The Journal of Neuroscience, February 15, 2003, 23(4):1464
A Neural Basis for Auditory Feedback Control of Vocal Pitch
Michael
Smotherman1,
Shuyi
Zhang3, and
Walter
Metzner1, 2
1 Department of Physiological Science, University of
California, Los Angeles, Los Angeles, California 90095-1606, 2 Brain Research Institute, University of California,
Los Angeles, Los Angeles, California 90095-1761, and
3 Institute of Zoology, Chinese Academy of Sciences,
Beijing 100080, People's Republic of China
Hearing one's own voice is essential for the production of correct
vocalization patterns in many birds and mammals, including humans.
Bats, for instance, adjust temporal, spectral, and intensity parameters
of their echolocation calls by precisely monitoring the characteristics
of the returning echo signals. However, neuronal substrates and
mechanisms for auditory feedback control of vocalizations are still
mostly unknown in any vertebrate. We used echolocating horseshoe bats
to investigate the role of the midbrain and hindbrain tegmentum for the
control of call frequencies in response to changing auditory feedback.
These bats accurately control the frequency of their echolocation calls
through auditory feedback both when the bat is at rest [resting
frequency (RF)] and when it is flying and compensating for changes in
echo frequency caused by flight-induced Doppler shifts [Doppler shift
compensation (DSC)]. We iontophoretically injected various GABAergic
and glutamatergic transmitter agonists and antagonists into the
brainstem tegmentum. We found that within the parabrachial nuclei and
the immediately adjacent tegmentum, excitatory effects caused by
application of the glutamate agonist AMPA or the GABAA
antagonist bicuculline raised RF and the frequency of calls emitted
during DSC. Bicuculline application routinely blocked DSC altogether.
Alternately, inhibitory effects caused by application of either the
GABAA agonist muscimol or the AMPA antagonist CNQX lowered
call frequencies emitted at rest and during DSC. Such an audio-vocal
feedback mechanism might share basic aspects with audio-vocal feedback
controlling the pitch of vocalizations in other mammals, including the
involuntary response to "pitch-shifted feedback" in humans.
Key words:
audio-vocal feedback control; echolocation; horseshoe bats; Rhinolophus; Doppler shift compensation; parabrachial nuclei
Copyright © 2003 Society for Neuroscience 0270-6474/03/2341464-14$05.00/0
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