title: Experience-dependent overrepresentation of ultrasonic vocalization frequencies in the rat primary auditory cortex.
abstract: Cortical sensory representation is highly adaptive to the environment, and prevalent or behaviorally important stimuli are often overrepresented. One class of such stimuli is species-specific vocalizations. Rats vocalize in the ultrasonic range >30 kHz, but cortical representation of this frequency range has not been systematically examined. We recorded in vivo cortical electrophysiological responses to ultrasonic pure-tone pips, natural ultrasonic vocalizations, and pitch-shifted vocalizations to assess how rats represent this ethologically relevant frequency range. We find that nearly 40% of the primary auditory cortex (AI) represents an octave-wide band of ultrasonic vocalization frequencies (UVFs; 32-64 kHz) compared with <20% for other octave bands <32 kHz. These UVF neurons respond preferentially and reliably to ultrasonic vocalizations. The UVF overrepresentation matures in the cortex before it develops in the central nucleus of inferior colliculus, suggesting a cortical origin and corticofugal influences. Furthermore, the development of cortical UVF overrepresentation depends on early acoustic experience. These results indicate that natural sensory experience causes large-scale cortical map reorganization and improves representations of species-specific vocalizations.
authors.affiliation: Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720-3190, USA.
authors.forename: Heesoo
authors.initials: H
authors.lastname: Kim
authors.forename: Shaowen
authors.initials: S
authors.lastname: Bao
mesh_terms: D000818:Animals; D001303:Auditory Cortex / Q000254:growth & development* / Q000502:physiology*; D005260:Female; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014465:Ultrasonics; D014828:Vocalization, Animal / Q000502:physiology*
keywords: auditory cortex; development; inferior colliculus; plasticity; vocalizations