Cutting the corpus callosum (split-brain) broadly disrupts functional integration across perception and attention, but some processes like action control remain unified. The key unresolved question is whether split-brain patients have split or unified consciousness. Current evidence is insufficient to decide, and future studies may need to consider intermediate conceptualizations beyond a simple yes or no.
The subjective feeling that consciousness is singular—that there is only one 'me'—may be an illusion created by the need to respond coherently to the environment. A review of neuropsychological conditions such as anosognosia, neglect, and split-brain, alongside psychiatric disorders and psychoactive drugs, suggests that perceptual, language, memory, attentional, and motor processes can operate largely in parallel without integration. The sense of unity, or 'Me-ness', arises only when an organism must produce a coherent response constrained by environmental affordances.