Subliminal Affective Priming Effect By Faces With Different Valence: Evidence From Event-related Potentials

The brain receives tens of millions of inputs with different levels of emotional significance. However, we experience the majority of them unconsciously. Nevertheless, these inputs can significantly influence our behavior. Studies in subliminal affective priming have found that the subliminal effect is very powerful. Subliminal affective priming has two different meanings:(1) First meaning refers to the phenomenon where subliminal presentation of a prime object shifts subsequent affective evaluation of the supraliminal object in the affective direction of the prime object. (2) Second meaning refers to the phenomenon occurs when the processing of a positive stimulus (e.g., love) is faster and more accurate when it is preceded by a positive stimulus (e.g., sunshine) rather than a negative stimulus (e.g., death). In this study, the dimension of arousal was controlled and two groups of positive and negative faces were selected as priming stimuli. Behavioral analyses were combined with recordings of event-related potential (ERP) to investigate the neural mechanisms of the two different kinds of subliminal affective priming effect.The first kind of subliminal affective priming was studied through experiment 1 by recording ERP to ambiguous neutral faces preceded by subliminal presented positive or negative prime faces. Behavioral results showed that positive and negative prime faces led to valance-consistent biases in affective judgments of ambiguous neutral faces. ERP data showed that subliminal primes differentially influenced anterior N100, N300 and posterior P170 potentials, with larger amplitudes in negative priming trials. These results support the conclusion that the early perceptual analysis of objects, as well as evaluation and selection of objects, is affected by subliminal affective information. Sourcing analysis showed that P170 potentials might be generated from the fusiform gyrus. Experiment 2 investigated the second kind of subliminal affective priming. The study used positive or negative faces as objects preceded by subliminal presented positive or negative prime faces. Behavioral results confirmed the affective priming effect, with faster responses to affectively congruent trails than affectively incongruent trials. ERP data showed that three processing stages involved in the effect. The first stage was characterized by larger ERP amplitudes between 50-100ms in response to primed negative objects. The second stage was characterized by larger VPP amplitudes between 150-250ms in response to primed positive objects, sourcing analysis showed that VPP potentials might be generated from the fusiform gyrus. Results showed the third stage by larger ERP amplitudes between 250-500ms in response to both negative and positive object objects, sourcing analysis showed that P300 effect might be generated from the cingulate gyrus.Taken together, this dissertation revealed that the two different kinds of subliminal affective priming effect have similar neuo-cognitive mechanisms. The early automatic affective detection and the perceptual analysis of objects, as well as evaluation of objects, are affected by subliminal affective information, and may demonstrate the subliminal affective priming effect. The processing is also modulated by the objects’emotional features.The findings of the present dissertation will help increase our understanding of the neuro-cognitive basis of unconscious and emotional processes, which are the forefront issue of Cognitive/Affective Neuroscience nowadays, It will also be of value for clinical diagnosis and therapy of various kinds of mental disorders that more or less all involve an anomalous relationship between unconscious processing and emotional experience.