By Kim Tong-hyung
Staff Reporter
Scientists have discovered new details about the complex mechanism involving human fear response, a discovery that they claim holds the promise of developing treatments for severe personality disorders.
The research team, led by Shin Hee-sup of Seoul's Korea Institute of Science and Technology (KIST), suggests that the medial pain system, the area of the brain that represents pain affection, has a key role in the social learning of fear by observation.
Also, the L-type calcium ion (Ca2+) channels, which are known to contribute to synaptic transmission and neural excitability in the anterior cingulated cortex (ACC) ― part of the medial pain system ― is also required in the learning process for fear, the scientists said.
Psychopaths, who suffer a severe mental illness that results in abnormally aggressive behavior, are often found to be impaired in recognizing the emotions and feelings of others.
By establishing a behavior model for social fear, Shin and his colleagues say they may have found a useful tool in developing measures to control such disorders, according to their study published by peer-review journal Nature Neurology.
"If the brain's medial pain system doesn't act normally, a person will not be able to properly recognize the pain and fear of others, and this could be related to a variety of conditions, such as psychopathic personality disorders," Shin said.
"By identifying the brain regions and mechanism related to fear learning and discovering the role of the L-type Ca2+ channels, we believe that we have made an important discovery in the efforts to develop treatments for mental illnesses related to fear learning by social observation."
The experiments on laboratory mice revealed that the animals developed freezing behavior and other responses after observing other mice receive repetitive electric shocks.
The observing mice had higher levels of fear when the mice receiving the shocks were socially related to them, such as siblings or mating partners.
The inactivation of the ACC and parafascicular or mediodorsal thalamic nuclei, which are the other parts of the medial pain system, substantially impaired this observational fear learning in the animals, the study said.
The deletion of the L-type Ca2+ channels in the ACC also impaired observational fear learning and reduced the behavioral pain responses.