Audition
Instructor: J. R. Ison
167 Meliora, x5-8461
e-mail ison@bcs.rochester.edu
The course should be interesting to students who would like the opportunity to explore the strengths and weaknesses of an area of neuroscience in which understanding the physiological substrate responsible for an important psychological function is relatively well advanced, for those interested in the receptive aspects of speech and language, and for those who wish to learn about the professional careers concerned with hearing impairment and deafness. The class meetings will consist largely of lectures and discussion, with some student presentations from the literature. My intent in lectures and discussion will be describe the theoretical and empirical data directly appropriate to the current topic, but always to place the material in the broader context by introducing relevant material that to be taken up in greater detail at a later time in the course.
The assignments for the course are two brief research/review papers (3-ish pages) and three in- class quizzes. The topic for the paper should be chosen at the end of September and October and the paper handed in 2 weeks later. The quizzes will be given in the first week of October, November, and December. Each paper should include a discussion of several publications in the primary literature on a topic of interest to you, and one will form the basis of a class presentation. The course can be taken for upper-level writing on request.
Overview of the course:
I: Introductory principles
A: Physiology
Reading -- the introductory chapters in any recent biopsychology text
Anatomy and physiology
Cells and their connections
receptors, projection neurons and interneurons
membrane potentials, receptor potentials, and action potentials
excitation and inhibition
neurotransmitters
brain regions
filters and their characteristics: bandwidth and temporal tradeoffs (receptors as filters) Fourier analysis: analysis and synthesis of complex wave forms (Fourier analysis done by the ear; linear system analysis, and the rationale for using simple tonal stimuli in sensory experiments).
III: Anatomy and physiology (for primer see Moore, pp 15 to 46)
A. Structure and function of the outer and middle ears (see Chapter 2 in Pickles and Gardner & Gardner 1973) and effect of pinna in humans; impedance matching in the middle ear; transfer functions of outer and middle ear in humans -- relation to human audiogram (see pp. 47 - 50 in Moore). Protective role of the middle ear reflex for hearing, and in "homeostasis". Sources of hearing impairment at this level of the auditory system. Differences in the outer and inner ear across species, and their functional significance.
B. Structure and function in the cochlea (Chapter 3 in Pickles) General structural details of Organ of Corti; Basilar membrane and stria vascularis; chemical structure of endolymph and perilymph; haircells as acoustic filters, and their innervation patterns; Differences in function of inner and outer haircells; olivocochlear bundle; movement of the basilar membrane and the traveling wave; frequency relationships along the basilar membrane. Motility of outer hair cells. Cellular bioelectrical potentials in hair cells. Cochlear potentials and cochlear emissions. Sources of hearing impairment at this level of the auditory system (Chapter 10 Pickles). Recovery of structure and function in birds and reptiles.
C: The Auditory Nerve (Chapter 4 in Pickles) Structural composition of auditory nerve. Physiological characteristics -- best frequencies, tuning curves, rate intensity functions, phase locking. Lack of inhibition, but presence of suppression, in the auditory nerve. Masking phenomena. Sources of hearing impairment at this level of the auditory system.
D: The auditory brainstem (Chapter 6 in Pickles) Ascending influences: Anatomy and physiology in the cochlear nucleus; the superior olivary complex, the inferior colliculus, and the medial geniculate. Tonotopic organization; Primary projection areas and "processing" areas; excitatory and inhibitory interneurons and their effects; binaural responses and investigations of neurotransmitters.
E: Auditory cortex (Chapter 7 in Pickles) General anatomy; tonotopic organization; response types and feature detectors. Sources of hearing impairment at this level of the auditory system: localization; auditory patterns; and speech perception.
F: Downstream mechanisms and their effects (Chapter 8 in Pickles) Anatomy and physiology of the olivocochlear bundle; effects of olivocochlear bundle stimulation on evoked potentials in animals and humans effects of olivocochlear bundle destruction on hearing in humans -- "selective attention."
IV: Sensory and Perceptual Phenomena of Audition (For primer see Pickles Chapter 9)
A: Loudness (Chapter 2 in Moore) Loudness and intensity; Absolute and Differential Thresholds; adaptation and fatigue; Pathologies of loudness perception -- recruitment. How is loudness coded in the nervous system?
B: Frequency selectivity (Chapter 3 in Moore) The critical band, and its relation to masking, frequency selectivity and to loudness judgments. Psychophysical tuning curves. Methods for investigating the critical band; masking and release from masking. Hearing impairment and frequency selectivity.
C: Pitch perception (Chapter 5 in Moore) Pitch and frequency; theories of pitch perception -- timing vs place; duplex theory and certain complexities; The "missing fundamental." "Perfect pitch" and the brain. What happens to musical perception and in the auditory nerve above C8 on the piano?
D: Temporal resolution (Chapter 4 in Moore) The importance of variation in the envelope of the acoustic signal over time; gap detection and amplitude modulation; relationship to speech perception -- temporal acuity and dyslexia; engineering models of temporal acuity.
E: Sound localization (Chapter 6 in Moore) Simple "duplex" theory for azimuth localization -- time and intensity cues; The importance of transients and the envelope of the signal; head movements and "sculpting" the signal by the pinna. The precedence effect and echo suppression; Neural mechanisms of localization.
V: Cognition and Hearing
A: Auditory scene analysis ( McAdams & Bigand, Chapter 2, by Bregman). The problem of the sound source and multiple sound sources ; auditory attention; stimulus regularities with coherent modulation of harmonics and amplitudes, and spatial location and other timing effects.
B: Neuropsychology (McAdams & Bigand, Chapter 7, by Peretz) Auditory agnosia and the recognition of auditory objects. Functional organization and partial specialization of the cerebral hemispheres. The importance of dissociative effects. "Apperceptive" vs "Associative" agnosia -- specific sensory dimensions and dedicated speech/musical mechanisms.
VI: Concluding remarks: Strengths and weaknesses of our current knowledge about audition. Practical needs for treating the hearing impaired, the development of prosthetic devices and for "hearing competence" in machines.