Default Mode Network activity in relation to Mind Wandering and EEG theta/beta ratio

In spontaneous (resting state) EEG, the ratio between power in the slow
frequency bands (theta) and the fast frequency bands (beta), known as the
theta/beta ratio (TBR) has already directly been negatively related to
executive control like attentional control (Putman et al., 2010, Putman et al.,
2014; Angelidis et al., 2016; Angelidis et al. (in submission); van Son et al.,
(in preparation)). A study by Braboszcz & Delorme (2011) found that increased
theta power and reduced beta power (increased TBR) was specifically present
during mind wandering episodes, and in turn lower theta and higher beta power
during on-task periods. Thus, increased TBR is likely also related to off task
processing. Mind wandering itself is described as a deficit in working memory
and attentional control (McVay & Kane, 2009) and a predictor for performance
errors (Smallwood & Schooler, 2006). Based on these findings, the regularly
observed relation between measurements of spontaneous TBR and attentional
control is possibly caused by episodes of mind wandering increasing the average
TBR in people with worse attentional control. Studying this latter hypothesis
would greatly benefit research on TBR, in healthy people (e.g. Wischnewski et
al., 2016) and ADHD alike (elevated TBR in ADHD is a robust finding; see Arns
et al., 2013, for a meta-analysis).
Focused states such as meditation or mindfulness (commonly seen as a focused
on-task process; opposite of the *off task* state of mind wandering) have been
related to a reduced activation of the default mode network (DMN; Garrison et
al., 2015; Brewer et al., 2011). Additionally, mind wandering was found to
directly activate the DMN (Karapanagiotidis et al., 2017; Smallwood et al.,
2008), making activity of the DMN a possible indicator of mind wandering
processes at the time of activity. This study therefore aims to investigate
mind wandering as an underlying responsible mechanism for the negative relation
between TBR and attentional control.

The first objective of this study is to replicate Braboszcz & Delorme (2011)
and see whether a mind wandering episode is indeed associated with increased
TBR (increased theta and reduced beta). The second objective is whether the
procedurally identically assessed mind wandering episodes are linked to an
increase in DMN coherent activity, as measured during fMRI scanning. The third
and most important objective is to test the hypothesis that quantification of
the EEG TBR change during mind wandering is positively correlated to fMRI DMN
activation during mind wandering. This could greatly increase our understanding
of the functional and neural mechanisms of spontaneous TBR and its relation to
executive control.

This study will be a within subjects observational design. First, a baseline
resting-state EEG measurement is done for eight minutes. Subjects will then
perform a 40 minute breath counting task as in Braboszcz & Delorme (2011) when
EEG is measured. Subsequently, on a different day within a week (the one- week
re-test reliability for TBR is as high as 0.93; see Angelidis et al., 2016) a
certain amount of participants will perform the same 40 minute breath counting
task in an MRI scanner while brain activity is measured. Participants who
during the EEG session report an insufficient number of mind wandering episodes
for reliable statistical analyses, will be excluded from the MRI session.

NA; no risks