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56 Cards in this Set

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Where is the start of the auditory neural pathway?
Cochlear nerve - CN VIII
Where does the cochlear nerve synapse first?
Ventral and Dorsal Cochlear nuclei (spiral ganglia)
Where does the Dorsal Cochlear nucleus project to?
Via the lateral lemniscus to the InferiorColliculus
Where does the ventral cochlear nucleus project to?
2 places:
1. W/ DCN to lateral lemniscus to inferior colliculus
2. To SOC then to IC via LL
Which pathway goes to the SOC?
That for sound localization
Which pathway goes directly to the LL/IC?
That for pattern recognition
Where does the inferior colliculus project to?
Superior Geniculate Nucleus then to the Primary auditory cortex
What is primary auditory cortex also called and where is it located?
Heschel's gyrus in the superior temporal lobe
What are the numbers of the primary auditory cortex?
A1 - Brodmann's area 41
What is the first place of binaural convergence?
SOC in pons
Why is it difficult to localize pathologic lesions in the auditory system?
Because there are many crossovers - makes topography and laterality of limited use for diagnosing pathologies.
Where exactly is auditory cortex A1 located?
Embedded within the lateral fissure of sylvius
Where does the primary auditory cortex project to?
Multiple higher order cortical areas surrounding A1
Function of Wernicke's area:
speech interpretation - comprehension of language
Where is Wernicke's area located?
On the left side of the brain, in the superior temporal gyrus.
How is the auditory cortex organised?
Hierarchically.
Where do lesions generally have to be to make unilateral hearing losses?
Peripheral or in the cochlear nucleus
What is Tonotopic Organization?
Preservation of the topography of the peripheral receptor array within the central pathways of the auditory sytem.
What exactly is the "receptor array" that gets preserved by higher neurons in the auditory system?
The receptive hair cells of the cochlea that are arranged along the basilar membrane.
important to know; where is the cochlear nucleus located?
In the medulla
To what tones are hair cells sensitive as you move along the basilar membrane from base to apex?
Increasingly lower frequency tones.
Why does the basilar membrane respond to lower freq tones at its apex?
Because it is wider and more floppy there.
So what is the receptive field of an auditory nerve cell?
The region of the basilar membrane to which it is responsive.
Characteristic frequency
The frequency to which a cell is best responsive
What is the frequency tuning curve?
The curve that describes how well a cell responds to higher and lower frequencies.
What are the axes for the frequency tuning curve?
X - frequency
Y - spike rate
Z - intensity
At an auditory nerve cell's characteristic frequency (X) what makes the tuning curve broaden?
increasing intensity
What does it mean that the tuning curve broadens?
At a neuron's characteristic frequency as intensity increases the neuron responds to a wider range of tone.
What do we realize by understanding that auditory nerves have characteristic frequencies?
Nerves have receptive fields that correlate with specific regions of the basilar membrane.
Components of a Frequency Response Curve:
-Frequency and Spike rate change
-Intensity held constant
What does a frequency response curve show?
An auditory nerve's Characteristic frequency
Components of a Tuning Curve:
-Intensity and frequency change
-Spike rate held constant (isorate)
What does the tuning curve show?
How well an auditory nerve responds to different frequencies
Components of the Intensity function curve:
-Changing Intensity/spike rate
-Hold freq at characteristic (best)
What does the intensity function curve show?
That as intensity increases, the tuning curve for a neuron gets wider and the nerve responds to a wider range of tones.
So how does an auditory nerve's response change as intensity of sound decreases?
It becomes narrower- more sharply tuned; less likely to respond to sounds that are at different frequencies other than its own personal characteristic frequency.
How does the tonotopic arrangement of hair cells on the basilar membrane translate to the CNS higher pathways?
It remains; is preserved; tonotopic maps are found in most major auditory nuclei, the primary auditory cortex, and secondary auditory cortex!
2 ways in which the auditory neural system is functionally organized:
1. Localization pathways
2. Recognition pathways
What pathway carries the initial localization fibers?
Where is my OLIVE
-VCN -> superior olivary complex
What pathway carries the initial pattern recognition fibers?
DCN/VCN -> LL -> inf colliculus
what is the primary auditory area A1 responsible for?
Sorting out localization vs recognition of sound
What is the cortex surrounding A1 responsible for?
Higher order processing of sound
2 important areas surrounding the primary A1 auditory cortex:
WHAT IS THE FUNCTION OF EACH?
1. Wiernicke's area - for speech analysis (comprehension)
2. Broca's area - for speech PRODUCTION
Result of a lesion to Wiernicke's area:
Can't comprehend questions so can't formulate answers
Another name for Wiernicke lesions:
Wernicke's Aphasia
Lesions to Broca's area result in:
Word salad -> you can understand the question, and formulate an answer, but can't get the words out - just a jarbled mess.
Is Wernicke's aphasia lack of speech?
No; they can talk b/c broca's area is still ok; just don't talk because not intelligent enough to.
How are cells higher up in the auditory complex different in terms of selectivity compared to early hair cells?
They are more responsive - can be finicky and respond only to different complex features of sounds.
What are the components of speech sounds?
-Initial formant (changes over time)
-Sustained tone
What is likely the difference between similar speech sounds?
Only the dynamic components - initial formant
2 factors that allow us to localize sound:
-Binaural time delay
-Binaural intensity difference
What causes the binaural time delay?
The fact that our two ears are located at different places in space, so one recieves soundwaves at a time before the other.
What causes the binaural intensity difference?
Shadowing of the head
Where does interpretation of interaural time and intensity differences begin?
At the superior olivary complex - the first place of binaural convergence.
How does the SOC allow localization of sound?
By the fact that specific neurons within the SOC only fire when recieve SIMULTANEOUS input from 2 inputs (from each ear) - this creates a place code for location of impulse.
What is the process of SOC cells responding to converging input from right/left pathways?
Temporal coincidence