A discontinuous tonotopic organization in the inferior colliculus of the rat.
Audible frequencies of sound are encoded in a continuous manner along the length of the cochlea, and frequency is transmitted to the brain as a representation of place on the basilar membrane. The resulting tonotopic map has been assumed to be a continuous smooth progression from low to high frequency throughout the central auditory system. Here, physiological and anatomical data show that best frequency is represented in a discontinuous manner in the inferior colliculus, the major auditory structure of the midbrain. Multiunit maps demonstrate a distinct stepwise organization in the order of best frequency progression. Furthermore, independent data from single neurons show that best frequencies at octave intervals of approximately one-third are more prevalent than others. These data suggest that, in the inferior colliculus, there is a defined space of tissue devoted to a given frequency, and input within this frequency band may be pooled for higher-level processing.
Malmierca
Manuel S
MS
Auditory Neurophysiology Unit, Laboratory for the Neurobiology of Hearing, Faculty of Medicine, University of Salamanca, 37007 Salamanca, Spain. msm@usal.es
Izquierdo
Marco A
MA
Cristaudo
Salvatore
S
Hernández
Olga
O
Pérez-González
David
D
Covey
Ellen
E
Oliver
Douglas L
DL
D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001306:Auditory Pathways / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001710:Biotin / Q000031:analogs & derivatives; D001931:Brain Mapping; D003911:Dextrans / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000378:metabolism; D021621:Imaging, Three-Dimensional / Q000379:methods; D007245:Inferior Colliculi / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D051381:Rats; D020318:Rats, Long-Evans
D003911:Dextrans; C076397:biotinylated dextran amine; C015219:fluorescein isothiocyanate dextran; D001710:Biotin; D016650:Fluorescein-5-isothiocyanate