" Now, here is the kicker: while hemi-neglect can occur when there is actual loss of sensation or motor systems, a version of it can also occur when all sensory systems and motor systems are in good working order—a syndrome known as extinction. In this case each half brain seems to work just fine alone, but it begins to fail when required to work at the same time as the other half. Yet information in the neglected field can be used at a nonconscious level!5 That means the information is there, but the patient isn’t conscious it is there. Here is how it works. If patients with left hemi-neglect are shown visual stimuli in both their right and left visual fields at the same time, they report seeing only the stimulus on the right. If, however, they are shown only the left visual stimulus, hitting the same exact place on the retina as previously, the left stimulus is perceived normally. In other words, if there is no competition from the normal side, then the neglected side will be noticed and pop into conscious awareness! What is strangest of all is that these patients will deny that there is anything wrong; they are not conscious of the loss of these circuits and their resulting problems. It appears, then, that their autobiographical self must be derived only from what they are conscious of. And what they are conscious of is dependent on two things. First, they are not conscious of circuits that are not working. It is as if the circuits never existed and consciousness for what the circuits did disappears with the circuit. The second thing is that some sort of competitive processing is happening. Some circuits’ processing makes it into consciousness while others’ does not. In short, conscious experience seems tied to processing that is exceedingly local, which produces a specific capacity, and that processing can also be outcompeted by the processing of other modules and never make it to consciousness. This has astounding implications. "
― Michael S. Gazzaniga , The Consciousness Instinct: Unraveling the Mystery of How the Brain Makes the Mind