Hockenbury Discovering Psychology 5th txtbk

112 CHAPTER 3 Sensation and Perceptionkinesthetic sense(kin-ess-THET-ick) The technical name forthe sense of location and position of bodyparts in relation to one another.proprioceptors(pro-pree-oh-SEP-ters) Sensory receptors,located in the muscles and joints, thatprovide information about body positionand movement.vestibular sense(vess-TIB-you-ler) The technical name for thesense of balance, or equilibrium.bottom-up processingInformation processing that emphasizes theimportance of the sensory receptors indetecting the basic features of a stimulus inthe process of recognizing a whole pattern;analysis that moves from the parts to thewhole; also called data-driven processing.top-down processingInformation processing that emphasizes theimportance of the observer’s knowledge,expectations, and other cognitive processesin arriving at meaningful perceptions; analysisthat moves from the whole to the parts;also called conceptually driven processing.As the pain circuits undergo sensitization, pain begins to occur in the absence of anysensory input. The result can be the development of persistent, chronic pain that continuesafter all indications are that the injury has healed (see Scholz & Woolf, 2002).In the case of phantom limb pain, sensitization has occurred in the pain transmissionpathways from the site of the amputation. The sensitized pathways produce painful sensationsthat mentally feel as though they are coming from a limb that is no longer there.Movement, Position, and BalanceThe phone rings. Without looking up from your textbook, you reach for thereceiver, pick it up, and guide it to the side of your head. You have just demonstratedyour kinesthetic sense—the sense that involves the location and position of body partsin relation to one another. (The word kinesthetics literally means “feelings of motion.”)The kinesthetic sense involves specialized sensory neurons, called proprioceptors,which are located in the muscles and joints. The proprioceptors constantly communicateinformation to the brain about changes in body position and muscle tension.Closely related to the kinesthetic sense is the vestibular sense, which provides asense of balance, or equilibrium, by responding to changes in gravity, motion, andbody position. The two sources of vestibular sensory information, the semicircularcanals and the vestibular sacs, are both located in the ear (see Figure 3.12). Thesestructures are filled with fluid and lined with hairlike receptor cells that shift inresponse to motion, changes in body position, or changes in gravity.When you experience environmental motion, like the rocking of a boat in choppywater, the fluids in the semicircular canals and the vestibular sacs are affected.Changes in your body’s position, such as falling backward in a heroic attempt toreturn a volleyball serve, also affect the fluids. Your vestibular sense supplies the criticalinformation that allows you to compensate for such changes and quicklyreestablish your sense of balance.Maintaining equilibrium also involves information from other senses, particularlyvision. Under normal circumstances, this works to our advantage. However, wheninformation from the eyes conflicts with information from the vestibular system, theresult can be dizziness, disorientation, and nausea. These are the symptoms commonlyexperienced in motion sickness, the bane of many travelers in cars, on planes,on boats, and even in space. One strategy that can be used to combat motion sicknessis to minimize sensory conflicts by focusing on a distant point or an object thatis fixed, such as the horizon.In the first part of this chapter, we’ve described how the body’s senses respond tostimuli in the environment. Table 3.4 summarizes these different sensory systems. Tomake use of this raw sensory data, the brain must organize and interpret the data andrelate them to existing knowledge. Next, we’ll look at the process of perception—how we make sense out of the information that we receive from our environment.Figure 3.12 TheVestibular Sense Thevestibular sense providesour sense of balance, orequilibrium. Shown hereare the two sources ofvestibular sensory information,both located inthe ear: the semicircularcanals and the vestibularsacs. Both structures arefilled with fluids thatshift in response tochanges in body position,gravity, or motion.SemicircularcanalsVestibularsacs