Do a study of the two-point threshold . Have a friend take a pair of scissors an

Question

Do a study of the two-point threshold. Have a friend take a pair of scissors and, with the blades closed, touch you lightly on the forearm with the points while your eyes are closed. Have your friend open the blades slightly and touch you with both points at the same time. Have your friend continue to spread the blades and touch you just to the point at which you can feel both blades. Now measure the distance between the points of the scissor blades. This is the two-point threshold. Repeat this procedure for different parts of your body (e.g., finger, palm, neck, back, foot, thigh). Record your measurements of the two-point thresholds for each body part.

Thinking carefully about what you have learned about the brain in this experiment, write up your results and try to explain them. (Note: You do not need to know anything about touch sensation to write this essay.) Be sure to address the following questions:

Does the two-point threshold differ across your body? Report your actual measurements of the two-point threshold and use those measurements as the basis of your discussion. Given what you know about the brain, why might the differences that you found exist?

Imagine that you had suffered damage to some specific part of your cerebral cortex. Would your ability to detect touches on your skin be impaired? Might this depend on which part(s) of your cortex had been damaged? Explain.

Why do you think certain body parts might be "overrepresented" in the human cortex? (Hint: One way to think about this question is to consider why having certain parts of the body be overrepresented in the brain might be adaptive? What in human experience could have lead those parts to be overrepresented?)

Explanation / Answer

The Two - point threshold differs across the body. The difference exists because of the different amount of cortex dedicated to a body surface. More the cortex dedicated to the body surface more will be the sensitivity of that region. From the data collected by you it will be seen that two - point threshold is smaller on the thumb than the forearm.

The area of the sensory cortex devoted to the thumb is the same size as the one devoted to the entire forearm.This leads to finer detailed information for the finger.The finger tips have more nerves going to the sensitive area of the brain. The area of the brain which receives information from sensitive areas have greater density of nerves.. It follows therefore that any damage to some specific part of the cerebral cortex will definetely impair the ability to detect touch on the skin. This will depend on which part of the cortex is impaired.

The receptors in the skin when stimulated, the nerve cell ending generate action potential. This travels to the central nervous system and via cross axon reach the other side of the brain. If the cortex is damaged the information cannot be processed.

Certain body parts may be overrepresented because fine touch information from these parts are important. This is a result of adaptation. The very act of survival could have lead to these adaptation. The finger tips are the most sensitive to pain and survival depended on adaptation.

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