1
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van den Wildenberg MF, Bremen P. Heterogeneous spatial tuning in the auditory pathway of the Mongolian Gerbil (Meriones unguiculatus). Eur J Neurosci 2024. [PMID: 39085952 DOI: 10.1111/ejn.16472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 06/17/2024] [Accepted: 07/09/2024] [Indexed: 08/02/2024]
Abstract
Sound-source localization is based on spatial cues arising due to interactions of sound waves with the torso, head and ears. Here, we evaluated neural responses to free-field sound sources in the central nucleus of the inferior colliculus (CIC), the medial geniculate body (MGB) and the primary auditory cortex (A1) of Mongolian gerbils. Using silicon probes we recorded from anaesthetized gerbils positioned in the centre of a sound-attenuating, anechoic chamber. We measured rate-azimuth functions (RAFs) with broad-band noise of varying levels presented from loudspeakers spanning 210° in azimuth and characterized RAFs by calculating spatial centroids, Equivalent Rectangular Receptive Fields (ERRFs), steepest slope locations and spatial-separation thresholds. To compare neuronal responses with behavioural discrimination thresholds from the literature we performed a neurometric analysis based on signal-detection theory. All structures demonstrated heterogeneous spatial tuning with a clear dominance of contralateral tuning. However, the relative amount of contralateral tuning decreased from the CIC to A1. In all three structures spatial tuning broadened with increasing sound-level. This effect was strongest in CIC and weakest in A1. Neurometric spatial-separation thresholds compared well with behavioural discrimination thresholds for locations directly in front of the animal. Our findings contrast with those reported for another rodent, the rat, which exhibits homogenous and sharply delimited contralateral spatial tuning. Spatial tuning in gerbils resembles more closely the tuning reported in A1 of cats, ferrets and non-human primates. Interestingly, gerbils, in contrast to rats, share good low-frequency hearing with carnivores and non-human primates, which may account for the observed spatial tuning properties.
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Affiliation(s)
| | - Peter Bremen
- Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
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2
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Mazo C, Baeta M, Petreanu L. Auditory cortex conveys non-topographic sound localization signals to visual cortex. Nat Commun 2024; 15:3116. [PMID: 38600132 PMCID: PMC11006897 DOI: 10.1038/s41467-024-47546-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 04/02/2024] [Indexed: 04/12/2024] Open
Abstract
Spatiotemporally congruent sensory stimuli are fused into a unified percept. The auditory cortex (AC) sends projections to the primary visual cortex (V1), which could provide signals for binding spatially corresponding audio-visual stimuli. However, whether AC inputs in V1 encode sound location remains unknown. Using two-photon axonal calcium imaging and a speaker array, we measured the auditory spatial information transmitted from AC to layer 1 of V1. AC conveys information about the location of ipsilateral and contralateral sound sources to V1. Sound location could be accurately decoded by sampling AC axons in V1, providing a substrate for making location-specific audiovisual associations. However, AC inputs were not retinotopically arranged in V1, and audio-visual modulations of V1 neurons did not depend on the spatial congruency of the sound and light stimuli. The non-topographic sound localization signals provided by AC might allow the association of specific audiovisual spatial patterns in V1 neurons.
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Affiliation(s)
- Camille Mazo
- Champalimaud Neuroscience Programme, Champalimaud Foundation, Lisbon, Portugal.
| | - Margarida Baeta
- Champalimaud Neuroscience Programme, Champalimaud Foundation, Lisbon, Portugal
| | - Leopoldo Petreanu
- Champalimaud Neuroscience Programme, Champalimaud Foundation, Lisbon, Portugal.
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3
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Grijseels DM, Prendergast BJ, Gorman JC, Miller CT. The neurobiology of vocal communication in marmosets. Ann N Y Acad Sci 2023; 1528:13-28. [PMID: 37615212 PMCID: PMC10592205 DOI: 10.1111/nyas.15057] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
An increasingly popular animal model for studying the neural basis of social behavior, cognition, and communication is the common marmoset (Callithrix jacchus). Interest in this New World primate across neuroscience is now being driven by their proclivity for prosociality across their repertoire, high volubility, and rapid development, as well as their amenability to naturalistic testing paradigms and freely moving neural recording and imaging technologies. The complement of these characteristics set marmosets up to be a powerful model of the primate social brain in the years to come. Here, we focus on vocal communication because it is the area that has both made the most progress and illustrates the prodigious potential of this species. We review the current state of the field with a focus on the various brain areas and networks involved in vocal perception and production, comparing the findings from marmosets to other animals, including humans.
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Affiliation(s)
- Dori M Grijseels
- Cortical Systems and Behavior Laboratory, University of California, San Diego, La Jolla, California, USA
| | - Brendan J Prendergast
- Cortical Systems and Behavior Laboratory, University of California, San Diego, La Jolla, California, USA
| | - Julia C Gorman
- Cortical Systems and Behavior Laboratory, University of California, San Diego, La Jolla, California, USA
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, California, USA
| | - Cory T Miller
- Cortical Systems and Behavior Laboratory, University of California, San Diego, La Jolla, California, USA
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, California, USA
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4
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Chen C, Remington ED, Wang X. Sound localization acuity of the common marmoset (Callithrix jacchus). Hear Res 2023; 430:108722. [PMID: 36863289 DOI: 10.1016/j.heares.2023.108722] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 02/03/2023] [Accepted: 02/10/2023] [Indexed: 02/14/2023]
Abstract
The common marmoset (Callithrix jacchus) is a small arboreal New World primate which has emerged as a promising model in auditory neuroscience. One potentially useful application of this model system is in the study of the neural mechanism underlying spatial hearing in primate species, as the marmosets need to localize sounds to orient their head to events of interest and identify their vocalizing conspecifics that are not visible. However, interpretation of neurophysiological data on sound localization requires an understanding of perceptual abilities, and the sound localization behavior of marmosets has not been well studied. The present experiment measured sound localization acuity using an operant conditioning procedure in which marmosets were trained to discriminate changes in sound location in the horizontal (azimuth) or vertical (elevation) dimension. Our results showed that the minimum audible angle (MAA) for horizontal and vertical discrimination was 13.17° and 12.53°, respectively, for 2 to 32 kHz Gaussian noise. Removing the monaural spectral cues tended to increase the horizontal localization acuity (11.31°). Marmosets have larger horizontal MAA (15.54°) in the rear than the front. Removing the high-frequency (> 26 kHz) region of the head-related transfer function (HRTF) affected vertical acuity mildly (15.76°), but removing the first notch (12-26 kHz) region of HRTF substantially reduced the vertical acuity (89.01°). In summary, our findings indicate that marmosets' spatial acuity is on par with other species of similar head size and field of best vision, and they do not appear to use monaural spectral cues for horizontal discrimination but rely heavily on first notch region of HRTF for vertical discrimination.
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Affiliation(s)
- Chenggang Chen
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Ave., Traylor 410, Baltimore, MD 21025, United States
| | - Evan D Remington
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Ave., Traylor 410, Baltimore, MD 21025, United States
| | - Xiaoqin Wang
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Ave., Traylor 410, Baltimore, MD 21025, United States.
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5
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Gilbert KM, Dureux A, Jafari A, Zanini A, Zeman P, Menon RS, Everling S. A radiofrequency coil to facilitate task-based fMRI of awake marmosets. J Neurosci Methods 2023; 383:109737. [PMID: 36341968 DOI: 10.1016/j.jneumeth.2022.109737] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 10/24/2022] [Accepted: 10/27/2022] [Indexed: 11/08/2022]
Abstract
BACKGROUND The small common marmoset (Callithrix jacchus) is an ideal nonhuman primate for awake fMRI in ultra-high field small animal MRI scanners. However, it can often be challenging in task-based fMRI experiments to provide a robust stimulus within the MRI environment while using hardware (an RF coil and restraint system) that is compatible with awake imaging. NEW METHOD Here we present an RF coil and restraint system that permits unimpeded access to an awake marmoset's head subsequent to immobilization, thereby permitting the setup of peripheral devices and stimuli proximal to the head. RESULTS As an example application, an fMRI experiment probing whole-brain activation in response to marmoset vocalizations was conducted-this paradigm showed significant bilateral activation in the inferior colliculus, medial lateral geniculate nucleus, and auditory cortex. COMPARISON WITH EXISTING METHOD(S) The coil performance was evaluated and compared to a previously published restraint system with integrated RF coil. The image and temporal SNR were improved by up to 58 % and 27 %, respectively, in the peripheral cortex and by 30 % and 3 % in the centre of the brain. The restraint-system topology limited head motion to less than 100 µm of translation and 0.30° of rotation when measured over a 15-minute acquisition. CONCLUSIONS The proposed hardware solution provides a versatile approach to awake-marmoset imaging and, as demonstrated, can facilitate task-based fMRI.
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Affiliation(s)
- Kyle M Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada; Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada.
| | - Audrey Dureux
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada
| | - Azadeh Jafari
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada
| | - Alessandro Zanini
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada
| | - Peter Zeman
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada
| | - Ravi S Menon
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, ON, Canada; Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada
| | - Stefan Everling
- Department of Physiology and Pharmacology, The University of Western Ontario, London, ON, Canada
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6
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Jiang Y, Komatsu M, Chen Y, Xie R, Zhang K, Xia Y, Gui P, Liang Z, Wang L. Constructing the hierarchy of predictive auditory sequences in the marmoset brain. eLife 2022; 11:74653. [PMID: 35174784 PMCID: PMC8893719 DOI: 10.7554/elife.74653] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 02/16/2022] [Indexed: 11/13/2022] Open
Abstract
Our brains constantly generate predictions of sensory input that are compared with actual inputs, propagate the prediction-errors through a hierarchy of brain regions, and subsequently update the internal predictions of the world. However, the essential feature of predictive coding, the notion of hierarchical depth and its neural mechanisms, remains largely unexplored. Here, we investigated the hierarchical depth of predictive auditory processing by combining functional magnetic resonance imaging (fMRI) and high-density whole-brain electrocorticography (ECoG) in marmoset monkeys during an auditory local-global paradigm in which the temporal regularities of the stimuli were designed at two hierarchical levels. The prediction-errors and prediction updates were examined as neural responses to auditory mismatches and omissions. Using fMRI, we identified a hierarchical gradient along the auditory pathway: midbrain and sensory regions represented local, shorter-time-scale predictive processing followed by associative auditory regions, whereas anterior temporal and prefrontal areas represented global, longer-time-scale sequence processing. The complementary ECoG recordings confirmed the activations at cortical surface areas and further differentiated the signals of prediction-error and update, which were transmitted via putative bottom-up γ and top-down β oscillations, respectively. Furthermore, omission responses caused by absence of input, reflecting solely the two levels of prediction signals that are unique to the hierarchical predictive coding framework, demonstrated the hierarchical top-down process of predictions in the auditory, temporal, and prefrontal areas. Thus, our findings support the hierarchical predictive coding framework, and outline how neural networks and spatiotemporal dynamics are used to represent and arrange a hierarchical structure of auditory sequences in the marmoset brain.
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Affiliation(s)
- Yuwei Jiang
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Misako Komatsu
- Laboratory for Molecular Analysis of Higher Brain Function, Center for Brain Science, RIKEN, Saitama, Japan
| | - Yuyan Chen
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Ruoying Xie
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Kaiwei Zhang
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Ying Xia
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Peng Gui
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Zhifeng Liang
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
| | - Liping Wang
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
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7
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Degraded cortical temporal processing in the valproic acid-induced rat model of autism. Neuropharmacology 2022; 209:109000. [PMID: 35182575 DOI: 10.1016/j.neuropharm.2022.109000] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 01/12/2022] [Accepted: 02/13/2022] [Indexed: 11/21/2022]
Abstract
Hearing disorders, such as abnormal speech perception, are frequently reported in individuals with autism. However, the mechanisms underlying these auditory-associated signature deficits in autism remain largely unknown. In this study, we documented significant behavioral impairments in the sound temporal rate discrimination task for rats prenatally exposed to valproic acid (VPA), a well-validated animal model for studying the pathology of autism. In parallel, there was a large-scale degradation in temporal information-processing in their primary auditory cortices (A1) at both levels of spiking outputs and synaptic inputs. Substantially increased spine density of excitatory neurons and decreased numbers of parvalbumin- and somatostatin-labeled inhibitory inter-neurons were also recorded in the A1 after VPA exposure. Given the fact that cortical temporal processing of sound is associated with speech perception in humans, these results in the animal model of VPA exposure provide insight into a possible neurological mechanism underlying auditory and language-related deficits in individuals with autism.
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8
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Liu J, Huang X, Zhang J. Unilateral Conductive Hearing Loss Disrupts the Developmental Refinement of Binaural Processing in the Rat Primary Auditory Cortex. Front Neurosci 2021; 15:762337. [PMID: 34867170 PMCID: PMC8640238 DOI: 10.3389/fnins.2021.762337] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 10/20/2021] [Indexed: 11/23/2022] Open
Abstract
Binaural hearing is critically important for the perception of sound spatial locations. The primary auditory cortex (AI) has been demonstrated to be necessary for sound localization. However, after hearing onset, how the processing of binaural cues by AI neurons develops, and how the binaural processing of AI neurons is affected by reversible unilateral conductive hearing loss (RUCHL), are not fully elucidated. Here, we determined the binaural processing of AI neurons in four groups of rats: postnatal day (P) 14–18 rats, P19–30 rats, P57–70 adult rats, and RUCHL rats (P57–70) with RUCHL during P14–30. We recorded the responses of AI neurons to both monaural and binaural stimuli with variations in interaural level differences (ILDs) and average binaural levels. We found that the monaural response types, the binaural interaction types, and the distributions of the best ILDs of AI neurons in P14–18 rats are already adult-like. However, after hearing onset, there exist developmental refinements in the binaural processing of AI neurons, which are exhibited by the increase in the degree of binaural interaction, and the increase in the sensitivity and selectivity to ILDs. RUCHL during early hearing development affects monaural response types, decreases the degree of binaural interactions, and decreases both the selectivity and sensitivity to ILDs of AI neurons in adulthood. These new evidences help us to understand the refinements and plasticity in the binaural processing of AI neurons during hearing development, and might enhance our understanding in the neuronal mechanism of developmental changes in auditory spatial perception.
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Affiliation(s)
- Jing Liu
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Xinyi Huang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
| | - Jiping Zhang
- Key Laboratory of Brain Functional Genomics, Ministry of Education, NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, School of Life Sciences, East China Normal University, Shanghai, China
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9
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Pandey S, Simhadri S, Zhou Y. Rapid Head Movements in Common Marmoset Monkeys. iScience 2020; 23:100837. [PMID: 32058952 PMCID: PMC6997856 DOI: 10.1016/j.isci.2020.100837] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 11/18/2019] [Accepted: 01/09/2020] [Indexed: 11/27/2022] Open
Abstract
Gaze shifts, the directing of the eyes to an approaching predator, preferred food source, or potential mate, have universal biological significance for the survival of a species. Our knowledge of gaze behavior is based primarily on visually triggered responses, whereas head orientation triggered by auditory stimuli remains poorly characterized. Common marmoset (Callithrix jacchus) is a diurnal, small-bodied (∼350 g), New World monkey species, known for its rich behavioral repertoires during social interactions. We used a lightweight head tracking system to measure marmosets' reflexive head orientations toward a natural stimulus presented from behind. We found that marmoset could rotate its head at angular velocities above 1,000°/s and maintained target accuracy for a wide range of rotation amplitudes (up to 250°). This unusual, saccadic head orienting behavior offers opportunities for understanding the many biological factors that have shaped the evolution of sensorimotor controls of gaze orientation by the primate brain. Marmosets can make rapid, reflexive head turns in response to natural stimuli The peak velocity of marmoset head turns can exceed that of primate eye saccades When the environment is lit, head movements are faster than when it is dark
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Affiliation(s)
- Swarnima Pandey
- College of Health Solutions, Arizona State University, 975 S. Myrtle Avenue, Coor Hall 3470, Tempe, AZ 85287, USA
| | - Sravanthi Simhadri
- College of Health Solutions, Arizona State University, 975 S. Myrtle Avenue, Coor Hall 3470, Tempe, AZ 85287, USA
| | - Yi Zhou
- College of Health Solutions, Arizona State University, 975 S. Myrtle Avenue, Coor Hall 3470, Tempe, AZ 85287, USA.
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10
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Synthesis of Hemispheric ITD Tuning from the Readout of a Neural Map: Commonalities of Proposed Coding Schemes in Birds and Mammals. J Neurosci 2019; 39:9053-9061. [PMID: 31570537 DOI: 10.1523/jneurosci.0873-19.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 09/23/2019] [Accepted: 09/25/2019] [Indexed: 11/21/2022] Open
Abstract
A major cue to infer sound direction is the difference in arrival time of the sound at the left and right ears, called interaural time difference (ITD). The neural coding of ITD and its similarity across species have been strongly debated. In the barn owl, an auditory specialist relying on sound localization to capture prey, ITDs within the physiological range determined by the head width are topographically represented at each frequency. The topographic representation suggests that sound direction may be inferred from the location of maximal neural activity within the map. Such topographical representation of ITD, however, is not evident in mammals. Instead, the preferred ITD of neurons in the mammalian brainstem often lies outside the physiological range and depends on the neuron's best frequency. Because of these disparities, it has been assumed that how spatial hearing is achieved in birds and mammals is fundamentally different. However, recent studies reveal ITD responses in the owl's forebrain and midbrain premotor area that are consistent with coding schemes proposed in mammals. Particularly, sound location in owls could be decoded from the relative firing rates of two broadly and inversely ITD-tuned channels. This evidence suggests that, at downstream stages, the code for ITD may not be qualitatively different across species. Thus, while experimental evidence continues to support the notion of differences in ITD representation across species and brain regions, the latest results indicate notable commonalities, suggesting that codes driving orienting behavior in mammals and birds may be comparable.
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11
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Liu X, Wei F, Cheng Y, Zhang Y, Jia G, Zhou J, Zhu M, Shan Y, Sun X, Yu L, Merzenich MM, Lurie DI, Zheng Q, Zhou X. Auditory Training Reverses Lead (Pb)-Toxicity-Induced Changes in Sound-Azimuth Selectivity of Cortical Neurons. Cereb Cortex 2019; 29:3294-3304. [PMID: 30137254 DOI: 10.1093/cercor/bhy199] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 07/20/2018] [Accepted: 07/26/2018] [Indexed: 01/16/2023] Open
Abstract
Lead (Pb) causes significant adverse effects on the developing brain, resulting in cognitive and learning disabilities in children. The process by which lead produces these negative changes is largely unknown. The fact that children with these syndromes also show deficits in central auditory processing, however, indicates a speculative but disturbing relationship between lead-exposure, impaired auditory processing, and behavioral dysfunction. Here we studied in rats the changes in cortical spatial tuning impacted by early lead-exposure and their potential restoration to normal by auditory training. We found animals that were exposed to lead early in life displayed significant behavioral impairments compared with naïve controls while conducting the sound-azimuth discrimination task. Lead-exposure also degraded the sound-azimuth selectivity of neurons in the primary auditory cortex. Subsequent sound-azimuth discrimination training, however, restored to nearly normal the lead-degraded cortical azimuth selectivity. This reversal of cortical spatial fidelity was paralleled by changes in cortical expression of certain excitatory and inhibitory neurotransmitter receptor subunits. These results in a rodent model demonstrate the persisting neurotoxic effects of early lead-exposure on behavioral and cortical neuronal processing of spatial information of sound. They also indicate that attention-demanding auditory training may remediate lead-induced cortical neurological deficits even after these deficits have occurred.
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Affiliation(s)
- Xia Liu
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China
| | - Fanfan Wei
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China
| | - Yuan Cheng
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China.,New York University-East China Normal University Institute of Brain and Cognitive Science, New York University-Shanghai, Shanghai, China
| | - Yifan Zhang
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China.,New York University-East China Normal University Institute of Brain and Cognitive Science, New York University-Shanghai, Shanghai, China
| | - Guoqiang Jia
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China.,New York University-East China Normal University Institute of Brain and Cognitive Science, New York University-Shanghai, Shanghai, China
| | - Jie Zhou
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China.,New York University-East China Normal University Institute of Brain and Cognitive Science, New York University-Shanghai, Shanghai, China
| | - Min Zhu
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China.,New York University-East China Normal University Institute of Brain and Cognitive Science, New York University-Shanghai, Shanghai, China
| | - Ye Shan
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China
| | - Xinde Sun
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China
| | - Liping Yu
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China
| | | | - Diana I Lurie
- Center for Structural and Functional Neuroscience, Center for Environmental Health Sciences, Department of Biomedical & Pharmaceutical Sciences, College of Health Professions and Biomedical Sciences, University of Montana, Missoula, MT, USA
| | - Qingyin Zheng
- Transformative Otology and Neuroscience Center, Binzhou Medical University, Yantai, China
| | - Xiaoming Zhou
- Key Laboratory of Brain Functional Genomics of Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, Collaborative Innovation Center for Brain Science, School of Life Sciences, East China Normal University, Shanghai, China.,New York University-East China Normal University Institute of Brain and Cognitive Science, New York University-Shanghai, Shanghai, China
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12
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Remington ED, Wang X. Neural Representations of the Full Spatial Field in Auditory Cortex of Awake Marmoset (Callithrix jacchus). Cereb Cortex 2019; 29:1199-1216. [PMID: 29420692 PMCID: PMC6373678 DOI: 10.1093/cercor/bhy025] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 01/13/2018] [Indexed: 11/14/2022] Open
Abstract
Unlike visual signals, sound can reach the ears from any direction, and the ability to localize sounds from all directions is essential for survival in a natural environment. Previous studies have largely focused on the space in front of a subject that is also covered by vision and were often limited to measuring spatial tuning along the horizontal (azimuth) plane. As a result, we know relatively little about how the auditory cortex responds to sounds coming from spatial locations outside the frontal space where visual information is unavailable. By mapping single-neuron responses to the full spatial field in awake marmoset (Callithrix jacchus), an arboreal animal for which spatial processing is vital in its natural habitat, we show that spatial receptive fields in several auditory areas cover all spatial locations. Several complementary measures of spatial tuning showed that neurons were tuned to both frontal space and rear space (outside the coverage of vision), as well as the space above and below the horizontal plane. Together, these findings provide valuable new insights into the representation of all spatial locations by primate auditory cortex.
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Affiliation(s)
- Evan D Remington
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Xiaoqin Wang
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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13
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Panniello M, King AJ, Dahmen JC, Walker KMM. Local and Global Spatial Organization of Interaural Level Difference and Frequency Preferences in Auditory Cortex. Cereb Cortex 2018; 28:350-369. [PMID: 29136122 PMCID: PMC5991210 DOI: 10.1093/cercor/bhx295] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 10/10/2017] [Indexed: 12/16/2022] Open
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.
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Affiliation(s)
- Mariangela Panniello
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Andrew J King
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Johannes C Dahmen
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Kerry M M Walker
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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14
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Toarmino CR, Yen CCC, Papoti D, Bock NA, Leopold DA, Miller CT, Silva AC. Functional magnetic resonance imaging of auditory cortical fields in awake marmosets. Neuroimage 2017; 162:86-92. [PMID: 28830766 DOI: 10.1016/j.neuroimage.2017.08.052] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 08/14/2017] [Accepted: 08/18/2017] [Indexed: 11/25/2022] Open
Abstract
The primate auditory cortex is organized into a network of anatomically and functionally distinct processing fields. Because of its tonotopic properties, the auditory core has been the main target of neurophysiological studies ranging from sensory encoding to perceptual decision-making. By comparison, the auditory belt has been less extensively studied, in part due to the fact that neurons in the belt areas prefer more complex stimuli and integrate over a wider frequency range than neurons in the core, which prefer pure tones of a single frequency. Complementary approaches, such as functional magnetic resonance imaging (fMRI), allow the anatomical identification of both the auditory core and belt and facilitate their functional characterization by rapidly testing a range of stimuli across multiple brain areas simultaneously that can be used to guide subsequent neural recordings. Bridging these technologies in primates will serve to further expand our understanding of primate audition. Here, we developed a novel preparation to test whether different areas of the auditory cortex could be identified using fMRI in common marmosets (Callithrix jacchus), a powerful model of the primate auditory system. We used two types of stimulation, band pass noise and pure tones, to parse apart the auditory core from surrounding secondary belt fields. In contrast to most auditory fMRI experiments in primates, we employed a continuous sampling paradigm to rapidly collect data with little deleterious effects. Here we found robust bilateral auditory cortex activation in two marmosets and unilateral activation in a third utilizing this preparation. Furthermore, we confirmed results previously reported in electrophysiology experiments, such as the tonotopic organization of the auditory core and regions activating preferentially to complex over simple stimuli. Overall, these data establish a key preparation for future research to investigate various functional properties of marmoset auditory cortex.
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Affiliation(s)
- Camille R Toarmino
- Cortical Systems and Behavior Laboratory, Department of Psychology and Neurosciences Graduate Program, The University of California at San Diego, La Jolla, CA, 92093-0109, USA
| | - Cecil C C Yen
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, Bethesda, MD, 20892-4478, USA
| | - Daniel Papoti
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, Bethesda, MD, 20892-4478, USA
| | - Nicholas A Bock
- Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, Ontario, L8S 4K1, Canada
| | - David A Leopold
- Section on Cognitive Neurophysiology and Imaging, Laboratory of Neuropsychology, National Institute of Mental Health, Bethesda, MD, 20892-4400, USA
| | - Cory T Miller
- Cortical Systems and Behavior Laboratory, Department of Psychology and Neurosciences Graduate Program, The University of California at San Diego, La Jolla, CA, 92093-0109, USA
| | - Afonso C Silva
- Cerebral Microcirculation Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, Bethesda, MD, 20892-4478, USA.
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15
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Representation of Multidimensional Stimuli: Quantifying the Most Informative Stimulus Dimension from Neural Responses. J Neurosci 2017; 37:7332-7346. [PMID: 28663198 DOI: 10.1523/jneurosci.0318-17.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 06/09/2017] [Accepted: 06/17/2017] [Indexed: 11/21/2022] Open
Abstract
A common way to assess the function of sensory neurons is to measure the number of spikes produced by individual neurons while systematically varying a given dimension of the stimulus. Such measured tuning curves can then be used to quantify the accuracy of the neural representation of the stimulus dimension under study, which can in turn be related to behavioral performance. However, tuning curves often change shape when other dimensions of the stimulus are varied, reflecting the simultaneous sensitivity of neurons to multiple stimulus features. Here we illustrate how one-dimensional information analyses are misleading in this context, and propose a framework derived from Fisher information that allows the quantification of information carried by neurons in multidimensional stimulus spaces. We use this method to probe the representation of sound localization in auditory neurons of chinchillas and guinea pigs of both sexes, and show how heterogeneous tuning properties contribute to a representation of sound source position that is robust to changes in sound level.SIGNIFICANCE STATEMENT Sensory neurons' responses are typically modulated simultaneously by numerous stimulus properties, which can result in an overestimation of neural acuity with existing one-dimensional neural information transmission measures. To overcome this limitation, we develop new, compact expressions of Fisher information-derived measures that bound the robust encoding of separate stimulus dimensions in the context of multidimensional stimuli. We apply this method to the problem of the representation of sound source location in the face of changes in sound source level by neurons of the auditory midbrain.
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16
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Montagne C, Zhou Y. Visual capture of a stereo sound: Interactions between cue reliability, sound localization variability, and cross-modal bias. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2016; 140:471. [PMID: 27475171 DOI: 10.1121/1.4955314] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Multisensory interactions involve coordination and sometimes competition between multiple senses. Vision usually dominates audition in spatial judgments when light and sound stimuli are presented from two different physical locations. This study investigated the influence of vision on the perceived location of a phantom sound source placed in a stereo sound field using a pair of loudspeakers emitting identical signals that were delayed or attenuated relative to each other. Results show that although a similar horizontal range (+/-45°) was reported for timing-modulated and level-modulated signals, listeners' localization performance showed greater variability for the timing signals. When visual stimuli were presented simultaneously with the auditory stimuli, listeners showed stronger visual bias for timing-modulated signals than level-modulated and single-speaker control signals. Trial-to-trial errors remained relatively stable over time, suggesting that sound localization uncertainty has an immediate and long-lasting effect on the across-modal bias. Binaural signal analyses further reveal that interaural differences of time and intensity-the two primary cues for sound localization in the azimuthal plane-are inherently more ambiguous for signals placed using timing. These results suggest that binaural ambiguity is intrinsically linked with localization variability and the strength of cross-modal bias in sound localization.
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Affiliation(s)
- Christopher Montagne
- Laboratory of Auditory Computation & Neurophysiology, Department of Speech and Hearing Science, College of Health Solutions, Arizona State University, Tempe, Arizona 85287, USA
| | - Yi Zhou
- Laboratory of Auditory Computation & Neurophysiology, Department of Speech and Hearing Science, College of Health Solutions, Arizona State University, Tempe, Arizona 85287, USA
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17
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Razak KA. Functional segregation of monaural and binaural selectivity in the pallid bat auditory cortex. Hear Res 2016; 337:35-45. [PMID: 27233917 DOI: 10.1016/j.heares.2016.05.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 05/05/2016] [Accepted: 05/13/2016] [Indexed: 11/30/2022]
Abstract
Different fields of the auditory cortex can be distinguished by the extent and level tolerance of spatial selectivity. The mechanisms underlying the range of spatial tuning properties observed across cortical fields are unclear. Here, this issue was addressed in the pallid bat because its auditory cortex contains two segregated regions of response selectivity that serve two different behaviors: echolocation for obstacle avoidance and localization of prey-generated noise. This provides the unique opportunity to examine mechanisms of spatial properties in two functionally distinct regions. Previous studies have shown that spatial selectivity of neurons in the region selective for noise (noise-selective region, NSR) is level tolerant and shaped by interaural level difference (ILD) selectivity. In contrast, spatial selectivity of neurons in the echolocation region ('FM sweep-selective region' or FMSR) is strongly level dependent with many neurons responding to multiple distinct spatial locations for louder sounds. To determine the mechanisms underlying such level dependence, frequency, azimuth, rate-level responses and ILD selectivity were measured from the same FMSR neurons. The majority (∼75%) of FMSR neurons were monaural (ILD insensitive). Azimuth tuning curves expanded or split into multiple peaks with increasing sound level in a manner that was predicted by the rate-level response of neurons. These data suggest that azimuth selectivity of FMSR neurons depends more on monaural ear directionality and rate-level responses. The pallid bat cortex utilizes segregated monaural and binaural regions to process echoes and prey-generated noise. Together the pallid bat FMSR/NSR data provide mechanistic explanations for a broad range of spatial tuning properties seen across species.
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Affiliation(s)
- Khaleel A Razak
- Department of Psychology and the Graduate Neuroscience Program, University of California, 900 University Avenue, Riverside, CA 92521, USA.
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18
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Physiological Evidence for a Midline Spatial Channel in Human Auditory Cortex. J Assoc Res Otolaryngol 2016; 17:331-40. [PMID: 27164943 PMCID: PMC4940291 DOI: 10.1007/s10162-016-0571-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 04/26/2016] [Indexed: 12/23/2022] Open
Abstract
Studies with humans and other mammals have provided support for a two-channel representation of horizontal (“azimuthal”) space in the auditory system. In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location. One channel is maximally responsive to sounds towards the left and the other to sounds towards the right. However, recent psychophysical studies of humans, and physiological studies of other mammals, point to the presence of an additional channel, maximally responsive to the midline. In this study, we used electroencephalography to seek physiological evidence for such a midline channel in humans. We measured neural responses to probe stimuli presented from straight ahead (0 °) or towards the right (+30 ° or +90 °). Probes were preceded by adapter stimuli to temporarily suppress channel activity. Adapters came from 0 ° or alternated between left and right (−30 ° and +30 ° or −90 ° and +90 °). For the +90 ° probe, to which the right-tuned channel would respond most strongly, both accounts predict greatest adaptation when the adapters are at ±90 °. For the 0 ° probe, the two-channel account predicts greatest adaptation from the ±90 ° adapters, while the three-channel account predicts greatest adaptation when the adapters are at 0 ° because these adapters stimulate the midline-tuned channel which responds most strongly to the 0 ° probe. The results were consistent with the three-channel account. In addition, a computational implementation of the three-channel account fitted the probe response sizes well, explaining 93 % of the variance about the mean, whereas a two-channel implementation produced a poor fit and explained only 61 % of the variance.
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19
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Asymmetries in the representation of space in the human auditory cortex depend on the global stimulus context. Neuroreport 2016; 27:242-6. [DOI: 10.1097/wnr.0000000000000527] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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20
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Cortical Transformation of Spatial Processing for Solving the Cocktail Party Problem: A Computational Model(1,2,3). eNeuro 2016; 3:eN-NWR-0086-15. [PMID: 26866056 PMCID: PMC4745179 DOI: 10.1523/eneuro.0086-15.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 12/16/2015] [Accepted: 12/18/2015] [Indexed: 12/04/2022] Open
Abstract
In multisource, “cocktail party” sound environments, human and animal auditory systems can use spatial cues to effectively separate and follow one source of sound over competing sources. In multisource, “cocktail party” sound environments, human and animal auditory systems can use spatial cues to effectively separate and follow one source of sound over competing sources. While mechanisms to extract spatial cues such as interaural time differences (ITDs) are well understood in precortical areas, how such information is reused and transformed in higher cortical regions to represent segregated sound sources is not clear. We present a computational model describing a hypothesized neural network that spans spatial cue detection areas and the cortex. This network is based on recent physiological findings that cortical neurons selectively encode target stimuli in the presence of competing maskers based on source locations (Maddox et al., 2012). We demonstrate that key features of cortical responses can be generated by the model network, which exploits spatial interactions between inputs via lateral inhibition, enabling the spatial separation of target and interfering sources while allowing monitoring of a broader acoustic space when there is no competition. We present the model network along with testable experimental paradigms as a starting point for understanding the transformation and organization of spatial information from midbrain to cortex. This network is then extended to suggest engineering solutions that may be useful for hearing-assistive devices in solving the cocktail party problem.
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21
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Sensory Cortical Plasticity Participates in the Epigenetic Regulation of Robust Memory Formation. Neural Plast 2016; 2016:7254297. [PMID: 26881129 PMCID: PMC4735916 DOI: 10.1155/2016/7254297] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/20/2015] [Indexed: 12/23/2022] Open
Abstract
Neuroplasticity remodels sensory cortex across the lifespan. A function of adult sensory cortical plasticity may be capturing available information during perception for memory formation. The degree of experience-dependent remodeling in sensory cortex appears to determine memory strength and specificity for important sensory signals. A key open question is how plasticity is engaged to induce different degrees of sensory cortical remodeling. Neural plasticity for long-term memory requires the expression of genes underlying stable changes in neuronal function, structure, connectivity, and, ultimately, behavior. Lasting changes in transcriptional activity may depend on epigenetic mechanisms; some of the best studied in behavioral neuroscience are DNA methylation and histone acetylation and deacetylation, which, respectively, promote and repress gene expression. One purpose of this review is to propose epigenetic regulation of sensory cortical remodeling as a mechanism enabling the transformation of significant information from experiences into content-rich memories of those experiences. Recent evidence suggests how epigenetic mechanisms regulate highly specific reorganization of sensory cortical representations that establish a widespread network for memory. Thus, epigenetic mechanisms could initiate events to establish exceptionally persistent and robust memories at a systems-wide level by engaging sensory cortical plasticity for gating what and how much information becomes encoded.
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22
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Day ML, Delgutte B. Neural population encoding and decoding of sound source location across sound level in the rabbit inferior colliculus. J Neurophysiol 2015; 115:193-207. [PMID: 26490292 DOI: 10.1152/jn.00643.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/17/2015] [Indexed: 11/22/2022] Open
Abstract
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.
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Affiliation(s)
- Mitchell L Day
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts; and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
| | - Bertrand Delgutte
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear, Boston, Massachusetts; and Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts
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23
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Lui LL, Mokri Y, Reser DH, Rosa MGP, Rajan R. Responses of neurons in the marmoset primary auditory cortex to interaural level differences: comparison of pure tones and vocalizations. Front Neurosci 2015; 9:132. [PMID: 25941469 PMCID: PMC4403308 DOI: 10.3389/fnins.2015.00132] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 04/01/2015] [Indexed: 11/13/2022] Open
Abstract
Interaural level differences (ILDs) are the dominant cue for localizing the sources of high frequency sounds that differ in azimuth. Neurons in the primary auditory cortex (A1) respond differentially to ILDs of simple stimuli such as tones and noise bands, but the extent to which this applies to complex natural sounds, such as vocalizations, is not known. In sufentanil/N2O anesthetized marmosets, we compared the responses of 76 A1 neurons to three vocalizations (Ock, Tsik, and Twitter) and pure tones at cells' characteristic frequency. Each stimulus was presented with ILDs ranging from 20 dB favoring the contralateral ear to 20 dB favoring the ipsilateral ear to cover most of the frontal azimuthal space. The response to each stimulus was tested at three average binaural levels (ABLs). Most neurons were sensitive to ILDs of vocalizations and pure tones. For all stimuli, the majority of cells had monotonic ILD sensitivity functions favoring the contralateral ear, but we also observed ILD sensitivity functions that peaked near the midline and functions favoring the ipsilateral ear. Representation of ILD in A1 was better for pure tones and the Ock vocalization in comparison to the Tsik and Twitter calls; this was reflected by higher discrimination indices and greater modulation ranges. ILD sensitivity was heavily dependent on ABL: changes in ABL by ±20 dB SPL from the optimal level for ILD sensitivity led to significant decreases in ILD sensitivity for all stimuli, although ILD sensitivity to pure tones and Ock calls was most robust to such ABL changes. Our results demonstrate differences in ILD coding for pure tones and vocalizations, showing that ILD sensitivity in A1 to complex sounds cannot be simply extrapolated from that to pure tones. They also show A1 neurons do not show level-invariant representation of ILD, suggesting that such a representation of auditory space is likely to require population coding, and further processing at subsequent hierarchical stages.
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Affiliation(s)
- Leo L Lui
- Department of Physiology, Monash University Clayton, VIC, Australia ; Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Clayton, VIC, Australia
| | - Yasamin Mokri
- Department of Physiology, Monash University Clayton, VIC, Australia
| | - David H Reser
- Department of Physiology, Monash University Clayton, VIC, Australia
| | - Marcello G P Rosa
- Department of Physiology, Monash University Clayton, VIC, Australia ; Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Clayton, VIC, Australia
| | - Ramesh Rajan
- Department of Physiology, Monash University Clayton, VIC, Australia ; Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Clayton, VIC, Australia ; Ear Sciences Institute of Australia Subiaco, WA, Australia
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24
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Zhang X, Zhang Q, Hu X, Zhang B. Neural representation of three-dimensional acoustic space in the human temporal lobe. Front Hum Neurosci 2015; 9:203. [PMID: 25932011 PMCID: PMC4399328 DOI: 10.3389/fnhum.2015.00203] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/27/2015] [Indexed: 11/13/2022] Open
Abstract
Sound localization is an important function of the human brain, but the underlying cortical mechanisms remain unclear. In this study, we recorded auditory stimuli in three-dimensional space and then replayed the stimuli through earphones during functional magnetic resonance imaging (fMRI). By employing a machine learning algorithm, we successfully decoded sound location from the blood oxygenation level-dependent signals in the temporal lobe. Analysis of the data revealed that different cortical patterns were evoked by sounds from different locations. Specifically, discrimination of sound location along the abscissa axis evoked robust responses in the left posterior superior temporal gyrus (STG) and right mid-STG, discrimination along the elevation (EL) axis evoked robust responses in the left posterior middle temporal lobe (MTL) and right STG, and discrimination along the ordinate axis evoked robust responses in the left mid-MTL and right mid-STG. These results support a distributed representation of acoustic space in human cortex.
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Affiliation(s)
- Xiaolu Zhang
- State Key Laboratory of Intelligent Technology and Systems, Tsinghua National Laboratory for Information Science and Technology (TNList), Department of Computer Science and Technology, Tsinghua University Beijing, China
| | - Qingtian Zhang
- State Key Laboratory of Intelligent Technology and Systems, Tsinghua National Laboratory for Information Science and Technology (TNList), Department of Computer Science and Technology, Tsinghua University Beijing, China
| | - Xiaolin Hu
- State Key Laboratory of Intelligent Technology and Systems, Tsinghua National Laboratory for Information Science and Technology (TNList), Department of Computer Science and Technology, Tsinghua University Beijing, China ; Center for Brain-Inspired Computing Research (CBICR), Tsinghua University Beijing, China
| | - Bo Zhang
- State Key Laboratory of Intelligent Technology and Systems, Tsinghua National Laboratory for Information Science and Technology (TNList), Department of Computer Science and Technology, Tsinghua University Beijing, China ; Center for Brain-Inspired Computing Research (CBICR), Tsinghua University Beijing, China
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25
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Abstract
The auditory system derives locations of sound sources from spatial cues provided by the interaction of sound with the head and external ears. Those cues are analyzed in specific brainstem pathways and then integrated as cortical representation of locations. The principal cues for horizontal localization are interaural time differences (ITDs) and interaural differences in sound level (ILDs). Vertical and front/back localization rely on spectral-shape cues derived from direction-dependent filtering properties of the external ears. The likely first sites of analysis of these cues are the medial superior olive (MSO) for ITDs, lateral superior olive (LSO) for ILDs, and dorsal cochlear nucleus (DCN) for spectral-shape cues. Localization in distance is much less accurate than that in horizontal and vertical dimensions, and interpretation of the basic cues is influenced by additional factors, including acoustics of the surroundings and familiarity of source spectra and levels. Listeners are quite sensitive to sound motion, but it remains unclear whether that reflects specific motion detection mechanisms or simply detection of changes in static location. Intact auditory cortex is essential for normal sound localization. Cortical representation of sound locations is highly distributed, with no evidence for point-to-point topography. Spatial representation is strictly contralateral in laboratory animals that have been studied, whereas humans show a prominent right-hemisphere dominance.
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Affiliation(s)
- John C Middlebrooks
- Departments of Otolaryngology, Neurobiology and Behavior, Cognitive Sciences, and Biomedical Engineering, University of California at Irvine, Irvine, CA, USA.
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26
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Phillips DP, Mew EJ, Hall SE. Selective adaptation in sound lateralization is not due to a repulsion effect. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2014; 136:EL424. [PMID: 25480093 DOI: 10.1121/1.4902419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Selective adaptation studies in dichotic sound lateralization have contributed to a three-channel model of lateralization mechanisms. They usually have employed highly-lateralized adaptor stimuli, and the expression of the selective adaptation is the perceptual shift of test tone locations away from that of the adaptor. The present study employed modestly lateralized adaptors so that any repulsion mechanism could be visualized in distorted position judgments for test tones on both sides of the adaptor stimuli. Comparison of position reports for tones lateralized using interaural time differences before and after selective adaptation provided no evidence for a repulsion effect.
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Affiliation(s)
- Dennis P Phillips
- Department of Psychology and Neuroscience and Department of Surgery, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Emma J Mew
- Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada ,
| | - Susan E Hall
- Department of Psychology and Neuroscience, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada ,
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27
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Gai Y, Ruhland JL, Yin TCT. Localization of click trains and speech by cats: the negative level effect. J Assoc Res Otolaryngol 2014; 15:789-800. [PMID: 24942705 DOI: 10.1007/s10162-014-0469-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 05/28/2014] [Indexed: 11/30/2022] Open
Abstract
Although localization of sound in elevation is believed to depend on spectral cues, it has been shown with human listeners that the temporal features of sound can also greatly affect localization performance. Of particular interest is a phenomenon known as the negative level effect, which describes the deterioration of localization ability in elevation with increasing sound level and is observed only with impulsive or short-duration sound. The present study uses the gaze positions of domestic cats as measures of perceived locations of sound targets varying in azimuth and elevation. The effects of sound level on localization in terms of accuracy, precision, and response latency were tested for sound with different temporal features, such as a click train, a single click, a continuous sound that had the same frequency spectrum of the click train, and speech segments. In agreement with previous human studies, negative level effects were only observed with click-like stimuli and only in elevation. In fact, localization of speech sounds in elevation benefited significantly when the sound level increased. Our findings indicate that the temporal continuity of a sound can affect the frequency analysis performed by the auditory system, and the variation in the frequency spectrum contained in speech sound does not interfere much with the spectral coding for its location in elevation.
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Affiliation(s)
- Yan Gai
- Department of Neuroscience, University of Wisconsin-Madison, Medical Sciences Building, 251 SMI, 1300 University Avenue, Madison, WI, 53706, USA,
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28
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Wang Y, Gutfreund Y, Peña JL. Coding space-time stimulus dynamics in auditory brain maps. Front Physiol 2014; 5:135. [PMID: 24782781 PMCID: PMC3986518 DOI: 10.3389/fphys.2014.00135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/19/2014] [Indexed: 11/21/2022] Open
Abstract
Sensory maps are often distorted representations of the environment, where ethologically-important ranges are magnified. The implication of a biased representation extends beyond increased acuity for having more neurons dedicated to a certain range. Because neurons are functionally interconnected, non-uniform representations influence the processing of high-order features that rely on comparison across areas of the map. Among these features are time-dependent changes of the auditory scene generated by moving objects. How sensory representation affects high order processing can be approached in the map of auditory space of the owl's midbrain, where locations in the front are over-represented. In this map, neurons are selective not only to location but also to location over time. The tuning to space over time leads to direction selectivity, which is also topographically organized. Across the population, neurons tuned to peripheral space are more selective to sounds moving into the front. The distribution of direction selectivity can be explained by spatial and temporal integration on the non-uniform map of space. Thus, the representation of space can induce biased computation of a second-order stimulus feature. This phenomenon is likely observed in other sensory maps and may be relevant for behavior.
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Affiliation(s)
- Yunyan Wang
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine Bronx, NY, USA
| | - Yoram Gutfreund
- The Rappaport Research Institute and Faculty of Medicine The Technion, Haifa, Israel
| | - José L Peña
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine Bronx, NY, USA
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Kusmierek P, Rauschecker JP. Selectivity for space and time in early areas of the auditory dorsal stream in the rhesus monkey. J Neurophysiol 2014; 111:1671-85. [PMID: 24501260 DOI: 10.1152/jn.00436.2013] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The respective roles of ventral and dorsal cortical processing streams are still under discussion in both vision and audition. We characterized neural responses in the caudal auditory belt cortex, an early dorsal stream region of the macaque. We found fast neural responses with elevated temporal precision as well as neurons selective to sound location. These populations were partly segregated: Neurons in a caudomedial area more precisely followed temporal stimulus structure but were less selective to spatial location. Response latencies in this area were even shorter than in primary auditory cortex. Neurons in a caudolateral area showed higher selectivity for sound source azimuth and elevation, but responses were slower and matching to temporal sound structure was poorer. In contrast to the primary area and other regions studied previously, latencies in the caudal belt neurons were not negatively correlated with best frequency. Our results suggest that two functional substreams may exist within the auditory dorsal stream.
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Affiliation(s)
- Pawel Kusmierek
- Department of Neuroscience, Georgetown University Medical Center, Washington, District of Columbia
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30
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Zhou Y, Wang X. Spatially extended forward suppression in primate auditory cortex. Eur J Neurosci 2013; 39:919-933. [PMID: 24372934 DOI: 10.1111/ejn.12460] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 10/22/2013] [Accepted: 11/20/2013] [Indexed: 11/26/2022]
Abstract
When auditory neurons are stimulated with a pair of sounds, the preceding sound can inhibit the neural responses to the succeeding sound. This phenomenon, referred to as 'forward suppression', has been linked to perceptual forward masking. Previous studies investigating forward suppression typically measured the interaction between masker and probe sounds using a fixed sound location. However, in natural environments, interacting sounds often come from different spatial locations. The present study investigated two questions regarding forward suppression in the primary auditory cortex and adjacent caudal field of awake marmoset monkeys. First, what is the relationship between the location of a masker and its effectiveness in inhibiting neural response to a probe? Second, does varying the location of a masker change the spectral profile of forward suppression? We found that a masker can inhibit a neuron's response to a probe located at a preferred location even when the masker is located at a non-preferred location of a neuron. This is especially so for neurons in the caudal field. Furthermore, we found that the strongest forward suppression is observed when a masker's frequency is close to the best frequency of a neuron, regardless of the location of the masker. These results reveal, for the first time, the stability of forward masking in cortical processing of multiple sounds presented from different locations. They suggest that forward suppression in the auditory cortex is spectrally specific and spatially broad with respect to the frequency and location of the masker, respectively.
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Affiliation(s)
- Yi Zhou
- Laboratory of Auditory Neurophysiology, Department of Biomedical Engineering, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA
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31
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Kyweriga M, Stewart W, Wehr M. Neuronal interaural level difference response shifts are level-dependent in the rat auditory cortex. J Neurophysiol 2013; 111:930-8. [PMID: 24335208 DOI: 10.1152/jn.00648.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
How does the brain accomplish sound localization with invariance to total sound level? Sensitivity to interaural level differences (ILDs) is first computed at the lateral superior olive (LSO) and is observed at multiple levels of the auditory pathway, including the central nucleus of inferior colliculus (ICC) and auditory cortex. In LSO, this ILD sensitivity is level-dependent, such that ILD response functions shift toward the ipsilateral (excitatory) ear with increasing sound level. Thus early in the processing pathway changes in firing rate could indicate changes in sound location, sound level, or both. In ICC, while ILD responses can shift toward either ear in individual neurons, there is no net ILD response shift at the population level. In behavioral studies of human sound localization acuity, ILD sensitivity is invariant to increasing sound levels. Level-invariant sound localization would suggest transformation in level sensitivity between LSO and perception of sound sources. Whether this transformation is completed at the level of the ICC or continued at higher levels remains unclear. It also remains unknown whether perceptual sound localization is level-invariant in rats, as it is in humans. We asked whether ILD sensitivity is level-invariant in rat auditory cortex. We performed single-unit and whole cell recordings in rat auditory cortex under ketamine anesthesia and measured responses to white noise bursts presented through sealed earphones at a range of ILDs. Surprisingly, we found that with increasing sound levels ILD responses shifted toward the ipsilateral ear (which is typically inhibitory), regardless of whether cells preferred ipsilateral, contralateral, or binaural stimuli. Voltage-clamp recordings suggest that synaptic inhibition does not contribute substantially to this transformation in level sensitivity. We conclude that the level invariance of ILD sensitivity seen in behavioral studies is not present in rat auditory cortex.
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32
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Briley PM, Summerfield AQ. Age-related deterioration of the representation of space in human auditory cortex. Neurobiol Aging 2013; 35:633-44. [PMID: 24094582 DOI: 10.1016/j.neurobiolaging.2013.08.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 08/23/2013] [Accepted: 08/28/2013] [Indexed: 10/26/2022]
Abstract
One of the principal auditory disabilities associated with older age is difficulty in locating and tracking sources of sound. This study investigated whether these difficulties are associated with deterioration in the representation of space in the auditory cortex. In psychophysical tests, half of a group of older (>60 years) adults displayed spatial acuity similar to that of young adults throughout the frontal horizontal plane. The remaining half had considerably poorer spatial acuity at the more peripheral regions of frontal space. Computational modeling of electroencephalographic responses to abrupt location shifts demonstrated marked differences in the spatial tuning of populations of cortical neurons between the older adults with poor spatial acuity on the one hand, and those with good spatial acuity, as well as young adults, on the other hand. In those with poor spatial acuity, cortical responses contained little information with which to distinguish peripheral locations. We demonstrate a clear link between neural responses and spatial acuity measured behaviorally, and provide evidence for age-related changes in the coding of horizontal space.
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Affiliation(s)
- Paul M Briley
- Department of Psychology, University of York, York, UK.
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Yao JD, Bremen P, Middlebrooks JC. Rat primary auditory cortex is tuned exclusively to the contralateral hemifield. J Neurophysiol 2013; 110:2140-51. [PMID: 23945782 DOI: 10.1152/jn.00219.2013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The rat is a widely used species for study of the auditory system. Psychophysical results from rats have shown an inability to discriminate sound source locations within a lateral hemifield, despite showing fairly sharp near-midline acuity. We tested the hypothesis that those characteristics of the rat's sound localization psychophysics are evident in the characteristics of spatial sensitivity of its cortical neurons. In addition, we sought quantitative descriptions of in vivo spatial sensitivity of cortical neurons that would support development of an in vitro experimental model to study cortical mechanisms of spatial hearing. We assessed the spatial sensitivity of single- and multiple-neuron responses in the primary auditory cortex (A1) of urethane-anesthetized rats. Free-field noise bursts were varied throughout 360° of azimuth in the horizontal plane at sound levels from 10 to 40 dB above neural thresholds. All neurons encountered in A1 displayed contralateral-hemifield spatial tuning in that they responded strongly to contralateral sound source locations, their responses cut off sharply for locations near the frontal midline, and they showed weak or no responses to ipsilateral sources. Spatial tuning was quite stable across a 30-dB range of sound levels. Consistent with rat psychophysical results, a linear discriminator analysis of spike counts exhibited high spatial acuity for near-midline sounds and poor discrimination for off-midline locations. Hemifield spatial tuning is the most common pattern across all mammals tested previously. The homogeneous population of neurons in rat area A1 will make an excellent system for study of the mechanisms underlying that pattern.
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Affiliation(s)
- Justin D Yao
- Department of Neurobiology and Behavior, University of California at Irvine, Irvine, California
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Polley DB, Thompson JH, Guo W. Brief hearing loss disrupts binaural integration during two early critical periods of auditory cortex development. Nat Commun 2013; 4:2547. [PMID: 24077484 PMCID: PMC4131765 DOI: 10.1038/ncomms3547] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 09/03/2013] [Indexed: 01/15/2023] Open
Abstract
Early binaural experience can recalibrate central auditory circuits that support spatial hearing. However, it is not known how binaural integration matures shortly after hearing onset or whether various developmental stages are differentially impacted by disruptions of normal binaural experience. Here we induce a brief, reversible unilateral conductive hearing loss (CHL) at several experimentally determined milestones in mouse primary auditory cortex (A1) development and characterize its effects ~1 week after normal hearing is restored. We find that CHL shapes A1 binaural selectivity during two early critical periods. CHL before P16 disrupts the normal coregistration of interaural frequency tuning, whereas CHL on P16, but not before or after, disrupts interaural level difference sensitivity contained in long-latency spikes. These data highlight an evolving plasticity in the developing auditory cortex that may relate to the aetiology of amblyaudia, a binaural hearing impairment associated with bouts of otitis media during human infancy.
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Affiliation(s)
- Daniel B. Polley
- Dept. of Otology and Laryngology, Harvard Medical School, Boston MA 02114 USA
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston MA 02114 MA
- Center for Computational Neuroscience and Neural Technology, Boston University, Boston MA 02215
| | - John H. Thompson
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston MA 02114 MA
| | - Wei Guo
- Eaton-Peabody Laboratories, Massachusetts Eye and Ear Infirmary, Boston MA 02114 MA
- Center for Computational Neuroscience and Neural Technology, Boston University, Boston MA 02215
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35
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Lee CC, Middlebrooks JC. Specialization for sound localization in fields A1, DZ, and PAF of cat auditory cortex. J Assoc Res Otolaryngol 2012. [PMID: 23180228 DOI: 10.1007/s10162-012-0357-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cortical deactivation studies in cats have implicated the primary auditory cortex (A1), the dorsal zone (DZ), and the posterior auditory field (PAF) in sound localization behavior, and physiological studies in anesthetized conditions have demonstrated clear differences in spatial sensitivity among those areas. We trained cats to perform two listening tasks and then we recorded from cortical neurons in off-task and in both on-task conditions during single recording sessions. The results confirmed some of the results from anesthetized conditions and revealed unexpected differences. Neurons in each field showed a variety of firing patterns, including onset-only, complex onset and long latency, and suppression or offset. A substantial minority of units showed sharpening of spatial sensitivity, particularly that of onset responses, during task performance: 44 %, 35 %, and 31 % of units in areas A1, DZ, and PAF, respectively, showed significant spatial sharpening. Field DZ was distinguished by a larger percentage of neurons responding best to near-midline locations, whereas the spatial preferences of PAF neurons were distributed more uniformly throughout the contralateral hemifield. Those directional biases also were evident in measures of the accuracy with which neural spike patterns could signal sound locations. Field DZ provided the greatest accuracy for midline locations. The location dependence of accuracy in PAF was orthogonal to that of DZ, with the greatest accuracy for lateral locations. The results suggest a view of spatial representation in the auditory cortex in which DZ exhibits an overrepresentation of the frontal areas around the midline, whereas PAF provides a more uniform representation of contralateral space, including areas behind the head. Spatial preferences of area A1 neurons were intermediate between those of DZ and PAF, sharpening as needed for localization tasks.
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Affiliation(s)
- Chen-Chung Lee
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, MI 48109, USA.
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