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categories: ["minds"]categories: ["minds"]tags: ["consciousness", "neuroscience", "integrated information", "global workspace", "anaesthesia", "experiment"]tags: ["consciousness", "neuroscience", "integrated information", "global workspace", "anaesthesia", "experiment"]summary: "The minimal neural activity jointly sufficient for a specific conscious experience, and the experimental programme that tries to identify it."summary: "The minimal neural activity jointly sufficient for a specific conscious experience, and the experimental programme that tries to identify it."updated: "2026-07-27"updated: "2026-10-29"issues: ["The 2023 open letter on whether IIT is testable is mentioned without a citation.", "Recurrent processing, higher-order and attention schema theories are stated without sources."]issues: ["The 2023 open letter on whether IIT is testable is mentioned without a citation.", "Recurrent processing, higher-order and attention schema theories are stated without sources."]------ lines 36–43 → 36–4322 unchanged lines not shown
## Defining an NCC## Defining an NCC David Chalmers's standard formulation distinguishes the *content* NCC — the minimal neural systemDavid Chalmers's standard formulation distinguishes the *content* NCC (the minimal neural systemwhose state determines what a person is conscious of — from the *background* or state NCC, thewhose state determines what a person is conscious of) from the *background* or state NCC, theconditions of arousal that make consciousness possible at all.[^chalmers2000] Brainstem structuresconditions of arousal that make consciousness possible at all.[^chalmers2000] Brainstem structuresthat regulate wakefulness are part of the second but plainly not the seat of visual experience.that regulate wakefulness are part of the second but plainly not the seat of visual experience. lines 45–51 → 45–511 unchanged line not shown
"Sufficient" is weaker than "identical to": a correlate can be a reliable accompaniment without"Sufficient" is weaker than "identical to": a correlate can be a reliable accompaniment withoutbeing the thing itself, which is why NCC results do not by themselves settle whether a machine or anbeing the thing itself, which is why NCC results do not by themselves settle whether a machine or an[[organoids|organoid]] is conscious. A further complication is that many candidate correlates are[[organoids|organoid]] is conscious. A further complication is that many candidate correlates areconsequences of consciousness rather than constituents — attention, working memory, and theconsequences of consciousness rather than constituents: attention, working memory, and thepreparation of a verbal report all follow conscious perception and are recorded alongside it.preparation of a verbal report all follow conscious perception and are recorded alongside it. ## Methods## Methodslines 86–100 → 86–10034 unchanged lines not shown
with a system's intrinsic, maximally irreducible cause-effect structure, quantified as Φ, andwith a system's intrinsic, maximally irreducible cause-effect structure, quantified as Φ, andlocates the substrate in a posterior "hot zone" of parietal, temporal, and occipital cortex ratherlocates the substrate in a posterior "hot zone" of parietal, temporal, and occipital cortex ratherthan in prefrontal areas.[^koch2016] It makes the strong claim that a system's architecture, not itsthan in prefrontal areas.[^koch2016] It makes the strong claim that a system's architecture, not itsinput-output behaviour, determines whether it is conscious — the reason it deniesinput-output behaviour, determines whether it is conscious, which is why it denies[[substrate-independence]].[[substrate-independence]]. **Recurrent processing theory** holds that local recurrent activity in sensory cortex suffices for**Recurrent processing theory** holds that local recurrent activity in sensory cortex suffices forexperience even without global broadcast. **Higher-order theories** hold that a first-orderexperience even without global broadcast. **Higher-order theories** hold that a first-orderrepresentation becomes conscious only when represented by a further state, typically in prefrontalrepresentation becomes conscious only when represented by a further state, typically in prefrontalcortex. **Attention schema theory** treats consciousness as the brain's simplified model of its owncortex. **Attention schema theory** treats consciousness as the brain's simplified model of its ownattention. These are not merely verbal variants: they disagree about where to look and about whichattention. The differences are substantive, not verbal: the theories disagree about where to lookpatients and which systems are conscious.and about which patients and which systems are conscious. ## The adversarial collaboration## The adversarial collaboration lines 109–143 → 109–1438 unchanged lines not shown
posterior emphasis; but the sustained long-range synchronization that integrated information theoryposterior emphasis; but the sustained long-range synchronization that integrated information theorypredicted was not observed. Conversely, prefrontal cortex carried some content information, but thepredicted was not observed. Conversely, prefrontal cortex carried some content information, but theignition-like response global workspace theory predicted at the end of a stimulus was not found.ignition-like response global workspace theory predicted at the end of a stimulus was not found.Both camps have argued that the tested predictions were not core commitments of their theories — aBoth camps have argued that the tested predictions were not core commitments of their theories. Theresponse the collaboration's design was intended to forestall, and which illustrates how hard it iscollaboration's design was intended to forestall exactly that response, and its appearanceto falsify a theory of consciousness.illustrates how hard it is to falsify a theory of consciousness. > [!debate] A bet, settled> [!debate] A bet, settled> In 1998 Christof Koch wagered David Chalmers a case of wine that a clear neural correlate of> In 1998 Christof Koch wagered David Chalmers a case of wine that a clear neural correlate of> consciousness would be identified within 25 years. Koch conceded in 2023. The concession was> consciousness would be identified within 25 years. Koch conceded in 2023. The concession was> collegial and the science had advanced considerably; the point is that a leading experimentalist> collegial and the science had advanced considerably, but a leading experimentalist had judged the> judged the specific target unmet.> specific target unmet. ## Measures without report## Measures without report The clinically important products of the field do not depend on settling the theory. TheThe clinically important products of the field do not depend on settling the theory. Theperturbational complexity index uses transcranial magnetic stimulation — one of the techniquesperturbational complexity index uses transcranial magnetic stimulation, one of the techniquescovered under [[non-invasive-neuromodulation]] — to perturb cortex and measures the spatiotemporalcovered under [[non-invasive-neuromodulation]], to perturb cortex and measures the spatiotemporalcomplexity of the electroencephalographic response. It separates wakefulness and dreaming fromcomplexity of the electroencephalographic response. It separates wakefulness and dreaming fromanaesthesia, deep sleep, and vegetative states in ways that behavioural examinationanaesthesia, deep sleep, and vegetative states in ways that behavioural examinationmisses.[^casali2013] Measures of signal diversity in the same family rise rather than fall undermisses.[^casali2013] Measures of signal diversity in the same family rise rather than fall underpsilocybin and LSD, which is why the drugs studied for [[psychedelic-therapy]] also serve the fieldpsilocybin and LSD, which is why the drugs studied for [[psychedelic-therapy]] also serve the fieldas a way of perturbing conscious state rather than only of suppressing it. Task-based imaging canas a way of perturbing conscious state rather than only of suppressing it. Task-based imaging candetect covert awareness: some behaviourally unresponsivedetect covert awareness: some behaviourally unresponsive patients modulate their brain activity onpatients modulate their brain activity on command, for example by imagining playing tennis. A largecommand, for example by imagining playing tennis. A large multi-centre study published in 2024 foundmulti-centre study published in 2024 found this cognitive-motor dissociation in roughly one in fourthis cognitive-motor dissociation in roughly one in four patients who showed no observable responsepatients who showed no observable response at the bedside.[^bodien2024] For those patients aat the bedside.[^bodien2024] For those patients a [[brain-computer-interface]] is the only available[[brain-computer-interface]] is the only available communication channel, and central thalamiccommunication channel, and central thalamic [[deep-brain-stimulation]] has been investigated as a[[deep-brain-stimulation]] has been investigated as a way to raise arousal.way to raise arousal. These methods are correlational and calibrated against people who can confirm their experience,These methods are correlational and calibrated against people who can confirm their experience,which limits how far they extend to systems very unlike humans — the problem that dominateswhich limits how far they extend to systems very unlike humans, the problem that dominates[[machine-consciousness]].[[machine-consciousness]]. ## Implications for artificial systems## Implications for artificial systemslines 148–155 → 148–1554 unchanged lines not shown
holds that a digital computer simulating a conscious system would have negligible Φ, so behaviour isholds that a digital computer simulating a conscious system would have negligible Φ, so behaviour isirrelevant. Higher-order and attention-schema theories fall in between.irrelevant. Higher-order and attention-schema theories fall in between. This is why current work on assessing artificial systems takes an indicator-property approach —This is why current work on assessing artificial systems takes an indicator-property approachextracting the computational features that each theory says matter and checking which are present —(extracting the computational features that each theory says matter and checking which are present)rather than applying a behavioural test. It is also why progress on the NCC bears directly onrather than applying a behavioural test. It is also why progress on the NCC bears directly on[[mind-uploading]] and [[whole-brain-emulation]]: an emulation's moral and personal status depends[[mind-uploading]] and [[whole-brain-emulation]]: an emulation's moral and personal status dependson a question the NCC programme was explicitly designed to bracket, as does the status of anythingon a question the NCC programme was explicitly designed to bracket, as does the status of anythinglines 166–173 → 166–17310 unchanged lines not shown
either; the field's stimuli are almost entirely visual, so the correlates found may be correlates ofeither; the field's stimuli are almost entirely visual, so the correlates found may be correlates ofseeing rather than of consciousness; and the tools remain coarse, since evenseeing rather than of consciousness; and the tools remain coarse, since even[[connectomics]] and dense recording sample far less than the relevant circuitry. Tension over[[connectomics]] and dense recording sample far less than the relevant circuitry. Tension overwhether integrated information theory is testable at all — expressed in a 2023 open letter from awhether integrated information theory is testable at all, expressed in a 2023 open letter from alarge group of researchers — reflects a deeper unresolved question about what would count aslarge group of researchers, reflects a deeper unresolved question about what would count asevidence.evidence. ## See also## See alsoremoved, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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