Homunculus And Neuroplasticity

DID YOU KNOW YOU HAVE A MAP OF YOUR BODY ON YOUR BRAIN?

MEET YOUR HOMUNCULUS!

The largest part of your brain, the cerebral cortex (pictured below), is the main center for information processing.

The cerebral cortex has designated sections for motor (movement) and sensory (sensations/physical feelings) functions and actions. Within those motor and sensory areas, the cortex breaks down into specific designated areas for processing information from each part of the body. This creates a sort of “map” of your body on your cortex that is referred to as the cortical homunculus.

For more information on the cortical homunculus, you might reference this Wikipedia article: https://en.wikipedia.org/wiki/Cortical_homunculus

This image is a cross-sectional representation of how your brain views your body!

Notice that it assigns a larger area (and therefore more neurons) to areas that you need more specific information from. For example, it’s important for you to have accurate and fine-tuned sensation and motor function in your hands, so the hands take up a larger portion of your brain than, say, your kneecaps.

Here’s a closer look.
This representation of your body in your brain is adaptable! If you use your hands for a lot of fine motor work (think piano players and violinists), your brain can assign even more neurons to your hands so that you can have even more awareness and control. The ability for the brain to adjust its wiring to meet your specific needs is called neuroplasticity.

This brief video offers a bit more information on neuroplasticity: https://www.youtube.com/watch?v=kWIagHUqD8A

Next time you feel your lower back hurting, do not panic! Remember that most cases of low back pain will get better in a few days or weeks. Take comfort in knowing that undergoing an X-ray or MRI will not make your back pain go away faster. So, keep calm, call your physical therapist, and keep moving!

Neuroplasticity allows your brain to learn, move and perform better by adapting to your specific needs. However your nervous system’s adaptability can occasionally cause some problems. For example, in people who suffer from chronic pain (pain lasting longer than 3 months), areas of the brain activate that are not normally responsible for processing pain information. Chronic pain also sometimes results in something called homuncular smudging – that is, the motor and sensory areas of the cortex that represent a certain body part blur or smudge into neighboring or related neurons in the brain, making the cortical representation of that body part less distinct.

The Director of the Neuro Orthopedic Institute, Dr. David Butler, PT, EdD, gives an excellent explanation of the process and consequences of smudging in this video:  https://www.youtube.com/watch?v=3QVAY5stO3U

Neuroplasticity and other adaptive changes to neuron function do not only occur in the brain – neurons in the spinal cord and limbs also adapt their connections and signaling behavior. The combination of these various adaptive changes can lead to a complicated chronic pain state called pain hyper-sensitization, or central sensitization.

We’ll talk more about central sensitization in a future post, but for now, let’s recap what you’ve learned:

    1. Your brain contains a “map” of your body, where specific areas process motor and sensory information from each body part. This is called the homunculus.
    2. These brain areas, connections and signaling processes are adaptable! Communications between neurons can rearrange, up-regulate and down-regulate, adjusting to new information and adapting signaling to reflect individual experience. This is called neuroplasticity.
  • Occasionally these neuroplastic events can cause you to become more sensitive to stimuli over time, resulting in more pain for the same stimulus. This is called central sensitization.

But there’s one more major take-away here: Your amazing brain is adaptable in both directions. Many processes or signals which have been up-regulated can be down-regulated again. Connections that have been strengthened can also be weakened over time, or vice-versa. And a homunculus that has smudged can be re-sharpened. Your physical therapist can help you through this process.

In good health,
Kim Tjoelker PT, DPT, OCS

Image credits:
Images 1 & 2 : cerebral-cortex
Image 3: Illustration from Anatomy & Physiology, Connexions Web site. Ch. 1 Introduction – Anatomy and Physiology, Jun 19, 2013.

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