Audition Quiz Study Guide Pathway of sound waves from physical vibration to electrical signals in the brain The auditory nerve carries auditory information into the brain The first synapse in the brainstem is called the cochlear nucleus and receives information from the ipsilateral same side VIII nerve The cochlear nucleus projects auditory information to the contralateral opposite side and ipsilateral superior olive Neurons from the superior olives travel up the brainstem to the inferior colliculus The superior colliculus is important for the vision localization From there auditory information goes through the medial geniculate nucleus of the thalamus MGN which acts as a relay station to project information to the temporal lobe also known as the auditory cortex There is also some descending information cortex to MGN suggesting that sensory information is bi directional in which feedback from the brain is tightly integrated with sensory information The ossicles amplify sound by acting as a lever to increase the amount of pressure they put on the oval window and by concentrating energy from a larger to smaller surface area This is important because it is more difficult for vibrations to travel through fluid than air and the oval window the opening of the cochlea inner ear is a fluid filled chamber The inner ear is where vibrations are transduced to neural signals i e from a mechanical stimulus to an electrical signal What does tonotopic mean How does this relate to the cochlea and the auditory cortex Tonotopic organization organization of neurons according to their characteristic frequency Spatial arrangements of where different auditory tones are processed in the brain Tonotopy in the auditory system begins at the cochlea In humans six tonotopic maps have been identified in the primary auditory cortex their anatomical locations along the auditory cortex What happens inside the cochlea Specifically how does transduction occur in the cochlea The opening of the cochlea inner ear is a fluid filled chamber The inner ear is where vibrations are transduced to neural signals i e from a mechanical stimulus to an electrical signal This is the auditory portion of the inner ear Psychophysics know psychophysical methods we learned about Psychophysics the science of quantitative relationships between physical and psychological subjective events Method of Limits A psychophysical method in which a particular dimension of a stimulus or the difference between two stimuli is varied incrementally until the participant responds differently Method of Adjustment The method of limits for which the subject controls the change in stimulus This is the least accurate because it is difficult to have the subject reliably adjust the stimulus to the same definition threshold across trials Method of Constant Stimuli method of right and wrong cases A method in which many stimuli ranging from rarely to almost always perceivable or rarely to almost always perceivable from a reference stimulus are presented one at a time Know the two qualities of sound waves Frequency pitch rate of recurrence of oscillations vibrations measured in Hertz Hz Amplitude loudness intensity amount of change in pressure measured in decibels dB What are the different types of deafness What is the difference between them Conductive hearing loss ossicles lose their ability to convey vibrations to the oval window Ear infections Otosclerosis abnormal growth of the ossicles Sensorineuroal hearing loss more common result of damage to the hair cells or auditory nerve Antibiotics or cancer treatments can damage hair cells Typical human hearing range and different ways it is measured Humans can hear frequencies ranging from 20 20 000 Hz anything above or below is inaudible We can have high amplitude low frequency or high and high or low and low It all depends on the amount of energy being emitted Habituation Expectation Expectation Participant expects the stimulus to increase or decrease and thinks that the stimulus should now be detectable and thus responds that it did increase or decrease even if the stimulus is not yet at threshold i e they jump the gun Habituation Participant hesitates to switch his her response Participant continues too responding Y or N too long i e they get used to responding a certain way forget zone out tune out Difference between interaural processes and structures involved in these processes Interaural time difference ITD The difference in time between a sound arriving at one ear vs the other The medial superior olive is the first place in the brain where information fom both ears converge and there are also neurons whose firing rates increase in response to very brief time differences between inputs from two ears Interaural level difference ILD The difference in intensity between a sound arriving at one ear vs the other The lateral superior olives compare excitatory input from the ipsilateral ear and inhibitory input from the contralateral ear Depending on which side of the head the sound is coming from those inputs to the lateral superior olives will be stronger
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