1 / 7

Cochlear Electrophysiology

Cochlear Electrophysiology. Zemlin pp. 489-494. Electrical Potentials. DC vs. AC Direct Current = stimulus doesn’t change with time, constant; i.e. battery Alternating Current = always changing over time, looks like a sine wave Stimulus Dependent vs. Stimulus Independent

cecily
Télécharger la présentation

Cochlear Electrophysiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Cochlear Electrophysiology Zemlin pp. 489-494

  2. Electrical Potentials • DC vs. AC • Direct Current = stimulus doesn’t change with time, constant; i.e. battery • Alternating Current = always changing over time, looks like a sine wave • Stimulus Dependent vs. Stimulus Independent • Stimulus Dependent = potentials only present if there is an acoustical sound present • Stimulus Independent = potentials always present with and without acoustical stimuli

  3. Stimulus Independent EP IP Stimulus Dependent SP CM AP Stimulus Independent vs. Dependent

  4. Three DC Potentials • Endocochlear Potential (EP) • Békésy discovered EP by putting the electrode in the scala media and discovered a +100 mV potential with respect to a neutral point on the body • Tasaki discovered EP was due to the Stria Vascularis • Intracellular Potential (IP) or organ of corti potential • Recorded -50 mV inside cells of organ of corti • Summating Potential (SP) • DC that is only during very loud intensities of acoustic stimulation

  5. +100 mV Reticular Lamina -50 mV

  6. Two AC Potentials • Cochlear Microphonic (CM) • Reproduces frequency and waveform of a sinusoid perfectly • Fig. 6-115 (p. 492) • Generated from OHC • Action Potential (AP) • Electrical activity from the VIII Nerve • Can be measured from anywhere in the cochlea or in the auditory nerve

  7. Differential Electrodes • Measure the CM, we also measure the AP unless we use differential electrodes • Tasaki (1954) was able to separate the CM & AP by using differential pair of electrodes • One electrode above reticular lamina (Scala Media or Scala Vestibuli) and the other electrode in the Scala Tympani • By changing the polarity, the AP cancels out, while the CM is doubled in amplitude • This proved Békésy’s Traveling Wave Theory

More Related