Hearing 1 Flashcards
What are 7 characteristics of hearing
Communication/language Hard to obstruct Active during sleep Can hear from 360 degrees around us Courtship Defense Music
Sound
How fast
Vibrations that travel through air or other medium
Speed (in air, room temp): 340m/s
Sound Frequency
Measure in cycles per second, Hz
Determines our sense of pitch
Sound Amplitude
Measures in decibel, dB
Determines our sense of loudness
Pure Tone
A sound with sinusoidal waveform
Pitch Perception: Species Differences
Humans hear frequencies between 20Hz-20,000Hz
Elephants: 10Hz-12,000Hz
Cats extend higher
Bats fair higher: 20,000-200,000 Hz (20-200kHz)
Complex Sounds
Most sounds are not pure tones
Fourier Transform
Decomposition of a sound (or other signal) to the frequencies that make it up
What does a spectrogram show
Frequencies that make up the sound, and how they change over time
What scale measures loudness
A Decibel Scale
(Log scale: a jump of 20 dB = 10 times higher sound pressure
-The Ear-
What structure collects sound and directs it down the ear canal
Sound air pressure waves strike what membrane
Middle ear bones pass vibrations to where
Pinna
Tympanic Membrane
Cochlea
The Cochlea
A coiled tube containing and the basilar membrane, which vibrates with the sound
The Basilar Membrane
Organized tonotopically
High frequency sounds cause the basal (thick) end to vibrate
Low frequency sounds cause the apical (thin) end to vibrate
The basilar membrane decomposes complex sounds into the component frequencies
Hair cells convert sounds to electrical signals
Vibration of the basilar membrane causes movement of hair cell sterocilia
Movement of hair cells opens K+ channels, depolarizing the cell
Depolarization causes neurotransmitter release (no action potentials)
The nerve that sends signals from hair cells to the cochlear nucleus in the brainstem
Auditory Nerve
What do projections to the cochlear nuclei retain
Tonotopic Organization
Noise-and age-related hearing loss
One in three people in the US between the ages of 65 and 74 has hearing loss
Nearly half of those older than 75 have difficulty hearing
Enhanced by excessive exposure to loud sounds
Often due to death of hair cells
Hearing Aid
A small electronic device that amplifies sounds
Three basic parts: microphone, amplifier, and speaker
Cochlear Implant
Used in complete or near-complete deafness
Bypasses/replaces hair cell, to directly stimulate the auditory nerve
Superior Olivary Nucleus
The cochlear nuclei send information to superior olivary nuclei
Brainstem nuclei critical for sound localization
Note that sound location has to be computed-it is not encoded in peripheral receptors
Having two ears provide cues to localize sounds
Detects interaural time differences (ITD)
Medial Superior Olive (MSO)
Detects interaural level differences (ILD)
Lateral Superior Olive (LSO)
The Inferior Colliculus and Superior Colliculus
Inferior Colliculus receives converging sound information
Sends information about sound location to the visual superior colliculus
This is integration of auditory and visual maps
What is sound localization sensitive to
Experience
The neural basis of plasticity in sound localization
Steps and Structures
- Auditory and visual receptive fields are normally aligned
- Prisms create mismatch of auditory and visual receptive fields
- Auditory remapping realigns receptive fields
ICC: Central nucleus of the inferior colliculus
ICX: External Nucleus of the inferior colliculus
SC: Superior Colliculus
