Unifying the Midbrain: The Commissure of the Inferior Colliculus

Rees, A; Orton, LD

doi:10.1093/oxfordhb/9780190849061.013.21

Unifying the Midbrain: The Commissure of the Inferior Colliculus

Lookup NU author(s): Professor Adrian Rees ORCiD, Dr LLwyd Orton

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Abstract

Commissural fibres that interconnect the two sides of the brain are found at severalpoints along the auditory pathway, thus suggesting their fundamental importance for theanalysis of sound. This chapter presents an overview of what is currently known aboutthe anatomy, physiology, and behavioral influences of the commissure of the inferiorcolliculus (CoIC)—the most prominent brainstem auditory commissure—that reciprocallyinterconnects the principal nuclei of the auditory midbrain, the inferior colliculi (IC). Theprimary contribution to the CoIC originates from neurons projecting from one inferiorcolliculus to the other, with the dorsal cortex and central nucleus providing the mostextensive connections. In addition, many ascending and descending auditory centers sendprojections to IC via the CoIC, together with a diverse range of sources located outsidethe classically defined auditory pathway. The degree of interconnection between the twoICs suggests they function as a single entity. Recent in vivo evidence has established thatCoIC projections modulate the neural representation of sound frequency, level, andlocation in IC, thus indicating an important role for the CoIC in auditory processing.However, there is limited evidence for the influence of the CoIC on auditory behavior.This, together with the diversity of sources projecting via CoIC, suggest unknown rolesthat warrant further exploration.