Self-related information (SRI) is regarded as being related to the individual ego but unrelated to others outside the individual. SRI has individual meaning and social value, and it is marked by different processing characteristics, compared with other information [1]). Specifically, individuals have a strong orientation to capture physiological and psychological information about themselves, including self-face, voice, name, and autobiographical memory, according to different SRI cues. This indicates strong self-recognition and self-awareness [2–4].
SRI has the advantage of orientation attention, which enables individuals to transfer their attention to SRI more quickly. Evidence from search and matching studies showed that SRI was searched or matched faster and with higher accuracy [5, 6]. These results indicated SRI has an orientation advantage in attentional capture, and limited attentional resources are allocated to SRI because its entry into conscious processing is preferred [7]. Additionally, in both stimulus-related and stimulus-unrelated tasks, SRI (i.e., self-face, name, and even screen name) could be identified faster and more accurately [8–11]. Moreover, when SRI was presented as a distraction, it would attract attention more automatically, leading to a decline in main task performance [12]. Therefore, SRI may be involuntary, uncontrollable, and unconsciously automated.
The cocktail party effect is an example of such automation. A person can recognize their own name quickly, even if it is mentioned at a noisy cocktail party [13]. Even infants as young as five months already show a preference for their own name [14]. This study further investigates the orientation attention mechanism of SRI using event-related potentials (ERPs), a biomarker reflecting pre-attentional change detection under non-attentional conditions [15]. Previous ERP studies on SRI involving the attention mechanism mainly focused on components such as P2, P300, and N2.
P2 is a positive wave that reaches its peak in the 200-250ms range of visual stimulus recognition [16]. This activity is mainly located in the anterior and central areas of the brain and is associated with attention distribution and stimulus processing and analysis [17, 18], especially perceptual analysis and memory processing [19, 20]. P2 can be divided into anterior P2, which is thought to be associated with early recognition of visual stimuli and posterior P2, which is associated with the early processing of verbal information.
On the one hand, P2 latency represents the time required for early processing stimulus capture and perception analysis [21]. The shorter the latency, the earlier individuals notice the target stimulus. Moreover, the longer the latency, the lower the efficiency of information processing [22]. On the other hand, P2 amplitude might indicate that the participants are already classifying and attending to stimuli based on different visual features in the early stages [23]. The larger the amplitude, the more attention resources would be consumed. Additionally, larger P2 amplitude elicited by semantic recognition might indicate that semantic processing involvement has begun on the basis of distinguishing visual features [24]. Furthermore, evidence has shown that P2 in the anterior and central areas is larger when the stimulus contains target features [25], possibly reflecting the rapid detection of the stimulus features [26, 27], although the demonstrated detection lacked advanced cognitive processing and allocation of control resources [28, 29].
P300 is a classic and widely used electrophysiological index for cognitive processing and brain mechanism study, and can be divided into sub-components, P3a and P3b. These have different distributions, different latency periods, and independent neural origins, reflecting different levels of neural processing [30]. P3a is an early sub-component of P300 with an incubation period of 220-280ms. It is mainly distributed in the anterior central area, and its maximum amplitude is located near the Fz point (posterior frontal lobe), reflecting the time from stimulus presentation to stimulus detection and processing. It is the main marker of orientation response, reflecting the change in attention allocation and working memory representation in response to the stimulus [13, 31]. Studies have shown that the processing of self-related stimuli elicited larger P2 and P3 amplitudes than that of non-self-related stimuli [32]. For example, when individuals process their own names, they react faster, have higher accuracy, and elicit larger P2 and P3 amplitudes [33].
N2 (also known as N200) is a composite negative wave occurring after P2. It appears around 200ms after stimulus presentation, representing the transition between automatic and controlled processing [34]. Studies have found that N2 is closely related to explicit knowledge; moreover, it reflects stimulus recognition, attention transfer, conflict monitoring, novelty or mismatch detection, and cognitive control function [35–37]. As such, it may be related to self-processing [36].
Evidence from face recognition studies shows a significant negative wave in the temporo-occipital region, named N170, is elicited during an incubation period of 170ms. In addition, Bentin and Deouell (2000) found that N170 could only be elicited by human faces under different kinds of stimuli (including non-face images), suggesting that N170 might reflect the specific neural mechanism of human face processing. Additionally, Caharel et al.'s (2002) study provided evidence that viewing self or familiar faces under passive conditions elicited larger N170 than did viewing non-self-related or unfamiliar faces. Furthermore, Keyes et al.’s (2010) group found that the self-face elicited a larger N170 and VPP amplitude in the posterior and anterior middle areas of the brain. However, Peng’s (2003) group found that not all participants elicited N170 in the “learning-recognition” experiment using face pictures as stimuli. Sui et al’s (2006) group found no difference in the amplitude and latency of the N170 elicited by self and other faces in the orientation judgment of self and familiar faces under both attentional and non-attentional conditions; that is, the relevance and familiarity of faces have no effect on N170.
Although there have been some ERP studies on SRI regarding orientation attention, no unified conclusion has been reached. However, there is no existing research on birthplace, a type of SRI with strong social attributes, as a stimulus material. Therefore, in this study, we used the oddball paradigm combined with ERPs to analyze the N170, P2, and N2 components to provide further electrophysiological evidence that SRI could attract orientation attention and, thus, further enrich the connotation of SRI.