In the first experiment, the experimenter rubbed our index fingers across very rough sandpaper for five seconds. The experimenter rated its coarseness as 5 on a scale of 1 (very soft) to 7 (very coarse). After one minute, the experimenter rubbed the same finger across the same paper and rated it again for 4. Our rating dropped one point between trials. The experimenter observed that our perception of the paper's coarseness change from the first to the second rubs. The sensitivity to coarseness changed over time demonstrating neural adaptation. The sensory system involved in this experiment is the somatosensory (Flanagan & Lederman, 2001). It is the sense that includes perceptions of pressure, temperature, and pain (Flanagan & Lederman, 2001). This system identifies stimuli from sensory receptors, and the sensory signal is sent to the central nervous system where it is processed in the brain (Flanagan & Lederman, 2001).
The next experiment reinforces the idea of adaptation in the somatosensory system. The experimenter filled three containers with water: one with hot, another with warm, and the third with cold. He placed his right hand in the hot water and left in the cold simultaneously and waited 3 minutes. Then, he places both hands in the warm bowl simultaneously. What he felt was coolness on the hand that was in the hot water and warmness on the hand that was in the cold. This is also demonstration of sensory adaptation in that the somatosensory system acclimated to the temperatures of the first two containers, and the sensory difference was felt in the third.
The somatosensory system is made up of receptor cells and electrochemical processes along a neural pathway that usually includes three long nerve cells (Boulpaep & Boron, 2003). The first neuron usually starts in the dorsal root ganglion of the chord (Boulpaep & Boron, 2003). The second neuron is usually in the spinal cord or the brainstem (Boulpaep & Boron, 2003). Their axons will tracers to the opposite side of the system (Boulpaep & Boron, 2003). Most of the axons end in the thalamus while others end in the reticulum or the cerebellum (Boulpaep & Boron, 2003). With touch, the third neuron ends up in the parietal lobe (Boulpaep & Boron, 2003). Some axons end up in the cerebellum (Boulpaep & Boron, 2003). The main somatosensory area in the cerebral cortex is in the postcentral gyrus of the parietal lobe. The postcentral gyrus is the main sensory receiver for of touch (Boulpaep & Boron, 2003). The map of sensory space here is called the sensory homunculus (Boulpaep & Boron, 2003). This area of the human brain refers to particular areas of the body (Boulpaep & Boron, 2003). Information about posture is processed in the cerebellum (Boulpaep & Boron, 2003).
In the last experiment, the experimenter set up two cups; one with sugar water, the other with fresh water. The experimenter sipped the sugar water first and swished it for several seconds. Over time, it began tasting less sweet. Next, the experimenter sipped the fresh water, and to our surprise, it tasted somewhat sweet. Taste is a kind of chemoreception (Smith & Margolskee, 2001). It is capability to sense flavor (Schiffman, 2000). In many species taste partners is coupled with smell in the brain (Smith & Margolskee, 2001). Traditional tastes include sweet, salty, sour, and bitter (Schiffman, 2000