Theories of Consciousness - List
bzichett
Posted by u/Braincyclopedia 3 days ago
Hey guys, I made a list of all the theories of consciousness I could find. Made a short description of each one. Would appreciate feedback if I missed anything or if my description is inaccurate. Also, let's pointlessly argue about which one is the most correct one. Looking forward to your inputs.
Ps. In each section, the first theory or two is most established one in the field (take into account that all the theories are untestable, thus what makes a theory more popular is its applicability to AI, and not how accurate it represents consciousness in the brain). Also, I didn't include theories that were refuted, such as the OrchOr theory.
Models:
1. **Synchrony theory**
(Singer, Engel): Neurons that fire in the same phase (rhythm) at the gamma range (above 30 action potentials per sec) send together stimulus information to consciousness. The purpose of consciousness is binding features into objects (eg binding the shape of a box with its color, sound, location. etc). The theory is now considered incomplete, and is the basis of most theories below.
System-Integration models: Consciousness emerges when information from different sources is processed in a closed network.
2. **Integrated information theory** (Tononi): Subjective experience is a side effect of a large scale simultaneous processing of incoming information in a closed network/ensemble of neurons. The information forms conscious shapes (quale) in the conscious space (qualia space) by integrating together all the possible dimensions of informations (q-arrows). The posterior parietal cortex (attention center) is a hot-zone for eliciting consciousness due to receiving more incoming information than other regions (but to a lesser degree consciousness occurs also in other brain parts). The model was formed by analyzing the properties of subjective experience (and not by examining the brain).
3. **Supramodular Interaction theory of Consciousness** (Morsella): Conflict resolution of movement is the only behavior that cannot occur subconsciously (ie it is encapsulated). In order to determine which body movement to execute, our brain enables cross talk between many different regions. The purpose of consciousness is to delay gratification (exert volitional control over the muscle system).
4. **Postdiction model of Consciousness** (Eagleman, Michel & Doerig): Sensory stimuli arrives to consciousness at different times, but we experience it simultaneously. The brain waits 80 ms (Eagleman) or 100-400 ms (Michel & Doerig) before integrating all the sensory stimuli into a single united experience (hence post diction - the opposite of prediction). The model is driven by several illusions (eg the flash-lag illusion). The purpose of consciousness is integration of sensory information into objects.
Attention based models: Attention has the ability to enhance/reduce conscious experience. These theories postulate that consciousness doesn’t occur at the local level (eg cortical column), but instead it occurs by implementing the large attentional network.
5. **Global neuronal workspace theory** (Dehaene, Changeux): Consciousness occurs due to the attention system (dorsal prefrontal and then parietal cortices) synching together the firing rate of neurons (phase) from distant brain areas. This results with all the synched neurons suddenly firing at a high rate (global ignition). This occurs due to a switch in the neurons from using AMPA receptors to NMDA receptors. The purpose of consciousness is to provide brain regions access to other active brain regions (eg saying a name elicits an image of a face). Consciousness occurs 300 ms after stimulus onset (model tries to explain the p300 EEG signal).
6. **Attention Schema theory** (Graziano): The model suggests similarity between the usage of the body schema (awareness for the position of body parts) for motor control, and the usage of consciousness (schemas of sensory stimuli) in the control of attention shifts. The function of consciousness is to serve as the 1st stage in attention control. That is to guide the spotlight of attention to focus on a region/object in space.
7. **Attended intermediate-level representation (AIR)** (Prinz): Attention is synonymous with consciousness. Based on hypothesis by Jackendoff, which argues that only intermediate level representations can reach awareness (eg when listening to a person speaking we are not aware of the acoustics because it is too simple, and we are not aware of the grammatical rules because they are too complex). The AIR theory argues that the attention system can only modify intermediate level representations. This modification elicit the representation into consciousness. The purpose of the modification is that the representation will become accessible to working memory.
5. **Corollary Discharge of Attention Movement (CODAM)** (Taylor): After we shift our attention spotlight, the working memory system retains a copy of this movement (corollary discharge). Then, after the attention system confirms the new location, it is sent to the working memory system, and the corollary discharge and new location cancel each other out. Consciouses rises by the maintenance in working memory during this wait period. Consciousness is a side-effect of our ability to shift attention in space. The model explains the attentional blink effect, and is based on neglect patients.
Memory/Learning based models:
6. **Multiple Draft Model of Consciousness** (Dennet): Consciousness is a preliminary phase to memory encoding. If it was not encoded into memory, it will be erased (ie it is a draft). The hypothesis is driven by the conclusion that consciousness is purposeless as there is no point of devoting costly energy to perform to yourself (Cartesian theater). The purpose of consciousness could thus be telling yourself your own story, which is done through reliving memories. The model is based on the phi phenomenon and the cutaneous rabbit illusion.
7. **Theory of Neural Group Selection**, TNGS (Edelman): A subjective experience of a stimulus emerges when information about it travels in a loop between neurons in the thalamus and their corresponding counterparts in the neocortex (together forming a neural group). The combination of simultaneously active neural groups (dynamic core) determines the content of consciousness, and this combination is constantly changing due to integration or differentiation. Consciousness originally emerged for reliving memories. Then, due to accidental integration of a neural group responsible for a memory with a a neural group responsible for perceiving a current stimulus, we became conscious of the present (ie recalling a memory that just occurred, a remembered present).
8. **Polychronization theory of consciousness** (Izhikevich): Continuation of the TNGS model. A computational model that argues that neurons self organize into groups based on their firing timing (instead of firing rate), with each group representing a different element/object in the scene. They found that there are more groups than objects in the scene, and argue that the additional objects are related to the memory of the object. Consciousness occurs in the redundant groups by allocating attention to the memories of objects.
Perception-based models: Consciousness emerges at the local level (eg cortical column, cortico-thalamic circuit). These models are based on studies of sensory perception.
9. **Recurrent processing theory** (Lamme): Consciousness occurs due to the travel of information in a loop in the brain between neighboring higher order and lower order sensory cortices (eg V2 and V4). The purpose of consciousness is perceptual organization. Consciousness occurs 100-200 ms after stimulus onset (model tries to explain the VAN/N2 EEG signal). (A similar model was developed by Crick and Koch.)
10. **Predictive coding theory of consciousness** (Hohwy): We are not conscious of stimuli, instead our brain constructs a simulated reality that is based on the expected stimuli (which explains illusions). Consciousness of sensory stimuli occurs because the brain tries to guess the current stimulus based on the previous stimulus, for the purpose of minimizing surprises. The purpose of consciousness is to form cause-effect associations between sensory representations.
11. **Resonance Theory (ART)** (Grossberg): Conscious experience emerges when information of sensory boundaries (center-surround) is traveling in a loop (ie resonating) in the neurons of a cortical column (including it thalamic counterpart) via a fast firing rate (gamma range), which enables learning (synaptic plasticity). The cortical column constantly compares the input from lower brain areas to feedback from higher areas, and as long as they match (and enhanced by attention) consciousness remains. The function of the thalamus is to detect mismatches between input and feedback, and to block learning (and consciousness) from happening in the neocortex by slowing cortical firing, and by activating the acetylcholine orienting system (Basal forebrain). The model predicts that parieto-frontal (visual where pathway) and entorhinal-hippocampal (long-term memory encoding) circuits are unconscious due to the lack of feature detection (center-surround processing). Based on this model, the purpose of consciousness is to maintain plasticity in the brain (ie to enable learning). The model is based on recording of neural activity at different cortical layers, and is derived from the organization of the visual, auditory, and emotion brain network.
12. **Disunity theory of consciousness** (Zeki): There are many localized subjective experiences, that are united into larger and larger units of subjective experiences. Consciousness is an outcome of local information analysis. The model is driven by the parallel and hierarchical processing structure of visual information in the brain, and by several illusions.
13. **Temporo-spatial theory of consciousness** (Northoff): The model is driven by the priming effect (eg watching faces biases face-vase illusion towards faces). A stimulus reaches consciousness if neighboring neurons in that network already behaved with a similar firing pattern before the stimulus perception began. Only when the signal involves enough neurons (ie expands the signal in a spatial and temporal directions), a signal will reach consciousness. The author equates consciousness to a surfer (stimulus), who rides on waves (previous brain activity) which lift and move the surfer (elicit the stimulus to consciousness).
Self-based theories of consciousness: Consciousness first emerged to be aware to our bodies, and was later extended to other senses. These models originate from met zinger’s hypothesis that we see the world through the self, with the self remaining transparent (phenomenal self model) and through Damasio’s assertion that emotions begin with perception of the body (porto-self).
14. **The Free Energy theory of consciousness** (Friston, Solms): This model is derived from the predictive coding theory. Affect is the original form of consciousness as it is the only aspect of consciousness that occurs sub-cortically (in the midbrain-reticular activating system). Affect, and in particular surprise, prompts a desire to return to balance (to dissipate free energy), by implementing active inference. In active inference, the brain constructs a prediction for the perceptual experience when performing an action, and then comparing the prediction to the results (with preference for prediction with minimal error/free energy). Throughout evolution, the consciousness associated with affect was extended to the sensory predictions. The purpose of consciousness is to return to homeostasis (avoid surprises).
15. **Embodied theory of consciousness** (Tallon-Boudry)— Sensory awareness to the world, emotions, and self-consciousness are derived from consciousness to one’s body. The model is based on a relationship between neural firing (eg EEG auditory components N1 and visual component P1), and 1st person perceptual perspective, with one’s heartbeat. Neural synchrony occurs because of synchronization with the heart beat. Consciousness first emerged to record bodily functions, and only later this was extended to include awareness to exterior stimuli.
16. **Projective Consciousness Model** (PCM) of consciousness (Williford, Rudrauf, Friston): Build on the free energy theory, and Metzinger’s phenomenal self model. Association with the 1st person point of view and prediction of stimuli in reference to the 1st person point of view (projective geometry) serve as a filter against integration of unnecessary information.
17. **Integrated World Modeling Theory (IWNT) of consciousness** (Safron): Combination of integrated information and free energy models. Association with the self and prediction of stimuli in reference to the self serve as a filter against integration of unnecessary information. Prediction in the neocortex occurs through excitation of independent waves of synchronized neurons (self organizing harmonic modes), which process the information and elicit it to consciousness. Harmonic modes with a slow neural firing (8-12 spikes per sec; alpha range) are responsible for phenomenal consciousness, while harmonic modes with even slower firing (4-8 spikes per sec; theta range) are responsible for access consciousness.
18. **Multi-level feedback model** (Haikonen): There are 4 requirements to consciousness: 1. Integrating location of perceived objects with the location of the self. 2. A complex feedback mechanism (introspection of mental content). 3. Integration of sensory information from different sources. 4. Perception of the self/body (eg somatosensory cortex). The model was constructed to simulate sentience in artificial intelligence.
19. **Retinoid model of consciousness** (Traube): Determination of distances to objects (ie determining your location in space) is the core of our consciousness (self locus). Once I occupy a location in conscious space, we cannot consciously perceive another object at that location. The self location is interconnected with a network of self identity (I! token). This network is connected to all our sensory perceptions, beliefs, memory recollections, and needs and motives. This is a computational model that is based on analysis of the visual system.
Higher Order theories (HOT): In addition to the brain representing the stimulus it also requires a thought or intention, which is localized to the lateral prefrontal cortex (with some including also the medial prefrontal and anterior insula cortices). In these models, meta-cognition appeared in evolution prior to consciousness, and provided the framework for its emergence. These models are based on the blindsight disorder and TMS research.
20. **Higher order thought theory** , HOTT (Rosenthal): A non-conscious thought/desire to be aware (executive control) enables a non-conscious representation in the posterior (sensory) cerebrum to rise into consciousness. The thought can also reach consciousness without a stimulus. This theory argues that consciousness has no function (or its contribution to survival is minimal).
21. **Higher order representation of representation**, HOROR (Brown, LeDoux): A copy of the perceptual representation from the posterior (sensory) cerebrum or from subocortical regions (eg amygdala) is sent to the frontal lobe, and there it is combined with an intention/thought. This combination elicits the stimulus into consciousness. The model argues that consciousness first emerged for consciously perceiving emotions.
22. **Perceptual reality monitoring theory of consciousness** (Lau): Executive control (frontal lobe) has an index for all the representations in the posterior (sensory) cerebrum, and determines if it is fit (reliable) to reach consciousness. The representations in the posterior cerebrum are the ones to reach consciousness (but they are dependent on prior frontal activation). The purpose of consciousness is relevance assessment.
23. **Radical plasticity thesis** (Cleermans): We are born without consciousness, and every time (especially as babies) we learn a rule (cause-effect) it is registered as a higher order representation that is accessible to consciousness. The learned cause-effect rules strengthen the quality of the subjective experience. If an experience is over learned (automatic), then it weakens the subjective experience. The purpose of consciousness is to learn rules (stimulus+action=consequence associations).
24. **Self representational higher order theory** (Kriegel, Van Gulick, Gennaro): The posterior (sensory) cerebrum forms weak/partial conscious representations. Once a posterior representation is combined with a thought/intention, the conscious experience becomes stronger and more distinct. Kriegel localized consciousness to the anterior cingulate cortex.
Content-based theories of consciousness: Models describing the content, instead of the existence, of consciousness:
25. **The laws of qualia** (Ramachandran, Hirstein): qualia are: 1) irrevocable, in the sense that subjects cannot deny qualia; 2) utilised flexibly for future planning, unlike those non‐conscious percepts that can only give riseto a reflex; 3) stored in short‐term memory; and 4) closely linked with attention.
26. **Entropy theory of consciousness** (Carhart-Harris): Describes the evolution of consciousness as increase in regulation (reduction in entropy) from infant or animal to adult human. Argues that dreams, psychosis, and psychedelics states are instances of returning to a more evolutionary primitive conscious state. The model is described via a Freudian psychoanalytical approach.
27. **Sensory-motor theory of consciousness** (O'Regan, Noë): Our ability and manner of interacting with objects (or modify their neural representations) determines their conscious quality. ie., we don't interact with our blood glucose level, and thus are not aware of it. We experience seeing a straight line because our eyes follow it from top to bottom in a straight manner, or we experience softness because of the degree of resistance we sense from an object while pressing on it. The model explains phenomena the change blindness, inattention blindness, and rubber hand illusion.
Electromagnetic models of consciousness:
28. **Cemi-field theory of consciousness** (McFadden): Similar to integrated information theory, but argues that instead of integrating information at synapses, information is also integrated via the electromagnetic waves of neurons (the waves detected by EEG). When enough neurons fire in synchrony, they form an electromagnetic wave that is both stronger than the noise produced by the remaining neurons, while also simultaneously integrates all the collected information in a single united fashion (ie the smell, name, face, and sound of a person are integrated into the same wave). This unified wave can trigger neurons close to threshold to fire (global ignition). This model explains neural synchrony, and the effect of TMS on consciousness.
29. **Operational space-time architectonic theory of consciousness** (Fingelkurts): Like the cemi-field theory, it argues for consciousness to be the result of electro-magnetic information processing, which further influences activity in neurons. However, this model describes a hierarchy of nested brain regions. That is, each group of regions combine their electromagnetic fields to affect larger regions, which in turn combine the electromagnetic fields to affect even larger regions, and so forth. This model is derived from recordings the brain activity in comatose patients.
Location-based models of consciousness:
30 **Thalamo-cortical models of consciousness** (Ward, Llinás, Min, Aru): Developed from Edelman’s dynamic core theory.
-Aru argues that the cortico-cortical connections are responsible for the content of consciousness and the thalamo-cortical connections to the level of consciousness.
-Ward argues that consciousness emerges in the dendrites of thalamic neurons. Ward also argues that the inhibition of thalamic neurons by the reticular thalamic nucleus synchronizes the neural activity of cortical neurons, which determines the content of consciousness.
-Min’s model is similar to Ward, but also argues that interconnections in the reticular thalamic nucleus form the unitary conscious experience.
-Llinás argues that the binding of all the elements into a united conscious experience occurs because of interaction between the non-specific thalamic nuclei (the ones receiving and sending axons to the neocortex) with the specific thalamic nuclei (the nuclei receiving sensory input from the eye, ear, skin etc and send it to the neocortex).
-This model is consistent with most of the models presented above, with each model arguing for a different combination of active thalamo-cortical connections.
31. **Anterior insula model of consciousness** (Craig, Huang): The anterior insula integrates information from the body regarding the self (eg proprioception, balance, touch, pain, visceral sensation). fMRI studies showed correlated activity here with losing consciousness in anesthesia, visual perception, and regaining consciousness in comatose patients. It should be noted that bilateral damage to the insula doesn’t eliminate consciousness.
32. **Claustrum model of consciousness** (Crick, Koch): Stimulation of white matter beneath the claustrum temporarily eliminates consciousness. The claustrum is interconnected with all parts of the neocortex, which could suggest a role in uniting all the processed information into a single conscious experience. The drug Salvia elicits hallucinations by modulating claustral neurons. It should be noted that bilateral damage to the claustrum doesn’t eliminate consciousness. Recently, the claustrum of mice were also ascribed with putting the neocortex in a down/sleep state by simultaneously exciting inhibitory neurons across the neocortex (Narikiyo).
33. **Mesencephalic model of consciousness** (Merker): Argues that consciousness rises in midbrain-hypothalamus, with a focus on the superior colliculus (due to its massive convergence of sensory and motor inputs). The neocortex can then amplify and modify this conscious experience. It suggests that low level consciousness exist in all vertebrates. The function of consciousness is to exert volitional control over the muscle system (delay gratification). This model is based on studies of children born without a neocortex and decorticated animals. The model was extended by Barron and Colin to argue that insects (and invertebrates) have basic consciousness.
Global Consciousness and Extended Cognition:
Theories that argue that consciousness can extend beyond the limits of the individual brain/body.
34. **The global consciousness hypothesis** (Dean Radin): Presented findings that in a double slit experiment, meditation/allocation of attention to the device can form (extremely small, yet consistent) interference in the intensity of the light. Argues that this is evidence that consciousness extends beyond the individual brain/body, and could even be prevalent throughout the universe (panpsychism?).
35. **Shared consciousness hypothesis** (Valencia and Froese): Showed that people synchronize brain activity (using EEG) when cooperating, and that this synchronization is lost in disorders of consciousness (eg schizophrenia, autism). Argues that, as neural synchrony correlates with consciousness in the individual brain, it can also elicits shared conscious experience between neighboring cooperating brains (this model is based on the extended cognition hypotheses of Clark, and of Kirchhoff).