Panpsychism is the view that everything has a mental life. Many people find this implausible because it seems weird to think that rocks and dust bunnies are cognizers in the same way that people or animals are cognizers. Panpsychism also seems to contradict the growing consensus among neuroscientists who claim that consciousness only “arises” when a certain level of cortical connectivity or information integration is present in the brain, especially in fronto-parietal circuits and other “global workspaces”.
But why think you need a sophisticated network of cortico-cortical activity in order to have a mind, to have a point of view on the world? Why not think a single neuron is a locus of mental experience? Perhaps there is a faint “something-it-is-like” from the point of view of individual neurons. I call this view neuronal panpsychism: it says that every neuron has a distinct mental life independent of its interaction with any other neuron. Of course a neurons experience is going to be significantly impacted by its causal and reciprocal interaction with neighboring neurons but the point is that the neurons themselves are loci of experience in virtue of their intrinsic nature.
But how do we account for the reams of data suggesting that a high-level of connectivity is necessary for what Stan Dehaene calls “conscious ignition”? After all, even coma patients have some preserved neuronal activity but no one thinks they are conscious: they show no external signs of consciousness at least.
The key to explaining this data in a way that’s consistent with neuronal panpsychism is the “nesting” solution. The idea is that the “macro” consciousness of normal human adults is actually composed of the “micro” experiences of all the individual neurons. The feeling of global unity is therefore an illusion according to neuronal panpsychism. The feeling of being one great unified stream of experience is actually an aggregate of billions of microexperiences in the same way that a river is composed of countless water atoms.
But what does it mean for experiences to “add up” in this way? Is there an equivalent of multiplication or taking the integral? These are tough, unresolved theoretical issues facing all brands of panpsychism. But is it any less mysterious than saying consciousness “arises” whenever informational connectivity reaches a certain threshold in frontal-parietal circuits or when there is 40z synchrony or whatever?
I actually think though neuronal panpsychism can make sense of why it feels different to have your frontal-parietal circuits activated or deactivated and why these circuits seem to make both a significant phenomenal and functional difference to the “macro” level experience of normal human adults. Neuronal panpsychism says that all neurons have mental states but that doesn’t mean they all have the same kind of mental states. For example, a motor neuron might have a different experience than a Von Economo neuron, or a cerebellar neuron might have a different experience than a neuron than lives in the prefrontal cortex.
In effect neuronal panpsychism is a kind of microfunctionalism where neurons with different functional profiles have different mental lives. These functional differences arise from both their phylo and ontogenetic history i.e. different types of neurons have different inherited genetic programming but they also have unique, individualized learning experiences.Thus. the differences in felt macro experiences when there are high levels of frontal-parietal activity are due to the unique experiences of those neurons being added to the choir of subcortical neurons. But they are not the origin of phenomenality, only the “loudest” phenomenality or “most famous” phenomenality, to borrow a metaphor from Dan Dennett’s “fame in the brain” theory (which is an intellectual precursor to neuronal panpsychism).
Thus, when a vegetative patient is transitioning to the minimally conscious state and onwards to normal consciousness there is never one unique threshold when consciousness gets “turned on”. Consciousness is not all or nothing. Consciousness is not a special property of only a unique set of cortical circuits in mammals with sufficiently activated global workspaces. According to neuronal panpsychism, ALL neurons contribute to what-it’s-like to be a unified mind or “I”.
But why stop at neurons? Why not think glial cells have mental lives too? Indeed, why not claims all cells have mental lives? This would be “cellular panpsychism”. But that’s another post.