Connections between midbrain hearing centers influence neuron responses in the auditory midbrain

Blocking excitation of commissural projections in the inferior colliculus altered neural responses to sound.

• The commissure of the inferior colliculi connects corresponding frequency regions between the two sides of the auditory midbrain.
• Commissural projections primarily originate from excitatory neurons, with some evidence of GABAergic inhibitory neuron involvement.
• Inhibition observed in neural responses could arise from direct (monosynaptic) or indirect (disynaptic) connections.
• Responses to both monaural and binaural sound stimulation were influenced by blocking input from the opposite inferior colliculus.
• Effects of blocking input were more pronounced at near-threshold sound levels.
• The findings indicate that the commissure of the inferior colliculus may play a role in modulating the responsiveness of neurons to sound.

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