Sleepwalking involves typically automated behaviour and occurs most often in young children. It occurs more frequently after sleep deprivation and the prevalence is 1%-5%. It typically occurs during the deepest stages of sleep and the frontal cortex is deactivated during sleepwalking.

In normal sleep, there are successive sleep stages. Cycles last ±90 minutes. Deep sleep stages occur in the early part of the night. It includes high amplitude, low-frequency EEG. REM-sleep stages occur towards the end of the night.  

Sleep paralysis refers to the muscle tone remaining flat because of muscle paralysis, but the person is awake. This is also shown on EEG. Sleep violence refers to REM-sleep without muscle paralysis. Narcolepsy is the sudden onset of REM-sleep. There are several disorders of consciousness:

1. Brain death
   No pupil response, no reflexes, no EEG.
2. Coma
   No reactions, no sleep-wake cycle. It is often short-lived and either results in death, vegetative state or waking up. Life support is often needed.
3. Vegetative state
   A sleep-wake cycle, breathing, autonomous reactions, eye movements, orienting, no reactions, no communication.
4. Minimally conscious
   The same as the vegetative state, but the person sometimes regains consciousness and communication.
5. Locked-in syndrome
   Being fully awake, but being unable to respond, except for a single muscle (e.g., eyelid).

The reticular activation system (RAS) is critical for maintaining consciousness. It either projects directly to the cortex or via the thalamus. Easy problems of consciousness include problems of consciousness that are very difficult to understand and explain, but it is possible to envision a solution. Hard problems of consciousness refer to explaining qualia. There is an explanatory gap, explaining the function of consciousness does not explain the experience of that part of consciousness.

Blindsight refers to not being able to consciously report stimuli in the visual field, but act appropriately as if one was still able to see. It is mediated via projections of the optic tract to the superior colliculus, which projects to the dorsal stream areas. Super blindsight refers to the ability of monkeys and humans with bilateral primary visual cortex lesions to behave normally.

The dorsal stream includes vision for action. The ventral stream includes vision for perception.  Looking for the neural correlate of consciousness (NCC) through elimination may leave no area of the brain as belonging to the neural correlate of consciousness.

It is also possible to study the neural correlate of consciousness by studying which regions contribute to the conscious percept. This can be studied by using bi-stable stimuli (stimuli that remains constant but the constant percept switches spontaneously), electrical stimulation and illusions.

In a binocular rivalry task, there are two percepts and the participant looks at the middle. One percept dominates and this switches. A higher contrast or sharper image dominates longer in a binocular rivalry task. If MT neurons are stimulated, the preferred direction of these neurons will be reported more often, instead of the actual direction of the stimulus.