scholarly journals Role of Auditory Cortex in Sound Localization in the Midsagittal Plane

2007 ◽  
Vol 98 (3) ◽  
pp. 1763-1774 ◽  
Author(s):  
Jennifer K. Bizley ◽  
Fernando R. Nodal ◽  
Carl H. Parsons ◽  
Andrew J. King
Keyword(s):  
Auditory Cortex ◽  
Sound Localization ◽  
Primary Auditory Cortex ◽  
Midsagittal Plane ◽  
Spectral Localization ◽  
Approximate Location ◽  
Before And After ◽  
Significant Deficit ◽  
Vertical Localization

Although the auditory cortex is known to be essential for normal sound localization in the horizontal plane, its contribution to vertical localization has not so far been examined. In this study, we measured the acuity with which ferrets could discriminate between two speakers in the midsagittal plane before and after silencing activity bilaterally in the primary auditory cortex (A1). This was achieved either by subdural placement of Elvax implants containing the GABAA receptor agonist muscimol or by making aspiration lesions after determining the approximate location of A1 electrophysiologically. Psychometric functions and minimum audible angles were measured in the upper hemifield for 500-, 200-, and 40-ms noise bursts. Muscimol-Elvax inactivation of A1 produced a small but significant deficit in the animals’ ability to localize brief (40-ms) sounds, which was reversed after removal of the Elvax implants. A similar deficit in vertical localization was observed after bilateral aspiration lesions of A1, whereas performance at longer sound durations was unaffected. Another group of ferrets received larger lesions, encompassing both primary and nonprimary auditory cortical areas, and showed a greater deficit with performance being impaired for long- and short-duration (500- and 40-ms, respectively) stimuli. These data suggest that the integrity of the auditory cortex is required to successfully utilize spectral localization cues, which are thought to provide the basis for vertical localization, and that multiple cortical fields, including A1, contribute to this task.

scholarly journals Lesions of the Auditory Cortex Impair Azimuthal Sound Localization and Its Recalibration in Ferrets

2010 ◽  
Vol 103 (3) ◽  
pp. 1209-1225 ◽  
Author(s):  
Fernando R. Nodal ◽  
Oliver Kacelnik ◽  
Victoria M. Bajo ◽  
Jennifer K. Bizley ◽  
David R. Moore ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Sound Localization ◽  
Primary Auditory Cortex ◽  
Spatial Cues ◽  
Target Behavior ◽  
Long Duration ◽  
Orienting Behavior ◽  
Before And After ◽  
Bilateral Lesions

The role of auditory cortex in sound localization and its recalibration by experience was explored by measuring the accuracy with which ferrets turned toward and approached the source of broadband sounds in the horizontal plane. In one group, large bilateral lesions were made of the middle ectosylvian gyrus, where the primary auditory cortical fields are located, and part of the anterior and/or posterior ectosylvian gyrus, which contain higher-level fields. In the second group, the lesions were intended to be confined to primary auditory cortex (A1). The ability of the animals to localize noise bursts of different duration and level was measured before and after the lesions were made. A1 lesions produced a modest disruption of approach-to-target responses to short-duration stimuli (<500 ms) on both sides of space, whereas head orienting accuracy was unaffected. More extensive lesions produced much greater auditory localization deficits, again primarily for shorter sounds. In these ferrets, the accuracy of both the approach-to-target behavior and the orienting responses was impaired, and they could do little more than correctly lateralize the stimuli. Although both groups of ferrets were still able to localize long-duration sounds accurately, they were, in contrast to ferrets with an intact auditory cortex, unable to relearn to localize these stimuli after altering the spatial cues available by reversibly plugging one ear. These results indicate that both primary and nonprimary cortical areas are necessary for normal sound localization, although only higher auditory areas seem to contribute to accurate head orienting behavior. They also show that the auditory cortex, and A1 in particular, plays an essential role in training-induced plasticity in adult ferrets, and that this is the case for both head orienting responses and approach-to-target behavior.

Contribution of auditory cortex to sound localization in the monkey (Macaca mulatta)

1975 ◽  
Vol 38 (6) ◽  
pp. 1340-1358 ◽  
Author(s):  
H. Heffner ◽  
B. Masterton
Keyword(s):  
Auditory Cortex ◽  
Sound Localization ◽  
Macaca Mulatta ◽  
Primary Auditory Cortex ◽  
Sensory Discrimination

Monkeys with lesions of auditory cortex were tested for their ability to localize the source of brief sounds. Although those deprived of primary auditory cortex bilaterally were able to indicate the direction of a sound with near-normal acuity, they were unable to locate its source. This dissociation of abilities suggest that the role of auditory cortex in sound localization is not so much sensory or perceptual as it is auditomotor or associative. Thus, sound localization joins loudness, pitch, and most other traditional attributes of sound as dimensions whose discrimination does not depend on auditory cortex. The question would now seem to turn to whether or not auditory cortex is necessary for any sensory discrimination whatever.

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.

Correlation Between the Activity of Single Auditory Cortical Neurons and Sound-Localization Behavior in the Macaque Monkey

2000 ◽  
Vol 83 (5) ◽  
pp. 2723-2739 ◽  
Author(s):  
Gregg H. Recanzone ◽  
Darren C. Guard ◽  
Mimi L. Phan ◽  
Tien-I K. Su
Keyword(s):  
Auditory Cortex ◽  
Sound Localization ◽  
Cortical Neurons ◽  
Primary Auditory Cortex ◽  
Macaque Monkey ◽  
Auditory Space ◽  
Spatial Sensitivity ◽  
Acoustic Space ◽  
Localization Ability ◽  
Primate Cerebral Cortex

Lesion studies have indicated that the auditory cortex is crucial for the perception of acoustic space, yet it remains unclear how these neurons participate in this perception. To investigate this, we studied the responses of single neurons in the primary auditory cortex (AI) and the caudomedial field (CM) of two monkeys while they performed a sound-localization task. Regression analysis indicated that the responses of ∼80% of neurons in both cortical areas were significantly correlated with the azimuth or elevation of the stimulus, or both, which we term “spatially sensitive.” The proportion of spatially sensitive neurons was greater for stimulus azimuth compared with stimulus elevation, and elevation sensitivity was primarily restricted to neurons that were tested using stimuli that the monkeys also could localize in elevation. Most neurons responded best to contralateral speaker locations, but we also encountered neurons that responded best to ipsilateral locations and neurons that had their greatest responses restricted to a circumscribed region within the central 60° of frontal space. Comparing the spatially sensitive neurons with those that were not spatially sensitive indicated that these two populations could not be distinguished based on either the firing rate, the rate/level functions, or on their topographic location within AI. Direct comparisons between the responses of individual neurons and the behaviorally measured sound-localization ability indicated that proportionally more neurons in CM had spatial sensitivity that was consistent with the behavioral performance compared with AI neurons. Pooling the responses across neurons strengthened the relationship between the neuronal and psychophysical data and indicated that the responses pooled across relatively few CM neurons contain enough information to account for sound-localization ability. These data support the hypothesis that auditory space is processed in a serial manner from AI to CM in the primate cerebral cortex.

Role of the primary auditory cortex in auditory selective attention studied by whole-head neuromagnetometer

1998 ◽  
Vol 7 (2) ◽  
pp. 99-109 ◽  
Author(s):  
Naohito Fujiwara ◽  
Takashi Nagamine ◽  
Makoto Imai ◽  
Tomohiro Tanaka ◽  
Hiroshi Shibasaki
Keyword(s):  
Selective Attention ◽  
Auditory Cortex ◽  
Primary Auditory Cortex ◽  
Auditory Selective Attention

Contribution of auditory cortex to sound localization by the ferret (Mustela putorius)

1987 ◽  
Vol 57 (6) ◽  
pp. 1746-1766 ◽  
Author(s):  
G. L. Kavanagh ◽  
J. B. Kelly
Keyword(s):  
Auditory Cortex ◽  
Sound Localization ◽  
Horizontal Plane ◽  
Primary Auditory Cortex ◽  
Cortical Lesions ◽  
Mustela Putorius ◽  
Complete Destruction ◽  
Left And Right ◽  
The Right ◽  
Bilateral Lesions

Ferrets were tested in a semicircular apparatus to determine the effects of auditory cortical lesions on their ability to localize sounds in space. They were trained to initiate trials while facing forward in the apparatus, and sounds were presented from one of two loudspeakers located in the horizontal plane. Minimum audible angles were obtained for three different positions, viz., the left hemifield, with loudspeakers centered around -60 degrees azimuth; the right hemifield, with loudspeakers centered around +60 degrees azimuth; and the midline with loudspeakers centered around 0 degrees azimuth. Animals with large bilateral lesions had severe impairments in localizing a single click in the midline test. Following complete destruction of the auditory cortex performance was only marginally above the level expected by chance even at large angles of speaker separation. Severe impairments were also found in localization of single clicks in both left and right lateral fields. In contrast, bilateral lesions restricted to the primary auditory cortex resulted in minimal impairments in midline localization. The same lesions, however, produced severe impairments in localization of single clicks in both left and right lateral fields. Large unilateral lesions that destroyed auditory cortex in one hemisphere resulted in an inability to localize single clicks in the contralateral hemifield. In contrast, no impairments were found in the midline test or in the ipsilateral hemifield. Unilateral lesions of the primary auditory cortex resulted in severe contralateral field deficits equivalent to those seen following complete unilateral destruction of auditory cortex. No deficits were seen in either the midline or the ipsilateral tests.

scholarly journals The Role of Adaptation in Generating Monotonic Rate Codes in Auditory Cortex

2019 ◽  
Author(s):  
Jong Hoon Lee ◽  
Xiaoqin Wang ◽  
Daniel Bendor
Keyword(s):  
Auditory Cortex ◽  
Single Unit ◽  
Discharge Rate ◽  
Primary Auditory Cortex ◽  
Stimulus Presentation ◽  
Single Neurons ◽  
Short Term ◽  
Acoustic Stimuli ◽  
Biophysical Mechanism

AbstractIn primary auditory cortex, slowly repeated acoustic events are represented temporally by phase-locked activity of single neurons. Single-unit studies in awake marmosets (Callithrix jacchus) have shown that a sub-population of these neurons also monotonically increase or decrease their average discharge rate during stimulus presentation for higher repetition rates. Building on a computational single-neuron model that generates phase-locked responses with stimulus evoked excitation followed by strong inhibition, we find that stimulus-evoked short-term depression is sufficient to produce synchronized monotonic positive and negative responses to slowly repeated stimuli. By exploring model robustness and comparing it to other models for adaptation to such stimuli, we conclude that short-term depression best explains our observations in single-unit recordings in awake marmosets. Using this model, we emulated how single neurons could encode and decode multiple aspects of an acoustic stimuli with the monotonic positive and negative encoding of a given stimulus feature. Together, our results show that a simple biophysical mechanism in single neurons can allow a more complex encoding and decoding of acoustic stimuli.

Sound Localization Deficits During Reversible Deactivation of Primary Auditory Cortex and/or the Dorsal Zone

2008 ◽  
Vol 99 (4) ◽  
pp. 1628-1642 ◽  
Author(s):  
Shveta Malhotra ◽  
G. Christopher Stecker ◽  
John C. Middlebrooks ◽  
Stephen G. Lomber
Keyword(s):  
Auditory Cortex ◽  
Sound Localization ◽  
Primary Auditory Cortex ◽  
Noise Burst ◽  
Orienting Response ◽  
Error Rates ◽  
Broadband Noise ◽  
Physiological Data ◽  
Anterior Ectosylvian Sulcus ◽  
Auditory Field

We examined the contributions of primary auditory cortex (A1) and the dorsal zone of auditory cortex (DZ) to sound localization behavior during separate and combined unilateral and bilateral deactivation. From a central visual fixation point, cats learned to make an orienting response (head movement and approach) to a 100-ms broadband noise burst emitted from a central speaker or one of 12 peripheral sites (located in front of the animal, from left 90° to right 90°, at 15° intervals) along the horizontal plane. Following training, each cat was implanted with separate cryoloops over A1 and DZ bilaterally. Unilateral deactivation of A1 or DZ or simultaneous unilateral deactivation of A1 and DZ (A1/DZ) resulted in spatial localization deficits confined to the contralateral hemifield, whereas sound localization to positions in the ipsilateral hemifield remained unaffected. Simultaneous bilateral deactivation of both A1 and DZ resulted in sound localization performance dropping from near-perfect to chance (7.7% correct) across the entire field. Errors made during bilateral deactivation of A1/DZ tended to be confined to the same hemifield as the target. However, unlike the profound sound localization deficit that occurs when A1 and DZ are deactivated together, deactivation of either A1 or DZ alone produced partial and field-specific deficits. For A1, bilateral deactivation resulted in higher error rates (performance dropping to ∼45%) but relatively small errors (mostly within 30° of the target). In contrast, bilateral deactivation of DZ produced somewhat fewer errors (performance dropping to only ∼60% correct), but the errors tended to be larger, often into the incorrect hemifield. Therefore individual deactivation of either A1 or DZ produced specific and unique sound localization deficits. The results of the present study reveal that DZ plays a role in sound localization. Along with previous anatomical and physiological data, these behavioral data support the view that A1 and DZ are distinct cortical areas. Finally, the findings that deactivation of either A1 or DZ alone produces partial sound localization deficits, whereas deactivation of either posterior auditory field (PAF) or anterior ectosylvian sulcus (AES) produces profound sound localization deficits, suggests that PAF and AES make more significant contributions to sound localization than either A1 or DZ.

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