All parts of the brain › Functions › Consciousness

What part of the brain controls consciousness?

No single part, and no agreed seat. [1][2][3]

The 3D brain needs JavaScript. The list of parts still says what each one does for consciousness.

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All 7 parts are lit together. Drag to turn, pinch or scroll to zoom, tap a part on the brain or a name in the list to focus it; .

Scientists split consciousness into two things: its level (being awake and aroused) and its content (what you are aware of). The level depends on the ascending reticular activating system, nuclei in the reticular formation of the upper brainstem whose signals reach the cortex through the thalamus and the hypothalamus; the content depends on the cerebral cortex working with the thalamus, and which cortical areas matter most is still argued. [1][2][3]

Consciousness: 7 parts lit

Midbrain, pons, medulla oblongata, thalamus, hypothalamus, cingulate gyrus and prefrontal cortex. Tap one to see where it is and what it does.

The parts and their roles

Its reticular formation holds the core of the ascending reticular activating system, and cholinergic nuclei at its border with the pons project to the thalamus; this upper-brainstem network acts as an on/off switch for the cerebral cortex and is an important enabling factor for being conscious at all. [4][1] Where is the midbrain?
Its upper part carries more arousal nuclei of the reticular formation, among them the locus coeruleus, the brain’s main source of noradrenaline, which is most active when you are awake and alert and almost silent in REM sleep. [4][5] Where is the pons?
The reticular formation runs on down through the medulla to its lower end, but the arousal-sending part lies higher up: the medullary reticular formation mainly sends signals down the spinal cord for posture and movement. It is lit because the reticular formation is one column through all three parts. [4] Where is the medulla oblongata?
Regulates arousal, the level of awareness and sleep and wakefulness: its intralaminar nuclei receive the brainstem’s arousal signals, and its strong two-way links with every region of the cortex carry them on. [6][1] Where is the thalamus?
Its lateral part makes orexin, whose neurons reach every component of the arousal system and steady wakefulness, and its tuberomammillary nucleus is the brain’s source of histamine, another wake-promoting signal. [2][7][8] Where is the hypothalamus?
Its back part, the posterior cingulate cortex, is a central hub of the default mode network, is active during self-related thinking, has been put forward as a neural substrate of human awareness, and runs about 40% above the brain’s average metabolic rate. [9][10] Where is the cingulate gyrus?
Crick and Koch proposed that the neural correlate of consciousness lies in the prefrontal cortex, and the global workspace theory holds that information becomes conscious when frontal and parietal networks broadcast it widely across the cortex. [1][11] Where is the prefrontal cortex?

How they work together

Being awake comes first: to be conscious of anything the brain must be in a fairly high state of arousal. The arousal system uses several chemical signals (acetylcholine, noradrenaline, serotonin, dopamine, histamine, glutamate) and reaches the cortex by two main routes: a thalamic route made mostly of cholinergic neurons in the pons, and a hypothalamic route made mostly of neurons that release monoamines. [1][2]
Level and content can come apart. In REM sleep the body is still and hard to wake, yet the cortex is highly active and dreams are vividly experienced, though usually not remembered; the richness of experience also grows step by step from deep sleep to drowsiness to full wakefulness. [1][12]
Where the content lives is the open question. One line of work places it in an interaction of the temporal, parietal and occipital lobes at the back of the brain (a view tied to integrated information theory); another stresses the prefrontal cortex (global workspace theory). Experiments have not settled it. [1][13][11]
Honest limit: there is no agreed single seat of consciousness, so this page shows the arousal system plus the cortical hubs the cited sources name, not a proven circuit. The reticular nuclei, the intralaminar thalamic nuclei and the orexin and histamine cells are each a few millimetres across and have no separate shape on this model, so the whole part that holds them lights; the back-of-the-brain cortex is not lit here. [1][4]

The switch that turns the arousal system down at night, the hypothalamus’s ventrolateral preoptic nucleus, and the clock that times it are lit on the sleep page. [14] What part of the brain controls sleep?

Sources

Facts describe anatomy and normal function only. A part lit here takes part in consciousness; it does not do it alone, and it does other jobs too. The 3D model is the adult male BodyParts3D brain (credits and licence); on it the brainstem includes the midbrain, pons and medulla, so lighting the brainstem lights all three.