Conscious Perception: Time for an Update?

Abstract

words)Understanding the neural mechanisms underlying subjective representation has become a central endeavor in cognitive-neuroscience. In theories of conscious perception, stimulus gaining conscious access is usually considered as a discrete neuronal event to be characterized in time or space, sometimes referred to as a conscious 'episode'. Surprisingly, the alternative hypothesis according to which conscious perception is a dynamic process has been rarely considered. Here, we discuss this hypothesis and envisage its implication. We show how it can reconcile inconsistent empirical findings on the timing of the neural correlates of consciousness (NCCs), and make testable predictions. According to this hypothesis, a stimulus is consciously perceived for as long as it is recoded to fit an ongoing stream composed of all other perceived stimuli. We suggest that this 'updating' process is governed by at least three factors (1) context, (2) stimulus saliency, and (3) observer's goal.Finally, this framework forces us to reconsider the typical distinction between conscious and unconscious information processing.

Multi-spectral oscillatory dynamics serving directed and divided attention

“…Therefore, as one might expect, stronger desynchronized alpha oscillations have often been found to facilitate heightened perception and attention. We found stronger desynchronized alpha oscillations in posterior cortices when attention was directed towards the visual domain relative to when it was directed away completely, as well as when it was divided between sensory modalities, which again aligns with previous literature presenting more robust alpha activity in task-relevant regions during active processing ( Haegens et al, 2011 ; Jones et al, 2010 ; McDermott et al, 2017; Proskovec et al, 2018a , 2019 ; Wiesman et al, 2017b , 2018 ; Wiesman and Wilson, 2019 ).…”

“…In contrast to the theta band, we found significant effects of attention on the alpha oscillatory responses for both the directed and divided attention experiments. A widely accepted mechanism of alpha activity in the brain is the “gating by inhibition” framework ( Bonneford and Jensen, 2012 ; Hanslmayr et al, 2007 ; Händel et al, 2011 ; Jensen et al, 2002 ; Jensen and Mazaheri, 2010 ; Klimesch, 2012 ; Klimesch et al, 2007 ; Spaak et al, 2014 ; Wiesman et al, 2018 ; Wiesman and Wilson, 2019 ), whereby higher levels of alpha oscillatory activity in posterior parieto-occipital cortices index the functional inhibition of incoming visual information. Within this framework, decreases from basal levels of alpha activity represent the dis-inhibition of these cortices towards the goal of visual stimulus processing.…”

“…MEG data acquisition, structural coregistration, preprocessing, and sensor-/source-level analyses for both experiments followed a similar pipeline as a number of previous manuscripts from our laboratory ( Kurz et al, 2017 ; Proskovec et al, 2018a ; Spooner et al, 2018 , 2019 ; Wiesman et al, 2017a ; Wiesman and Wilson, 2019 , 2020 ). All recordings took place in a one-layer magnetically-shielded room with active shielding engaged for environmental noise compensation.…”

“…Neural oscillatory activity is thought to support a diverse array of neural computational functions both within and across cortical regions, and thereby may underlie numerous cognitive and behavioral processes ( Başar et al, 2001 ; Bonneford and Jensen, 2012 ; Klimesch, 1999 ; Musall et al, 2014 ; Proskovec et al, 2018a , 2019 ). Regarding visual attention, previous research using electroencephalography (EEG) and magnetoencephalography (MEG) has found alpha activity (7–13 Hz) to be central to inhibitory processing ( Bonneford and Jensen, 2012 ; Klimesch, 2012 ; McDermott et al, 2017; Proskovec et al, 2018a , 2019 ; van Dijk et al, 2008 ; Wiesman et al, 2018 ; Wiesman and Wilson, 2019 ), theta activity (3–7 Hz) to index early stimulus recognition and top-down modulatory feedback ( Basar et al, 2001 ; Busch et al, 2009 ; Klimesch et al, 2005 ; Landau and Fries, 2012 ; Landau et al, 2015 ; Proskovec et al, 2018a ; Verbruggen et al, 2010 ; Wiesman et al, 2017b ), and gamma activity (>30 Hz) to represent and possibly bind fine-grained stimulus features ( Edden et al, 2009 ; Fries et al, 2001 ; Muthukumaraswamy and Singh, 2013 ; Swettenham et al, 2009 ; Tallon-Baudry, 2009 ; Womelsdorf et al, 2006 ). Studies have also shown that inter-sensory attention reduces alpha and beta power responses to visual stimuli, as well as beta power in primary somatosensory cortex when attending to tactile stimuli ( Pomper et al, 2015 ).…”

Hard criteria for empirical theories of consciousness

“…Even though problems with this contrastive approach have been highlighted recently (Aru et al, 2012;Balsdon & Clifford, 2018;Kleiner & Hoel, 2020;Lau, 2008;Peters & Lau, 2015), all that is needed is the existence of conscious and unconscious states, and methods to contrast them (but see Salti et al, 2019, for an argument that the conscious vs. unconscious dichotomy is misguided). For visual masking and other paradigms, specific procedures have been established to differentiate between conscious and unconscious perception (Morales et al, 2015;Overgaard et al, 2010;Schmidt & Vorberg, 2006).…”