietal bone at the roof of the skull. This area is
roughly demarcated anteriorly by the central fissure, ventrally by the Sylvian
fissure, dorsally by the cingulate gyrus, and posteriorly by the parieto-occipital
sulcus . The principal regions of the parietal lobe include the
postcentral gyrus (Brodmann’s areas 1, 2, and 3), the superior parietal lobule
(areas 5 and 7), the parietal operculum (area 43), the supramarginal gyrus (area
40), and the angular gyrus (area 39) .
Together, the supramarginal gyrus and angular gyrus are often referred
to as the inferior parietal lobe. The parietal lobe can be divided
into two functional zones: an anterior zone including areas 1, 2, 3, and
43; and a posterior zone, which includes the remaining areas. The anterior
zone is the somatosensory cortex; the posterior zone is referred to as
the posterior parietal cortex.
The parietal lobes have undergone a major expansion in the course of
human evolution, largely in the inferior parietal region. This increase in
size has made comparisons of various areas in the human brain with those
in the monkey brain confusing, especially because Brodmann did not
identify areas 39 and 40 in the monkey. Whether monkeys actually have
regions homologous to areas 39 and 40 is debatable. One solution to this
problem is to consult another anatomist, Constantin von Economo.
On von Economo’s maps, in which parietal areas are called PA (parietal
area A), PB, and so forth, are three posterior parietal areas (PE, PF, PG) that
von Economo described in both humans and monkeys (Figure 14.1C). If we use
this system, area PF is equivalent to area 7b and PE to area 5 in Felleman and
van Essen’s flat map of cortical areas in the macaque (see Figure10.17).
Similarly, area PG in the monkey includes areas 7a, VIP, LIP, IPG, PP, MSTc,
and MSTp. These PG areas are primarily visual .