1. Introduction: The Hard Problem of Consciousness

Knowing the brain's structure (see R-08 and R-13). Measuring neuronal activity. Mapping circuits. Yet one question persists: Why is this activity accompanied by lived experience? Why do neurons processing the image of red produce not only behavior but also feel red?

David Chalmers, philosopher and cognitive scientist, named this problem the «hard problem» in 1995. He distinguishes two categories of questions:

• «Easy» problems: Explaining cognitive functions (memory, attention, stimulus discrimination). They are «easy» because they can be solved by identifying computational or neural mechanisms.
• «Hard» problem: Explaining why and how these physical processes are accompanied by subjective experience. Why is there «something it is like»?

This document surveys the main scientific theories of consciousness, distinguishing what is established from what is debated.

2. Global Workspace Theory (GWT)

Origin: Bernard Baars (cognitive scientist, USA), 1988. Redesigned by Stanislas Dehaene and collaborators (cognitive neuroscience, France).

Principle: Consciousness functions like a theater. Unconscious specialists (neural processes) compete for access to a limited stage (the global workspace). Information that gains access is «broadcast» throughout the brain and becomes conscious.

Neural mechanism: Activation propagates through a fronto-parietal network, with nonlinear ignition at high latency (~300 ms). Observed neural signature: P300 component of event-related potentials and high-frequency gamma synchronization.

Publications: Baars, B. J. (1997). In the Theatre of Consciousness. Dehaene, S. et al. (2014). Conscious Processing and the Global Neuronal Workspace Hypothesis (Neuron).

Validation: Numerous experimental studies, particularly on unconscious vs. conscious vision. Testable predictions verified in hundreds of works.

Limitations: Explains access to information, but not why this accessibility creates subjective experience. Some critics note the model localizes consciousness too much in frontal regions.

Status: Dominant theory in cognitive neuroscience. Experimentally validated.

3. Integrated Information Theory (IIT)

Origin: Giulio Tononi (psychiatrist, University of Wisconsin-Madison, USA), 2004. Developed with Christof Koch, Melanie Boly, and others.

Principle: Consciousness corresponds to the amount of integrated information in a system. The more integrated information a system generates (measured by Φ, phi), the more conscious it is. The system must satisfy five axioms: existence, composition, information, integration, exclusion.

Mathematical formalization: Φ is calculated as the minimum between integrated causal information (φc) and integrated effecter information (φe). In principle, can be applied to any physical substrate (brain, machine) (see B-07).

Applications: Assessing consciousness in coma patients, under anesthesia. Clinical tests (Perturbation Complexity Index — PCI).

Publications: Tononi, G. et al. (2016). Integrated Information Theory 3.0. Albantakis, L. et al. (2023). Integrated Information Theory 4.0 (arXiv). Ellia, F. et al. (2021). Consciousness and Complexity (Neural Computation).

Scientific validity: Rigorous formal framework, numerous peer-reviewed publications. Empirically testable (PCI).

Criticisms:

1. Calculation of Φ is extremely costly in computational resources, practically impossible for large real systems.
2. Certain predictions (e.g., consciousness in simple systems) seem counterintuitive (implicit panpsychism).
3. Conflict with GWT on the role of prefrontal cortex.

Status: Major theory, peer-reviewed. Open debate with GWT.

4. Orchestrated Objective Reduction (Orch OR — Penrose & Hameroff)

Origin: Roger Penrose (mathematician, physicist, Oxford, UK) and Stuart Hameroff (anesthesiologist, University of Arizona, USA), 1990s.

Principle: Consciousness arises from quantum computations in neuronal microtubules. Each computation ends with objective reduction (wave function collapse) linked to spacetime geometry. Non-computational, explains free will.

Arguments in favor:

• Microtubules are cellular structures candidates for hosting quantum states.
• Studies show anesthetics act on microtubules.
• Quantum coherence has been reported in tubulin fragments.

Publications: Penrose, R. & Hameroff, S. (2014). Consciousness in the universe: A review of the 'Orch OR' theory (Physics of Life Reviews). Craddock, T.J. et al. (2015). Anesthetics Act in Quantum Channels in Brain Microtubules (Current Topics in Medicinal Chemistry).

Dominant criticisms (2023–2025):

1. Rapid decoherence: The brain is «warm, wet and noisy». Quantum states decohere in ~10⁻¹³ seconds, too fast for cognitive processing (~10⁻² seconds).
2. Lack of direct evidence: No experimental demonstration of quantum coherence at the required scale in a living brain.
3. Contested Gödelian arguments: Penrose's argument on non-computability based on Gödel's theorem is judged speculative and not supported by empirical data.

Current consensus: Intriguing theory, minority. Majority of neuroscientists and physicists consider Orch OR as unverified or even unverifiable.

Status: Speculative hypothesis. Little supported by dominant scientific community.

5. Other Notable Approaches

Classical emergence: Consciousness emerges naturally from the complexity of neural networks. «Default» position of many neuroscientists. Problem: Does not answer the «hard problem», sidesteps the question of subjective experience.

Panpsychism (variants): Consciousness is a fundamental property of matter (see B-07), like mass or charge. Complex systems integrate these elementary consciousnesses. Related to IIT. Criticism: How do micro-consciousnesses aggregate into macro-consciousness?

Eliminative materialism (Dennett, etc.): Consciousness as we conceive it is an illusion. There are only computational processes. Criticism: Denies subjective experience, philosophically unsatisfying.

Hybrid approaches (Consciousness Consortium, 2023): Researchers propose several theories are complementary, each explaining a facet of the phenomenon. Ex: GWT for access, IIT for phenomenal quality.

Publications: Consortium, C. et al. (2023). Mapping the Landscape of Consciousness Theories (Trends in Cognitive Sciences).

6. Comparative Synthesis

7. What Science Does Not Know Yet

Despite progress, several questions remain open:

1. The substrate: Is consciousness limited to biological systems? Can it exist in silicon, as IIT theoretically suggests? (see B-07)
2. Measurement: How to objectively measure consciousness in a non-responsive patient, an animal, a machine?
3. The mechanism: Which precise mechanism(s) generate subjective experience? None is confirmed.
4. Evolution: Why did consciousness appear in evolution? Adaptive function or epiphenomenon?

8. Open Questions

1. Which theory is right? GWT, IIT, or another? Or are several simultaneously true at different levels?
2. Is consciousness universal? A fundamental property of the cosmos (IIT, panpsychism) or emergent from life?
3. Can silicon be conscious? According to IIT, yes, if Φ is high enough. According to classical neuroscience, probably not.
4. How to decide? What future experiments could validate or refute each theory?

9. Sources and References

Hard problem (Chalmers):

• Chalmers, D. «Facing Up to the Problem of Consciousness.» Journal of Consciousness Studies 2(3):200-19 (1995)

Global Workspace Theory (Baars, Dehaene):

• Baars, B.J. In the Theatre of Consciousness (1997)
• Dehaene, S. et al. «Conscious Processing and the Global Neuronal Workspace Hypothesis.» Neuron 89(6):1130-49 (2014)

Integrated Information Theory (Tononi):

• Tononi, G. et al. «Integrated Information Theory 3.0.» (2016)
• Albantakis, L. et al. «Integrated Information Theory 4.0.» arXiv (2023)
• Ellia, F. et al. «Consciousness and Complexity.» Neural Computation (2021)

Orch OR (Penrose & Hameroff):

• Penrose, R. & Hameroff, S. «Consciousness in the universe: A review of the 'Orch OR' theory.» Physics of Life Reviews 11(1):39-78 (2014)
• Craddock, T.J. et al. «Anesthetics Act in Quantum Channels in Brain Microtubules.» Current Topics in Medicinal Chemistry (2015)

Hybrid approaches:

• Consortium, C. et al. «Mapping the Landscape of Consciousness Theories.» Trends in Cognitive Sciences (2023)