“Two little humans”: Journeys to the brain-3

The little human”:

image source: Wikimedia Commons 

In this journey, we will meet “Two little humans” who “live” on the brain surface. Dr. Wilder Penfield and Edwin Boldrey “discovered” them in 1937.

That is an amazing story.

They began their expedition while working at McGill University. Dr. Wilder Penfield served there as a brain surgeon. During that time, while operating under local anesthesia, they mapped corresponding brain regions where the sensory information are received from different body parts. They also succeeded in demonstrating the corresponding brain regions which send signals to move relevant body parts.

Together with Edwin Boldrey, he published their story in the “Brain” journal writing a 50-page long article with drawings.

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

“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.

Homunculus in the brain

Figures 2 depicts the two little humans who lie along 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).

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

Figure 2: Left homunculus

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

As you can see in Figure 3 (below), the upper inside surface area controls our feet and legs. Let us start with Figure 2. When we begin to climb, we will step on the areas that receive information from and send commands to the facial structures. Further up, we will find areas that receive information and send commands to arms, body, legs, and feet. It follows a highly organized distinct pattern. And, the more complex the job is, the larger the designated area.

<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>

Figure 3: Homunculus regions

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

This information is very useful for carers because most of the time, these are the body parts affected due to stroke You can read about the brain’s blood supply by joining me on another journey.   

Author: Prasantha De Silva

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