Psych 102 Chapter 9 Presentation
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7/23/19 Hearing and Language Chapter 9 Stimulus for Hearing The Auditory Mechanism Frequency Analysis Garrett: Brain & Behavior 4e Locating sounds with Binaural Cues Language, Aphasias, and Antecedents 1 Hearing • A *receptor is a cell or specialized neuron that • Responds to a particular form of energy 7/23/19 (adequate stimulus). • *converts one form of energy to another • Intensity and pattern of information makes information meaningful. • “Hearing” vs. “ listening” • *Sensation- acquisition of information Garrett: Brain & Behavior 4e • *Perception- interpretation of information 2 Hearing Where Sensation Occurs and What is Encoded Where Physical stimulus is Psychological 7/23/19 Sense Adequate Stimulus modalities converted modalities (receptor) Hearing Vibration in a Cochlea • Frequency • Pitch (Ch 9) conducting medium (hair cell) • Intensity or • Loudness (air, water, bone) Amplitude Vision Electromagnetic Retina • Wavelengt • Color (Ch 10) radiation in visual (rod , cone) h • Brightness spectrum • Intensity or wavelengths Amplitude Garrett: Brain & Behavior 4e 3 Physical vs. Psychological • *Amplitude (or • *Loudness 7/23/19 Intensity) • dB- decibels • mV- millivolts • 6dB corresponds to doubling of amplitude • Peak-to-peak • *Frequency • *Pitch • Hz- hertz • Waves per second • Human hearing range: Garrett: Brain & Behavior 4e *20Hz – 20,000 Hz 4 Hearing Fig 9.2: Alternating Compression & Decompression of Air by a Sound Source Fig 9.3: Examples of Pure Tones (a-d) and Complex (e-f) Sounds (right) 7/23/19 Garrett: Brain & Behavior 4e 5 SOURCE: (LEFT) From Sensation and Perception, 5th ed., by Goldstein, 1999. Reprinted with permission of Wadsworth, a division of Thomson Learning. Hearing Figure 9.4: The Outer, Middle, and Inner Ear 7/23/19 Garrett: Brain & Behavior 4e Oval window Round window Eustachian tube 6 Hearing Figure 9.4: The Outer, Middle, and Inner Ear • Outer ear 7/23/19 • Pinna • External auditory canal Garrett: Brain & Behavior 4e 7 Hearing Figure 9.5: Structures of the Middle and Inner Ear. • Middle ear 7/23/19 • Tympanic membrane • Tensor tympani • *Ossicles • hammer, anvil, stirrup • amplify sound from the tympanic membrane to the oval window Garrett: Brain & Behavior 4e • Eustachian tube Stirrup 8 Hearing Figure 9.5: Structures of the Middle and Inner Ear • Inner ear 7/23/19 • Oval window • Cochlea (Inner Ear) • Vestibular canal • Cochlear canal • Organ of Corti • Tympanic canal • Round window • Auditory nerve Garrett: Brain & Behavior 4e 9 Hearing See Figure 9.6: Electron Microscope view Showing the Hair Cells Attached to the Tectorial Membrane • *Organ of Corti – The receptive Organ of the ear 7/23/19 • Tectorial membrane • *Hair cells – The actual auditory receptors themselves • *Outer hair cells -> (amplification and sound sharpening) • Inner hair cells (encode sound into impulses) Garrett: Brain & Behavior 4e • Basilar membrane 10 Hearing The Auditory Cortex. Figure 9.7: The Auditory Pathway and Auditory Cortex • Auditory (8th Cranial Nerve) > • Inferior colliculi (sound from both ears converge) > 7/23/19 • Medial geniculate nucleus (mostly opposite ear information) > • Primary auditory cortex *(temporal lobe) • Topographical organization throughout system Garrett: Brain & Behavior 4e 11 Hearing Fig 9.8: The Dorsal “Where” & Ventral “What” Streams of Auditory Processing • What (green) • *Ventral Stream into temporal lobes 7/23/19 • Secondary Auditory Cortical areas • Where (red) • *Dorsal stream to parietal lobes, then frontal lobes Garrett: Brain & Behavior 4e 12 Hearing Frequency Theories. Figure 9.9: Illustration of Volleying in Neurons • Frequency theory (Rutherford, 1886) • Telephone theory (Wever & Bray, 1930) 7/23/19 • Both of above limited to <500 Hz sounds. Why? • Volley theory (Wever, 1949) • Volleying fails to follow sounds beyond about 5200 Hz • *groups of neurons follow frequency up to this point though Garrett: Brain & Behavior 4e 13 Hearing Why Frequency Theories are Inadequate • Why can’t we use frequency theories for encoding high frequency signals? • 1000 Hz is 1000 waves per second, • 1 millisecond between action potentials • Well below absolute refractory period of individual neuron +20 mV 0 mV -20 mV Absolute -40 mV 14 Threshold (mV) Refractory Period Relative Refractory Period 00 21 42 63 84 ms Time between action potentials (ms) Hearing Place Theory. Figure 9.10: Frequency Sensitivity on the Human Basilar Membrane. • *Place Theory • Tonotopic map of basilar membrane • *Frequencies encoded by place on membrane Garrett: Brain & Behavior 4e 15 SOURCE: Animation © 2006 Howard Hughes Medical Institute Hearing Place Theory. Figure 9.11: Tonotopic Map Figure 9.12: “ Tuning Curves” of three Cat Auditory Neurons • Auditory cortex is also *tonotopically organized • Cells tightly tuned to specific frequencies Garrett: Brain & Behavior 4e 16 SOURCE: (Bottom) Figure 11.31 from Sensation and Perceptions (5th ed.; p. 331) by E. Bruce Goldstein, 1999, Pacific Grove, CA: Brooks-Cole. © 1999. Reprinted by permission of Wadsworth, a division of Thomson Learning: www.thomsonrights.com. Fax 800-730-2215. Hearing Summary of Frequency vs. Place Theory • Hair cells fire at same • Basilar membrane frequency as sound sensitive to different wave frequencies • Volley: combining • Tonotopic frequency several hair cells organization • Low frequency • High frequency • Pitch- impulse rate of • Pitch- membrane hair cells location • Loudness- number of • Loudness- firing rate firing hair cells of hair cell 17 Hearing • However, place theory alone is inadequate. 7/23/19 • Basilar membrane vibrates equally throughout low range of hearing • Frequency-specific neurons have not been found below 200 Hz. • Frequency-place theory • Frequency encoding at low frequencies (most < 500 Hz) • Place encoding for everything else Frequency Theories Garrett: Brain & Behavior 4e Place Theory 18 0 1 2 3 4 5+ kHz Hearing Analyzing Complex Sounds. Figure 9.14: Fourier analysis of a clarinet note • Analyzing Complex Sounds 7/23/19 • Fourier analysis • Breaking complex sound into component frequencies • Basal membrane Garrett: Brain & Behavior 4e 19 SOURCE: From “How Much Distraction Can You Hear?” by P. Milner, Stereo Review, June 1977, pp. 64–68. © 1977. Reprinted by permission of Stereo Review. Hearing Analyzing Complex Sounds Figure 9.15: Areas Involved in Identifying Environmental Sounds • Analyzing Complex Sounds 7/23/19 • Cocktail party effect • Following an auditory object within complex sound background • Selective attention requires directional information as well as “what” pathway (yellow areas below) Garrett: Brain & Behavior 4e 20 SOURCE: From “Human Brain Regions involved in Recognizing Environmental Sounds,” by J. W. Lewis et al., 2004, Cerebral Cortex, 14, 1008–1021. Reprinted with permission. Hearing Locating Sounds With Binaural Cues Figure 9.16: Sound Localizing Device Used by 19th-Century Sailors. • Binaural: using both ears • Differences –*Greatest with sounds to our left & right • Difference in Intensity • Difference in Time of Arrival • Phase Difference Garrett: Brain & Behavior 4e 21 Hearing Locating Sounds With Binaural Cues Figure 9.17: Differential Intensity & Time of Arrival Cues • Difference in 7/23/19 Intensity • High frequencies • Sound shadow • Difference in Time of Arrival • Low frequencies • Sound delay Garrett: Brain & Behavior 4e 22 Hearing Figure 9.18: Phase Differences at the Two Ears • Phase difference between ears 7/23/19 • The far ear’s wave will lag behind the nearer one • Only useful < 1500 Hz Garrett: Brain & Behavior 4e 23 Application: Restoring Hearing *Hearing aids useful for losses associated with middle ear bone conduction issues *A Cochlear Implant Device for problems with hair cells Garrett: Brain & Behavior 4e 24 Stimulates hair cells directly through implanted receiver/stimulator Quality is about the same as a telephone call Hearing A Brain Circuit for Detecting Time Differences Figure 9.19: Difference in Time of Arrival Circuit • Coincidence detectors and delay lines 7/23/19 • Longer pathway from one ear compensates for sound delay to the other ear. • Cell fires most when inputs from both ears arrive at the same time. • Each detector is specialized for a particular angle of sound. Garrett: Brain & Behavior 4e 25 SOURCE: Based on the results of Carr and Konishi (1990). Hearing Application: I Can Hear a Tree Over There • Echolocation • Emit sound, echoes coming off objects are “seen” • Bats, dolphins, whales, some birds, submarines • Occasionally a blind human! Garrett: Brain & Behavior 4e 26 SOURCE: From Figure 3, Thaler, L., Arnott, S. R., Goodale, M. A. (2011). Neural correlates of natural human echolocation in early and late blind echolocation experts. PLoS ONE, 6, e20162, DOI: 10.1371/journal.pone.0020162. Figure was edited to highlight only the later views of Participant EB and control Participant C1 Language Defined • Language: generation and understanding of written, spoken, and gestural communication. 7/23/19 • Acquired through learning • Brain areas responsible for language • Impairment- Aphasia Garrett: Brain & Behavior 4e 27 Language Broca’s Area. Figure 9.20: Language-Related Areas of the Cortex • Broca (1861): Stroke patient with *frontal lobe damage anterior to motor cortex (Broca’s area) 7/23/19 • Broca’s (Expressive) Aphasia • *Non-fluency (selecting the right word) • Anomia • *Inarticulate (pronunciation) • Agrammatic 28 Language Wernicke’s Area. Figure 9.20: Language-Related Areas of the Cortex • Wernicke (1874): Left *Posterior superior temporal lobe damage