A Precuneal Causal Loop Mediates External and Internal Information Integration in the Human Brain

Abstract

Human brains interpret external stimuli based on internal representations. One untested hypothesis is that the default-mode network (DMN), widely considered responsible for internally oriented cognition, can decode external information. Here, we posit that the unique structural and functional fingerprint of the precuneus (PCu) supports a prominent role for the posterior part of the DMN in this process. By analyzing the imaging data of 100 participants performing two attention-demanding tasks, we found that the PCu is functionally divided into dorsal and ventral subdivisions. We then conducted a comprehensive examination of their connectivity profiles and found that at rest, both the ventral PCu (vPCu) and dorsal PCu (dPCu) are mainly connected with the DMN but also are differentially connected with internally oriented networks (IoN) and externally oriented networks (EoN). During tasks, the double associations between the v/dPCu and the IoN/EoN are correlated with task performance and can switch depending on cognitive demand. Furthermore, dynamic causal modeling (DCM) revealed that the strength and direction of the effective connectivity (EC) between v/dPCu is modulated by task difficulty in a manner potentially dictated by the balance of internal versus external cognitive demands. Our study provides evidence that the posterior medial part of the DMN may drive interactions between large-scale networks, potentially allowing access to stored representations for moment-to-moment interpretation of an ever-changing environment.

Functional networks in prolonged disorders of consciousness

“…It has been identified that the default mode network (DMN) exhibits internal activities, also referred to as the "task-negative network" (Andrews-Hanna, 2012;Andrews-Hanna et al, 2014), whereas the lateral frontoparietal areas related to the network of dorsal attention (DAN; Mallas et al, 2021) and executive control (ECN; Martin-Signes et al, 2019) mediate taskdriven stimuli (Xin et al, 2021;i.e., task-positive network). These two sets of regions are reported to be negatively correlated with healthy adults, anesthetic patients, or patients with prolonged DoC (He et al, 2014;Palanca et al, 2015), both under resting-state or attention-demanding processes (Lyu et al, 2021). In another case, according to the regulating function, the brain networks could be classified into higher order networks [the DMN, ECN, DAN, and salience network (SN)] and sensory-related (perceptual processing) lower order networks including the sensory input auditory network (AN; Braga et al, 2017), visual network (VN;, and sensorimotor network (SMN; Liang et al, 2015; Figure 1).…”

Intrinsic brain dynamics in the Default Mode Network predict involuntary fluctuations of visual awareness

“…For example, recent literature using graph theoretic metrics and information theory has provided a new perspective for how we understand consciousness; it suggests that the posteromedial cortex (PMC; PCC/PCU), standing out as a hub for the whole-brain information exchange, affords the complexity that consciousness emerges from [66][67][68] . There have also been theoretical arguments hinting at the PCU's role in information integration between the internal and external worlds 69,70 , a fundamental component of conscious processing 71,72 .…”

Inhibitory temporo-parietal effective connectivity is associated with explicit memory performance in older adults

“…While the meta-analysis by Uncapher and Wagner was focused on lateral parietal structures, a similar pattern of functional heterogeneity has also been proposed for midline parietal subregions of the DMN (Kernbach et al, 2018). Particularly the dorsal Prc is involved in switching between DMN activity and activity of task-positive networks (Utevsky et al, 2014) and has been shown to be actively engaged in some attention-demanding tasks, possibly mediating the integration of inwardly-directed and externally-directed cognitive processes (Lyu et al, 2021). More recently, the precuneus has also been proposed as a key region for memory acquisition (Brodt et al, 2018; Brodt et al, 2016; Schott et al, 2019).…”