title: Intercollicular commissural connections refine the representation of sound frequency and level in the auditory midbrain.
abstract: Connections unifying hemispheric sensory representations of vision and touch occur in cortex, but for hearing, commissural connections earlier in the pathway may be important. The brainstem auditory pathways course bilaterally to the inferior colliculi (ICs). Each IC represents one side of auditory space but they are interconnected by a commissure. By deactivating one IC in guinea pig with cooling or microdialysis of procaine, and recording neural activity to sound in the other, we found that commissural input influences fundamental aspects of auditory processing. The areas of nonV frequency response areas (FRAs) were modulated, but the areas of almost all V-shaped FRAs were not. The supra-threshold sensitivity of rate level functions decreased during deactivation and the ability to signal changes in sound level was decremented. This commissural enhancement suggests the ICs should be viewed as a single entity in which the representation of sound in each is governed by the other.
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Llwyd David
authors.initials: LD
authors.lastname: Orton
authors.affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Adrian
authors.initials: A
authors.lastname: Rees
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001306:Auditory Pathways / Q000187:drug effects / Q000502:physiology*; D001309:Auditory Threshold / Q000187:drug effects / Q000502:physiology*; D004192:Discrimination, Psychological / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D008297:Male; D017551:Microdialysis; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D011343:Procaine / Q000494:pharmacology; D013016:Sound; D003336:Tectum Mesencephali / Q000187:drug effects / Q000502:physiology*
chemical_list: D011343:Procaine
keywords: auditory; commissure; deactivation; guinea pig; neuroscience; receptive field; sensory