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Advanced Neurology The anterior cingulate cortex in social empathy

social transfer of pain was found to be more dependent that ACC-MDL can modulate alternative freezing
on olfactory perception , while visual and auditory behavior. Studies have also found that rats that
[36]
sensations contributed equally to the social onset of experienced foot stimulation were more likely to
pain . This is very different from the social transfer of induce alternative freezing behavior [22,75,76] . In addition,
[66]
[67]
fear, which relies on visual and auditory sensations . resting state-functional magnetic resonance imaging
Although the ACC encodes our own pain emotions (rs-fMRI) has revealed significantly enhanced regional
and the emotional states of others , further research connectivity of the ACC after electric shock, suggesting
[68]
in rodents is needed to determine whether social cues that the plasticity of ACC neurons may also be altered
transmitted through multiple sensory inputs can mediate in rodents with the same painful experience [77] ; similar
pain empathy. to the preferential recruitment of hippocampal neurons
in learning and memory with synchronous excitation
5.2. Anterior cingulate cortex-basolateral nucleus of in recall, there may also be a preferential recruitment
amygdala pathway of neurons activated by previous painful experiences
The ACC and the amygdala are associated with when reactivated by observational fear. Determining the
observational learning and social decision-making. subpopulation of ACC-MDL projection neurons is thus
Studies have shown that the pharmacological inhibition necessary to further explore the mechanisms of empathy
of both the ACC and the BLA significantly decreased at the neuronal level.
freezing behavior in observer mice [14,44,69] and there was Experiments in which rats were under observational
a synchronous increase in the theta rhythm between fear stimuli followed by conditioned fear experiments
the ACC and the BLA during the transmission of social have revealed enhanced conditioned fear, and the dynamic
fear in rodents [44,70] . In addition, ACC neurons have tracking of neurons activated by both types of fear has
been observed to rapidly alter basal firing rates during revealed that conditioned fear preferentially activated
social fear transmission [45,71] . Kim et al. have shown that neurons in the CA1 region of the dorsal hippocampus,
the optogenetic inhibition of ACC-BLA projections did which were also activated by observational fear, suggesting
not affect the freezing behavior of observational fear but that the overlapping activated neurons may have the ability
the inhibited fear memory in observational fear the next to integrate both types of fear learning . This may also
[78]
day . The above findings suggest that the neural circuit be the neuronal basis of the alternative freezing behavior
[72]
from the ACC to the BLA is involved in the transmission that is more likely to be evoked in foot-stimulated rats,
and encoding of social fear information (Table 1), where
ACC input dominates BLA encoding of social cues and suggesting that there may be a bidirectional positive
subsequent observational fear memory but does not feedback neural mechanism between observational and
conditioned fears. As mentioned in the previous section,
affect the re-expression of memory [14,45,71] . Post-long-term mirror neurons in the ACC have the dual property of
potentiation (LTP) activation depends on the de-silencing encoding signals for pain signals and observational fears .
[48]
of silent synapses in the ACC-BLA pathway that occurs
after observational fear . However, no experiments Mediodorsal (MD)-ACC projections, in turn, are involved
[73]
have been conducted to demonstrate the extent to which in the development of pain emotions and sensations as
[79-81]
this change in synaptic plasticity after observational fear well as in the enhancement of pathological states .
Although there is still no experimental confirmation of an
affects behavior. Instead, combining observational fear
experiment with inhibitory avoidance experiment (IA) overlapping relationship between activated ACC neurons
has revealed a rapid disappearance of LTP after the IA test, and mirror neurons in this circuit, the speculation that
along with observed rapid maturation of silent synapses the mechanism by which the formation of observational
and enhanced excitatory synaptic transmission, which fear shares a neural loop with affection pain awaits further
[74]
facilitated the ACC-BLA circuit . This is in contrast investigation.
to previous studies, which found that the maturation of Another interesting phenomenon is that the destruction
silent synapses is able to promote the expression of post- of ACC-MDL projecting neurons delays the onset of
LTP . alternative behavior but does not completely prevent it,
[73]
so there may be other neural loops mediating alternative
5.3. Anterior cingulate cortex-mediodorsal thalamic freezing behavior in rodents . Uncertainty surrounds the
[77]
nucleus pathway ability of ACC interneurons and ACC neurons projecting
Recent studies have found that the optogenetic to the MDL regulating alternative freezing behavior and
activation of ACC to lateral MDL circuit reduces the whether there is a more precise microcircuit mechanism
occurrence of freezing behavior (Table 1), suggesting between projecting neurons and interneurons.

Volume 2 Issue 1 (2023) 7 https://doi.org/10.36922/an.281