Does the Prefrontal Cortex Play an Essential Role in Consciousness? Insights from Intracranial Electrical Stimulation of the Human Brain

Raccah, Omri; Block, Ned; Fox, Kieran C. R.

doi:10.1523/jneurosci.1141-20.2020

Cited by 51 publications

(54 citation statements)

References 139 publications

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“…While negative results should be treated with caution, it is interesting that a recent review of massive stimulation study failed to find evidence for specific perceptual modulations following frontal lobe stimulations ( Raccah et al. 2021 ) again in agreement with converging evidence from functional specialization and cortical lesion data.…”

Section: Three Criteria For Identifying Candidates For Conscious Contentmentioning

confidence: 66%

Local neuronal relational structures underlying the contents of human conscious experience

Malach

2021

Neuroscience of Consciousness

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While most theories of consciousness posit some kind of dependence on global network activities, I consider here an alternative, localist perspective—in which localized cortical regions each underlie the emergence of a unique category of conscious experience. Under this perspective, the large-scale activation often found in the cortex is a consequence of the complexity of typical conscious experiences rather than an obligatory condition for the emergence of conscious awareness—which can flexibly shift, depending on the richness of its contents, from local to more global activation patterns. This perspective fits a massive body of human imaging, recordings, lesions and stimulation data but opens a fundamental problem: how can the information, defining each content, be derived locally in each cortical region. Here, I will discuss a solution echoing pioneering structuralist ideas in which the content of a conscious experience is defined by its relationship to all other contents within an experiential category. In neuronal terms, this relationship structure between contents is embodied by the local geometry of similarity distances between cortical activation patterns generated during each conscious experience, likely mediated via networks of local neuronal connections. Thus, in order for any conscious experience to appear in an individual’s mind, two central conditions must be met. First, a specific configural pattern (“bar-code”) of neuronal activity must appear within a local relational geometry, i.e. a cortical area. Second, the individual neurons underlying the activated pattern must be bound into a unified functional ensemble through a burst of recurrent neuronal firing: local “ignitions”.

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Section: Three Criteria For Identifying Candidates For Conscious Contentmentioning

confidence: 66%

Local neuronal relational structures underlying the contents of human conscious experience

Malach

2021

Neuroscience of Consciousness

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“…Collectively, our results are aligned with the theoretical framework of global neuronal workspace theory, which attempts to describe the neurocognitive mechanisms of conscious access ( Dehaene et al, 1998 ; Dehaene and Changeux, 2011 ; Mashour et al, 2020 ). Access consciousness refers to the broad cognitive availability of sensory information, which often is measured based on report or task performance (as in this study), and is distinct from phenomenal consciousness, which has been defined as experience itself and hypothesized to be independent of post-perceptual processing in anterior cortex ( Block, 2005 ; Raccah et al, 2021 ). According to workspace theory, a reverberant network that includes both prefrontal and posterior parietal cortex serves to sustain, amplify, and make available neural representations, with a ‘broadcasting’ effect that allows access by otherwise non-conscious cognitive processors ( Mashour et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

Recovery of consciousness and cognition after general anesthesia in humans

Mashour

Palanca

Basner

et al. 2021

eLife

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Understanding how the brain recovers from unconsciousness can inform neurobiological theories of consciousness and guide clinical investigation. To address this question, we conducted a multicenter study of 60 healthy humans, half of whom received general anesthesia for three hours and half of whom served as awake controls. We administered a battery of neurocognitive tests and recorded electroencephalography to assess cortical dynamics. We hypothesized that recovery of consciousness and cognition is an extended process, with differential recovery of cognitive functions that would commence with return of responsiveness and end with return of executive function, mediated by prefrontal cortex. We found that, just prior to the recovery of consciousness, frontal-parietal dynamics returned to baseline. Consistent with our hypothesis, cognitive reconstitution after anesthesia evolved over time. Contrary to our hypothesis, executive function returned first. Early engagement of prefrontal cortex in recovery of consciousness and cognition is consistent with global neuronal workspace theory.

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“…Of note, these subcortical regions send projections to cortex (Briand et al, 2007;Hoover and Vertes, 2007) but there is limited evidence of a direct role of cortical areas in regulating behavioral arousal. The cortical mechanisms of consciousness have been a subject of recent debate, with specific controversy as to whether the prefrontal cortex plays a causal role (Boly et al, 2017;Odegaard et al, 2017;Raccah et al, 2021). We recently demonstrated that cholinergic stimulation of prefrontal cortex-via local carbachol delivery-in anesthetized rats induced wakefulness despite the continued presence of sevoflurane anesthesia (Pal et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Inactivation of Prefrontal Cortex Delays Emergence From Sevoflurane Anesthesia

Huels

Groenhout

Fields

et al. 2021

Front. Syst. Neurosci.

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Studies aimed at investigating brain regions involved in arousal state control have been traditionally limited to subcortical structures. In the current study, we tested the hypothesis that inactivation of prefrontal cortex, but not two subregions within parietal cortex—somatosensory barrel field and medial/lateral parietal association cortex—would suppress arousal, as measured by an increase in anesthetic sensitivity. Male and female Sprague Dawley rats were surgically prepared for recording electroencephalogram and bilateral infusion into prefrontal cortex (N = 13), somatosensory barrel field (N = 10), or medial/lateral parietal association cortex (N = 9). After at least 10 days of post-surgical recovery, 156 μM tetrodotoxin or saline was microinjected into one of the cortical sites. Ninety minutes after injection, rats were anesthetized with 2.5% sevoflurane and the time to loss of righting reflex, a surrogate for loss of consciousness, was measured. Sevoflurane was stopped after 45 min and the time to return of righting reflex, a surrogate for return of consciousness, was measured. Tetrodotoxin-mediated inactivation of all three cortical sites decreased (p < 0.05) the time to loss of righting reflex. By contrast, only inactivation of prefrontal cortex, but not somatosensory barrel field or medial/lateral parietal association cortex, increased (p < 0.001) the time to return of righting reflex. Burst suppression ratio was not altered following inactivation of any of the cortical sites, suggesting that there was no global effect due to pharmacologic lesion. These findings demonstrate that prefrontal cortex plays a causal role in emergence from anesthesia and behavioral arousal.

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Does the Prefrontal Cortex Play an Essential Role in Consciousness? Insights from Intracranial Electrical Stimulation of the Human Brain

Cited by 51 publications

References 139 publications

Local neuronal relational structures underlying the contents of human conscious experience

Local neuronal relational structures underlying the contents of human conscious experience

Recovery of consciousness and cognition after general anesthesia in humans

Inactivation of Prefrontal Cortex Delays Emergence From Sevoflurane Anesthesia

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