Lecture 11-12

Sound

Vibration in a medium, usually air; waves of compression and decompression

Frequency

Sound cycles per second

Pure tone

One frequency

Complex sounds

Speech, music, and noise mixes

Pinna

Outer ear; funnels sound into the auditory canal and favors sounds infront of you

Eardrum

tympanic membrane; vibrates and passes the vibration

Ossicles

comprised of 3 tiny bones, hammer, anvil and stirrup; work like levers to amplify sound by 30 times

Eusachian tube

Equalizes air pressure

Oval window

Sends pressure waves through the fluid inside the cochlea

Cochlea

A coiled tube in the ear that’s about 35 mm long; has 3 fluid filled canals; when fluid wants to move, the round window flexes in order to do so

Basilar membrane

membrane filled with hair cells and next to the tectorial membrane; when this membrane vibrates, hair cells bend and cause a neuronal signal, type of bends activate either potassium or calcium ions, which causes depolarization

Inner hair vs outer hair cells

Inner hair cells are sensory cells that connect most of the auditory neurons; outer hair cells amplify the cochlea’s response and sharpen frequency tuning

Describe the process of going from the cochlea to cortex

auditory nerve carries signals to brain stem nuclei, then inferior colliculi, than medial geniculate, than nucleus of the thalamus; input crosses to the opposite side of the auditory cortex where it meets the dorsal steam, but the sound is identified by the ventral stream.

Tonotopic

Neighboring areas are able to respond to neighboring frequencies

Auditory cortex

Where the signal is processed; most inputs cross to its opposite side, some stay on the same side; a map of the basliar membrane

Frequency theory

Auditory neurons fire at the same rate as the frequency of sound

Volley theory

neurons take turns firing in order to keep the sound

Place theory

Frequency is coded by where the basilar membrane vibrates the most

lateral inhibition

Sharpens tuning, so we can tell apart tones

frequency place theory (todays view of auditory processing)

Neurons follow the sound’s freuency only fro low pitches, higher pitches are coded by place

Cochlear implant

sends each frequency to its own place along the cochlea

Cocktail party effect

picking out one conversation from everything else in the auditory scene; due to attention being able to boost the sound of something

Fourier analyzer

breaks complex sounds into its component frequencies

Superior olivary nucleus

Where cues are computed on the brain stem

Intensisty difference between ears

Your head casts a sound shadow, so the near ear hears it ouder

Timing difference between ears

Sound reaches the far ear up to .5 ms later

How does the brain spatially tell where something is

The pinna and body reshape the sound, being able to tell where is where

Broca’s Aphasia

A language impairment caused by brain damage in the Broca’s area

Wernickes area

Back of the left temproal lobe

Wernickes aphasia

trouble understanding and producing meaningful language

Receptive ahasia

Normal rhythm and speech but words makes little sense

Alexia

the inability to read

agraphia

inability to write

Dyslexia

Impaired reading; Dyslexic patients have a left planum temporal (more responsible for speech) thats 13% larger than the right, largely assumed to be because of trouble learning which sounds go with which letters

What are the three patterns within language network disorders

Phonological (linking letters to sounds), surface (words spelled unlike they sound), and rapid automatic naming (slow to recognize letters and numbers)

Difference between right and left planum temporale

Right temporale focuses on the emphasis, rhythm, and meaning behind speech; the left focuses on efficiency in speech

Tympanic membrane

The eardrum which seperates the outer and middle ear and passes vibration to the ossicles

intermural intensity difference j

A difference in the intensity of a sound at the two ears, used to locate sounds above about 2000Hz

Interaural timing difference

a difference in the sound’s arrival time at the two ears

The wernicke’s Geschwind Model

A model of how language areas work together; auditory cortex to Warnicke’s area to brocas area to motor area

wada technique

temporarily anesthetizing one hemisphere at a time, to find which hemisphere controls language