Inferior colliculus. II. Development of tuning characteristics and tonotopic organization in central nucleus of the neonatal cat

1975 ◽  
Vol 38 (5) ◽  
pp. 1208-1216 ◽  
Author(s):  
L. M. Aitkin ◽  
D. R. Moore
Keyword(s):  
Inferior Colliculus ◽  
Tuning Curve ◽  
External Auditory Meatus ◽  
Auditory Pathway ◽  
Central Nucleus ◽  
Synaptic Density ◽  
Tonotopic Organization ◽  
Tuning Curves ◽  
Sharp Form ◽  
Cochlear Development

Tuning curves were measured for 65 units in the inferior colliculus of seven anesthetized kittens aged from 6 to 28 days. At 2 days of age the inferior colliculus was divisible into central, pericentral, and external nuclei. Evidence was found for broader tuning curves to occur in the pericentral nucleus compared with the central nucleus, as has been observed in the adult. The middle ear was filled with serous fluid to 6 days, while the external auditory meatus remained collapsed until 10 days. Central nucleus tuning curves in kittens were relatively flat with high thresholds. Best-frequency thresholds diminished from a mean of near 100 dB SPL at 6-11 days to near 50 dB in the adult. The marked drop in thresholds between days 22 and 21 led to the adoption of the sharp form of tuning curve common for adults. Tonotopic organization of the central nucleus was clear at day 11. Speculations were advanced about the dependence of central auditory maturations on cochlear development, axon myelination in the auditory pathway, and changes in synaptic density as a function of age.

Corticofugal Shaping of Frequency Tuning Curves in the Central Nucleus of the Inferior Colliculus of Mice

2005 ◽  
Vol 93 (1) ◽  
pp. 71-83 ◽  
Author(s):  
Jun Yan ◽  
Yunfeng Zhang ◽  
Günter Ehret
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Cortical Neurons ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Primary Auditory Cortex ◽  
Nerve Fibers ◽  
Cortical Activation ◽  
Central Nucleus ◽  
Tuning Curves

Plasticity of the auditory cortex can be induced by conditioning or focal cortical stimulation. The latter was used here to measure how stimulation in the tonotopy of the mouse primary auditory cortex influences frequency tuning in the midbrain central nucleus of the inferior colliculus (ICC). Shapes of collicular frequency tuning curves (FTCs) were quantified before and after cortical activation by measuring best frequencies, FTC bandwidths at various sound levels, level tolerance, Q-values, steepness of low- and high-frequency slopes, and asymmetries. We show here that all of these measures were significantly changed by focal cortical activation. The changes were dependent not only on the relationship of physiological properties between the stimulated cortical neurons and recorded collicular neurons but also on the tuning curve class of the collicular neuron. Cortical activation assimilated collicular FTC shapes; sharp and broad FTCs were changed to the shapes comparable to those of auditory nerve fibers. Plasticity in the ICC was organized in a center (excitatory)-surround (inhibitory) way with regard to the stimulated location (i.e., the frequency) of cortical tonotopy. This ensures, together with the spatial gradients of distribution of collicular FTC shapes, a sharp spectral filtering at the core of collicular frequency-band laminae and an increase in frequency selectivity at the periphery of the laminae. Mechanisms of FTC plasticity were suggested to comprise both corticofugal and local ICC components of excitatory and inhibitory modulation leading to a temporary change of the balance between excitation and inhibition in the ICC.

scholarly journals Frequency-Specific Effects on Cochlear Responses During Activation of the Inferior Colliculus in the Guinea Pig

2004 ◽  
Vol 91 (5) ◽  
pp. 2185-2193 ◽  
Author(s):  
Y. Ota ◽  
D. L. Oliver ◽  
D. F. Dolan
Keyword(s):  
Electrical Stimulation ◽  
Inferior Colliculus ◽  
Auditory System ◽  
Auditory Pathway ◽  
Central Nucleus ◽  
Frequency Effect ◽  
Tuning Curves ◽  
Specific Effects ◽  
Main Input

The inferior colliculus (IC) is a major processing center in the ascending auditory pathway. The role of the IC in the descending efferent auditory system is less clear. Although the IC central nucleus (ICC) is the major relay station for the ascending auditory pathways, the IC's cortex receives its main input from the neocortex and nonauditory sources. The goal of this study was to determine if the IC subdivisions had different functions in the descending efferent auditory system. IC subdivisions were identified by their tuning curves evoked by tone stimulation, and the effects of localized electrical stimulation on the cochlear whole-nerve action potential (CAP). Sharp tuning curves were obtained from ICC in contrast to broad tuning curves from the lateral, external cortex. Electrical stimulation within the central nucleus had a sharply tuned effect on the CAP. The frequency region affected within the cochlea closely matched the best frequency of local cells within the central nucleus. The effect of electrical stimulation within the lateral, external cortex on the CAP was smaller in comparison to central nucleus stimulation. Similar to the broad tuning of cells within the lateral cortex, electrical stimulation had a broad frequency effect on CAP thresholds.

Observations on Tonotopic Organization within the Rat Inferior Colliculus Using 2-Deoxy-D[1-3H] Glucose

1982 ◽  
Vol 90 (6) ◽  
pp. 795-800 ◽  
Author(s):  
James R. Coleman ◽  
Maurice Campbell ◽  
William J. Clerici
Keyword(s):  
Inferior Colliculus ◽  
Pure Tone ◽  
Central Nucleus ◽  
Banding Patterns ◽  
Tonotopic Organization ◽  
Marking Technique

Tonotopic organization is a major feature of central auditory structures. The tritiated 2-deoxyglucose metabolic marking technique is demonstrated to be useful for visualizing isofrequency contours in the rat inferior colliculus. Following pure-tone stimulation, the central nucleus of the inferior colliculus shows discrete, prominent banding patterns and a well-organized tonotopic arrangement.

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 Neural population encoding and decoding of sound source location across sound level in the rabbit inferior colliculus

2016 ◽  
Vol 115 (1) ◽  
pp. 193-207 ◽  
Author(s):  
Mitchell L. Day ◽  
Bertrand Delgutte
Keyword(s):  
Inferior Colliculus ◽  
Sound Source ◽  
Auditory Pathway ◽  
Relevant Information ◽  
Sound Level ◽  
Neural Population ◽  
Linear Transformations ◽  
Tuning Curves ◽  
Azimuthal Position ◽  
Sound Levels

At lower levels of sensory processing, the representation of a stimulus feature in the response of a neural population can vary in complex ways across different stimulus intensities, potentially changing the amount of feature-relevant information in the response. How higher-level neural circuits could implement feature decoding computations that compensate for these intensity-dependent variations remains unclear. Here we focused on neurons in the inferior colliculus (IC) of unanesthetized rabbits, whose firing rates are sensitive to both the azimuthal position of a sound source and its sound level. We found that the azimuth tuning curves of an IC neuron at different sound levels tend to be linear transformations of each other. These transformations could either increase or decrease the mutual information between source azimuth and spike count with increasing level for individual neurons, yet population azimuthal information remained constant across the absolute sound levels tested (35, 50, and 65 dB SPL), as inferred from the performance of a maximum-likelihood neural population decoder. We harnessed evidence of level-dependent linear transformations to reduce the number of free parameters in the creation of an accurate cross-level population decoder of azimuth. Interestingly, this decoder predicts monotonic azimuth tuning curves, broadly sensitive to contralateral azimuths, in neurons at higher levels in the auditory pathway.

scholarly journals Emergence of Multiplicative Auditory Responses in the Midbrain of the Barn Owl

2007 ◽  
Vol 98 (3) ◽  
pp. 1181-1193 ◽  
Author(s):  
Brian J. Fischer ◽  
José Luis Peña ◽  
Masakazu Konishi
Keyword(s):  
Inferior Colliculus ◽  
Interaural Time Difference ◽  
Extracellular Recording ◽  
Auditory Pathway ◽  
Barn Owl ◽  
Central Nucleus ◽  
Interaural Level Difference ◽  
Tyto Alba ◽  
Neural Responses ◽  
Auditory Responses

Space-specific neurons in the barn owl's auditory space map gain spatial selectivity through tuning to combinations of the interaural time difference (ITD) and interaural level difference (ILD). The combination of ITD and ILD in the subthreshold responses of space-specific neurons in the external nucleus of the inferior colliculus (ICx) is well described by a multiplication of ITD- and ILD-dependent components. It is unknown, however, how ITD and ILD are combined at the site of ITD and ILD convergence in the lateral shell of the central nucleus of the inferior colliculus (ICcl) and therefore whether ICx is the first site in the auditory pathway where multiplicative tuning to ITD- and ILD-dependent signals occurs. We used extracellular recording of single neurons to determine how ITD and ILD are combined in ICcl of the anesthetized barn owl ( Tyto alba). A comparison of additive, multiplicative, and linear-threshold models of neural responses shows that ITD and ILD are combined nonlinearly in ICcl, but the interaction of ITD and ILD is not uniformly multiplicative over the sample. A subset (61%) of the neural responses is well described by the multiplicative model, indicating that ICcl is the first site where multiplicative tuning to ITD- and ILD-dependent signals occurs. ICx, however, is the first site where multiplicative tuning is observed consistently. A network model shows that a linear combination of ICcl responses to ITD–ILD pairs is sufficient to produce the multiplicative subthreshold responses to ITD and ILD seen in ICx.

Neural Mechanisms Underlying Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Inferior Colliculus of the Pallid Bat

2006 ◽  
Vol 96 (3) ◽  
pp. 1320-1336 ◽  
Author(s):  
Zoltan M. Fuzessery ◽  
Marlin D. Richardson ◽  
Michael S. Coburn
Keyword(s):  
Inferior Colliculus ◽  
High Frequency ◽  
Tuning Curve ◽  
Low Frequency ◽  
Shape Selectivity ◽  
Similar Rate ◽  
Central Nucleus ◽  
Arrival Times ◽  
Sweep Direction ◽  
Pallid Bat

This study describes mechanisms that underlie neuronal selectivity for the direction and rate of frequency-modulated sweeps in the central nucleus of the inferior colliculus (ICC) of the pallid bat ( Antrozous pallidus). This ICC contains a high percentage of neurons (66%) that respond selectively to the downward sweep direction of the bat's echolocation pulse. Some (19%) are specialists that respond only to downward sweeps. Most neurons (83%) are also tuned to sweep rates. A two-tone inhibition paradigm was used to describe inhibitory mechanisms that shape selectivity for sweep direction and rate. Two different mechanisms can create similar rate tuning. The first is an early on-best frequency inhibition that shapes duration tuning, which in turn determines rate tuning. In most neurons that are not duration tuned, a delayed high-frequency inhibition creates rate tuning. These neurons respond to fast sweep rates, but are inhibited as rate slows, and delayed inhibition overlaps excitation. In these neurons, starting a downward sweep within the excitatory tuning curve eliminates rate tuning. However, if rate tuning is shaped by duration tuning, this manipulation has no effect. Selectivity for the downward sweep direction is created by an early low-frequency inhibition that prevents responses to upward sweeps. In addition to this asymmetry in arrival times of low- and high-frequency inhibitions, the bandwidth of the low-frequency sideband was broader. Bandwidth influences the arrival time of inhibition during an FM sweep because a broader sideband will be encountered sooner. These findings show that similar spectrotemporal filters can be created by different mechanisms.

Delay-Tuned Neurons in the Inferior Colliculus of the Mustached Bat: Implications for Analyses of Target Distance

1999 ◽  
Vol 82 (3) ◽  
pp. 1326-1338 ◽  
Author(s):  
Christine V. Portfors ◽  
Jeffrey J. Wenstrup
Keyword(s):  
Inferior Colliculus ◽  
Tuning Curve ◽  
Central Nucleus ◽  
Harmonic Frequency ◽  
High Frequency Signal ◽  
Response Properties ◽  
Mustached Bat ◽  
Medial Geniculate ◽  
Higher Harmonic ◽  
Delay Tuning

We examined response properties of delay-tuned neurons in the central nucleus of the inferior colliculus (ICC) of the mustached bat. In the mustached bat, delay-tuned neurons respond best to the combination of the first-harmonic, frequency-modulated (FM1) sweep in the emitted pulse and a higher harmonic frequency-modulated (FM2, FM3 or FM4) component in returning echoes and are referred to as FM-FM neurons. We also examined H1-CF2 neurons. H1-CF2 neurons responded to simultaneous presentation of the first harmonic (H1) in the emitted pulse and the second constant frequency (CF2) component in returning echoes. These neurons served as a comparison as they are thought to encode different features of sonar targets than FM-FM neurons. Only 7% of our neurons (14/198) displayed a single excitatory tuning curve. The rest of the neurons (184) displayed complex responses to sounds in two separate frequency bands. The majority (51%, 101) of neurons were facilitated by the combination of specific components in the mustached bat’s vocalizations. Twenty-five percent showed purely inhibitory interactions. The remaining neurons responded to two separate frequencies, without any facilitation or inhibition. FM-FM neurons (69) were facilitated by the FM1 component in the simulated pulse and a higher harmonic FM component in simulated echoes, provided the high-frequency signal was delayed the appropriate amount. The delay producing maximal facilitation (“best delay”) among FM-FM neurons ranged between 0 and 20 ms, corresponding to target distances ≤3.4 m. Sharpness of delay tuning varied among FM-FM neurons with 50% delay widths between 2 and 13 ms. On average, the facilitated responses of FM-FM neurons were 104% greater than the sum of the responses to the two signals alone. In comparing response properties of delay-tuned, FM-FM neurons in the ICC with those in the medial geniculate body (MGB) from other studies, we find that the range of best delays, sharpness of delay tuning and strength of facilitation are similar in the ICC and MGB. This suggests that by the level of the IC, the basic response properties of FM-FM neurons are established, and they do not undergo extensive transformations with ascending auditory processing.

Responses to Social Vocalizations in the Inferior Colliculus of the Mustached Bat Are Influenced by Secondary Tuning Curves

2007 ◽  
Vol 98 (6) ◽  
pp. 3461-3472 ◽  
Author(s):  
Lars Holmstrom ◽  
Patrick D. Roberts ◽  
Christine V. Portfors
Keyword(s):  
Inferior Colliculus ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Extended Model ◽  
Complex Frequency ◽  
Neural Responses ◽  
Tone Frequency ◽  
Tuning Curves ◽  
Mustached Bat ◽  
Dual Functions

Neurons in the inferior colliculus (IC) of the mustached bat integrate input from multiple frequency bands in a complex fashion. These neurons are important for encoding the bat's echolocation and social vocalizations. The purpose of this study was to quantify the contribution of complex frequency interactions on the responses of IC neurons to social vocalizations. Neural responses to single tones, two-tone pairs, and social vocalizations were recorded in the IC of the mustached bat. Three types of data driven stimulus-response models were designed for each neuron from single tone and tone pair stimuli to predict the responses of individual neurons to social vocalizations. The first model was generated only using the neuron's primary frequency tuning curve, whereas the second model incorporated the entire hearing range of the animal. The extended model often predicted responses to many social vocalizations more accurately for multiply tuned neurons. One class of multiply tuned neuron that likely encodes echolocation information also responded to many of the social vocalizations, suggesting that some neurons in the mustached bat IC have dual functions. The third model included two-tone frequency tunings of the neurons. The responses to vocalizations were better predicted by the two-tone models when the neuron had inhibitory frequency tuning curves that were not near the neuron's primary tuning curve. Our results suggest that complex frequency interactions in the IC determine neural responses to social vocalizations and some neurons in IC have dual functions that encode both echolocation and social vocalization signals.

scholarly journals Multiple sounds degrade the frequency representation in monkey inferior colliculus

2020 ◽  
Author(s):  
Shawn M. Willett ◽  
Jennifer M. Groh
Keyword(s):  
Maximum Likelihood ◽  
Firing Rate ◽  
Inferior Colliculus ◽  
Frequency Tuning ◽  
Tuning Curve ◽  
Response Functions ◽  
Tuning Curves ◽  
Frequency Representation ◽  
Simultaneous Sounds ◽  
Alternative Theories

AbstractHow we distinguish multiple simultaneous stimuli is uncertain, particularly given that such stimuli sometimes recruit largely overlapping populations of neurons. One hypothesis is that tuning curves might change to limit the number of stimuli driving any given neuron when multiple stimuli are present. To test this hypothesis, we recorded the activity of neurons in the inferior colliculus while monkeys localized either one or two simultaneous sounds differing in frequency. Although monkeys easily distinguished simultaneous sounds (∼90% correct performance), the frequency tuning of inferior colliculus neurons on dual sound trials did not improve in any obvious way. Frequency selectivity was degraded on dual sound trials compared to single sound trials: tuning curves broadened, and frequency accounted for less of the variance in firing rate. These tuning curve changes led a maximum-likelihood decoder to perform worse on dual sound trials than on single sound trials. These results fail to support the hypothesis that changes in frequency response functions serve to reduce the overlap in the representation of simultaneous sounds. Instead these results suggest alternative theories, such as recent evidence of alternations in firing rate between the rates corresponding to each of the two stimuli, offer a more promising approach.

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