higher auditory systems Flashcards
what range can humans hear?
realistically 30-18000 Hz
what is the effect of water on high frequencies
it dampens them quickly
how do dolphins use ultrasound
in a restricted are to catch prey
why do wales use low frequency sound?
it can travel long distances in water, so they can use it to communicate with each other over many miles
what happens when wavelength is smaller than barrier?
shadow is generated behind the barrier
some sound is reflected
some sound is absorbed (dependant on the material)
what is the basis of echolocation
that some sound is reflected when the wavelength is smaller than the barrier
bats and echolocation
Bats have to us high frequency (short wavelength) sound so that it reflects off small prey
don’t want the wave to diffract around
Rely on sound to create a three-dimensional map of the world
how do blind people create a 3D representation of the world?
- visual cortex generates a 3D map of the world based on vision
- blind people cannot generate a 3D map of the world based on visual input, however they can use auditory input to generate a 3D ‘sound map in visual cortex
they use the visual cortex (occipital lobe) to process the sounds from echolocation, as this area is not used for visual input
due to plasticity of the brain
isn’t as precise as visual input
organisation of the auditory cortex
tonotopic organisation
low frequencies processed in the anterior most part
what happens in the A1?
perception of sound, but no understanding of it
what does A1 mainly deal wit?
pure tones
how are neurons in A1 specified
specified to a particular frequency
some respond to input from both ears: mostly contralateral but also partially ipsilateral due to cross talk
some respond only to the contralateral ear
where do MGN axons enter the auditory cortex?
layer 4, and a bit at layer 3
where is Hessels gyrus
in the temporal lobe
where does A1 signal to?
the belt region (which is also receiving signals from MGN)
Belt region responds to
more complex features of sound
-can respond to difference in frequency withing a sound, not just pure tone, band width
where does the rostral end of the belt region project to?
via anteroventral pathway to the prefrontal cortex
tonotopic map of the rostral region
reverse direction to A1
what happens as you go through the layers of hessels gyrus
you start to process to a higher level, use memory to start to associate what the sound might be
rostral temporal region
- predicted to be present in humans, based on a region present in primates
- more experimental work needs to be done
- reversal of tonotopic map again
where pathway
postero dorsal pathway
parietal lobe
predominantly right side of brain (evidence from stroke patients)
what pathway
antero ventral pathway
temporal lobe
predominantly left side of brain
ST
superior temporal gyrus
which gender speaks at a slightly higher frequency?
females
where is wernicke’s area?
superior temporal gyrus
purpose of wernicke’s area
comprehension of language
why does wernicke’s area receive visual information
for reading
anterior and dorsal sections of wernicke’s area
the anterior area is part of the what stream
dorsal part goes through the where stream
wernicke’s aphasia
lesion to anterior part of Wernicke’s area
* loss of comprehension of words and sentences
* person talks fluently but what they say is meaningless
brochas area
main area to do with the motor part of language
