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Advanced Neurology The anterior cingulate cortex in social empathy

5.4. Local neural circuits in the anterior cingulate a decrease in the E/I ratio . Therefore, the modulation
[93]
cortex of social cognition in rodents by ACC relies heavily on
In the cerebral cortex, information processing relies on the modulation of these interneurons, that is, receiving
a highly interconnected microcircuit that is composed remote projections from cortical or subcortical areas or
of excitatory glutamatergic pyramidal neurons and receiving local neurotransmitter modulation to achieve
[82]
GABAergic inhibitory neurons . The ACC is no a shift in excitatory or inhibitory effects on pyramidal
neurons following information integration. This ability
exception; as a center of social interaction and information to dynamically regulate interneurons is necessary for
integration, the activation and inhibition of its internal social interaction, and deficits or abnormal connections of
pyramidal neurons depend not only on the direct interneurons within the ACC can cause severe deficits in
projections of superior neurons, but also on the dynamic social functioning in animals, as shown in a study in which
modulation and filtering of information by intermediate participants with high autistic traits showed elevated
neurons . The interaction of different neurons allows the observational fear responses . In contrast, when PV+
[83]
[94]
ACC to process the input and output signals differently. neurons are absent, there is a deficit in information filtering
Inhibitory interneuron dysfunction is more likely to cause in the cortex that leads to autism [83,95] . This is consistent
dysregulation of neural homeostasis, thus resulting in with the neuroanatomical findings of autistic individuals
psychiatric symptoms . This includes both parvalbumin or model rats exhibiting PV+ neuron deficits [96,97] . Past
[84]
(PV)+ and SST+ neurons . Results of a viral bundle experiments have revealed a unique role for specific SST+
[85]
pathway tracing have shown that both PV+ and SST+ neurons in the ACC in the social transfer of fear in rodents,
neurons receive monosynaptic excitatory inputs from but the inhibition of PV+ neurons did not alter the level
the BLA and midline and intralaminar thalamic nuclei of alternative freezing in experimental animals . The
[46]
(MITN) [16,86] . Fast-spiking PV+ neurons in the ACC possible reason for this is that PV+ neurons in the ACC
mainly receive information filtered by the thalamus [83,87] have a weaker direct modulation of pyramidal neurons
and mediates feed forward inhibition around L2/3 and are more involved in the modulation of SST+ neurons.
pyramidal cells to control excitatory inputs to pyramidal However, it is undeniable that the microcircuits composed
neurons . SST+ interneurons, on the other hand, of PV+ neurons, SST+ neurons, and pyramidal neurons
[88]
target the distal dendrites of pyramidal cells and play a will be an important neurobiological basis for decoding
[89]
prominent role in regulating distal dendritic excitability . social cues in the ACC and the balance of microcircuits
SST+ interneurons also receive direct projections from L5 homeostasis within the ACC is crucial for decoding the
pyramidal neurons or the cortex. There is also a reciprocal behavior of social cues, such as empathy (Table 1).
inhibitory effect between these two interneurons [89,90] ; an
increase in PV neuron-mediated perisomatic feed forward There appears to be a top-down regulatory mechanism
inhibition of pyramidal neurons leads to a compensatory in the ACC for social pain sensitization. More and more
decrease in (SST+ neuron-mediated) dendritic neural circuits are likely to be identified in the involvement
inhibition [83,91] . The modulation of pyramidal neurons of empathy with the development of neural modulations.
by interneurons is seen to be a dynamic balance [83,92] .
However, less dendritic inhibition decreases the threshold 6. Clinical studies
at which pyramidal neurons are activated, lowering the Numerous clinical studies have confirmed that there
neurons’ capacity to filter information, and thus causing are variations in the empathic abilities of patients with
behavioral abnormalities. However, the effect of these two different neuropsychiatric disorders [98-100] . Patients with
modes of inhibition differs in that an increase in input Alzheimer’s disease (AD) and Parkinson’s disease (PD)
from PV+ neurons significantly decreases E/I, whereas have significantly lower social emotion recognition ability
the input from SST+ neurons to the distal dendrites of than their respective caregivers; meanwhile, changes in
pyramidal neurons significantly increases E/I. As a result, emotion perception and empathy in patients with AD and
the modulation of pyramidal neurons by interneurons is PD have an impact on the perceived burden and depression
more flexible and dynamic, thus facilitating the processing among caregivers. Therefore, an early identification of
of information from different brain regions. Recent the changes in empathic abilities in those patients may
studies have found that oxytocin can bind to postsynaptic be effective for interventions in both patients and their
oxytocin receptors on fast-spiking interneurons in the caregivers . As an other-oriented form of emotional
[98]
ACC and enhance inhibitory input to pyramidal neurons empathy, empathic concern was found to be higher in AD
by lowering the action potential (AP) threshold and patients than in controls. fMRI can be used to assist in
resting membrane potential of interneurons, and thus the assessment of functional changes in empathy-related
promoting depolarization of interneurons and inducing brain areas. A higher connectivity between the ACC

Volume 2 Issue 1 (2023) 8 https://doi.org/10.36922/an.281