Chapter 7

1. Chapter 7 Auditionand Pain

2. Audition • The Stimulus • Pitch • A perceptual dimension of sound; corresponds to the fundamental frequency of the stimulus. • Hertz • Cycles per second. • Loudness • A perceptual dimension of sound; corresponds to the intensity of the stimulus. • Timbre • A perceptual dimension of sound; corresponds to the complexity.

3. Figure 7.2 Physical and Perceptual Dimensions of Sound Waves

4. Anatomy of the Ear • Tympanic membrane • The eardrum; vibrates when stimulated by sound waves. • Ossicles • The bones of the middle ear. • Malleus • The first of the three ossicles; attached to the tympanic membrane. • Incus • Located between the malleus and the stapes. • Stapes • The third ossicle; attached to the oval window of the cochlea.

5. Anatomy of the Ear • Cochlea • The snail-shaped, fluid-filled, bony structure of the inner ear; contains the basilar membrane and the auditory receptor hair cells. • Oval window • An opening in the bone of the cochlea that reveals a membrane, against which the baseplate of the stapes presses, transmitting sound vibrations into the fluid within the cochlea.

6. Figure 7.3 The Auditory Anatomy

7. Figure 7.4 The Cochlea. A cross section through the cochlea, showing the organ of Corti.

8. Figure 7.5 Responses to Sound Waves. When the stapes pushes against the membrane behind the oval window, the membrane behind the round window bulges outward. Different high-frequency and medium-frequency sound vibrations cause flexing of different portions of the basilar membrane. In contrast, low-frequency sound vibrations cause the tip of the basilar membrane to flex in synchrony with the vibrations.

9. Figure 7.6 Transduction Apparatus in Hair Cells. These electron micrographs are of the transduction apparatus in hair cells: (a) a longitudinal section through three adjacent cilia. Tip links, elastic filaments attached to insertional plaques, link adjacent cilia. (b) A cross section through several cilia, showing an insertional plaque.

10. The Auditory Pathway • Cochlear nerve • A branch of the eighth cranial nerve; the branch of the auditory nerve that transmits auditory information from the cochlea to the brain. • Cochlear nucleus • One of a group of nuclei in the medulla that receive auditory information from the cochlea. • Superior olivarycomplex • A group of nuclei in the medulla; involved with auditory functions, including localization of the sound source. • Lateral lemniscus • A band of fibers running rostrally through the medulla and pons; carries fibers of the auditory system.

11. Figure 7.7 Pathways of the Auditory System. The major pathways are indicated by heavy arrows.

12. Perception of Spatial Location • Humans can determine the location of a sound because auditory neurons respond selectively to different arrival times of the sound waves at the left and right ears. • Phase difference • The difference in arrival times of sound waves at each of the eardrums.

13. Figure 7.12 Sound Localization. This method localizes the source of low-frequency and medium-frequency sounds through phase differences. (a) Source of a 1000-Hz tone to the right. The pressure waves on each eardrum are out of phase; one eardrum is pushed in while the other is pushed out. (b) Source of a sound directly in front. The vibrations of the eardrums are synchronized (in phase).

14. Perception of Complex Sounds • Hearing has three primary functions: to detect sounds, to determine the location of their sources, and to recognize the identity of these sources—and thus their meaning and relevance to us. • The task of the auditory system in identifying sound sources, then, is one of pattern recognition. The auditory system must recognize that particular patterns of constantly changing activity belong to different sound sources.

15. Figure 7.14 “Where” Versus “What.” This figure shows regional brain activity in response to judgments of category (blue) and location (red) of sounds. IFG = inferior frontal gyrus, IPL = inferior parietal lobule, MFG = middle frontal gyrus, SFG = superior frontal gyrus, SPL = superior parietal lobule.

16. Pain Pain appears to have three different perceptual and behavioral effects. First is the sensory component—the pure perception of the intensity of a painful stimulus. The second component is the immediate emotional consequences of pain—the unpleasantness or degree to which the individual is bothered by the painful stimulus. The third component is the long-term emotional implications of chronic pain—the threat that such pain represents to one’s future comfort and well-being.

17. Perception of Pain These three components of pain appear to involve different brain mechanisms. The purely sensory component of pain is mediated by a pathway from the spinal cord to the ventral posterolateral thalamus to the primary and secondary somatosensory cortex. The immediate emotional component of pain appears to be mediated by pathways that reach the anterior cingulate cortex (ACC) and insular cortex. The long-term emotional component appears to be mediated by pathways that reach the prefrontal cortex.

18. Figure 7.20 The Three Components of Pain. A simplified, schematic diagram shows the brain mechanisms involved in the three components of pain: the sensory component, the immediate emotional component, and the long-term emotional component.

19. Figure 7.21 Sensory and Emotional Components of Pain. The PET scans show regions of the brain that respond to sensory and emotional components of pain. Top: Dorsal views of the brain. Activation of the primary somatosensory cortex (circled in red) by a painful stimulus was not affected by a hypnotically suggested reduction in unpleasantness of a painful stimulus, indicating that this region responded to the sensory component of pain. Bottom: Midsagittal views of the brain. The anterior cingulate cortex (circled in red) showed much less activation when the unpleasantness of the painful stimulus was reduced by hypnotic suggestion.