The Neural Mechnism Of Emotion Modulation On Information Processing Of Sensory System And Attentional Resources

A major constraint on sensory systems and attentional resources is their limited capacity of processing information, which makes people often only pay attention to the most important part of the surrounding environment and prioritize the information based on their current relevance or salience through selective attention. However, what information is significant information related to personal survival and development? Previous studies showed that emotional stimulus plays a very important role in selective attention, compared to neutral stimuli, the emotion laden item will attract more attentional resources, and the process even operates in an automatic, unconscious way. Emotional stimuli also can be divided into positive, negative stimulus. Due to the negative stimulus, especially threatening stimuli is crucial for the survival and development of people, when processed among various emotional information, they can often be prioritized, which will enhance subjects’ perception ability, this phenomenon is known as "negative bias" effect. The effect has been evidenced by-many behavioral studies, for example, in visual search paradigm, the target stimuli with emotional or threatening information, compared to neutral target or friendly stimulus, the detection performance are better. Other paradigms, such as attentional blink paradigm, Stroop task and dot probe paradigm also show that emotional stimuli, especially negative emotions can obtain more processing resources.With the development of cognitive neuroimaging technology, more and more studies use functional magnetic resonance imaging (fMRI) and event related potential (ERP) techniques to investigate the neural mechanisms of the effect of emotion on perception. fMRI technology provides high spatial resolution, researches showed that emotion can modulate the feedback pathway of amygdala and sensory system, and lead frontoparietal attention networks to be involved in the processing of emotional stimuli. In contrast, ERP facilitate researchers to observe brain cognitive processing in short term, emotional studies have shown that the early perceptual processing components, the middle and long latency components related to cognitive resources can be modulated by emotion valence. But previous ERP studies also exist some problems to be solved, such as the N170, as the special face processing component, whether can be modulated by emotion does not have a unified conclusion. P300(index cognitive resource allocation) emotional valence effects have been evidenced by different paradigms, but these paradigms also brings some interference effect that make P300emotion effects be questioned. Besides, many researches lack behavioral evidence which diminish the relationship between behavioral performance and neural mechanisms.The current study uses ERP technology combined with the emotional face visual search paradigm. In visual search paradigm, multiple stimulu are presented simultaneously and subjects’ task is to identify a target wish some special characteristic, the rest stimulus are called distractions. In the present study, targets are emotional face (face threatening or friendly face), distractions are neutral faces, and subjects need to determine whether there is a different facial expression in multiple faces. Half of the stimulus arrays were composed of faces that all showed neutral face expressions. In the other half of the arrays, one of the faces in the array had either a friendly or threatening emotional expression. The experiment aims to compare the behavioral and electrophysiological measures when one inconsistent emotional face appears (threatening vs. friendly). Three components of ERP are involved: N170-a special component for face processing; N2pc-index the allocation of visual spatial attention: P300-index the regulation of cognitive resources. After collecting and analyzing data, the final results are as follows:(1) behavioral data: Participants detected threatening better than friendly target faces with higher accuracy and faster speed, reflecting that the threatening faces could enhanced subjects perception stronger;(2) N170, as a specific component of the face processing, was modulated by emotional valence, showing that the visual search for threatening faces induced a stronger amplitude than friendly faces, in addition, consistent with the previous research results of right hemisphere dominance, which produced the larger N170amplitude on the right electrode;(3) N2pc indexing the allocation of visual spatial attention was also modulated by emotional valence, manifested as threatening face compared to friendly face elicited larger amplitude, reflecting that the threat face began to attract more attention resources;(4) P300,as a key component representing the regulation of cognitive resources was indeed affected by emotion, manifested as threatening face compared to friendly face elicited larger amplitude, suggesting that cognitive resources are invested continuously to ensure that the threatening information could be processed preferentially. In addition, we found that when the target appeared on the left position compared to the right side of the fixation, it evoked larger amplitude. Previous studies have shown that the P300source involved the activity of frontoparietal network, so maybe it reflected top-down modulation;(5) When considering the relationship of behavioral performance and the ERP amplitude, we found no correlation between behavioral performance and the ERP amplitude in early and middle components, only found the reaction time correspond to P300amplitude, which complied with the idea that P300is related to decision making.During emotional information processing, the preferential processing of threatening face and the perceptual ability can be influenced by emotion. The phenomena are supported by different ERP components which provide the neural mechanisms of the cognitive process involving in emotion processing. The cognitive process includes the early sensory process, middle and late process related to continuous allocation of attention resources that can be modulated by emotional valence. Besides, the results shown that N170and P300emotional valence effect are obviously, which served the solution of debate about these two components, and the consistency of behavioral data and P300amplitude also make the results more persuasive. All of these results provide system and direct evidence for the suggestion that emotional information processing involves the modulation of activity of sensory system and regulation of attentional resources.