Key, B., Zalucki, O.H., & Brown, D.J. (2022). A first principles approach to subjective experience. Frontiers in Systems Neuroscience, 16. doi:10.3389/fnsys.2022.756224
[Abstract]Understanding the neural bases of subjective experience remains one of the great challenges of the natural sciences. Higher-order theories of consciousness are typically defended by assessments of neural activity in higher cortical regions during perception, often with disregard to the nature of the neural computations that these regions execute. We have sought to refocus the problem toward identification of those neural computations that are necessary for subjective experience with the goal of defining the sorts of neural architectures that can perform these operations. This approach removes reliance on behaviour and brain homologies for appraising whether non-human animals have the potential to subjectively experience sensory stimuli. Using two basic principles—first, subjective experience is dependent on complex processing executing specific neural functions and second, the structure-determines-function principle—we have reasoned that subjective experience requires a neural architecture consisting of stacked forward models that predict the output of neural processing from inputs. Given that forward models are dependent on appropriately connected processing modules that generate prediction, error detection and feedback control, we define a minimal neural architecture that is necessary (but not sufficient) for subjective experience. We refer to this framework as the hierarchical forward models algorithm. Accordingly, we postulate that any animal lacking this neural architecture will be incapable of subjective experience.
[Citing Place (1956)]  
Citing Place (1956) in context (citations start with an asterisk *):
* Our approach begins with the basic principle that subjective experience is dependent on neural processing involving the execution of specific functions rather than merely being a result of the firing of neurons. For example, others have argued that neural firing of C-type peripheral sensory neurons just is pain (Putnam, 1960) — an idea that has strongly influenced philosophical mind-brain debates (Puccetti, 1977; Levin, 2005; Montero and Brown, 2018; Polák and Marvan, 2018; Van den Hombergh, 2020). Rather than being pain, C-type firing may be just background noise without eliciting sensation (Schäfers and Cain, 2004; Ermentrout et al., 2008). Alternatively, given that C-fibres are polymodal (Perl, 2007), firing of these neurons may instead represent either nociception or innocuous heat/cold/mechanical sensations. Aside from lacking mechanistic explanatory power, such claims of type-type identity are focussed at the wrong level of abstraction just as claiming that water is an oxide would be. A more promising view is that subjective consciousness is not neural activity per se but rather a specific type of neural process (Place, 1956; Smart, 1959; Polger, 2011; Polák and Marvan, 2018). How, though, could a neural process be the same thing as a subjective experience? An analogy can be found in the arithmetic operation of summing two numerals. The process of summing is addition and addition just is the process of summing. Addition is not something “over and above” the computational process itself. Accepting type-type identity between subjective experience and certain kinds of neural processes would resolve the problem facing dualist or epiphenomenalist accounts that a non-materialistic subjective experience cannot have causative power because if subjective experience is just a physical process, it can be causative. Nonetheless, the challenge of identifying those neural processes that are subjective experiences would remain. We are a long way from being able to specify necessary and sufficient conditions for subjective experience.