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Advanced Neurology The anterior cingulate cortex in social empathy

recruited preferentially in the social transmission of fear 5. Neural circuits associated with the
that follows , suggesting that mirror neurons may be anterior cingulate cortex in empathy
[54]
directly involved in the presence of empathically activated
neural circuits. Both neural circuits from the ACC projecting to other
nuclei and from other nuclei projecting to the ACC underly
At the single-cell level, specific neuronal populations the neural mechanisms for social empathy. The neural
in the ACC have shown to create shared neural circuits from the ACC projecting to other nuclei include
representations between direct pain and pain empathy, ACC-nucleus accumbens (NAc), ACC-mediodorsal
and the shared neural representations depend on a thalamic nucleus (MDL), ACC-BLA, and local neural
mirror neuron system (MNS) located in A24b, which circuits in the ACC (Figure 2). ACC appears to have a
is activated both when an action is actively performed top-down regulation mechanism in the sensitization
and when it is observed [48,55] . Therefore, it has been of social pain, but the mechanism in which sensitivity
hypothesized that mirror neurons might be involved is regulated at the spinal cord level remains unclear.
in the encoding of painful emotional states transmitted According to research, when noradrenergic neurons in
during social interactions and might be the biological the locus coeruleus (LC) are activated, the concentration
bases for the shared neural mechanisms of direct pain of norepinephrine in the circulation increases, and
and pain empathy . However, it is still uncertain alpha-1 adrenergic receptor blockers can be used to
[56]
whether mirror neurons are capable of encoding the block mechanical pain hypersensitivity . The previous
[62]
emotional component of pain. Furthermore, although studies have shown a bidirectional synaptic connection
the neurons that are co-activated by empathy and pain between the LC and the ACC, and the excitability of its
have been identified in the ACC, the exact location of the neurons is regulated by the ACC [63,64] . Although it has
overlapping neurons and whether they are involved in been suggested that ACC-LC might mediate the top-
specific neural circuits remain unclear. down regulation of social pain, this hypothesis needs to
be further investigated with photogenetic technology. In
4.2. Somatostatin neurons in empathy
addition, a study has found that the inactivation of the
SST neurons release gamma-aminobutyric acid (GABA) lateral amygdala (LA) and the medial amygdala (MeA) can
ergic transmitters and affect the excitability of neighboring decrease emotional transmission and alternative learning
neurons to regulate the cortical state of certain regions . in rats . The LA-MeA circuit can connect social cues with
[57]
[12]
Studies have shown that SST neurons in the ACC are environmental cues and use these environmental cues to
associated with the discrimination of emotional states guide social behaviors in fear conditioning. The stronger
and the optogenetic inhibition of these neurons would the functional connection of the neural circuit, the more
eliminate social discrimination . Therefore, it has been the conditional freezing of social fear. According to Allsop
[58]
hypothesized that specific SST neurons in the ACC may be et al., the inner amygdala path between the LA and the
responsible for the emotional states of others in empathy MeA might be the basis for linking the emotional content
and that social cognitive function depends on an intact of social cues with other external prediction cues . Since
[45]
[59]
balance of cortical neuronal excitation and inhibition . previous studies have observed a dense projection between
Other experimental studies have shown that neurexin the ACC and the amygdala, it is speculated that the ACC-
(Nrxn)3-dependent SST interneurons in the ACC can MeA may be a potential neural mechanism for the ACC
control the degree of socially transmitted fear in mice. SST to adopt corresponding social behaviors after decision-
neurons contribute to the hyperactivity of ACC pyramidal making empathy. Furthermore, the MNS in the ACC may
neurons by decreasing inhibitory synaptic transmission, be the biological basis of the neural mechanism shared
thus driving enhanced alternative fear responses . by pain and pain empathy; this remains to be further
[46]
Therefore, the inhibition of ACC neurons through SST investigated.
neurons can be said to regulate empathy-related behaviors.
However, the molecular mechanisms underlying the 5.1. Anterior cingulate cortex-nucleus accumbens
mediation of SST neurons in the occurrence of fear pathway
empathy are unclear. Previous studies have shown that Recent studies have shown that the neural circuit from the
SST neurons with different molecules at different levels ACC to the nucleus accumbens (NAc) mediates the rapid
or in the same region may result in different function transfer of pain sensitivity and analgesia in bystanders,
and distribution [60,61] . Therefore, further investigations but not the expression of mechanical pain sensitivity .
[35]
are required to determine whether there are co-expressed In a study, pain empathy was not detected in unfamiliar
molecules that dictate the specific roles of SST neurons in mice, which suggested the importance of a familiar
empathy. social environment for pain empathy . In addition, the
[65]

Volume 2 Issue 1 (2023) 6 https://doi.org/10.36922/an.281