Midbrain local circuits shape sound intensity codes

Calum Alex Grimsley, Jason Tait Sanchez, Shobhana Sivaramakrishnan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Hierarchical processing of sensory information requires interaction at multiple levels along the peripheral to central pathway. Recent evidence suggests that interaction between driving and modulating components can shape both top down and bottom up processing of sensory information. Here we show that a component inherited from extrinsic sources combines with local components to code sound intensity. By applying high concentrations of divalent cations to neurons in the nucleus of the inferior colliculus in the auditory midbrain, we show that as sound intensity increases, the source of synaptic efficacy changes from inherited inputs to local circuits. In neurons with a wide dynamic range response to intensity, inherited inputs increase firing rates at low sound intensities but saturate at mid-to-high intensities. Local circuits activate at high sound intensities and widen dynamic range by continuously increasing their output gain with intensity. Inherited inputs are necessary and sufficient to evoke tuned responses, however local circuits change peak output. Push-pull driving inhibition and excitation create net excitatory drive to intensity-variant neurons and tune neurons to intensity. Our results reveal that dynamic range and tuning re-emerge in the auditory midbrain through local circuits that are themselves variable or tuned.

Original languageEnglish (US)
Article number174
JournalFrontiers in Neural Circuits
Issue numberOCT
StatePublished - Oct 30 2013


  • High divalents
  • Inferior colliculus
  • Local circuits
  • Monosynaptic
  • Sound intensity

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Sensory Systems
  • Cognitive Neuroscience
  • Cellular and Molecular Neuroscience


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