Negative inhibition is poor in Sub-threshold Depression individuals: Evidence from ERP and a Go/No-go task

Inhibition control refers to the ability of individuals to inhibit task-irrelevant information from entering working memory (Diamond, 2013). Effective inhibition control can protect task-related content in working memory from interference of irrelevant information and prevent limited working memory capacity from being occupied by irrelevant information (Getzmann, Wascher & Schneider, 2018). According to the resource limitation theory, emotional processing and inhibitory control will compete with each other for cognitive resources (Williams et al., 2001), and the loss of inhibitory control of emotional stimuli may make individuals more prone to emotional disorders.

There is a study have shown that major depressive disorder (MDD) may be related to response inhibition deficit (Ardal & Hammar, 2011). Joormann et al. (2010) also believed that one of the reasons for the persistence of negative emotions in MDD individuals may be the inhibitory control defects that make them unable to suppress the interference of negative information. Later, Colich et al. (2016) found that compared with healthy individuals, MDD individuals showed abnormalities in the prefrontal cortex during the inhibition task of negative stimuli, and this encephalic region was mainly responsible for inhibitory control, so it was hypothesized that MDD individuals did have deficit in inhibitory control. This deficit may lead to insufficient inhibition of unrelated negative information entering working memory in MDD individuals, resulting in interference of relevant positive or neutral information in working memory, and hindering individuals from recovering from negative emotions (Dai & Feng, 2011; Joormann, Yoon & Zetsche, 2007).

The classical research paradigm of inhibitory control are Stop-Signal Task(SST), Stroop, and Go/No-go Task. A emotional SST study found that MDD individuals had longer Stop-Signal RT for both negative and positive emotional words than the control group (Lau et al., 2007), showing defects in the inhibition of emotional information. Another study using this paradigm (Liang et al., 2022) further indicated that MDD individuals had deficits in both explicit and implicit emotional response inhibition. Fritzsche et al. (2010) adopted the Stroop task of emotional faces and found that MDD individuals had worse performance in inhibiting sad faces, while their performance under happy faces was relatively intact. Moreover, a meta-analysis of Stroop studies also showed that, compared with healthy individuals, MDD individuals were subjected to a stronger interference effect of negative stimuli (Epp et al., 2012; Joyal et al., 2019), and the higher the severity of depressive symptoms, the greater the interference effect (Epp et al., 2012), which confirmed that MDD individuals had more difficulty in inhibiting negative stimuli.

In another classic paradigm, Go/No-go Task, the frequency of “Go” trails is much higher than that of “No-go” trails, so that the participants establish a prepotent response to “Go” trails, requiring the participants to respond to “Go” trails and inhibit the response to “No-go” trails (Huang & Li, 2021; Erickson et al., 2005; Kyte, Goodyer & Sahakian, 2005). In control group, positive stimuli had shorter RTs when they were the trails of “Go” compared to negative or neutral stimuli (Erickson et al.,2005; Hare et al.,2005), while in MDD individuals, negative stimuli as “Go” trails have shorter RTs (Erickson et al., 2005; Ladouceur et al., 2006; Murphy et al., 1999), and compared with the control group, MDD individuals had a higher rate of false responses to negative words under No-go conditions (Erickson et al.,2005; Kyte, Goodyer & Sahakian, 2005). In other words, compared with positive information, MDD individuals have difficulty in inhibiting negative information, showing a prepotent response to negative stimulus.

SST, Stroop, and Go/No-go Task can serve to investigate for the inhibition process. The SST paradigm requires the participants to stop any response as soon as the stop signal appears. It measures non-selective inhibition, and this type of inhibition is not involved in more complex cognitive processes. In fact, this kind of non-selective inhibition is not very close to people's real life situations, where we tend not to suppress all information, but selectively suppress some information that is unrelated to the current active task. In addition, during the execution of SST, the participants may "intentionally wait" for the stop signal to appear in order to maintain a high successful inhibition rate, leading to deviations in the measurement of Go RT (Fang et al., 2013). Although the Stroop task is the most commonly used task for measuring attention bias, it may not be an ideal method for measuring attention bias due to some interpretation difficulties. For example, delayed responses to emotional words could be due to increased attention to emotional words or an overall delayed response to emotional words (Algom, Chajut, & Lev, 2004). Therefore, the Go/No-go paradigm is chosen in this study.

In further Event-related Potential (ERP) studies, N2 and P3, as ERPs reflecting a higher level of cognition, are often used as neurophysiological evidence. N2 reflects the final stages of automatic processes, associated with cognitive control and response inhibition (Bruin & Wijers, 2002; Kopp et al., 1996; Veen & Carter,2002), is related to attention allocation during conflict monitoring (Donkers & Van Boxtel,2004; Folstein & Van Petten,2008; Ramautar, Kok & Ridderinkhof, 2004; Ramautar, Kok & Ridderinkhof, 2006), evoked when two or more incompatible response tendencies are activated simultaneously (Wauthia & Rossignol,2016; Van Veen & Carter, 2002; Nieuwenhuis et al., 2003). The P3 is thought to be related to processes of response inhibition during “No-go” trials and response execution during “Go” trials (Jodo & Kayama, 1992; Bokura, Yamaguchi & Kobayashi, 2001; Smith, Johnstone & Barry, 2008), reflects conflict resolution and behavior inhibition (Kropotov et al., 2011; Monnart et al., 2016), more specifically, Nogo-P3 mainly reflects the inhibition process (Smith et al., 2013). In addition, P3 also reflects the resources allocated to working memory representations and selective responses (Donchin & Coles, 1988; Kok, 2001; Luck, Woodman & Vogel, 2000). Studies using both emotional and neutral stimuli found lower amplitude of No-go-N2 in the frontal area of MDD individuals (Bailey et al.,2014; Kaiser et al.,2003), suggesting that MDD individuals have impaired early conflict monitoring ability; Other studies have found that the amplitude of No-go-P3 in the frontal area of MDD individuals under negative emotional stimuli is lower than that of the control group, suggesting that the selective deficit of MDD individuals in the inhibition of negative emotional information is also manifested in late conflict resolution and behavioral inhibition deficits (Yu et al.,2017). Gender is another factor affecting ERP results. Women allocate more attention resources to emotions than men do. A “modified emotional” oddball task result shows that under the control of personality factors, the sex differences on N2 and P3 components of the ERPs disappeared (Campanella et al., 2012), which suggests that in the experiment without taking gender as a variable, we should not only strictly control the gender ratio of participants, personality factors should be controlled strictly.

Expanding the research group can explore the change track of inhibitory function along with the development of symptoms, and further clarify the role of emotional information processing in the generation and maintenance of depressive symptoms (Huang & Li, 2021). For example, patients in remission and Sub-threshold depression (SD) individuals with certain depressive symptoms who do not meet the diagnostic criteria for MDD (Judd et al., 1994). At present, there are inconsistent results in studies on inhibition function of these two types of participants. For example, when patients in remission are participants, some studies have shown that their negative processing bias is consistent with that of MDD individuals (Joormann & Gotlib, 2010), while some studies have not found differences in behavioral performance between patients in remission and healthy individuals (Goeleven et al.,2006; Joormann,2004). In addition, a study of SD college students as participants found that their inhibitory control ability was comparable to that of normal groups (zhang et al., 2022).

Compared with patients in remission and MDD individuals, the current research on the inhibition control of SD is not sufficient, and SD is considered to be the early process of MDD, which has an important predictive effect on MDD (Chen, Feng & Jiang, 2016). Therefore, based on previous studies, the classical Go/No-go task combined with ERP technology, to explore the characteristics of negative emotion inhibition between healthy individuals and SD individuals, as well as whether there are differences between neutral emotion and negative emotion inhibition in SD individuals, so as to deepen the understanding and recognition of the occurrence and development of depression (Li et al., 2016)

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