Homunculus on our brain surface

cropped brain surface

“Homunculus” refers to a small human or a “humanoid” creature.

Do we have it on our brain surface?

Yes, we can find a homunculus (figuratively) as a map in our brain.

Not just one, in fact, we have “two little humanoids”!.

This is the story behind this amazing discovery.

In 1937, two brilliant scientists, Dr Wilder Penfield and Edwin Boldrey embarked on a journey to unravel the mysteries of the human brain. They were operating at McGill University, in Montreal, Canada with a mission to map the brain regions that receive sensory information from the skin and those that send signals to move the corresponding body parts.

Their journey took a surprising turn when they discovered two little shapes on the surface of the brain. They were intrigued by their finding and dedicated themselves to studying these shapes in depth.


They meticulously mapped the brain regions and soon realized that these two shapes were exactly similar to “two little humanoids” lying on the brain surface.

The scientists were amazed by their discovery. They found that the brain surface had very distinct regions that exactly corresponded to and accounted for different body regions. This meant that each part of the body had its corresponding area on the brain surface, controlled by these “two little humanoids”.

The scientists documented their findings in a 50-page-long article, published in the “Brain” journal. The article was accompanied by detailed drawings and illustrations, showcasing the discovery of these two little humanoids. The article is about a map of the human brain that shows how it controls movement and sensation.

According to Marco Catani, The data for the map came from 126 patients who had surgery while awake and could talk about what was happening. The information was gathered between 1928 and 1936 by Dr Penfield. He put all the patient recordings together to make the first complete map of how the brain controls movement and sensation. The map shows a distorted human shape, called a homunculus, which shows how much of the brain is used for each part of the body.

The article was a landmark in the field of neuroscience and received widespread recognition.

Figure 1: Dr Penfield and Boldrey and their little men Courtesy: https://academic.oup.com/brain/article/140/11/3055/4566636

These “Two little humans” (Figure 1) – now famously called “Homunculus of the brain” – lie along the Central Sulcus, which separates the Frontal lobe from the Parietal and Temporal lobes.

Years have passed. The two little humanoids’ “discovery” helped improve our understanding of the human brain. This knowledge has inspired scientists to dig deeper into the brain’s mysteries.

Homunculus in the brain

Figure 2: Left homunculus

Source: Wikimedia Commons: Polygon data are from BodyParts3D[1]. Author: Polygon data were generated by the Database Center for Life Science(DBCLS)[2]. Permission: under the license of CC BY SA 2.1.

File:BA312 - Primary Somatosensory Cortex - lateral view - with homunculus.png

Figure 2 depicts the two little humans who lie (figuratively) on either side of the Central sulcus – a groove that separates the Frontal lobe from the Parietal lobe (You can read this on the Journeys to the brain -2: A walk over the brain surface).

Let us start with Figure 3.

Figure 3 (below) marks the distinct geographical areas of the brain that look after the specific body parts.

When we climb, we will step on the areas that receive information and send commands to the facial structures. Further up, we will find the regions that receive the information and send instructions. It follows a highly organized distinct pattern. And, the more complex the job is, the larger the designated area.

Figure 3: Homunculus regions

Source: Wikimedia Commons: OpenStax College Anatomy & Physiology, Connexions Website:  http://cnx.org/content/col11496/1.6/, Jun 19, 2013, under the license of Creative Commons. CC BY 3.0

<strong>Figure 4: Image source</strong>: <a href="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c4/1421_Sensory_Homunculus.jpg/482px-1421_Sensory_Homunculus.jpg">Wikimedia Commons </a>

The role of homunculus in stroke recovery

This cortical representation of the homunculus is a picture of a distorted human shape that shows how much of the brain is used for different body parts. Although the picture might not be completely accurate, it’s still interesting because it shows that separate body parts have different amounts of brain space dedicated to them. This is because body parts with more important functions, like the hands and mouth, need more brain space to control them. The bigger a body part is in the picture, the more brain space it has dedicated to it. This means that the picture helps show how each body part is specialized for different functions.

The historical discovery of homunculus by Wilder Penfield and Edwin Boldrey can be used to identify which areas of the brain are responsible for controlling specific body parts, making it possible to tailor rehabilitation programs specifically for each patient. For example, if a stroke patient has difficulty moving the arm, you know which brain area is damaged.

Another benefit of using the homunculus in stroke rehabilitation is that it provides a visual representation of the brain and its functions. This can be helpful for both healthcare professionals and patients, as it makes it easier to understand the effects of a stroke and the progress of rehabilitation. For patients, seeing the homunculus can provide a sense of hope and motivation, as they can see which areas of the brain are being targeted and the potential for improvement.

The discovery of the homunculus has been extremely useful in the field of stroke rehabilitation. By providing a comprehensive map of the brain and its functions, healthcare professionals can tailor rehabilitation programs to individual patients, making it possible to provide more effective care. Additionally, the visual representation of the brain provided by the homunculus can be helpful for both patients and healthcare professionals, providing hope and motivation for recovery.

The discovery of the homunculus has led to the development of several tools that can improve stroke recovery. These tools include:

Motor Imagery: Motor imagery is a technique where patients imagine themselves performing movements, even if they can’t physically perform them. This technique can be guided by the homunculus, as it allows healthcare professionals to identify which areas of the brain are responsible for specific movements. By targeting these areas, motor imagery can help improve recovery.

Constraint-Induced Movement Therapy (CIMT): CIMT is a type of physical therapy that restricts the use of an unaffected limb and forces the affected limb to be used more. The homunculus can be used to identify which limb is affected and tailor the therapy to target specific movements.

Neurofeedback Training: Neurofeedback training uses sensors to monitor brain activity and provide feedback to the patient. The homunculus can be used to identify which areas of the brain are responsible for specific movements and target these areas during neurofeedback training.

Robotics and Virtual Reality (VR) Therapy: Robotics and VR therapy use technology to create interactive environments that can help patients practice movements and improve their ability to perform them. The homunculus can be used to tailor these therapies to target specific movements and improve recovery.

Health education tools that use homunculus in stroke recovery education for patients

Visual aids: Homunculus diagrams and illustrations are used to help patients understand the relationship between different body parts and the corresponding areas in the brain. These visual aids can be found in medical textbooks, brochures, or in educational videos created by medical institutions or healthcare providers.

  1. Wall charts and posters: Large wall charts and posters that display the homunculus can be placed in patient rooms, rehabilitation centers, and doctor’s offices to help patients understand the relationship between their body and brain.
  2. Brochures and handouts: Handouts and brochures that feature illustrations of the homunculus can be given to patients to help them better understand the relationship between their body and brain. These can be handed out during appointments or given to patients to take home and study.
  3. Online videos: Animated videos that feature the homunculus can be found online and used to help patients understand the relationship between their body and brain. These videos can be accessed through websites, YouTube, or other online video platforms.
  4. Medical textbooks: Medical textbooks that feature illustrations of the homunculus can be used as reference materials for patients and healthcare providers. These can be found in libraries, bookstores, or online.

Interactive software: Interactive software programs are available that allow patients to explore the homunculus and learn about the different body parts and their corresponding areas in the brain. These programs can be accessed through a computer or mobile device and may be available for free or as part of a paid subscription service.

Workshops and classes: Workshops and classes that focus on stroke recovery often use homunculus as a tool to help patients understand the relationship between their body and their brain. These classes may be offered by rehabilitation centers, hospitals, or community organizations and can be led by physical therapists, occupational therapists, or other healthcare professionals.

You can read about the brain’s blood supply by joining me on another journey.   

Author: Ed Jerard

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