scholarly journals Serotonin 1B Receptor Modulates Frequency Response Curves and Spectral Integration in the Inferior Colliculus by Reducing GABAergic Inhibition

2008 ◽  
Vol 100 (3) ◽  
pp. 1656-1667 ◽  
Author(s):  
Laura M. Hurley ◽  
Jo Anne Tracy ◽  
Alexander Bohorquez
Keyword(s):  
Frequency Response ◽  
Inferior Colliculus ◽  
Extracellular Recording ◽  
Evoked Responses ◽  
Auditory Midbrain ◽  
Response Curves ◽  
Response Characteristics ◽  
Spectral Integration ◽  
Serotonin 1B Receptor

The selectivity of sensory neurons for stimuli is often shaped by a balance between excitatory and inhibitory inputs, making this balance an effective target for regulation. In the inferior colliculus (IC), an auditory midbrain nucleus, the amplitude and selectivity of frequency response curves are altered by the neuromodulator serotonin, but the changes in excitatory-inhibitory balance that mediate this plasticity are not well understood. Previous findings suggest that the presynaptic 5-HT1B receptor may act to decrease the release of GABA onto IC neurons. Here, in vivo extracellular recording and iontophoresis of the selective 5-HT1B agonist CP93129 were used to characterize inhibition within and surrounding frequency response curves using two-tone protocols to indirectly measure inhibition as a decrease in spikes relative to an excitatory tone alone. The 5-HT1B agonist attenuated such two-tone spike reduction in a varied pattern among neurons, suggesting that the function of 5-HT1B modulation also varies. The hypothesis that the 5-HT1B receptor reduces inhibition was tested by comparing the effects of CP93129 and the GABAA antagonists bicuculline and gabazine in the same neurons. The effects of GABAA antagonists on spike count, tuning bandwidth, two-tone ratio, and temporal response characteristics mimicked those of CP93129 across the neuron population. GABAA antagonists also blocked or reduced the facilitation of evoked responses by CP93129. These results are all consistent with the reduction of GABAA-mediated inhibition by 5-HT1B receptors in the IC, resulting in an increase in the level of evoked responses in some neurons, and a decrease in spectral selectivity in others.

A Quantitative Evaluation of the Frequency-Response Characteristics of Active Human Skeletal Muscle In Vivo

1979 ◽  
Vol 101 (1) ◽  
pp. 28-37 ◽  
Author(s):  
G. I. Zahalak ◽  
S. J. Heyman
Keyword(s):  
Skeletal Muscle ◽  
Frequency Response ◽  
Human Skeletal Muscle ◽  
Muscle Stiffness ◽  
Forced Oscillations ◽  
Muscle Stretch ◽  
Gain Parameter ◽  
Response Characteristics ◽  
Frequency Response Characteristics

This paper describes an investigation of the frequency-response characteristics of active human skeletal muscle in vivo over the frequency range 1 Hz to 15 Hz. The applied force, forearm position, and surface electromyograms (from biceps, triceps, and brachioradialis) were recorded simultaneously in four normal adult male subjects for small oscillations of the forearm about a mean position of 90 deg flexion. Two modes of oscillatory behavior are discussed: externally forced oscillations under constant muscle force and voluntary oscillations against an elastic resistance. The observed amplitude and phase relations are presented herein and are compared to the response predicted by a simple model for neuromuscular dynamics. It appears that the small amplitude frequency response of normal skeletal muscle in vivo can be represented by a second order model. The main muscle parameters of this model are a muscular stiffness K, two time constants τ1 and τ2 associated with contraction dynamics, and a time delay τ: typical values of these parameters at moderate contraction levels (approximately 20 percent of maximum voluntary effort) are K = 100 N · m/rad, τ1 and τ2 = 50 ms, and τ = 10 ms. Reflex feedback under forced-oscillation conditions was also examined and may be characterized by a gain parameter (ΔE/Δθ), the ratio of the surface EMG amplitude to the angular displacement of the forearm, and the phase by which the EMG leads muscle stretch. The reflex EMG is observed to lead muscle stretch at all frequencies between 1 Hz and 15 Hz. The muscle stiffness K and the reflex gain parameter (ΔE/Δθ) are approximately proportional to the average force of contraction.

Numerical Study of a New Variable Friction TMD

2011 ◽  
Vol 243-249 ◽  
pp. 5450-5457 ◽  
Author(s):  
Li Qin ◽  
Wei Ming Yan ◽  
Sheng Bo Guo
Keyword(s):  
Frequency Response ◽  
Numerical Study ◽  
Damping Ratio ◽  
Harmonic Balance Method ◽  
Structural Response ◽  
Harmonic Excitation ◽  
Response Curves ◽  
Equivalent Damping ◽  
Response Characteristics ◽  
Variable Friction

The paper proposes a new variable friction system, of which the friction force can increase linearly with the displacement of system. This new system can be used in TMD to avoid the disadvantage of Coulomb friction TMD. Using first order harmonic balance method, the equivalent damping ratio and frequency of SDOF variable friction system is deduced and analyzed. The frequency response characteristics of SDOF variable friction system is discussed. The control effectiveness of variable friction TMD under harmonic excitation is analyzed theoretically. The results demonstrate that the frequency response curves of variable friction TMD and classically damped TMD are similar and both can effectively reduce structural response under harmonic excitation.

The commissure of the inferior colliculus shapes frequency response areas in rat: an in vivo study using reversible blockade with microinjection of kynurenic acid

2003 ◽  
Vol 153 (4) ◽  
pp. 522-529 ◽  
Author(s):  
Manuel S. Malmierca ◽  
Olga Hern�ndez ◽  
Atilio Falconi ◽  
Enrique A. Lopez-Poveda ◽  
Miguel Merch�n ◽  
...  
Keyword(s):  
Frequency Response ◽  
Inferior Colliculus ◽  
Kynurenic Acid ◽  
In Vivo Study

scholarly journals Intra-patch clustering in mysid swarms revealed through multifrequency acoustics

2013 ◽  
Vol 70 (4) ◽  
pp. 883-891 ◽  
Author(s):  
Amanda M. Kaltenberg ◽  
Kelly J. Benoit-Bird
Keyword(s):  
Frequency Response ◽  
Coastal Waters ◽  
Patch Dynamics ◽  
Size Class ◽  
Response Curves ◽  
Response Characteristics ◽  
Patch Clustering ◽  
Frequency Response Characteristics ◽  
Large Predator ◽  
Single Size

Abstract Kaltenberg, A. M., and Benoit-Bird, K. J. 2013. Intra-patch clustering in mysid swarms revealed through multifrequency acoustics. – ICES Journal of Marine Science, 70: 883–891. Simultaneous multifrequency acoustic echosounders (70, 120, 200, 333, and 710 kHz), net tows, and video sampling were conducted on dense mysid aggregations in coastal waters off OR, USA, to study intra-patch dynamics in mysid swarms. Multifrequency differencing techniques demonstrated submetre, intra-patch clustering of individual mysids of different frequency response characteristics in all 33 samples collected. For samples that contained multiple sizes of mysids, frequency response curves showed a consistent peak 200 kHz. Samples dominated by only a single size class of small (5 mm long mysids) had a peak in scattering at 710 kHz. Intra-patch clustering of heterogeneous individuals shown here demonstrates patchiness at the scales of interactions among individual mysids; however, this patchiness is likely averaged out at the scale of large predator–mysid swarm interactions or the scale typical of most scientific surveys.

Rapid resetting of aortic baroreceptors in vitro

1983 ◽  
Vol 244 (5) ◽  
pp. H672-H680 ◽  
Author(s):  
P. A. Munch ◽  
M. C. Andresen ◽  
A. M. Brown
Keyword(s):  
Time Course ◽  
Response Curves ◽  
Response Characteristics ◽  
Pressure Threshold ◽  
Pressure Axis ◽  
Wistar Kyoto ◽  
Change In Mean ◽  
Aortic Baroreceptors

Pressure-response characteristics of arterial baroreceptors (BR) were shown recently to be reset following a 15- to 20-min change in mean arterial pressure (MAP); the curves shifted in the direction of the MAP change. To characterize this rapid BR resetting process more precisely than in vitro studies allow, we utilized an in vitro aortic arch-aortic nerve preparation from Wistar-Kyoto rats. Pressure ramps were used to determine the discharge response curves of single BRs following exposure to precisely controlled conditioning pressures. Rapid resetting occurred in all BRs and followed an exponential time course with a 3- to 5-min time constant. The reset curves were stable for 1 h and were completely reversible. The curves were shifted along the pressure axis in a parallel manner, i.e., pressure threshold (Pth) changed but slope and mean asymptotic discharge were unaltered. In experiments lasting as long as 7 h in which more than two MAP steps were possible, in vitro rapid resetting was a very consistent and reproducible process. Quantitatively, the extent of resetting (delta Pth/delta MAP) averaged 0.33 over an MAP range of 40-160 mmHg. In vitro resetting therefore appears very similar to that observed in vivo, suggesting that the conditioning pressure is the primary, perhaps the sole, determinant of resetting. Resetting occurred at subthreshold MAPs, demonstrating action potentials are not a prerequisite. Efferent neural or hormonal influences are also not required.

scholarly journals Unifying the Midbrain

2018 ◽  
pp. 548-576
Author(s):  
Adrian Rees ◽  
Llwyd D. Orton
Keyword(s):  
Inferior Colliculus ◽  
Auditory Processing ◽  
Auditory Pathway ◽  
Neural Representation ◽  
Central Nucleus ◽  
Dorsal Cortex ◽  
Auditory Midbrain ◽  
Inferior Colliculi ◽  
Behavioral Influences

Commissural fibres interconnecting the two sides of the brain are found at several points along the auditory pathway, thus suggesting their fundamental importance for the analysis of sound. This chapter presents an overview of what is currently known about the anatomy, physiology, and behavioral influences of the commissure of the inferior colliculus (CoIC)—the most prominent brainstem auditory commissure—that reciprocally interconnects the principal nuclei of the auditory midbrain, the inferior colliculi (IC). The primary contribution to the CoIC originates from neurons projecting from one inferior colliculus to the other, with the dorsal cortex and central nucleus providing the most extensive connections. In addition, many ascending and descending auditory centers send projections to the IC via the CoIC, together with diverse sources located outside the classically defined auditory pathway. The degree of interconnection between the two ICs suggests they function as a single entity. Recent in vivo evidence has established that CoIC projections modulate the neural representation of sound frequency, level, and location in the IC, thus indicating an important role for the CoIC in auditory processing. However, there is limited evidence for the influence of the CoIC on auditory behavior. This, together with the diversity of sources projecting via the CoIC, suggest unknown roles that warrant further exploration.

Effects of nonlinear interactions of flexural modes on the performance of a beam autoparametric vibration absorber

2019 ◽  
Vol 26 (7-8) ◽  
pp. 459-474
Author(s):  
Saeed Mahmoudkhani ◽  
Hodjat Soleymani Meymand
Keyword(s):  
Frequency Response ◽  
Internal Resonance ◽  
Continuation Method ◽  
Harmonic Balance Method ◽  
Vibration Absorber ◽  
Primary System ◽  
Lumped Mass ◽  
Response Curves ◽  
Internal Resonances ◽  
The One

The performance of the cantilever beam autoparametric vibration absorber with a lumped mass attached at an arbitrary point on the beam span is investigated. The absorber would have a distinct feature that in addition to the two-to-one internal resonance, the one-to-three and one-to-five internal resonances would also occur between flexural modes of the beam by tuning the mass and position of the lumped mass. Special attention is paid on studying the effect of these resonances on increasing the effectiveness and extending the range of excitation amplitudes at which the autoparametric vibration absorber remains effective. The problem is formulated based on the third-order nonlinear Euler–Bernoulli beam theory, where the assumed-mode method is used for deriving the discretized equations of motion. The numerical continuation method is then applied to obtain the frequency response curves and detect the bifurcation points. The harmonic balance method is also employed for detecting the type of internal resonances between flexural modes by inspecting the frequency response curves corresponding to different harmonics of the response. Parametric studies on the performance of the absorber are conducted by varying the position and mass of the lumped mass, while the frequency ratio of the primary system to the first mode of the beam is kept equal to two. Results indicated that the one-to-five internal resonance is especially responsible for the considerable enhancement of the performance.

Single-Unit Responses in the Inferior Colliculus of Decerebrate Cats II. Sensitivity to Interaural Level Differences

1999 ◽  
Vol 82 (1) ◽  
pp. 164-175 ◽  
Author(s):  
Kevin A. Davis ◽  
Ramnarayan Ramachandran ◽  
Bradford J. May
Keyword(s):  
Frequency Response ◽  
Inferior Colliculus ◽  
Free Field ◽  
Central Nucleus ◽  
Type I ◽  
Discharge Rates ◽  
Ipsilateral Stimulation ◽  
Interaural Level Differences ◽  
Type V ◽  
Decerebrate Cats

Single units in the central nucleus of the inferior colliculus (ICC) of unanesthetized decerebrate cats can be grouped into three distinct types (V, I, and O) according to the patterns of excitation and inhibition revealed in contralateral frequency response maps. This study extends the description of these response types by assessing their ipsilateral and binaural response map properties. Here the nature of ipsilateral inputs is evaluated directly using frequency response maps and compared with results obtained from methods that rely on sensitivity to interaural level differences (ILDs). In general, there is a one-to-one correspondence between observed ipsilateral input characteristics and those inferred from ILD manipulations. Type V units receive ipsilateral excitation and show binaural facilitation (EE properties); type I and type O units receive ipsilateral inhibition and show binaural excitatory/inhibitory (EI) interactions. Analyses of binaural frequency response maps show that these ILD effects extend over the entire receptive field of ICC units. Thus the range of frequencies that elicits excitation from type V units is expanded with increasing levels of ipsilateral stimulation, whereas the excitatory bandwidth of type I and O units decreases under the same binaural conditions. For the majority of ICC units, application of bicuculline, an antagonist for GABAA-mediated inhibition, does not alter the basic effects of binaural stimulation; rather, it primarily increases spontaneous and maximum discharge rates. These results support our previous interpretations of the putative dominant inputs to ICC response types and have important implications for midbrain processing of competing free-field sounds that reach the listener with different directional signatures.

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