Development of output connections from the inferior colliculus to the optic tectum in barn owls

2003 ◽  
Vol 464 (4) ◽  
pp. 511-524 ◽  
Author(s):  
B�rbel Nieder ◽  
Hermann Wagner ◽  
Harald Luksch
Keyword(s):  
Inferior Colliculus ◽  
Optic Tectum ◽  
Barn Owls

Adaptive plasticity of the auditory space map in the optic tectum of adult and baby barn owls in response to external ear modification

1994 ◽  
Vol 71 (1) ◽  
pp. 79-94 ◽  
Author(s):  
E. I. Knudsen ◽  
S. D. Esterly ◽  
J. F. Olsen
Keyword(s):  
Spatial Pattern ◽  
Optic Tectum ◽  
Interaural Time Difference ◽  
Rate Of Change ◽  
Adaptive Plasticity ◽  
Interaural Level Difference ◽  
External Ear ◽  
Site Location ◽  
Physiological Range ◽  
Barn Owls

1. This study demonstrates the influence of experience on the establishment and maintenance of the auditory map of space in the optic tectum of the barn owl. Auditory experience was altered either by preventing the structures of the external ears (the facial ruff and preaural flaps) from appearing in baby barn owls (baby ruff-cut owls) or by removing these structures in adults (adult ruff-cut owls). These structures shape the binaural cues used for localizing sounds in both the horizontal and vertical dimensions. 2. The acoustic effects of removing the external ear structures were measured using probe tube microphones placed in the ear canals. In both baby and adult ruff-cut owls, the spatial pattern of binaural localization cues was dramatically different from normal: interaural level difference (ILD) changed with azimuth instead of with elevation, the rate of change of ILD across space was decreased relative to normal, and the rate of change of interaural time difference (ITD) across frontal space was increased relative to normal. 3. The neurophysiological representations of ITD and ILD in the optic tectum were measured before and > or = 3 mo after ruff removal in adults and beginning at 4.5 months of age in baby ruff-cut owls. Multiunit tuning to ITD and to ILD was measured using dichotic stimulation in ketamine-anesthetized owls. The tectal maps of ITD and ILD were reconstructed using visual receptive field location as a marker for recording site location in the optic tectum. 4. Adjustment of the tectal map of ITD to the altered spatial pattern of acoustic ITD was essentially complete in adults as well as in baby ruff-cut owls. This adjustment changed the magnification of ITD across the tectum, with resultant changes in ITD tuning at individual tectal sites of up to approximately 25 microseconds (approximately 5% of the physiological range) relative to normal values. 5. Adaptation of the tectal ILD map to the ruff-cut spatial pattern of acoustic ILD was substantial but clearly incomplete in both adult and baby ruff-cut owls. Although changes of up to approximately 15 dB (approximately 47% of the physiological range) relative to normal tuning were observed at certain tectal sites, the topography of the ILD map was always intermediate between normal and that predicted by the ruff-cut spatial pattern of acoustic ILD.(ABSTRACT TRUNCATED AT 400 WORDS)

Tuning to Interaural Time Difference and Frequency Differs Between the Auditory Arcopallium and the External Nucleus of the Inferior Colliculus

2009 ◽  
Vol 101 (5) ◽  
pp. 2348-2361 ◽  
Author(s):  
Katrin Vonderschen ◽  
Hermann Wagner
Keyword(s):  
Inferior Colliculus ◽  
Tuning Curve ◽  
Interaural Time Difference ◽  
Low Frequency ◽  
Steep Slope ◽  
Time Difference ◽  
Interaural Time Differences ◽  
Tuning Curves ◽  
Barn Owls ◽  
Zero Time

Barn owls process sound-localization information in two parallel pathways, the midbrain and the forebrain pathway. Exctracellular recordings of neural responses to auditory stimuli from far advanced stations of these pathways, the auditory arcopallium in the forebrain and the external nucleus of the inferior colliculus in the midbrain, demonstrated that the representations of interaural time difference and frequency in the forebrain pathway differ from those in the midbrain pathway. Specifically, low-frequency representation was conserved in the forebrain pathway, while it was lost in the midbrain pathway. Variation of interaural time difference yielded symmetrical tuning curves in the midbrain pathway. By contrast, the typical forebrain-tuning curve was asymmetric with a steep slope crossing zero time difference and a less-steep slope toward larger contralateral time disparities. Low sound frequencies contributed sensitivity to contralateral leading sounds underlying these asymmetries, whereas high frequencies enhanced the steepness of slopes at small interaural time differences. Furthermore, the peaks of time-disparity tuning curves were wider in the forebrain than in the midbrain. The distribution of the steepest slopes of best interaural time differences in the auditory arcopallium, but not in the external nucleus of the inferior colliculus, was centered at zero time difference. The distribution observed in the auditory arocpallium is reminiscent of the situation observed in small mammals. We speculate that the forebrain representation may serve as a population code supporting fine discrimination of central interaural time differences and coarse indication of laterality of a stimulus for large interaural time differences.

scholarly journals Comparison of Midbrain and Thalamic Space-Specific Neurons in Barn Owls

2006 ◽  
Vol 95 (2) ◽  
pp. 783-790 ◽  
Author(s):  
María Lucía Pérez ◽  
José Luis Peña
Keyword(s):  
Inferior Colliculus ◽  
Spatial Information ◽  
Receptive Fields ◽  
Stimulus Frequency ◽  
Auditory Pathway ◽  
Mammalian Brain ◽  
Neural Pathways ◽  
Spatial Cues ◽  
Auditory Space ◽  
Barn Owls

Spatial receptive fields of neurons in the auditory pathway of the barn owl result from the sensitivity to combinations of interaural time (ITD) and level differences across stimulus frequency. Both the forebrain and tectum of the owl contain such neurons. The neural pathways, which lead to the forebrain and tectal representations of auditory space, separate before the midbrain map of auditory space is synthesized. The first nuclei that belong exclusively to either the forebrain or the tectal pathways are the nucleus ovoidalis (Ov) and the external nucleus of the inferior colliculus (ICx), respectively. Both receive projections from the lateral shell subdivision of the inferior colliculus but are not interconnected. Previous studies indicate that the owl's tectal representation of auditory space is different from those found in the owl's forebrain and the mammalian brain. We addressed the question of whether the computation of spatial cues in both pathways is the same by comparing the ITD tuning of Ov and ICx neurons. Unlike in ICx, the relationship between frequency and ITD tuning had not been studied in single Ov units. In contrast to the conspicuous frequency independent ITD tuning of space-specific neurons of ICx, ITD selectivity varied with frequency in Ov. We also observed that the spatially tuned neurons of Ov respond to lower frequencies and are more broadly tuned to ITD than in ICx. Thus there are differences in the integration of frequency and ITD in the two sound-localization pathways. Thalamic neurons integrate spatial information not only within a broader frequency band but also across ITD channels.

scholarly journals GABAergic Inhibition Influences Auditory Motion-Direction Sensitivity in Barn Owls

1998 ◽  
Vol 80 (1) ◽  
pp. 172-185 ◽  
Author(s):  
Dirk Kautz ◽  
Hermann Wagner
Keyword(s):  
Inferior Colliculus ◽  
Visual Motion ◽  
Gabaergic Inhibition ◽  
Auditory Motion ◽  
Cellular Mechanisms ◽  
Motion Direction ◽  
Inhibitory Mechanisms ◽  
Barn Owls ◽  
Gaba Antagonist ◽  
Direction Sensitivity

Kautz, Dirk and Hermann Wagner. GABAergic inhibition influences auditory motion-direction sensitivity in barn owls. J. Neurophysiol. 80: 172–185, 1998. Many neurons in the barn owl's inferior colliculus (IC) exhibit auditory motion-direction sensitivity (MDS), i.e., they respond more to motion of a sound source in one direction than to motion in the opposite direction. We investigated the cellular mechanisms underlying the phenomenon of auditory MDS by microiontophoretically applying γ-aminobutyric acid (GABA) or the GABA-antagonist bicuculline methiodide (BMI) while recording from neurons in the owl's midbrain. In most cases GABA reduced the overall firing rate, whereas BMI increased it. In addition, 29% of the motion-direction–sensitive cells completely lost their selectivity for the direction of auditory movement during administration of BMI. It had been proposed that auditory MDS in the owl is due to inhibition. The present results show that GABAergic inhibition plays a role in the strengthening of MDS. We discuss the data within the framework of the acoustic motion detector and with respect to microiontophoretic studies on visual motion detection and on inhibitory mechanisms in the inferior colliculus.

A novel relay nucleus between the inferior colliculus and the optic tectum in the chicken (Gallus gallus)

2016 ◽  
Vol 525 (3) ◽  
pp. 513-534 ◽  
Author(s):  
Bertram Niederleitner ◽  
Cristian Gutierrez-Ibanez ◽  
Quirin Krabichler ◽  
Stefan Weigel ◽  
Harald Luksch
Keyword(s):  
Inferior Colliculus ◽  
Optic Tectum ◽  
Gallus Gallus ◽  
Relay Nucleus

Dynamics of visually guided auditory plasticity in the optic tectum of the barn owl

1995 ◽  
Vol 73 (2) ◽  
pp. 595-614 ◽  
Author(s):  
M. S. Brainard ◽  
E. I. Knudsen
Keyword(s):  
Visual Field ◽  
Optic Tectum ◽  
Visual Experience ◽  
Normal Values ◽  
Interaural Time Difference ◽  
Receptive Fields ◽  
Visually Guided ◽  
Barn Owls ◽  
Tectal Neurons ◽  
The Right

1. In the optic tectum of normal barn owls, bimodal (auditory-visual) neurons are tuned to the values of interaural time difference (ITD) that are produced by sounds at the locations of their visual receptive fields (VRFs). The auditory tuning of tectal neurons is actively guided by visual experience during development: in the tectum of adult owls reared with an optically displaced visual field, neurons are tuned to abnormal values of ITD that are close to the values produced by sounds at the locations of their optically displaced VRFs. In this study we investigated the dynamics of this experience-dependent plasticity. 2. Owls were raised from shortly after eye-opening (14-22 days of age) with prismatic spectacles that displaced the visual field to the right or left. Starting at approximately 60 days of age, multiunit recordings were made to assess the tuning of tectal neurons to ITD presented via earphones. In the earliest recording sessions (ages 60-80 days), ITD tuning was often close to normal, even though the majority of the owls' previous experience was with an altered correspondence between ITD values and VRF locations. Subsequently, over a period of weeks, responses to the normal range of ITDs were gradually eliminated while responses to values of ITD corresponding with the optically displaced VRF were acquired. 3. At intermediate stages in this process, the ITD tuning at many sites became abnormally broad, so that responses were simultaneously present to both normal values of ITD and to values corresponding with the optically displaced VRF. At this stage the latencies and durations of newly acquired responses systematically exceeded the latencies and durations of the responses to normal values of ITD. 4. Dynamic changes in ITD tuning similar to those recorded in the optic tectum also occurred in the external nucleus of the inferior colliculus (ICX), which provides the major source of ascending auditory input to the tectum. 5. These results suggest the hypothesis that the neural selectivity for ITD in the barn owl's tectum is first established by vision-independent mechanisms and only subsequently calibrated by visual experience. This calibration involves both the elimination of responses to normal values of ITD and the visually guided acquisition of responses to novel values and can be accounted for by plasticity at the level of the ICX.

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