Neural Basis For The Initiation Of Emotions By Emotional Faces:Evidence From Patterns Of Evoked And Spontaneous Neural Activity In The Brain

Emotional faces carry complex emotional and social information and have received much attention and research.For example,emotional faces are often used to induce emotions in subjects in psychological studies,and people often use different emotional faces to signify the nature of some things in daily life.Previous studies on the processing mechanism of emotional faces have focused on the activated brain regions and the effects on some cognitive tasks.Despite the stability of emotions,how long do emotional stimuli(emotional faces)last? What is the pattern of neural activity in the brain in the resting state after the emotional stimulus disappears? Is it exactly the same as before the emotional stimulus? Previous studies have not yet explored these questions.In this study,pleasant,neutral and fearful face stimuli were used as emotional stimuli,and the experimental design was combined with functional magnetic resonance imaging(f MRI)technology,using the "resting state – task state-resting state" experimental model,and collected brain imaging data from the subjects in the baseline resting state,the task state when viewing the emotional faces,and the resting state after the emotional faces disappeared,in order to explore the effects of external emotional face stimuli on the internal brain activity from both the task state and the resting state.The first research objective in this study was to investigate the activation of brain regions under fearful,happy,and neutral faces in order to investigate the neural mechanisms in the brain during emotional face processing.The researchers collected f MRI data from 21 subjects during the viewing of different emotional faces,and the activation analysis revealed that the classical face processing brain regions such as the fusiform area,occipital cortex,and temporal cortex were activated accordingly,while the precentral gyrus,postcentral gyrus,and insula were activated under the stimulation of happy faces,and the thalamus,the putamen,and angular gyrus were activated under the stimulation of fearful faces.This shows that emotional faces,as a complex social-emotional stimulus require the synergy of all brain regions to ensure that individuals accurately identify the emotional and social information in faces,and that the overreaction of these activated brain regions may be one of the important manifestations of emotional disorders.This result also implies that the research paradigm of using emotional faces to activate subjects’ emotions in psychological studies is valid and practical.Is the spontaneous neural activity in the brain affected by the previous stimulus after the human brain has received the task stimulus(emotional face)? This was the second research objective in the present study.We acquired resting-state brain images from 21 subjects at baseline level and after stimulus disappearance to explore the pattern of spontaneous neural activity in the brain after the emotional face task from local metrics(amplitude of the low frequency fluctuations,percent amplitude of fluctuation,regional homogeneity)in commonly used resting-state f MRI.It was found that after the disappearance of the emotional face,even when the brain was at rest,the brain state did not immediately return to the baseline level at the beginning,and the brain areas that were abnormally active at this time were all related to the emotional face or the brain area for emotional processing,which suggests that the previous task had an effect on the subsequent neural activity pattern in the brain.This also suggests that after people experience emotional stimulus,the corresponding emotional experience remains even after the stimulus disappears and is continuing to influence the subjects’ subsequent behavior.This result suggests that people should try to avoid the negative effects(e.g.,influencing people’s decision-making behavior)that may result from such situations in psychological research or in daily life.Secondly,this result also suggests that studies using emotional face stimuli need to pay extra attention to the details of the experiment,such as careful control of the emotional context during the experiment and careful consideration of the overall sequence of the experiment.Previously,task state f MRI data have been mostly used for activation and mental/physiological interaction analysis.Since brain signals are in a state of smooth fluctuation when individuals continuously receive the same type of emotional stimuli,the possibility of processing neural activity of this nature in a resting state to improve the utility of task state data is the third goal attempted to be explored in the present study.In the present study,brain imaging data from 21 subjects continuously viewing the same type of face stimulus were collected and low-frequency fluctuation amplitudes were used to explore the differences in brain activity patterns during the period.It is found abnormal brain activity in low-frequency amplitudes during viewing of happy and fear faces compared to neutral faces,and concentrated in the calcarine cortex,precuneus,middle frontal gyrus,and precentral gyrus,which are closely related to visual and emotional processing.Although the analysis in task f MRI data using resting state f MRI methods also yielded some brain areas related to emotional face processing,its use still needs more evidence to verify the validity and reliability of this method in the future.