Deactivation of the Default Mode Network as a Marker of Impaired Consciousness: An fMRI Study

Julia Sophia Crone,Stefan Golaszewski,Martin Kronbichler,Gunther Ladurner,Eugen Trinka,Yvonne Höller,Tianzi Jiang

doi:10.1371/journal.pone.0026373

Julia Sophia Crone, Stefan Golaszewski + Show 5 more

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https://doi.org/10.1371/journal.pone.0026373

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Abstract

Diagnosis of patients with a disorder of consciousness is very challenging. Previous studies investigating resting state networks demonstrate that 2 main features of the so-called default mode network (DMN), metabolism and functional connectivity, are impaired in patients with a disorder of consciousness. However, task-induced deactivation – a third main feature of the DMN – has not been explored in a group of patients. Deactivation of the DMN is supposed to reflect interruptions of introspective processes. Seventeen patients with unresponsive wakefulness syndrome (UWS, former vegetative state), 8 patients in minimally conscious state (MCS), and 25 healthy controls were investigated with functional magnetic resonance imaging during a passive sentence listening task. Results show that deactivation in medial regions is reduced in MCS and absent in UWS patients compared to healthy controls. Moreover, behavioral scores assessing the level of consciousness correlate with deactivation in patients. On single-subject level, all control subjects but only 2 patients in MCS and 6 with UWS exposed deactivation. Interestingly, all patients who deactivated during speech processing (except for one) showed activation in left frontal regions which are associated with conscious processing. Our results indicate that deactivation of the DMN can be associated with the level of consciousness by selecting those who are able to interrupt ongoing introspective processes. In consequence, deactivation of the DMN may function as a marker of consciousness.

Highlights

Patients with a disorder of consciousness (DOC) like patients in the vegetative state and patients in minimally conscious state (MCS) have survived severe brain injury to a state of wakefulness with no or minimal awareness of themselves and their environment
As postulated by the European Task Force on Disorders of Consciousness to avoid associations with a vegetable-like condition [3], we will further refer to patients in the vegetative state as patients with unresponsive wakefulness syndrome (UWS)
Coherent spontaneous low-frequency fluctuations in the resting brain are organized into distinct brain networks such as the default mode network (DMN) [22] including medial parietal and frontal brain regions like the posterior cingulate cortex (PCC) and the ventral anterior cingulate cortex [23]

Summary

Introduction

Patients with a disorder of consciousness (DOC) like patients in the vegetative state and patients in minimally conscious state (MCS) have survived severe brain injury to a state of wakefulness with no or minimal awareness of themselves and their environment (see Laureys et al [1] and Owen et al [2] for further review). A resting state network like the DMN is characterized by, first, high metabolism during resting state [24,25]; second, functional connectivity during rest [26]; and third, deactivation during various attention-demanding cognitive tasks [27,28]. The third feature of the DMN, task-induced deactivation, has only been assessed in a single-case study in which an UWS patient showed a reduced pattern of deactivation in regions of the DMN compared to the time of recovery 7 months later [31]. This finding implies that deactivation of the DMN may be related to conscious processing

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