Impaired conscious access and abnormal attentional amplification in schizophrenia

Abstract

Previous research suggests that the conscious perception of a masked stimulus is impaired in schizophrenia, while unconscious bottom-up processing of the same stimulus, as assessed by subliminal priming, can be preserved. Here, we test this postulated dissociation between intact bottom-up and impaired top-down processing and evaluate its brain mechanisms using high-density recordings of event-related potentials. Sixteen patients with schizophrenia and sixteen controls were exposed to peripheral digits with various degrees of visibility, under conditions of either focused attention or distraction by another task. In the distraction condition, the brain activity evoked by masked digits was drastically reduced in both groups, but early bottom-up visual activation could still be detected and did not differ between patients and controls. By contrast, under focused top-down attention, a major impairment was observed: in patients, contrary to controls, the late non-linear ignition associated with the P3 component was reduced. Interestingly, the patients showed an essentially normal attentional amplification of the P1 and N2 components. These results suggest that some but not all top-down attentional amplification processes are impaired in schizophrenia, while bottom-up processing seems to be preserved.

Conscious Processing and the Global Neuronal Workspace Hypothesis

“…For instance, the crossing of the threshold for auditory or visual conscious perception is associated with a sudden increase in the P300 component, and only this component vanishes almost entirely under inattention conditions (Berkovitch et al, 2018;Charles et al, 2014;Del Cul et al, 2007) or during sleep (Strauss et al, 2015). The latency for conscious access can in fact be delayed by much more than 300 ms when attention is temporarily distracted by a secondary task (dual-task conditions) (Marti et al, 2015;Marti et al, 2012).…”

Towards a refined mindfulness model related to consciousness and based on ERP

“…According to these theoretical models, an elevated consciousness threshold could result from a bottom-up perceptual impairment (the object remains subliminal) and/ or a lack of topdown attentional amplification (the object remains preconscious) (Dehaene, Changeux, Naccache, Sackur, & Sergent, 2006), preventing conscious access to information (Berkovitch, Del Cul, Maheu, & Dehaene, 2018). Conversely, it seems reasonable to assume that attentional amplification could result in a lower consciousness threshold.…”

Opportunities and challenges for a maturing science of consciousness

“…Similarly, the focus of pain research has moved from understanding the mechanisms of noxious stimulation to understanding the mediators of subjective pain experience 8 . Several studies have also emphasized the role of consciousness science in explaining the symptoms of schizophrenia, as explicit and implicit cognitive processing seem differentially impaired in this condition 9 . As such, translational applications of consciousness research have the potential to create a virtuous cycle, whereby a theoretical understanding of consciousness guides ever more successful clinical interventions, and thus clinical results, which in turn provide critical material to evaluate and refine empirical theories.…”