Posterior cingulate cross-hemispheric functional connectivity predicts the level of consciousness in traumatic brain injury

Abstract

Previous studies have demonstrated that altered states of consciousness are related to changes in resting state activity in the default-mode network (DMN). Anatomically, the DMN can be divided into anterior and posterior regions. The anterior DMN includes the perigenual anterior cingulate cortex and other medial prefrontal cortical regions, whereas the posterior DMN includes regions such as the posterior cingulate cortex (PCC) and the temporal parietal junction (TPJ). Although differential roles have been attributed to the anterior and posterior DMN regions, their exact contributions to consciousness levels remain unclear. To investigate the specific role of the posterior DMN in consciousness levels, we investigated 20 healthy controls (7 females, mean age = 33.6 years old) and 20 traumatic brain injury (TBI) patients (5 females, mean age = 43 years old) whose brain lesions were mainly restricted to the bilateral frontal cortex but retained a well-preserved posterior DMN (e.g., the PCC and the TPJ) and who exhibited varying levels of consciousness. We investigated the intra- and cross-functional connectivity strengths (FCSs) between the right/left PCC and the right/left TPJ and their correlation with consciousness levels. Significant reductions in both the intra- and cross-hemispheric FCSs were observed in patients compared with controls. A significant correlation with consciousness levels was observed only for the cross-hemispheric PCC-TPJ FCS but not for the intra-hemispheric PCC-TPJ FCS. Taken together, our results show that the cross-hemispheric posterior DMN is related to consciousness levels in a specific group of patients without posterior structural lesions. We therefore propose that the PCC may be central in maintaining consciousness through its cross-hemispheric FC with the TPJ.

Spontaneous Brain Activity Predicts Task-Evoked Activity During Animate Versus Inanimate Touch

“…This result suggests that PACC's scale-free resting state properties are specifically related to a differentiation of animate from inanimate stimuli in task-evoked activity. Analogous findings of specific relations between scale-free properties and mental features have been observed regarding the self (Huang et al 2016) and consciousness (Zhang et al 2017). This is well in line with our finding of animate task evoked activity being specifically predicted by resting state PLE (rather than ALFF, ReHo, and SD).…”

“…Recent functional magnetic resonance imaging (fMRI) studies demonstrated that the degree of LRTCs predisposes the neural processing of motor (Palva et al 2013) and sensory stimuli (Huang et al 2015;He 2011) as well as private self-consciousness (Huang et al 2016). Together, these studies suggest that spontaneous activity's scale-free properties may shape task-evoked activity and associated behavioral features including consciousness (Northoff and Huang 2017;Zhang et al 2017). The exact neural mechanisms of such rest-stimulus interaction including the relevant neuronal features (He 2013;Huang et al 2015;Northoff et al 2010) as well as the exact kind of external stimuli that are preferentially mediated by the spontaneous activity's scale-free properties remain unclear.…”

Dissociation of the subjective and objective bodies: Out‐of‐body experiences following the development of a posterior cingulate lesion

“…This seems to share a phenomenological basis with the difficulty in localizing the self in space associated with a PCC lesion. Furthermore, in the resting brain, the PCC is functionally connected to the TPJ (Mars et al , ); the PCC and TPJ both lie in the posterior region of the default‐mode network (one of the central resting brain networks; Zhang et al , ). Anatomically, the PCC projects to the macaque homologue of the inferior parietal lobule and the superior temporal sulcus, both of which are TPJ regions (Parvizi, Van Hoesen, Buckwalter, & Damasio, ).…”

How Energy Supports Our Brain to Yield Consciousness: Insights From Neuroimaging Based on the Neuroenergetics Hypothesis

“…Specifically, current evidence highlights the role of the posteromedial cortex (PMC) in regulating the consciousness levels in humans as a central hub between the networks (Crone et al, 2015 ; Silva et al, 2015 ; Zhang et al, 2017 ). The PMC, including the PCC and precuneus, is one of the most metabolically active brain regions.…”