Simulation of free-field sound sources and its application to studies of cortical mechanisms of sound localization in the cat

Brugge, John F.; Reale, Richard A.; Hind, Joseph E.; Chan, Jacob Yuichung; Musicant, Alan D.; Poon, P.W.F.

doi:10.1016/0378-5955(94)90284-4

Cited by 67 publications

(64 citation statements)

References 10 publications

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“…Third, comparing the spatial tuning of inferior colliculus neurons in barn owl using individual and nonindividual HRTF did not show any appreciable differences (Keller et al, 1998). Fourth, the data reported here from A1 is similar to data collected with free-field stimulation or to studies that used a different set of nonindividualized HRTFs (Brugge et al, 1994(Brugge et al, , 1998.…”

Section: Methodological Issuessupporting

confidence: 65%

Functional Gradients of Auditory Sensitivity along the Anterior Ectosylvian Sulcus of the Cat

Las¹,

Shapira²,

Nelken³

2008

J. Neurosci.

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Determining the spatial direction of sound sources is one of the major computations performed by the auditory system. The anterior ectosylvian sulcus (AES) of cat cortex is known to be important for sound localization. However, there are contradicting reports as to the spatial response properties of neurons in AES: whereas some studies found narrowly tuned neurons, others reported mostly spatially widely tuned neurons. We hypothesized that this is the result of a nonhomogenous distribution of the auditory neurons in this area. To test this possibility, we recorded neuronal activity along the AES, together with a sample of neurons from primary auditory cortex (A1) of cats in response to pure tones and to virtual acoustic space stimuli. In all areas, most neurons responded to both types of stimuli. Neurons located in posterior AES (pAES) showed special response properties that distinguished them from neurons in A1 and from neurons in anterior AES (aAES). The proportion of space-selective neurons among auditory neurons was significantly higher in pAES (82%) than in A1 (72%) and in aAES (60%). Furthermore, whereas the large majority of A1 neurons responded preferentially to contralateral sounds, neurons in pAES (and to a lesser extent in aAES) had their spatial selectivity distributed more homogenously. In particular, 28% of the space-selective neurons in pAES had highly modulated frontal receptive fields, against 8% in A1 and 17% in aAES. We conclude that in cats, pAES contains a secondary auditory cortical field which is specialized for spatial processing, in particular for the representation of frontal space.

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Section: Methodological Issuessupporting

confidence: 65%

Functional Gradients of Auditory Sensitivity along the Anterior Ectosylvian Sulcus of the Cat

Las¹,

Shapira²,

Nelken³

2008

J. Neurosci.

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“…Although the methods used here have not been previously used in auditory cortex, a number of previous studies in monkeys and other animals have evaluated the spatial sensitivity of auditory cortical neurons using other means (Middlebrooks and Pettigrew, 1981;Rajan et al, 1990a,b;Brugge et al, 1994Brugge et al, , 1996Brugge et al, , 1998Brugge et al, , 2001Clarey et al, 1994Clarey et al, , 1995Middlebrooks et al, 1994Middlebrooks et al, , 1998Barone et al, 1996;Eggermont and Mossop, 1998;Xu et al, 1998;Brugge and Reale, 2000;Furukawa et al, 2000;Recanzone, 2000;Furukawa and Middlebrooks, 2002;Stecker et al, , 2005aMrsic-Flogel et al, 2005;Woods et al, 2006). These studies have provided numerous clues about auditory cortical spatial sensitivity that are more consistent with a rate code than a place code: neurons tend to exhibit broad spatial tuning (Recanzone, 2000;Mickey and Middlebrooks, 2003;Woods et al, 2006); many neurons show "hemifield" sensitivity (Middlebrooks and Pettigrew, 1981); few neurons have circumscribed receptive fields in frontal space (Rajan et al, .…”

Section: Relationship To Previous Neurophysiological Studiesmentioning

confidence: 99%

A Rate Code for Sound Azimuth in Monkey Auditory Cortex: Implications for Human Neuroimaging Studies

Werner-Reiss

2008

J. Neurosci.

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Is sound location represented in the auditory cortex of humans and monkeys? Human neuroimaging experiments have had only mixed success at demonstrating sound location sensitivity in primary auditory cortex. This is in apparent conflict with studies in monkeys and other animals, in which single-unit recording studies have found stronger evidence for spatial sensitivity. Does this apparent discrepancy reflect a difference between humans and animals, or does it reflect differences in the sensitivity of the methods used for assessing the representation of sound location? The sensitivity of imaging methods such as functional magnetic resonance imaging depends on the following two key aspects of the underlying neuronal population: (1) what kind of spatial sensitivity individual neurons exhibit and (2) whether neurons with similar response preferences are clustered within the brain.To address this question, we conducted a single-unit recording study in monkeys. We investigated the nature of spatial sensitivity in individual auditory cortical neurons to determine whether they have receptive fields (place code) or monotonic (rate code) sensitivity to sound azimuth. Second, we tested how strongly the population of neurons favors contralateral locations. We report here that the majority of neurons show predominantly monotonic azimuthal sensitivity, forming a rate code for sound azimuth, but that at the population level the degree of contralaterality is modest. This suggests that the weakness of the evidence for spatial sensitivity in human neuroimaging studies of auditory cortex may be attributable to limited lateralization at the population level, despite what may be considerable spatial sensitivity in individual neurons.

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“…For instance, 58 to 97% of units in areas A2 and AES responded with more than 50% of their maximum spike rates across receptive fields spanning 180 • or greater [18]; the exact percentage of units varied with cortical area and sound level. A similar breadth of sensitivity is reported for the majority of units in area A1 [13,15,16]. Spatial receptive fields of neurons tend to be smallest when measured with sound levels near threshold, but increases in sound levels can result in considerable expansion of receptive fields [13,25]; Figure 1 shows examples of spatial tuning that broadened with increasing sound level.…”

Section: Neuronal Spatial Tuning and Cortical Topographymentioning

confidence: 49%

“…In the cat, the spatial sensitivity of neurons has been studied in the primary auditory cortex (area A1) [13][14][15][16], area A2 [17][18][19], the anterior ectosylvian area (area AES) [17][18][19][20], and to a limited degree in the anterior auditory area (area AAF) [20]. There are good reasons to assume that cortical areas A1, A2, and AES are involved in sound localization.…”

Section: Neuronal Spatial Tuning and Cortical Topographymentioning

confidence: 99%

Cortical codes for sound localization

Furukawa¹,

Middlebrooks

2001

Acoust. Sci. & Tech.

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Abstract:It is well known that there is a point-to-point map of auditory space in the midbrain: each neuron is tuned to a particular sound-source location, and neurons' preferred locations are topographically represented in a neural structure. In the auditory cortex, however, researchers have consistently failed to demonstrate evidence for such an auditory space map, despite the well-known necessity of the auditory cortex for normal sound localization. Cortical neurons show generally broad spatial tuning, and the preferred locations are not systematically organized on the cortex in a topographical fashion. An alternative hypothesis is presented here: Individual single neurons represent auditory space panoramically by space-specific characteristics of their spike patterns. Information about any particular sound-source location is distributed across a large population of neurons, and we predict accurate localization judgement by combining information across those neurons. In our analyses of experimental data using an artificial neural network algorithm, we were able to recognize spike patterns of single neurons to identify sound-source locations throughout 360 • of space. The amount of information carried by a moderate size of neural ensemble appeared sufficient to account for the accuracy of location judgements by behaving animals.

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Simulation of free-field sound sources and its application to studies of cortical mechanisms of sound localization in the cat

Cited by 67 publications

References 10 publications

Functional Gradients of Auditory Sensitivity along the Anterior Ectosylvian Sulcus of the Cat

Functional Gradients of Auditory Sensitivity along the Anterior Ectosylvian Sulcus of the Cat

A Rate Code for Sound Azimuth in Monkey Auditory Cortex: Implications for Human Neuroimaging Studies

Cortical codes for sound localization

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