w2 - CANS Flashcards
What 7 components make up the CANS?
1) cochlear nuclei (CN): VCN and DCN
2) superior olivary complex (SOC)
3) lateral lemniscus
4) inferior colliculus
5) medial geniculate body
6) auditory cortex
7) corpus callosum
What is the function of the CANS?
- CANS plays a crucial role in receiving and processing sound information, enabling humans and animals to perceive and interact with their acoustic environment
The CANS incorporates several brain regions from the ____ to the ____
cochlear nuclei, cerebral cortex
Our understanding of the human central auditory system is derived from what 4 things?
1) post-mortem anatomical studies
2) psychophysical and electrophysiological experiments
3) structural and functional imaging
4) comparative studies with laboratory animals
What did neuroanatomy of the auditory system help build a foundation for?
speech and language acquisition and diagnosing and treating hearing, speech, and language disorders
What are the 4 crossings of the CANS?
The blue areas have to cross information from one side to another
- 1st cross: DCN
- 2nd cross: TB (trapezoid body)
- 3rd cross: LL
- 4th cross: AC through the corpus callosum
Information to one ear is crossing to the other side of the brain
What are the 2 components of the cochlear nucleus (CN)?
- ventral cochlear nucleus (VCN)
- dorsal cochlear nucleus (DCN)
The primary afferents of the AN are divided into ____ and ____ branches in the CN
ascending, descending
The ascending branch travels to the ____.
rostral pole of the VCN
The descending branch travels to the ____
DCN
The CN is the ____ stage of transforming acoustic information
initial
Where does the CN receive efferent fibers from?
auditory thalamocortical pathways (top down processing)
Explain the CNs characteristic frequency (CF)
the frequency to which it is most sensitive, corresponds to a specific location on the BM of the cochlea.
Explain the CNs tonotopic organization
mimics the BMs cochleotopic organization
CN - The human VCN contains what 5 cells?
- spherical bushy cells
- globular bushy cells
- stellate cells
- octopus cells
- small cap cells
CN VCN - what do the spherical/globular bushy cells and stellate cells do?
- maintain spectral sensitivity and signal patterns
CN VCN - what tests of AP target spherical/globular bushy cells and stellate cells?
- frequency pattern test or pitch pattern test or changes in timing/intensity
- these tests will target these cells directly to show place of involvement
CN VCN - What is a job that only stellate cells do?
stellate cells have different firing patterns and provide excitatory and inhibitory input to other neurons in the cochlear nucleus
CN VCN - What do octopus cells do?
- handle precise timing for detecting sound structures
CN VCN - What tests of AP target octopus cells?
- gap detection
- problem with this task could mean problem with the octopus cells in the VCN
CN VCN - what do small cap cells do?
their function is still unknown
CN DCN - What does the DCN do?
receives input from auditory and non-auditory sources and undergoes complex processing
CN DCN - explain the 3 layers of the DCN
The DCN is organized into 3 layers, containing different types of neurons and interneurons:
1) the molecular layer: dendrites of fusiform cells
2) granule cells: input to layer 1
3) fusiform cells, giant cells, interneurons that link to DCN and VCN
neural fibers connect the layers (and also connect to other parts of the brain)
CN DCN - what do fusiform and giant cells do?
- fusiform cells exhibit a “pauser” firing pattern, while giant cells show a “buildup” pattern.
- fusiform and giant cells are sensitive to monaural acoustic cues, providing information about sound sources in the vertical plane
Difficulty with speech in noise has to do with cells in the ____
DCN
CN - What are the 5 functions of the DCN?
- encoding verticle spectral cues
- detects monaural directional cues (HRTF)
- detecting sound source elevation (high or low sound)
- accurate sound source orientation
- tuberculo-ventral cells in the DCN inhibit VCN bushy cells which reduces echoes (helpful for unilateral HL)
CN DCN - what are proprioceptive signals?
Signals related to position, place, and movement of body and cells
CN - The DCN is the first area of incorporating ____ with auditory information
sensory information
What are the 3 major nuclear groups in the SOC?
1) the medial superior olivary nucleus (MSO)
2) the lateral superior olivary nucleus (LSO)
3) the medial nucleus of the trapezoid body (MNTB)
SOC - explain the MSO
The MSO is tonotopically organized, disproportionately representing low frequencies
SOC - physical separation of the two ears contributes to sound localization in the ____ plane
horizontal
SOC - what are ITDs
- interaural time differences
- used for localizing low frequency sound
SOC - what are IIDs
- interaural intensity differences
- used for high frequency sounds
SOC - MSO involved in encoding ____
ITDs
SOC - LSO involved in encoding ____
IIDs
SOC - MNTB plays a crucial role in ____
sound localization
SOC - the MSO and LSO send projections to: (2)
- dorsal nucleus of the lateral lemniscus (DNLL)
- central nucleus of the inferior colliculus (CNIC)
Tonotopy isn’t just limited to the ____, also in the ____
BM, CAS
The nuclei of the ____ are not well studied in the human auditory brainstem
LL
The LL nuclei are divided into: (2)
- the ventral nucleus of the LL (VNLL)
- the dorsal nucleus of LL (DNLL)
LL - what are the 2 inputs to the ventral nucleus of LL (VNLL)
- contra: VCN cells
- ipsi: MNTB
LL - what are the inputs to the dorsal nucleus of LL (DNLL)
contra: VCN
ipsi: MSO, VNLL
LL - where is the DNLL located?
below the inferior colliculus (IC)
The DNLL projects ____ to the IC
bilaterally
What is the lowest level of auditory processing?
The LL
The LL and the IC do what 2 things?
- contribute to sound source localization and lateralization in both vertical and horizontal planes
- first place for processing auditory information and the complexity of speech (voices)
The ____ is a prominent paired structure in humans and other mammals
inferior colliculus (IC)
The IC is divided into what 2 things?
- a central nucleus (CNIC)
- exhibits tonotopic organization
- receives auditory inputs from CN, SOC, and LL - a surrounding cortex (ICC)
What are the 5 inputs to the IC?
- various auditory nuclei in the brainstem
- auditory thalamus and cortex
- somatosensory
- limbic areas
- motor nuclei of the basal ganglia
IC and LL contribute to what?
sound source lateralizastion/localization
neurons in the dorsal cortex of IC are sensitive to ____
vocalizations
The medial geniculate body (MGB) is a ____ in the auditory system
complex gateway
Only about ____% of MGB synaptic inputs come from cochlear pathways
20
Where do most inputs to the MGB come from?
multiple sources including: cortex, reflecting behavioural states like attention and arousal
What 3 divisions is the is MGB divided into?
- ventral (MGBv)
- dorsal (MGBd)
- medial (MGBm)
MGB - explain the MGBv
- part lemniscal pathway
- receives input from the CNIC
MGB - explain MGBd and MGBm
- parts of the non-lemniscal pathway
- receive major input from ICC (surrounding cortex of IC)
The MGB is a ____ nucleus
multisensory
Explain multisensory nucleus
- visual, tactile, sensory
- also information from the auditory cortex
- uses top down and bottom up processing
Where does the AC in the temporal neocortex receive its main input from?
MGB and related cell groups
AC - where are auditory areas located?
on the lateral surface of the superior temporal gyrus (STG) and its superior surface is within the lateral fissure
AC - Explain the superior temporal gyrus (STG)
The STG is highly folded and variable, with prominent transverse gyri, inclduing heschl’s gyrus (HG)
AC - explain the posterior portion of HG
the posterior portion of HG is traditionally considered the primary auditory cortex (PAC) recognized as the auditory cortical core
AC - Surrounding the auditory core fields are the multiple auditory fields known as the ____
auditory cortical belt
AC - Further out, on the lateral surface of the STG, is the ____
auditory cortical parabelt
AC - Explain the core, belt, and parabelt
- 3 mains parts
- core/PAC/HG
- then belt
- the parabelt
- the farther from the core the more things are being processed
- core = tonotopy
- belt/para = representation of phonemes (more complex than core)
- as we go from the core to the parabelt we see the AC is processing more than auditory information
AC - which framework does the core/belt relate to?
cognitive-driven framework
AC - These temporal auditory fields: core, belt, and para belt are interconnected with eachother and the auditory thalamus to form what?
the auditory forebrain complex
The AC interacts with what other cortical areas?
occipital, parietal, and frontal lobes (engaging in sensory, motor, limbic, and cognitive processing)
Auditory visual interactions of the AC contribute to what?
speech and language processing
Explain why we know that the AC is involved in processing more than sound?
Diseases/disorders in auditory system can impact other modalities (the brain is a network and no systems are isolated)
Tonotopic organization in the central auditory pathway pic
How many subdivisions of the corpus callosum are there and what are they?
- 1-5: the anterior half of the CC (contains fibers interconnecting frontal association cortical areas)
- 6: the isthmus (mostly contains fibers interconnecting the primary motor, somatosensory, and auditory areas (2 halves)
- 7: the splenium (contains fibers interconnecting primary visual and association temporo-occipital and parietal fibers
CC - explain small fiber diameter
- < 0.4 um
- primarily found in regions 2 and 7
- connect prefrontal and temporoparietal association areas
CC - explain large fiber diameter
- 3-5 um
- found in regions 6 (isthmus)
- and 7 (splenium): connect visual cortices
CC fibers interconnecting the 2 primary ACs are the ____ among others
largest
