bluuebunny/crossref_metadata_2025 huggingface dataset:
Force-sensitive mechanoreceptors of the dactyl of the crab: single-unit responses during walking and evaluation of function
Authors: Libersat F. , Clarac F. , Zill S.
Published: December 2017

The activities of individual force-sensitive mechanoreceptors of the dactyl (terminal leg segment) of the crab, Carcinus maenas, have been recorded during free walking. These receptors have also been mechanically and electrically stimulated in freely moving animals to directly evaluate their function in locomotion. All force-sensitive mechanoreceptors fired during the stance phase of walking and were silent during swing. Receptor discharges showed regular phase relationships to bursts in motor neurons of leg muscles. Crabs walk laterally and use the legs of one side either in trailing to actively push the animal to the opposite side, or in leading, to less forcefully pull the animal in that direction. Individual force-sensitive mechanoreceptors differed in their patterns of activity during trailing or leading according to their location on the dactyl. Units of proximal receptors fired more vigorously when used in trailing than in leading. Discharges in trailing were also increased by loading of the animal. In contrast, distal receptors near the dactyl tip fired equally intensely during walking in either direction. Proximal receptors thus encode forces and loads applied to the leg. Distal receptors do not encode loads but can signal leg contact and, potentially, exteroceptive vibrations. Sensory stimulation of force-sensitive mechanoreceptors was produced during walking by a device that imposed continuous mechanical bending of the dactyl and by electrical stimulation of dactyl nerves. Intra- and inter-segmental reflexes were evaluated by myographic recordings from leg muscles. Continuous mechanical deformation of the dactyl increased the activity of the levator and decreased firing in the depressor muscles of the homonymous leg during walking. The same stimulus produced enhanced activity in depressor muscles of adjacent legs. The latter effect was not due to simple mechanical coupling resulting from reflexes in the stimulated leg. These reflexes can function to limit forces applied to a leg and provide compensatory adjustments in other legs. Brief low-threshold electrical stimuli applied to nerves in which the activities of force-sensitive mechanoreceptors were recorded produced reflex effects similar to those obtained by mechanical stimulation. These stimuli also reset the rhythm of motor neuron bursting in both homonymous and adjacent legs during walking. These studies confirm the importance of force-sensitive mechanoreceptors in adapting walking patterns and in determining leg coordination in locomotion.
Objective classification of motion- and direction-sensitive neurons in primary somatosensory cortex of awake monkeys
Authors: Warren S. , Hamalainen H. A. , Gardner E. P.
Published: December 2017

S. Warren, H. A. Hamalainen, and E. P. Gardner, “Objective classification of motion- and direction-sensitive neurons in primary somatosensory cortex of awake monkeys.” It was incorrectly stated that Orban and co-workers(J. Neurophysiol. 45: 1059–1073, 1981) attributed direction selectivity to cortical neurons having a direction index (DI) ge 20. Orban et al. actually used a weighted average of DIs and defined cells with a mean DI (MDI) above 50 as direction selective. Their criterion for direction selectivity was stricter and not less stringent, as stated in the paper. This error does not alter any of the data or conclusions of Warren et al.
Maximal force as a function of anatomical features of motor units in the cat tibialis anterior
Authors: Bodine S. C. , Roy R. R. , Eldred E. , Edgerton V. R.
Published: December 2017

In 11 tibialis anterior muscles of the cat, a single motor unit was characterized physiologically and subsequently depleted of its glycogen through repetitive stimulation of an isolated ventral root filament. Muscle cross sections were stained for glycogen using a periodic acid-Schiff reaction, and single-fiber optical densities were determined to identify those fibers belonging to the stimulated motor unit. Innervation ratios were determined by counting the total number of muscle fibers in a motor unit in sections taken through several levels of the muscle. The average innervation ratios for the fast, fatigueable (FF) and fast, fatigue-resistant (FR) units were similar. However, the slow units (S) contained 61% fewer fibers than the fast units (FF and FR). Muscle fibers belonging to S and FR units were similar in cross-sectional area, whereas fibers belonging to FF units were significantly larger than fibers belonging to either S or FR units. Additionally, muscle fibers innervated by a single motoneuron varied by two- to eightfold in cross-sectional area. Specific tensions, based on total cross-sectional area determined by summing the areas of all muscle fibers of each unit, showed a modest difference between fast and slow units, the means being 23.5 and 17.2 N X cm-2, respectively. Variations in maximum tension among units could be explained principally by innervation ratio, although fiber cross-sectional area and specific tension did contribute to differences between unit types.
Mechanoreceptor response to mechanical and thermal stimuli in the glans penis of the dog
Authors: Johnson R. D. , Kitchell R. L.
Published: December 2017

In the dog, we isolated 126 mechanoreceptive afferent fibers of the A-delta myelinated fiber class from the dorsal nerve of the penis using microdissection and extracellular electrophysiological techniques. Receptive fields on the glans penis were stimulated with a computer-controlled mechanostimulator and Peltier effect thermostimulator. The great majority of units were categorized as either rapidly adapting (RA) or slowly adapting (SA) and were located primarily proximally and distally, respectively, on the glans. In comparison to values from other glabrous skin regions in other species, mean displacement and force thresholds of penile mechanoreceptors were high, whereas the mean velocity thresholds were low. SA units, generally poor encoders of static displacement, were distinguishable into two types based on static response firing pattern but were not homologous to either the SA I or SA II mechanoreceptors found in other skin regions. Fifty-five units were given simultaneous mechanical and thermal stimulation. Very few units responded to pure thermal stimulation or increased their discharge frequency to skin cooling. Warm receptive-field temperatures between 35 and 43 degrees C increased mechanical sensitivity, measured by displacement and velocity coding functions, in almost all units tested. We conclude that canine penile mechanoreceptors, capable of encoding a variety of skin movements when the penis is warm, provide the spinal cord with the sensory input necessary to drive the spinal sexual reflexes. However, many appear to be at least physiologically different from mechanoreceptors native to other skin areas.
Modifications in membrane properties of trigeminal sensory neurons during general anesthesia
Authors: Puil E. , Gimbarzevsky B.
Published: December 2017

1. The effects of general anesthesia on passive and active membrane properties of trigeminal root ganglion neurons of decerebrate guinea pigs have been determined using frequency-domain analyses of small-amplitude perturbations of membrane voltage. Quantification of the effects was accomplished by fitting the complex impedance locus diagrams computed from the neuronal responses with a membrane model based on linearized Hodgkin-Huxley-like equations. 2. Endotracheal administrations of isoflurane (2-3% for periods of 30-180 s), the most extensively studied of five general anesthetics, did not elicit large changes in membrane potential or in electrical properties in 26 of the 38 neurons. In this relatively unresponsive group, application of isoflurane in higher concentrations (3-4%) tended to evoke small but significant changes (less than 20%) in membrane properties without altering membrane potential by greater than 5 mV. These changes consisted of increases in the effective input capacitance and input conductance. 3. The impedance magnitude functions were reduced in amplitude consistently in 12 of the 38 neurons during induction of general anesthesia with isoflurane (2-4%) or, in several cases, with halothane (2%). Such applications evoked depolarizations of 8-32 mV, which also were observed in several instances of anesthesia with enflurane and cyclopropane. Quantification of these effects on electrical properties by curve fitting with the linearized Hodgkin-Huxley model revealed increases in the effective input capacitance, in the time-invariant resting conductance, Gr, and in the voltage- and time-dependent conductance, GL. Sometimes, an initial decrease preceded the increase of Gr, and the relaxation time constant associated with GL usually was reduced by the anesthetic agent in the 12 neurons. 4. In 10 neurons, membrane resonance behavior (which was apparent as a large hump at low frequencies of the impedance magnitude functions) was reduced in amplitude, as well as broadened in bandwidth, when peak changes in membrane properties were evident, i.e., during surgical or deep anesthesia. These actions of isoflurane or halothane were correlated to a reduction in spike electrogenesis and they may account for the reduced tendency of neurons to fire repetitive action potentials during anesthesia with isoflurane or halothane.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of interaural time delays of noise stimuli on low-frequency cells in the cat's inferior colliculus. III. Evidence for cross-correlation
Authors: Yin T. C. , Chan J. C. , Carney L. H.
Published: December 2017

1. We tested the coincidence, or cross-correlation, model of Jeffress, which proposes a neuronal mechanism for sensitivity to interaural time differences (ITDs) in low-frequency cells in the central nucleus of the inferior colliculus (ICC) of the cat. Different tokens of Gaussian noise stimuli were delivered to the two ears. We studied the neural responses to changes in ITDs of these stimuli and examined the manner in which the binaural cells responded to them. All of our results support the idea that the central binaural neurons perform an operation very similar to cross-correlation on the inputs arriving from each side. These inputs are transformed from the actual acoustic signal by the peripheral auditory system, and these transformations are reflected in the properties of the cross-correlations. 2. The responses to ITDs of identical broadband noise stimuli to the two ears varies cyclically as a function of ITD at a frequency close to the best frequency of the neuron. This cyclic response is a consequence of the narrowband filtering of the wideband acoustic signal by the auditory nerve fibers. To examine the effects of using stimuli to the two ears that were correlated to each other to different degrees, we generated pairs of noises. Each pair consisted of one standard noise, which was delivered to one ear, and a linear sum of two standard uncorrelated noises, which was delivered to the other ear. The responses of 34 neurons in the ICC to ITDs of noises with variable interaural coherence were examined. When partially correlated noises were delivered, there was a positive and approximately linear relationship between the degree of modulation of the response as a function of ITD and interaural coherence. The degree of modulation was measured by the synchronization coefficient, or vector strength, over one period of the ITD curve. 3. We examined the effects of altering the interaural phase relationships of the input noise stimuli. The phase of the noise stimuli was changed by digitally filtering the standard noise so that only a phase delay was imposed. The responses to ITDs with differing interaural phase relationships were then studied by delivering a phase-shifted noise to one ear and the standard noise to the other. The ITD curves in response to phase-shifted noise were shifted by about the same amount as the shift of the stimulus; the shift of the response was measured with respect to the case with identical noises to the two ears.(ABSTRACT TRUNCATED AT 400 WORDS)
Inputs from regularly and irregularly discharging vestibular nerve afferents to secondary neurons in the vestibular nuclei of the squirrel monkey. II. Correlation with output pathways of secondary neurons
Authors: Highstein S. M. , Goldberg J. M. , Moschovakis A. K. , Fernandez C.
Published: December 2017

1. Intracellular recordings were made from secondary neurons in the vestibular nuclei of barbiturate-anesthetized squirrel monkeys. Monosynaptic excitatory postsynaptic potentials (EPSPs) evoked by stimulation of the ipsilateral vestibular nerve (Vi) were measured. An electrophysiological paradigm, described in the preceding paper (26), was used to determine the proportion of irregularly (I) and regularly (R) discharging Vi afferents making direct connections with individual secondary neurons. The results were expressed as a % I index, an estimate for each neuron of the percentage of the total Vi monosynaptic input that was derived from I afferents. The secondary neurons were also classified as I, R, or M cells, depending on whether they received their direct Vi inputs predominantly from I or R afferents or else from a mixture (M) of both kinds of Vi fibers. The neurons were located in the superior vestibular nucleus (SVN) or in the rostral parts of the medical or lateral (LVN) vestibular nuclei. 2. Antidromic activation or reconstruction of axonal trajectories after intrasomatic injection of horseradish peroxidase (HRP) was used to identify three classes of secondary neurons in terms of their output pathways: 1) cerebellar-projecting (Fl) cells innervating the flocculus (n = 26); 2) rostrally projecting (Oc) cells whose axons ascended toward the oculomotor (IIIrd) nucleus (n = 27); and 3) caudally projecting (Sp) cells with axons descending toward the spinal cord (n = 13). Two additional neurons, out of 21 tested, could be antidromically activated both from the level of the IIIrd nucleus and from the spinal cord. 3. The Vi inputs to the various classes of relay neurons differed. As a class, Oc neurons received the most regular inputs. Sp neurons had more irregular inputs. Fl neurons were heterogeneous with similar numbers of R, M, and I neurons. The mean values (+/- SD) of the % I index for the Oc, Fl, and Sp neurons were 34.7 +/- 24.7, 51.9 +/- 30.4, and 61.8 +/- 18.0%, respectively. Only the Oc neurons had a % I index that was similar to the proportion of I afferents (34%) in the vestibular nerve (cf. Ref. 26). 4. The commissural inputs from the contralateral vestibular nerve (Vc) also differed for the three projection classes. Commissural inhibition was most common in Fl cells: 22/25 (88%) of the neurons had Vc inhibitory postsynaptic potentials (IPSPs) and 1/25 (4%) had a Vc EPSP. In contrast, Vc inputs were only observed in approximately half the Oc and Sp neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of cholinergic depletion on neuron activities in the cat visual cortex
Authors: Sato H. , Hata Y. , Hagihara K. , Tsumoto T.
Published: December 2017

1. Unilateral lesions of the nucleus basalis magnocellularis (nBM), a source of cholinergic projection to the cerebral cortex, were produced by injection of kainic acid in the cat. The lesions caused a significant reduction in density of choline acetyltransferase-immunoreactive terminals in the visual cortex ipsilateral to the lesions. 2. In the primary visual cortex ipsilateral to the lesions [acetylcholine (ACh)-depleted cortex], about half of the cells had weak or undetectable visual responses, whereas in the contralateral visual cortex almost all the cells had normal responsivity. The response selectivity, such as orientation and direction selectivities, of cortical cells was not affected by the depletion of ACh. 3. The microionophoretic application of ACh to cells under observation facilitated visual responses in 83% of the cells recorded from the ACh-depleted cortex, whereas it suppressed the responses in only 9%. The application of a muscarinic antagonist, atropine, to cells in the ACh-depleted cortex was ineffective, suggesting no residual ACh activity. 4. The mean current required to induce facilitation in the cortex ipsilateral to the lesion was significantly smaller than that required in the contralateral cortex and the visual cortex of the normal cat, suggesting a supersensitivity of receptors mediating the effect or a reduction in catabolism of exogenous ACh in the ACh-depleted cortex. 5. More than half of the cells that had been unresponsive to visual stimuli became clearly responsive during the ACh application. The response magnitude of cortical cells, as a whole, increased to the same degree as that observed during the ACh application in the normal cat. 6. In addition to the decrease in the average response magnitude, there was a remarkable variability in responses of cells to motion of the slit from sweep to sweep in the ACh-depleted cortex. The application of ACh to cortical cells decreased the variability of responses and consequently made the responses much more consistent. 7. These results suggest that without ACh supplied from the nBM, most of the cortical neurons could not respond briskly and consistently to excitatory inputs and that exogenously applied ACh could reverse such an impairment of cortical neurons through intact or even supersensitive postsynaptic receptors.
Responses of feline medial medullary reticulospinal neurons to cardiac input
Authors: Blair R. W.
Published: December 2017

1. Responses of medial medullary reticulospinal (RS) neurons to electrical stimulation of cardiac sympathetic afferents, probing the epicardium and epicardial application of bradykinin, were determined in cats anesthetized with alpha-chloralose. Conduction velocity of RS cells averaged 67 m/s; these neurons were probably part of the RS motor pathway and the bulbospinal pathway that modulates ascending information. Fifty-three RS neurons had unilateral projections and 18 neurons bilateral projections to the thoracic spinal cord. 2. Maximal electrical stimulation of the left stellate ganglion excited 69% of 97 RS neurons with a mean latency of 15 +/- 1.0 ms. Mean spike discharge rate increased from 4 +/- 1.2 to 93 +/- 8.0 spikes/s for responsive neurons. 3. Epicardial bradykinin (0.04 mg) excited 34%, inhibited 2%, and did not affect 64% of 44 RS cells tested. Excited neurons increased their mean discharge rate from 12.3 +/- 3.6 to 18.2 +/- 4.3 spikes/s, with a latency of 24 +/- 3.0 s, in response to bradykinin. Response duration averaged 43 +/- 2.3 s. Neurons responsive to bradykinin had greater spontaneous discharge rates than unresponsive neurons. Thirteen of 16 RS cells excited by bradykinin were located in the gigantocellular tegmental field (FTG); the other three cells were in the paramedian nucleus (PR). 4. Epicardial bradykinin often elicited changes in aortic pressure. Although some neurons responded to altered blood pressure alone, these responses could not account for responses to bradykinin. Furthermore, the percentage of responsive neurons was similar in experiments with intact nerves as well as those with vagotomy and barodenervation. 5. Touching the epicardium with a blunt probe excited 19 of 60 (32%) RS neurons, and visceral receptive fields were mapped for 12 of these cells. Neurons responded with one to three spikes to probing. RS neurons responsive to probing were scattered throughout the medial reticular formation. 6. RS cells were also tested for somatic, auditory, and visual input. Of 63 neurons responsive to sympathetic afferent stimulation, only one did not receive convergent input from at least one of these sources; 51% received input from each tested source. Neurons responsive to bradykinin were more likely to receive visual input than the general population of neurons. RS neurons unresponsive to sympathetic afferent stimulation were less likely to receive convergent inputs from other sensory modalities.(ABSTRACT TRUNCATED AT 400 WORDS)
The two-dimensional spatial structure of simple receptive fields in cat striate cortex
Authors: Jones J. P. , Palmer L. A.
Published: December 2017

1. A reverse correlation (6, 8, 25, 35) method is developed that allows quantitative determination of visual receptive-field structure in two spatial dimensions. This method is applied to simple cells in the cat striate cortex. 2. It is demonstrated that the reverse correlation method yields results with several desirable properties, including convergence and reproducibility independent of modest changes in stimulus parameters. 3. In contrast to results obtained with moving stimuli, we find that the bright and dark excitatory subregions in simple receptive fields do not overlap to any great extent. This difference in results may be attributed to confounding the independent variables space and time when using moving stimuli. 4. All simple receptive fields have subregions that vary smoothly in all directions in space. There are no sharp transitions either between excitatory subregions or between subregions and the area surrounding the receptive field. 5. Simple receptive fields vary both in the number of subregions observed, in the elongation of each subregion, and in the overall elongation of the field. In contrast with results obtained using moving stimuli, we find that subregions within a given receptive field need not be the same length. 6. The hypothesis that simple receptive fields can be modeled as either even symmetric or odd symmetric about a central axis is evaluated. This hypothesis is found to be false in general. Most simple receptive fields are neither even symmetric nor odd symmetric. 7. The hypothesis that simple receptive fields can be modeled as the product of a width response profile and an orthogonal length response profile (Cartesian separability) is evaluated. This hypothesis is found to be true for only approximately 50% of the cells in our sample.
Patch-clamp study of the calcium-dependent chloride current in AtT-20 pituitary cells
Authors: Korn S. J. , Weight F. F.
Published: December 2017

1. Voltage-clamp recordings were made from cultured AtT-20 pituitary cells using the whole-cell patch-clamp technique. Cells were perfused internally with Cs+ to block K+ currents and bathed externally with either 1 microM tetrodotoxin or with tetraethylammonium (TEA) as a Na+ substitute to block voltage-activated Na+ currents. 2. Depolarizing voltage steps from a holding potential of -80 mV to potentials positive to -30 mV evoked two currents: a fast inward current that activated between -30 and +70 mV and a slowly activating current (designated “slow step current”) that was inward between -30 and near 0 mV (the Cl- equilibrium potential) and outward positive to about 0 mV. Repolarization to -80 mV revealed a slowly decaying, inward tail current, whose magnitude with respect to step potential closely matched the current-voltage relationship of the voltage-activated Ca2+ current. 3. Activation of the fast inward current, slow step current, and tail current, was prevented by extracellular application of Cd2+ or removal of extracellular Ca2+. Replacement of extracellular Ca2+ with Ba2+ potentiated the fast inward current but blocked the slow step and tail currents. Intracellular perfusion with greater than 1 mM of the Ca2+ chelators ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) or [1,2-bis(2)aminophenoxy]ethane N,N,N',N'-tetraacetic acid (BAPTA) prevented activation of the slow step and tail currents, but not the fast inward current. 4. The reversal potential of the slow inward current was sensitive to changes in the Cl- equilibrium potential but not to substitution of TEA for Na+. The slow step current, but not the fast inward current, was partially blocked by the Cl- channel blocker, 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid. 5. These data indicate that both the slow inward tail current and the slowly activating, reversible step current were a Ca2+-dependent Cl- current, similar to that described in other neuronal and nonneuronal cell types. The fast inward current was a voltage-activated Ca2+ current, described previously in these and other cells. 6. In the absence of intracellular EGTA, the tail current decayed with complex kinetics, its time course apparently dependent on the magnitude of the voltage-activated Ca2+ current. In the presence of 200 microM intracellular EGTA, the tail current decayed significantly faster and often decayed exponentially.
Primary involvement of K+ conductance in membrane resonance of trigeminal root ganglion neurons
Authors: Puil E. , Gimbarzevsky B. , Spigelman I.
Published: December 2017

1. The complex impedances and impedance magnitude functions were obtained from neurons in in vitro slices of trigeminal root ganglia using frequency-domain analyses of intracellularly recorded voltage responses to specified oscillatory input currents. A neuronal model derived from linearized Hodgkin-Huxley-like equations was used to fit the complex impedance data. This procedure yielded estimates for membrane electrical properties. 2. Membrane resonance was observed in the impedance magnitude functions of all investigated neurons at their initial resting membrane potentials and was similar to that reported previously for trigeminal root ganglion neurons in vivo. Tetrodotoxin (10(-6) M), a Na+-channel blocker, applied in the bathing medium for 20 min produced only minor changes, if any, in the resonance, although gross impairment of Na+-spike electrogenesis was apparent in most of the neurons. Brief applications (1-5 min) of a K+-channel blocker, tetraethylammonium (TEA; 10(-2) M), increased the impedance magnitude and abolished, in a reversible manner, the resonant behavior. In all cases, the resonant frequency was decreased by TEA administration prior to total blockade of resonance. 3. The TEA-induced blockade of resonance was associated with decreases in the estimates of the membrane conductances, without significant alterations of input capacitance. A particularly large decrease was observed in Gr, the time-invariant resting conductance that includes a lumped leak conductance component. The voltage- and time-dependent conductance, GL, and associated relaxation time constant, tau u, also declined progressively during administration of TEA. 4. Systematic variations in the membrane potentials of trigeminal root ganglion neurons were produced by intracellular injections of long-lasting step currents with superposition of the oscillatory current stimuli, in order to assess the effects of TEA on the relationship of the electrical properties to the membrane potential. Applications of TEA led to a depolarizing shift in the dependence of the membrane property estimates, suggesting voltage-dependence of the effects of TEA on presumed K+ channels in the membrane. 5. These data suggest a primary involvement of K+ conductance in the genesis of membrane resonance. This electrical behavior or its ionic mechanism is a major modulator of the subthreshold electrical responsiveness of trigeminal root ganglion neurons.
Whole-cell and single-channel recordings of GABA-gated currents in cultured chick cerebral neurons
Authors: Weiss D. S. , Barnes E. M. , Hablitz J. J.
Published: December 2017

1. gamma-Aminobutyric acid (GABA) (10-500 microM) was applied to cultured chick cerebral neurons by pressure ejection, and the resulting currents (IGABA) were recorded using standard whole-cell voltage-clamp techniques. Plots of the peak IGABA as a function of membrane potential were nonlinear with an outwardly rectifying appearance. 2. IGABA decayed during a prolonged application of GABA. This decay was associated with a decline in the conductance of the cell, suggesting that the decline in IGABA was principally due to receptor desensitization. 3. After 5-7 days in culture, whole-cell recordings revealed the presence of spontaneous synaptic currents. These currents were presumed to be GABA-gated inhibitory postsynaptic currents (IPSCs) because they reversed at the Cl- equilibrium potential (ECl-), were blocked by picrotoxin (25 microM), and were prolonged by pentobarbital (50 microM). 4. Synaptic currents were analyzed by fitting exponential functions to their decay. In normal recording saline, 68% of the decays analyzed could be adequately described by a single exponential function. Two exponentials were necessary to describe the decay of the other 32%. The time constant of the decay (for those adequately fitted by a single exponential) increased with depolarization, from an average value of 15 ms at -80 mV to 60 ms at +40 mV. 5. A relationship was noted between IPSC amplitude and decay time constant; IPSCs with larger peak amplitudes had a slower decay. One possible explanation considered for this finding was that transmitter persists in the synaptic cleft and rebinds to the receptors, thus prolonging the decay of the IPSC. 6. Consistent with the above hypothesis was the observation that the decays of miniature IPCSs (examined under conditions of reduced transmitter release) were faster, showed less variability, and were all adequately described by a single exponential function. Furthermore, the decay times were independent of the membrane potential, suggesting that the kinetic parameters of the GABA channel which shape the decay of these miniature IPSCs are independent of voltage. 7. Single-channel activity underlying whole-cell GABA responses could be recorded in isolated outside-out and inside-out patches of membrane. In isotonic choline chloride, single-channel amplitudes were linearly related to voltage and reversed at -1.8 +/- 11.0 mV (n = 12). Under these conditions, the channel had a main conductance state of 20.8 +/- 3.4 pS (n = 12). Transitions were observed from this main conductance state to other conductance states, e.g., two subconductance states of 6 and 12 pS and one supraconductance state of 30 pS.(ABSTRACT TRUNCATED AT 400 WORDS)
Influence of auditory localization cues on neuronal activity in the auditory thalamus of the cat
Authors: Ivarsson C. , De Ribaupierre Y. , De Ribaupierre F.
Published: December 2017

1. The response properties of auditory thalamic neurons to the two major localization cues characterizing the azimuth of sound sources in the horizontal plane were investigated in cats. Single-unit responses to auditory stimuli (white noise and tones) presented with interaural phase differences (IPD) or interaural intensity differences (IID) were studied. 2. The proportion of neurons in the medial geniculate body that were sensitive to the localization cues tested was 28% for IPD (n = 253) and 37% for IID (n = 65). Half of the IID-sensitive units were also sensitive to IPD, but when the range of IPDs and IIDs to which each unit responded was converted to the sound-source locations that would generate those ranges they did not always correspond to overlapping azimuth angles. 3. The changes in discharge rate in response to the two localization cues occurred over very broad IPD and IID ranges. If this activity is involved in the representation of acoustic space, then the responses of individual neurons do not provide fine spatial tuning. 4. Contralateral and ipsilateral ear leads were represented in a continuous manner by the maximum discharge rate of IPD-sensitive units. On the other hand, units that were sensitive to IIDs were activated over one of two delimited ranges of IIDs. The first corresponded to IID combinations in which the stimulus was presented at a higher intensity in one ear than in the other (for 15/17 units the contralateral one); these were the lateralized intensity response field units. The second are the centered intensity response field units, whose responses were maximal when the intensity was equal in both ears and decreased when IIDs were introduced.
Excitatory synaptic actions between pairs of neighboring pyramidal tract cells in the motor cortex
Authors: Kang Y. , Endo K. , Araki T.
Published: December 2017

1. By spike-triggered averaging, we documented recurrent individual excitatory postsynaptic potentials (EPSPs) produced in 33 pyramidal tract (PT) cells (target) by the activity of axon collaterals of neighboring single PT cells (reference) in the motor cortex of the cat. 2. The computer was triggered by the spontaneous activity of reference PT cells or by current pulses applied to reference PT cells through the extracellular recording electrode. 3. The threshold for direct activation of PT cells was less than 0.1 microA with an anodal current pulse and 0.2-0.3 microA with a cathodal current pulse. 4. Application of an anodal current pulse directly activated only a single reference PT cell, the surface membrane of which was presumably touched by and sucked with the extracellular recording electrode. 5. When a cathodal current pulse was used, simultaneous activation of neurons or axons other than the reference PT cell was checked by changing the stimulus parameters along the characteristic strength-duration curve for the reference PT cell and/or by comparing averaged EPSPs obtained by cathodal stimulation with those obtained from spontaneous spikes of the reference PT cell. 6. Recurrent individual EPSPs were produced in fast PT cells by activation of neighboring slow PT cells and also of neighboring fast PT cells. Some recurrent individual EPSPs were also observed in slow PT cells. 7. The mean latencies of recurrent individual EPSPs produced by the spontaneous activity of reference slow and fast PT cells were 1.61 (n = 12) and 1.12 ms (n = 8), respectively. Their amplitudes ranged between 30 and 390 microV (n = 33). The rise time observed in fast PT cells with activation of slow and fast PT cells ranged from 1.6 to 3.6 ms (n = 20) and from 0.8 to 1.9 ms (n = 10), respectively. 8. The average conduction velocity of axon collaterals of slow and fast PT cells was estimated to be as slow as that of unmyelinated fibers in the cat. 9. It is suggested that axon collaterals of slow PT cells synapse onto more distal dendrites of fast PT cells than axon collaterals of fast PT cells.
Neuronal responses in rabbit cingulate cortex linked to quick-phase eye movements during nystagmus
Authors: Sikes R. W. , Vogt B. A. , Swadlow H. A.
Published: December 2017

1. Responses of single units in area 29 of cingulate cortex were examined in alert rabbits during vestibular and optokinetic nystagmus. Eye movements were measured by optically detecting the position of an infrared light-emitting diode attached to the cornea. 2. Fourteen percent of cingulate cells (68 of 477 isolated units) had responses that were correlated to the occurrence of quick phases. Latencies ranged from 60 ms before to 220 ms after the onset of the quick phase with a mean of 70 ms and standard deviation of 58 ms. Most units responded during or following quick phases, although four units had responses that preceded the quick-phase onset. 3. Unitary responses during quick phases were not due to visual field movement, since these responses occurred in the dark as well as the light. The responses were not dependent upon vestibular stimulation, since responses related to spontaneous saccadelike eye movements were observed in cingulate quick-phase neurons. 4. The majority (37 of 52) of the quick-phase neurons had a directional preference. Approximately equal numbers of directional units responded to quick phases directed ipsilaterally and contralaterally with respect to the recording site. 5. About one-fourth of the quick-phase units were bidirectional (15 of 52) with virtually equal responses to ipsilaterally and contralaterally directed quick phases. 6. Auditory and/or somatosensory responses were observed in only five of the quick-phase cells. All such multimodal units were bidirectional. 7. The quick-phase units were histologically confirmed to be primarily in area 29d of cingulate cortex. Although most cells were located in layer V, some were isolated in layer II-III. 8. Cingulate cortex has reciprocal connections with visual cortex and oculomotor-related thalamic nuclei and projects to the layers of the superior colliculus that are involved in oculomotor control. Responses to quick phases in cingulate neurons may synchronize cingulate cortex responsiveness with the arrival of new, and potentially significant, visual information.
Spatial and temporal determinants of directionally selective velocity preference in cat striate cortex neurons
Authors: Baker C. L.
Published: December 2017

1. Direction-selective properties of neurons in cat striate cortex (area 17) were studied with flashed and continuously moving bar stimuli. Receptive fields were characterized by measurement of static and dynamic parameters, which were correlated with the velocity preference exhibited by the same cells. 2. Each neuron was found to be direction selective to a limited range of velocities. This behavior was characterized by measuring the optimal velocity (Vopt) to elicit responses in the preferred and null directions that were maximally distinct. 3. A bar stimulus flashed sequentially at two nearby locations in the receptive field also produced direction-selective behavior, which was characterized by an optimal displacement (Dopt) to drive maximally distinct responses in the preferred versus null directions. 4. The static spatial receptive field properties were quantified by measurement of the receptive field size (2 sigma) and the spatial subunit wavelength (lambda). The latter quantity was measured as twice the separation between adjacent ON and OFF regions in simple cells and as twice the optimal separation for lateral inhibition between two simultaneously flashed bars in complex cells. 5. Direction-selective velocity preference for continuously moving stimuli, Vopt, was found to be highly correlated with lambda and with the Dopt for 2-flash motion; Vopt was also correlated to a lesser degree with 2 sigma. These results suggest a fundamental linkage between spatial frequency preference, velocity preference, and spatial tuning to 2-flash motion. 6. The range of measured direction-selective velocity preference values (Vopt) spanned about a 100-fold range, whereas the corresponding values of Dopt or lambda spanned substantially smaller ranges. This discrepancy suggested that the dynamic range of velocity preference among cortical neurons might be determined jointly by the measured spatial properties and by a temporal property that covaries with the measured spatial properties. 7. Temporal properties of striate cortical neurons were assessed from responses to flashed stimuli having a prolonged duration ("step responses"). Neurons typically responded in the following manner: after some latency (L), a transient rise in spike frequency occurred, which then adapted to some sustained level. The adaptation dynamics (extent of sustained vs. transient behavior) were quantified by the first-order time constant (AT) of the adaptation decay, and by the ratio of initial transient rise to final sustained level [adaptation ratio (AR)].(ABSTRACT TRUNCATED AT 400 WORDS)
The trajectory of human wrist movements
Authors: Stein R. B. , Cody F. W. , Capaday C.
Published: December 2017

1. To determine the form of human movement trajectories and the factors that determine this form, normal subjects performed wrist flexion movements against various elastic, viscous, and inertial loads. The subjects were instructed with visual and auditory feedback to make a movement of prescribed amplitude in a present period of time, but were free to choose any trajectory that fulfilled these constraints. 2. The trajectories were examined critically to determine if they corresponded to those which would minimize the root mean square (RMS) value of some kinematic variable or of energy consumption. The data agreed better with the trajectory that minimized the RMS value of jerk (the third derivative of length) than that of acceleration. However, systematic deviations from the minimum jerk predictions were consistently observed whenever movements were made against elastic and viscous loads. 3. Improved agreement could generally be obtained by assuming that the velocity profile varied according to a normal (Gaussian) curve. We conclude that minimization of jerk is not a general principle used by the nervous system in organizing voluntary movements, although movements may approach the predicted form, particularly under inertial loading conditions. 4. The EMG of the agonist muscles consisted of relatively simple waveforms containing ramplike increases and approximately exponential decays. The form of the movements could often be predicted quite well by using the EMG as an input to a linear second-order model of the muscle plus load. Rather than rigorously minimizing a kinematic variable or energy consumption, the nervous system may generate simple waveforms and adjust the parameters of these waveforms by trial and error until a trajectory is achieved that meets the requirements for a given load.
A slow calcium-dependent chloride conductance in clonal anterior pituitary cells
Authors: Rogawski M. A. , Inoue K. , Suzuki S. , Barker J. L.
Published: December 2017

1. Whole cell voltage-clamp recordings were made from GH3 cells, a clonal cell line initially derived from a rat anterior pituitary tumor, using patch electrodes filled with CsCl or N-methylglucamine chloride (NMG Cl). The bathing medium contained tetraethylammonium chloride (TEA; 20 mM) and NaCl (120 mM) or NMG Cl (140 mM). These conditions resulted in substantial blockade of outward currents. 2. Depolarizing voltage steps from a holding potential of -50 mV activated transient (T-type) and sustained (L-type) inward Ca2+ currents. In addition, prolonged depolarization (greater than 1 s) invariably elicited a slowly activating inward current that persisted with maintained depolarization, and deactivated slowly on repolarization, resulting in a prominent inward tail current. 3. This tail current could be recorded under conditions where Ca2+ and Cl- were the only membrane-permeant ions (symmetrical NMG Cl). The tail current nulled near 0 mV with symmetrical Cl- and showed a negative reversal potential with nominally Cl--free internal solution. Ba2+ substituted for Ca2+ as a carrier of inward current, but no tail current was expressed. These observations indicate that Cl- is the charge carrier of the slow inward tail current. 4. The voltage dependence for activation of the slow tail current was U-shaped with a peak at approximately -10 mV. This closely paralleled the voltage dependency of the Ca2+ currents. Recordings with 5 mM internal ethylene glycol-bis(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) to buffer intracellular Ca2+ to low nM levels exhibited slow inward tail currents that were of lower peak amplitude than with the usual 1.1 mM EGTA-containing pipette solution, but the kinetics of the currents were similar in both cases. In addition, the slow tail current was eliminated on superfusion with the Ca2+ channel blocker Cd2+ or with Ca2+-free medium. These results demonstrate that the current is dependent on Ca2+ influx; it is, therefore, referred to as ICl(Ca). 5. Activation of ICl(Ca) required depolarization of at least 1 s. More prolonged depolarizations activated progressively greater current, to a maximum with 6-s depolarization. In most cases, the decay of the tail current was described by a single exponential function with time constant approximately 0.8-0.9 s within the potential range -80 to -30 mV. At more depolarized potentials the decay was slower (increasing e-fold/20-mV change in membrane potential). 6. In a high proportion of cells, ICl(Ca) rapidly diminished in amplitude on repeated activation. This "rundown" occurred more rapidly than the rundown of the Ca2+ currents.(ABSTRACT TRUNCATED AT 400 WORDS)
The vestibular nerve of the chinchilla. II. Relation between afferent response properties and peripheral innervation patterns in the semicircular canals
Authors: Baird R. A. , Desmadryl G. , Fernandez C. , Goldberg J. M.
Published: December 2017

1. The relation between the response properties of semicircular canal afferents and their peripheral innervation patterns was studied by the use of intra-axonal labeling techniques. Fifty physiologically characterized units were injected with horseradish peroxidase (HRP) or Lucifer yellow CH (LY) and their processes were traced to the crista. The resting discharge, discharge regularity, and responses to both externally applied galvanic currents and sinusoidal head rotations were determined for most neurons. Terminal fields were reconstructed and, as in the preceding paper, the fibers were classified as calyx, bouton, or dimorphic units. 2. To determine if the intra-axonal sample was representative, the physiological properties of the labeled units were compared with those of a sample of extracellularly recorded units. A comparison was also made between the morphology of the intra-axonal units and those labeled by extracellular injection of HRP into the vestibular nerve Most of the discrepancies between the intra-axonal and the two extracellular samples can be explained by assuming that small-diameter fibers are underrepresented in the former sample. 3. A normalized coefficient of variation (CV*), independent of discharge rate, was used to classify units as regular, intermediate, or irregular. The CV* ranged from 0.020 to 0.60. Regular units (CV* less than or equal to 0.10) outnumbered irregular units (CV* greater than or equal to 0.20) by an approximately 3:1 ratio and had higher resting discharges. 4. Calyx units were invariably irregular. The one recovered bouton unit was regular. The discharge regularity of dimorphic units was related to their epithelial location, with those found in the periphery of the crista having a more regular discharge than those located more centrally. Dimorphic units, even those with quite similar morphology, can differ in their discharge regularity. Calyx and dimorphic units, which differ in their morphology, can both be irregular. These observations imply that discharge regularity is not determined by the branching pattern of a fiber or the number and types of hair cells it contacts. 5. The galvanic sensitivity (beta*) of an afferent, irrespective of its peripheral innervation pattern, was strongly correlated with CV*. This is consistent with the notion that discharge regularity and galvanic sensitivity are causally related, both being determined by postspike recovery mechanisms of the afferent nerve terminal.(ABSTRACT TRUNCATED AT 400 WORDS)