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Manno FAM, An Z, Kumar R, Wu EX, He J, Feng Y, Lau C. Structural Alterations in a Rat Model of Short-Term Conductive Hearing Loss Are Associated With Reduced Resting State Functional Connectivity. Front Syst Neurosci 2021; 15:655172. [PMID: 34456689 PMCID: PMC8397539 DOI: 10.3389/fnsys.2021.655172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 07/02/2021] [Indexed: 12/14/2022] Open
Abstract
Conductive hearing loss (CHL) results in attenuation of air conducted sound reaching the inner ear. How a change in air conducted sound alters the auditory system resulting in cortical alterations is not well understood. Here, we have assessed structural and functional magnetic resonance imaging (MRI) in an adult (P60) rat model of short-term conductive hearing loss (1 week). Diffusion tensor imaging (DTI) revealed fractional anisotropy (FA) and axial diffusivity alterations after hearing loss that circumscribed the auditory cortex (AC). Tractography found the lateral lemniscus tract leading to the bilateral inferior colliculus (IC) was reduced. For baseline comparison, DTI and tractography alterations were not found for the somatosensory cortex. To determine functional connectivity changes due to hearing loss, seed-based analysis (SBA) and independent component analysis (ICA) were performed. Short term conductive hearing loss altered functional connectivity in the AC and IC, but not the somatosensory cortex. The results present an exploratory neuroimaging assessment of structural alterations coupled to a change in functional connectivity after conductive hearing loss. The results and implications for humans consist of structural-functional brain alterations following short term hearing loss in adults.
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Affiliation(s)
| | - Ziqi An
- Guangdong Provincial Key Laboratory of Medical Image Processing, School of Biomedical Engineering, Southern Medical University, Guangzhou, China
- Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou, China
| | - Rachit Kumar
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
- Medical Scientist Training Program, University of Pennsylvania, Philadelphia, PA, United States
| | - Ed X. Wu
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, SAR China
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, SAR China
| | - Jufang He
- Department of Neuroscience, City University of Hong Kong, Hong Kong, SAR China
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, SAR China
| | - Yanqiu Feng
- Guangdong Provincial Key Laboratory of Medical Image Processing, School of Biomedical Engineering, Southern Medical University, Guangzhou, China
- Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou, China
| | - Condon Lau
- Department of Physics, City University of Hong Kong, Hong Kong, SAR China
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Wong E, Radziwon K, Chen GD, Liu X, Manno FA, Manno SH, Auerbach B, Wu EX, Salvi R, Lau C. Functional magnetic resonance imaging of enhanced central auditory gain and electrophysiological correlates in a behavioral model of hyperacusis. Hear Res 2020; 389:107908. [PMID: 32062293 DOI: 10.1016/j.heares.2020.107908] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 12/02/2019] [Accepted: 02/02/2020] [Indexed: 01/24/2023]
Abstract
Hyperacusis is a debilitating hearing condition in which normal everyday sounds are perceived as exceedingly loud, annoying, aversive or even painful. The prevalence of hyperacusis approaches 10%, making it an important, but understudied medical condition. To noninvasively identify the neural correlates of hyperacusis in an animal model, we used sound-evoked functional magnetic resonance imaging (fMRI) to locate regions of abnormal activity in the central nervous system of rats with behavioral evidence of hyperacusis induced with an ototoxic drug (sodium salicylate, 250 mg/kg, i.p.). Reaction time-intensity measures of loudness-growth revealed behavioral evidence of salicylate-induced hyperacusis at high intensities. fMRI revealed significantly enhanced sound-evoked responses in the auditory cortex (AC) to 80 dB SPL tone bursts presented at 8 and 16 kHz. Sound-evoked responses in the inferior colliculus (IC) were also enhanced, but to a lesser extent. To confirm the main results, electrophysiological recordings of spike discharges from multi-unit clusters were obtained from the central auditory pathway. Salicylate significantly enhanced tone-evoked spike-discharges from multi-unit clusters in the AC from 4 to 30 kHz at intensities ≥60 dB SPL; less enhancement occurred in the medial geniculate body (MGB), and even less in the IC. Our results demonstrate for the first time that non-invasive sound-evoked fMRI can be used to identify regions of neural hyperactivity throughout the brain in an animal model of hyperacusis.
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Affiliation(s)
- Eddie Wong
- Department of Physics, City University of Hong Kong, Hong Kong, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China; Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, China
| | - Kelly Radziwon
- Center for Hearing & Deafness, Department of Communicative Disorders and Sciences, SUNY at Buffalo, 137 Cary Hall, Buffalo, NY, 14214, USA
| | - Guang-Di Chen
- Center for Hearing & Deafness, Department of Communicative Disorders and Sciences, SUNY at Buffalo, 137 Cary Hall, Buffalo, NY, 14214, USA
| | - Xiaopeng Liu
- Center for Hearing & Deafness, Department of Communicative Disorders and Sciences, SUNY at Buffalo, 137 Cary Hall, Buffalo, NY, 14214, USA
| | - Francis Am Manno
- Department of Physics, City University of Hong Kong, Hong Kong, China; School of Biomedical Engineering, University of Sydney, Sydney, New South Wales, Australia
| | - Sinai Hc Manno
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - Benjamin Auerbach
- Center for Hearing & Deafness, Department of Communicative Disorders and Sciences, SUNY at Buffalo, 137 Cary Hall, Buffalo, NY, 14214, USA
| | - Ed X Wu
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China; Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, China
| | - Richard Salvi
- Center for Hearing & Deafness, Department of Communicative Disorders and Sciences, SUNY at Buffalo, 137 Cary Hall, Buffalo, NY, 14214, USA; Department of Audiology and Speech-Language Pathology, Asia University, Taichung, Taiwan, ROC.
| | - Condon Lau
- Department of Physics, City University of Hong Kong, Hong Kong, China.
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Dong CM, Leong ATL, Manno FA, Lau C, Ho LC, Chan RW, Feng Y, Gao PP, Wu EX. Functional MRI Investigation of Audiovisual Interactions in Auditory Midbrain. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2018:5527-5530. [PMID: 30441589 DOI: 10.1109/embc.2018.8513629] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The brain integrates information from different sensory modalities to form a representation of the environment and facilitate behavioral responses. The auditory midbrain or inferior colliculus (IC) is a pivotal station in the auditory system, integrating ascending and descending information from various auditory sources and cortical systems. The present study investigated the modulation of auditory responses in the IC by visual stimuli of different frequencies and intensities in rats using functional MRI (fMRI). Low-frequency (1 Hz) high-intensity visual stimulus suppressed IC auditory responses. However, high-frequency (10 Hz) or low-intensity visual stimuli did not alter the IC auditory responses. This finding demonstrates that cross-modal processing occurs in the IC in a manner that depends on the stimulus. Furthermore, only low-frequency high-intensity visual stimulus elicited responses in non-visual cortical regions, suggesting that the above cross-modal modulation effect may arise from top-down cortical feedback. These fMRI results provide insight to guide future studies of cross-modal processing in sensory pathways.
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Lau C, Manno FAM, Dong CM, Chan KC, Wu EX. Auditory-visual convergence at the superior colliculus in rat using functional MRI. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2019; 2018:5531-5536. [PMID: 30441590 DOI: 10.1109/embc.2018.8513633] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The superior colliculus (SC) of the midbrain has been a model structure for multisensory processing. Many neurons in the intermediate and deep SC layers respond to two or more of auditory, visual, and somatosensory stimuli as assessed by electrophysiology. In contrast, noninvasive and large field of view functional magnetic resonance imaging (fMRI) studies have focused on multisensory processing in the cortex. In this study, we applied blood oxygenation leveldependent (BOLD) fMRI on Sprague-Dawley rats receiving monaural (auditory) and binocular (visual) stimuli to study subcortical multisensory processing. Activation was observed in the left superior olivary complex, lateral lemniscus, and inferior colliculus and both hemispheres of the superior colliculus during auditory stimulation. The SC response was bilateral even though the stimulus was monaural. During visual stimulation, activation was observed in both hemispheres of the SC and lateral geniculate nucleus. In both hemispheres of the SC, the number of voxels in the activation area $( \mathrm {p}<10 -8$) and BOLD signal changes $( \mathrm {p}<0.01)$ were significantly greater during visual than auditory stimulation. These results provide functional imaging evidence that the SC is a site of auditoryvisual convergence due to its involvement in both auditory and visual processing. The auditory and visual fMRI activations likely reflect the firing of unisensory and multisensory neurons in the SC. The present study lays the groundwork for noninvasive functional imaging studies of multisensory convergence and integration in the SC.
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Graydon K, Van Dun B, Dowell R, Rance G. The frequency-following response as an assessment of spatial processing. Int J Audiol 2019; 58:497-503. [DOI: 10.1080/14992027.2019.1597285] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Kelley Graydon
- The HEARing Cooperative Research Centre, Carlton, Australia
- Department of Audiology and Speech Pathology, The University of Melbourne, Carlton, Victoria, Australia
| | - Bram Van Dun
- The HEARing Cooperative Research Centre, Carlton, Australia
- National Acoustic Laboratories, Macquarie Park, New South Wales, Australia
| | - Richard Dowell
- The HEARing Cooperative Research Centre, Carlton, Australia
| | - Gary Rance
- The HEARing Cooperative Research Centre, Carlton, Australia
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Leong ATL, Dong CM, Gao PP, Chan RW, To A, Sanes DH, Wu EX. Optogenetic auditory fMRI reveals the effects of visual cortical inputs on auditory midbrain response. Sci Rep 2018; 8:8736. [PMID: 29880842 PMCID: PMC5992211 DOI: 10.1038/s41598-018-26568-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 05/10/2018] [Indexed: 12/20/2022] Open
Abstract
Sensory cortices contain extensive descending (corticofugal) pathways, yet their impact on brainstem processing - particularly across sensory systems - remains poorly understood. In the auditory system, the inferior colliculus (IC) in the midbrain receives cross-modal inputs from the visual cortex (VC). However, the influences from VC on auditory midbrain processing are unclear. To investigate whether and how visual cortical inputs affect IC auditory responses, the present study combines auditory blood-oxygenation-level-dependent (BOLD) functional MRI (fMRI) with cell-type specific optogenetic manipulation of visual cortex. The results show that predominant optogenetic excitation of the excitatory pyramidal neurons in the infragranular layers of the primary VC enhances the noise-evoked BOLD fMRI responses within the IC. This finding reveals that inputs from VC influence and facilitate basic sound processing in the auditory midbrain. Such combined optogenetic and auditory fMRI approach can shed light on the large-scale modulatory effects of corticofugal pathways and guide detailed electrophysiological studies in the future.
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Affiliation(s)
- Alex T L Leong
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Celia M Dong
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Patrick P Gao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Russell W Chan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Anthea To
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Dan H Sanes
- Center for Neural Science, New York University, New York, NY, 10003, United States
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China. .,Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China. .,School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China. .,Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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7
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Yang B, Wong E, Ho WH, Lau C, Chan YS, Wu EX. Reduction of sound-evoked midbrain responses observed by functional magnetic resonance imaging following acute acoustic noise exposure. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 143:2184. [PMID: 29716239 DOI: 10.1121/1.5030920] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Short duration and high intensity acoustic exposures can lead to temporary hearing loss and auditory nerve degeneration. This study investigates central auditory system function following such acute exposures after hearing loss recedes. Adult rats were exposed to 100 dB sound pressure level noise for 15 min. Auditory brainstem responses (ABRs) were recorded with click sounds to check hearing thresholds. Functional magnetic resonance imaging (fMRI) was performed with tonal stimulation at 12 and 20 kHz to investigate central auditory changes. Measurements were performed before exposure (0D), 7 days after (7D), and 14 days after (14D). ABRs show an ∼6 dB threshold shift shortly after exposure, but no significant threshold differences between 0D, 7D, and 14D. fMRI responses are observed in the lateral lemniscus (LL) and inferior colliculus (IC) of the midbrain. In the IC, responses to 12 kHz are 3.1 ± 0.3% (0D), 1.9 ± 0.3% (7D), and 2.9 ± 0.3% (14D) above the baseline magnetic resonance imaging signal. Responses to 20 kHz are 2.0 ± 0.2% (0D), 1.4 ± 0.2% (7D), and 2.1 ± 0.2% (14D). For both tones, responses at 7D are less than those at 0D (p < 0.01) and 14D (p < 0.05). In the LL, similar trends are observed. Acute exposure leads to functional changes in the auditory midbrain with timescale of weeks.
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Affiliation(s)
- Bin Yang
- Department of Physics, The City University of Hong Kong, Hong Kong, People's Republic of China
| | - Eddie Wong
- Department of Physics, The City University of Hong Kong, Hong Kong, People's Republic of China
| | - Wai Hong Ho
- Department of Physics, The City University of Hong Kong, Hong Kong, People's Republic of China
| | - Condon Lau
- Department of Physics, The City University of Hong Kong, Hong Kong, People's Republic of China
| | - Ying Shing Chan
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong, People's Republic of China
| | - Ed X Wu
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, People's Republic of China
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8
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Blazquez Freches G, Chavarrias C, Shemesh N. BOLD-fMRI in the mouse auditory pathway. Neuroimage 2018; 165:265-277. [DOI: 10.1016/j.neuroimage.2017.10.027] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/09/2017] [Accepted: 10/13/2017] [Indexed: 01/31/2023] Open
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9
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Wong E, Yang B, Du L, Ho WH, Lau C, Ke Y, Chan YS, Yung WH, Wu EX. The multi-level impact of chronic intermittent hypoxia on central auditory processing. Neuroimage 2017; 156:232-239. [PMID: 28528846 DOI: 10.1016/j.neuroimage.2017.05.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 04/07/2017] [Accepted: 05/16/2017] [Indexed: 12/21/2022] Open
Abstract
During hypoxia, the tissues do not obtain adequate oxygen. Chronic hypoxia can lead to many health problems. A relatively common cause of chronic hypoxia is sleep apnea. Sleep apnea is a sleep breathing disorder that affects 3-7% of the population. During sleep, the patient's breathing starts and stops. This can lead to hypertension, attention deficits, and hearing disorders. In this study, we apply an established chronic intermittent hypoxemia (CIH) model of sleep apnea to study its impact on auditory processing. Adult rats were reared for seven days during sleeping hours in a gas chamber with oxygen level cycled between 10% and 21% (normal atmosphere) every 90s. During awake hours, the subjects were housed in standard conditions with normal atmosphere. CIH treatment significantly reduces arterial oxygen partial pressure and oxygen saturation during sleeping hours (relative to controls). After treatment, subjects underwent functional magnetic resonance imaging (fMRI) with broadband sound stimulation. Responses are observed in major auditory centers in all subjects, including the auditory cortex (AC) and auditory midbrain. fMRI signals from the AC are statistically significantly increased after CIH by 0.13% in the contralateral hemisphere and 0.10% in the ipsilateral hemisphere. In contrast, signals from the lateral lemniscus of the midbrain are significantly reduced by 0.39%. Signals from the neighboring inferior colliculus of the midbrain are relatively unaffected. Chronic hypoxia affects multiple levels of the auditory system and these changes are likely related to hearing disorders associated with sleep apnea.
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Affiliation(s)
- Eddie Wong
- Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
| | - Bin Yang
- Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Department of Radiology, Children's Hospital of Fudan University, Shanghai, People's Republic of China
| | - Lida Du
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
| | - Wai Hong Ho
- Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
| | - Condon Lau
- Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
| | - Ya Ke
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
| | - Ying Shing Chan
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
| | - Wing Ho Yung
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China
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10
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Tuning to Binaural Cues in Human Auditory Cortex. J Assoc Res Otolaryngol 2016; 17:37-53. [PMID: 26466943 DOI: 10.1007/s10162-015-0546-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 09/25/2015] [Indexed: 10/22/2022] Open
Abstract
Interaural level and time differences (ILD and ITD), the primary binaural cues for sound localization in azimuth, are known to modulate the tuned responses of neurons in mammalian auditory cortex (AC). The majority of these neurons respond best to cue values that favor the contralateral ear, such that contralateral bias is evident in the overall population response and thereby expected in population-level functional imaging data. Human neuroimaging studies, however, have not consistently found contralaterally biased binaural response patterns. Here, we used functional magnetic resonance imaging (fMRI) to parametrically measure ILD and ITD tuning in human AC. For ILD, contralateral tuning was observed, using both univariate and multivoxel analyses, in posterior superior temporal gyrus (pSTG) in both hemispheres. Response-ILD functions were U-shaped, revealing responsiveness to both contralateral and—to a lesser degree—ipsilateral ILD values, consistent with rate coding by unequal populations of contralaterally and ipsilaterally tuned neurons. In contrast, for ITD, univariate analyses showed modest contralateral tuning only in left pSTG, characterized by a monotonic response-ITD function. A multivoxel classifier, however, revealed ITD coding in both hemispheres. Although sensitivity to ILD and ITD was distributed in similar AC regions, the differently shaped response functions and different response patterns across hemispheres suggest that basic ILD and ITD processes are not fully integrated in human AC. The results support opponent-channel theories of ILD but not necessarily ITD coding, the latter of which may involve multiple types of representation that differ across hemispheres.
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11
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Lau C, Pienkowski M, Zhang JW, McPherson B, Wu EX. Chronic exposure to broadband noise at moderate sound pressure levels spatially shifts tone-evoked responses in the rat auditory midbrain. Neuroimage 2015; 122:44-51. [DOI: 10.1016/j.neuroimage.2015.07.065] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 07/10/2015] [Accepted: 07/24/2015] [Indexed: 02/09/2023] Open
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12
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Gao PP, Zhang JW, Fan SJ, Sanes DH, Wu EX. Auditory midbrain processing is differentially modulated by auditory and visual cortices: An auditory fMRI study. Neuroimage 2015; 123:22-32. [PMID: 26306991 DOI: 10.1016/j.neuroimage.2015.08.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/15/2015] [Accepted: 08/18/2015] [Indexed: 11/19/2022] Open
Abstract
The cortex contains extensive descending projections, yet the impact of cortical input on brainstem processing remains poorly understood. In the central auditory system, the auditory cortex contains direct and indirect pathways (via brainstem cholinergic cells) to nuclei of the auditory midbrain, called the inferior colliculus (IC). While these projections modulate auditory processing throughout the IC, single neuron recordings have samples from only a small fraction of cells during stimulation of the corticofugal pathway. Furthermore, assessments of cortical feedback have not been extended to sensory modalities other than audition. To address these issues, we devised blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) paradigms to measure the sound-evoked responses throughout the rat IC and investigated the effects of bilateral ablation of either auditory or visual cortices. Auditory cortex ablation increased the gain of IC responses to noise stimuli (primarily in the central nucleus of the IC) and decreased response selectivity to forward species-specific vocalizations (versus temporally reversed ones, most prominently in the external cortex of the IC). In contrast, visual cortex ablation decreased the gain and induced a much smaller effect on response selectivity. The results suggest that auditory cortical projections normally exert a large-scale and net suppressive influence on specific IC subnuclei, while visual cortical projections provide a facilitatory influence. Meanwhile, auditory cortical projections enhance the midbrain response selectivity to species-specific vocalizations. We also probed the role of the indirect cholinergic projections in the auditory system in the descending modulation process by pharmacologically blocking muscarinic cholinergic receptors. This manipulation did not affect the gain of IC responses but significantly reduced the response selectivity to vocalizations. The results imply that auditory cortical gain modulation is mediated primarily through direct projections and they point to future investigations of the differential roles of the direct and indirect projections in corticofugal modulation. In summary, our imaging findings demonstrate the large-scale descending influences, from both the auditory and visual cortices, on sound processing in different IC subdivisions. They can guide future studies on the coordinated activity across multiple regions of the auditory network, and its dysfunctions.
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Affiliation(s)
- Patrick P Gao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Jevin W Zhang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Shu-Juan Fan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Dan H Sanes
- Center for Neural Science, New York University, New York, NY 10003, United States
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Anatomy, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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13
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Gao PP, Zhang JW, Chan RW, Leong ATL, Wu EX. BOLD fMRI study of ultrahigh frequency encoding in the inferior colliculus. Neuroimage 2015; 114:427-37. [PMID: 25869860 DOI: 10.1016/j.neuroimage.2015.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/02/2015] [Accepted: 04/02/2015] [Indexed: 01/23/2023] Open
Abstract
Many vertebrates communicate with ultrahigh frequency (UHF) vocalizations to limit auditory detection by predators. The mechanisms underlying the neural encoding of such UHF sounds may provide important insights for understanding neural processing of other complex sounds (e.g. human speeches). In the auditory system, sound frequency is normally encoded topographically as tonotopy, which, however, contains very limited representation of UHFs in many species. Instead, electrophysiological studies suggested that two neural mechanisms, both exploiting the interactions between frequencies, may contribute to UHF processing. Neurons can exhibit excitatory or inhibitory responses to a tone when another UHF tone is presented simultaneously (combination sensitivity). They can also respond to such stimulation if they are tuned to the frequency of the cochlear-generated distortion products of the two tones, e.g. their difference frequency (cochlear distortion). Both mechanisms are present in an early station of the auditory pathway, the midbrain inferior colliculus (IC). Currently, it is unclear how prevalent the two mechanisms are and how they are functionally integrated in encoding UHFs. This study investigated these issues with large-view BOLD fMRI in rat auditory system, particularly the IC. UHF vocalizations (above 40kHz), but not pure tones at similar frequencies (45, 55, 65, 75kHz), evoked robust BOLD responses in multiple auditory nuclei, including the IC, reinforcing the sensitivity of the auditory system to UHFs despite limited representation in tonotopy. Furthermore, BOLD responses were detected in the IC when a pair of UHF pure tones was presented simultaneously (45 & 55kHz, 55 & 65kHz, 45 & 65kHz, 45 & 75kHz). For all four pairs, a cluster of voxels in the ventromedial side always showed the strongest responses, displaying combination sensitivity. Meanwhile, voxels in the dorsolateral side that showed strongest secondary responses to each pair of UHF pure tones also showed the strongest responses to a pure tone at their difference frequency, suggesting that they are sensitive to cochlear distortion. These BOLD fMRI results indicated that combination sensitivity and cochlear distortion are employed by large but spatially distinctive neuron populations in the IC to represent UHFs. Our imaging findings provided insights for understanding sound feature encoding in the early stage of the auditory pathway.
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Affiliation(s)
- Patrick P Gao
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Jevin W Zhang
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Russell W Chan
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Alex T L Leong
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
| | - Ed X Wu
- Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Anatomy, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; Department of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
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Lau C, Zhang JW, McPherson B, Pienkowski M, Wu EX. Long-term, passive exposure to non-traumatic acoustic noise induces neural adaptation in the adult rat medial geniculate body and auditory cortex. Neuroimage 2015; 107:1-9. [DOI: 10.1016/j.neuroimage.2014.11.048] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/12/2014] [Accepted: 11/22/2014] [Indexed: 02/02/2023] Open
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The inferior colliculus is involved in deviant sound detection as revealed by BOLD fMRI. Neuroimage 2014; 91:220-7. [PMID: 24486979 DOI: 10.1016/j.neuroimage.2014.01.043] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 01/23/2014] [Accepted: 01/24/2014] [Indexed: 11/24/2022] Open
Abstract
Rapid detection of deviant sounds is a crucial property of the auditory system because it increases the saliency of biologically important, unexpected sounds. The oddball paradigm in which a deviant sound is randomly interspersed among a train of standard sounds has been traditionally used to study this property in mammals. Currently, most human studies have only revealed the involvement of cortical regions in this property. Recently, several animal electrophysiological studies have reported that neurons in the inferior colliculus (IC) exhibit reduced responses to a standard sound but restore their responses at the occurrence of a deviant sound (i.e., stimulus-specific adaptation or SSA), suggesting that the IC may also be involved in deviance detection. However, by adopting an invasive method, these animal studies examined only a limited number of neurons. Although SSA appears to be more prominent in the external cortical nuclei of the IC for frequency deviant, a thorough investigation of this property throughout the IC using other deviants and efficient imaging techniques may provide more comprehensive information on this important phenomenon. In this study, blood-oxygen-level-dependent (BOLD) fMRI with a large field of view was applied to investigate the role of the IC in deviance detection. Two sound tokens that had identical frequency spectrum but temporally inverted profiles were used as the deviant and standard. A control experiment showed that these two sounds evoked the same responses in the IC when they were separately presented. Two oddball experiments showed that the deviant induced higher responses than the standard (by 0.41±0.09% and 0.41±0.10%, respectively). The most activated voxels were in the medial side of the IC in both oddball experiments. The results clearly demonstrated that the IC is involved in deviance detection. BOLD fMRI detection of increased activities in the medial side of the IC to the deviant revealed the highly adaptive nature of a substantial population of neurons in this region, probably those that belong to the rostral or dorsal cortex of the IC. These findings highlighted the complexity of auditory information processing in the IC and may guide future studies of the functional organizations of this subcortical structure.
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