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Cochlear Mechanics
Basilar Membrane
Neurophysical Tools for Measuring Neural Responses
Theories of Hearing
Anything goes...
100
Electrical voltage differences which exist between different parts of the cochlea?
What are resting cochlear potentials?
100
Because the basilar membrane does this as it goes from the base to the apex, it creates a gradation of stiffness...most stiff at the base and least stiff at the apex
What is "gets wider"?
100
It is a plot of the intensity needed to make a hair cell or neuron fire above its spontaneous rate across a range of Frequencies. A plot of threshold level vs. frequency, which can also be called an isorate curve , but most people call it this.
What is a frequency tuning curve?
100
Propsed by Wever in 1949, this theory proposed that several neurons acting as a group could fire in response to each cycle of a high F sound, even though they wouldn't be able to fire individually.
What is the volley principle or theory?
100
This kind of anatomical plane would cut the human body into right and left halves....medial would be toward the center, lateral would be towards the outer part of the body.
What is a sagittal cut?
200
The number of inner hair cells and their intracellular potential?
What is 3500 inner hair cells and -40mV
200
Sounds transmitted to the cochlea develop a special kind of wave pattern on the basilar membrane that always travels from the base up toward the apex. This is called...
What is the traveling wave?
200
The frequency to which a hair cell or neuron best responds. It is usually determined by the neurons lowest threshold or greatest magnitude of response to a tone. In other words, The neuron seems to be “tuned” to one frequency
What is its characteristic frequency?
200
Proposed by Rutherford in 1896, this theory claimed that the entire cochlea responds as a whole to all frequencies, instead of being activated on a place by place basis.
What is telephone theory? (temporal theory)
200
Most of the structures which make up the ear are contained within this portion of the skull bone.
What is the temporal bone?
300
The number of outer hair cells and their intracellular potential?
What is 12,000 outer hair cells and -70mV
300
This kind of stimulation causes maximum displacement in the basal end of the membrane, and essentially no vibration at the apex.
What is high frequency stimulation?
300
The are graphic displays of a single neuron’s response to repeated presentations of a given stimulus The vertical axis of this is usually some measure of the number of responses…it might be frequency of responses…percentage of responses….or just number of neural discharges….
What is a histogram?
300
This theory by Helmholtz in 1895 propsed that the basilar membrane was constructed of segments that resonated in response to different frequencies, and that these segments were arranged according to place along the length of the basilar membrane.
What is the resonance place theory?
300
When the light from an otoscope is reflected back from the tympanic membrane as a bright light or reflection, this is called....
What is cone of light? What is light reflex?
400
The perilymph has a reference point at or near zero, while the polarity of the endolymph is about 80-100 mV.Because of the large potential differences between these cells, it is believed that the this may increase the size of the electrical response of the hair cells, making it a more effective and sensitive biologic transducer..
What is the endocochlear potential?
400
This kind of displacement causes the cilia to bend away from the modiolus when the cochlear duct is displaced, which activates the hair cells leading to the excitations of their associated auditory neurons.
What is upward displacement?
400
Temporal coding for tones is revealed by this, which is a graph that shows the timing of neural firings during the presntation of a pure tone.
What is a period histogram?
400
This theory describes how frequency is coded by place and was propsed by Bekesy in 1960, sound travels from the base to the apex in a special wave pattern.
What is traveling wave theory?
400
The utricle, saccule and semicircular canals are part of this and respond to these three things.
What is the vestibular system or balance system...respond to angular acceleration, linear acceleration, and changes in gravity
500
A receptor potential with an alternating current signal that mimcs the stimulus waveform
What is the cochlear microphonic?
500
The basilar membrane is attached medially and laterally at these two places.
What is the osseous spiral lamina medially and the spiral ligament laterally?
500
daily double --These display the total number of responses at each given moment in time to a repeated stimulus…. The greatest # of discharges occurs at the onset of the tone burst (called the “on effect”) The number of discharges decreases or adapts rapidly over the first few msec Then the adaptation (decrease in the firing rate) is much slower while the stimulation is still on When the tone goes off….the number of discharges goes to zero…or near zero And then after a short period of time, the number of discharges returns to the normal spontaneous firing rate
What is the post stimulation histogram?
500
This theory combines both place and temporal theories and propsed that low frequencies are handled by temporal coding, high frequencies by place, and an interaction between the two occurs for the wide range of frequencies between them. Proposed by Wever and Lawrence in 1954
What is the place-volley theory?
500
Daily Double- Many of the efferent neurons that communicate with the Organ of Corti come from this area on both sides of the brainstem.
What is the olivocochlear bundle (OCB) of the superior olivary complex?