Which characteristics of neural activity patterns underlie conscious experience? Which specific characteristics of neural activity patterns are unique for the cortex and neocortex as the presumed "seat of consciousness" and can only be observed there? Activity patterns having these characteristics would be candidates for "neural correlates of consciousness" and so to speak are responsible for or underlie conscious experience. Furthermore, it would be "explained" why neural activity in other parts of the brain don't (directly) affect conscious experience.

I especially wonder on which level of description and observation and on which spatio-temporal scales these activity patterns (and their characteristics) would be found. It could be


on a subneuronal level
on the level of single neurons
on the level of small groups of neurons, e.g. cortical columns
on a voxel level
on a ROI level


With "characteristic" I mean something like


"reentrant signaling states in some specific forms" source 
some forms of synchrony, resonance, or general structuredness


but it would have to be defined in a specific way such that it is unique and characteristic for the cortex and would not be found in other areas of the brain.

Are there at least some preliminary and not too abstract answers around? Known neural-based explanations of consciousness I am aware of (and that are summarized for example here or here) don't give explicit answers to my question but often remain rather abstract and often don't explicitly argue that the processes they describe only do and can occur in the cortex - let alone what is "really characteristic" for them as spatio-temporal processes.

If experts here would say that this question in this form is unanswerable or otherwise ill-posed it would be great to know. Thanks a lot in advance.
As discussed previously in this thread, information (specifically, information that exists in the neural circuits), is probably the physical quantity that correlates perfectly with consciousness and, I would like to add, qualia. This is because information can have the same complexity, dynamicity, and content as consciousness and qualia do.

Now, what is the specific neural activity that is or contains information among neural circuits. When a neural circuit is functioning, there are many activities going on in and around that neural circuit: signal processing activities, metabolic activities, structural maintaining (of membranes, organelles, cytoskeletons, etc.) activities, circuit modifying (of synapses, dendrites, axons) activities, changes in supplying blood circulation, oxygen, and other blood constituents, changes in its physical constitutions (temperature, mass, entropy, etc.), etc. But the only activity that has the complexity, dynamicity, content containing capacity as the information does is the signal processing activity. Moreover, it’s the only activity that can communicate locally and extensively with its counterparts in other neural circuits. 

So, from current evidence, it is to be concluded that neural processing activities, with its correct spatio-temproal and other profiles, underly the brain’s information-related functions, including consciousness and qualia. Clinical and experimental evidence strongly supports this concept. Anything (such as a certain disease or drug, brain electrical stimulation, or transcranial magnetic stimulation) that mainly affects neural transmissions and significantly interferes with the signal processing activities but does not significantly interfere with other activities significantly interferes the brain’s information-related functions, such as consciousness and qualia. Moreover, the change that occurs in the signal processing activity and that in the brain’s information-related functions (such as consciousness and qualia) occur simultaneously! For more detailed discussion about this matter, please read ref 1 and ref 2.

Now, why do some signal processing activities have qualia or consciousness, why some don’t? There are different explanations for this from some existing theories. The Integrated Information Theory [IIT][3-6] asserts that a conscious experience is a maximally irreducible conceptual structure (MICS), which corresponds to a local maximum of integrated conceptual information (or a local maximum of Φ or Φmax) and provides mathematical formulations to calculate Φ. So, according to this theory, for any signal processing activity to be conscious, it must be complex in a certain way enough for its Φ to reach Φmax there. For example, from its calculations, there is no consciousness during sleeps, generalized seizures, or in the cerebellum – which are all true – even if, in the last two examples, active and complex processing activities are going on. It also calculates that processing activities in computers or robots, no matter how complex, can’t become conscious because they function from fixed software, which isn’t really complex in the IIT way.

According to The Basic Theory of the Mind [1,2], not all signal processing activities can be qualia or consciousness. To be qualia or consciousness, the signals from signal processing activities not only must be accessible by the consciousness neural process but also must be in some specific forms that mean qualia or mean consciousness in the nervous system language, that is, the signals must be in some specific forms that, when processed by neural circuits in the nervous system, will be interpreted to be qualia or consciousness. The theory called this kind of signals “Special signaling pattern” and “Special signaling state”. This is like why all words, except the word is this specific form “consciousness”, do not mean consciousness in English. However, although the theory gives some preliminary characteristics of these special signaling forms, it admits that the complete characteristics of these special signaling forms are not known at present but predicts that these specific forms exist and can be found by investigations.

According to the Adaptive Resonance Theory (ART)[7,8], “all conscious states are resonant states, but not all resonant states are conscious states”. The resonance states must be accessible to consciousness to be conscious. “Indeed, some resonant states, such as the storage of a sequence of events in working memory before rehearsal occurs, or the entorhinal–hippocampal resonances that may dynamically stabilize the learning of entorhinal grid cells and hippocampal place cells, are not accessible to consciousness.” So, they are not conscious. Also, the resonance states must be in some forms to be conscious – they must involve the processes of learning, expectation, and attention. For example, “What sort of resonance supports a conscious percept of surface brightness or color? As noted above, I have predicted that such a consciously visible percept is supported by a surface shroud resonance between visual cortical areas and the parietal cortex that is predicted to play a role in learning invariant object categories (Section17).This prediction illustrates how ART clarifies mechanistic relationships between the CLEARS processes of consciousness, learning, expectation, attention, resonance, and synchrony.”

I think these are some preliminary answers that I can gather from some existing theories. They are certainly not the widely-accepted, standard answers. And there are other theories that I’m not familiar with, such as ref 9-11, which may have the answers you’re looking for. So, if you are intereseted and have time, please examine them.

References:


Ukachoke C. Chapter 5 – Theorem IV: A Quale is a Special Kind of Signaling Pattern In: The Basic Theory of the Mind. 1st ed. Bangkok, Thailand; Charansanitwong Printing Co. 2018.
Ukachoke C. Chapter 6 – Theorem V: Consciousness is a Special Kind of Reentrant Signaling State In: The Basic Theory of the Mind. 1st ed. Bangkok, Thailand; Charansanitwong Printing Co. 2018.
Tononi G. An information integration theory of consciousness. BMC Neurosci 2004,5:42. DOI: 10.1186/1471-2202-5-42. 
Tononi G. Integrated information theory of consciousness: An updated account. Arch Ital Biol. 2012 Jun-Sep;150(2-3):56-90. DOI: 10.4449/aib.v149i5.1388. 
Oizumi M, Albantakis L, Tononi G. From the phenomenology to the mechanisms of consciousness: Integrated Information Theory 3.0. PLoS Comput Biol. 2014 May;10(5):e1003588. DOI: 10.1371/journal.pcbi.1003588. 
Tononi G, Koch C. Consciousness: Here, there and everywhere? Philos Trans R Soc Lond B Biol Sci. 2015 May 19;370(1668):20140167. DOI: 10.1098/rstb.2014.0167. 
Grossberg S. Adaptive Resonance Theory: How a brain learns to consciously attend, learn, and recognize a changing world. Neural Netw. 2013 Jan;37:1-47. DOI: 10.1016/j.neunet.2012.09.017. 
Grossberg S. Towards solving the hard problem of consciousness: The varieties of brain resonances and the conscious experiences that they support. Neural Netw. 2017 Mar;87:38-95. DOI: 10.1016/j.neunet.2016.11.003. 
McFadden J. The CEMI Field. Theory gestalt information and the meaning of meaning. J Conscious Stud. 2013;20(3-4):3-4. 
Sevush S. Single-neuron Theory of Consciousness. Journal of Theoretical Biology. 2005. 
Hameroff S, Penrose R. Consciousness in the universe: A review of the 'Orch OR' theory. Phys Life Rev. 2014 Mar;11(1):39-78. doi: 10.1016/j.plrev.2013.08.002.