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Advanced Neurology The anterior cingulate cortex in social empathy

paradigms: pain and fear empathy in rodents. The study and coordinated . Therefore, in the last decade or so,
[25]
of the neural mechanisms in the ACC during empathic some researchers have re-delineated the cingulate cortex
behavior is of great importance for the exploration of new of rodents by using a method that follows the distinction
therapeutic targets for patients with psychiatric disorders. between the cingulate cortex of other mammals (MCC
and ACC) to facilitate the study of brain function across
2. Anatomical division of the anterior species homologies. Rodent ACC ranges from A24a–b,
cingulate cortex A25, A32, and A33 (A33 is present in rats only), with A25

The human ACC is located in the anterior third of the corresponding to subgenual ACC and A32 and A24a and b
cingulate cortex, surrounding the cephalic end of the corpus roughly coinciding with pACC.
callosum (area [A]24a–c, A25, A32, and A33), while the Although the extent of the brain regions corresponding
midcingulate cortex (MCC) is located in the middle third to rodent ACC has been re-normalized, there is still no
of the cingulate cortex (A24a–c’, A32’, and A33’). The ACC way to clarify the boundary between the ACC and the
can be divided into posterior ACC (pACC) and subgenual PFC, especially the mPFC, because the prefrontal lobes
ACC (sACC) (Figure 1A). For rodents, there is a gradual of primates and rodents are fundamentally different in
shift in the nomenclature of the cingulate region. The development. In general, the lateral prefrontal lobes of
cingulate cortex was initially divided into cingulate area 1 rodents, that is, prefrontal lobes with the granular layer,
(Cg1) and Cg2, with Cg1 containing A24b and A24b’ and are underdeveloped , and researchers tend to use rodent
[26]
Cg2 containing A24a and A24a’. However, a problem exists, PFC to refer to primate mPFC. It has been found that the
in which the boundaries of the conventional cingulate ACC is homologous to the granule-free cellular structures
cortex partition in rodents are perpendicular to those in the mPFC, and therefore primate ACC is often treated
between ACC and MCC in primates , suggesting that Cg1 as a subregion of the medial prefrontal lobe . A large part
[23]
[27]
and Cg2 cover parts of what would be considered the ACC of the current data on rodent prefrontal lobe comes from
and MCC in other mammalians. It has been shown that studies of the prelimbic (PL), infralimbic (IL), and cingulate
there is a significant gap between rodent ACC and MCC regions . Therefore, the definitions of the cingulate
[28]
in terms of anatomical structure, cellular architecture, cortex, PFC, and mPFC remain ambiguous. As mentioned
connections to different brain regions, and the functions earlier, a nomenclature change has redefined these two
[24]
involved . However, to the extent of differentiation, regions and the anterior part of the cingulate cortex as
rodent ACC and MCC are functionally complementary the ACC, but because of the controversy, PL and IL are
A B

C

Figure 1. Anatomical division of the ACC. (A) The human ACC is located in the anterior third of the cingulate cortex, surrounding the cephalic end of
the corpus callosum (area [A] 24, A25, A32, and A33), while the midcingulate cortex (MCC) is located in the middle third of the cingulate cortex (A24’,
A32’, and A33’). The ACC can be divided into posterior ACC and subgenual ACC. (B and C) For rodents, the cingulate cortex was initially divided into
Cg1 and Cg2, with Cg1 containing A24b and A24b’ and Cg2 containing A24a and A24a’. Meanwhile, we define the ACC, IL, PL, and other areas of the
mPFC as the ACC.
ACC: Anterior cingulate cortex; Cg1: Cingulate area 1; Cg2: Cingulate area 2; IL: Infralimbic cortex; MCC: Midcingulate cortex; pACC: posterior ACC;
PL: Prelimibic cortex; sACC; subgenual ACC.

Volume 2 Issue 1 (2023) 3 https://doi.org/10.36922/an.281