Difference Between Motor and Sensory Homunculus

The key difference between motor and sensory homunculus is the type of processing each undergoes during neurological mapping. Motor homunculus is a map showcasing the motor processing of the different anatomical portions of the body while sensory homunculus is a map showcasing the sensory processing of the different anatomical portions of the body.

Homunculus is an imaginary map generated on the data available on the different neurological connections. It mainly involves the brain, sensory processing and motor processing. Furthermore, nerves and the spinal cord also play an important role in generating the homunculus.

CONTENTS

1. Overview and Key Difference
2. What is Motor Homunculus
3. What is Sensory Homunculus
4. Similarities Between Motor and Sensory Homunculus
5. Side by Side Comparison – Motor vs Sensory Homunculus in Tabular Form
6. Summary

What is Motor Homunculus?

Motor homunculus is a representative map of neurological connections. The motor homunculus focuses on motor processing of the neurological system. The primary motor cortex plays an important role in motor homunculus. The motor cortex mainly concerns the signals transmitting through the frontal lobes.

The primary cortex that transmits the signals is located at the central sulcus. Then this extends to the Sylvian fissure. In the homunculus map, this is the area called Brodmann’s area 4. According to the motor homunculus, the right cerebral hemisphere is responsible for the activities of the left side of the body and vice versa. The motor homunculus represents various sizes. The main reason for this is that the motor receptors of various parts of the body differ in size and density. Thus, the map would depict various size connections in relation to motor processing of the neurological connections.

What is Sensory Homunculus?

The sensory homunculus is the representative map of neurological connections concerning sensory processing. The signals for the sensory homunculus arrive from the thalamus to the primary sensory cortex.

The sensory cortex is situated at the posterior side of the central sulcus. It also extends to the Sylvian fissure. Therefore, the area under the sensory homunculus also falls under the Brodmann’s areas 1, 2 and 3.

The sensory homunculus represents the tactile representation of the contralateral side. Similar to the motor homunculus, the densities of the various parts of the sensory homunculus also vary in structure. It is mainly because different parts vary in size and in density.

What are the Similarities Between Motor and Sensory Homunculus?

• Motor and sensory homunculus are imaginary maps drawn by taking the neurological connections into consideration.
• Both have varying densities due to the change in structure.
• They take the brain, spinal cord and nerves into consideration.
• They can be divided into Brodmann’s areas.

What is the Difference Between Motor and Sensory Homunculus?

The key difference between motor and sensory homunculus depends on the types of connections incorporated into the map. The motor homunculus focuses on motor processing, while the sensory homunculus focuses on sensory processing. Also, another difference between motor and sensory homunculus is the pathway in which the signals arrive for the two formats; motor homunculus concerns the signals transmitted through the frontal lobes while sensory homunculus concerns the signals transmitted through the thalamus. Furthermore, the designated areas of the Brodmann also differ in both types. Thus, motor homunculus belongs to the Brodmann’s area 4 while sensory homunculus belongs to the Brodmann’s areas 1, 2 and 3.

The below infographic represents the difference between motor and sensory homunculus.

Summary – Motor vs Sensory Homunculus

Motor and sensory homunculus are two areas that show neurological connections that associate the brain, nerves and spinal cord. Motor homunculus is the imaginary map of neurological connections based on motor processing. Sensory homunculus is the imaginary map of neurological connections based on sensory processing. Each type of homunculus receives signals in different pathways. However, both connections show a variety in structure as the sizes and the densities of each vary. Furthermore, the Brodmann areas in the neurological map also vary; the Brodmann area 4 falls under motor homunculus while the Brodmann areas 1, 2 and 3 fall under Sensory homunculus. So, this is the summary of the difference between motor and sensory homunculus.

Reference:

1. “Homunculus Sensory and Motor Cortex.” EBM Consult, Available here.

Image Courtesy:

1. “Motor homunculus” By mailto:ralf@ark.in-berlin.de – File: Homunculus-ja.png Translated from Image: Homunculus-de.svg by Was a bee (CC BY-SA 4.0) via Commons Wikimedia
2. “1421 Sensory Homunculus” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia