bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophysiological Properties of Cultured Neonatal Rat Dorsal Horn Neurons Containing GABA and Met-Enkephalin-Like Immunoreactivity
Authors: Jo Y. H. , Stoeckel M. E. , Schlichter R.
Published: December 2017

Jo, Y. H., M. E. Stoeckel, and R. Schlichter. Electrophysiological properties of cultured neonatal rat dorsal horn neurons containing GABA and met-enkephalin-like immunoreactivity. J. Neurophysiol. 79: 1583–1586, 1998. We have developed a culture of neurons dissociated from the most superficial laminae of the neonatal rat spinal cord dorsal horn (DH). By using the perforated patch-clamp technique, we distinguished four types of neurons based on their firing properties in response to intracellular injection of 900 ms lasting current pulses. Type 1 neurons were characterized by a tonic firing. Type 2 neurons displayed marked spike accommodation and fired brief (<500 ms) bursts of action potentials, whereas type 3 neurons fired a single spike. Type 4 neurons exhibited different types of firing patterns, but all of them possessed a time-dependent inwardly rectifying current activated by membrane hyperpolarization. Met-enkephalin-like immunoreactivity (met-ENK-LI) and glutamic acid decarboxylase-like immunoreactivity (GAD-LI) were colocalized in 42% of the neurons ( n = 59), which were previously identified electrophysiologically. Type 1–4 neurons represented respectively 4, 64, 20, and 12% of the population of neurons colocalizing met-ENK-LI and GAD-LI. We conclude that the electrophysiological properties of DH neurons present in our cultures are similar to those described in acute slice or hemisected spinal cord preparations and that met-ENK-LI and GABA-LI are preferentially colocalized in type 2 neurons.
Somadendritic Backpropagation of Action Potentials in Cortical Pyramidal Cells of the Awake Rat
Authors: Buzsáki György , Kandel Adam
Published: December 2017

Buzsáki, György and Adam Kandel. Somadendritic backpropagation of action potentials in cortical pyramidal cells of the awake rat. J. Neurophysiol. 79: 1587–1591, 1998. The invasion of fast (Na+) spikes from the soma into dendrites was studied in single pyramidal cells of the sensorimotor cortex by simultaneous extracellular recordings of the somatic and dendritic action potentials in freely behaving rats. Field potentials and unit activity were monitored with multiple-site silicon probes along trajectories perpendicular to the cortical layers at spatial intervals of 100 μm. Dendritic action potentials of individual layer V pyramidal neurons could be recorded up to 400 μm from the cell body. Action potentials were initiated at the somatic recording site and traveled back to the apical dendrite at a velocity of 0.67 m/s. Current source density analysis of the action potential revealed time shifted dipoles, supporting the view of active spike propagation in dendrites. The presented method is suitable for exploring the conditions affecting the somadendritic propagation action of potentials in the behaving animal.
Theta-Frequency Resonance in Hippocampal CA1 Neurons In Vitro Demonstrated by Sinusoidal Current Injection
Authors: Leung L. Stan , Yu Hui-Wen
Published: December 2017

Leung, L. Stan and Hui-Wen Yu. Theta-frequency resonance in hippocampal CA1 neurons in vitro demonstrated by sinusoidal current injection. J. Neurophysiol. 79: 1592–1596, 1998. Sinusoidal currents of various frequencies were injected into hippocampal CA1 neurons in vitro, and the membrane potential responses were analyzed by cross power spectral analysis. Sinusoidal currents induced a maximal (resonant) response at a theta frequency (3–10 Hz) in slightly depolarized neurons. As predicted by linear systems theory, the resonant frequency was about the same as the natural (spontaneous) oscillation frequency. However, in some cases, the resonant frequency was higher than the spontaneous oscillation frequency, or resonance was found in the absence of spontaneous oscillations. The sharpness of the resonance ( Q), measured by the peak frequency divided by the half-peak power bandwidth, increased from a mean of 0.44 at rest to 0.83 during a mean depolarization of 6.5 mV. The phase of the driven oscillations changed most rapidly near the resonant frequency, and it shifted about 90° over the half-peak bandwidth of 8.4 Hz. Similar results were found using a sinusoidal function of slowly changing frequency as the input. Sinusoidal currents of peak-to-peak intensity of >100 pA may evoke nonlinear responses characterized by second and higher harmonics. The theta-frequency resonance in hippocampal neurons in vitro suggests that the same voltage-dependent phenomenon may be important in enhancing a theta-frequency response when hippocampal neurons are driven by medial septal or other inputs in vivo.
Spinal Mechanisms Underlying Persistent Pain and Referred Hyperalgesia in Rats With an Experimental Ureteric Stone
Authors: Roza Carolina , Laird Jennifer M. A. , Cervero Fernando
Published: December 2017

Roza, Carolina, Jennifer M. A. Laird, and Fernando Cervero. Spinal mechanisms underlying persistent pain and referred hyperalgesia in rats with an experimental ureteric stone. J. Neurophysiol. 79: 1603–1612, 1998. Spinal neurons processing information from the ureter have been characterized in rats 1–4 days after the implantation of an experimental ureteric stone and compared with those of normal rats. The effects of a conditioning noxious stimulation of the ureter in the presence of the hyperalgesia evoked by the calculosis also were examined. Extracellular recordings were performed at the T12–L1 segments of the spinal cord. In rats with calculosis, more neurons expressed a ureter input (53 vs. 42% in normal rats); such cells being more likely to show background activity, at a higher rate than normals (6.6 ± 1.2 vs. 3.2 ± 0.9 spikes/s; mean ± SE) and increasing with the continuing presence of the stone. The threshold pressure for a ureteric response was higher than in normal rats (79 ± 5 vs. 54 ± 4 mmHg) but the neurons failed to encode increasing intensities of stimulation. Thirty-five percent of the neurons with exclusively innocuous somatic receptive fields had a ureter input in rats with calculosis, whereas none were seen in normal rats. A noxious ureteric distention applied to neurons with ureter input evoked a complex mixture of increases and decreases in somatic receptive field size and/or somatic input properties markedly different from the generalized increases in excitability seen when such a stimulus was applied to normal animals. We conclude that the presence of a ureteric stone evokes excitability changes of spinal neurons (enhanced background activity, greater number of ureter-driven cells, decreased threshold of convergent somatic receptive fields), which likely account for the referred hyperalgesia seen in rats with calculosis. However, further noxious visceral input occurring in the presence of persistent hyperalgesia produces selective changes that cannot be explained by a generalized excitability increase and suggest that the mechanisms underlying maintenance of hyperalgesia include alteration of both central inhibitory and excitatory systems.
Primary Somatosensory Cortical Neuronal Activity During Monkey's Detection of Perceived Change in Tooth-Pulp Stimulus Intensity
Authors: Iwata Koichi , Tsuboi Yoshiyuki , Sumino Rhyuji
Published: December 2017

Iwata, Koichi, Yoshiyuki Tsuboi, and Rhyuji Sumino. Primary somatosensory cortical neuronal activity during monkey's detection of perceived change in tooth-pulp stimulus intensity. J. Neurophysiol. 79: 1717–1725, 1998. To elucidate the functional properties of primary somatosensory cortical neurons for the perception of tooth-pulp sensation, neuronal activity was recorded from the primary somatosensory cortex (SI) in awake behaving monkeys. Monkeys were trained to detect changes in tooth-pulp stimulus intensity applied to the upper canine or incisor tooth pulp. Stimulus intensities applied to the tooth pulp were multiples of the threshold intensity for the jaw opening reflex (1.0 T) elicited by tooth-pulp stimulation. When monkeys pressed a button, baseline electrical pulses (V1: 0.5 T, 1.0 T, 2.0 T, or 3.0 T) were applied to the tooth pulp. After 4–8 s, a V2 stimulus (0.3 T, 0.5 T, 1.0 T, or 2.0 T) was added to V1. Percent escapes at V1 stimulus intensity of 0.5 T and 1.0 T were ∼10%, 22% at 2.0 T, and 40% at 3.0 T (total of 1,997 trials). A total of 862 single units were recorded from the SI. Thirty-seven SI neurons responded to electrical stimulation of the tooth pulp (tooth-pulp–driven neurons; TPNs), 139 SI neurons responded to tactile stimulation of the lateral face area, 90 to upper lip and 99 to lower lip, 44 to tongue and 102 to periodontal membrane, whereas 351 SI neurons were not responsive to tactile stimulation of the orofacial regions. Thirty of 37 TPNs were recorded long enough to test with V1 stimuli ranging from 0.5 T to 3.0 T. Eleven of 30 TPNs linearly increased their firing frequency following increases in stimulus intensity (encoding TPNs), whereas 19 did not (nonencoding TPNs). Mean first spike latency of encoding TPNs was 24.8 ± 1.7 ms ( n = 11), that of nonencoding TPNs was 23.6 ± 1.5 ms ( n = 19), and that of unclassified TPNs was 24.7 ± 3.7 ms ( n = 7). TPNs were distributed in the areas 1–2, 3a, and 3b within the oral projection area and the transition zone between the face and oral projection areas of the SI. All of them received inputs from the intraoral structures, facial skin, or both. The firing frequency of eight encoding and nonencoding TPNs was correlated with detection latency at stimulus intensities of 0.5 and 1.0 T. On the other hand, when the baseline stimulus was increased to 2.0 T and 3.0 T, the discharge of most TPNs did not increase in firing frequency with the reduction in detection latency. These results indicate that the discharge rates of some SI TPNs are correlated with detection latency at near-noxious threshold and noxious stimulus intensities. These findings suggest that some TPNs are involved in the sensory-discriminative aspect of tooth-pulp sensation in the near-pain threshold and pain ranges.
Glucose-Induced Intracellular Ion Changes in Sugar-Sensitive Hypothalamic Neurons
Authors: Silver Ian A. , Erecinska Maria
Published: December 2017

Silver, Ian A. and Maria Erecińska. Glucose-induced intracellular ion changes in sugar-sensitive hypothalamic neurons. J. Neurophysiol. 79: 1733–1745, 1998. In the lateral hypothalamic area (LHA) of rat brain, ∼30% of cells showed sensitivity to small changes in local concentrations of glucose. These “glucose-sensitive” neurons demonstrated four types of behavior, three of which probably represent segments of a continuous spectrum of recruitment in response to ever more severe changes in blood sugar. Type I cells showed maximum activity ≤5.6 mM blood glucose but became completely silent at hyperglycemia of 10–12 mM (normoglycemia 7.6 ± 0.3 mM; mean ± SD). Type II and III neurons exhibited a wider range of response. Type IV cells (5–7% of glucose-sensitive neurons) paralleled the behavior of sugar-sensitive cells in ventromedial hypothalamic nucleus (VMH). In VMH, ∼40% of cells responded to changes in blood glucose over a range of concentrations from 3.6 to 17 mM, by increasing their firing rate as sugar level rose and vice versa. Ionic shifts during increases in blood (brain) glucose levels were similar in LHA types I–III but fastest in I and slowest in III. [Na+]ifell by 5–9 mM, [K+]irose by 6–8 mM, and plasma membrane hyperpolarized by 5 mV. [Ca2+]ideclined by 15–20 nM in line with membrane hyperpolarization. In VMH and type IV LHA cells, [K+]ifell 3–8 mM and plasma membrane depolarized −3 to −5 mV as blood/brain glucose concentration increased from 7.6/2.4 to 17.6/4.2 mM, whereas [Ca2+]iincreased from 125 to 180 nM as a consequence of falling membrane potential. During falls in blood/brain sugar concentration the effects in both VMH and LHA cells were reversed. The findings are consistent with the ionic shifts in types I–III LHA cells being dependent on alterations in Na/K-ATPase activity, whereas those in VMH and type IV LHA cells could be caused by modulation of ATP-dependent K+channels. A possible mechanism for linking the effects of small changes in glucose to ATP generation, which could bring about the above phenomena, is the interposition of a “glucokinase-type” enzyme in a role similar to that which it has in glucose-sensing pancreatic β-cells.
Modulation of Synaptic Transmission by Dopamine and Norepinephrine in Ventral but not Dorsal Striatum
Authors: Nicola Saleem M. , Malenka Robert C.
Published: December 2017

Nicola, Saleem M. and Robert C. Malenka. Modulation of synaptic transmission by dopamine and norepinephrine in ventral but not dorsal striatum. J. Neurophysiol. 79: 1768–1776, 1998. Although the ventral striatum (nucleus accumbens; NAc) and dorsal striatum are associated with different behaviors, these structures are anatomically and physiologically similar. In particular, dopaminergic afferents from the midbrain appear to be essential for the normal functioning of both nuclei. Although a number of studies have examined the effects of dopamine on the physiology of NAc or striatal cells, results have varied, and few studies have compared directly the actions of dopamine on both of these nuclei. Here we use slice preparations of the NAc and dorsal striatum to compare how synaptic transmission in these nuclei is modulated by catecholamines. As previously reported, dopamine depressed excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in the NAc. Surprisingly, however, neither EPSPs nor IPSPs in the dorsal striatum were affected by dopamine. Similarly, norepinephrine depressed excitatory synaptic transmission in the NAc by an α-adrenergic receptor-dependent mechanism but was without effect on excitatory transmission in the dorsal striatum. Inhibitory synaptic transmission was not affected by norepinephrine in either structure. These results suggest that the functional roles of dopamine and norepinephrine are not the same in the dorsal striatum and the NAc.
New Look at Force-Frequency Relationship of Human Skeletal Muscle: Effects of Fatigue
Authors: Binder-Macleod Stuart A. , Lee Samuel C. K. , Fritz April D. , Kucharski Lorin J.
Published: December 2017

Binder-Macleod, Stuart A., Samuel C. K. Lee, April D. Fritz, and Lorin J. Kucharski. New look at force-frequency relationship of human skeletal muscle: effects of fatigue. J. Neurophysiol. 79: 1858–1868, 1998. A muscle does not have a unique force-frequency relationship; rather, it is dynamic and depends on the activation history of muscle. The purpose of this study was to investigate the force-frequency relationship of nonfatigued and fatigued skeletal muscle with the use of both catchlike-inducing trains (CITs) that exploited the catchlike property of skeletal muscle and constant-frequency trains (CFTs). Quadriceps femoris muscles were studied during isometric contractions in twelve healthy subjects (5 females, 7 males). Both the peak force and force-time integrals produced in response to each stimulation train were analyzed. Compared with nonfatigued muscles, higher frequencies of activation were needed to produce comparable normalized peak forces when the muscles were fatigued (i.e., a “rightward” shift in the force-frequency relationship) for both the CFTs and the CITs. When using the normalized force-time integral to measure muscle performance, the CFTs required slightly higher frequencies to produce comparable normalized forces from fatigued muscles, but the CITs did not. Furthermore, when the muscles were fatigued, the CITs produced greater peak forces and force-time integrals than all comparable CFTs with frequencies ≤20 pps. In general, the lower the frequency the greater the augmentation produced by the CITs. In addition, the CIT that elicited the greatest force-time integral produced a 25% greater force-time integral than the best CFT. Because the CITs augmented forces across a wide range of physiological relevant activation rates, these results may have important clinical implications when using electrical stimulation to aid patients with paralysis. The results of this study contribute to our understanding of the relationship between the activation pattern of a muscle and the force output produced.
Noise-Induced Tuning Curve Changes in Mechanoreceptors
Authors: Ivey Chandra , Apkarian A. Vania , Chialvo Dante R.
Published: December 2017

Ivey, Chandra, A. Vania Apkarian, and Dante R. Chialvo. Noise-induced tuning curve changes in mechanoreceptors. J. Neurophysiol. 79: 1879–1890, 1998. Fibers from the tibial nerve of rat were isolated and spike activity recorded using monopolar hook electrodes. The receptive field (RF) of each recorded unit on the glabrous skin of the foot was mechanically stimulated with waveforms comprised of various frequency sine waves in addition to increasing levels of white noise. Single-unit responses were recorded for both rapidly adapting (RA) and slowly adapting (SA) units. Signal-to-noise ratio (SNR) of the output was quantified by the correlation coefficient ( C 1) between the input sine wave and the nerve responses. The addition of noise enhanced signal transmission in both RA and SA fibers. With increasing noise, the initially inverted “V”-shaped, zero-noise tuning curves for RA fibers broadened and eventually inverted. There was a large expansion of the frequencies that the RA receptor responded to with increasing noise input. On the other hand, the typical shape of the SA fiber tuning curves remained invariant, at all noise levels tested. C 1 values continued to increase with larger noise input for higher frequencies, but did not do so at the lowest frequencies. For both RA and SA fibers the responses with added noise tended to be rate modulated at the low-frequency end, and followed nonlinear stochastic resonance (SR) properties at the higher frequencies. The changes in the tuning properties due to noise found here, as well as preliminary psychophysics data, imply that external noise is relevant for sensing small periodic signals in the environment. All current models of sensory perception assume that the tuning properties of receptors determined in the absence of noise are preserved during everyday tasks. Our results indicate that this is not true in a noisy environment.
Postsaccadic Enhancement of Initiation of Smooth Pursuit Eye Movements in Monkeys
Authors: Lisberger Stephen G.
Published: December 2017

Lisberger, Stephen G. Postsaccadic enhancement of initiation of smooth pursuit eye movements in monkeys. J. Neurophysiol. 79: 1918–1930, 1998. Step-ramp target motion evokes a characteristic sequence of presaccadic smooth eye movement in the direction of the target ramp, catch-up targets to bring eye position close to the position of the moving target, and postsaccadic eye velocities that nearly match target velocity. I have analyzed this sequence of eye movements in monkeys to reveal a strong postsaccadic enhancement of pursuit eye velocity and to document the conditions that lead to that enhancement. Smooth eye velocity was measured in the last 10 ms before and the first 10 ms after the first saccade evoked by step-ramp target motion. Plots of eye velocity as a function of time after the onset of the target ramp revealed that eye velocity at a given time was much higher if measured after versus before the saccade. Postsaccadic enhancement of pursuit was recorded consistently when the target stepped 3° eccentric on the horizontal axis and moved upward, downward, or away from the position of fixation. To determine whether postsaccadic enhancement of pursuit was invoked by smear of the visual scene during a saccade, I recorded the effect of simulated saccades on the presaccadic eye velocity for step-ramp target motion. The 3° simulated saccade, which consisted of motion of a textured background at 150°/s for 20 ms, failed to cause any enhancement of presaccadic eye velocity. By using a strategically selected set of oblique target steps with horizontal ramp target motion, I found clear enhancement for saccades in all directions, even those that were orthogonal to target motion. When the size of the target step was varied by up to 15° along the horizontal meridian, postsaccadic eye velocity did not depend strongly either on the initial target position or on whether the target moved toward or away from the position of fixation. In contrast, earlier studies and data in this paper show that presaccadic eye velocity is much stronger when the target is close to the center of the visual field and when the target moves toward versus away from the position of fixation. I suggest that postsaccadic enhancement of pursuit reflects activation, by saccades, of a switch that regulates the strength of transmission through the visual-motor pathways for pursuit. Targets can cause strong visual motion signals but still evoke low presaccadic eye velocities if they are ineffective at activating the pursuit system.
Development of Excitatory Circuitry in the Hippocampus
Authors: Hsia Albert Y. , Malenka Robert C. , Nicoll Roger A.
Published: December 2017

Hsia, Albert Y., Robert C. Malenka, and Roger A. Nicoll. Development of excitatory circuitry in the hippocampus. J. Neurophysiol. 79: 2013–2024, 1998. Assessing the development of local circuitry in the hippocampus has relied primarily on anatomic studies. Here we take a physiological approach, to directly evaluate the means by which the mature state of connectivity between CA3 and CA1 hippocampal pyramidal cells is established. Using a technique of comparing miniature excitatory postsynaptic currents (mEPSCs) to EPSCs in response to spontaneously occurring action potentials in CA3 cells, we found that from neonatal to adult ages, functional synapses are created and serve to increase the degree of connectivity between CA3-CA1 cell pairs. Neither the probability of release nor mean quantal size was found to change significantly with age. However, the variability of quantal events decreases substantially as synapses mature. Thus in the hippocampus the developmental strategy for enhancing excitatory synaptic transmission does not appear to involve an increase in the efficacy at individual synapses, but rather an increase in the connectivity between cell pairs.
Electrophysiological and Pharmacological Characterization of the Direct Perforant Path Input to Hippocampal Area CA3
Authors: Berzhanskaya Julia , Urban Nathaniel N. , Barrionuevo German
Published: December 2017

Berzhanskaya, Julia, Nathaniel N. Urban, and German Barrionuevo. Electrophysiological and pharmacological characterization of the direct perforant path input to hippocampal area CA3. J. Neurophysiol. 79: 2111–2118, 1998. Monosynaptic perforant path responses evoked by subicular stimulation were recorded from CA3 pyramidal cells of rat hippocampal slices. These monosynaptic responses were isolated by using low intensities of stimulation and by placing a cut through the mossy fibers. Perforant path–evoked responses consisted of both excitatory and inhibitory components. Excitatory postsynaptic currents (EPSCs) were mediated by both α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acidreceptors (AMPAR) and N-methyl-d-aspartate receptors (NMDAR).Inhibitory postsynaptic currents consisted of γ-aminobutyric acid-A (GABAA-) and -B (GABAB)-receptor–mediated components. At membrane potentials more positive than -60 mV and at physiological [Ca2+]/[Mg2+] ratios, >30% of perforant path evoked EPSC was mediated by NMDARs. This value varied as a function of the membrane voltage and external [Mg2+]. Two types of responses were observed after low-intensity stimulation of the perforant path. The first type of response showed paired-pulse facilitation and was reduced by 2-amino-4-phosphonobutyric acid (AP4). The second type of response showed paired-pulse depression and was reduced by baclofen. Electrophysiological and pharmacological characteristics of these two types of responses are similar to the properties of lateral and medial perforant path–evoked EPSPs in the dentate gyrus.
Handedness and Asymmetry of Hand Representation in Human Motor Cortex
Authors: Volkmann J. , Schnitzler A. , Witte O. W. , Freund H.-J.
Published: December 2017

Volkmann, J., A. Schnitzler, O. W. Witte, and H.-J. Freund. Handedness and asymmetry of hand representation in human motor cortex. J. Neurophysiol. 79: 2149–2154, 1998. The cortical representation of five simple hand and finger movements in the human motor cortex was determined in left- and right-handed people with whole-head magnetoencephalography. Different movements were found to be represented by spatially segregated dipolar sources in primary motor cortex. The spatial arrangement of neuronal sources for digit and wrist movements was nonsomatotopic and varied greatly between subjects. As an estimator of hand area size in primary motor cortex, we determined the smallest cuboid volume enclosing the five dipole sources within the left and right hemisphere of each subject. Interhemispheric comparison revealed a significant increase of this volume in primary motor cortex opposite to the preferred hand. This asymmetry was due to a greater spatial segregation of neuronal dipole generators subserving different hand and finger actions in the dominant hemisphere. Mean Euclidean distances between dipole sources for different movements were 10.7 ± 3.5 mm in the dominant and 9.4 ± 3.5 mm in the nondominant hemisphere (mean ± SD; P = 0.01, two-tailed t-test). The expansion of hand representation in primary motor cortex could not simply be attributed to a greater number of pyramidal cells devoted to each particular movement as inferred from current source amplitudes. The degree of hemispheric asymmetry of hand area size in the primary motor cortex was correlated highly with the asymmetry of hand performance in a standardized handedness test ( r = −0.76, P < 0.01). These results demonstrate for the first time a biological correlate of handedness in human motor cortex. The expansion of hand motor cortex in the dominant hemisphere may provide extra space for the cortical encoding of a greater motor skill repertoire of the preferred hand.
Spinal Cord Astrocytes Display a Switch From TTX-Sensitive to TTX-Resistant Sodium Currents After Injury-Induced Gliosis In Vitro
Authors: Macfarlane Stacey Nee , Sontheimer Harald
Published: December 2017

MacFarlane, Stacey Nee and Harald Sontheimer. Spinal cord astrocytes display a switch from TTX-sensitive to TTX-resistant sodium currents after injury-induced gliosis in vitro. J. Neurophysiol. 79: 2222–2226, 1998. Two distinct morphological subtypes of astrocytes have been shown to express Na+ currents that differ biophysically and pharmacologically. Using an in vitro model for reactive gliosis, we recently reported marked changes in Na+ and K+ channel expression by astrocytes induced to proliferate. Using this in vitro assay in which a confluent monolayer of astrocytes is mechanically scarred to induce gliosis, we now demonstrate that sodium currents of scar-associated cells, in addition to doubling in current density, also switch from being tetrodotoxin-sensitive(TTX-S, IC50 8 nM) to being ∼40-fold more TTX-resistant (TTX-R,IC50 314 nM). These changes occurred within 6 h after injury and were not associated with any notable changes in cell morphology. Changes in biophysical properties were analyzed for the two current types. The activation curve for TTX-R currents demonstrated a significant depolarized shift versus that of TTX-S currents ( P ≤ 0.003), and TTX-R currents have more depolarized V1/2 of activation (−33 vs. −23 mV). The V1/2 of inactivation was slightly, but not significantly, more depolarized for TTX-R currents as compared to TTX-S (−63 vs. −68 mV). Most notably, TTX-R currents showed significantly slower inactivation kinetics at depolarized voltage potentials than TTX-S sodium currents (0.76 vs. 1.128 ms, at −10 mV; P < 0.0004).
Painful Stimuli Evoke Potentials Recorded Over the Human Anterior Cingulate Gyrus
Authors: Lenz F. A. , Rios M. , Zirh A. , Chau D. , Krauss G. , Lesser R. P.
Published: December 2017

F. A. Lenz, M. Rios, A. Zirh, D. Chau, G. Krauss, and R. P. Lesser. Painful stimuli evoke potentials recorded over the human anterior cingulate gyrus. J. Neurophysiol. 79: 2231–2234, 1998. Clinical studies of cingulotomy patients and imaging studies predict that the human cingulate gyrus might display pain-related activity. We now report potentials evoked by painful cutaneous stimulation with a CO2 laser (LEP) and recorded from subdural electrodes over the medial wall of the hemisphere. In response to facial laser stimulation on both sides, a negative (latency 211–242 ms) and then a positive wave (325–352 ms) were recorded from the cortex of right medial wall and from the falcine dura overlying the left medial wall. Medial wall LEPs were similar to scalp LEPs and were largest over the anterior cingulate and superior frontal gyri just anterior to motor cortex contralateral to the side of stimulation. These results demonstrate that there is significant direct nociceptive input to the human anterior cingulate gyrus (Brodmann's area 24).
Thalamic Locus Mediates Hypoxic Inhibition of Breathing in Fetal Sheep
Authors: Koos Brian J. , Chau Andrew , Matsuura Masahiko , Punla Oscar , Kruger Lawrence
Published: December 2017

Koos, Brian J., Andrew Chau, Masahiko Matsuura, Oscar Punla, and Lawrence Kruger. Thalamic locus mediates hypoxic inhibition of breathing in fetal sheep. J. Neurophysiol. 79: 2383–2393, 1998. The effects of lesions rostral to the brain stem on breathing responses to hypoxia were determined in chronically catheterized fetal sheep (>0.8 term). These studies were designed to test the hypothesis that the diencephalon is involved in hypoxic inhibition of fetal breathing. As in normal fetuses, hypoxia inhibited breathing with transection rostral to the thalamus or transection resulting in virtual destruction of the thalamus but sparing most of the parafascicular nuclear complex. Neuronal lesions were produced in the fetal diencephalon by injecting ibotenic acid through cannulas implanted in the brain. Hypoxic inhibition of breathing was abolished when the lesions encompassed the parafascicular nuclear complex but was retained when the lesions spared the parafascicular nuclear region or when the vehicle alone was injected. A new locus has been identified immediately rostral to the midbrain, which is crucial to hypoxic inhibition of fetal breathing. This thalamic sector involves the parafascicular nuclear complex and may link central O2-sensing cells to motoneurons that inhibit breathing.
IID Sensitivity Differs Between Two Principal Centers in the Interaural Intensity Difference Pathway: the LSO and the IC
Authors: Park Thomas J.
Published: December 2017

Park, Thomas J. IID sensitivity differs between two principal centers in the interaural intensity difference pathway: the LOS and the IC. J. Neurophysiol. 79: 2416–2431, 1998. Interaural intensity differences (IIDs) are the chief cues that animals use to localize high-frequency sounds. Neurons that are sensitive to IIDs are excited by sound at one ear and inhibited by sound at the other. Thus a given IID generates a combination of excitation and inhibition that is reflected in a cell's spike count. In mammals, the so-called “IID pathway” begins in the lateral superior olive (LSO), which is dominated by the type of IID-sensitive neurons just described. The LSO then sends a prominent projection to the inferior colliculus (IC), which also contains a substantial population of IID-sensitive cells. Recent pharmacological studies have suggested that the response properties of IID-sensitive neurons in the IC undergo considerable processing and thus should not simply reflect the output of the LSO. However, we have no direct evidence as to whether IID sensitivity, the defining response feature of these cells, differs at these two levels. The present study makes this direct comparison in the Mexican free-tailed bat, a species that relies greatly on high-frequency hearing and thus on IIDs for localizing sounds in space. Extracellular recording techniques were used to obtain IID functions from 50 IC neurons. Comparable data from 50 LSO cells were available from a previous study. The main result was that IID sensitivity significantly differed between cells in the LSO and the IC. Among LSO cells, sensitivity was centered ∼0 dB (no intensity difference between the ears) whereas, in the IC, sensitivity was biased toward the inhibitory ear: on average, IC cells required a more intense signal at the inhibitory ear to reach the same degree of suppression as observed in LSO cells. Further analysis showed that the vast majority of IC cells (88%) exhibited a mismatch in the latencies of their inputs: inhibition arrived later when an equally strong excitation and inhibition were elicited; this reduced the effectiveness of the inhibition. Because latency shortens with increasing stimulus intensity, an IID with a more intense signal at the inhibitory ear could equate the latencies of excitation and inhibition, increasing the effectiveness of the inhibition. This result suggests that latency mismatches account, to a great extent, for the difference in sensitivity between the LSO and the IC; and when mismatches were negated by electronically time shifting the signals to the ears, sensitivity was no longer significantly different between the two nuclei.
Effects of Cerebellar Nuclear Inactivation on the Learning of a Complex Forelimb Movement in Cats
Authors: Wang Jian-Jun , Shimansky Yury , Bracha Vlastislav , Bloedel James R.
Published: December 2017

Wang, Jian-Jun, Yury Shimansky, Vlastislav Bracha, andJames R. Bloedel. Effects of cerebellar nuclear inactivation on thelearning of a complex forelimb movement in cats. J. Neurophysiol. 79: 2447–2459, 1998. The purpose of this study was to determine the effects of inactivating concurrently the cerebellar interposed and dentate nuclei on the capacity of cats to acquire and retain a complex, goal-directed forelimb movement. To assess the effects on acquisition, cats were required to learn to move a vertical manipulandum bar through a two-segment template with a shape approximating an inverted “L” after the injection of muscimol (saline for the control group) in the interposed and dentate cerebellar nuclei. During training periods, they were exposed progressively to more difficult templates, which were created by decreasing the angle between the two segments of the template. After determining the most difficult template the injected animals could learn within the specified time and performance constraints, the retraining phase of the experiment was initiated in which the cats were required to execute the same sequence of templates in the absence of any injection. This stage of the experiment assessed retention and determined the extent of any relearning required to execute the task at criterion levels. Next, the animals were overtrained without any injection on the most difficult template they could perform. Finally, to determine the effects of nuclear inactivation on retention after extensive retraining, their capacity to perform the same template was determined after muscimol injection in the interposed and dentate nuclei. The findings show that during the inactivation of the dentate and interposed nuclei the animals could learn to execute the more difficult templates. However, when required to execute the most difficult template learned under muscimol on the day after injections were discontinued, the cats had to “relearn” (reacquire) the movement. Finally, when the cerebellar nuclei were inactivated after the animals learned the task in the absence of any injections during the retraining phase, retention was not blocked. The data indicate that the intermediate and lateral cerebellum are not required either for learning this type of complex voluntary movement or for retaining the capacity to perform the task once it is learned. Nevertheless, when the cerebellum becomes available for executing a task learned in the absence of this structure, reacquisition of the behavior usually is necessary. It is hypothesized that the relearning observed after acquisition during muscimol inactivation reflects the tendency of the system to incorporate the cerebellum into the interactions responsible for the learning and performance of a motor sequence that is optimal for executing the task.
Neural Modulation of Gut Motility by Myomodulin Peptides and Acetylcholine in the SnailLymnaea
Authors: Perry Stephen J. , Straub Volko A. , Kemenes György , Santama Niovi , Worster Belinda M. , Burke Julian F. , Benjamin Paul R.
Published: December 2017

Perry, Stephen J., Volko A. Straub, György Kemenes, Niovi Santama, Belinda M. Worster, Julian F. Burke, and Paul R. Benjamin. Neural modulation of gut motility by myomodulin peptides and acetylcholine in the snail Lymnaea. J. Neurophysiol. 79: 2460–2474, 1998. Families of peptide neuromodulators are believed to play important roles in neural networks that control behaviors. Here, we investigate the expression and role of one such group of modulators, the myomodulins, in the feeding system of Lymnaea stagnalis. Using a combination of in situ hybridization and antibody staining, expression of the myomodulin gene was confirmed in a number of identified behaviorally significant neuronal types, including the paired B2 motor neurons. The B2 cells were shown to project axons to the proesophagus, where they modulate foregut contractile activity. The presence of the five myomodulin peptide structures was confirmed in the B2 cells, the proesophagus, and the intervening nerve by mass spectrometry. Using a sensitive cell culture assay, evidence that the B2 cells are cholinergic also is presented. Application of four of the five myomodulin peptides to the isolated foregut increased both contraction frequency and tonus, whereas the main effect of acetylcholine (ACh) application was a large tonal contraction. The fifth myomodulin peptide (pQIPMLRLamide) appeared to have little or no effect on gut motility. Coapplication of all five myomodulin peptides gave a greater increase in tonus than that produced by the peptides applied individually, suggesting that corelease of the peptides onto the gut would produce an enhanced response. The combined effects that the myomodulin peptides and ACh have on foregut motility can mimic the main actions of B2 cell stimulation.
Responses of Neurons in the Insular Cortex to Gustatory, Visceral, and Nociceptive Stimuli in Rats
Authors: Hanamori Takamitsu , Kunitake Takato , Kato Kazuo , Kannan Hiroshi
Published: December 2017

Hanamori, Takamitsu, Takato Kunitake, Kazuo Kato, and Hiroshi Kannan. Responses of neurons in the insular cortex to gustatory, visceral, and nociceptive stimuli in rats. J. Neurophysiol. 79: 2535–2545, 1998. Extracellular unit responses to baroreceptor and chemoreceptor stimulation, gustatory stimulation of the posterior tongue, electrical stimulation of the superior laryngeal (SL) nerve, and tail pinch were recorded from the insular cortex of anesthetized and paralyzed rats. Forty-three neurons identified responded to stimulation by at least one of the stimuli used in the present study. Of the 43 neurons, 33 responded to tail pinch, and the remaining 10 had no response; 18 showed an excitatory response, and 15 showed an inhibitory response. Of the 43 neurons, 35 responded to electrical stimulation of the SL nerve; 27 showed an excitatory response, and 8 showed an inhibitory response. Of the 20 neurons that responded to baroreceptor stimulation by an intravenous injection of methoxamine hydrochloride (Mex), 11 were excitatory and 9 were inhibitory. Twenty-seven neurons were responsive to an intravenous injection of sodium nitroprusside (SNP); 10 were excitatory and 17 were inhibitory. Ten neurons were excited and 16 neurons were inhibited by arterial chemoreceptor stimulation by an intravenous injection of sodium cyanide (NaCN). Twenty-six neurons were responsive to at least one of the gustatory stimuli (1.0 M NaCl, 30 mM HCl, 30 mM quinine HCl, and 1.0 M sucrose): four to six excitatory neurons and three to nine inhibitory neurons for each stimulus. A large number of the neurons (42/43) received convergent inputs from more than one stimulus among the nine stimuli used in the present study. Most neurons (38/43) were responsive to two or more stimulus groups when the natural stimuli used in the present study are grouped into three, gustatory, visceral, and nociceptive stimuli. The neurons recorded were located in the insular cortex between 2.8 mm anterior and 1.1 mm posterior to the anterior edge of the joining of the anterior commissure (AC); the mean location was 1.0 mm ( n = 43) anterior to the AC. This indicates that most of the neurons identified in the present study were located in the region posterior to the taste area and anterior to the visceral area in the insular cortex. These results indicate that the insular cortex neurons distributing between the taste area and the visceral area receive convergent inputs from baroreceptor, chemoreceptor, gustatory, and nociceptive organs and may have roles in taste aversion or in regulation of visceral responses.
Processing of Frequency-Modulated Sounds in the Cat's Posterior Auditory Field
Authors: Tian Biao , Rauschecker Josef P.
Published: December 2017

Tian, Biao and Josef P. Rauschecker. Processing of frequency-modulated sounds in the cat's posterior auditory field. J. Neurophysiol. 79: 2629–2642, 1998. Single-neuron activity was recorded from the posterior auditory field (PAF) in the cortex of gas-anesthetized cats. Tone bursts and broadband complex sounds were used for auditory stimulation. Responses to frequency-modulated (FM) sounds, in particular, were studied systematically. Linear FM sweeps were centered around the best frequency (BF) of a neuron and had an excursion large enough to cover its whole frequency tuning range. Rate and direction of change of the FM sweeps were varied. In the majority of PAF neurons (75%) the FM response seemed not to be linear, i.e., their best instantaneous frequency (BIF) varied by more than one octave at different FM rates (FMR). When the difference between BIF and BF at each FMR was used as a measure of linearity, it was within one-third octave only at five or fewer FMR in most PAF neurons (74%). The majority of PAF neurons (70%) preferred moderate FM rates (<200 Hz/ms). Fifty-four percent of all neurons in this area showed band-pass behavior with a clear preference in the middle range of FM rates in at least one direction. Overall, neurons with high-pass behavior in both directions made up only a minor portion (22%) of PAF neurons. When both directions of an FM sweep (low-to-high and high-to-low frequency) were tested, 50% of the neurons were clearly selective for one direction, i.e., the response to one FM direction was at least twice as large as that to the other direction. This selectivity was not necessarily present at the preferred FM rate. In general, FM direction selectivity was equally distributed over FM rates tested. The selectivity of PAF neurons for the rate and direction of FM sounds makes these neurons suitable for the detection and analysis of communication sounds, which often contain FM components with a moderate sweep rate in a particular direction.
Minimal Model of Oscillations and Waves in theLimaxOlfactory Lobe With Tests of the Model's Predictive Power
Authors: Ermentrout Bard , Flores Jorge , Gelperin Alan
Published: December 2017

Ermentrout, Bard, Jorge Flores, and Alan Gelperin. Minimal model of oscillations and waves in the Limax olfactory lobe with tests of the model's predictive power. J. Neurophysiol. 79: 2677–2689, 1998. Propagating waves are observed in the olfactory or procerebral (PC) lobe of the terrestrial mollusk, Limax maximus. Wave propagation is altered by cutting through the various layers of the PC lobe both parallel and transverse to the direction of wave propagation. We present a model for the PC lobe based on two layers of coupled cells. The top layer represents the cell layer of the PC lobe, and the bottom layer corresponds to the neuropil of the PC lobe. To get wave propagation, we induce a coupling gradient so that the most apical cells receive a greater input from neighbors than the basal cells. The top layer in the model is composed of oscillators coupled locally, whereas the bottom layer is comprised of oscillators with global coupling. Odor stimulation is represented by an increase in the strength of coupling between the two layers. This model allows us to explain a number of experimental observations: 1) the intact PC lobe exhibits regular propagating waves, which travel from the apical to the basal end; 2) there is a gradient in the local frequency of slices cut transverse to the axis of wave propagation, with apical slices oscillating faster than basal slices; 3) with partial cuts through the cell layer or the neuropil layer, the apical and basal ends remain tightly coupled; 4) removal of the neuropil layer does not prevent wave propagation in the cell layer; 5) odor stimulation causes the waves to collapse and the cells in the PC lobe oscillate synchronously; and 6) by allowing a single parameter to vary in the model, we capture the reversal of waves in low chloride medium.
Control of Spatial Orientation of the Angular Vestibuloocular Reflex by the Nodulus and Uvula
Authors: Wearne Susan , Raphan Theodore , Cohen Bernard
Published: December 2017

Wearne, Susan, Theodore Raphan, and Bernard Cohen. Control of spatial orientation of the angular vestibuloocular reflex by the nodulus and uvula. J. Neurophysiol. 79: 2690–2715, 1998. Spatial orientation of the angular vestibuloocular reflex (aVOR) was studied in rhesus monkeys after complete and partial ablation of the nodulus and ventral uvula. Horizontal, vertical, and torsional components of slow phases of nystagmus were analyzed to determine the axes of eye rotation, the time constants (Tcs) of velocity storage, and its orientation vectors. The gravito-inertial acceleration vector (GIA) was tilted relative to the head during optokinetic afternystagmus (OKAN), centrifugation, and reorientation of the head during postrotatory nystagmus. When the GIA was tilted relative to the head in normal animals, horizontal Tcs decreased, vertical and/or roll time constants (Tcvert/roll) lengthened according to the orientation of the GIA, and vertical and/or roll eye velocity components appeared (cross-coupling). This shifted the axis of eye rotation toward alignment with the tilted GIA. Horizontal and vertical/roll Tcs varied inversely, with Tchorbeing longest and Tcvert/rollshortest when monkeys were upright, and the reverse when stimuli were around the vertical or roll axes. Vertical or roll Tcs were longest when the axes of eye rotation were aligned with the spatial vertical, respectively. After complete nodulo-uvulectomy, Tchorbecame longer, and periodic alternating nystagmus (PAN) developed in darkness. Tchorcould not be shortened in any of paradigms tested. In addition, yaw-to-vertical/roll cross-coupling was lost, and the axes of eye rotation remained fixed during nystagmus, regardless of the tilt of the GIA with respect to the head. After central portions of the nodulus and uvula were ablated, leaving lateral portions of the nodulus intact, yaw-to-vertical/roll cross-coupling and control of Tcvert/rollwas lost or greatly reduced. However, control of Tchorwas maintained, and Tchorcontinued to vary as a function of the tilted GIA. Despite this, the eye velocity vector remained aligned with the head during yaw axis stimulation after partial nodulo-uvulectomy, regardless of GIA orientation to the head. The data were related to a three-dimensional model of the aVOR, which simulated the experimental results. The model provides a basis for understanding how the nodulus and uvula control processing within the vestibular nuclei responsible for spatial orientation of the aVOR. We conclude that the three-dimensional dynamics of the velocity storage system are determined in the nodulus and ventral uvula. We propose that the horizontal and vertical/roll Tcs are separately controlled in the nodulus and uvula with the dynamic characteristics of vertical/roll components modulated in central portions and the horizontal components laterally, presumably in a semicircular canal-based coordinate frame.