Auditory Stimuli Of Different Valences Affect The Cognitive Neural Mechanism Of Fear Extinction

Fear is one of the basic human emotions.Fear prompts us to avoid these unsafe stimuli,which contains the survival value.Some disorders（e.g.,post-traumatic stress disorder,PTSD）with excessive fear responses are often refractory to treatment and recurrence of symptoms after treatment.The fear extinction is the basis of exposure therapy.However,in recent years,more and more studies have found that the traditional extinction procedure does not "eliminate" the initial fear memory,but forms a kind of new memory.There is a kind of competition between the fear memory and new memory.When the fear memory is dominant,the recovery of fear symptoms occurs.Although some studies have gradually begun to try to pair positive valence stimuli with fear stimuli,and the positive valence stimuli are visual stimuli.However,we are exposed to a large number of sound stimuli in our daily life（eg,sweet music;the voice of a lover;bird calls in nature,streams,etc.）,and it is important to explore how these sound stimuli affect our fears.Therefore,on the basis of previous studies,the studies adopted electrodermal（skin conductance response,SCR）and functional near-infrared spectroscopy（f NIRS）to explore the cognitive neural mechanism of the effect of different valences of sound stimuli on fear extinction.Experiment I verifies whether neutral voice has a better fade-out effect than traditional fade-out.We used the classic big and small circle paradigm for fear acquisition on day one,fear extinction on day two,and fear recovery testing on day three.The extinction on the second day was divided into two groups,one was the traditional extinction group,and the other was a conditioned stimulus（CS）followed by a neutral sound stimulus.Behavioral results found no successful regression on the second day,but SCR results indicated successful regression in both groups at a later stage of regression.On the third day of the fear recovery test,there was no difference in behavioral outcomes between the two groups,but the SCR results found fear recovery in the traditional extinction group,but not in the neutral voice extinction.Experiment I found that compared with traditional extinction,neutral voices did have a better effect on retention after fear extinction.Experiment II further explored the effect of positive sound stimuli on fear extinction based on the findings of Experiment I.At the same time,we adopted the retrieval and withdrawal paradigm,which activates the memory by presenting a single fear stimulus first and then withdraws it.There are four conditions: the extraction-neutral sound;the no extraction-positive sound;the no extraction-neutral sound;the extraction-positive sound.The results showed that the dorsolateral prefrontal cortex（dlPFC）has different activation levels when distinguishing between safe and dangerous stimuli.When the memory was not activated,positive sounds had lower fear responses in the sensory cortex during fear extinction than neutral sounds.Neutral sound stimuli had better retention of fear recovery after memory retrieval.Taken together,this dissertation draws the following conclusions:1.Neutral voices and positive voices fade better than traditional fades.2.Neutral sounds require memory activation to have better extinction retention effect,and positive sound extinction can still have lower fear responses in the sensory cortex even without the memory activation.3.The dlPFC plays an important role in distinguishing between the threatening and safety stimuli.