Intracranial Electrophysiology of the Human Default Network

Abstract

The human default network (DN) plays a critical role in internally directed cognition, behavior, and neuropsychiatric disease. Despite much progress with functional neuroimaging, persistent questions still linger concerning the electrophysiological underpinnings, fast temporal dynamics, and causal importance of the DN. Here, we review how direct intracranial recording and stimulation of the DN provides a unique combination of high spatiotemporal resolution and causal information that speaks directly to many of these outstanding questions. Our synthesis highlights the electrophysiological basis of activation, suppression, and connectivity of the DN, each key areas of debate in the literature. Integrating these unique electrophysiological data with extant neuroimaging findings will help lay the foundation for a mechanistic account of DN function in human behavior and cognition.

Neurochemical correlates of scene processing in the precuneus/posterior cingulate cortex: A multimodal fMRI and 1H‐MRS study

“…More substantively, our lack of significant correlation for scene‐task related PCu/PCC BOLD with local GABA+ and Glx could be consistent with accounts that different populations of neurons within posterior DMN have somewhat distinct functions. Single unit recording studies have recently revealed that neural populations in PCu/PCC associated with “default mode” activity (i.e., showing task‐negative responses) may be distinct from those involved in active (e.g., mnemonic or scene‐construction) processing (Daitch & Parvizi, ; Fox et al, ). In addition, patterns of DMN network connectivity are somewhat different during rest versus autobiographical memory and future thinking (Bellana, Liu, Diamond, Grady, & Moscovitch, ).…”

“…Much of our knowledge of the role of PCu/PCC in scene-related cognition is based on measurements tied to neuronal activity, including blood-oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI) in humans (Bzdok et al, 2015;Spreng, Mar, & Kim, 2009) and single unit recording studies in both humans (Fox, Foster, Kucyi, Daitch, & Parvizi, 2018) and nonhuman primates (Dean, 2006;Sato, Sakata, Tanaka, & Taira, 2010). Further evidence comes from neuropsychological investigations of scene-based processing following brain lesions (Futamura et al, 2018;Suzuki, Yamadori, Hayakawa, & Fujii, 1998), including Alzheimer disease-linked neurodegeneration (Chan et al, 2016;Irish et al, 2015).…”

Spatial dynamics within and between brain functional domains: A hierarchical approach to study time‐varying brain function

“…Furthermore, regarding default mode, intracranial electrophysiology studies demonstrate different patterns of activity across multiple regions of the default mode over time (for review please read (Fox et al, 2018)). The concept of spatial dynamics and variations in regions’ associations over time was also confirmed via the amplitude of BOLD signal.…”

Affective neuroscience of self‐generated thought

“…At the same time, there has been a dramatic increase in the number of functional neuroimaging and electrophysiological studies aiming to elucidate the neural correlates of self‐generated cognition. A general picture of the brain networks involved in self‐generated thought is gradually emerging, and initial steps have been taken to correlate the specific sensory modality and emotional valence of self‐generated mental content with specific patterns of brain activity …”