EEG Frequency Changes Prior to Making Errors in an Easy Stroop Task

ORIGINAL RESEARCH published: 31 October 2017 doi: 10.3389/fnhum.2017.00521 EEG Frequency Changes Prior to Making Errors in an Easy Stroop Task Rachel Atchley* , Daniel Klee and Barry Oken Department of Neurology, Oregon Health and Science University, Portland, OR, United States Background: Mind-wandering is a form of off-task attention that has been associated with negative affect and rumination. The goal of this study was to assess potential electroencephalographic markers of task-unrelated thought, or mind-wandering state, as related to error rates during a specialized cognitive task. We used EEG to record frontal frequency band activity while participants completed a Stroop task that was modified to induce boredom, task-unrelated thought, and therefore mind-wandering. Methods: A convenience sample of 27 older adults (50–80 years) completed a computerized Stroop matching task. Half of the Stroop trials were congruent (word/color match), and the other half were incongruent (mismatched). Behavioral data and EEG recordings were assessed. EEG analysis focused on the 1-s epochs prior to stimulus presentation in order to compare trials followed by correct versus incorrect responses. Results: Participants made errors on 9% of incongruent trials. There were no errors on congruent trials. There was a decrease in alpha and theta band activity during the epochs followed by error responses. Edited by: Xiaolin Zhou, Peking University, China Reviewed by: Xiaolan Song, Zhejiang Normal University, China Bertille Somon, Office National d’Études et de Recherches Aérospatiales, France *Correspondence: Rachel Atchley Received: 29 June 2017 Accepted: 16 October 2017 Published: 31 October 2017 Citation: Atchley R, Klee D and Oken B (2017) EEG Frequency Changes Prior to Making Errors in an Easy Stroop Task. Front. Hum. Neurosci. 11:521. doi: 10.3389/fnhum.2017.00521 Conclusion: Although replication of these results is necessary, these findings suggest that potential mind-wandering, as evidenced by errors, can be characterized by a decrease in alpha and theta activity compared to on-task, accurate performance periods. Keywords: mind-wandering, attention, theta, alpha, executive control INTRODUCTION Mind-wandering is a form of off-task attention that has been associated with negative affect and rumination (Scheeringa et al., 2008; Lagopoulos et al., 2009; Hasenkamp et al., 2012; Sood and Jones, 2013; Levinson et al., 2014; Wilson et al., 2014; Smallwood and Schooler, 2015). Mindwandering can be an adaptive and even a natural state, but it offers potential drawbacks as well. Smallwood and Schooler (2006) hypothesized that mind-wandering is associated with executive control and that mind-wandering precipitates attentional shifts that can impair task performance and awareness of external sensory information. Certain inflexible and negative forms of mindwandering, such as perseverative cognition, can have deleterious effects on the health and mood of persons with Major Depressive Disorder (Ottaviani et al., 2015), for example. Previous studies have assessed mind-wandering using objective brain activity measures such as attentional P3 event-related potential (ERP) markers in conjunction with behavioral and self-report measures (Smallwood et al., 2008), fMRI for default-mode network assessment and self-report (Mason et al., 2007), and fMRI for brain region activity levels during mind-wandering Frontiers in Human Neuroscience | www.frontiersin.org 1 October 2017 | Volume 11 | Article 521 Atchley et al. EEG Frequency Changes During Mind-Wandering of accuracy while facing no significant time pressure for a response. Thus, all errors, including those potentially related to category response inhibition failure, were likely mind-wandering errors. Decreased theta activity has been particularly related to worse cognitive performance including working memory (Onton et al., 2005; Sauseng et al., 2007; Nigbur et al., 2011). Decreased alpha can be intuited as a characteristic of mind-wandering when drawing from previous work in which increased attention, specifically meditation, showed increased alpha (Lagopoulos et al., 2009; Ahani et al., 2013, 2014). Although there are several potential contributors to errors on a task potentially related to mind-wandering, we hypothesized that mind-wandering would be characterized by decreases in theta and alpha frequencies across the frontal regions of the brain. (Weissman et al., 2006). It was found that mind-wandering naturally occurs as sustained attention waxes and wanes (Smallwood et al., 2008), that default mode network recruitment was greater during periods of higher self-reported mindwandering (Mason et al., 2007) and that the start of mindwandering events can be traced to pre-stimulus brain activity in the right prefrontal regions and the anterior cingulate (Weissman et al., 2006). Additional ERP studies on the topic of mind-wandering have found that the amplitude of the P1 component, as an early occurring ERP that occurs in response to stimuli, was decreased when participants reported they were engaged in task-unrelated thought (Baird et al., 2014). Furthermore, the Baird et al. (2014) study conducted a time-frequency analysis and observed a decrease in theta-band cortical phase-locking over the parietal areas, as well as increased cortical processing during task-relevant action. The authors interpreted these findings as evidence that there is an increase in neural processing in an effort to recouple attention following a mind-wandering event. Recent research by Baldwin et al. (2017) explored the effects of mind-wandering on behavioral responses. Participants who completed various simulated driving tasks were asked to selfreport mind-wandering and were also intermittently prompted to report whether they were experiencing mind-wandering. While mind-wandering events affected performance on the driving task in terms of reduced driver speed and less lane variability, the electrophysiological findings of this study included an increase in alpha-band power during mind-wandering and a reduced amplitude in the P3a component during auditory probes. Event-related potential studies of mind-wandering show that attentional ERP components such as P3 are reduced during task-unrelated thought. For example, Kam et al. (2012) also studied the effects of mind-wandering on behavior and found that the P3 attentional component was reduced when participants self-reported mind-wandering during a motor tracking task, and that errors on the task were also increased. These results support the findings of the study Baldwin et al. (2017) and suggest that mind-wandering can have functional effects on motor control and behavior. O’Connell and colleagues found that mind-wandering, as lapsing attention, was characterized by an increase in alpha band activity up to 20 s before errors were made on a task in which the goal was to identify a rare-occurring visual target. After a mis (...truncated)