As promised, 9 articles by Knudsen & Konishi (from Biological Abstracts):
Record 1 of 9
Title: MON AURAL OCCLUSION SHIFTS RECEPTIVE FIELD LOCATIONS OF
AUDITORY MID BRAIN UNITS IN THE OWL TYTO-ALBA
Author(s): KNUDSEN E I; KONISHI M
Source: Journal of Neurophysiology (Bethesda) 44 (4) : 687-695 1980
Abstract: The responses of auditory units with limited spatial
receptive fields (L-F units) were studied before and after acute
monaural occlusion. The L-F units were recorded in the space-mapped
region of the midbrain auditory nucleus (MLD) of the owl (T. alba).
Excitatory receptive fields and best areas were plotted using a
movable sound source under free-field conditions. Occlusion of the
right ear caused auditory receptive fields to move up and to the
right; occlusion of the left ear moved the fields down and to the
left. The magnitude of the field shifts increased with the density of
the plugging material and the firmness of its placement in the ear
canal. In addition to shifting the location of a receptive field unit,
monaural occlusion often altered the size of the receptive field. The
fields of some units expanded, some contracted and others remained
unchanged. When a change in field size did occur, it was the vertical
dimension of the field that was predominantly affected. The finding
that monaural occlusion of either ear shifts the locations of auditory
receptive fields demonstrates unequivocally that these fields derive
from central integration of binaural inputs and that interaural
intensities dictate, to a large extent, the locations and boundaries
of these fields. The direction and magnitude of the receptive-field
shifts are appropriate to explain the behavioral errors in sound
localization observed under similar conditions of monaural occlusion.
This correlation reinforces the speculation that the activity of L-F
units encodes the location of a sound source in space.
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Record 2 of 9
Title: MECHANISMS OF SOUND LOCALIZATION IN THE BARN OWL TYTO-ALBA
Author(s): KNUDSEN E I; KONISHI M
Source: Journal of Comparative Physiology A Sensory Neural and
Behavioral Physiology 133 (1) : 13-22 1979
Abstract: The mechanisms by which the barn owl (T. alba) determines
the azimuth and elevation of a sound source were studied. Localizing
ability was measured by the accuracy of head orientation to a sound
source. When localizing tonal signals, the owl committed the smallest
errors at frequencies between 4-8 kHz. The azimuthal component of
these errors was frequency independent from 1-8 kHz, but the
elevational component increased dramatically for frequencies below 4
kHz. The owl's mean error when localizing wide band noise was nearly 3
times less than its mean error when localizing the optimal frequency
for tonal localization (6 kHz). Occluding the right ear caused the owl
to orient below and left of the sound source; occluding the left ear
caused it to orient above and right of the sound source. With ruff
feathers (facial ruff) removed, the owl continued to localize sounds
accurately in azimuth, but failed to localize sounds in elevation. The
barn owl may use interaural comparisons of sound spectrum to determine
the elevation of a sound source. Interaural onset time and interaural
spectrum are used to identify the azimuth of the sound source. If
onset time is not available (as in a continuous sound), the owl can
derive the azimuth of the source from interaural spectrum alone, but
spatial resolution is poorer.
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Record 3 of 9
Title: SOUND LOCALIZATION BY THE BARN OWL TYTO-ALBA MEASURED WITH THE
SEARCH COIL TECHNIQUE
Author(s): KNUDSEN E I; BLASDEL G G; KONISHI M
Source: Journal of Comparative Physiology A Sensory Neural and
Behavioral Physiology 133 (1) : 1-12 1979
Abstract: The dynamics and accuracy of sound localization by the barn
owl (T. alba) were studied by exploiting the natural head-orienting
response of the owl to novel sound stimuli. Head orientation and
movement were measured using an adaptation of the search coil
technique which provided continuous high resolution azimuthal and
elevational information during the behavior. The owls responded to
sound sources with a quick, stereotyped head saccade; the median
latency of the response was 100 ms, and its maximum angular velocity
was 790.degree./s. The head saccade terminated at a fixation point
which was used to quantify the owl's sound localization accuracy. When
the sound target was located frontally, the owl's localization error
was less than 2.degree. in azimuth and elevation. This accuracy is
superior to all terrestrial animals tested to date, including man.
When the owls were performing open-loop localization (stimulus off
before response begins), localization errors increased as the angular
distance to the target increased. Under closed-loop conditions
(stimulus on throughout response), the owls again committed their
smallest errors when localizing frontal targets, but errors increased
only out to target angles of 30.degree.. At target angles greater than
30.degree. the owl's localization errors were independent of target
location. The owl's frontal region, where the auditory system has
maximum angular acuity, is coincident with the owl's visual axis.
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Record 4 of 9
Title: THE OILBIRD HEARING AND ECHO LOCATION
Author(s): KONISHI M; KNUDSEN E I
Source: Science (Washington D C) 204 (4391) : 425-427 1979
Abstract: Oilbirds [Steatormis caripensis] can navigate in total
darkness of echolocation. The sound energy in their sonar cries is
unevenly distributed over the range from about 1-15 kHz, with a
dominant frequency range of 1.5 to 2.5 kHz. This corresponds to the
most sensitive range of their hearing as determined by
neurophysiological methods. Behavioral tests in their home cave
indicate that the smallest object avoided by them is a disk 20 cm in
diameter.
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Record 5 of 9
Title: SPACE AND FREQUENCY ARE REPRESENTED SEPARATELY IN AUDITORY MID
BRAIN OF THE OWL
Author(s): KNUDSEN E I; KONISHI M
Source: Journal of Neurophysiology (Bethesda) 41 (4) : 870-883 1978
Abstract: The influence of sound location and sound frequency on the
responses of single units in the midbrain auditory area (MLD) of the
owl (Tyto alba) were studied using a movable sound source under
free-field conditions. With this technique 2 functionally distinct
regions in MLD have been identified: a tonotopic region and a
space-mapped region. MLD units were classified according to their
receptive-field properties. Limited-field units responded only to
sound from a small, discrete area of space. Complex-field units
exhibited 2-4 different excitatory areas separated by areas of reduced
response or inhibition. Space-preferring units responded best to a
certain area of space, but their fields expanded considerably with
increasing sound intensities. Space-independent units responded
similarly to a sound stimulus regardless of its location in space.
Limited-field units were located exclusively along the lateral and
anterior borders of MLD. These units were tuned to sound frequencies
at the high end of the owl's audible range (5-8.7 kHz). They usually
responded only at the onset of a tonal stimulus; but most importantly,
the units were systematically arranged in this region according to the
azimuths and elevations of their receptive fields, thus creating a
physiological map of auditory space. Because of this latter, dominant
aspect of its functional organization, this region is named the
space-mapped region of MLD. The receptive fields of units in the
larger, medial portion of MLD were of the space-independent,
space-preferring, or complex-field types. These units tended to
respond in a sustained fashion to tone and noise bursts, and these
units were arranged in a strict frequency-dependent order. Based on
this last property, this region is named the tonotopic region of MLD.
Because of the salient differences in the response properties of their
constituent units, the space-mapped region and the tonotopic region
are involved in different aspects of sound analysis.
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Record 6 of 9
Title: CENTER SURROUND ORGANIZATION OF AUDITORY RECEPTIVE FIELDS IN THE OWL
Author(s): KNUDSEN E I; KONISHI M
Source: Science (Washington D C) 202 (4369) : 778-780 1978
Abstract: The spatial receptive fields of specialized auditory units
in the midbrain of the barn owl (Tyto abla) contained 2 functionally
antagonistic areas: an excitatory center and an inhibitory surround.
The response of these units represented the balance of acoustic
activation of the 2 areas, which in turn depended upon the location,
intensity and spectral content of the sound stimulus.
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Record 7 of 9
Title: A MAP OF AUDITORY SPACE IN THE MID BRAIN OF THE OWL
Author(s): KNUDSEN E I; KONISHI M
Source: Journal of the Acoustical Society of America 62 (SUPPL 1) : S85 1977
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Record 8 of 9
Title: A NEURAL MAP OF AUDITORY SPACE IN THE OWL
Author(s): KNUDSEN E I; KONISHI M
Source: Science (Washington D C) 200 (4343) : 795-797 1978
Abstract: Auditory units that responded to sound only when it
originated from a limited area of space were found in the lateral and
anterior portions of the midbrain auditory nucleus of the owl (Tyto
alba). The areas of space to which these units responded (their
receptive fields) were largely independent of the nature and intensity
of the sound stimulus. The units were arranged systematically within
the midbrain auditory nucleus according to the relative locations of
their receptive fields, thus creating a physiological map of auditory
space.
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Record 9 of 9
Title: RECEPTIVE FIELDS OF AUDITORY NEURONS IN THE OWL
Author(s): KNUDSEN E I; KONISHI M; PETTIGREW J D
Source: Science (Washington D C) 198 (4323) : 1278-1280 1977
Abstract: The influence of sound location on the responses of auditory
neurons in the forebrain of the owl (Tyto alba) was studied directly
by using a remotely controlled, movable sound source under free-field,
anechoic conditions. Some auditory neurons demonstrated well-defined
receptive fields that were restricted both in elevation and in azimuth
and relatively independent of the intensity and the nature of the
sound stimulus. The majority of the fields were located frontally and
contralateral to the recording site.
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