It can be useful for students to be able to put these parts together in a way that would represent a human. The sensory homunculus in humans has a very large face, tongue and fingertips, therefore the student drawings will have large faces, tongues and fingertips. Each hemisphere of the cortex receives information from the opposite side of the body. The maps in animals and humans have been made by tactile stimulation of the skin and recording of the resultant electrical activity in the neurons of the sensory cortex. Facsimiles of these maps can be made in the classroom by using two point-discrimination to find the relative density of touch receptors in the skin.
Maps are available for a number of mammals, including humans, rats, rabbits and cats.
The materials used in two-point discrimination are normal school materials but students should always be aware that everyday materials must be used carefully for personal safety. Points should be discarded or disinfected before using on another person. In a prelab situation, demonstrate to the students a method of two-point discrimination on the skin. Gently touch two slightly pointed objects to the skin of your forearm. It is important to apply these at the same time and to have the subject looking away from the test site.