Altered Spectral Localization Cues Disrupt the Development of the Auditory Space Map in the Superior Colliculus of the Ferret

1998 ◽  
Vol 79 (2) ◽  
pp. 1053-1069 ◽  
Author(s):  
Jan W. H. Schnupp ◽  
Andrew J. King ◽  
Simon Carlile
Keyword(s):  
Superior Colliculus ◽  
Critical Role ◽  
Free Field ◽  
Auditory Space ◽  
Spectral Cues ◽  
Sound Levels ◽  
Spectral Localization ◽  
Auditory Representation ◽  
Auditory Space Map ◽  
Monaural Spectral Cues

Schnupp, Jan W. H., Andrew J. King, and Simon Carlile. Altered spectral localization cues disrupt the development of the auditory space map in the superior colliculus of the ferret. J. Neurophysiol. 79: 1053–1069, 1998. Spectral localization cues provided by the outer ear are utilized in the construction of the auditory space map in the superior colliculus (SC). The role of the outer ear in the development of this map was examined by recording from the SC of anesthetized, adult ferrets in which the pinna and concha had been removed in infancy. The acoustical consequences of this procedure were assessed by recording outer ear impulse responses via a probe-tube microphone implanted in the wall of the ear canal. Both monaural and binaural spectral cues normally show a number of asymmetric features within the horizontal plane, which allow azimuthal locations on either side of the interaural axis to be discriminated. These features were eliminated or altered by chronic pinnectomy. The responses of auditory units in the SC to noise bursts presented in the free field were examined at sound levels of ∼10 and 25 dB above unit threshold. After bilateral pinnectomy, the representation of auditory space was severely degraded at both sound levels. In contrast to normal ferrets, many units had bilobed azimuthal response profiles, indicating that they were unable to resolve sound locations on either side of the interaural axis. There was also much less order in the distribution of best azimuths or elevations of those units that were tuned to a single direction. Some units were tuned to locations that extended much further into the hemifield ipsilateral to the recording side than the normal range of best azimuths. Unilateral removal of the outer ear, which disrupts the monaural spectral cues for one side only, had a much smaller effect on the development of the auditory representation. At supra- and near-threshold sound levels, the representation of sound azimuth in the SC on both sides of the brain was less scattered than that found after bilateral pinna removal. Nevertheless, units with bilobed responses, broader tuning, and inappropriate best azimuths were observed in both the left and right SC of ferrets in which the left pinna and concha had been removed in infancy. These data illustrate that the localization cues provided by the outer ear play a critical role in the development of the auditory space map in the SC. In contrast to other manipulations of either auditory or visual inputs, the map does not appear to adapt to the changes in spectral cues brought about by pinna removal, suggesting that residual binaural cues are, by themselves, insufficient for its normal maturation.

Topographic representation of auditory space in the superior colliculus of adult ferrets after monaural deafening in infancy

1994 ◽  
Vol 71 (1) ◽  
pp. 182-194 ◽  
Author(s):  
A. J. King ◽  
D. R. Moore ◽  
M. E. Hutchings
Keyword(s):  
Superior Colliculus ◽  
Free Field ◽  
Receptive Fields ◽  
Spatial Location ◽  
Stimulus Level ◽  
Sound Level ◽  
Lateral Side ◽  
Auditory Space ◽  
Sound Levels ◽  
Auditory Representation

1. We have investigated the role of monaural cues provided by the outer ear in the construction of a map of auditory space in the superior colliculus. Single-unit recordings were made from the superior colliculus of adult ferrets that were deprived of binaural inputs by surgically ablating the ipsilateral cochlea on postnatal day 21 or 24. 2. The spatial response properties of auditory units in the deeper layers of this nucleus were studied using white-noise bursts presented under free-field conditions in an anechoic chamber. The thresholds of the units recorded in the monaural ferrets were not significantly different from those recorded in the superior colliculus of normal adult ferrets. In both groups the unit thresholds varied by 30-50 dB in each region of the superior colliculus. 3. In normal and monaural ferrets the elevation tuning tended to be sharper than the azimuth tuning. At sound levels of approximately 10 dB above threshold the auditory units recorded in both groups of animals were tuned to a specific region of space that was restricted in azimuth and elevation. The spatial location at which the maximum response was obtained (auditory best position) varied topographically in azimuth along the rostrocaudal axis of the nucleus and in elevation along the mediolateral axis. 4. The azimuthal distribution of best positions associated with each recording location in the superior colliculus of the monaural ferrets and the alignment between this dimension of the auditory map and that of the visual map in the overlying superficial layers were no different from those found at corresponding near-threshold sound levels in normal ferrets. 5. Elevation spatial selectivity was examined in a smaller sample of units. Although elevation best positions shifted downward from the medial to the lateral side of the nucleus in both normal and monaural ferrets, we found that the topography of the auditory representation and its alignment with the visual representation were statistically different in the two groups of animals. 6. Increasing the sound level does not affect the representation of auditory space in normal ferrets. However, when the stimulus level presented to monoaural ferrets was increased, the receptive fields either expanded so that the responses were no longer tuned to any particular region of space, or the responses remained tuned but exhibited a marked shift in the value of the best position.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Spectral cues are necessary to encode azimuthal auditory space in the mouse superior colliculus

2019 ◽  
Author(s):  
Shinya Ito ◽  
Yufei Si ◽  
David A. Feldheim ◽  
Alan M. Litke
Keyword(s):  
Superior Colliculus ◽  
Critical Role ◽  
Receptive Fields ◽  
Spectral Structure ◽  
Topographic Map ◽  
Neural Encoding ◽  
Spectral Filtering ◽  
Auditory Space ◽  
Spectral Cues ◽  
Interaural Level Differences

AbstractSound localization plays a critical role in animal survival. Three cues can be used to compute sound direction: interaural timing differences (ITDs), interaural level differences (ILDs) and the direction-dependent spectral filtering by the head and pinnae (spectral cues). Little is known about how spectral cues contribute to the neural encoding of auditory space. Here we report on auditory space encoding in the mouse superior colliculus (SC). We show that the mouse SC contains neurons with spatially-restricted receptive fields (RFs) that form an azimuthal topographic map. We found that frontal RFs require spectral cues and lateral RFs require ILDs. The neurons with frontal RFs have frequency tunings that match the spectral structure of the specific head and pinna filter for sound coming from the front. These results demonstrate that patterned spectral cues in combination with ILDs give rise to the topographic map of azimuthal auditory space.

scholarly journals Spectral cues are necessary to encode azimuthal auditory space in the mouse superior colliculus

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Shinya Ito ◽  
Yufei Si ◽  
David A. Feldheim ◽  
Alan M. Litke
Keyword(s):  
Superior Colliculus ◽  
Auditory Space ◽  
Spectral Cues

Analysis of the superior colliculus auditory space map function in guinea pig behavior

1998 ◽  
Vol 23 (1) ◽  
pp. 23-40 ◽  
Author(s):  
Bettina Blatt ◽  
Eva von Linstow Roloff ◽  
Deborah J. Withington ◽  
Euan M. Macphail ◽  
Gernot Riedel
Keyword(s):  
Guinea Pig ◽  
Superior Colliculus ◽  
Auditory Space ◽  
Auditory Space Map ◽  
Map Function

Coding for Auditory Space in the Nucleus of the Brachium of the Inferior Colliculus in the Ferret

1997 ◽  
Vol 78 (5) ◽  
pp. 2717-2731 ◽  
Author(s):  
Jan W. H. Schnupp ◽  
Andrew J. King
Keyword(s):  
Inferior Colliculus ◽  
Free Field ◽  
Sound Level ◽  
Fine Tuning ◽  
Threshold Condition ◽  
Two Dimensional ◽  
Auditory Space ◽  
Sound Levels ◽  
Response Profiles ◽  
Near Threshold

Schnupp, Jan W. H. and Andrew J. King. Coding for auditory space in the nucleus of the brachium of the inferior colliculus in the ferret. J. Neurophysiol. 78: 2717–2731, 1997. The nucleus of the brachium of the inferior colliculus (BIN) projects topographically to the deeper layers of the superior colliculus (SC), which contain a two-dimensional map of auditory space. In this study, we have used broadband stimuli presented in the free field to investigate how auditory space is represented in the BIN of the ferret. Response latencies and temporal firing patterns were comparable with those in the SC, and both properties showed some variation with stimulus location. We obtained spatial response profiles at two sound levels (5–15 and 25–35 dB above unit threshold). A large proportion of azimuth profiles (41% in the suprathreshold condition, 80% in the near-threshold condition) presented a single peak, indicating that they were tuned to single regions in space. For some of these units, the preferred speaker position varied considerably with sound level. The remaining units showed predominantly either broad “hemifield” or spatially ambiguous “bilobed” response profiles. At suprathreshold sound levels, the preferred azimuths of the tuned cells were ordered topographically along the rostrocaudal axis of the BIN, although this representation is considerably more scattered than that in the SC. In contrast to the SC, we observed no systematic variation in the distribution of near-threshold best azimuths, which were instead concentrated around the interaural axis in the contralateral hemifield. The azimuth tuning of individual units in the BIN was generally broader at both sound levels than that in the SC. Many units also were tuned for the elevation of the sound source (48% for supra-, 77% for near-threshold stimulation), but there was no evidence for topographic order in the distribution of preferred elevations within the BIN. These results suggest that the BIN sends inputs to the SC that are already selective for sound azimuth and elevation and that show some degree of topographic order for sound azimuth. These inputs then presumably are sharpened and their topography refined by a mechanism that is likely to involve convergence of other inputs and activity-dependent fine tuning of terminal connections, to result in a precise two-dimensional map of auditory space in the SC.

Effects of ear plugging on single-unit azimuth sensitivity in cat primary auditory cortex. II. Azimuth tuning dependent upon binaural stimulation

1994 ◽  
Vol 71 (6) ◽  
pp. 2194-2216 ◽  
Author(s):  
F. K. Samson ◽  
P. Barone ◽  
J. C. Clarey ◽  
T. J. Imig
Keyword(s):  
Auditory Cortex ◽  
Single Unit ◽  
Free Field ◽  
Primary Auditory Cortex ◽  
Excitatory Input ◽  
Spectral Cues ◽  
Binaural Stimulation ◽  
Monaural Stimulation ◽  
Monaural Spectral Cues ◽  
Interaural Level Differences

1. Single-unit recordings were carried out in primary auditory cortex (AI) of barbiturate-anesthetized cats. Observations were based on a sample of 131 high-best-frequency (> 5 kHz), azimuth-sensitive neurons. These were identified by their responses to a set of noise bursts, presented in the free field, that varied in azimuth and sound-pressure level (SPL). Each azimuth-sensitive neuron responded well to some levels at certain azimuths, but did not respond well to any level at other azimuths. 2. Unilateral ear plugging was used to infer each neuron's response to monaural stimulation. Ear plugs, produced by injecting a plastic ear mold compound into the external ear, attenuated sound reaching the tympanic membrane by 25–70 dB. The azimuth tuning of a large proportion of the sample (62/131), referred to as binaural directional (BD), was completely dependent upon binaural stimulation because with one ear plugged, these cells were insensitive to azimuth (either responded well at all azimuths or failed to respond at any azimuth) or in a few cases exhibited striking changes in location of azimuth function peaks. This report describes patterns of monaural responses and binaural interactions exhibited by BD neurons and relates them to each cell's azimuth and level tuning. The response of BD cells to ear plugging is consistent with the hypothesis that they derive azimuth tuning from interaural level differences present in noise bursts. Another component of the sample consisted of monaural directional (27/131) cells that derived azimuth tuning in part or entirely from monaural spectral cues. Cells in the remaining portion of the sample (42/131) responded too unreliably to permit specific conclusions. 3. Binaural interactions were inferred by statistical comparison of a cell's responses to monaural (unilateral plug) and binaural (no plug) stimulation. A larger binaural response than either monaural response was taken as evidence for binaural facilitation. A smaller binaural than monaural response was taken as evidence for binaural inhibition. Binaural facilitation was exhibited by 65% (40/62) of the BD sample (facilitatory cells). Many of these exhibited mixed interactions, i.e., binaural facilitation occurred in response to some azimuth-level combinations, and binaural inhibition to others. Binaural inhibition in the absence of binaural facilitation occurred in 35% (22/62) of the BD sample, a majority of which were EI cells, so called because they received excitatory (E) input from one ear (excitatory ear) and inhibitory (I) input from the other (inhibitory ear). One cell that exhibited binaural inhibition received excitatory input from each ear.(ABSTRACT TRUNCATED AT 400 WORDS)

Sign in / Sign up

Export Citation Format

Share Document