Abstract
Two important theories in cognitive neuroscience are predictive coding (PC) and the global workspace (GW) theory. A key research task is to understand how these two theories relate to one another, and particularly, how the brain transitions from a predictive early state to the eventual engagement of a brain-scale state (the GW). To address this question, we present a source-localization of EEG responses evoked by the local-global task—an experimental paradigm that engages a predictive hierarchy, which encompasses the GW. The results of our source reconstruction suggest three phases of processing. The first phase involves the sensory (here auditory) regions of the superior temporal lobe and predicts sensory regularities over a short timeframe (as per the local effect). The third phase is brain-scale, involving inferior frontal, as well as inferior and superior parietal regions, consistent with a global neuronal workspace (GNW; as per the global effect). Crucially, our analysis suggests that there is an intermediate (second) phase, involving modulatory interactions between inferior frontal and superior temporal regions. Furthermore, sedation with propofol reduces modulatory interactions in the second phase. This selective effect is consistent with a PC explanation of sedation, with propofol acting on descending predictions of the precision of prediction errors; thereby constraining access to the GNW.
Highlights
Two important theories in current cognitive neuroscience are predictive coding (PC; Rao and Ballard 1999; Friston 2010) and global neuronal workspace (GNW) theory (Dehaene and Changeux 2011)
Sedation with propofol reduces modulatory interactions in the second phase. This selective effect is consistent with a PC explanation of sedation, with propofol acting on descending predictions of the precision of prediction errors; thereby constraining access to the GNW
The key aspect of this change in responsiveness is a coincidence of surprise; that is, a combination of local and global deviants induces an acceleration of the P3, an effect we have called the doublesurprise acceleration effect (Shirazibeheshti et al 2018)
Summary
Two important theories in current cognitive neuroscience are predictive coding (PC; Rao and Ballard 1999; Friston 2010) and global neuronal workspace (GNW) theory (Dehaene and Changeux 2011). The former emphasizes forward and backward exchanges along sensory processing and higher level pathways, with forward connections carrying prediction errors, and backward connections conveying predictions. King et al (2014) argued for the existence of two distinct modes of processing; the first restricted to sensory areas and the latter, the GNW They have suggested that these two modes are experimentally engaged by the local-global task. The first level, which generates the (so-called) local effect, reflects regularity at a short temporal frame of reference, that is, repeated “tones.” In contrast, the second level, which generates the (so-called) global effect, reflects regularity at a longer temporal frame; that is, repeated sequences of tones
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