A review of the sufficient conditions for consciousness

The hard problem of consciousness asks how subjective experience arises from physical processes. Neuroscience has focused on the cortex and subcortex while discounting the cerebellum, but neuroimaging shows that cerebellar, cortical, and subcortical functions all correlate with consciousness. Neurostimulation evidence indicates that alterations in any brain region can change experience, with the most extreme changes coming from the subcortex. Neuropsychological findings show that damage to any part of the brain can alter experience, but only damage to the oldest regions can completely eliminate it. Congenital and experimental decorticate cases suggest that behaviors indicating basic experiences are possible without a cortex. The body, subcortex, and environment together appear sufficient for behaviors suggesting basic experiences, highlighting the importance of developmental trajectory and neural interdependencies.

Study at a glance

Abstract

How subjective experience (i.e., consciousness) arises out of objective material processes has been called the hard problem. The neuroscience of consciousness has set out to find the sufficient conditions for consciousness and theoretical and empirical endeavours have placed a particular focus on the cortex and subcortex, whilst discounting the cerebellum. However, when looking at neuroimaging research, it becomes clear there is substantial evidence that cerebellar, cortical and subcortical functions are correlated with consciousness. Neurostimulation evidence suggests that alterations in any part of the brain may provoke alterations in experience, but the most extreme changes are provoked via the subcortex. I then evaluate neuropsychological evidence and find abnormality in any part of the brain may provoke changes in experience; but only damage to the oldest regions seem to completely obliterate experience. Finally, I review congenital and experimental decorticate cases, and find that behavioral evidence of experience is largely compatible with the absence of the cortex. The evidence, taken together, indicates that the body, subcortex and environment are sufficient for behaviours that suggest bastic experiences. I then emphasise both the importance of the individual's developmental trajectory and the interdependencies between different neural systems.