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Hearing Research Dec 2015Type I and type II cochlear afferents differ markedly in number, morphology and innervation pattern. The predominant type I afferents transmit the elemental features of...
Type I and type II cochlear afferents differ markedly in number, morphology and innervation pattern. The predominant type I afferents transmit the elemental features of acoustic information to the central nervous system. Excitation of these large diameter myelinated neurons occurs at a single ribbon synapse of a single inner hair cell. This solitary transmission point depends on efficient vesicular release that can produce large, rapid, suprathreshold excitatory postsynaptic potentials. In contrast, the many fewer, thinner, unmyelinated type II afferents cross the tunnel of Corti, turning basally for hundreds of microns to form contacts with ten or more outer hair cells. Although each type II afferent is postsynaptic to many outer hair cells, transmission from each occurs by the infrequent release of single vesicles, producing receptor potentials of only a few millivolts. Analysis of membrane properties and the site of spike initiation suggest that the type II afferent could be activated only if all its presynaptic outer hair cells were maximally stimulated. Thus, the details of synaptic transfer inform the functional distinctions between type I and type II afferents. High efficiency transmission across the inner hair cell's ribbon synapse supports detailed analyses of the acoustic world. The much sparser transfer from outer hair cells to type II afferents implies that these could respond only to the loudest, sustained sounds, consistent with previous reports from in vivo recordings. However, type II afferents could be excited additionally by ATP released during acoustic stress of cochlear tissues.
Topics: Acoustic Stimulation; Adenosine Triphosphate; Animals; Cochlea; Excitatory Postsynaptic Potentials; Hair Cells, Auditory; Hair Cells, Auditory, Outer; Hearing; Humans; Mice; Neurons, Afferent; Rats; Synapses; Synaptic Transmission
PubMed: 26403507
DOI: 10.1016/j.heares.2015.09.007 -
Current Opinion in Chemical Biology Aug 2015Neurons tightly regulate the electrical potential difference across the plasma membrane with millivolt accuracy and millisecond resolution. Membrane voltage dynamics... (Review)
Review
Neurons tightly regulate the electrical potential difference across the plasma membrane with millivolt accuracy and millisecond resolution. Membrane voltage dynamics underlie the generation of an impulse, the transduction of impulses from one end of the neuron to the other, and the release of neurotransmitters. Imaging these voltage dynamics in multiple neurons simultaneously is therefore crucial for understanding how neurons function together within circuits in intact brains. Genetically encoded fluorescent voltage sensors have long been desired to report voltage in defined subsets of neurons with optical readout. In this review, we discuss the diverse strategies used to design and optimize protein-based voltage sensors, and highlight the chemical mechanisms by which different classes of reporters sense voltage. To guide neuroscientists in choosing an appropriate sensor for their applications, we also describe operating trade-offs of each class of voltage indicators.
Topics: Action Potentials; Animals; Biosensing Techniques; Cell Membrane; Fluorescent Dyes; Humans; Luminescent Proteins; Neurons; Protein Binding; Voltage-Sensitive Dye Imaging
PubMed: 26079047
DOI: 10.1016/j.cbpa.2015.05.003 -
Sensors (Basel, Switzerland) Nov 2014We have measured the coefficient of the voltage induced frequency shift (VIFS) of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong...
We have measured the coefficient of the voltage induced frequency shift (VIFS) of a 32.768 KHz quartz tuning fork. Three vibration modes were studied: one prong oscillating, two prongs oscillating in the same direction, and two prongs oscillating in opposite directions. They all showed a parabolic dependence of the eigen-frequency shift on the bias voltage applied across the fork, due to the voltage-induced internal stress, which varies as the fork oscillates. The average coefficient of the VIFS effect is as low as several hundred nano-Hz per millivolt, implying that fast-response voltage-controlled oscillators and phase-locked loops with nano-Hz resolution can be built.
PubMed: 25414971
DOI: 10.3390/s141121941 -
Frontiers in Neuroengineering 2014In this report, we describe the system integration of a complementary metal oxide semiconductor (CMOS) integrated circuit (IC) chip, capable of both stimulation and...
In this report, we describe the system integration of a complementary metal oxide semiconductor (CMOS) integrated circuit (IC) chip, capable of both stimulation and recording of neurons or neural tissues, to investigate electrical signal propagation within cellular networks in vitro. The overall system consisted of three major subunits: a 5.0 × 5.0 mm CMOS IC chip, a reconfigurable logic device (field-programmable gate array, FPGA), and a PC. To test the system, microelectrode arrays (MEAs) were used to extracellularly measure the activity of cultured rat cortical neurons and mouse cortical slices. The MEA had 64 bidirectional (stimulation and recording) electrodes. In addition, the CMOS IC chip was equipped with dedicated analog filters, amplification stages, and a stimulation buffer. Signals from the electrodes were sampled at 15.6 kHz with 16-bit resolution. The measured input-referred circuitry noise was 10.1 μ V root mean square (10 Hz to 100 kHz), which allowed reliable detection of neural signals ranging from several millivolts down to approximately 33 μ Vpp. Experiments were performed involving the stimulation of neurons with several spatiotemporal patterns and the recording of the triggered activity. An advantage over current MEAs, as demonstrated by our experiments, includes the ability to stimulate (voltage stimulation, 5-bit resolution) spatiotemporal patterns in arbitrary subsets of electrodes. Furthermore, the fast stimulation reset mechanism allowed us to record neuronal signals from a stimulating electrode around 3 ms after stimulation. We demonstrate that the system can be directly applied to, for example, auditory neural prostheses in conjunction with an acoustic sensor and a sound processing system.
PubMed: 25346683
DOI: 10.3389/fneng.2014.00039 -
The Journal of Neuroscience : the... Aug 2014Local field potentials are important indicators of in vivo neural activity. Sustained, phase-locked, sound-evoked extracellular fields in the mammalian auditory...
Local field potentials are important indicators of in vivo neural activity. Sustained, phase-locked, sound-evoked extracellular fields in the mammalian auditory brainstem, known as the auditory neurophonic, reflect the activity of neurons in the medial superior olive (MSO). We develop a biophysically based model of the neurophonic that accounts for features of in vivo extracellular recordings in the cat auditory brainstem. By making plausible idealizations regarding the spatial symmetry of MSO neurons and the temporal synchrony of their afferent inputs, we reduce the challenging problem of computing extracellular potentials in a 3D volume conductor to a one-dimensional problem. We find that postsynaptic currents in bipolar MSO neuron models generate extracellular voltage responses that strikingly resemble in vivo recordings. Simulations reproduce distinctive spatiotemporal features of the in vivo neurophonic response to monaural pure tones: large oscillations (hundreds of microvolts to millivolts), broad spatial reach (millimeter scale), and a dipole-like spatial profile. We also explain how somatic inhibition and the relative timing of bilateral excitation may shape the spatial profile of the neurophonic. We observe in simulations, and find supporting evidence in in vivo data, that coincident excitatory inputs on both dendrites lead to a drastically reduced spatial reach of the neurophonic. This outcome surprises because coincident inputs are thought to evoke maximal firing rates in MSO neurons, and it reconciles previously puzzling evoked potential results in humans and animals. The success of our model, which has no axon or spike-generating sodium currents, suggests that MSO spikes do not contribute appreciably to the neurophonic.
Topics: Animals; Auditory Pathways; Cats; Evoked Potentials, Auditory, Brain Stem; Female; Male; Models, Neurological; Neurons; Olivary Nucleus
PubMed: 25164666
DOI: 10.1523/JNEUROSCI.0175-14.2014 -
Scientific Reports Aug 2014Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical...
Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect infrasound at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for infrasound frequencies.
PubMed: 25130708
DOI: 10.1038/srep06105 -
Nature Communications Jun 2014Photon and neutron inelastic scattering spectrometers are microscopes for imaging condensed matter dynamics on very small length and time scales. Inelastic X-ray...
Photon and neutron inelastic scattering spectrometers are microscopes for imaging condensed matter dynamics on very small length and time scales. Inelastic X-ray scattering permitted the first quantitative studies of picosecond nanoscale dynamics in disordered systems almost 20 years ago. However, the nature of the liquid-glass transition still remains one of the great unsolved problems in condensed matter physics. It calls for studies at hitherto inaccessible time and length scales, and therefore for substantial improvements in the spectral and momentum resolution of the inelastic X-ray scattering spectrometers along with a major enhancement in spectral contrast. Here we report a conceptually new spectrometer featuring a spectral resolution function with steep, almost Gaussian tails, sub-meV (≃620 μeV) bandwidth and improved momentum resolution. The spectrometer opens up uncharted space on the dynamics landscape. New results are presented on the dynamics of liquid glycerol, in the regime that has become accessible with the novel spectrometer.
PubMed: 24953338
DOI: 10.1038/ncomms5219 -
The Journal of Spinal Cord Medicine Jul 2014Experimental study.
STUDY DESIGN
Experimental study.
OBJECTIVE
To determine similarities and differences of C7 and T11-12 multisegmental motor responses (MMR) studies for the upper limbs (UL) and lower limbs (LL).
SETTINGS
Neuroscience Lab, TWU (School of Physical Therapy, TX, USA).
METHODS
C7 and T11-12 percutaneous electrical stimulations were applied while recording muscle action potentials from ULs and LLs.
RESULTS
The procedure of cervical MMR (CMMR) was easier in application than thoracolumbar MMR (TMMR), requiring less current intensities but cause more "jolts" in the trapezius/shoulder complex, due to close proximity of the stimulation electrodes. CMMR evoked large amplitude motor responses in the millivolts range in (UL) muscles, but smaller amplitude signal in (LL) muscles (in microvolts). TMMR evoked large amplitude motor responses in both UL and LL (in millivolts). The MMR amplitude was generally larger in the UL as compared to the LL, in the distal limb muscles more than in the proximal limb muscles. CMMR and TMMR for the UL were comparable in amplitude, latencies and action potential shapes. Signal latencies were longer for distal limb muscles as compared to proximal limb muscles and were slightly longer for LL as compared to UL muscles. MMR signals were either biphasic or triphasic in shape.
CONCLUSION
CMMR and TMMR have similarities and differences in the methods and recording signal that must be considered during its clinical applications. Comparing the signal of the UL muscles with CMMR and TMMR could be a useful test for the integrity of the ascending and descending spinal pathways in patients with spinal cord injuries and diseases.
Topics: Adolescent; Adult; Aged; Biophysics; Electric Stimulation; Electromyography; Evoked Potentials, Motor; Female; Functional Laterality; Humans; Lower Extremity; Lumbosacral Region; Male; Middle Aged; Multivariate Analysis; Muscle, Skeletal; Reaction Time; Sacrococcygeal Region; Spinal Cord; Thoracic Vertebrae; Upper Extremity; Young Adult
PubMed: 24621020
DOI: 10.1179/2045772313Y.0000000157 -
Case Reports in Neurological Medicine 2013In advanced Parkinson's disease (PD), deep brain stimulation (DBS) may be an alternative option for the treatment of motor symptoms. Side effects associated with...
In advanced Parkinson's disease (PD), deep brain stimulation (DBS) may be an alternative option for the treatment of motor symptoms. Side effects associated with subthalamic nucleus (STN) DBS in patients with PD are emerging as the most frequent sensory and motor symptoms. DBS-related syncope is reported as extremely rare. We wanted to discuss the mechanisms of syncope associated with STN DBS in a patient with Parkinson's disease. Case report. Sixty-three-year-old female patient is followed up with diagnosis of idiopathic Parkinson's disease for 6 years in our clinic. The patient has undergone STN DBS due to painful dystonia and drug resistant tremor. During the operation, when the left STN was stimulated at 5 milliampere (mAmp), the patient developed presyncopal symptoms. However, when the stimulation was stopped symptoms improved. During the early period after the operation, when the right STN was stimulated at 1.3 millivolts (mV), she developed the pre-yncopal symptoms and then syncope. Our case shows that STN DBS may lead to directly autonomic symptoms resulting in syncope during stimulation-on (stim-on).
PubMed: 24455344
DOI: 10.1155/2013/371929 -
The AAPS Journal Mar 2014This study was designed to test the hypothesis that a triggered release of a topical microbicide (tenofovir) from hyaluronic acid nanoparticles (HA-NPs) can be achieved...
This study was designed to test the hypothesis that a triggered release of a topical microbicide (tenofovir) from hyaluronic acid nanoparticles (HA-NPs) can be achieved under the influence of hyaluronidase (HAase) enzyme. A fractional factorial experimental design was used to examine the factors [molar concentrations of adipic acid dihydrazide (X1) and 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (X2), volume of acetone (X3) and reaction time (X4)] influencing the responses, Y1; particle mean diameter: PMD (nanometers: nm), Y2; polydispersity index: PDI and Y3; zeta (ζ) potential: (millivolts). The amide bond formation between HA and ADH after cross-linking was confirmed by FT-IR and (13)C-NMR analyses. These NPs were also characterized for cytotoxicity on a human vaginal epithelial cell line and L. crispatus. When formulated with factors X1; 2.49 mM, X2; 9.96 mM, X3; 60 mL, X4; 6 h, HA-NPs exhibited a spherical shape with PMD, PDI, ζ potential, encapsulation efficiency, and drug loading of 70.6 ± 4.1 nm, 0.07 ± 0.02, -38.2 ± 2.8 mV, 51.8 ± 2.4% w/w and 26.1 ± 1.2% w/w, respectively, (n = 3). Unlike for HA based gel, HAase significantly triggered the drug release and HA degradation from the NPs after 24 h (~90% w/w and 65% w/w, respectively); whereas, in its absence, these values were ~39% w/w and 26% w/w, respectively. The NPs were non-cytotoxic to human vaginal VK2/E6E7, End1/E6E7 cells and Lactobacillus crispatus. These data highlight the potential of HAase-sensitive HA-NPs templates for the controlled and vaginal delivery of anti-HIV/AIDS microbicides.
Topics: Anti-HIV Agents; Cell Line; Female; Humans; Hyaluronoglucosaminidase; In Vitro Techniques; Magnetic Resonance Spectroscopy; Nanoparticles; Spectroscopy, Fourier Transform Infrared; Surface Properties; Vagina
PubMed: 24343770
DOI: 10.1208/s12248-013-9546-7