scholarly journals Dynamics of synaptic extracellular field potentials in the nucleus laminaris of the barn owl

2019 ◽  
Vol 121 (3) ◽  
pp. 1034-1047
Author(s):  
Thomas McColgan ◽  
Paula T. Kuokkanen ◽  
Catherine E. Carr ◽  
Richard Kempter
Keyword(s):  
Brain Stem ◽  
Field Potential ◽  
Barn Owl ◽  
Fast Time ◽  
Short Term ◽  
Synaptic Currents ◽  
Time Constants ◽  
Nucleus Laminaris ◽  
Iontophoretic Application ◽  
Auditory Brain Stem

Synaptic currents are frequently assumed to make a major contribution to the extracellular field potential (EFP). However, in any neuronal population, the explicit separation of synaptic sources from other contributions such as postsynaptic spikes remains a challenge. Here we take advantage of the simple organization of the barn owl nucleus laminaris (NL) in the auditory brain stem to isolate synaptic currents through the iontophoretic application of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[ f]quinoxaline-7-sulfonamide (NBQX). Responses to auditory stimulation show that the temporal dynamics of the evoked synaptic contributions to the EFP are consistent with synaptic short-term depression (STD). The estimated time constants of an STD model fitted to the data are similar to the fast time constants reported from in vitro experiments in the chick. Overall, the putative synaptic EFPs in the barn owl NL are significant but small (<1% change of the variance by NBQX). This result supports the hypothesis that the EFP in NL is generated mainly by axonal spikes, in contrast to most other neuronal systems. NEW & NOTEWORTHY Synaptic currents are assumed to make a major contribution to the extracellular field potential in the brain, but it is hard to directly isolate these synaptic components. Here we take advantage of the simple organization of the barn owl nucleus laminaris in the auditory brain stem to isolate synaptic currents through the iontophoretic application of a synaptic blocker. We show that the responses are consistent with a simple model of short-term synaptic depression.

scholarly journals Maps of interaural delay in the owl's nucleus laminaris

2015 ◽  
Vol 114 (3) ◽  
pp. 1862-1873 ◽  
Author(s):  
Catherine E. Carr ◽  
Sahil Shah ◽  
Thomas McColgan ◽  
Go Ashida ◽  
Paula T. Kuokkanen ◽  
...  
Keyword(s):  
Conduction Velocity ◽  
Delay Line ◽  
Field Potential ◽  
Barn Owl ◽  
Conduction Delay ◽  
Interaural Time Differences ◽  
Nucleus Laminaris ◽  
Nucleus Magnocellularis

Axons from the nucleus magnocellularis form a presynaptic map of interaural time differences (ITDs) in the nucleus laminaris (NL). These inputs generate a field potential that varies systematically with recording position and can be used to measure the map of ITDs. In the barn owl, the representation of best ITD shifts with mediolateral position in NL, so as to form continuous, smoothly overlapping maps of ITD with iso-ITD contours that are not parallel to the NL border. Frontal space (0°) is, however, represented throughout and thus overrepresented with respect to the periphery. Measurements of presynaptic conduction delay, combined with a model of delay line conduction velocity, reveal that conduction delays can account for the mediolateral shifts in the map of ITD.

scholarly journals A Role for Short-Term Synaptic Facilitation and Depression in the Processing of Intensity Information in the Auditory Brain Stem

2007 ◽  
Vol 97 (4) ◽  
pp. 2863-2874 ◽  
Author(s):  
K. M. MacLeod ◽  
T. K. Horiuchi ◽  
C. E. Carr
Keyword(s):  
Synaptic Plasticity ◽  
Brain Stem ◽  
Time Constant ◽  
Cochlear Nucleus ◽  
Auditory Nerve ◽  
Brain Slices ◽  
Fast Time ◽  
Short Term ◽  
Intensity Information

The nature of the synaptic connection from the auditory nerve onto the cochlear nucleus neurons has a profound impact on how sound information is transmitted. Short-term synaptic plasticity, by dynamically modulating synaptic strength, filters information contained in the firing patterns. In the sound-localization circuits of the brain stem, the synapses of the timing pathway are characterized by strong short-term depression. We investigated the short-term synaptic plasticity of the inputs to the bird's cochlear nucleus angularis (NA), which encodes intensity information, by using chick embryonic brain slices and trains of electrical stimulation. These excitatory inputs expressed a mixture of short-term facilitation and depression, unlike those in the timing nuclei that only depressed. Facilitation and depression at NA synapses were balanced such that postsynaptic response amplitude was often maintained throughout the train at high firing rates (>100 Hz). The steady-state input rate relationship of the balanced synapses linearly conveyed rate information and therefore transmits intensity information encoded as a rate code in the nerve. A quantitative model of synaptic transmission could account for the plasticity by including facilitation of release (with a time constant of ∼40 ms), and a two-step recovery from depression (with one slow time constant of ∼8 s, and one fast time constant of ∼20 ms). A simulation using the model fit to NA synapses and auditory nerve spike trains from recordings in vivo confirmed that these synapses can convey intensity information contained in natural train inputs.

scholarly journals On the Origin of the Extracellular Field Potential in the Nucleus Laminaris of the Barn Owl (Tyto alba)

2010 ◽  
Vol 104 (4) ◽  
pp. 2274-2290 ◽  
Author(s):  
Paula T. Kuokkanen ◽  
Hermann Wagner ◽  
Go Ashida ◽  
Catherine E. Carr ◽  
Richard Kempter
Keyword(s):  
Signal To Noise Ratio ◽  
Phase Locking ◽  
Field Potential ◽  
Barn Owl ◽  
Tyto Alba ◽  
Signal To Noise ◽  
Nucleus Laminaris ◽  
Temporal Precision ◽  
Noise Ratio ◽  
Vector Strength

The neurophonic is a sound-evoked, frequency-following potential that can be recorded extracellularly in nucleus laminaris of the barn owl. The origin of the neurophonic, and thus the mechanisms that give rise to its exceptional temporal precision, has not yet been identified. Putative generators of the neurophonic are the activity of afferent axons, synaptic activation of laminaris neurons, or action potentials in laminaris neurons. To identify the generators, we analyzed the neurophonic in the high-frequency (>2.5 kHz) region of nucleus laminaris in response to monaural pure-tone stimulation. The amplitude of the neurophonic is typically in the millivolt range. The signal-to-noise ratio reaches values beyond 30 dB. To assess which generators could give rise to these large, synchronous extracellular potentials, we developed a computational model. Spike trains were produced by an inhomogeneous Poisson process and convolved with a spike waveform. The model explained the dependence of the simulated neurophonic on parameters such as the mean rate, the vector strength of phase locking, the number of statistically independent sources, and why the signal-to-noise ratio is independent of the spike waveform and subsequent filtering of the signal. We found that several hundred sources are needed to reach the observed signal-to-noise ratio. The summed coherent signal from the densely packed afferent axons and activation of their synapses on laminaris neurons are alone sufficient to explain the measured properties of the neurophonic.

Can mobile phone emissions affect auditory functions of cochlea or brain stem?

2005 ◽  
Vol 132 (3) ◽  
pp. 451-455 ◽  
Author(s):  
UWE Sievert ◽  
Siegfried Eggert ◽  
Hans Wilhelm Pau
Keyword(s):  
Adverse Effects ◽  
Mobile Phone ◽  
Brain Stem ◽  
Inner Ear ◽  
Sense Organ ◽  
Previous Article ◽  
Short Term ◽  
Auditory Brain Stem ◽  
Electromagnetic Emissions ◽  
Brain Stem Reflexes

PROBLEMS ADDRESSED: Despite their abundant spread, mobile phones are suspected by a major share of the population to cause adverse effects on health and welfare. The ear as the sense organ next to the individual device has rarely been Investigated for short-term effects in this regard. In a previous article, we could not prove any impact on the vestibular part of the inner ear. Our present examinations are concerned with the question whether mobile phone emissions could affect cochlear or auditory brain stem functions. METHODS AND MEASURES: In 12 healthy test persons with normal hearing, auditory brain stem reflexes recordings were performed before, during, and after exposure to electromagnetic emissions by standardized mobile phone devices. Two modes of electromagnetic emissions fields were administered: pulsed and continuous. For acoustic stimulation simultaneous to field exposure, special “plug-in” earphones had to be used. RESULTS: No impact on auditory brain stem reflexes recordings in terms of absolute and interpeak latencies could be found. CLINICAL SIGNIFICANCE: Together with the results of a previous article concerned with the vestibular part of the inner ear, we can state that there are no adverse effects of mobile phone emissions on the ear function, at least on a short-term range. Of course, any long-term effects cannot be excluded by our study.

scholarly journals Contribution of action potentials to the extracellular field potential in the nucleus laminaris of barn owl

2018 ◽  
Vol 119 (4) ◽  
pp. 1422-1436 ◽  
Author(s):  
Paula T. Kuokkanen ◽  
Go Ashida ◽  
Anna Kraemer ◽  
Thomas McColgan ◽  
Kazuo Funabiki ◽  
...  
Keyword(s):  
Spectral Power ◽  
Spectral Component ◽  
Field Potential ◽  
Barn Owl ◽  
Field Potentials ◽  
Multiple Sources ◽  
Nucleus Laminaris ◽  
Power Spectral ◽  
Spectral Components

Extracellular field potentials (EFP) are widely used to evaluate in vivo neural activity, but identification of multiple sources and their relative contributions is often ambiguous, making the interpretation of the EFP difficult. We have therefore analyzed a model EFP from a simple brainstem circuit with separable pre- and postsynaptic components to determine whether we could isolate its sources. Our previous papers had shown that the barn owl neurophonic largely originates with spikes from input axons and synapses that terminate on the neurons in the nucleus laminaris (NL) (Kuokkanen PT, Wagner H, Ashida G, Carr CE, Kempter R. J Neurophysiol 104: 2274–2290, 2010; Kuokkanen PT, Ashida G, Carr CE, Wagner H, Kempter R. J Neurophysiol 110: 117–130, 2013; McColgan T, Liu J, Kuokkanen PT, Carr CE, Wagner H, Kempter R. eLife 6: e26106, 2017). To determine how much the postsynaptic NL neurons contributed to the neurophonic, we recorded EFP responses in NL in vivo. Power spectral analyses showed that a small spectral component of the evoked response, between 200 and 700 Hz, could be attributed to the NL neurons’ spikes, while nucleus magnocellularis (NM) spikes dominate the EFP at frequencies ≳1 kHz. Thus, spikes of NL neurons and NM axons contribute to the EFP in NL in distinct frequency bands. We conclude that if the spectral components of source types are different and if their activities can be selectively modulated, the identification of EFP sources is possible. NEW & NOTEWORTHY Extracellular field potentials (EFPs) generate clinically important signals, but their sources are incompletely understood. As a model, we have analyzed the auditory neurophonic in the barn owl’s nucleus laminaris. There the EFP originates predominantly from spiking in the afferent axons, with spectral power ≳1 kHz, while postsynaptic laminaris neurons contribute little. In conclusion, the identification of EFP sources is possible if they have different spectral components and if their activities can be modulated selectively.

scholarly journals Can auditory brain stem response accurately reflect the cochlear function?

2020 ◽  
Vol 124 (6) ◽  
pp. 1667-1675
Author(s):  
Dalian Ding ◽  
Jianhui Zhang ◽  
Wenjuan Li ◽  
Dong Li ◽  
Jintao Yu ◽  
...  
Keyword(s):  
Brain Stem ◽  
Damage Model ◽  
Compound Action Potential ◽  
Cochlear Function ◽  
Auditory Brain Stem Response ◽  
Threshold Difference ◽  
Auditory Brain Stem ◽  
Cochlear Damage ◽  
Brain Stem Response ◽  
Compound Action

Auditory brain stem response (ABR) is more commonly used to evaluate cochlear lesions than cochlear compound action potential (CAP). In a noise-induced cochlear damage model, we found that the reduced CAP and enhanced ABR caused the threshold difference. In a unilateral cochlear destruction model, a shadow curve of the ABR from the contralateral healthy ear masked the hearing loss in the destroyed ear.

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