Hindbrain: Parts & Function

The hindbrain (also called the rhombencephalon) is a vital part of the brain located at its base, just above the spinal cord.

It acts as the body’s control center for essential, automatic functions such as breathing, heart rate, balance, and sleep, without which we would not survive.

Remarkably, it also supports complex, learned movements like walking or dancing, alongside these automatic survival functions.

Evolutionary Context of the Hindbrain

The hindbrain is often called one of the oldest parts of the brain. Every vertebrate, from ancient fish to humans, has one.

This shared ancestry shows the hindbrain evolved very early, over 400 million years ago, long before more complex brain regions appeared. Because of this ancient origin, the hindbrain handles the basic, life-sustaining processes every animal needs to survive.

It acts as the body’s autopilot, controlling automatic functions like breathing, heart rate, and balance. These jobs have barely changed throughout evolution. The hindbrain was essential for early species, and it remains just as essential in humans today.

Key Functions of the Hindbrain

The hindbrain’s role extends beyond basic survival functions to include several sophisticated processes:

• Autonomic Regulation: Controls essential life functions including breathing rhythm, heart rate, blood pressure, and digestion. These processes continue even when we’re unconscious, ensuring our survival.
• Motor Control and Learning: Coordinates precise movements, maintains balance, and helps us learn new physical skills. This includes everything from maintaining posture while standing to learning complex dance movements.
• Sensory Integration: Processes and integrates information from our senses, particularly those related to balance, spatial orientation, and movement. This integration helps us navigate our environment effectively.
• Sleep and Arousal: Regulates sleep cycles and levels of wakefulness, helping maintain normal sleep patterns and appropriate alertness during waking hours.
• Reflexive Behaviors: Controls automatic responses like coughing, sneezing, and swallowing that protect our airways and help maintain bodily functions.

Parts of the Hindbrain

The hindbrain consists of three main structures: the pons, the medulla oblongata, and the cerebellum.

The pons acts as a relay bridge, the medulla oblongata is the brainstem’s lowest, life-sustaining segment, and the cerebellum is a highly folded structure that fine-tunes movement and balance. Each plays a unique role in keeping the body running smoothly.

Pons: The Brain’s Communication Bridge

The pons (Latin for “bridge”) is a rounded bulge of tissue within the brainstem (the stalk of nerve tissue connecting the brain to the spinal cord).

It connects different parts of the brain and serves as a key messaging hub. It links the cerebral cortex (the brain’s outer layer, responsible for higher-level thinking) to the cerebellum and the spinal cord below.

Key roles of the pons include:

• Assisting in breathing rhythm and sleep regulation
• Relaying auditory and sensory information
• Hosting cranial nerves that manage eye movement, facial expressions, chewing, and balance
• Supporting motor learning and alertness through the reticular formation and pontine nuclei

The pons plays a critical role in both survival and movement coordination, helping us transition from rest to action.

This arousal role has a long research history. Moruzzi and Magoun’s classic 1949 experiment showed that stimulating the reticular formation, a network of neurons running through the pons and medulla, could instantly wake a sleeping animal’s brain.

Edlow et al. (2024) tested this with modern brain-scanning technology, combining detailed scans of three human brainstems with functional MRI from 84 healthy adults. Rather than finding a single “on/off” switch, they mapped eighteen separate brainstem and forebrain regions that work together to keep us awake and alert.

Cerebellum: Master of Movement and Balance

The cerebellum (“little brain”) is located behind the pons. It fine-tunes our movements and helps us stay balanced without thinking about it.

While once believed to only handle physical coordination, the cerebellum is now known to be involved in:

• Motor learning and reflex memory
• Emotional regulation and cognitive tasks
• Sequence learning (like playing piano or typing)

Despite making up only about 11% of the brain’s weight, the cerebellum holds the vast majority of the brain’s neurons. Roughly 69 billion of the brain’s 86 billion neurons sit in the cerebellum alone, around four out of every five (Herculano-Houzel, 2009).

Specialized cells called Purkinje cells enable it to process massive amounts of information quickly and accurately.

The cerebellum’s job goes beyond movement, too. Ivry and Keele (1989) tested patients with cerebellar damage on tasks requiring precise timing, even when no movement was involved. These patients struggled significantly more than healthy participants, showing the cerebellum also works as an internal timing device.

Medulla Oblongata: Guardian of Vital Functions

The medulla is the brainstem’s lowest part, connecting directly to the spinal cord. It is also where most of the brain’s descending motor pathways cross to the opposite side of the body. This crossover matters. Damage to one side of the brain therefore affects movement on the other side.

It controls many of the body’s automatic functions that keep us alive, such as:

• Breathing and heart rate
• Blood pressure and circulation
• Coughing, sneezing, swallowing, and vomiting reflexes

It also houses cranial nerves responsible for taste, voice, head movement, and speech. Damage to the medulla can be life-threatening because it disrupts critical functions like breathing and heartbeat.

Damage to the Hindbrain

Early warning signs of damage to the hindbrain can include:

• Persistent dizziness or balance problems
• Difficulty swallowing or breathing
• Sudden coordination problems
• Unexplained sleep disturbances
• Slurred speech without other explanation

Damage to the hindbrain can have severe consequences due to its role in vital functions. The effects vary depending on which structure is affected:

Types of Damage and Effects

• Pons Damage
  • Impairs breathing and sleep patterns
  • Affects taste perception and muscle function
  • Can cause “Locked-in Syndrome,” where patients remain conscious but cannot move voluntarily except for eye movements
  • May result from pontine stroke, leading to partial or complete paralysis
• Medulla Damage
  • Can be fatal due to disruption of breathing and heart function
  • Research has shown that medulla damage in Parkinson’s disease patients correlates with cardiac and respiratory problems (Pyatigorskaya et al., 2016)
  • Affects basic reflexes like swallowing and breathing
• Cerebellum Damage
  • Disrupts coordination and balance
  • Causes tremors and difficulty walking
  • Affects speech clarity
  • Studies show cerebellar dysfunction is linked to developmental disorders including autism and ADHD (Stoodley, 2016)
  • Research has found reduced Purkinje cells in autistic individuals, potentially affecting signal processing (Whitney et al., 2008)

Protecting the Hindbrain

While some conditions are unavoidable, healthy habits can lower the risk of hindbrain injury:

• Use safety gear: Helmets and seatbelts protect the back of the head during accidents.
• Limit alcohol: Alcohol affects cerebellar function, even short-term.
• Exercise regularly: Supports circulation and reduces stroke risk.
• Eat a healthy diet: Helps manage blood pressure and brain health.
• Avoid smoking: Smoking raises stroke and cardiovascular risks.

References

Edlow, B. L., Olchanyi, M., Freeman, H. J., Li, J., Maffei, C., Snider, S. B., Zöllei, L., Iglesias, J. E., Augustinack, J., Bodien, Y. G., Haynes, R. L., Greve, D. N., Diamond, B. R., Stevens, A., Giacino, J. T., Destrieux, C., van der Kouwe, A., Brown, E. N., Folkerth, R. D., … Kinney, H. C. (2024). Multimodal MRI reveals brainstem connections that sustain wakefulness in human consciousness. Science Translational Medicine, 16 (745), Article eadj4303. https://doi.org/10.1126/scitranslmed.adj4303

Herculano-Houzel, S. (2009). The human brain in numbers: A linearly scaled-up primate brain. Frontiers in Human Neuroscience, 3, 31.

Ivry, R. B., & Keele, S. W. (1989). Timing functions of the cerebellum. Journal of Cognitive Neuroscience, 1 (2), 136-152.

Jou, R. J., Minshew, N. J., Melhem, N. M., Keshavan, M. S., & Hardan, A. Y. (2009). Brainstem volumetric alterations in children with autism. Psychological Medicine, 39 (8), 1347.

Kolb, L. C. (1987). A neuropsychological hypothesis explaining posttraumatic stress disorders. The American Journal of Psychiatry, 144, 989-95.

Pyatigorskaya, N., Mongin, M., Valabregue, R., Yahia-Cherif, L., Ewenczyk, C., Poupon, C., Debellemaniere, E., Vidailhet, M., Arnulf, I. & Lehéricy, S. (2016). Medulla oblongata damage and cardiac autonomic dysfunction in Parkinson disease. Neurology, 87 (24), 2540-2545.

Stoodley, C. J. (2016). The cerebellum and neurodevelopmental disorders. The Cerebellum, 15 (1), 34-37.

Tedesco, A. M., Chiricozzi, F. R., Clausi, S., Lupo, M., Molinari, M., & Leggio, M. G. (2011). The cerebellar cognitive profile. Brain, 134 (12), 3672-3686.

The University of Queensland. (n.d). The hindbrain. Retrieved April 29, 2021, from https://qbi.uq.edu.au/brain/brain-anatomy/hindbrain

Whitney, E. R., Kemper, T. L., Bauman, M. L., Rosene, D. L., & Blatt, G. J. (2008). Cerebellar Purkinje cells are reduced in a subpopulation of autistic brains: a stereological experiment using calbindin-D28k. The Cerebellum, 7 (3), 406-416.

Xi, Z., & Luning, W. (2009). REM sleep behavior disorder in a patient with pontine stroke. Sleep medicine, 10 (1), 143-146.