Abstract:

Attentional bias towards threat information is a common phenomenon in Posttraumatic Stress Disorder (PTSD) individuals. A number of studies have investigated the processing characteristics and internal mechanisms of attentional bias by using eye-movement technology. it is found that factors influenced the three components are distinct. 
First, facilitated attention is the consequence by the interaction of the threat stimulus type and the eye movement indicators. PTSD individuals are more likely to be alert to threat words, which is not only related to the interference of pictures and words in the recognition process, but also affected by arousal, salience and complexity of stimulus. Furthermore, the smaller visual angle presented in previous studies may also accelerate the attentional capture of threat words. In addition, the inconsistent selection of eye movement measures may also cause the difference of the results of attention directed acceleration: the first fixation latency is not sensitive to the component due to the inability to measure the apparent eye movement. Moreover, the spatial indicators are more suitable to investigate this processing to threat words, but pupil index is more appropriate to threat pictures. 
Second, PTSD individuals do not have the difficulty in attention disengagement to threat words. It may be related to preview, information density, and unconscious binding. Words preview leads to rapid processing; however, it is not available to continuously capture the attention because of low information density. Besides, the unconscious binding of “static-words” also makes it difficult to show the difficulty in attention disengagement to threat words. 
Third, the absence of attentional avoidance to threat information may be a long-term self-protection strategy adopted by PTSD individuals, and this result will not be affected by analysis methods, stimuli types, and presentation time. Therefore, it is more likely to be the mechanism of “facilitated attention - difficulty in attention disengagement”. Indeed, compared with behavioral response time, eye tracking technology can monitor the time course of attention while PTSD individuals look at the threat stimuli. On the one hand, it can deeply understand the attention characteristics of PTSD individuals caused by different types of traumatic events, and on the other hand, it can verify relevant attention-biased stage theory. From the observation of phenomenon to the theoretical construction, it is a more comprehensive investigation of the attentional bias processing mechanism to this type of affective disorder. 
Future research may also should to pay attention to the following aspects. First of all, whether researchers can maximize the advantages of eye movement technology is still worth discussing. They can construct the unique attentional bias eye movement pattern and corresponding eye movement model of PTSD individuals from multiple dimensions based on the perspective of eye movement mechanism, for example, age. The PTSD rate of American children and adolescents is higher than that of American adults caused by the same experience, and compared with PTSD adults, PTSD children will show more hypervigilance and traumatic memories of repeated intrusions. In addition, the immaturity of the eye physiological system of children and adolescents may lead to more limitations or inconsistent eye movement patterns. The superposition of these differences may cause heterogeneity in the eye movement patterns of attentional bias between different PTSD groups. Consequently, it is necessary to construct corresponding attentional bias eye movement patterns and theoretical models from the age level for researchers. Second, when researchers make full use of eye tracking technology to investigate PTSD attention bias, they also need to combine multiple technologies to investigate the threat attention bias mechanism of PTSD individuals from a multimodal perspective, such as physiological indicators, event-related potentials, and so on.

Key words: Posttraumatic Stress Disorder, attentional bias, eye-movement