scholarly journals Local and Global Spatial Organization of Interaural Level Difference and Frequency Preferences in Auditory Cortex

2017 ◽  
Vol 28 (1) ◽  
pp. 350-369 ◽  
Author(s):  
Mariangela Panniello ◽  
Andrew J King ◽  
Johannes C Dahmen ◽  
Kerry M M Walker
Keyword(s):  
Auditory Cortex ◽  
Spatial Organization ◽  
Mammalian Species ◽  
Primary Auditory Cortex ◽  
Global Scale ◽  
Interaural Level Difference ◽  
Contralateral Ear ◽  
The Difference ◽  
Interaural Level Differences

Abstract Despite decades of microelectrode recordings, fundamental questions remain about how auditory cortex represents sound-source location. Here, we used in vivo 2-photon calcium imaging to measure the sensitivity of layer II/III neurons in mouse primary auditory cortex (A1) to interaural level differences (ILDs), the principal spatial cue in this species. Although most ILD-sensitive neurons preferred ILDs favoring the contralateral ear, neurons with either midline or ipsilateral preferences were also present. An opponent-channel decoder accurately classified ILDs using the difference in responses between populations of neurons that preferred contralateral-ear-greater and ipsilateral-ear-greater stimuli. We also examined the spatial organization of binaural tuning properties across the imaged neurons with unprecedented resolution. Neurons driven exclusively by contralateral ear stimuli or by binaural stimulation occasionally formed local clusters, but their binaural categories and ILD preferences were not spatially organized on a more global scale. In contrast, the sound frequency preferences of most neurons within local cortical regions fell within a restricted frequency range, and a tonotopic gradient was observed across the cortical surface of individual mice. These results indicate that the representation of ILDs in mouse A1 is comparable to that of most other mammalian species, and appears to lack systematic or consistent spatial order.

scholarly journals Role of Mammalian Auditory Cortex in the Perception of Elementary Sound Properties

2001 ◽  
Vol 85 (6) ◽  
pp. 2350-2358 ◽  
Author(s):  
Sanjiv K. Talwar ◽  
Pawel G. Musial ◽  
George L. Gerstein
Keyword(s):  
Auditory Cortex ◽  
Time Course ◽  
Auditory Evoked Potentials ◽  
Mammalian Species ◽  
Sound Intensity ◽  
Primary Auditory Cortex ◽  
Normal Hearing ◽  
Auditory Task ◽  
Experimental Conditions

Studies in several mammalian species have demonstrated that bilateral ablations of the auditory cortex have little effect on simple sound intensity and frequency-based behaviors. In the rat, for example, early experiments have shown that auditory ablations result in virtually no effect on the rat's ability to either detect tones or discriminate frequencies. Such lesion experiments, however, typically examine an animal's performance some time after recovery from ablation surgery. As such, they demonstrate that the cortex is not essential for simple auditory behaviors in the long run. Our study further explores the role of cortex in basic auditory perception by examining whether the cortex is normally involved in these behaviors. In these experiments we reversibly inactivated the rat primary auditory cortex (AI) using the GABA agonist muscimol, while the animals performed a simple auditory task. At the same time we monitored the rat's auditory activity by recording auditory evoked potentials (AEP) from the cortical surface. In contrast to lesion studies, the rapid time course of these experimental conditions preclude reorganization of the auditory system that might otherwise compensate for the loss of cortical processing. Soon after bilateral muscimol application to their AI region, our rats exhibited an acute and profound inability to detect tones. After a few hours this state was followed by a gradual recovery of normal hearing, first of tone detection and, much later, of the ability to discriminate frequencies. Surface muscimol application, at the same time, drastically altered the normal rat AEP. Some of the normal AEP components vanished nearly instantaneously to unveil an underlying waveform, whose size was related to the severity of accompanying behavioral deficits. These results strongly suggest that the cortex is directly involved in basic acoustic processing. Along with observations from accompanying multiunit experiments that related the AEP to AI neuronal activity, our results suggest that a critical amount of activity in the auditory cortex is necessary for normal hearing. It is likely that the involvement of the cortex in simple auditory perceptions has hitherto not been clearly understood because of underlying recovery processes that, in the long-term, safeguard fundamental auditory abilities after cortical injury.

Functional Organization of Squirrel Monkey Primary Auditory Cortex: Responses to Pure Tones

2001 ◽  
Vol 85 (4) ◽  
pp. 1732-1749 ◽  
Author(s):  
Steven W. Cheung ◽  
Purvis H. Bedenbaugh ◽  
Srikantan S. Nagarajan ◽  
Christoph E. Schreiner
Keyword(s):  
Receptive Field ◽  
Auditory Cortex ◽  
Squirrel Monkey ◽  
Spatial Organization ◽  
Functional Organization ◽  
Primary Auditory Cortex ◽  
Complex Sound ◽  
Sound Coding ◽  
Field Gradients ◽  
Pure Tones

The spatial organization of response parameters in squirrel monkey primary auditory cortex (AI) accessible on the temporal gyrus was determined with the excitatory receptive field to pure tone stimuli. Dense, microelectrode mapping of the temporal gyrus in four animals revealed that characteristic frequency (CF) had a smooth, monotonic gradient that systematically changed from lower values (0.5 kHz) in the caudoventral quadrant to higher values (5–6 kHz) in the rostrodorsal quadrant. The extent of AI on the temporal gyrus was ∼4 mm in the rostrocaudal axis and 2–3 mm in the dorsoventral axis. The entire length of isofrequency contours below 6 kHz was accessible for study. Several independent, spatially organized functional response parameters were demonstrated for the squirrel monkey AI. Latency, the asymptotic minimum arrival time for spikes with increasing sound pressure levels at CF, was topographically organized as a monotonic gradient across AI nearly orthogonal to the CF gradient. Rostral AI had longer latencies (range = 4 ms). Threshold and bandwidth co-varied with the CF. Factoring out the contribution of the CF on threshold variance, residual threshold showed a monotonic gradient across AI that had higher values (range = 10 dB) caudally. The orientation of the threshold gradient was significantly different from the CF gradient. CF-corrected bandwidth, residual Q10, was spatially organized in local patches of coherent values whose loci were specific for each monkey. These data support the existence of multiple, overlying receptive field gradients within AI and form the basis to develop a conceptual framework to understand simple and complex sound coding in mammals.

Sound-Induced Synchronization of Neural Activity Between and Within Three Auditory Cortical Areas

2000 ◽  
Vol 83 (5) ◽  
pp. 2708-2722 ◽  
Author(s):  
Jos J. Eggermont
Keyword(s):  
Auditory Cortex ◽  
Stimulus Intensity ◽  
Primary Auditory Cortex ◽  
Noise Burst ◽  
Stimulus Onset ◽  
Feature Binding ◽  
Intensity Level ◽  
Correlation Strength ◽  
The Difference ◽  
Peak Correlation

Neural synchrony within and between auditory cortical fields is evaluated with respect to its potential role in feature binding and in the coding of tone and noise sound pressure level. Simultaneous recordings were made in 24 cats with either two electrodes in primary auditory cortex (AI) and one in anterior auditory field (AAF) or one electrode each in AI, AAF, and secondary auditory cortex. Cross-correlograms (CCHs) for 1-ms binwidth were calculated for tone pips, noise bursts, and silence (i.e., poststimulus) as a function of intensity level. Across stimuli and intensity levels the total percentage of significant stimulus onset CCHs was 62% and that of significant poststimulus CCHs was 58% of 1,868 pairs calculated for each condition. The cross-correlation coefficient to stimulus onsets was higher for single-electrode pairs than for dual-electrode pairs and higher for noise bursts compared with tone pips. The onset correlation for single-electrode pairs was only marginally larger than the poststimulus correlation. For pairs from electrodes across area boundaries, the onset correlations were a factor 3–4 higher than the poststimulus correlations. The within-AI dual-electrode peak correlation was higher than that across areas, especially for spontaneous conditions. Correlation strengths for between area pairs were independent of the difference in characteristic frequency (CF), thereby providing a mechanism of feature binding for broadband sounds. For noise-burst stimulation, the onset correlation for between area pairs was independent of stimulus intensity regardless the difference in CF. In contrast, for tone-pip stimulation a significant dependence on intensity level of the peak correlation strength was found for pairs involving AI and/or AAF with CF difference less than one octave. Across all areas, driven rate, between-area peak correlation strength, or a combination of the two did not predict stimulus intensity. However, between-area peak correlation strength performs better than firing rate to decide if a stimulus is present or absent.

scholarly journals Experience-dependent overrepresentation of ultrasonic vocalization frequencies in the rat primary auditory cortex

2013 ◽  
Vol 110 (5) ◽  
pp. 1087-1096 ◽  
Author(s):  
Heesoo Kim ◽  
Shaowen Bao
Keyword(s):  
Auditory Cortex ◽  
Large Scale ◽  
Primary Auditory Cortex ◽  
Wide Band ◽  
Ultrasonic Vocalization ◽  
Ultrasonic Vocalizations ◽  
Central Nucleus ◽  
Frequency Range ◽  
Species Specific

Cortical sensory representation is highly adaptive to the environment, and prevalent or behaviorally important stimuli are often overrepresented. One class of such stimuli is species-specific vocalizations. Rats vocalize in the ultrasonic range >30 kHz, but cortical representation of this frequency range has not been systematically examined. We recorded in vivo cortical electrophysiological responses to ultrasonic pure-tone pips, natural ultrasonic vocalizations, and pitch-shifted vocalizations to assess how rats represent this ethologically relevant frequency range. We find that nearly 40% of the primary auditory cortex (AI) represents an octave-wide band of ultrasonic vocalization frequencies (UVFs; 32–64 kHz) compared with <20% for other octave bands <32 kHz. These UVF neurons respond preferentially and reliably to ultrasonic vocalizations. The UVF overrepresentation matures in the cortex before it develops in the central nucleus of inferior colliculus, suggesting a cortical origin and corticofugal influences. Furthermore, the development of cortical UVF overrepresentation depends on early acoustic experience. These results indicate that natural sensory experience causes large-scale cortical map reorganization and improves representations of species-specific vocalizations.

scholarly journals Local Homogeneity of Tonotopic Organization in the Primary Auditory Cortex of Marmosets

2018 ◽  
Author(s):  
Huan-huan Zeng ◽  
Jun-feng Huang ◽  
Ming Chen ◽  
Yun-qing Wen ◽  
Zhi-ming Shen ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Large Scale ◽  
Frequency Tuning ◽  
Primary Auditory Cortex ◽  
Primate Species ◽  
Tonotopic Organization ◽  
Brain Structure And Function ◽  
A1 Neurons ◽  
Cortical Regions

AbstractMarmoset has emerged as a useful non-human primate species for studying the brain structure and function. Previous studies on the mouse primary auditory cortex (A1) showed that neurons with preferential frequency tuning responses are mixed within local cortical regions, despite a large-scale tonotopic organization. Here we found that frequency tuning properties of marmoset A1 neurons are highly uniform within local cortical regions. We first defined tonotopic map of A1 using intrinsic optical imaging, and then used in vivo two-photon calcium imaging of large neuronal populations to examine the tonotopic preference at the single-cell level. We found that tuning preferences of layer 2/3 neurons were highly homogeneous over hundreds of micrometers in both horizontal and vertical directions. Thus, marmoset A1 neurons are distributed in a tonotopic manner at both macro- and microscopic levels. Such organization is likely to be important for the organization of auditory circuits in the primate brain.

scholarly journals Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

2007 ◽  
Vol 97 (2) ◽  
pp. 1413-1427 ◽  
Author(s):  
Hubert H. Lim ◽  
David J. Anderson
Keyword(s):  
Auditory Cortex ◽  
Inferior Colliculus ◽  
Spatial Organization ◽  
Medial Geniculate Body ◽  
Primary Auditory Cortex ◽  
Central Nucleus ◽  
Antidromic Activation ◽  
Antidromic Stimulation ◽  
Medial Geniculate ◽  
Layer V

The inferior colliculus (IC) is highly modulated by descending projections from higher auditory and nonauditory centers. Traditionally, corticofugal fibers were believed to project mainly to the extralemniscal IC regions. However, there is some anatomical evidence suggesting that a substantial number of fibers from the primary auditory cortex (A1) project into the IC central nucleus (ICC) and appear to be tonotopically organized. In this study, we used antidromic stimulation combined with other electrophysiological techniques to further investigate the spatial organization of descending fibers from A1 to the ICC in ketamine-anesthetized guinea pigs. Based on our findings, corticofugal fibers originate predominantly from layer V of A1, are amply scattered throughout the ICC and only project to ICC neurons with a similar best frequency (BF). This strict tonotopic pattern suggests that these corticofugal projections are involved with modulating spectral features of sound. Along the isofrequency dimension of the ICC, there appears to be some differences in projection patterns that depend on BF region and possibly isofrequency location within A1 and may be indicative of different descending coding strategies. Furthermore, the success of the antidromic stimulation method in our study demonstrates that it can be used to investigate some of the functional properties associated with corticofugal projections to the ICC as well as to other regions (e.g., medial geniculate body, cochlear nucleus). Such a method can address some of the limitations with current anatomical techniques for studying the auditory corticofugal system.

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