Wk 8 - Non-Visual Systems Flashcards
(53 cards)
The former model of sensory processing held that the system was… (x3)
With which five stages?
Hierarchical
Functionally homogenous
Serial
Receptor - thalamus - primary sensory cortex - secondary - association
The current model of sensory processing holds that the system is… (x3)
Meaning that?
Hierarchical
Functionally segregated
Parallel
There are many lateral connections and feedback after receptors send info to thalamus, primary, secondary, association cortices
The pina is…(x1)
Which functions to…(x2)
The external part of ear
Catch passing sound waves
Help with locating sound source
The first point of contact inside the ear canal is the…(x1)
Which is responsible for…(x1)
Tempanic membrane (eardrum) Transfer mechanical energy to the ossicles
Ossicles are…(x1)
Three tiny bones transferring energy from eardrum (tempanic membrane) to cochlea
The organs of Corti consist of…(x3)
And are responsible for… (x1)
Tectorial membrane, lying above the
Basilar membrane, in which are embedded
Hair cells
The transduction of sound energy to nerve impulses
Mechanisms of sound transduction are… (x6)
Stapes attached to base of cochlea
Sets fluid in cochlea into waves
Organ of Corti vibrates -
Tectorial and basilar membranes joined at base, and
Shearing motion against each other leads to
Changed electrical properties on membrane = excitatory action potentials
Sound signals hitting the tympanic membrane are amplified… (x3)
1.3 times by the vibrations of the ossicles, and
17 times by the concentration of tympanic vibrations to very tiny part of oval window
For a total of 22 fold increase in vibration strength
At the auditory threshold, the hair cells of the basilar membrane displace…(x1)
Which is the equivalent of.. (x1)
With such fine distinctions contributing to… (x1)
100 picometers
The top of the Eiffel Tower bending 10mm
Detection of faint sounds (esp when combined with properties of oval window/middle ear amplification)
Frequency theory of pitch perception covers which frequencies, by what mechanism?
0 -100 Hz
Neurones firing at direct equivalent rate per second to frequency
Volley theory of pitch perception covers which frequencies, by what mechanism?
100 - 5000 Hz
Teams of neurons firing in sequence to add up to necessary rate per second
Place theory of pitch perception covers which frequencies, by what mechanism (x5)?
5000 - 23 000 Hz
Based on mechanical properties of basilar membrane
High frequency sounds cause displacement, maximal at the base, like skipping rope;
So hair cells at that point code for high frequencies
At each point along membrane, coded for lower frequency
So if wave makes it right to the tip, will be coded as much lower freq than at base
What two methods allow sound localisation?
Interaural time differences
Interaural intensity differences
Explain the use of interaural time differences in sound localisation (x3)
Sound in front hits both ears at the same time
But off to side - detectable diff in time taken to travel width of the head
Brain compares arrival times, calculates where sound came from
Explain the use of interaural intensity differences in sound localisation (x3)
Particularly for higher frequencies, intensity of sound from one side is different to intensity on other side
Coz head forms a buffer
Brain calculates difference to localise sound source
Mechanisms of coding sound location through interaural time differences (x5)
Loudspeaker closer to left ear - sound arrives slightly sooner to left ear
Coincidence detector – fires maximally to simultaneous signal arrival, connections at a,b,c,d,e
A through D don’t fire, because only hit from left signal, which has head start
E fires because it gets simultaneous signal – the last from the left ear and first from the right,
Codes that sound came from left
Mechanisms of coding sound location through interaural intensity differences (x5)
Sound into left ear, stimulates cochlea, sends neural impulse along to olivary nucleus
Excites it to send excitatory signal from left superior olive to A1
Same time, another pathway sends inhibitory signal to trapezoidal body
Stimulates it to inhibit right olivary nucleus
Giving a push/pull mechanism based on the intensity of the sound
Describe two principles of the organisation of the auditory cortex
Tonotopic organisation: adjacent regions stimulated on basilar membrane stimulate adjacent regions in cortex
Columnar organisation: columns respond to different frequencies
To guard against hearing loss, we should have no more than 5 hrs/wk exposure to noise levels above…(x1)
88 db
Conduction deafness results from…(x1 plus eg)
But does not involve… (x1)
Damage to the tympanic membrane and ossicles
Eg ossicles become fused, no longer transmit vibrations from the outer ear to the cochlea
The nervous system
Sensorineural deafness results from…(x1 plus 4 eg causes)
Auditory nerve fibres not stimulated properly = permanent deafness
Infection, trauma, toxic exposure, loud noise
Tuberculosis patients treated with streptomycin suffered its ototoxic properties in that it lead to …(x2)
Cochlear damage
Some cases, all hair cells destroyed = total sensorineural deafness
Central deafness is caused by…(x1)
Resulting in…(x1 plus 2 egs)
Brain lesions in temporal lobes of cortex (ie stroke)
Loss of specific function
Language processing (left lobe) or
Discrimination of non-language sounds (right lobe)
The meaningful sounds test measures… (x1)
By… (x1)
Showing which pattern of deficits? (x2)
Ability to match correct semantic meaning to a sound
Get played a sound, eg braying donkey, then have to point out similar sound/category or unrelated sound
Need to identify, assign semantic meaning, so left temporal damage affects
Whereas right side doesn’t
