Automatic Processing of Emotional Words in the Absence of Awareness: The Critical Role of P2.

Yi Lei,Haoran Dou,Wenhai Zhang,Zhonglu Zhang,Hong Li,Qingming Liu

doi:10.3389/fpsyg.2017.00592

Abstract

It has been long debated to what extent emotional words can be processed in the absence of awareness. Behavioral studies have shown that the meaning of emotional words can be accessed even without any awareness. However, functional magnetic resonance imaging studies have revealed that emotional words that are unconsciously presented do not activate the brain regions involved in semantic or emotional processing. To clarify this point, we used continuous flash suppression (CFS) and event-related potential (ERP) techniques to distinguish between semantic and emotional processing. In CFS, we successively flashed some Mondrian-style images into one participant's eye steadily, which suppressed the images projected to the other eye. Negative, neutral, and scrambled words were presented to 16 healthy participants for 500 ms. Whenever the participants saw the stimuli—in both visible and invisible conditions—they pressed specific keyboard buttons. Behavioral data revealed that there was no difference in reaction time to negative words and to neutral words in the invisible condition, although negative words were processed faster than neutral words in the visible condition. The ERP results showed that negative words elicited a larger P2 amplitude in the invisible condition than in the visible condition. The P2 component was enhanced for the neutral words compared with the scrambled words in the visible condition; however, the scrambled words elicited larger P2 amplitudes than the neutral words in the invisible condition. These results suggest that the emotional processing of words is more sensitive than semantic processing in the conscious condition. Semantic processing was found to be attenuated in the absence of awareness. Our findings indicate that P2 plays an important role in the unconscious processing of emotional words, which highlights the fact that emotional processing may be automatic and prioritized compared with semantic processing in the absence of awareness.

Highlights

Emotional words hold an important place in social communication in the modern world
One is semantic information, which contains the meaning of the word, which activates the left lateral occipitotemporal sulci (Dehaene and Cohen, 2011), inferior frontal gyrus (Mestres-Missé et al, 2008; Chou et al, 2012), Automatic Processing of Emotional Words and angular gyrus (Horwitz et al, 1998; Seghier, 2013); the other is emotional information, which includes the biological value or social significance (Fox et al, 2001), which activates the amygdala (Isenberg et al, 1999; Garavan et al, 2001; Tabert et al, 2001; Hamann and Mao, 2002; Compton et al, 2003; Kensinger and Schacter, 2006; Herbert et al, 2009; GarcíaGarcía et al, 2016), orbitofrontal gyrus and bilateral inferior frontal gyrus (Nakic et al, 2006), anterior cingulate gyrus (Posner et al, 2009), and lingual gyrus (Kuchinke et al, 2005)
We rejected the outliers of reaction time (RT) that were outside the range of ±2.5 standard deviations from the mean (

Summary

Introduction

Emotional words hold an important place in social communication in the modern world. When we see an emotional word, it transmits two main kinds of information. It remains unclear to what extent the emotional and semantic processing of words can take place in the absence of conscious awareness. To render the word stimuli invisible, we adopted an effective paradigm called continuous flash suppression (CFS). This interocular suppression technique has been known as a pivotal tool for exploring the visual awareness (Lin and He, 2009; Eo et al, 2016). In the CFS paradigm, some Mondrian-style images flash successively into the dominant eye steadily, which suppresses the experimental materials projected to the non-dominant eye (Kim and Blake, 2005; Tsuchiya and Koch, 2005)

Methods

Results

Conclusion