Auditory localization: role of auditory pathways in brain stem of the cat

1975 ◽  
Vol 38 (4) ◽  
pp. 842-858 ◽  
Author(s):  
J. H. Casseday ◽  
W. D. Neff
Keyword(s):  
Brain Stem ◽  
Inferior Colliculus ◽  
Auditory System ◽  
Superior Olivary Complex ◽  
Medial Superior Olive ◽  
Lateral Lemniscus ◽  
Localization Accuracy ◽  
Before And After ◽  
Localization Ability ◽  
Trapezoid Body

Cats were trained to localize sound in space. The animals' localization accuracy was determined before and after one of the following operations: 1) transection of the trapezoid body, 2) unilateral and 3) bilateral transection of the lateral lemniscus, 4) unilateral and 5) bilateral transection of the brachium of the inferior colliculus. The results after bilateral transections of the lateral lemniscus and the one deep bilateral transection of the brachium of the inferior colliculus indicate that some portion of the ascending auditory system must be intact above the medulla for an animal to be able to localize sound. A small loss in accuracy of localization was found after unilateral transection of the lateral lemniscus or brachium of the inferior colliculus. This loss, when compared with the much larger loss that monaural animals show, is an indication that binaural analysis, important for sound localization, occurs at the level of the medulla. Some transections of the trapezoid body resulted in a deficit in localization ability that appeared to be complete and permanent. The position of the lesions in the trapezoid body indicated that important encoding of the binaural cues to localization most likely occurs at the superior olivary complex, probably at the medial superior olive. But the trapezoid body or other commissures of the brain stem auditory system are probably also involved in transmission of information necessary for localization to higher centers.

scholarly journals Physiological and anatomical investigation of the auditory brainstem in the Fat-tailed Dunnart (Sminthopsis crassicaudata)

2019 ◽  
Author(s):  
Andrew Garrett ◽  
Virginia Lannigan ◽  
Nathanael Yates ◽  
Jennifer Rodger ◽  
Wilhelmina Mulders
Keyword(s):  
Auditory System ◽  
Mammalian Species ◽  
Auditory Brainstem ◽  
Auditory Brainstem Responses ◽  
Superior Olivary Complex ◽  
Medial Superior Olive ◽  
Superior Olive ◽  
Medial Nucleus ◽  
Sminthopsis Crassicaudata ◽  
Nissl Stain

The fat-tailed Dunnart (Sminthopsis crassicaudata) is a small (10-20g) native marsupial endemic to the south west of Western Australia. Currently little is known about the auditory capabilities of the dunnart, and of marsupials in general. Consequently, this study sought to investigate several electrophysiological and anatomical properties of the dunnart auditory system. Auditory brainstem responses (ABR) were recorded to brief (5ms) tone pips at a range of frequencies (4-47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. Morphological observations (Nissl stain) revealed that the auditory structures thought to contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior olive. This study is the first to show functional and anatomical aspects of the lower part of the auditory system in the Fat-tailed Dunnart.

The Brain Stem Evoked Response and Medial Nucleus of the Trapezoid Body

1994 ◽  
Vol 110 (1) ◽  
pp. 84-92 ◽  
Author(s):  
Chiyeko Tsuchitani
Keyword(s):  
Brain Stem ◽  
Action Potentials ◽  
Stimulus Onset ◽  
Evoked Response ◽  
Superior Olivary Complex ◽  
Lateral Superior Olive ◽  
Medial Nucleus ◽  
Brain Stem Evoked Response ◽  
The Brain ◽  
Trapezoid Body

Single-unit responses of cat superior olivary complex neurons to acoustic stimuli were examined to determine whether the units' action potentials were sufficiently synchronized to contribute to the brain stem evoked response. The medial nucleus of the trapezoid body and lateral superior olive are two major nuclei within the cat superior olivary complex. The first-spike discharge latencies of medial nucleus of the trapezoid body and lateral superior olivary neurons to monaural presentations of tone burst stimuli were measured as a function of stimulus level. Evidence is provided to support the hypotheses that in cat the medial nucleus of the trapezoid body may contribute directly to the monaural brain stem evoked response by producing action potentials synchronized to stimulus onset and may also contribute indirectly to the brain stem evoked response binaural difference wave bc by inhibiting the lateral superior olive unit excitatory responses synchronized to stimulus onset.

Interaural time and intensity coding in superior olivary complex and inferior colliculus of the echolocating bat Molossus ater

1985 ◽  
Vol 53 (1) ◽  
pp. 89-109 ◽  
Author(s):  
G. Harnischfeger ◽  
G. Neuweiler ◽  
P. Schlegel
Keyword(s):  
Inferior Colliculus ◽  
Stimulus Frequency ◽  
Stimulus Onset ◽  
Time Difference ◽  
Superior Olivary Complex ◽  
Inhibitory Input ◽  
Medial Superior Olive ◽  
Transient Time ◽  
Interaural Time Differences ◽  
Superior Olive

Single-unit responses to tonal stimulation with interaural disparities were recorded in the nuclei of the superior olivary complex (SOC) and the central nucleus of the inferior colliculus (ICC) of the echolocating bat, Molossus ater. Seventy-six units were recorded from the ICC and 74 from the SOC; of the SOC units, 31 were histologically verified in the medial superior olive (MSO), 10 in the lateral superior olive (LSO), and 33 in unidentified areas of the SOC. Best frequencies (BFs) of the units ranged from 10.3 to 89.6 kHz, and Q10 dB values ranged from 2 to 70 dB. Most ICC neurons responded phasically to stimulus onset and were either inhibitory/excitatory [I/E; (53)] or excitatory/excitatory [E/E; (21)] units. In the MSO, 23 units responded tonically and 7 phasically on, 18 were E/E or E/OF (facilitatory for other input) units, and 11 were I/E neurons. All LSO neurons responded in a "chopper" fashion, and the binaural neurons were E/I units. In E/E units the excitatory response to binaural stimulation was frequently larger than the sum of the monaurally evoked responses. Many neurons with E/I or I/E inputs had very steep binaural impulse-count functions and were sensitive to small interaural intensity differences. Twenty-eight units (24%) responded with a change in firing rate of at least 20% to interaural time differences of +/- 500 microseconds. Within this sample, 11 units (8 from ICC, 2 from MSO, and 1 from SOC) were sensitive to interaural time differences of only +/- 50 microseconds. Of these 11 units, 10 were I/E units responding phasically only to stimulus onset and were also sensitive to intensity differences (delta I), being suppressed completely by the inhibitory input over a delta I range of 20 dB or less. Of 117 units tested in the ICC and SOC nuclei, 86 units (76%) were not sensitive to interaural time disparities within +/- 500 microseconds. Because the BFs of these units sensitive to interaural transient time differences (delta t) ranged between 18 and 90 kHz, responses were elicited by pure tones, and responses did not change periodically with the period equal to that of the stimulus frequency, we conclude that the neurons reacted to interaural differences of stimulus-onset time (transient time difference) but not to phase differences (ongoing time difference). Sensitivity to interaural time differences was also correlated with interaural intensity differences.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Multiple Sources of Cholinergic Input to the Superior Olivary Complex

2021 ◽  
Vol 15 ◽  
Author(s):  
Nichole L. Beebe ◽  
Chao Zhang ◽  
R. Michael Burger ◽  
Brett R. Schofield
Keyword(s):  
Auditory System ◽  
Cholinergic Neurons ◽  
Auditory Brainstem ◽  
Cholinergic Innervation ◽  
Superior Olivary Complex ◽  
Multiple Sources ◽  
Cholinergic Modulation ◽  
Medial Nucleus ◽  
Trapezoid Body

The superior olivary complex (SOC) is a major computation center in the brainstem auditory system. Despite previous reports of high expression levels of cholinergic receptors in the SOC, few studies have addressed the functional role of acetylcholine in the region. The source of the cholinergic innervation is unknown for all but one of the nuclei of the SOC, limiting our understanding of cholinergic modulation. The medial nucleus of the trapezoid body, a key inhibitory link in monaural and binaural circuits, receives cholinergic input from other SOC nuclei and also from the pontomesencephalic tegmentum. Here, we investigate whether these same regions are sources of cholinergic input to other SOC nuclei. We also investigate whether individual cholinergic cells can send collateral projections bilaterally (i.e., into both SOCs), as has been shown at other levels of the subcortical auditory system. We injected retrograde tract tracers into the SOC in gerbils, then identified retrogradely-labeled cells that were also immunolabeled for choline acetyltransferase, a marker for cholinergic cells. We found that both the SOC and the pontomesencephalic tegmentum (PMT) send cholinergic projections into the SOC, and these projections appear to innervate all major SOC nuclei. We also observed a small cholinergic projection into the SOC from the lateral paragigantocellular nucleus of the reticular formation. These various sources likely serve different functions; e.g., the PMT has been associated with things such as arousal and sensory gating whereas the SOC may provide feedback more closely tuned to specific auditory stimuli. Further, individual cholinergic neurons in each of these regions can send branching projections into both SOCs. Such projections present an opportunity for cholinergic modulation to be coordinated across the auditory brainstem.

Binaural Response Properties of Low-Frequency Neurons in the Gerbil Dorsal Nucleus of the Lateral Lemniscus

2006 ◽  
Vol 96 (3) ◽  
pp. 1425-1440 ◽  
Author(s):  
Ida Siveke ◽  
Michael Pecka ◽  
Armin H. Seidl ◽  
Sylvie Baudoux ◽  
Benedikt Grothe
Keyword(s):  
Low Frequency ◽  
Superior Olivary Complex ◽  
Suitable Model ◽  
Medial Superior Olive ◽  
Lateral Lemniscus ◽  
Auditory Midbrain ◽  
Response Properties ◽  
Superior Olive ◽  
Dorsal Nucleus ◽  
Anatomical Evidence

Differences in intensity and arrival time of sounds at the two ears, interaural intensity and time differences (IID, ITD), are the chief cues for sound localization. Both cues are initially processed in the superior olivary complex (SOC), which projects to the dorsal nucleus of the lateral lemniscus (DNLL) and the auditory midbrain. Here we present basic response properties of low-frequency (<2 kHz) DNLL neurons and their binaural sensitivity to ITDs and IIDs in the anesthetized gerbil. We found many neurons showing binaural properties similar to those reported for SOC neurons. IID-properties were similar to that of the contralateral lateral superior olive (LSO). A majority of cells had an ITD sensitivity resembling that of either the ipsilateral medial superior olive (MSO) or the contralateral LSO. A smaller number of cells displayed intermediate types of ITD sensitivity. In neurons with MSO-like response ITDs that evoked maximal discharges were mostly outside of the range of ITDs the gerbil naturally experiences. The maxima of the first derivative of their ITD-functions (steepest slope), however, were well within the physiological range of ITDs. This finding is consistent with the concept of a population rather than a place code for ITDs. Moreover, we describe several other binaural properties as well as physiological and anatomical evidence for a small but significant input from the contralateral MSO. The large number of ITD-sensitive low-frequency neurons implicates a substantial role for the DNLL in ITD processing and promotes this nucleus as a suitable model for further studies on ITD-coding.

Functional Segregation of ITD Sensitivity in the Inferior Colliculus of Decerebrate Cats

2002 ◽  
Vol 88 (5) ◽  
pp. 2251-2261 ◽  
Author(s):  
Ramnarayan Ramachandran ◽  
Bradford J. May
Keyword(s):  
Parallel Processing ◽  
Brain Stem ◽  
Inferior Colliculus ◽  
Single Unit ◽  
Dorsal Cochlear Nucleus ◽  
Central Nucleus ◽  
Projection Neurons ◽  
Medial Superior Olive ◽  
Superior Olive ◽  
Decerebrate Cats

Decerebration allows single-unit responses in the central nucleus of the inferior colliculus (ICC) to be studied in the absence of anesthesia and descending efferent influences. When this procedure is applied to cats, three neural response types (V, I, and O) can be identified by distinct patterns of excitation and inhibition in pure-tone frequency-response maps. Similarities of the definitive response map features with those of projection neurons in the auditory brain stem have led to the proposal that the ICC response types are derived from different sources of ascending input that remain functionally segregated within the midbrain. Additional evidence for the existence of these hypothesized parallel processing pathways has been obtained in our previous investigations of the effects of interaural level differences, brain stem lesions, and pharmacological manipulations on physiologically classified units. This study extends our characterization of the functional segregation of single-unit activity in the ICC by investigating how sensitivity to interaural time differences (ITDs) is related to the response types that are observed in decerebrate cats. The results of these experiments support our parallel-processing model of the ICC by linking the ITD sensitivity of type V and I units to putative inputs from the medial superior olive and lateral superior olive and by showing that most type O units lack a systematic sensitivity to binaural temporal information presumably because their dominant ascending inputs arise from weakly binaural neurons in the dorsal cochlear nucleus.

scholarly journals Physiological and anatomical investigation of the auditory brainstem in the Fat-tailed Dunnart (Sminthopsis crassicaudata)

2019 ◽  
Author(s):  
Andrew Garrett ◽  
Virginia Lannigan ◽  
Nathanael Yates ◽  
Jennifer Rodger ◽  
Wilhelmina Mulders
Keyword(s):  
Auditory System ◽  
Mammalian Species ◽  
Auditory Brainstem ◽  
Auditory Brainstem Responses ◽  
Superior Olivary Complex ◽  
Medial Superior Olive ◽  
Superior Olive ◽  
Medial Nucleus ◽  
Sminthopsis Crassicaudata ◽  
Nissl Stain

The fat-tailed Dunnart (Sminthopsis crassicaudata) is a small (10-20g) native marsupial endemic to the south west of Western Australia. Currently little is known about the auditory capabilities of the dunnart, and of marsupials in general. Consequently, this study sought to investigate several electrophysiological and anatomical properties of the dunnart auditory system. Auditory brainstem responses (ABR) were recorded to brief (5ms) tone pips at a range of frequencies (4-47.5 kHz) and intensities to determine auditory brainstem thresholds. The dunnart ABR displayed multiple distinct peaks at all test frequencies, similar to other mammalian species. ABR showed the dunnart is most sensitive to higher frequencies increasing up to 47.5 kHz. Morphological observations (Nissl stain) revealed that the auditory structures thought to contribute to the first peaks of the ABR were all distinguishable in the dunnart. Structures identified include the dorsal and ventral subdivisions of the cochlear nucleus, including a cochlear nerve root nucleus as well as several distinct nuclei in the superior olivary complex, such as the medial nucleus of the trapezoid body, lateral superior olive and medial superior olive. This study is the first to show functional and anatomical aspects of the lower part of the auditory system in the Fat-tailed Dunnart.

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