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Auditory Processes, Sound Localization, & the Auditory Cortex - Coggle…

- - - - the axons innervate the dorsal cochlear nucleus and ventral cochlear nucleus ipsilateral to the cochlea they came from 🎋
        
        More complex, multiple pathways
        
        one particularly important pathway
        
        Cells in the ventral cochlear nucleus send axons that project to the superior olive on both sides of the brain stem 🫒🫒 :world_map:
        
        lateral lemniscus
        
        inferior colliculus of the midbrain
        
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        dorsal path bypasses the superior olive
  - - - characteristic frequency
        
        Tonotopy
        
        map of the basilar membrane within the cochlear nuclei.
        
        but these maps do not contain neurons with very low characteristic frequencies, below about 200 Hz
        
        additional information about frequency
        
        phase locking
        
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    - - higher intensity
        
        auditory nerve fiber fires faster
        
        bc the basilar membrane vibrates with greater amplitude
        
        broadening of the frequency range
        
        bc of activation of more hair cells
- - - - distance between your ears is 20 cm
        
        sound coming from the right will reach your left ear 0.6 msec after your right ear. (or vice versa)
        
        If the sound comes from straight ahead, there is no interaural delay
        
        angles between straight ahead and perpendicular, the delay will be between 0 and 0.6 msec
      - Detected by specialized neurons in the brain stem
        
        good for sudden sounds, or continuous sounds at low freq. (interaural delay of the peak in the wave)
        
        for continuous tones at high frequencies: sound wave is smaller than the distance between your ears (i.e., greater than about 2000 Hz).
        
        uses a different process: interaural intensity difference
        
        head effectively casts a sound shadow - sound comes directly from the right, the left ear will hear a significantly lower intensity
        
        There is no sound shadow at low frequencies. (between 20-2000Hz)
        
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  - - - cause reflections of the entering sound
        
        delays between the direct path and the reflected path change as a sound source moves vertically
- - - - neurons have characteristic frequencies covering the audible spectrum of sound.
        
        low frequencies: rostrally and laterally, whereas high frequencies: caudally and medially
        
        there are isofrequency bands running mediolaterally across A1
        
        different frequency bands may be processed in parallel by tonotopically organized structures.