lecture 13 - adrian rees

Question 1

95% of auditory nerve fibres are associated with..

Answer 1

IHCs (rest OHCs)

Question 2

Type 1 nerve fibres associate with

Answer 2

IHCs

Question 3

type 2 nerve fibres associate with

Answer 3

OHCs

Question 4

each type 1 fibres only goes to a single IHC
but each IHC can have…

Answer 4

multiple auditory nerve fibres associated with it

Question 5

type 2 fibres make contact with ______ OHCs

Answer 5

multiple

Question 6

as well as afferent fibres (fibres coming from the hair cells to the brain) hair cells also receive…

Answer 6

efferent fibres from the superior olive

Question 7

what are the efferent fibres thought to do

Answer 7

control firing of type 1 fibres (IHCs)
change the operating characteristics of the OHC

Question 8

type 2 fibres were originally thought to be silent (didn’t signal anything to the brain) however in vitro patch recordings from type 2 fibres show they are not silent. APs can be evoked and spontaneous EPScs occur. fibres are sensitive to ___ (purinergic receptors)
- released following sound induced injury, role in signalling damaging sound levels??

Answer 8

ATP

Question 9

type 1 nerve fibres enter the brain at a level between the

Answer 9

medulla and the pons

Question 10

what is the name of the nucleus that receives input from the auditory nerve fibres

Answer 10

the cochlea nucleus

Question 11

above the cochlea nucleus is the

Answer 11

superior olivary complex which is where the efferent fibres originate from

Question 12

superior olivary complex also has multiple nuclei in it that receive afferent input from the

Answer 12

cochlea nucleus

Question 13

the superior olive then projects into a nucleus the…

Answer 13

lateral lemniscus

Question 14

from the lateral lemniscus there are projections to the…

Answer 14

inferior colliculus (midbrain)

Question 15

from the inferior colliculus there are projections to the

Answer 15

medial geniculate body (auditory centre in the thalamus)

Question 16

from the thalamus these projections go to the..

Answer 16

auditory cortex

Question 17

each ear projects to both left and right sides of the brain but..

Answer 17

pathway from each ear is contralaterally dominant

Question 18

there are many connections coming from the higher centres going back to the levels before. also there are feedback connections from non auditory cortical areas (e.g visual, motor systems)

Question 19

the cochlea nucleus is organised into three subdivisions..

Answer 19

• anterior ventral
• posterior ventral
• dorsal

Question 20

these different regions are the sources of…

Answer 20

different parallel pathways

Question 21

how can we distinguish these 3 divisions

Answer 21

by the cells types we find there

Question 22

what cells are in the anterior ventral region

Answer 22

spherical bushy cells

Question 23

what cells are in the posterior ventral region

Answer 23

globular bushy cells

Question 24

what cells are in the dorsal region

Answer 24

octopus cells

Question 25

as auditory nerve fibres come into the cochlea nucleus they

Answer 25

bifurcate and sends one projection to the anterior ventral region and other projections to the posterior ventral region and then they lead onto the dorsal region

Question 26

parallel pathways from the cochlear nucleus all converge in the

Answer 26

inferior colliculus

Question 27

each fibre entering the cochlear nucleus is tuned to a slightly different frequency.
the fibres that are tuned to higher frequency terminate more…

Answer 27

dorsally (tonotopic organisation)

Question 28

we find this tonotopic organisation at every level of the auditory pathway

Question 29

auditory cortex lies where in the brain

Answer 29

upper bank of the temporal lobe

Question 30

the primary auditory cortex is made up of…

Answer 30

Heschl’s gyrus and planum temporale