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2011.01.13: Nick Lesica - Adaptation and precision in auditory midbrain

  • Sense -> encode -> represent -> decode
  • Cochlea -> brainstem -> inferior colliculus -> thalamus -> cortex
  • Amplitude modulation is critical for speech
    • AM (low Hz) and FM (high Hz) are separated in frequency space
  • Does timing in AM matter? If so, what precision in timing is important?
    • Used mutual information to determine relationship between AM input and neuronal firing rate.
      • Utilized Victor's bin-less method
    • 2 ms of timing jitter reduces mutual information
      • Roll off at 500 Hz, which is upper end of natural stimuli
  • To figure out differences/sources of noise and effect on response screw up known signal until mutual info is same. Then compare the output responses.
  • Adding noise appeared to increase over-all response but did not reduce precision.
  • The IC appears to directly represent the AM signal.
  • Inter-aural timing difference and sound intensity have different effects on the filtering of input.  ITD does not cause changes in the filtering of the signal.