The Journal of Neuroscience, November 15, 2000, 20(22):8533-8541
Spectral Integration in the Inferior Colliculus of the Mustached
Bat
Scott A.
Leroy and
Jeffrey J.
Wenstrup
Department of Neurobiology and Pharmacology, Northeastern Ohio
Universities College of Medicine, Rootstown, Ohio 44272-0095
Acoustic behaviors including orientation and social communication
depend on neural integration of information across the sound spectrum.
In many species, spectral integration is performed by combination-sensitive neurons, responding best when distinct spectral elements in sounds are combined. These are generally considered a
feature of information processing in the auditory forebrain. In the
mustached bat's inferior colliculus (IC), they are common in frequency
representations associated with sonar signals but have not been
reported elsewhere in this bat's IC or the IC of other species. We
examined the presence of combination-sensitive neurons in frequency
representations of the mustached bat's IC not associated with
biosonar. Seventy-five single-unit responses were recorded with the
best frequencies in 10-23 or 32-47 kHz bands. Twenty-six displayed
single excitatory tuning curves in one band with no additional
responsiveness to a second signal in another band. The remaining 49 responded to sounds in both 10-23 and 32-47 kHz bands, but response
types varied. Sounds in the higher band were usually excitatory,
whereas sounds in the lower band either facilitated or inhibited
responses to the higher frequency signal. Interactions were usually
strongest when the higher and lower frequency stimuli were presented
simultaneously, but the strength of interactions varied. Over one-third
of the neurons formed a distinct subset; they responded most
sensitively to bandpass noise, and all were combination sensitive. We
suggest that these combination-sensitive interactions are activated by elements of mustached bat social vocalizations. If so, neuronal integration characterizing analysis of social vocalizations in many
species occurs in the IC.
Key words:
auditory pathways; bat; combination sensitive; complex
sounds; frequency integration; inferior colliculus; mustached bat; spectral integration
Copyright © 2000 Society for Neuroscience 0270-6474/00/20228533-09$05.00/0