bluuebunny/crossref_metadata_2025 huggingface dataset:
Single voltage-dependent potassium channels in cultured rat hippocampal neurons
Authors: Rogawski M. A.
Published: December 2017

Single-channel recordings using the gigohm seal patch-clamp technique were carried out on the somatic membranes of dissociated embryonic rat hippocampal neurons grown in cell culture. The recording medium contained tetrodotoxin to block the voltage-dependent Na+ conductance and Cd2+ to block Ca2+ and Ca2+-activated conductances. In the cell-attached configuration, depolarizing voltage steps activated outward directed single-channel currents with conductance 15-20 pS. The channel openings exhibited a moderate degree of flickering. The mean burst lifetimes ranged from 5 to 13 ms with a tendency to increase slightly at more depolarized potentials (T = 21-25 degrees C). Reversal potential measurements using excised membrane patches indicated that the channels behaved as expected of a K+-selective membrane pore. Channel opening occurred in Ca2+-free EGTA-containing solutions but was never observed in the presence of tetraethylammonium (TEA; 20 mM). The frequency of channel opening increased as the membrane was depolarized by up to 50 mV from resting potential; the fraction of time spent in the open state during the first 300 ms following a step depolarization increased e-fold for a 8-25 mV change in potential. First-latency histograms and simulations of the macroscopic current based on channel data obtained during repeated depolarizing voltage steps indicated that the probability of the channel being in the open state increases gradually with time after a step depolarization. During repeated depolarizing steps the channels appeared to randomly enter and exit a long-lived inactive state. It is concluded that these channels may underly the slowly activating, very slowly inactivating, TEA-sensitive voltage-dependent K+ current (IK) in cultured hippocampal neurons.
Transient and delayed potassium currents in the Retzius cell of the leech, Macrobdella decora
Authors: Johansen J. , Kleinhaus A. L.
Published: December 2017

The properties of a quickly inactivating transient K current (IA) and a slowly inactivating delayed K current (IK) were investigated with two-electrode voltage-clamp techniques in the isolated soma of the Retzius cell of the leech, Macrobdella decora. The two currents could be pharmacologically separated according to their different sensitivities to tetraethylammonium ions (TEA) and 4-aminopyridine (4-AP). IA was totally blocked by 3 mM 4-AP but not affected by 25 mM TEA. IK was suppressed almost completely by 25 mM TEA, whereas its peak amplitude only decreased by 10-15% in 3 mM 4-AP. IA was activated at membrane potentials more positive than -35 to -30 mV, whereas the threshold for IK was at more positive potentials of approximately -20 to -15 mV. The activation of IA was rapid with a voltage-dependent time constant [tau m(A)] that varied from 6 to 2 ms for command potentials between -20 and 10 mV (at 22-24 degrees C). The inactivation, which was independent of voltage, was somewhat slower with a time constant (tau A) of approximately 90-110 ms. The time constants for activation [tau m(K)] and the early inactivation phase (tau K) of IK were both voltage dependent. In the range of potential steps from 0 to 30 mV, tau m(K) varied from 12 to 4.5 ms and tau K from 1,500 to 700 ms. The steady-state inactivation of IA varied with holding potential and was complete at potentials more positive than -30 mV. IA was fully available from potentials more negative than -70 mV. IK did not show steady-state inactivation below its threshold of activation. The time course of IA during a maintained depolarization could be reasonably described by the expression IA(t) = IA(infinity) [1-exp(-t/tau m(A))]2 exp(-t/tau A). The time course of activation of IK without allowance for inactivation was approximated by the expression IK(t) = IK(infinity) [1-exp(-t/tau m(K))]2. The reversal potentials and magnitude of both IA and IK were dependent on extra-cellular K concentration, which suggest that a substantial part of the two currents was carried by K ions.
Cat area 17. IV. Two types of corticotectal cells defined by controlling geniculate inputs
Authors: Weyand T. G. , Malpeli J. G. , Lee C. , Schwark H. D.
Published: December 2017

The dependence of cat area 17 corticotectal (CT) cells on specific subdivisions of the dorsal lateral geniculate (LGN) and medial interlaminar nuclei (MIN) was examined using reversible inactivation techniques. Inactivation of layer C of the LGN or layer 1 of the MIN did not block visual activity of CT cells driven through the contralateral eye. Inactivation of layer A of the LGN revealed two populations of CT cells: one strongly dependent on layer A and one whose visually driven activity survived layer A inactivation. CT cells that responded best to short stimuli (special complex cells) were least dependent on layer A, whereas cells that responded best to long stimuli (standard complex cells) were most dependent on layer A. We propose a model of the intracortical circuitry of these two types of CT cells. Standard complex cells, which are heavily dependent on layer A, receive sustaining visual input through layers 4 and/or 6. Special complex cells, which are not dependent on any single layer of the lateral geniculate nucleus, receive sustaining visual input from supragranular layers.
Viscerosomatic neurons in the lower thoracic spinal cord of the cat: excitations and inhibitions evoked by splanchnic and somatic nerve volleys and by stimulation of brain stem nuclei
Authors: Tattersall J. E. , Cervero F. , Lumb B. M.
Published: December 2017

Single-unit electrical activity has been recorded from 95 viscerosomatic neurons in the T9 and T11 segments of the cat's spinal cord. These neurons were excited by electrical and/or natural stimulation of visceral and somatic afferent fibers. The excitatory and inhibitory effects on these neurons of volleys in somatic and visceral afferent fibers and of electrical and chemical stimulation of the nucleus raphe magnus (NRM) and adjacent areas of the reticular formation (Ret. F.) have been studied. Electrical stimulation of the splanchnic nerve produced, after the initial excitation of the neurons, a period of inhibition lasting for up to 1 s. This inhibition reduced the responsiveness of the neurons to all inputs, somatic and visceral, and was still present after spinalization of the animals with cold block, which indicates a segmental organization of the inhibition. Electrical stimulation of afferent fibers within the somatic receptive field of the neurons produced, after the initial excitation, a period of inhibition similar to that induced by visceral afferent volleys. During this period of inhibition all inputs to the neurons were reduced. Reversible spinalization of the animals with cold block did not abolish this inhibition. On the basis of the effects of reversible spinalization on the visceral input to viscerosomatic neurons, two types of neurons were distinguished: 1) neurons whose visceral responses increased in the spinal state (neurons under tonic descending inhibition) and 2) neurons whose visceral responses were decreased or abolished in the spinal state (neurons subject to descending excitation). Neurons under tonic descending inhibition were inhibited by electrical stimulation of locations within the NRM and Ret. F. This inhibition lasted for less than 100 ms and could be evoked at intensities of stimulation of 100 microA or less. Neurons under descending excitation were also inhibited by electrical stimulation in the NRM and Ret. F. but, in addition, the inhibition was preceded by an excitation in 75% of these neurons. Chemical stimulation with DL-homocysteic acid (DLH) of locations within the NRM and Ret. F. was used to activate cell bodies, but not axons, located in these brain stem sites. The only effect observed following injections of DLH into the NRM and Ret. F. was inhibition of viscerosomatic neurons including those with descending excitation as well as those with descending inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)
Tooth pulp deafferentation is associated with functional alterations in the properties of neurons in the trigeminal spinal tract nucleus
Authors: Hu J. W. , Dostrovsky J. O. , Lenz Y. E. , Ball G. J. , Sessle B. J.
Published: December 2017

The effects of deafferentation of the tooth pulps of mandibular or maxillary teeth were investigated on the functional properties of single neurons recorded in the subnucleus oralis of the trigeminal (V) spinal tract nucleus of adult cats. Deafferentation was produced by endodontic removal, under sterile conditions, of the coronal pulp of the canine, premolar, and molar teeth. The subnucleus oralis of each animal was then studied electrophysiologically in a series of microelectrode penetrations of the subnucleus at a single postoperative time that varied between 3 days and 2 yr. Data from deafferented cats were compared with those obtained from control (unoperated) animals. The study was based on an examination of over 2,000 single units recorded on the side ipsilateral to the pulp deafferentation. In animals deafferented 7-15 days prior to brain stem neuron recording, tooth pulp deafferentation was associated with a statistically significant decrease compared with control animals in the incidence of neurons having a mechanoreceptive field localized within the mandibular or maxillary division; this decrease in incidence was coincident with a significant increase in the occurrence of neurons having a mechanoreceptive field involving two or three V divisions. Linear trend analysis indicated a progressive return to control values from the 7- to 15-day postoperative period. In deafferented cats there were also statistically significant increases in the incidence of neurons having spontaneous activity or showing rapidly habituating responses to brisk tap stimuli applied to the orofacial region; neurons having a receptive field consisting of discontinuous zones of mechanosensitivity were also encountered. The mean impulse frequency of spontaneous activity was not, however, significantly different between control and deafferented animals. The responsiveness of the habituating tap-sensitive neurons was further quantified and compared with neurons showing normal rapidly adapting (RA) features of their responses to mechanical orofacial stimuli. Whereas most (85%) of the RA neurons could faithfully follow stimuli applied by a mechanical stimulator at a mean maximal following frequency of 6.6 Hz and showed entrainment and 'turning curve' profiles comparable to those previously described for oralis neurons in normal animals, most of the habituating tap-sensitive neurons could not follow mechanical stimulus frequencies greater than 1 Hz (mean maximal following frequency 0.3 Hz) and none could be entrained sufficiently to allow for a determination of their tuning curve.(ABSTRACT TRUNCATED AT 400 WORDS)
Characterization of spontaneous and evoked inhibitory postsynaptic potentials in rat supraoptic neurosecretory neurons in vitro
Authors: Randle J. C. , Bourque C. W. , Renaud L. P.
Published: December 2017

Intracellular recordings from 52 supraoptic nucleus neurosecretory neurons in perfused explants of rat hypothalamus revealed abundant spontaneous inhibitory postsynaptic potentials (sIPSPs) and a compound evoked inhibitory postsynaptic potential (eIPSP) following electrical stimulation in the diagonal band of Broca (DBB). These IPSPs were characterized in terms of the magnitude and ionic specificity of the underlying current and in terms of the transmitter responsible for their activation. sIPSPs rose rapidly to peak within 3-5 ms and decayed exponentially with a mean time constant of 20.2 +/- 1.9 ms (mean +/- SE), a value 1.6-fold greater than the mean cell time constant of 13.8 +/- 1.0 ms. The eIPSPs rose rapidly to peak within 3-10 ms and decayed exponentially over 60-100 ms with a mean time constant of 37.0 +/- 2.8 ms, which is 2.6-fold greater than the mean cell time constant. These features imply a brief persistence of the conductance underlying the IPSPs. In recordings with KAcetate-filled micropipettes, sIPSPs were hyperpolarizing at membrane potentials in the range of -50 to -70 mV and reversed polarity when the membrane was hyperpolarized beyond -80 mV. The mean reversal potential (EsIPSP) was -72.4 +/- 1.1 mV. eIPSPs were hyperpolarizing at resting membrane potential and could be reversed by membrane hyperpolarization beyond a mean reversal potential (EIPSP) of -67.4 +/- 1.4 mV. In recordings with KCl-filled micropipettes, sIPSPs were depolarizing at all membrane potentials more negative than -50 mV. Under these conditions, EsIPSP was estimated at -44 mV. sIPSPs were absent when chloride ions were removed from the perfusion medium. eIPSPs were depolarizing at all membrane potentials and often evoked action potentials; mean EeIPSP was 43.2 mV. Reversal potentials of spontaneous and evoked IPSPs were similar. At a given membrane potential, sIPSP amplitudes varied widely between 1 and 20 mV. The conductance increase underlying individual sIPSPs was estimated to vary between 0.17 and 3.0 nS (avg 0.6 nS) against a mean resting input conductance of 3.78 +/- 0.41 nS. Estimates of the conductance underlying eIPSPs varied widely between cells, from 0.8 to 22.0 nS (mean 72 nS). Accordingly, the ratio of evoked to spontaneous IPSP conductance varied from 1.6 to 43.7 (mean 13.1). The reversal potential of evoked IPSPs shifted with the extracellular concentration of Cl- ions ([Cl-]0) with a mean slope of 41 mV/log [Cl-]0.(ABSTRACT TRUNCATED AT 400 WORDS)
The dendritic origins of penicillin-induced epileptogenesis in CA3 hippocampal pyramidal cells
Authors: Swann J. W. , Brady R. J. , Friedman R. J. , Smith E. J.
Published: December 2017

Experiments were performed in order to identify the sites of epileptiform burst generation in rat hippocampal CA3 pyramidal cells. A subsequent slow field potential was studied, which is associated with afterdischarge generation. Laminar field potential and current source-density (CSD) methods were employed in hippocampal slices exposed to penicillin. Simultaneous intracellular and extracellular field recordings from the CA3 pyramidal cell body layer showed that whenever an epileptiform burst was recorded extracellularly, individual CA3 neurons underwent an intense depolarization shift. In extracellular records a slow negative field potential invariably followed epileptiform burst generation. In approximately 10% of slices, synchronous afterdischarges rode on the envelope of this negative field potential. Intracellularly a depolarizing afterpotential followed the depolarization shift and was coincident with the extracellular slow negative field potential. A one-dimensional CSD analysis performed perpendicular to the CA3 cell body layer showed that during epileptiform burst generation large current sinks occur simultaneously in the central portions of both the apical and basilar dendrites. The average distance of the peak amplitude for these sinks from the center of the cell body layer was 175 +/- 46.8 microns and 158 +/- 25.0 microns, respectively. A large current source was recorded in the cell body layer. Smaller current sources were observed in the distal portions of the dendritic layers. During the postburst slow field potential a current sink was recorded at the edge of the cell body layer in stratum oriens--a region referred to as the infrapyramidal zone. Simultaneous with the current sink recorded there, smaller sinks were often observed in the dendritic layers that appeared to be "tails" or prolongations of the currents underlying burst generation. Two-dimensional analyses of these field potentials were performed on planes parallel and perpendicular to the exposed surface of the slice. Isopotential contours showed that the direction of extracellular current is mainly orthogonal to the CA3 laminae. Correction of CSD estimates made perpendicular to the cell body layer for current flowing in the other direction did not alter the location of computed current sources and sinks. In order to show that the dendritic currents associated with epileptiform burst generation were active sinks, tetrodotoxin (TTX) was applied locally to the dendrites where the current sinks were recorded.(ABSTRACT TRUNCATED AT 400 WORDS)
W-cells in the cat retina: correlated morphological and physiological evidence for two distinct classes
Authors: Stanford L. R.
Published: December 2017

Intracellular recording and iontophoresis of horseradish peroxidase were used to study the morphology of physiologically characterized W-cells in the cat retina. The recording experiments were performed in an in vivo preparation to allow the responses of these retinal ganglion cells to be compared with previous functional studies of these neurons. The physiological and morphological characteristics of 16 injected and recovered retinal W-cells were compared with similar data from 14 retinal X-cells injected in the same preparations. The soma sizes of retinal W-cells were found to fall into two distinct groups. The somata of the phasic W-cells, at every eccentricity, were smaller than the somata of tonic W-cells, with no overlap between the two distributions. Soma sizes of the tonic W-cells fell into the previously described “medium-sized” range of retinal ganglion cell soma sizes and were similar to, although slightly larger than, the soma sizes of physiologically identified beta- or X-cells. The dendritic arbors of all of the cells physiologically classified as tonic W-cells were similar. Every example of this type had four to five primary dendrites that branched a short distance from the soma to form a circular or cruciate dendritic arbor. The dendritic arrays of these cells were easily distinguishable from the compact dendritic arbors of the physiologically identified X-cells. The dendritic arbors of the phasic W-cells were much more heterogeneous, ranging from sparse, wide dendritic arbors to very compact dendritic arbors with many fine branches. No significant correlation was found between the extent of the dendritic arbor and the distance from the area centralis for either the tonic W-cells or the phasic W-cells. The axons of the tonic and phasic W-cells differed from one another and from X-cells on a number of different morphological and physiological measures. The intraretinal segments of the axons of the phasic W-cells had the smallest diameters of the three groups; the axons of X-cells in the retina were relatively large, and the axons of the tonic W-cells had diameters intermediate between the phasic W-cells and the X-cells. Although considerable overlap was seen between the X-cells, tonic W-cells, and phasic W-cells in their antidromic latencies to electrical stimulation of the optic chiasm, the intraretinal and extraretinal components of the conduction velocities of the three groups were significantly different.(ABSTRACT TRUNCATED AT 400 WORDS)
Beta-contributions to fusimotor action in triceps surae muscles of decerebrated cats
Authors: Grill S. E. , Rymer W. Z.
Published: December 2017

The discharge of spindle afferents from medial gastrocnemius and soleus muscles was recorded in the decerebrated cat preparation, under isometric conditions and during ramp and hold stretches. Motor output was varied systematically by manual stimulation of the contralateral hindlimb. Twenty-six of 34 afferents showed response patterns consistent with enhancement of dynamic and/or static fusimotor input with increasing muscle force. To establish whether force-related fusimotor effects were mediated at least partly by beta-input, beta-innervation to these same spindles was sought, using a ventral root stimulation protocol. Twenty-three of the 34 afferents were shown to receive beta-innervation, which was most often static in type. For two measures of fusimotor action, the slope of the afferent dynamic rate-length relation and the discharge rate measured during the last portion of ramp stretch, significant increases in the measure, which paralleled increases in muscle force, made it statistically more likely that the afferent received beta-innervation. Our measures did not successfully predict the type of beta-input (beta-static or beta-dynamic). Procaine block of gamma-fibers produced substantial reductions in fusimotor effect in seven spindle afferents (although modest residual fusimotor effects were detectable for 3/7 afferents). The severity of these reductions indicates that beta-action probably requires concurrent gamma-input to the spindle in order to be effective. In support of this possibility, the fusimotor effects of electrical stimulation of single beta-fibers were greatly reduced for five out of six afferents during procaine block of gamma-fibers, compared with the beta-effects recorded when modest levels of spontaneous gamma-activity were present. We conclude that beta-innervation to muscle spindles of triceps surae is common and that this innervation exerts significant fusimotor effects. It appears likely that beta-motoneurons are able to produce both static and dynamic effects above extrafusal threshold, but that the actions require on-going gamma-activity in order to be effective.
Activity-dependent changes in extracellular potassium and excitability in turtle olfactory nerve
Authors: Eng D. L. , Kocsis J. D.
Published: December 2017

The excitability properties of turtle olfactory nerve (o.n.) were studied in vitro using potassium-sensitive microelectrodes (KSM), a modified sucrose gap chamber, and a standard nerve chamber to measure conduction velocity. A pronounced supernormal period (SNP), as indicated by increased conduction velocity of the o.n. fiber volley, lasting up to several seconds, was observed following a single stimulus. The compound action potential recorded in the sucrose gap chamber showed a prolonged depolarization with a similar time course to the SNP. When stimulation intensity was submaximal the response amplitude, and the extracellular potassium concentration [K+]o, continuously increased during repetitive stimulation. In contrast, when supramaximal stimuli were applied, the amplitude of the o.n. fiber volley was reduced during a high-frequency stimulus train for all responses after the initial one even though latency was maximally reduced, i.e., during supernormal conduction. Superfusion with various levels of K+ elicited changes in the excitability of the o.n. fibers. Small increases in [K+]o above the resting concentration of 2.6 mM led to an increase in resting excitability, whereas larger increases resulted in decreased excitability and conduction block. The SNP was eliminated when extracellular potassium was elevated between 3 and 4 mM above resting levels. Microstimulation of a small bundle of o.n. fibers led to an increase in [K+]o along the bundle but also around adjacent nonactivated fibers. The excitability of these neighboring nonactivated fibers was increased, further indicating the importance of activity-dependent changes in [K+]o in modulating axonal excitability. These results demonstrate the importance of activity-dependent increases in extracellular potassium in modulating nonmyelinated o.n. fiber excitability. They also indicate that increases in [K+]o and an associated membrane depolarization contribute to the increased excitability observed during fiber recruitment and the supernormal period.
The effects of prolonged superfusions with acidic amino acids and their agonists on field potentials and horizontal cell photoresponses in the turtle retina
Authors: Perlman I. , Normann R. A. , Anderton P. J.
Published: December 2017

The effects of prolonged superfusions with acidic amino acids and their agonists, kainic acid (KA) and N-methyl-D-aspartate (NMDA), on horizontal cells, and extracellular field potentials were studied in the turtle everted eyecup preparation using simultaneous intracellular and extracellular recordings. In a fresh preparation initial superfusions with each of the above agents usually induced a large (up to 60 mV) transient negative extracellular field potential recorded adjacent to horizontal cells, followed by a sustained negative potential of lesser amplitude (up to 10 mV). The amplitude of the sustained potential did not vary with subsequent superfusions, whereas that of the transient phase was reduced. KA and NMDA were much more potent (at least 300 times) in evoking these field potentials than either acidic amino acid. The horizontal cell transmembrane potential was monitored as the difference between the intra- and extracellular potentials. Superfusion with KA and NMDA produced a triphasic time course of the drug effect consisting of an initial depolarization with reduced photoresponses, a rehyperpolarization of the membrane accompanied by a growth of the light responses followed by a gradual depolarization and loss of photoresponses. Superfusion with the acidic amino acids usually produced a biphasic response that resembled qualitatively the first two phases of the response to KA and NMDA. This biphasic response was occasionally followed by a gradual depolarization and loss of the light response. The kinetics of the transient component of the field potential and the rapid reduction and regrowth of the photoresponses recorded during superfusion with these agents suggests an initial action of these drugs, which is of a nonsynaptic origin and which may be an expression of a drug-induced spreading depression. The kinetics of the photoresponses recorded during superfusion with KA, L-aspartate, and L-glutamate were similar but differed from those recorded during superfusion with NMDA. The difference in the effects of NMDA and KA on photoresponse kinetics suggests that two types of acidic amino acid receptors may be present in the outer plexiform layer of the turtle retina.
Motor-unit properties following cross-reinnervation of cat lateral gastrocnemius and soleus muscles with medial gastrocnemius nerve. II. Influence of muscle on motoneurons
Authors: Foehring R. C. , Sypert G. W. , Munson J. B.
Published: December 2017

We tested whether the muscle innervated may influence the expression of motoneuron electrical properties. Properties of individual motor units were examined following cross-reinnervation (X-reinnervation) of cat lateral gastrocnemius (LG) and soleus muscles by the medial gastrocnemius (MG) nerve. We examined animals at two postoperative times: 9-10 wk (medX) and 9-11 mo (longX). For comparison, normal LG and soleus motoneuron properties were also studied. Motor units were classified on the basis of their contractile responses as fast contracting fatigable, fast intermediate fast contracting fatigue resistant, and slow types FF, FI, FR, or S, respectively) (9, 21). Motoneuron electrical properties (rheobase, input resistance, axonal conduction velocity, afterhyperpolarization) were measured. After 9-11 mo, MG motoneurons that innervated LG muscle showed recovery of electrical properties similar to self-regenerated MG motoneurons. The relationships between motoneuron electrical properties were largely similar to self-regenerated MG. For MG motoneurons that innervated LG, motoneuron type (65) predicted motor-unit type in 74% of cases. LongX-soleus motoneurons differed from longX-LG motoneurons or self-regenerated MG motoneurons in mean values for motoneuron electrical properties. The differences in overall means reflected the predominance of type S motor units. The relationships between motoneuron electrical properties were also different than in self-regenerated MG motoneurons. In all cases, the alterations were in the direction of properties of type S units, and the relationship between normal soleus motoneurons and their muscle units. Within motor-unit types, the mean values were typical for that type in self-regenerated MG. Motoneuron type (65) was a fairly strong predictor of motor-unit type in longX soleus. MG motoneurons that innervated soleus displayed altered values for axonal conduction velocity, rheobase, and input resistance, which could indicate incomplete recovery from the axotomized state. However, although mean afterhyperpolarization (AHP) half-decay time was unaltered by axotomy (25), this parameter was significantly lengthened in MG motoneurons that innervated soleus muscle. There were, however, individual motoneuron-muscle-unit mismatches, which suggested that longer mean AHP half-decay time may also be due to incomplete recovery of a subpopulation of motoneurons. Those MG motoneurons able to specify soleus muscle-fiber type exhibited motoneuron electrical properties typical of that same motoneuron type in self-regenerated MG.(ABSTRACT TRUNCATED AT 400 WORDS)
Interaural phase-sensitive units in the inferior colliculus of the unanesthetized rabbit: effects of changing frequency
Authors: Kuwada S. , Stanford T. R. , Batra R.
Published: December 2017

We studied the interaural phase sensitivity of 85 units in the inferior colliculus (IC) of the unanesthetized rabbit. We assessed this sensitivity at several frequencies within each unit's responsive range. The interaural phase disparity was varied by delivering tones that differed by 1 Hz to the two ears, resulting in a 1-Hz binaural beat. We analyzed each unit's response to different frequencies by calculating four measures: characteristic delay (CD), characteristic phase (CP), composite peak delay, and mean peak delay. We estimated the CD and CP from the slope and phase intercept, respectively, of the regression line fitted to a plot of the mean interaural phase against stimulating frequency. The composite peak delay was estimated from the peak of a composite delay curve. This was generated by replotting the response to changes in interaural phase, as a function of the equivalent interaural delay and averaging the resultant interaural delay curves. The composite delay curve reflects the unit's average response to interaural delays across frequencies. Last, we calculated a mean peak delay, derived by converting the mean interaural phase of the response at each frequency to an equivalent delay and then averaging these delays. Interaural phase sensitivity was observed to frequencies as high as 2,150 Hz. However, the majority of units showed such sensitivity below 1,500 Hz. For most units, the interaural delay curves measured at several frequencies coincided near the peak discharge. This result is consistent with a neural model, where excitatory inputs from each ear converge upon a binaural cell, evoking maximum discharge only when the two inputs arrive simultaneously. As a first approximation, our data fit this model, indicating that IC neurons can act like coincidence detectors or cross-correlators. The distributions of CD, composite peak delay, and mean peak delay showed that most units preferred ipsilateral stimulus delays, which in the natural situation corresponds to sounds emanating from the contralateral field. Moreover, most units preferred delays that were within the estimated physiological range of the rabbit. These results support the viewpoint that neurons in the IC participate in sound localization. The distributions of CP and CD differ substantially from those found in the IC of the anesthetized cat. These differences may reflect species differences, the effects of anesthesia, or a difference in the population of units sampled. For each unit, we assessed the linearity of the plot of mean interaural phase against frequency of stimulation using a chi 2 method. For most units the plots were significantly nonlinear.(ABSTRACT TRUNCATED AT 400 WORDS)
Basic electrophysiological properties of spinal cord motoneurons during old age in the cat
Authors: Morales F. R. , Boxer P. A. , Fung S. J. , Chase M. H.
Published: December 2017

1. The electrophysiological properties of alpha-motoneurons in old cats (14–15 yr) were compared with those of adult cats (1–3 yr). These properties were measured utilizing intracellular recording and stimulating techniques. 2. Unaltered in the old cat motoneurons were the membrane potential, action potential amplitude, and slopes of the initial segment (IS) and soma dendritic (SD) spikes, as well as the duration and amplitude of the action potential's afterhyperpolarization. 3. In contrast, the following changes in the electrophysiological properties of lumbar motoneurons were found in the old cats: a decrease in axonal conduction velocity, a shortening of the IS-SD delay, an increase in input resistance, and a decrease in rheobase. 4. In spite of these considerable changes in motoneuron properties in the old cat, normal correlations between different electrophysiological properties were maintained. The following key relationships, among others, were the same in adult and old cat motoneurons: membrane potential polarization versus action potential amplitude, duration of the afterhyperpolarization versus motor axon conduction velocity, and rheobase versus input conductance. 5. A review of the existing literature reveals that neither chronic spinal cord section nor deafferentation (13, 21) in adult animals produce the changes observed in old cats. Thus we consider it unlikely that a loss of synaptic contacts was responsible for the modifications in electrophysiological properties observed in old cat motoneurons. 6. We conclude that during old age there are significant changes in the soma-dendritic portion of cat motoneurons, as indicated by the modifications found in input resistance, rheobase, and IS-SD delay, as well as significant changes in their axons, as indicated by a decrease in conduction velocity.
Linear mechanism of orientation tuning in the retina and lateral geniculate nucleus of the cat
Authors: Soodak R. E. , Shapley R. M. , Kaplan E.
Published: December 2017

1. The orientation tuning of lateral geniculate nucleus (LGN) neurons and retinal ganglion cells (recorded as S potentials in the LGN) was investigated with drifting grating stimuli. 2. Results were compared with a quantitative model, in which receptive fields were constructed from linear, elliptical Gaussian center and surround subunits, and responses could be predicted to gratings of any spatial frequency at any orientation. 3. The orientation tuning of X and Y retinal ganglion cells and LGN neurons was shown to result from the linear mechanism of receptive-field elongation, as data from these cells could be well fit with this model. 4. The responses of LGN neurons and their input retinal ganglion cells were compared. The orientation tuning of LGN neurons was found to be a reflection of the tuning of their retinal inputs, showing that neither intrageniculate neural interactions nor the corticogeniculate projection play any role in LGN orientation selectivity.
Retrograde effects of target atrophy on submandibular ganglion neurons
Authors: Womble M. D. , Roper S.
Published: December 2017

1. To study the retrograde effects of changes in target tissue upon the innervating nerve supply, we have examined the parasympathetic submandibular ganglion of the adult rat. Neurons of this ganglion innervate the submandibular and sublingual salivary glands. 2. Ligating the salivary ducts leads to rapid and prolonged salivary gland cell atrophy. 3. Duct ligations, without direct injury to the glandular nerve supply, initially produced few alterations in the ganglion. After 8 wk, however, neuron number was reduced by 50%. The numbers of presynaptic inputs/neuron and synapses/neuron perimeter were not affected by the cell loss. 4. After 1 wk of duct ligation in which the glandular nerve supply was intentionally damaged, some ganglionic neurons have lost all presynaptic inputs, suggesting synaptic disjunction. This is followed at 3 wk by a 40% decrease in neuron number and an increase in the number of inputs per (remaining) ganglion cell. However, the number of synapses/neuronal profile was unchanged. 5. Thus axotomy plus target atrophy causes synaptic disjunction, neuron cell death, and input rearrangement, presumably due to a combination of direct injury effects and an abrupt loss of peripheral trophic supplies. 6. In contrast, target atrophy alone produced more gradual changes in submandibular ganglion neurons. Only prolonged target atrophy leads to a decrease in the number of ganglionic neurons, perhaps due to the gradual loss of peripheral trophic supplies. However, other features, such as the number of inputs/cell and the number of synapses/neuron perimeter, remain unaltered. Evidently, the gradual loss of trophic support does not result in synaptic disjunction to the degree needed to produce presynaptic input rearrangement.
Physiology and morphology of multireceptive neurons with C-afferent fiber inputs in the deep dorsal horn of the rat lumbar spinal cord
Authors: Woolf C. J. , King A. E.
Published: December 2017

Intracellular recording techniques have been used to study neurons that respond to low- and to high-intensity mechanical stimulation of the skin of the hindpaw (wide dynamic range or multireceptive cells) in the deep dorsal horn of the fourth lumbar segment of the spinal cord, in decerebrate-spinal rats. Electrical stimulation of the A-fibers in the sciatic nerve produced a short-latency response in all 32 neurons studied. A long-latency prolonged excitation was produced in 28 of the 32 neurons when the unmyelinated afferents in the sciatic nerve were activated. This paper describes the physiological properties of 12 multireceptive cells with A- and C-fiber inputs, whose cell body location was established by horseradish peroxidase ionophoresis and the morphology of six neurons in this group whose cell bodies lay within lamina V. Single stimuli to the sciatic nerve at an intensity high enough to activate unmyelinated afferent fibers (C-fiber strength) produced two patterns of response in the neurons. In five neurons a number of long-latency postsynaptic potentials (PSPs) clearly separated from the short-latency A-fiber evoked PSPs were produced, resulting in an early discharge, a silent period, and a late discharge. The second pattern, found in seven neurons, was a long-lasting depolarization, only generated by C-strength stimuli, which continued from the early A-fiber evoked PSPs, peaked at 100-200 ms, and lasted for 300-500 ms, producing in six cases a continuous burst of action potentials with a maximal frequency at the expected latency of the C-afferent fiber input but with no clear A- and C-fiber evoked banding of the action potentials. This postsynaptic depolarization was large enough to inactivate action potentials in one cell. Repeated stimuli to the sciatic nerve (1 Hz for 10 s) at C-fiber strength produced five different types of response in the neurons. In three neurons a progressive increase in the size and duration of the C-fiber PSPs occurred, resulting in an increase in the number of action potentials (windup), whereas in two, the repeated stimulation resulted in a progressive moderate depolarization of the neurons and an increase in the total number of action potentials evoked at both early and late latencies. Large depolarizations, sufficient to partially inactivate action potentials, developed during the repeated stimulation in two cells, effectively reducing the number of spikes evoked per stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)
The personalized auditory cortex of the mustached bat: adaptation for echolocation
Authors: Suga N. , Niwa H. , Taniguchi I. , Margoliash D.
Published: December 2017

1. In the mustached bat, Pteronotus parnellii, the "resting" frequency of the constant-frequency component of the second harmonic (CF2) of the orientation sound (biosonar signal) is different among individuals within a range from 59.69 to 63.33 kHz. The standard deviation of CF2 resting frequency is 0.091 kHz on the average for individual bats. The male's CF2 resting frequency (61.250 +/- 0.534 kHz, n = 58) is 1.040 kHz lower than the female's (62.290 +/- 0.539 kHz, n = 58) on the average. Females' resting frequencies measured in December are not different from those measured in April when almost all of them are pregnant. Therefore, the orientation sound is sexually dimorphic. 2. In the DSCF (Doppler-shifted CF processing) area of the auditory cortex, tonotopic representation differs among individual bats. The higher the CF2 resting frequency of the bat's own sound, the higher the frequencies represented in the DSCF area of that bat. There is a unique match between the tonotopic representation and the CF2 resting frequency. This match indicates that the auditory cortex is "personalized" for echolocation and that the CF2 resting frequency is like a signature of the orientation sound. 3. If a bat's resting frequency is normalized to 61.00 kHz, the DSCF area overrepresents 60.6-62.3 kHz. The central region of this overrepresented band is 61.1-61.2 kHz. This focal band matches the "reference" frequency to which the CF2 frequency of a Doppler-shifted echo is stabilized by Doppler-shift compensation. 4. Since DSCF neurons are extraordinarily sharply tuned in frequency, the personalization of the auditory cortex or system is not only suited for the detection of wing beats of insects, but also for the reduction of the masking effect on echolocation of consepecific's biosonar signals. 5. Because the orientation sound is sexually dimorphic and the auditory cortex is personalized, the tonotopic representation of the auditory cortex is also sexually dimorphic.
Enhancement of inferior temporal neurons during visual discrimination
Authors: Richmond B. J. , Sato T.
Published: December 2017

1. Previous results have shown that spatially directed attention enhances the stimulus-elicited responses of neurons in some areas of the brain. In the inferior temporal (IT) cortex, however, directing attention toward a stimulus mildly inhibits the responses of the neurons. Inferior temporal cortex is involved in pattern discrimination, but not spatial localization. If enhancement signifies that a neuron is participating in the function for which that part of cortex is responsible, then pattern discrimination, not spatial attention, should enhance responses of IT neurons. The influence of pattern discrimination behavior on the responses of IT neurons was therefore compared with previously reported suppressive influences of both spatial attention and the fixation point. 2. Single IT neurons were recorded from two monkeys while they performed each of five tasks. One task required the monkey to make a pattern discrimination between a bar and a square of light. In the other four tasks the same bar of light appeared, but the focus of spatial attention could differ, and the fixation point could be present or absent. Either attention to (without discrimination of) the bar stimulus or the presence of the fixation point attenuated responses slightly. These two suppressive influences produced a greater attenuation when both were present. 3. The visual conditions and motor requirements when the bar stimulus appeared in the discrimination task were identical to those of the trials in the stimulus attention task. However, one-half of the responsive neurons showed significantly stronger responses to the bar stimulus when it appeared in the discrimination task than when it appeared in the stimulus attention task. For most of these neurons, discrimination just overcame the combined effect of the two suppressive influences. For six other neurons, the response strength was significantly greater during the discrimination task than during any other task. 4. The monkeys achieved an overall correct performance rate of 90% in both the discrimination and stimulus attention tasks. To achieve this performance in the discrimination task they adopted a strategy in which they performed one trial type, bar stimulus attention trials, perfectly (100%) and the other trial type, pattern trials, relatively poorly (84% correct).(ABSTRACT TRUNCATED AT 400 WORDS)
Signal transmission in the catfish retina. IV. Transmission to ganglion cells
Authors: Sakai H. M. , Naka K.
Published: December 2017

1. To characterize the temporal dynamic responses of ganglion cells and to define the possible inputs giving rise to their responses in catfish retina, we recorded the ganglion cell responses evoked by 1) a step of light presented in the dark, 2) an incremental and decremental step from a background illumination, and 3) a white-noise modulated light. 2. For comparison, we recorded the responses of preganglionic cells evoked by the same set of stimuli as used for the ganglion cells. Type-C cells produced on-off transient depolarizations to step stimuli, whether presented in the dark or an illuminated background. Type-N amacrine cells produced complex transient responses to incremental and decremental steps, whereas their step-evoked responses in the dark were sustained polarizations. Bipolar cells produced sustained responses to all step stimuli. 3. Ganglion cells were classified into three types, based on their responses evoked by incremental and decremental steps of light. One class of ganglion cells produced responses similar to those of type-C cells, the second class produced responses similar to those of type-N cells, and the third class resembled bipolar cell responses, although spike discharges accompanied the ganglion cell responses. 4. The analysis of the first-order kernels indicates that the temporal properties of linear dynamic responses are established at the level of bipolar cells and encoded into spike trains of ganglion cells without a major transformation. 5. The second-order nonlinearity appeared at the amacrine cell level. Type-C and type-N cells produced a second-order kernel characteristic of each cell type. The second-order kernels produced in ganglion cells were similar to those produced either by type-C or type-N cells. 6. We conclude that bipolar cells are the major source of linear components of ganglion cell responses and that type-C and type-N amacrine cells are the major source of the nonlinear responses. These linear and second-order nonlinear signals were encoded into spike trains by ganglion cells without a major transformation of the temporal response properties.
The role of the posterior vermis of monkey cerebellum in smooth-pursuit eye movement control. I. Eye and head movement-related activity
Authors: Suzuki D. A. , Keller E. L.
Published: December 2017

1. The observation of smooth-pursuit eye and retinal image velocity signals in lobules VI and VII of the vermis has given rise to the hypothesis that a neural correlate of a target velocity signal exists in this region of the cerebellum (29). However, activity signaling head velocity is also required to regenerate a target velocity signal. Vermal Purkinje cell activity was, therefore, recorded during the performance of paradigms designed to dissociate head movement-related responses. 2. The activity of 107 Purkinje cells was found to be related to horizontal head velocity. Of these, 52% increased their discharge rate for ipsilaterally directed passive head movement (type I), and 48% were excited by contralateral head movements (type II). 3. In five Purkinje cells in which sufficient data were obtained, cell discharge rate increased monotonically with head velocity over the range of 5–40 deg/s. The sensitivity to head velocity at 0.4 Hz +/- 25 deg/s averaged approximately 0.5 spikes.s-1/deg.s-1 in a larger sample of cells (n = 39). The sensitivities to head velocity, at this same frequency and velocity, of type I and type II Purkinje cells were comparable at 0.44 and 0.51 spikes.s-1/deg.s-1, respectively. 4. The Purkinje cell responses led head velocity by an average of 12 degrees at 0.4 Hz +/- 25 deg/s of passive head rotation. The phase shifts associated with type I and II responses were similar with phase leads of 13 and 9 degrees with respect to head velocity, respectively. 5. A linear interaction of smooth-pursuit eye and head velocity signals was observed during the performance of a variety of antiphase and inphase eye and head movement paradigms. The results support the conclusion that some Purkinje cells in lobules VI and VII of the cerebellar vermis encode a gaze velocity signal. Contributions of the head velocity signal to the regeneration of target velocity are considered in a companion paper (32).