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Unformatted text preview: 2/9/12 1 Tinnitus • The perception of sound in the absence of an acoustic stimulus – “Ringing in ears” • 10-15% of all adults • Cause – Multiple: noise induced, some drugs (e.g., aspirin), aging – Related to hearing loss, but not necessarily produced by the damaged ear per se • Can have tinnitus even when auditory nerve is cut MEG overlaid on MRI scan of subject with unilateral tinnitus Central activity in the in tinnitus patients If brain is active, then perception… it doesn’t need to be started by sound Leading Hypothesis: loss of inhibition in the central auditory pathways. Neural coding • What is it – What Frequencies at What Intensities • Where is it Neural coding • What info is available ? – Action potentials • Simple yes or no event; can’t be “size” – Location of activity – Rate of activity – Pattern of activity Auditory Neurons show Frequency Tuning Each has a “best frequency” So…Brain knows which frequencies are in the sound by which neurons are active FREQUENCY “Tuning Curves” Tonotopic (frequency map) Organization 2/9/12...
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- Spring '12
- Tinnitus, Sound localization, Interaural time difference