Abstract: Internet Gaming Disorder (IGD) has garnered increasing attention from international communities, and the research on the topic has become more urgent and vital. Existing studies indicate that people with IGD exhibit abnormalities in emotional processing, along with corresponding abnormalities in brain mechanisms.
The abnormal emotional processing in individuals with IGD can be broadly categorized into two facets: biased processing of negative emotional stimuli and challenges in effectively regulating negative emotions. Firstly, people with IGD exhibit abnormal processing biases toward negative emotional stimuli, especially those associated with anger. On one hand, in facial expression recognition tasks, individuals with IGD show processing biases towards angry faces but not sad faces. Anger but not sadness is a typical representative of threatening facial expressions even though both are negative emotions. These imply that processing of various types of negative facial expressions in individuals with IGD rather than broadly comparing negative facial expressions with positive ones needs further investigation. On the other hand, in executive control tasks, people with IGD exhibit abnormal automatization and biases when processing negative interfering stimuli (particularly those associated with anger) compared to neutral and positive interfering stimuli. Furthermore, when confronted with negative interfering stimuli, they tend to experience overactivation of the ventral attention system, hindering the goal-oriented processing of the dorsal attention system. This renders them to be more vulnerable to the interference of negative stimuli, which then requires increased cognitive resources for effective executive control. Hence, future studies could focus on the emotional characteristics of interfering stimuli and compare the effects of interference across different types of emotions. Secondly, negative stimuli elicit excessive emotional arousal in people with IGD, yet they encounter difficulties in effective emotional regulation. In terms of the brain mechanism of emotional arousal, the activation of the bilateral insula and right ventral anterior cingulate cortex is enhanced when IGD individuals are exposed to negative stimuli. Moreover, the brain mechanisms related to emotional regulation in people with IGD are also abnormal. For instance, when experiencing a negative event during gaming, IGD individuals show weaker activation of the left middle frontal gyrus (MFG) and decreased functional connections between the left MFG and the right amygdala than recreational gamer users. Additionally, the theoretical models of IGD emotional regulation are evolving. In the early stage of addiction, individuals with IGD often turn to online gaming as a coping mechanism to alleviate negative emotions. This process establishes a connection between internal triggers of negative emotions and online gaming-generated reinforcing experiences. Subsequently, this linkage tends to intensify over time. In the late stage, an automatic response to game cues and a heightened craving for gaming will appear in response to triggers. Consequently, non-adaptive emotional regulation might play a more direct role in the early development of IGD.
In a word, the emotional processing abnormalities among people with IGD have certain internal connections. Specifically, IGD individuals who exhibit processing biases towards negative emotional stimuli display heightened sensitivity to such stimuli in terms of brain activity. Moreover, people with IGD tend to experience more intense emotional arousal when confronted with negative stimuli. Hence, effective emotional regulation is crucial for people with IGD to maintain a normal emotional state. However, people with IGD find it difficult to effectively regulate negative emotions and tend to adopt a non-adaptive emotional regulation strategy—online gaming. Then, the negative reinforcement generated in this process may further aggravate addiction and form a vicious circle.
Future research could focus on the following aspects: First, pinpointing the gender ratio of the participants and the effects of the participants' long-term and short-term emotional states on the results of the emotional processing studies. Second, diversifying the design of emotional stimuli to investigate various facets of IGD emotional processing. For example, exploring the processing of dynamic facial expressions, the intonation in emotional expressions, and body expressions. Third, it would be beneficial to present cross-channel emotional information, examining the integrated processing of multi-sensory emotional stimuli in individuals with IGD. Fourth, incorporating the event-related potentials (ERP) technique can be instrumental in exploring the temporal dynamics of emotional processing in IGD, given its high time resolution. Fifth, to further clarify the relationship between IGD and impaired social function, it is important to investigate the group emotional processing of IGD individuals, particularly focusing on group facial expression processing. Sixth, exploring ways to effectively enhance the emotional regulation ability of IGD individuals. Therefore, investigating more representative methods according to the structural relationship of general emotional regulation strategies warrent furture exploration. Finally, the emotional processing of adolescents with IGD remains a largely understudied area. Existing theoretical models suggest that emotional regulation may have a more direct impact on early IGD. Therefore, in terms of the time course, intervention in the emotional regulation of adolescents with IGD may have a better effect.

Key words: Internet Gaming Disorder (IGD), facial expression, emotional processing bias, emotional regulation