Auditory System: Introduction

	Sound: Physics; Salient features of perception.
		Weber-Fechner laws, as in touch, vision
	Auditory Pathway: cochlea – brainstem – cortex
		Optimal design to pick up the perceptually salient features
		Coding principles common to other sensory systems:
			sensory or “place” maps,
			receptive fields,
			hierarchies of complexity.
		Coding principles unique to auditory system: timing
		Physiology explains perception
	fMRI of language processing
	Plasticity (sensory experience or external manipulation).
	Diseases:
		Hearing impairment affects ~ 30 million in the USA

Sound: a tiny pressure wave

	Waves of compression and expansion of the air
		(Imagine a tuning fork, or a vibrating drum pushing the air molecules to vibrate)

Pitch (Frequency): heard in Octaves

Complex sounds: Multiple frequencies

Loudness: Huge range; logarithmic

Timing: Used to locate sound sources

Auditory System: Ear

Middle Ear: Engineering; diseases

Inner ear: Cochlea

Basilar Membrane

Basilar Membrane: tonotopy, octaves

Organ of Corti

Organ of Corti

Transduction: inner hair cells

Auditory System: Hair Cells

Auditory System: Hair Cells

Auditory System: Hair Cells

Hair Cells: Tricks to enhance response:

Cochlear prosthesis

Auditory Nerve (VIII cranial nerve)

Auditory Nerve (VIII): Receptive fields

Auditory Nerve (VIII): Receptive fields

Auditory System: Central Pathways

Auditory System: Central Pathways

Cochlear Nucleus:

Auditory System: Central Pathways

Superior Olive: Locates sound sources

Superior Olive: locates sound sources

Auditory System: Midbrain

Auditory Cortex: Complex patterns

Auditory Cortex: Complex patterns

Auditory Cortex: Complex patterns

Auditory Cortex: “What vs. Where”

Auditory System: Speech Areas

Auditory System: Speech Areas

Central auditory lesions

Auditory System: Cortical Plasticity

Auditory System: Recapitulation:

	Sound: Physics, Perception
		Characterizing: Frequency (pitch), Loudness
		Timing (sound source location; discriminating complex sounds)
		Weber-Fechner law: perceptions are logarithmic; just noticeable differences are proportional to the value (of loudness or pitch)
	Pathway: cochlea – brainstem – cortex
		Ear: finely engineered to pick up sound
		Parallel processing of pitch, loudness, timing, (complex sounds)
		“Physiology explains perception”: receptive fields, tuning curves, place coding for pitch, loudness, sound source location. Similar to sensory systems of vision, touch
		Higher along pathway -> more complex processing.
	fMRI of language processing
	Plasticity (sensory experience or external manipulation).