3. From Ear to Thalamus: Sound Localization and Auditory Processing

Vocabulary flashcards focused on key terms related to sound localization and auditory processing in behavioral neuroscience.

Interaural time difference (ITD)

The difference in time taken for a sound to reach each ear,

• used for low-sound localizing sound.

• Binaural cue

no time difference is present when the sound is directly behind or in front

Interaural level difference (ILD)

The difference in sound pressure level reaching each ear,

• helpful in localizing high-frequency sounds.

• Binaural cue

Reduction in sound level at the ear further away from the sound

Head-related transfer function (HRTF)

A spectral cue indicating how the body modifies sound before it reaches the inner ear

• helping with vertical sound localization.

• spectral cue

• pinna, head, and torso influence sound before reaching inner ear ^

• higher frequency above ear than lower

Stereocilia

Hair-like structures on hair cells in the cochlea that deflect in response to sound vibrations, leading to neural signal transduction.

• Kinocilium is the tallest hair

When Stereocilia deflect….

towards kinocilium: hair cells depolarize

away from kinocilium: hair cells hyperpolarize

Cochlea

The spiral-shaped organ in the inner ear that acts as a frequency analyzer, transforming pressure waves into neural signals.

• where membrane moves most depends on sound frequency

• Contains:

  • 1 row of inner cells

  • 3 rows of outer hair cells

• hair cells are called “stereocilia”

Tonotopic organization

The spatial arrangement of auditory nerve fibers corresponding to different sound frequencies.

Sound pressure level (SPL)

A measure of the magnitude of pressure fluctuations in sound, expressed in decibels (dB).

Phase-locking

The phenomenon where neurons fire action potentials at a specific phase of a sound wave, providing frequency information at low frequencies.

Basilar membrane

A membrane in the cochlea that moves in response to sound waves, with different areas tuned to different frequencies.

Auditory pathway

The neural pathway through which auditory information travels from the cochlea to the auditory cortex.

Outer Ear

Sound waves hit the tympanic membrane (eardrum).

Middle Ear

The tympanic membrane causes the ossicles (malleus, incus, stapes) to move, which in turn moves the oval window.

Inner Ear

The movement of the oval window causes the cochlear fluid (perilymph and endolymph) to move. This movement makes the basilar membrane vibrate.

• detected by hair cells