The Nonvisual Senses

1. The Nonvisual Senses • Fig. 19.1 The physical properties of waves. • Memorize sound to nerve impulses(m259 f19.2 c245 f6.35) • The outer ears funnels sound waves to the eardrum. • The bones of the middle ear amplify and relay the ear-drum's vibrations through the oval window into the fluid-filled cochlea. • The resulting pressure changes in the cochlear fluid cause the basilar membrane to ripple, bending the hair cells on its surface. • Hair cell movements trigger impulses at the base of the nerve cells, whose approx. 30,000 fibres converge to form the auditory nerve. • Fig. 19.3 We evolved in a much quieter world.

2. The Nonvisual Senses • Nerve deafness can be partially restored with a cochlear impant. • The device translates sounds into electrical signals that, wired into the cochlear nerves, convey information about sound to the brain. • Klinke 1999 (m260 c246): Cochlear implants given to deaf kittens and human infants seem to trigger an awakening of the pertinent brain areas. • If installed as preschoolers, users can become proficients in oral communication. • The implants in adults will not enable normal hearing if their brain never learned to process sound during childhood.

3. The Nonvisual Senses • Loudness is perceived by the number of cochlear hair cells that are stimluted. • Pitch is perceived as a combination: • Place theory links pitch with the location of stimulation of the cochlear membrane. • Frequency theory: the rate of nerve impulses travelling up the auditory nerve matches the frequency of the tone. • Volley principle: Neural cells can alternate firing. By firing in rapid succession, they can achieve a combined frequency above 1000 Herze (waves / second). • Volley for high pitch, frequency for low pitch, and a combination for middle pitches. • The just noticeable difference for two sound sources is .000027 seconds.

4. The Nonvisual Senses • Touch: We have basically four senses of touch: pressure, warmth, cold, and pain. • There is no one type of receptor that triggers pain. Instead there are different nociceptor --sensory receptors the detect hurtful temperatures, pressure and certain chemicals. (m 264 f19.6 c250 f2.39) • Wall, 1965. Gate-control theory: The spinal cord contains small nerve fibres that conduct most pain signals, and larger fibres that conduct most other sensory signals. • When tissue is injured, the small fibres activate, you feel pain. Large fibre activity (such as massage) closes the gate. • Zubieta, 2003: A gene that boosts the availability of endorphins can make the brain less responsive to pain (m264 c250).

5. The Nonvisual Senses • Phantom limb sensations: where the brain misinterprets spontaneous central nervous system activity, such as sending a right thumb protruding out of your upper lip. • Tinnitus: A ringing-in-the-ears due to cochlea damage. • Non-threatening hallucinations as a side effect of glaucoma, cataracts, diabetes or macular degeneration (death of cells in the fovea). • Psychological influences: Kahneman, 1999: we prefer longer trials, with more overall pain, but less pain at the end; this is the 'taper off' effect (m265 c251). • Social-Cultural influences: Symbaluk 1997: We perceive more pain if others around us do(m265 c251). • Fig. 19.7

6. The Nonvisual Senses • Controlling Pain: The placebo effect. Scott, 2007. Fake pain-killing chemicals cause brain to activate an area that releases pain-killing endorphins. • Kaptchuk 2006: Fake acupunture does the same thing, all the way to side effects. • Edward, 2009. Distraction (dissociation) counting backward by 3s. • Virtual reality works even better, immersion in a 3d world reduces the brain's pain-related activities. • Fig. 19.8

7. The Nonvisual Senses • Taste. We have five basic taste sensations, based on receptors on our tongues. Table 19.1 • A very quick taste will alter the temporal lobe of your brain. Kelling & Halpern, 1983(m267 c253). • Plassmann, 2008: Being told that a wine costs $90 rather than its real price of $10 made it taste better and triggered more activity in the brain area that responds to pleasant sensations. • Embodied cognition. Figure 19.9 When hard-of-hearing listeners see an animated face forming the words being spoken at the other end of the phone line, the words become easier to understand. • Kayser, 2007. A weak flicker of light that is barely perceptible beomes more visible when accompanied by a short burst of sound (m268 c254).

8. The Nonvisual Senses • Smell: (m269 f19.10 c255 f6.43) • Miller, 2004, Buck & Axel 1991: There are 350 receptor proteins that recognize particular odor molecules. This is the 'key-and-lock' model of smell (m270 c256). • The combination of olfactory receptors, activating different neural patterns, that allow fine distinctions. • Herz, 2001. The attractiveness of smells depends on learned associations. • Fig. 19.12 Information from the taste buds travels to an area between the frontal and temporal lobes, registering in an area not far from the sense of smell area, which interacts with taste. • The brain's smell circuitry interacts with memory storage.

9. The Nonvisual Senses • Kinesthesis is the sense of body position and movement. • Vestibular sense monitors your head and body position and movement. • Anatomically, this is the semicircular canals, and the vestibular sacs. • Messages are sent to the cerebellum, enabling you to consciously sense movement and maintain balance. • For the next exam: summarizing the senses (m272 t19.2 c258 t6.3)