Rhythms of Consciousness: Binocular Rivalry Reveals Large-Scale Oscillatory Network Dynamics Mediating Visual Perception

Abstract

Consciousness has been proposed to emerge from functionally integrated large-scale ensembles of gamma-synchronous neural populations that form and dissolve at a frequency in the theta band. We propose that discrete moments of perceptual experience are implemented by transient gamma-band synchronization of relevant cortical regions, and that disintegration and reintegration of these assemblies is time-locked to ongoing theta oscillations. In support of this hypothesis we provide evidence that (1) perceptual switching during binocular rivalry is time-locked to gamma-band synchronizations which recur at a theta rate, indicating that the onset of new conscious percepts coincides with the emergence of a new gamma-synchronous assembly that is locked to an ongoing theta rhythm; (2) localization of the generators of these gamma rhythms reveals recurrent prefrontal and parietal sources; (3) theta modulation of gamma-band synchronization is observed between and within the activated brain regions. These results suggest that ongoing theta-modulated-gamma mechanisms periodically reintegrate a large-scale prefrontal-parietal network critical for perceptual experience. Moreover, activation and network inclusion of inferior temporal cortex and motor cortex uniquely occurs on the cycle immediately preceding responses signaling perceptual switching. This suggests that the essential prefrontal-parietal oscillatory network is expanded to include additional cortical regions relevant to tasks and perceptions furnishing consciousness at that moment, in this case image processing and response initiation, and that these activations occur within a time frame consistent with the notion that conscious processes directly affect behaviour.

Cognitive Effort Drives Workspace Configuration of Human Brain Functional Networks

“…Our results demonstrate that workspace formation is a fairly broadband or scale-invariant phenomenon: there is some evidence for task-related increases in global efficiency and physical distance, as well as task-related decreases in clustering and modularity, across all frequency intervals considered (collectively encompassing the range of 8 -120 Hz). This is compatible with various prior reports highlighting the significance of ␣-, ␤-, and ␥-band synchronization as mechanisms for communication between distributed neuronal groups (Rodriguez et al, 1999;Doesburg et al, 2009;.…”

Role of tau protein on neocortical and hippocampal oscillatory patterns

“…This result is supported by three sources of evidence: (i) tau expression is densely expressed in frontal regions (see Fig. 1C) as previously reported (Goerdert et al, 1989;Trojanowski et al, 1989;Santa-Maria et al, 2005;McMillan et al, 2008), (ii) anatomical studies have demonstrated the existence of a monosynaptic pathway from the hippocampus to the frontal cortex (Swanson, 1981;Ferino et al, 1987;Thierry et al, 2000), and (iii) gamma-band synchronization between distant brain regions, including the frontal lobe, has been involved in a variety of cognitive processes, such as perception, attentional selection, and memory (Desmedt and Tomberg, 1994;Von stein et al, 2000;Doesburg et al, 2008Doesburg et al, , 2009Sehatpour et al, 2008). Combining more specific cognitive tests with long-range gamma synchronization measurements could be a more adequate approach at providing novel insights into the role of tau in cognitive functions.…”

Oscillatory activity in prefrontal and posterior regions during implicit letter-location binding

“…However, an alternative interpretation is possible since several authors propose that the prefrontal cortex does not maintain mnemonic representations (Lebedev et al, 2004;Owen et al, 1998;Petrides, 2000;Rissman et al, 2008;Rowe and Passingham, 2001). Instead, prefrontal cortex is considered to participate in controlled processing of the activity of posterior brain regions more directly involved in representing specific features as well as categorical information (Doesburg et al, 2009;Grimault et al, 2009;Kessler and Kiefer, 2005;Mechelli et al, 2004;Rainer and Ranganath, 2002;Serences and Yantis, 2006). This control could be exerted by means of longrange fronto-posterior connections (Grimault et al, 2009;Hasegawa et al, 2000;Kessler and Kiefer, 2005).…”