Research reportThe resting state questionnaire: An introspective questionnaire for evaluation of inner experience during the conscious resting state
Introduction
A significant part of our wakeful brain activity is self-directed rather than goal-directed, consisting of periods of uncontrolled stream of thoughts, recollection of past episodes of our life, analysis of current inner sensations, thinking about problems, or planning for the future. This particular mind state, also referred to as “random episodic silent thinking” (REST) [1], “default mode” [34], or “conscious rest” [4], [28], has received increased attention in recent years because the corresponding brain state is both a physiological baseline [34] and a state of high neural activity and energy metabolism [38].
Several investigators have identified a large-scale cortical network with activity that appears to be maximal during REST and reduced during goal-directed cognitive tasks [4], [28], [30], [31], [37]. This network seems to support, at least in part, self-oriented activities [1], [4], [7], [12], [19], [28]. Modulation in brain default mode network activity due to life events, such as development [15], [16], learning [27], aging [2], [13], and neuropsychiatric diseases [36], [39], [43], has also been studied with the underlying hypothesis that the associated behavioral/cognitive changes or deficits may be related to such modulation.
A major concern in all neuroimaging experiments addressing the resting state is the assessment of the participant's mental content while being imaged. First, the researcher must ensure that the participant has adequately followed instructions. Second, although some investigators have made efforts to perform online evaluation of the participant's mental content while in the resting state [8], [31], avoiding interaction with the participant being scanned is recommended to prevent switching between a free mode and a goal-directed mode. As a consequence, assessment of participant mental content during a functional magnetic resonance imaging (fMRI) study must rely on a posteriori introspective evaluation.
We previously attempted to complete such an introspective post-fMRI evaluation in a group of participants who were scanned at rest with positron emission tomography (PET) [28]. This evaluation was qualitative, however, and restricted to having the participants indicate whether their mental content during the resting state consisted mainly of mental imagery or inner language. However, the conscious resting state is a mind state during which various types of thought, not necessarily limited to language and imagery, alternate. Here we report on a new questionnaire, the resting state questionnaire (ReSQ) that we designed to obtain a quantitative and detailed evaluation of the mental content during the resting state. A total of 180 healthy adults, including women and men and right- and left-handers, completed this questionnaire, and English and French versions are available upon request.
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Participants and experimental context
The present study included 180 young (26.0 ± 6.6 years, mean ± SD), healthy volunteers. The participants had no history of any psychiatric, neurological or medical conditions. The sample was balanced for sex (91 women) and handedness (90 left-handers). All participants gave their informed written consent, and the local ethical committee (CPP de Basse-Normandie, France) approved the study. Participant handedness was assessed using the Edinburgh Handedness Inventory [33], and educational level was
Participants
Table 2 shows handedness, age, and educational level for the sample. The sample average handedness scores were 88.6 ± 18.0 (N = 90, mean ± SD) for the right-handers and −61.4 ± 38.6 (N = 90) for the left-handers. The sample mean age was 26.0 ± 6.6 years (N = 180, range = [18.1–51.3] years) without sex or handedness effect (ANOVA). The mean educational level of the participants was 15 ± 3 years (mean ± SD, range = [11–20] years), indicating an average of 3 years at a university, with left-handers having a
Discussion
The development of neuroimaging techniques that allow correlation of subjective experience with a neuroanatomical substrate has triggered a new interest in the study of the neural bases of inner experience, a phenomenon long considered to be beyond the reach of scientific investigations [20]. Consciousness access is the phenomenon by which information is accessible to the mind for report. We can therefore access our thinking (we can introspect) and we can report accurately about our
Conclusions and perspectives
We conclude that ReSQ is a robust and easy tool for exploration of the mental activities of healthy participants during the resting state of an fMRI experiment. The results are consistent with those from studies investigating inner experience under natural conditions. These behavioral data add some evidence to the self-referential memory and planning activity nature of the resting state. The paper also provides a normative set of data, built on sex and handedness equilibrated in a participant
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