Somatosensory Discrimination

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Differences in Somatosensory Discrimination of Two-Points across the Body
Christina Caviasco
Fordham University
November 9, 2015 Christina Caviasco
November 9, 2015
PSYC 1100 – R04
Differences in Somatosensory Discrimination of Two-Points across the Body In order for a somatosensation to be perceived, the stimulus must transmit information from the periphery at the site of stimulation to the central nervous system. Sensory receptors located in the human skin respond to a variety of different stimuli, including touch, pressure, heat, cold, and pain through mechanoreceptors, chemoreceptors, and thermoreceptors. Sensitivity to movement of the skin mechanically moves dendrites of specialized mechanoreceptors. This creates an electrical …show more content…
Cortical regions of the brain, however, are disproportionate to the surface area of skin. Rather the area of the brain devoted to receiving input on different areas of skin is based on the density of receptors in that area (Hermann, 1996). Previous studies have proved discrepancies in different skin regions due to the localization of tactile stimuli receptors (Stevens, 1995 & Johnson, 1981). To represent this phenomenon, a distorted figurine called a homunculus is often used, depicting regions of the skin with more dense sensory receptors as enlarged body parts. On these diagrams, hands, feet, face, and lips are disproportionately larger than the remainder of the body (Linkenauger, 2015). In this commonly performed experiment, the sense of touch was tested by a two-point discrimination test. It is performed to assess a patient’s ability to perceive two, closely positioned stimuli presented simultaneously. Based on what is known about the location of receptors in the skin, it was hypothesized that less distance will be needed …show more content…
Two-point discrimination of each participant was tested while his or her eyes were closed. The two-point discrimination device, the unwound paperclip, was gently pressed by another group member on the skin of the participant with the two points growing increasingly further apart until the participant was able to perceive two points versus only one point. The participant indicated their perception of either one or two points by reporting this aloud to the other members of the group. The group member administering the two-point discrimination ensured that both of the two points were placed on the skin simultaneously with not too much force. This was tested on the skin of the cheek, forearm, palm of hand, tip of thumb, tip of index finger, and lower leg of each participant. The other group member recorded the minimum distance between the two points before the participant was able to discern two distinct points. At the end of the experiment, the groups self-reported the raw data, and the data of the entire class was compiled to calculate the mean minimum distances in millimeters for each of the different body parts

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