How do the normal pains of everyday life, such as headaches and backaches, influence our ability to think? Recent studies suggest that healthy individuals in pain also show deficits in working memory, or the cognitive process of holding and manipulating information over short periods of time.
Prior research suggests that pain-related impairments in working memory depend on an individual’s level of emotional distress. Yet the specific brain and psychological factors underlying the role of emotional distress in contributing to this relationship are not well understood.
A new study, titled “Modeling neural and self-reported factors of affective distress in the relationship between pain and working memory in healthy individuals,” and published in the journal Neuropsychologia sought to address this gap in the literature.
The study was authored by recent University of Miami psychology Ph.D. graduate students Steven Anderson, Joanna Witkin, and Taylor Bolt and their advisors Elizabeth Losin, director of the Social and Cultural Neuroscience Laboratory at the University of Miami; Maria Llabre, professor and associate chair of the Department of Psychology; and Claire Ashton-James, senior lecturer at the University of Sydney.
The study used publicly available brain imaging and self-report data from the Human Connectome Project (HCP), a large-scale project sponsored by the National Institutes of Health (NIH) which aims to construct a map of the complete structural and functional connections in the healthy human brain.
Brain imaging and self-report data from 416 HCP participants were analyzed using structural equation modeling (SEM), a statistical technique for modeling complex relationships between multiple variables. In the 228 participants who reported experiencing some level of pain in the 7 days prior to the study, the authors found that higher pain intensity was directly associated with worse performance a commonly used test of working memory, the n-back task.
In the n-back task, participants are shown a series of letters and asked whether the letter they are seeing appeared some number of screens previously. The more screens back in the sequence participants are asked to recall, the more working memory is required.
In addition, the authors found that higher pain intensity was indirectly associated with worse working memory performance through increased activity in a particular region in the center of the frontal cortex during the n-back task, the ventromedial prefrontal cortex (vmPFC).
The vmPFC is a brain region involved in pain, affective distress, and cognition. Interestingly, the relationship between everyday pain and vmPFC brain activity in this study is similar to prior findings in patients with chronic pain.
“We found that healthy participants with even low levels of reported pain had different levels of activity in the vmPFC during the n-back task compared to healthy participants who didn’t report pain. Surprisingly, this pattern of activity was more similar to patients with chronic pain than healthy patients who are exposed to pain manipulations in a laboratory,” said Witkin.
In contrast, the authors found that certain aspects of emotional distress reported by participants, such as anger, fear, and perceived stress, were not associated with working memory performance.
“Studies looking at the relationship between pain and cognition have typically focused on patients with chronic pain or research participants given experimentally-induced pain,” noted Anderson.
“Even though pain is a common experience for many people, we know surprisingly little about how the everyday experience of pain impacts cognition.”
Using the publicly available HCP dataset allowed the researchers to include data from a much larger group of participants than is typical in brain imaging studies due to the high cost of brain scans.
This large sample enabled authors to use structural equation modeling, a statistical technique that allows for the understanding of complex relationships between multiple variables that in this case may help explain how pain decreases working memory. The authors note that their findings have potential implications in both clinical and non-clinical settings.
“This study highlights the real impact that pain can have on our ability to think even in healthy people, and points how this may come about in the brain,” said Losin.
Chronic pain is a major socioeconomic health issue. The estimated annual cost of treating chronic pain is $635 billion, which surpasses the annual cost of treating any other chronic illness.1 Cost related to loss of work productivity represents one of the largest proportion of the total societal cost caused by chronic pain.2
It is estimated that lost work productivity brought about by chronic pain costs up to $61.2 billion per year, accounting for almost 30% of the total work-related burden of pain conditions in the United States.3 Yet, although the association between chronic pain and lost worker productivity is well established4–7, the mechanisms that undergird this relationship remain to be fully articulated.
One avenue for investigating how the experience of persistent pain negatively influences vocational commitments and actions is to compare the attitudes, beliefs, and motivational styles of persons with chronic pain who have remained at work with those who have either disengaged from work due to pain or who are pain free.
For example, drawing from a nationally representative sample of U.S. adults with chronic pain by means of random digit dialing procedures, Karoly, Ruehlman and Okun8 found that continued employment, in contrast to being on disability, was negatively related to a belief in a medical cure for pain and to the tendency to catastrophize. Attitudes reflecting task persistence (e.g., “I do not let my pain get in the way of what I want to do”) positively predicted continued employment.
In a separate study focusing on a national sample of working adults, Karoly and Ruehlman9 compared the responses of managers with persistent or episodic pain to those with no pain on the Goal Systems Assessment Battery (GSAB). Inspired by a cybernetic model of adaptive control systems10, the GSAB gauges a set of governing functions underlying the process of goal regulation and pursuit.
The Directive Function consists of measures of Value (This goal is important to me) and Self-Efficacy (I possess the necessary skills to attain this goal). The Control Function assesses Goal Planning, Self-Criticism, and Self-Reward. The Arousal Function includes measures of goal-related Positive and Negative Affect. They found (among other things) that those with pain tended to report lower levels of goal-centered self-efficacy along with heightened levels of goal-based self-criticism and negative arousal. Although some motivational and attitudinal patterns have been reported in cross-sectional surveys11, these findings provide limited understanding of how momentary experiences of pain adversely influence certain individuals more than others in their work.
In contrast to static, cross-sectional surveys and between-group comparisons, recently researchers have used daily diaries to explore the within-person dynamics of goal-related thought, affective reactions, and vocational performance as they unfold in real time. For example, Karoly, Okun, Enders, and Tennen12 asked adults with chronic pain who were working full- or part-time to complete a telephonic diary for 21 days.
Each morning, participants answered questions about their anticipatory goal cognitions (or goal schemas) that assess the extent to which participants think their self-selected work-related and lifestyle goals are important, their planning for how to pursue them, and their expectancy about having opportunities to pursue these goals.
In addition, pain intensity levels were measured three times per day (morning, afternoon, and evening) and work and lifestyle goal pursuit were assessed in the afternoon and evening. Multilevel modeling revealed that when a participant experienced greater than usual pain intensity in the morning, he or she reported less positive schematic thoughts about work and lifestyle goals, which was then related to decreased likelihood of goal pursuit in the afternoon and evening.
The Role of Negative Affect
Although some intriguing relationships between momentary pain and work-related goal schema and goal pursuit emerged from the above-noted analyses, other factors may likewise figure prominently in the process of goal pursuit among workers with chronic pain. Negative affect represents one such potentially important state-level factor.
For example, the momentary experience of high negative affect can activate an information processing bias which may render individuals hyper-vigilant for potential threat.13,14 It has been also suggested that negative affect functions as part of a harm-avoidance motivational system15,16 that biases overall information processing and that can constrain one’s choice of goals and impact self-regulation.17 Thus, it is reasonable to presume that negative affect can function as a potential disruptor of daily goal pursuit.
Working Memory as a Moderator
Self-regulation refers to the processes involved in motivating goal-directed perceptions, thoughts, actions, emotions, and physiological reactions in response to contextual challenges via the mobilization of specific skills, resources, and strategic knowledge18–21.
Workers with chronic pain face a great many daunting regulatory challenges to the flexible and effective performance of their job-related duties including pain-derived threats to their ability to control their attentional focus and to access goal-relevant information in support of vocational objectives.
A specific cognitive resource system believed to enable people to stay on course toward their goals (of whatever sort) in the face of interference from within (e.g., pain) or from external sources (e.g., distraction) has been labeled working memory (WM).22,23
WM has been defined as a “system comprising encoding, maintaining, and retrieving from long term memory the information, goals, and strategies necessary to perform a task.23 The importance of WM for goal pursuit was demonstrated in a study by Avery, Smillie and de Fockert24 in which the experimental loading of WM led to performance decrements in the pursuit of achievement goals.
WM is also considered particularly important as a clinical target because it is presumed to play a key role in avoiding errors in the planning, management, and execution of complex behaviors. Moreover, there are also a number of studies that have examined the effects of working memory on pain and negative affect. For instance, Legrain, Crombez, Verhoeven, and Mouraux (2011)25, experimentally demonstrated that working memory can prevent participants from experiencing involuntary attention capture by acute nociceptive stimuli while maintaining attention to non-pain goals.
Also, individuals with higher working memory capacity are less likely to report negative affective reactions induced by the cold-pressor task.26 Hence, having measured several so-called “executive functions” in our pre-diary assessment, we elected to examine WM as a potential moderator of the effects of pain intensity and negative affect on work-goal interference.
The present study
Our previous study27 examined the effect of morning pain and affect on afternoon pain’s interference with work goal pursuit and evening work goal progress, as well as the moderating effects of pain acceptance and pain catastrophizing in a community sample of adults who completed 21-day diary. The hypotheses tested in the present study are derived from the same data set, but extend this work by focusing on whether WM moderates the within-person associations between both morning pain and morning negative affect and pain’s interference with work goal pursuit in the afternoon and evening. Although the outcome of the present study (i.e., a composite of afternoon and evening pain’s interference with work goal pursuit) is slightly different from that employed in the Mun et al. study27 (i.e., afternoon pain’s interference with work goal pursuit), we nonetheless expect that both morning pain and morning negative affect will be positively associated with pain’s interference with work goal pursuit in the afternoon and evening.
We hypothesized that the significant, positive within-person associations between (a) pain intensity and (b) negative affect and pain’s interference with work goal pursuit in the afternoon/evening would be moderated by WM. Individuals with higher WM were expected to be less impacted than those with lower WM by the experience of greater than usual pain and negative affect in the morning for the following reasons: (1) WM is known to assist the active mental representation of personal goals and values28–30 and (2) WM functions as a top-down source of resistance to extraneous, attention-capturing stimuli31,32 and may act to shield goal-relevant information from interference.33 In testing these hypotheses, several individual difference factors known to exert some influence on WM and on pain intensity, negative affect, and goal pursuit served as control variables, including sleep quality, level of emotional distress (i.e., depression, anxiety, and stress), chronic pain severity, duration of chronic pain, age, and gender34–40. Figure 1 depicts the hypothetical model tested in the present study.
The present study was designed to test whether the effects of morning pain intensity and negative affect upon pain’s interference with afternoon and evening work goal pursuit were moderated by individual difference in WM. We expected WM to serve a critical role in protecting goal-relevant information from distractions that result from higher than usual negative affective arousal and from pain intensity.
WM did not moderate the within-person association between morning pain intensity and afternoon/evening ratings of pain’s interference with work goal pursuit. Yet it nonetheless attenuated the positive association between morning negative affect and afternoon and evening pain’s interference with work goal pursuit.
Thus, our findings provide a warrant for other ecologically nuanced observational or intervention studies to further explore the influence of WM on the ongoing pursuit of important personal goals in the face of pain and negative affect.
More information: Steven R. Anderson et al, Modeling neural and self-reported factors of affective distress in the relationship between pain and working memory in healthy individuals, Neuropsychologia (2021). DOI: 10.1016/j.neuropsychologia.2021.107766