Chapter 7 Physiological Psych
A membrane-covered opening in the inner wall of the middle ear that compensates for changes in cochlear pressure.
What is the round window?
loudnesss; rate; more intense vibrations produce more intense shearing fore on cilia, therefore cells release more NT, therefore more firing occurs. (Doctrine of specific nerve energies and rate law)
_____________ is determined by __________ of hair cell firing. Explain.
-different frequencies produce maximal distortion at different points of the basilar membrane. Also, throughout the auditory system there is a tonotopic representation in which adjacent neurons receive signals from adjacent areas of the basilar membrane. Sound vibrations produce a traveling wave: -HIGH FREQUENCY: near BASE of basilar membrane (front of cochlea) -LOW FREQUENCY: near APEX of basilar membrane (back of cochlea)
define place coding of pitch
-Stapes presses against the oval window to create a force in the cochlea -the cochlea is filled with liquid, which transmits energy -the liquid moves with the help of the membrane covered round window.
describe the cochlear mechanics.
cilia are arranged from tallest to shortest and are connected to each other by "tip links" which attach to the cilia at a point called "insertional plaque". When sound waves move the fluid within the cochlea, the cilia bend with the movement of the fluid. The tallest cilia experience the most movement, and this causes tension along the tip links which opens potassium and calcium ion channels in the adjacent insertional plaques. The calcium and potassium ions flow into the cilia and produce a depolarization.
explain auditory transduction.
an afferent pathway for sound through the cochlear nuclei, to the auditory cortex in the superior temporal lobe.
explain the auditory cortex pathway.
an afferent pathway through the cochlear nuclei to inferior colliculus in the dorsal midbrain, near the cerebellum
explain the inferior colliculus pathway.
An afferent pathway through the cochlear nuclei to the superior olivary nuclei in the medulla
explain the superior olivary nuclei pathway.
PITCH: place coding; firing by hair cells at LOCATION of basilar membrane that is active LOUDNESS: Determined by RATE of action potentials from hair cells
how do we perceive the pitch and loudness of high and medium frequency sounds?
PITCH: rate coding; hair cells at apical end of basilar membrane fire in synchrony with FREQUENCY of sound wave LOUDNESS: determine by NUMBER of active hair cells
how do we perceive the pitch and loudness of low-frequency sounds?
-BASILAR MEMBRANE (forms the base) with the hair cells -TECTORIAL MEMBRANE (forms the roof) -HAIR CELLS in between these layers
the organ of corti consists of what?
amplifier; making the ossicles extremely efficient, the baseplate of the stapes makes more forceful impact against the oval window than the tympanic membrane does against the malleus, because the oval window is so flexible, allowing it to move at just the slightest sound.
the ossicles act as a _____________, allowing what to happen?
-amplitude (intensity)=loudness -frequency=pitch -complexity=timbre
the receptive perceptual dimensions of the following physical dimensions are what? -amplitude -frequency -complexity
mechanoreceptors (physical force that makes them fire)
unlike retinal cells (photoreceptors), auditory receptors are ______________
-approximately 3,500 form a single line of cells along the BASILAR MEMBRANE (they do not touch the membrane , but move with the movement of the liquid inside the cochlea in response to sound) (like seaweed moves in water in response to current) -destruction of these hair cells leads to hearing loss -they are so important to hearing that 95% of the auditory nerve axons synapse with inner ear cells!
what are inner hair cells?
-approximately (12,000) are arranged in three rows along the basilar membrane -serve a structural function, as they actually connect the basilar membrane and tectorial membranes (therefore they do not sway like inner ear hair cells.
what are outer hair cells?
Through cochlear nuclei: -to superior olivary nuclei (medulla) -to inferior colliculus (dorsal midbrain, near cerebellum) -to medial geniculate (thalamus) -to auditory cortex (superior temporal lobe) *mostly contralateral about 80%-20%
what are the afferent auditory pathways?
core, belt, and parabelt
what are the three cortical regions?
cochlear implants restore speech perception by stimulating different regions of the basilar membrane
what can restore speech perception and how?
the fiber link which joins cilia tips
what is a tip link?
The theory which explains the way in which low frequencies are detected: low frequencies are detected by neurons that fire in synchrony with movements of the apical end of the basilar membrane. Because the cochlea only has room for sounds greater than about 200Hz, rate coding perceives the rest of the spectrum, meaning that the sound is coded by the rate of firing. The intensity is coded by the number of hair cells depolarized.
what is rate coding?
-structures which determine the difference in intensity of sounds between the ears, because they have intensity detectors -sounds that are presented closer to the ear will experience a higher intensity of sounds causing increased APs
what is the Lateral Superior Olives?
-structures which determine if sound is to the right or left because the sound will reach one ear sooner, and therefore get to the medulla sooner -these structures have coincidence detectors
what is the Medial Superior Olives?
-the true auditory receptive organ containing hair cells that transduce sound waves into nerve impulses
what is the Organ of Corti?
the secondary association area (receives information from the PAC and the medial geniculate nucleus) -stimulating this area results in people hearing more complex sounds
what is the belt region?
the region that contains the primary auditory cortex -stimulating this area results in people hearing simple, quick sounds
what is the core region?
the specific point where tip links join the adjacent neuron. It is really an ion channel, and the movement of the tip links causes these channels to open allowing calcium and potassium channels to open depolarizing the cilia.
what is the insertional plaque?
the tertiary region (receives information from the belt region and medial geniculate nucleus -stimulating this area results in people hearing very complex sounds and even words
what is the parabelt region?
-some antibiotic drugs produce degeneration of the auditory hair cells. This damage begins at the basal end of the cochlea and progresses toward the apical end. The progressive death of hair cells induced by an antibiotic closely parallels a progressive hearing loss: the highest frequencies are the first to one lost, the lowest are the last. -observations of traveling waves by Von Bekesy, who noticed that different frequencies produce maximal displacement at different points along the basilar membrane.
what is the support of place theory?
complex sounds are composed of a fundamental frequency with overtones of other frequencies, the pattern of activity is detected in the cochlear nerve and sent to primary auditory cortex. -Experience helps us know what the sound is (secondary association areas; hippocampus)
what is timbre?
Basal end of basilar membrane (high pitches) is represented most medially in the auditory cortex while the apical end (lowest frequencies) is most lateral. -essentially, the higher pitches are represented by deeper cortex
what is tonotopic representation?
Pinea, ear canal, and tympanic membrane
what makes up the outer ear?
the cochlea
what parts make up the inner ear?
maltieous, incus, and stapes (the ossicles)
what parts make up the middle ear?
inverse; higher frequencies are closer to the stapes
An ________________ relationship exists between frequency of sound and distance from stapes. Explain.
Sound is funneled into the auditory canal via the Pinea where it vibrates the tympanic membrane, all part of the outer ear. Then the sound vibrates the ossicles and opal window all part of the middle ear. Finally the sound vibrates the fluid inside the cochlea stimulating receptors responding to the movement of the fluid inside the cochlea.
Explain how sound travels through the ear.
-DORSAL STREAM; determine sound location, runs to the parietal lobe (like vision- WHERE is the sound coming from) -VENTRAL STREAM; helps determine meaning, runs to the temporal lobe (like in vision- WHAT is being said and who is saying it)
Like vision, audition has two streams. What are they and what do they determine?