Functions of the posterior cingulate cortex and default network

The posterior cingulate cortex (PCC) is an intriguing yet understudied brain region implicated in diverse cognitive functions and neurological disorders. Progress in understanding the human PCC has been hindered by the absence of a clear rodent homolog, inconsistent lesion-behavior deficits in humans, and limitations in studying the region with noninvasive electrophysiological methods. However, the advent of functional neuroimaging has highlighted the PCC's central role within the default mode network (DMN) and its broader functional role as an associative, transmodal, cortical region. Recent advances in precision imaging have further refined the functional neuroanatomy of the PCC, revealing its complex subregional organization and network connectivity profiles. For example, the PCC is a convergence point for dorsal executive and ventral mnemonic systems, with distinct subregions (dorsal PCC and ventral PCC) differentially contributing to cognitive control, decision-making, and episodic memory. This emphasis on higher-order cognition highlights the often-striking dissociation of the PCC/DMN from primary sensory-motor processing. However, emerging evidence suggests that the PCC operates at the apex of cortical processing hierarchies, supporting temporally extended cognitive behaviors while also integrating sensory updates relevant to ongoing tasks. This review synthesizes recent advances in understanding the human PCC, emphasizing its functional connections to various cognitive systems beyond the DMN and its relative separation, though not isolation, from primary sensory-motor systems. Together, these facets allow the PCC to support the representation of past and future behavioral scenarios by integrating prior experience with ongoing sensory feedback.