Auditory Process Flashcards
What is extracellular Microelectrode Recording?
A method that aims to listen to the electrical signal of one neuron, which however is not guaranteed. One way to overcome this limitation is to insert the microelectrode into the cell body
Explain sound waves (also compression and rarefication).
-> Generated by the vibration and collision of air particles.
-> Whenever there is a physical movement that causes vibration, air particles collide with each other.
-> Compression = when the source provides a higher air pressure which causes the air particles to pack
-> Rarefication = When the source provides a lower air pressure which causes the air particles to dense less
Explain the 3 dimensions of sound waves
Amplitude: This is the volume of the sound. The higher the amplitude is, the higher the air pressure provided from the source.
Tone (pitch): The higher the frequency is, the higher the tone (pitch) of the sound wave. Frequency refers to the number of sound wave cycles in a second (500 Hz = 500 cycles in a second)
Timbre: The quality of the sound. The lesser the complexity of the sound, the higher the quality of the sound is.
Name all of the structures in the outer ear.
Pinna: The most exterior part of the ear. Designed to maximise the sound waves that enter the ears.
Auditory Canal: Where sound waves travel from the pinna to the middle and inner ear.
Name all of the structures in the middle ear.
Tympanic membrane (eardrum):
-> A thin membrane that moves back & forth whenever it receives vibrations from the auditory canal.
Ossicles:
-> Constructed with 3 bones (namely the malleus, incus and stapes).
-> The malleus is connected to the tympanic membrane and the stapes is connected to the oval window.
-> The Ossicles move back and forth with the tympanic membrane and is used to amplify the incoming vibrations.
Name all of the structures in the inner ear.
Cochlea:
-> The snail-like region that is constructed by 3 channels (namely the Scala Vestibuli, Scala Media, which consists the organ of Corti and Scala Tympani.)
Auditory Nerve:
-> Receives neurotransmitters from the spiral ganglion cells and brings them to the primary auditory cortex, which is located in the superior temporal gyrus
Explain how the cochlea works.
-> The stapes moves the oval window, which then moves the perilymph in the Scala Vestibuli.
-> The frequency of the sound reaches the designated spot of the basilar membrane.
-> Then the movement of the perilymph moves the basilar membrane.
-> The higher the frequency of the sound, the closer to the base of the basilar membrane will be activated.
-> The lower the frequency of the sound, the closer to the apex of the basilar membrane will be activated (Tonotopic organisation).
Explain how hair cells work.
-> Inner hair cells predominantly help us hear.
-> When the basilar membrane is moved by the associated frequency generated by the movement of the perilymph, the stereocilia (connected by tip-links) also bends to the right (towards the kinocilium).
-> The right-shift of the stereocilia opens the ion channels on the cilia, which allows the influx of K+ and CA+ in the endolymph.
-> The change of voltage in the hair cells trigger action potentials in the spiral ganglion cells, which releases a kind of neurotransmitter (glutamate).
-> The glutamate as a bundle travels through the auditory nerve and reach the primary auditory cortex after a complicated pathway.
Explain the tonotopic organisation in the primary auditory cortex.
-> The primary auditory cortex is located at the superior temporal gyrus.
-> After signals reach the primary auditory cortex from the auditory nerve, the neurons in different parts of the primary auditory cortex also reacts to certain frequencies (identified by the signals from different spiral ganglion cells). Lower frequencies in the front part of the cortex while higher frequencies in the back part of the cortex.
Explain how Cochlear Implants work.
-> One kind of deafness is due to the abnormality of hair cells.
-> By performing a cochlear implant, an electrode is inserted into the patient’s cochlea.
-> A speech processor is connected to the electrode. After the speech processor analyses the incoming frequencies, the electrodes can then give an electrical stimulation to the respective regions on the basilar membrane.
-> The electrical stimulation acts as the influx of K+ and CA+ and changes the voltage in the hair cells, which helps triggering action potentials in the spiral ganglion cells.
the earlier the cochlea implant is, the better the __ will be. However, cochlea implants are not optimised for__
language ability; music
where is the suprachiasmatic nucleus and which cell receives light information from the environment
in the hypothalamus (diencephalon); melanopsin ganglion cells
what does retinal implant generate
phosphenes (i.e., light dots)
