Evidence for a Glutamatergic Pathway from the Guinea Pig Auditory Cortex to the Inferior Colliculus

Feliciano, Maribel; Potashner, S.J.

doi:10.1046/j.1471-4159.1995.65031348.x

Cited by 131 publications

(103 citation statements)

References 52 publications

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“…The shortest latency responses to cortical stimulation (1.0 -1.4 msec) were always excitatory, and the authors concluded they were probably monosynaptic. This is consistent with work suggesting that the corticocollicular axons use glutamate as a neurotransmitter (Feliciano and Potashner 1995). Longer latency responses (1.8 -4.2 msec) included excitatory and inhibitory effects, and are likely to include di-or multisynaptic circuits.…”

Section: Cortical Effects On Ic Cellssupporting

confidence: 87%

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Peterson

Schofield

2007

Hearing Research

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The superior olivary complex (SOC) and inferior colliculus (IC) are targets of cortical projections as well as sources of major ascending auditory pathways. This study examines whether the cortical projections contact cells in the SOC or IC that project to higher levels. First, we placed an anterograde tracer into the auditory cortex to label cortico-olivary axons and a retrograde tracer into the IC to label olivocollicular cells in guinea pigs. Cortical axons contacted many labeled cells in the ipsilateral SOC and fewer labeled cells in the contralateral SOC. Contacted cells projected to the ipsilateral or contralateral IC.In a second experiment, we labeled corticocollicular axons with an anterograde tracer and injected retrograde tracers into the medial geniculate (MG) to label colliculogeniculate cells. In the IC ipsilateral to the cortical injection, many cortical axons contacted colliculogeniculate cells in the dorsal cortex and external cortex of the IC. The contacted cells projected to the ipsilateral MG or, less often, to the contralateral MG.The results indicate that cortical projections are likely to contact cells in the SOC and IC that project to higher centers. This suggests that auditory cortex can modulate the ascending auditory pathways at multiple levels of the brainstem.

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Section: Cortical Effects On Ic Cellssupporting

confidence: 87%

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Peterson

Schofield

2007

Hearing Research

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“…Previous data support the role of glutamate as the main excitatory neurotransmitter in the inferior colliculus (Faingold, 2002;Caicedo and Eybalin, 1999;Feliciano and Potashner, 1995;Gaza and Ribak, 1997;Goldsmith et al, 1995;Helfert et al, 1999;Liao et al, 2000;Moore et al, 1998;Parks, 2000;Saint Marie, 1996;Suneja et al, 1995Suneja et al, , 2000. In addition, glutamine and glutamate have numerous functions in different organs working as precursors for neurotransmitters, related proteins, nucleotides, nucleic acids and glutathione synthesis.…”

Section: Introductionmentioning

confidence: 68%

Glutamate-related gene expression changes with age in the mouse auditory midbrain

et al. 2007

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Glutamate is the main excitatory neurotransmitter in both the peripheral and central auditory systems. Changes of glutamate and glutamate-related genes with age may be an important factor in the pathogenesis of age-related hearing loss -presbycusis. In this study, changes in glutamate-related mRNA gene expression in the CBA mouse inferior colliculus with age and hearing loss were examined and correlations were sought between these changes and functional hearing measures, such as the auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs). Gene expression of 68 glutamate-related genes was investigated using both genechip microarray and real-time PCR (qPCR) molecular techniques for four different age/hearing loss CBA mouse subject groups. Two genes showed consistent differences between groups for both the genechip and qPCR. Pyrroline-5-carboxylate synthetase enzyme (Pycs) showed down-regulation with age and a highaffinity glutamate transporter (Slc1a3) showed up-regulation with age and hearing loss. Since Pycs plays a role in converting glutamate to proline, its deficiency in old age may lead to both glutamate increases and proline deficiencies in the auditory midbrain, playing a role in the subsequent inducement of glutamate toxicity and loss of proline neuroprotective effects. The up-regulation of Slc1a3 gene expression may reflect a cellular compensatory mechanism to protect against age-related glutamate or calcium excitoxicity.

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“…In some of the responses, antidromic spike activity was also observed. Anatomical studies (Feliciano and Potashner 1995;Winer 2005;Winer et al 1998) showed that monosynaptic corticofugal projections exist from A1 to ICC and that electrical stimulation within ICC can antidromically activate cortical neurons originating from layer V (Mitani and Shimokouchi 1985). Although we attempted to position our recording sites in layer IV of A1, it is possible that some of our responses were contaminated with antidromic spike activity recorded from layer V. There is also evidence, at least for projections from the visual cortex to the superior colliculus, that antidromically activated dendritic processes extending from corticotectal cells located in layer V can elicit spike activity in layers III and IV of the cortex (Schofield et al 1987).…”

Section: Discussionmentioning

confidence: 99%

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

Lim¹,

Anderson²

2007

Journal of Neurophysiology

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. Auditory cortical responses to electrical stimulation of the inferior colliculus: implications for an auditory midbrain implant. J Neurophysiol 96: 975-988, 2006. First published May 24, 2006 doi:10.1152/jn.01112.2005. The success and limitations of cochlear implants (CIs) along with recent advances in deep brain stimulation and neural engineering have motivated the development of a central auditory prosthesis. In this study, we investigated the effects of electrical stimulation of the inferior colliculus central nucleus (ICC) on primary auditory cortex (A1) activity to determine the potential benefits of an auditory midbrain implant (AMI). We recorded multiunit activity in A1 of ketamine-anesthetized guinea pigs in response to single-pulse (200 s/phase) monopolar stimulation of the ICC using multisite silicon-substrate probes. We then compared measures of threshold, dynamic range, and tonotopic spread of activation for ICC stimulation with that of published data for CI stimulation. Our results showed that compared with cochlear stimulation, ICC stimulation achieved: 1) thresholds about 8 dB lower; 2) dynamic ranges Ն4 dB greater; and 3) more localized, frequency-specific activation, even though frequency specificity was partially lost at higher stimulus levels for low-frequency ICC regions. Our results also showed that stimulation of rostral ICC regions elicited lower thresholds but with greater activation spread along the tonotopic gradient of A1 than did stimulation of more caudal regions. These results suggest that an AMI may improve frequency and level coding with lower energy requirements compared with CIs. However, a trade-off between lower perceptual thresholds and better frequency discrimination may exist that depends on location of stimulation along the caudorostral dimension of the ICC. Overall, this study provides the foundation for future AMI research and development.

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Evidence for a Glutamatergic Pathway from the Guinea Pig Auditory Cortex to the Inferior Colliculus

Cited by 131 publications

References 52 publications

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Projections from auditory cortex contact ascending pathways that originate in the superior olive and inferior colliculus

Glutamate-related gene expression changes with age in the mouse auditory midbrain

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

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