Motivation and emotion/Book/2020/Attentional bias for emotional stimuli

Overview
Attentional bias for emotional stimuli refers to one's elevated attention to information with enhanced emotional saliency (Gibb et al, 2016). The ability to flexibly allocate one’s attention to relevant cues in the environment is essential for adaptive functioning and deficits in this ability play a central role in various domains of psychopathology (Gibb et al, 2016). For individuals without cognitive disturbance, attention is generally biased towards positive stimuli (Gotlib, Krasnoperova & Joorman, 2004, as cited in Disner et al, 2011). However, attentional bias towards negative emotional stimuli has been linked to the aetiology and maintenance of psychological disorders (Blicher, Reinholdt-Dunne, Hvenegaard, Winding, Petersen & Vangkilde, 2020). For example, compared to non-anxious individuals, anxious individuals display a preference to attend to threatening compared to neutral stimuli (Theorn, Grueschow, Ehlert, Ruff & Kleim, 2016). In contrast to this emerging body of literature on attention to negative emotional stimuli, attentional bias to positive stimuli has received considerably less attention (Theorn et al, 2016). The literature posits that attentional bias comprises observable characteristics including; enhanced engagement such that threat-related stimuli are detected faster than non-threatening stimuli; slower disengagement, whereby one requires substantial cognitive effort to disengage attention from a threatening stimulus compared to a neutral stimulus and; attentional avoidance which refers to faster disengagement (Cisler & Koster, 2009; Cisler, Bacon & Williams, 2009; Blicher et al, 2020). These mechanisms along with the neural underpinnings of attentional bias will be examined and discussed in this chapter. Furthermore, contemporary empirical findings pertaining to the effect of attentional bias on psychopathology will be reviewed. Lastly, the implications of attentional bias on an emerging novel treatment for depression and anxiety, known as attentional bias modification training, will be investigated.

Nature of attentional bias in humans


Attentional bias towards emotional stimuli serves to elicit adaptive responses (Gibb et al, 2016). A substantial body of contemporary research contends that emotional salience modulates attention (Blicher et al, 2020). A practical way to understand the nature of attentional bias is to examine the experimental techniques that measure this construct. Experimental research using the stroop task has indicated that individuals more readily pay attention to emotional compared to neutral stimuli (Blicher et al, 2020). In this task, participants are presented with a screen and are required to name the colour that the words are printed in as quickly as possible (Blicher et al, 2020; Cisler & Koster, 2010). Attentional bias is operationalised as the latency to name the colour of emotional stimuli relative to neutral stimuli (Blicher et al, 2020). The premise of the emotional stroop task is that naming the colour of a word is slowed when the stimulus has an emotional meaning (Yiend, 2010; Vuilleumier, 2005). Similarly, the dot-probe task operationalises attentional bias as the latency to respond to a target probe in the location of emotional stimuli relative to the location of neutral stimuli (Blicher et al, 2020). Please see figure 1. for further details. Moreover, in studies utilising eye tracking methodology, depressed individuals were significantly slower to disengage their attention from depression-related images than healthy control participants (Sanchez et al, 2013, as cited in Blicher et al, 2020). Collectively, the abovementioned empirical research indicates that attentional bias comprises several key elements. These include enhanced engagement which is characterised by faster engagement, delayed disengagement, and attentional avoidance which is denoted by faster disengagement. Contemporary literature has attributed this greater salience of emotional information impacting on the allocation of attention to intrinsic properties of the brain, as will be examined below (Martin & Jones, 1995; Vuilleumier, 2005).

Neural mechanisms underlying attentional bias to emotional stimuli


Contemporary research indicates that attentional biases are the result of disruptions in cortico-limbic circuitry, whereby initial attention is influenced by activation of the amygdala in response to emotionally salient information (Gibb et al, 2016). That is, attentional biases are the result of hyperactivation in the limbic system in response to salient emotional stimuli that are not effectively down-regulated by areas of the prefrontal cortex (Disner et al, 2011; De Raedt & Koster, 2010). It has been found that shifting attention away from emotional stimuli necessitates top-down intervention from cortical structures including the lateral prefrontal cortex (LPFC) (Beevers, Clasen, Stice, & schnyer, 2010, as cited in Disner et al, 2011). Specifically, the ventrolateral prefrontal cortex (VLPFC) is associated with control over stimulus selection while the dorsolateral prefrontal cortex (DLPFC) is responsible for executive functioning (Disner et al, 2011) (See Figure 2. for visual depiction of LPFC). This demonstrates that the LPFC plays an important role in cognitive control (Disner et al, 2011; Helfinstein et al, 2014, as cited in Gibb et al, 2016). A large body of empirical research indicates that negatively biased attention in individuals and consequent depressive symptoms could be attributed to LPFC function (Disner et al, 2011; Vuilleumier, 2005). For example, compared to individuals with mild depressive symptoms, those with severe depressive symptoms have been found to display weaker activation in the inferior frontal gyrus (a brain region in the LPFC) when required to shift attention away from negative stimuli (Beevers et al, 2010; Gibb et al, 2015). Conversely, no differences in LPFC activity were observed between the two participant groups when shifting attention away from neutral stimuli (Beevers et al, 2010). This research indicates that cortico-limbic circuitry including the amygdala and LPFC modulate attentional bias towards emotional stimuli. Collectively, this research demonstrates that the nature of attentional bias to emotional stimuli is underpinned by neural mechanisms.

Focus questions:
 * Explain how the dot-probe paradigm and stroop test each provide a measure of attentional bias
 * What is the definition of enhanced engagement? In what way does enhanced engagement differ from slower disengagement and attentional avoidance?
 * Which brain regions are involved in attentional bias for emotional (negative) stimuli? Discuss the distinct roles that each of these regions play in modulating attentional bias for negative emotional stimuli.
 * What role does the lateral prefrontal cortex play in influencing attentional bias for emotional stimuli?
 * How does the hyperactivation in the limbic system influence attentional bias for emotional stimuli?

Implications of attentional bias towards emotional stimuli for psychopathology
A substantial body of research asserts that attentional bias is associated with emotional difficulties (Gibb et al, 2016). Cognitive models emphasise that selective attention plays a key role in the aetiology and maintenance of emotional disorders (Blicher et al, 2020). Specifically, attentional biases in information processing of emotional stimuli are theoretically and empirically linked to emotional difficulties (Beck, 1976, as cited in Blicher et al, 2020), as will be further investigated below. While depression and anxiety have both been associated with attentional bias toward negative stimuli, differences exist regarding how this bias manifest between the disorders (Browning, Holmes & Harmer, 2010). Research has identified that anxiety is characterised by abnormalities in the initial engagement of attention, whereas depression is associated with difficulties related to disengaging attention (Mathews & MacLeod, 2005, as cited in Browning, Holmes & Harmer, 2010; De Raedt & Koster, 2010). For example, Armstrong and Olatunji (2012) conducted a meta-analysis with research utilising eye-tracking methodology. The data indicated that individuals with higher levels of anxiety displayed impaired disengagement from threat as well as threat vigilance during visual search and free viewing. Conversely, depressed individuals displayed increased maintenance of attention on negative stimuli during free viewing (Armstrong & Olatunji, 2012). Overall, the findings in the literature demonstrate that attentional bias plays a key role in the development and maintenance in both anxiety and depression.

Implications for depression
The inability to disengage from negative stimuli has been found to further exacerbate depressive symptoms and perpetuate the positive feedback loop of dysphoric symptoms (Hasler et al, 2004, as cited in Disner et al, 2011; Wells & Beevers, 2010). Furthermore, empirical research suggests that in depression, attentional focus on a negative stimulus prevents the processing of more positively valenced information (Disner et al, 2011). There is substantial research that corroborates this notion. These studies indicate that individuals with depression show increased attention for negative stimuli and decreased attention for positive stimuli compared to healthy control individuals (Kellough, Beevers, Ellis & Wells, 2008; Disner, 2011). This effect has been attributed to inefficient attentional disengagement from negative stimuli, which as noted above, has been linked to decreased activity in the right VLPFC and right DLPFC (Disner et al, 2011). Thus, reduced activity in these regions contributes to difficulty with attentional disengagement from negative emotional stimuli, thus further perpetuating increased exposure to depressive stimuli (Disner et al, 2011). Furthermore, the anterior cingulate cortex (ACC) is involved in normal inhibitory processing whereby increased ACC activity is indicative of successful inhibition of positive stimuli (Disner et al, 2011). Conversely, for individuals with depression, greater activation of the ACC is required to successfully inhibit attention to negative stimuli (Eugene, Joorman, Cooney, Atlas & Gotlib, 2010; Elliot, Rubinsztein, Sahakian & Dolan, 2002; Mitterschiffthaler, 2008, as cited in Disner et al, 2011). This demonstrates that healthy individuals require greater cognitive effort to divert attention away from positive stimuli whereas individuals with depression require greater cognitive effort to divert attention away from negative stimuli (Disner et al, 2011). Thus, ACC dysfunction disrupts the efficient inhibition of negative stimuli and consequently contributes to biased attention towards negative information (Disner et al, 2011). These findings corroborate the notion that attentional bias towards emotional stimuli influences the development and maintenance of both depression and anxiety.



From a theoretical perspective, Beck (1967) proposed a cognitive-emotional model of depression which provides a rationale for the association between attentional bias and depression (Beck, 1967, as cited in Disner et al, 2011). The model asserts that biased acquisition and processing of information plays a key role in the aetiology and maintenance of depression. Specifically, this model posits that latent schemas play a key role in attentional bias towards negative stimuli which consequently perpetuates depressive symptoms (Beck, 1967, as cited in Disner et al, 2011). A latent schema is a cognitive concept denoted by representations of stimuli that are stored internally which can be activated by internal or external environmental circumstances (Beck, 1967, as cited in Disner et al, 2011). For example, adverse events such as loss of employment may influence the development of negative self-referential thoughts. Beck posits that activation of these maladaptive schemas heighten one’s vulnerability for depression, and consequently may influence deficits in cognitive processing of emotional stimuli (Disner et al, 2011). See Figure 3. for further details. Beck’s model is an example of cognitive-emotional theory which may provide important implications for the mechanisms underlying attentional bias for emotional stimuli.

Implications for anxiety
Ample literature exists which demonstrates that attentional biases towards threat play a pivotal role in the development and maintenance of anxiety disorders. Facilitated attention and difficulty in disengagement comprise the specific components of attentional bias that modulate anxiety symptoms (Cisler & Koster, 2009). Research conducted by Grafton et al. (2012, as cited in Blicher et al, 2020) implemented the attentional assessment task and included participants both high and low in affectivity. They identified that higher negative affectivity was associated with both enhanced engagement to, and delayed disengagement from, negative stimuli, particularly when this was anxiety-related (Grafton et al, 2012). Furthermore, Grafton and MacLeod (2014) elucidated this notion by identifying that enhanced engagement and delayed disengagement from negative stimuli both characterise an elevated risk of anxiety vulnerability. In a similar vein, the attentional assessment task has been employed to examine attentional mechanisms in individuals high and low in ruminative disposition. Scholars including Grafton et al (2016) and Southworth et al (2017) identified that elevated ruminative disposition was associated with delayed disengagement from negative compared to positive stimuli. Collectively, empirical research suggests that anxiety is associated with enhanced engagement to negative stimuli (Grafton & Macleod, 2016) and delayed disengagement from negative stimuli via cognitive processes including rumination (Grafton & MacLeod, 2014; Rudaizky et al., 2014). This evidence demonstrates that attentional bias for emotional stimuli modulates anxiety.

Focus questions:
 * What is the difference between anxiety and depression regarding how attentional bias for emotional stimuli is manifested? Which of these disorders is associated with difficulties related to disengaging attention, and which is characterised by difficulties with the initial engagement of attention?
 * Greater activation of which brain region is required to successfully inhibit attention to negative stimuli in individuals with depression?
 * According to Beck’s cognitive model of depression, what concept plays a key role in modulating emotional attentional bias? Note that this concept heightens one’s vulnerability for depression.

Attentional bias towards positive emotional stimuli predicts stress-resilience


Substantial literature exists corroborating the association between an attentional bias towards emotionally negative stimuli and vulnerability to stress-related psychopathology (Thoern et al, 2016). This suggests that attentional bias towards positive emotional stimuli may be a protective factor against psychopathology and may thus contribute to stress resilience (Thoern et al, 2016). Just as a negative attentional bias has been identified to influence heightened anxiety vulnerability, an attentional bias to positive stimuli plays an important role in promoting stress resilience and psychological well-being (Thoern et al, 2016). Specifically, an attentional bias towards positive stimuli facilitates adaptive stress regulation by inhibiting negative emotional responses to stressors (Dandeneau et al, 2005, as cited in Theorn et al, 2016). This notion is premised on the fact that endorsing an attentional bias towards positive stimuli facilitates an adaptive process of antecedent emotion regulation that operates before an emotional response is fully generated, thus leading to resilience via positive emotions (Theorn et al, 2016). Experimental research conducted by Theorn et al (2016) implemented the dot probe task to examine the relationship between positive attentional bias and stress resilience in a non-clinical sample. It was identified that an attentional bias towards happy, but not away from angry, face stimuli predicted greater self-reported stress resilience. Moreover, an attentional bias towards angry stimuli was found to moderate this relationship such that the positive attentional bias was only predictive of resilience in participants who also experienced an attentional bias towards angry faces. This was attributed to the notion that an attentional bias towards positive information may only be effective for promoting resilience in individuals with a heightened sensitivity to negative stimuli, while those without negative attentional bias are less in need of this protective process (Theorn et al, 2016). These findings provide significant implications for the treatment of psychological conditions as it demonstrates that attentional bias towards positive emotional stimuli promotes stress-resilience.

Attentional bias modification training (ABMT): An emerging novel treatment for psychological conditions
The paradigm shift in the literature towards positive psychology has caused an emerging surge in the examination of attentional bias towards positive emotional stimuli (Hakamata et al, 2010) (see Figure 4.). Optimism bias and positive attention bias have been attributed to a common underlying neural network comprising specific activations in the anterior and posterior cingulate cortices with functional connections to the limbic system, particularly the amygdala (Kress & Aue, 2019). Attentional bias modification training (ABMT) has been developed in light of the association between positive attentional bias and enhanced psychological well-being (Hakamata et al, 2010). ABMT utilises repeated training to attend to specific target stimuli and simultaneously disregard others (Kress & Aue, 2019). Recent neuroscientific evidence indicates that ABMT reduces amygdala and insula activation toward emotional (threatening) stimuli (Browning, Holmes, Murphy, Goodwin & Harmer, 2010; Taylor et al, 2014, as cited in Kress & Aue, 2019). Moreover, ABMT has been associated with increased frontal control over stimulus selection and it can thus be inferred that it may reduce anxiety and depressive symptoms (Browning, Holmes, Murphy, Goodwin & Harmer, 2010). A significant benefit to ABMT includes that the process of identifying a positive stimulus among negative stimuli serves an adaptive function and can be easily transferred to everyday life situations. Furthermore, ABMT has been consistently associated with positive emotional outcomes including stress reduction, and enhanced self-esteem (Dandeneau & Baldwin, 2009, as cited in Kress & Aue, 2019). Moreover, there is ample empirical evidence that higher attentional bias towards positive stimuli is related to enhanced stress-resilience as well as elevated positive mood (Tamir & Robinson, 2007, as cited in Theorn et al, 2016). Collectively, this literature demonstrates that research pertaining to positive emotional attentional bias provides significant and practical implications for the treatment of psychological conditions.

Focus questions:
 * How does an attentional bias towards positive stimuli facilitate stress resilience? What mechanisms are involved?
 * In a non-clinical sample, Theorn et al (2016) found that an attentional bias towards happy, but not away from angry, face stimuli predicted greater self-reported stress resilience. How do you think the results would compare to a sample of participants with anxiety or depressive disorders? Explain your predictions.
 * In Theorn et al’s (2016) study, what was the rationale behind why positive attentional bias was only predictive of resilience in those who also endorsed an attentional bias towards angry faces?

Conclusion
Key take-home messages:
 * Collectively, this synthesis of contemporary literature and theory demonstrates that the nature of human attentional bias is underpinned by neural mechanisms. Specifically, attentional biases were found to be the result of disruptions in cortico-limbic circuitry whereby initial attention is influenced by activation of the amygdala in response to emotionally salient information. That is, attentional biases are the result of hyperactivation in the limbic system in response to emotionally salient stimuli that are not effectively down-regulated by areas of the lateral prefrontal cortex.
 * Attentional bias towards negative emotional stimuli has been linked to the aetiology and maintenance of psychological disorders and thus significantly implicates anxiety and depression (Blicher et al, 2020).
 * Anxiety is characterised by abnormalities in the initial engagement of attention, whereas depression is associated with impaired attentional disengagement from negative emotional stimuli.
 * In depression, attentional focus on a negative stimulus prevents the processing of more positive emotional information (Disner et al, 2011). Deficits in attentional disengagement from negative stimuli has been attributed to decreased activity in the LPFC and ACC.
 * According to Beck’s (1967) cognitive model of depression, latent schemas perpetuate depressive symptoms and thus influence deficits in the cognitive processing of emotional stimuli.
 * These findings demonstrate that attentional bias for emotional stimuli significantly implicates anxiety and depression.
 * Lastly, it was established that attentional bias towards positive emotional stimuli predicts stress-resilience. This is because it facilitates adaptive stress regulation by inhibiting negative emotional responses to stressors. Based on this research, ABMT was developed. ABMT reduces amygdala and insular activation toward emotional stimuli (Browning et al, 2010). Thus, attentional bias provides significant implications for a novel treatment of psychological disorders.