2. Chapter 4 Sensation

3. What Do Sensory Illusions Demonstrate? Streams of information coming from different senses can interact. Experience can change the sensations we receive. “Reality” differs from person to person. –Our sensory systems create our personal reality.

4. Figure 4.1: Elements of a Sensory System

5. The Problem of Coding How are physical properties coded into neural activity? Doctrine of Specific Nerve Energies Types of codes –Temporal –Spatial

6. Linkages: Sensation and Biological Aspects of Psychology Organized sensory information is called a representation. Shared features of representations of vision, hearing, and skin senses: –Information from each sense reaches the cortex via the thalamus. –Representation of world is contralateral to the part of the world being sensed.

7. Linkages: Sensation and Biological Aspects of Psychology (cont’d) Shared features (cont’d.): –The cortex contains topographical representations of each sense. –The density of nerve fibers in a sense organ determines how well it is represented in the cortex. –Each region of primary sensory cortex is divided into columns of cells that have similar properties. –Regions of cortex other than the primary areas do additional processing of sensory information.

8. Sound A repeated fluctuation in the pressure of air, water, or some other substance. –Produced by vibrations of an object Wave: Repeated variation in pressure that spreads out in three dimensions.

9. Continue Physical Characteristics of Sound A waveform represents a wave in two- dimensions.A waveform represents a wave in two- dimensions. Characteristics of Waveforms –Amplitude –Wavelength –Frequency

10. Return Figure 4.2: Sound Waves and Waveforms

11. Psychological Dimensions of Sound Loudness Pitch Timbre

12. Figure 4.3: Structures of the Ear

13. Conduction Deafness The three tiny bones of the middle ear are fused together. Prevents accurate reproduction of vibrations. Surgery can break bones apart or replace them with plastic ones. Hearing aids can also help.

14. Nerve Deafness Results when the auditory nerve or the hair cells are damaged. Can be caused by extended exposure to loud noise. Cochlear implants can stimulate the auditory nerve. Hair cell regeneration as a possible treatment.

15. Auditory Pathways Auditory nerve  brainstem  thalamus Various aspects of sound processed in different regions of auditory system Certain parts of auditory cortex process certain types of sounds

16. Sensing Pitch Different people may experience the “same” sound as different pitches. Pitch-recognition abilities influenced by genetics. –Cultural factors are also partly responsible for the way in which a pitch is sensed.

17. Locating Sounds Determined partly by the very slight difference when sound arrives at each ear. The brain also uses information about the difference in sound intensity at each ear.

18. Coding Intensity and Frequency The more intense the sound, the more rapid the firing of a given neuron. Frequency appears to be coded in two ways.

19. Coding Frequency: Place Theory Sounds produce waves that move down the basilar membrane. –Where the wave peaks depends on the frequency of the sound. Hair cells at a particular place on the membrane respond most to a particular frequency. But how are very low frequencies coded?

20. Coding Frequency: Frequency Matching Theory Firing rate of an auditory nerve matches a sound wave’s frequency. Sometimes called the volley theory of frequency coding.

21. The Ear and Sound Waves: Part I

22. The Ear and Sound Waves: Part 2