Primary Sensory Cortex

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Author: Angela Pike

Grade Level: 9th - 12th; Type: Life Science


  • Compare the sensitivity of touch receptors in different areas of the body.
  • Compare the sensitivity of touch receptors between different people.

Research Questions:

  • What is the Central Nervous System?
  • What is the Peripheral Nervous System?
  • Identify the types of information processed by the following areas of the cerebral cortex: frontal lobe; parietal lobe; temporal lobe; occipital lobe.

The primary sensory cortex is the portion of the brain where your sense of touch is interpreted. Different parts of your body send their information to different portions of the cortex.


  • 9 toothpicks
  • Metric ruler
  • Tape
  • Blindfold (optional)
  • Partner

Experimental Procedure:

  1. Place the ruler on the table.
  2. Lay 3 toothpicks side-by-side on one end of the ruler. The toothpicks should be touching each other. Now tape them in this position. Record the distance between the toothpicks in Table 1 under "Position 1".
  3. Choose 3 more toothpicks and place them on the other end of the ruler. This time space them a little further apart, but space them evenly. Tape them into position. Record the distance between the toothpicks in Table 1 under "Position 2."
  4. Choose 3 more toothpicks and place them in the center of the ruler. This time space them a littler further apart (the widest spacing). Tape them into position and record the distance in Table 1 under "Position 3."
  5. With your partner's eyes closed and their hand laid on a table, gently touch the tip of their dominant index finger with the tip of two toothpicks at position 1. Ask your partner how many tips they felt. Record in Table 1.
  6. Repeat step 5 using two toothpick tips at positions 2 and 3.
  7. Repeat steps 6 and 7 using three toothpick tips.
  8. Repeat steps 5, 6, and 7 using the inside of your partner's forearm instead of their index finger.
  9. Was your partner's finger or forearm more sensitive to the touch of the toothpicks?
  10. Which area of the body, finger or forearm, has more space reserved for its use in the primary sensory cortex? Explain.

   Table 1

 Toothpick Position  Index Finger    Forearm  

Position 1

Distance between

toothpicks _______cm

 Tips used  Tips sensed  Tips used  Tips sensed
   2    2  
   3    3  

Position 2

Distance between

toothpicks _______cm

 2    2  
   3    3  

Position 3

Distance between

toothpicks _______cm

 2    2  
   3    3  


Terms/Concepts: Cerebrum;  Primary sensory cortex


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