bluuebunny/crossref_metadata_2025 huggingface dataset:
Circuitry Underlying AntiOpioid Actions of Orphanin FQ in the Rostral Ventromedial Medulla
Authors: Heinricher M. M. , McGaraughty S. , Grandy D. K.
Published: December 2017

Heinricher, M. M., S. McGaraughty, and D. K. Grandy. Circuitry underlying antiopioid actions of orphanin FQ in the rostral ventromedial medulla. J. Neurophysiol. 78: 3351–3358, 1997. Several laboratories recently identified a 17 amino-acid peptide, termed “nociceptin” or “orphanin FQ (OFQ)”, as the endogenous ligand for the LC132 (or “opioid receptor-like1”) receptor. Taken together with the fact that the cellular effects of OFQ are to a large extent opioid-like, the close relationship between the LC132 receptor and known opioid receptors raised expectations that the behavioral effects of this peptide would resemble those of opioids. However studies of the role of OFQ in nociception have not provided a unified view. The aim of the present study was to use a combination of electrophysiological and pharmacological techniques to characterize the actions of OFQ in a brain region in which the circuitry mediating the analgesic actions of opioids has been relatively well characterized, the rostral ventromedial medulla (RVM). Single-cell recording was combined with opioid administration and local infusion of OFQ in the RVM of rats lightlyanesthetized with barbiturates. The tail flick reflex was used as a behavioral index of nociceptive responsiveness. Two classes of physiologically identifiable RVM neurons with distinct responses to opioids have been characterized. off-cells are activated, although indirectly, by opioids, and there is strong evidence that this activation is crucial to opioid antinociception. on-cells, thought to enable nociception, are directly inhibited by opioids. Cells of a third class, neutral cells, do not respond to opioids and whether or not they have any role in nociceptive modulation remains an open question. OFQ infused within the RVM profoundly suppressed the firing of all classes of RVM neurons, blocking opioid-induced activation of off-cells. The antinociceptive effects of a μ-opioid agonist infused at the same site were significantly attenuated in these animals. Those of systemically administered morphine, which can produce its antinociceptive effects by acting at a number of CNS sites, were not blocked by RVM OFQ. Inasmuch as activation of off-cells can account for the antinociceptive action of opioids within the RVM, these results demonstrate that, at least within the medulla, OFQ can exert a functional “antiopioid” effect by suppressing firing of this cell class. However to the extent that antinociceptive and pronociceptive outflows from various brain regions involved in both transmission and modulation of nociception are active under different conditions, focal application of OFQ in different regions could potentially produce either hypalgesia or hyperalgesia.
Glutamatergic N2v Cells Are Central Pattern Generator Interneurons of theLymnaeaFeeding System: New Model for Rhythm Generation
Authors: Brierley M. J. , Yeoman M. S. , Benjamin P. R.
Published: December 2017

Brierley, M. J., M. S. Yeoman, and P. R. Benjamin. Glutamatergic N2v cells are central pattern generator interneurons of the Lymnaea feeding system: new model for rhythm generation. J. Neurophysiol. 78: 3396–3407, 1997. We aimed to show that the paired N2v (N2 ventral) plateauing cells of the buccal ganglia are important central pattern generator (CPG) interneurons of the Lymnaea feeding system. N2v plateauing is phase-locked to the rest of the CPG network in a slow oscillator (SO)-driven fictive feeding rhythm. The phase of the rhythm is reset by artificially evoked N2v bursts, a characteristic of CPG neurons. N2v cells have extensive input and output synaptic connections with the rest of the CPG network and the modulatory SO cell and cerebral giant cells (CGCs). Synaptic input from the protraction phase interneurons N1M (excitatory), N1L (inhibitory), and SO (inhibitory-excitatory) are likely to contribute to a ramp-shaped prepotential that triggers the N2v plateau. The prepotential has a highly complex waveform due to progressive changes in the amplitude of the component synaptic potentials. Most significant is the facilitation of the excitatory component of the SO → N2v monosynaptic connection. None of the other CPG interneurons has the appropriate input synaptic connections to terminate the N2v plateaus. The modulatory function of acetylcholine (ACh), the transmitter of the SO and N1M/N1Ls, was examined. Focal application of ACh (50-ms pulses) onto the N2v cells reproduced the SO → N2v biphasic synaptic response but also induced long-term plateauing (20–60 s). N2d cells show no endogenous ability to plateau, but this can be induced by focal applications of ACh. The N2v cells inhibit the N3 tonic (N3t) but not the N3 phasic (N3p) CPG interneurons. The N2v → N3t inhibitory synaptic connection is important in timing N3t activity. The N3t cells recover from this inhibition and fire during the swallow phase of the feeding pattern. Feedback N2v inhibition to the SO, N1L protraction phase interneurons prevents them firing during the retraction phase of the feeding cycle. The N2v → N1M synaptic connection was weak and only found in 50% of preparations. A weak N2v → CGC inhibitory connection prevents the CGCs firing during the rasp (N2) phase of the feeding cycle. These data allowed a new model for the Lymnaea feeding CPG to be proposed. This emphasizes that each of the six types of CPG interneuron has a unique set of synaptic connections, all of which contribute to the generation of a full CPG pattern.
Glutamate is the Transmitter for N2v Retraction Phase Interneurons of theLymnaeaFeeding System
Authors: Brierley M. J. , Yeoman M. S. , Benjamin P. R.
Published: December 2017

Brierley, Matthew J., Mark S. Yeoman, and Paul R. Benjamin. Glutamate is the transmitter for the N2v retraction phase interneurons of the Lymnaea feeding system. J. Neurophysiol. 78: 3408–3414, 1997. Electrophysiological and pharmacological methods were used to examine the role of glutamate in mediating the excitatory and inhibitory responses produced by the N2v rasp phase neurons on postsynaptic cells of the Lymnaea feeding network. The N2v → B3 motor neuron excitatory synaptic response could be mimicked by focal or bath application of l-glutamate at concentrations of ≥10−3M. Quisqualate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) were potent agonists for the B3 excitatory glutamate receptor (10−3M), whereas kainate only produced very weak responses at the same concentration. This suggested that non- N-methyl-d-aspartate (NMDA), AMPA/quisqualate receptors were present on the B3 cell. The specific non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10−5M) blocked 85% of the excitatory effects on the B3 cell produced by focal application of glutamate (10−3M), confirming the presence of non-NMDA receptors. CNQX also blocked the major part of the excitatory postsynaptic potentials on the B3 cell produced by spontaneous or current-evoked bursts of spikes in the N2v cell. As with focal application of glutamate, a small delayed component remained that was CNQX insensitive. This provided direct evidence that glutamate acting via receptors of the non-NMDA, AMPA/quisqualate type were responsible for mediating the main N2v → B3 cell excitatory response. NMDA at 10−2M also excited the B3 cell, but the effects were much more variable in size and absent in one-third of the 25 B3 cells tested. NMDA effects on B3 cells were not enhanced by bath application of glycine at 10−4M or reduction of Mg2+concentration in the saline to zero, suggesting the absence of typical NMDA receptors. The variability of the B3 cell responses to NMDA suggested these receptors were unlikely to be the main receptor type involved with N2v → B3 excitation. Quisqualate and AMPA at 10−3M also mimicked N2v inhibitory effects on the B7 and B8 feeding motor neurons and the modulatory slow oscillator (SO) interneuron, providing further evidence for the role of AMPA/quisqualate receptors. Similar effects were seen with glutamate at the same concentration. However, CNQX could not block either glutamate or N2v inhibitory postsynaptic responses on the B7, B8, or SO cells, suggesting a different glutamate receptor subtype for inhibitory responses compared with those responsible for N2v → B3 excitation. We conclude that glutamate is a strong candidate transmitter for the N2v cells and that AMPA/quisquate receptors of different subtypes are likely to be responsible for the excitatory and inhibitory postsynaptic responses.
Receptive Field Changes After Strokelike Cortical Ablation: A Role for Activation Dynamics
Authors: Sober Samuel J. , Stark Jeanne M. , Yamasaki Dwayne S. , Lytton William W.
Published: December 2017

Sober, Samuel J., Jeanne M. Stark, Dwayne S. Yamasaki, and William W. Lytton. Receptive field changes after strokelike cortical ablation: a role for activation dynamics. J. Neurophysiol. 78: 3438–3443, 1997. The reorganization of neural activity that takes place after stroke is of paramount importance in producing functional recovery. Experimental stroke models have suggested that this reorganization may have two phases, but physiology alone cannot fully resolve what causes each phase. Computer modeling suggests that these phases might involve an initial change in dynamics occurring immediately, followed by synaptic plasticity. We combined physiological recording from macaque middle temporal cortex (area MT) with a neural network computer model to examine this first phase of altered cortical function after a small, experimentally induced cortical lesion. Major receptive field (RF) changes seen in the first few days postlesion included both expansion and contraction of receptive fields. Although only expansion could be reproduced in an initial model, addition of inhibitory interneuron loss in a ring around the primary ablation, suggested by immunohistochemical examination, permitted contraction to be replicated as well. We therefore predict that this immunochemical observation reflects an immediate extension of the lesion rather than a late response. Additionally our model successfully predicted a correlation between increased firing rate and RF size. Our model suggests that activation dynamics alone, without anatomic remodeling, can cause the large receptive field changes that allow the rapid behavioral recovery seen after middle temporal lesions.
Frequency-Dependent Information Flow From the Entorhinal Cortex to the Hippocampus
Authors: Gloveli Tengis , Schmitz Dietmar , Empson Ruth M. , Heinemann Uwe
Published: December 2017

Gloveli, Tengis, Dietmar Schmitz, Ruth M. Empson, and Uwe Heinemann. Frequency-dependent information flow from the entorhinal cortex to the hippocampus. J. Neurophysiol. 78: 3444–3449, 1997. Storage and retrieval of information in the hippocampus is dependent on information transfer from the entorhinal cortex (EC). We studied how the separate pathways from layer II and III of the EC to the hippocampus are selected for information transfer during repetitive synaptic stimulation. Intracellular recordings were made from EC layer II and III projection cells in horizontal combined EC-hippocampal slices. Synaptic responses to stimulation of deep layers or the lateral EC with stimulus intensities ∼70% of that required to elicit an action potential were analyzed during short trains of repetitive stimulation. The threshold intensities for induction of action potentials were in layer II cells 8.2 ± 3.8 (SE) V, significantly larger than 4.4 ± 1.5 V in type 1, and 5.2 ± 3.3 V in type 2 layer III cells, respectively. During repetitive subthreshold stimulation with frequencies below 5 Hz the pathway from the EC layer II remained quiet and was preferentially activated with stimulation frequencies above 5 Hz. In contrast the EC layer III cells responded preferentially to low stimulus frequencies (<10 Hz) and became strongly inhibited when synaptically stimulated with frequencies above 10 Hz. Interestingly during stimulus frequencies between 5 and 10 Hz the likelihood that both layer II and III cells fire was large. Thus a frequency switch operates in the entrohinal cortex regulating output of layer II and III cells to the hippocampus. We suggest that such frequency dependent regulation of information flow presents a new principle of neuronal information processing.
On the Detection and Measurement of Synchrony in Neural Populations by Coherence Analysis
Authors: Christakos Constantinos N.
Published: December 2017

Christakos, Constantinos N. On the detection and measurement of synchrony in large neural populations by coherence analysis. J. Neurophysiol. 78: 3453–3459, 1997. This study considers the possibility of using coherence analysis for detection and measurement of synchrony (correlations) in large neural populations, applied to activities that are relatively easy to record in parallel. Mathematical analysis and computer simulations are used to examine the behavior of the coherence function between both unitary and population-aggregate activity (UTA coherence) and the aggregate activities of two populations (ATA coherence). The results indicate that for a large population showing partial correlations, the UTA coherence function is almost zero at all frequencies for the uncorrelated units. However, unless the synchrony is very restricted, its value is nonzero (i.e., statistically significant by common criteria) at each frequency of synchrony for the units that show correlations to other units. Moreover, this value is indicative of the strength of synchrony for any given unit. These properties enable the identification of the correlated units in a sample of unit/population activities simultaneously recorded in a series of experiments, and hence the detection of synchrony. The extent of synchrony can then be estimated as the fraction of such units in the sample, whereas the values of the UTA coherences in the sample can be used to estimate the strength and its distribution within the population. Similarly, the ATA coherence function is generally nonzero (significant) at the frequencies where there are correlations between members of two large populations. This enables the easy detection of such correlations from simultaneously recorded population activities. However, this function is a very sensitive index of synchrony and even shows saturation effects. It may therefore be used as a general measure of synchrony only under restricted conditions.
Time-Dependent Changes in Excitability After One-Trial Conditioning of Hermissenda
Authors: Crow Terry , Siddiqi Vilma
Published: December 2017

Crow, Terry and Vilma Siddiqi. Time-dependent changes in excitability after one-trial conditioning of Hermissenda. J. Neurophysiol. 78: 3460–3464, 1997. The visual system of Hermissenda has been studied extensively as a site of cellular plasticity produced by classical conditioning. A one-trial conditioning procedure consisting of light paired with the application of serotonin (5-HT) to the exposed, but otherwise intact, nervous system produces suppression of phototactic behavior tested 24 h after conditioning. Short- and long-term enhancement (STE and LTE) of excitability in identified type B photoreceptors is a cellular correlate of one-trial conditioning. LTE can be expressed in the absence of STE suggesting that STE and LTE may be parallel processes. To examine the development of enhancement, we studied its time-dependent alterations after one-trial conditioning. Intracellular recordings from identified type B photoreceptors of independent groups collected at different times after conditioning revealed that enhanced excitability follows a biphasic pattern in its development. The analysis of spikes elicited by 2 and 30 s extrinsic current pulses at different levels of depolarization showed that enhancement reached a peak 3 h after conditioning. From its peak, excitability decreased toward baseline control levels 5–6 h after conditioning followed by an increase to a stable plateau at 16 to 24 h postconditioning. Excitability changes measured in cells from unpaired control groups showed maximal changes 1 h posttreatment that rapidly decremented within 2 h. The conditioned stimulus (CS) elicited significantly more spikes 24 h postconditioning for the conditioned group as compared with the unpaired control group. The analysis of the time-dependent development of enhancement may reveal the processes underlying different stages of memory for this associative experience.
Contribution of Auditory Cortex to Acoustical Orientation in Cats Under Conditions of Discordant Auditory Reafference
Authors: Beitel Ralph E.
Published: December 2017

Beitel, Ralph E. Contribution of auditory cortex to acoustical orientation in cats under conditions of discordant auditory reafference. J. Neurophysiol. 78: 3468–3474, 1997. Head-orienting responses (ORs) evoked by a stationary source of sound typically terminate in small undershoots in normal hearing cats or in large undershoots (hypometria) if the auditory cortex is ablated bilaterally. In the present study, ORs executed by cats were studied using a procedure in which the OR produced an isogonal rotation of the sound source, i.e., response-produced change (reafference) in the acoustic stimulus was distorted. Under this condition (discordant auditory reafference), ORs terminated in large overshoots (hypermetria) in the normal hearing cats. This result indicates that experimental distortion of response-produced auditory feedback resulted in an “on-line” modification of ORs by the normal hearing cats. In the cats with auditory cortex ablated, ORs terminated in large undershoots (hypometria), suggesting that auditory cortex is a necessary component of the central auditory system for processing reafferent acoustic stimuli that normally occur during head rotation in a sound field.
PET Study of Pointing With Visual Feedback of Moving Hands
Authors: Inoue Kentaro , Kawashima Ryuta , Satoh Kazunori , Kinomura Shigeo , Goto Ryoi , Koyama Masamichi , Sugiura Motoaki , Ito Masatoshi , Fukuda Hiroshi
Published: December 2017

Inoue, Kentaro, Ryuta Kawashima, Kazunori Satoh, Shigeo Kinomura, Ryoi Goto, Masamichi Koyama, Motoaki Sugiura, Masatoshi Ito, and Hiroshi Fukuda. PET study of pointing with visual feedback of moving hands. J. Neurophysiol. 79: 117–125, 1998. This study was conducted to determine where in the human brain visual feedback of hand movements is processed to allow accurate pointing. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) and H2 15O in nine normal volunteers while performing one control and two reaching tasks. In all tasks, visual stimuli were presented on a head mounted display (HMD). A target board was placed in front of the subjects bearing six red light-emitting diodes (LEDs) aligned on a circle with a green LED at its center. The center green LED and one of the six red LEDs, randomly selected, were repeatedly switched on and off, alternatively. In the control task, subjects were instructed to gaze at the lit LED. In the two reaching tasks, the reaching with visual feedback (RwithF) task and the reaching without visual feedback (RwithoutF) task, they had to point to the lit red LED with their right index fingers. In the RwithF task, their right hands were visible on the HMD before touching the target, whereas in the RwithoutF task, they were not visible. For each subject, subtraction images of each reaching task minus the control and the RwithF task minus the RwithoutF task were calculated after transformation of PET images into the standard brain shape with an adjustable computerized brain atlas. These subtraction rCBF images were then averaged among the subjects, and significant changes of rCBF were identified. Significant increases in rCBF not only in the RwithF task minus control image but also in the RwithF task minus the RwithoutF task image were observed in the supramarginal cortex, the premotor cortex and the posterior cingulate cortex of the left hemisphere, the caudate nucleus and the thalamus of the right hemisphere, and the right cerebellum and vermis. These results indicate that the supramarginal cortex, the premotor cortex, and the posterior cingulate cortex of the left hemisphere and the cerebellum are involved in integrating visual feedback of hand movements and execution of accurate pointing.
Abnormal Synaptic Transmission in the Olfactory Bulb of Fyn-Kinase–Deficient Mice
Authors: Kitazawa Hiromasa , Yagi Takeshi , Miyakawa Tsuyoshi , Niki Hiroaki , Kawai Nobufumi
Published: December 2017

Kitazawa, Hiromasa, Takeshi Yagi, Tsuyoshi Miyakawa, Hiroaki Niki, and Nobufumi Kawai. Abnormal synaptic transmission in the olfactory bulb of Fyn-kinase–deficient mice. J. Neurophysiol. 79: 137–142, 1998. We studied synaptic transmission in the granule cells in the olfactory bulb of the homozygous Fyn (a nonreceptor type tyrosine kinase)-deficient ( fyn z/ fyn z) and heterozygous Fyn-deficient (+/ fyn z) mice by using slice preparations from the olfactory bulb. Stimulation to the lateral olfactory tract and/or centrifugal fibers to the olfactory bulb evoked field excitatory postsynaptic potentials (fEPSPs) in the granule cells. In +/ fyn z mice, fEPSPs were augmented by bicuculline, a γ-aminobutyric acid (GABAA) antagonist and picrotoxin, whereas fEPSPs in fyn z/ fyn z mice were much less sensitive to bicuculline and picrotoxin. Application of d-2-amino-5-phosphonopentanoic acid had no effect but 6-cyano-7-nitroquinoxaline-2,3-dione produced almost complete block of fEPSPs in both +/ fyn z mice and fyn z/ fyn z mice. (1S, 3R)-1-aminocyclo-pentane-1.3-dicarboxylate, an agonist of metabotropic glutamate receptors caused a similar depression of fEPSPs in both +/ fyn z and fyn z/ fyn z mice. In +/ fyn z mice tetanic stimulation to the lateral olfactory tract and/or centrifugal fibers induced N-methyl-d-aspartate (NMDA)-dependent long-term potentiation (LTP) of fEPSPs, whereas LTP was impaired in fyn z/ fyn z mice. Our results demonstrate altered functions of GABAA and NMDA receptors in the olfactory system of Fyn-deficient mice.
Neural Discharge and Local Field Potential Oscillations in Primate Motor Cortex During Voluntary Movements
Authors: Donoghue John P. , Sanes Jerome N. , Hatsopoulos Nicholas G. , Gaál Gyöngyi
Published: December 2017

Donoghue, John P., Jerome N. Sanes, Nicholas G. Hatsopoulos, and Gyöngyi Gaál. Neural discharge and local field potential oscillations in primate motor cortex during voluntary movements. J. Neurophysiol. 79: 159–173, 1998. The role of “fast,” or gamma band (20–80 Hz), local field potential (LFP) oscillations in representing neuronal activity and in encoding motor behavior was examined in motor cortex of two alert monkeys. Using chronically implanted microwires, we simultaneously recorded LFPs and single or multiple unit (MU) discharge at a group of sites in the precentral gyrus during trained finger force or reaching movements, during natural reaching and grasping, and during quiet sitting. We evaluated the coupling of oscillations with task-related firing at the same site, the timing of oscillations with respect to the execution of trained and untrained movement, and the temporal synchrony of oscillations across motor cortical sites. LFPs and neural discharge were examined from a total of 16 arm sites (7 sites in 1 monkey and 9 in the other), each showing movement-related discharge modulation and arm microstimulation effects. In the trained tasks, fast LFP and MU oscillations occurred most often during a premovement delay period, ceasing around movement onset. The decrease in oscillation roughly coincided with the appearance of firing rate modulation coupled to the motor action. During this delay, LFP oscillations exhibited either “overlapping” or “mixed” relationships with the simultaneously recorded neural discharge at that site. Overlap was characterized by coincident epochs of increased neural discharge and LFP oscillations. For the mixed pattern, episodes of LFP oscillation typically coincided with periods of diminished firing but overlap also sometimes appeared. Both patterns occurred concurrently across motor cortex during preparation; LFP suppression with motor action was ubiquitous. Fast oscillations reappeared quickly upon transition from quiet sitting to resumption of task performance, indicating an association with task engagement, rather than the general motor inaction of the delay period. In contrast to trained movements, fast oscillations often appeared along with movement during untrained reaching, but oscillations occurred erratically and were not reliably correlated with elevated neural discharge. Synchronous oscillations occurred at sites as much as 5 mm apart, suggesting widespread coupling of neurons and LFP signals in motor cortex. Widespread coupling of oscillatory signals is consistent with the concept that temporal coding processes operate in motor cortex. However, because the relationship between neuronal discharge and the appearance of fast oscillations may be altered by behavioral condition, they must reflect a global process active in conjunction with motor planning or preparatory functions, but not details of motor action encoded in neuronal firing rate.
Monkey Prefrontal Neuronal Activity Coding the Forthcoming Saccade in an Oculomotor Delayed Matching-to-Sample Task
Authors: Hasegawa Ryohei , Sawaguchi Toshiyuki , Kubota Kisou
Published: December 2017

Hasegawa, Ryohei, Toshiyuki Sawaguchi, and Kisou Kubota. Monkey prefrontal neuronal activity coding the forthcoming saccade in an oculomotor delayed matching-to-sample task. J. Neurophysiol. 79: 322–333, 1998. To determine the role of the dorsolateral prefrontal cortex (PFC) in the selection of memory-guided saccadic eye movements, we recorded the activities of PFC neurons while macaque monkeys performed an oculomotor delayed matching-to-sample task. The task was designed to dissociate motor factors from visual factors in the selection and retention of the direction of the forthcoming saccade during delay periods after the visual cue but before the GO signal was presented. While the monkey fixated on a central fixation spot (FX period, 1 s), a sample cue (1 of 4 geometric figures) and a matching cue composed of two geometric figures were presented in succession (SC and MC periods, respectively, 0.5 s) with a brief delay (D1 period, 1 or 1.5 s). After another delay (D2 period, 1.5 s), the monkey made a saccade (GO period, <0.5 s) toward one of four locations (the goal) that had been indicated by the combination of the sample and matching cues in the MC period. We recorded the activities of 224 neurons in the periprincipal sulcal area of 3 hemispheres of 2 monkeys. Sixty-five neurons (29%) showed a significant increase in activity during the D2 period. Some of these also responded during other phases of the task (SC period, n = 32; D1, 22; MC, 53; GO, 47). Some of the activity during the D2(52/65, 80%) and GO (40/47, 85%) periods was associated with the direction of the forthcoming saccade (“direction selective”). Although most MC-period activities of D2 neurons were direction selective (38/53, 73%), a fraction of them (14/38) was also affected by both saccade direction and matching cue pattern. To compare quantitatively the contribution of motor (saccade direction) and visual (matching-cue pattern) factors to the activity of D2 neurons, we calculated directional and visual dependency indices (DDI and VDI) for each of the three periods (MC, D2, and GO). In both the D2 and GO periods, D2 neurons with high DDI values and low VDI values predominated. In the MC period, however, there was no significant difference between the distributions of DDI and VDI values. These findings suggest that PFC neurons store the direction of memory-guided saccades during a delay period before eye movement and that the same neurons may be involved in the decision-making process that underlies the selection of the saccade direction during the MC period.
Coupling of Efferent Neuromodulatory Neurons to Rhythmical Leg Motor Activity in the Locust
Authors: Baudoux Sylvie , Duch Carsten , Morris Oliver T.
Published: December 2017

Baudoux, Sylvie, Carsten Duch, and Oliver T. Morris. Coupling of efferent neuromodulatory neurons to rhythmical leg motor activity in the locust. J. Neurophysiol. 79: 361–370, 1998. The spike activity of neuromodulatory dorsal unpaired median (DUM) neurons was analyzed during a pilocarpine-induced motor pattern in the locust. Paired intracellular recordings were made from these octopaminergic neurons during rhythmic activity in hindleg motor neurons evoked by applying pilocarpine to an isolated metathoracic ganglion. This motor pattern is characterized by two alternating phases: a levator phase, during which levator, flexor, and common inhibitor motor neurons spike, and a depressor phase, during which depressor and extensor motor neurons spike. Three different subpopulations of efferent DUM neurons could be distinguished during this rhythmical motor pattern according to their characteristic spike output. DUM 1 neurons, which in the intact animal do not innervate muscles involved in leg movements, showed no change apart from a general increase in spike frequency. DUM 3 and DUM 3,4 neurons produced the most variable activity but received frequent and sometimes pronounced hyperpolarizations that were often common to both recorded neurons. DUM 5 and DUM 3,4,5 neurons innervate muscles of the hindleg and showed rhythmical excitation leading to bursts of spikes during rhythmic activity of the motor neurons, which innervate these same muscles. Sometimes the motor output was coordinated across both sides of the ganglion so that there was alternating activity between levators of both sides. In these cases, the spikes of DUM 5 and DUM 3,4,5 neurons and the hyperpolarization of DUM 3 and DUM 3,4 neurons occurred at particular phases in the motor pattern. Our data demonstrate a central coupling of specific types of DUM neurons to a rhythmical motor pattern. Changes in the spike output of these particular efferent DUM neurons parallel changes in the motor output. The spike activity of DUM neurons thus may be controlled by the same circuits that determine the action of the motor neurons. Functional implications for real walking are discussed.
Changes in Intracellular Ca2+ Induced by GABAA Receptor Activation and Reduction in Cl− Gradient in Neonatal Rat Neocortex
Authors: Fukuda Atsuo , Muramatsu Kanji , Okabe Akihito , Shimano Yasunobu , Hida Hideki , Fujimoto Ichiro , Nishino Hitoo
Published: December 2017

Fukuda, Atsuo, Kanji Muramatsu, Akihito Okabe, Yasunobu Shimano, Hideki Hida, Ichiro Fujimoto, and Hitoo Nishino. Changes in intracellular Ca2+ induced by GABAA receptor activation and reduction in Cl− gradient in neonatal rat neocortex. J. Neurophysiol. 79: 439–446, 1998. We have studied the effects of γ-aminobutyric acid (GABA) and of reducing the Cl− gradient on the [Ca2+]i in pyramidal neurons of rat somatosensory cortex. The Cl− gradient was reduced either with furosemide or by oxygen-glucose deprivation. Immature slices taken at postnatal day (P)7–14 were labeled with fura-2, and [Ca2+]i was monitored in identified pyramidal cells in layer II/III as the ratio of fluorescence intensities (RF340/F380). The magnitude of the [Ca2+]i increases induced by oxygen-glucose deprivation was significantly reduced (by 44%) by bicuculline (10 μM), a GABAA receptor antagonist. Under normal conditions, GABA generally did not raise [Ca2+]i, although in some neurons a small and transient [Ca2+]i increase was observed. These transient [Ca2+]i increases were blocked by Ni2+ (1 mM), a blocker of voltage-dependent Ca2+ channels (VDCCs). Continuous perfusion with GABA did not cause a sustained elevation of [Ca2+]i but bicuculline caused [Ca2+]i oscillations. After inhibition of Cl− extrusion with furosemide (1.5 mM), GABA induced a large [Ca2+]i increase consisting of an initial peak followed by a sustained phase. Both the initial and the sustained phases were eliminated by bicuculline (10 μM). The initial but not the sustained phase was abolished by Ni2+. In the presence of Ni2+, the remaining sustained response was inhibited by the addition of 2-amino-5-phosphonopentanoic acid (AP5, 20 μM), a selective N-methyl-d-aspartate (NMDA) receptor antagonist. Thus the initial peak and the sustained phase of the GABA-evoked [Ca2+]i increase were mediated by Ca2+ influx through VDCCs and NMDA receptor channels, respectively, and both phases were initiated via the GABAA receptor. These results indicate that, in neocortical pyramidal neurons, a reduction in the Cl− gradient converts the GABAA receptor-mediated action from nothing or virtually nothing to a large and sustained accumulation of cellular Ca2+. This accumulation is the result of Ca2+ influx mainly through the NMDA receptor channel. Thus GABA, normally an inhibitory transmitter, may play an aggravating role in excitotoxicity if a shift in the Cl− equilibrium potential occurs, as reported previously, during cerebral ischemia.
Molecular Motor and Electrokinetic Contributions to Outer Hair Cell Electromotility
Authors: Jerry Rocco A. , Dutta Ashim
Published: December 2017

Jerry, Rocco A. and Ashim Dutta. Molecular motor and electrokinetic contributions to outer hair cell electromotility. J. Neurophysiol. 79: 471–473, 1998. The outer hair cell of the inner ear is believed to be responsible for the high sensitivity and selectivity of mammalian hearing. Molecular motors are generally believed to cause the electrically-driven length change (electromotility) of the outer hair cell. It has been suggested that electrokinetic effects might also play a significant role in electromotility, along with the molecular motors. This paper describes a new technique that can be used to experimentally determine the percentage of the electromotile response that is caused by electrokinetic effects. The technique is based on the novel idea that molecular motor activity cannot in itself generate a net force on the cell, but that electrokinetic effects can. Our method is the first that can separate molecular motor behavior from electrokinetic behavior, during experiments on the outer hair cell.
Dynamic Properties of Corticothalamic Neurons and Local Cortical Interneurons Generating Fast Rhythmic (30–40 Hz) Spike Bursts
Authors: Steriade Mircea , Timofeev Igor , Dürmüller Niklaus , Grenier François
Published: December 2017

Steriade, Mircea, Igor Timofeev, Niklaus Dürmüller, and François Grenier. Dynamic properties of corticothalamic neurons and local cortical interneurons generating fast rhythmic (30–40 Hz) spike-bursts. J. Neurophysiol. 79: 483–490, 1998. Fast spontaneous oscillations (mainly 30–40 Hz) characterize cortical and thalamic neuronal networks during behavioral states of increased vigilance and depend on cell depolarization under the influence of ascending activating systems. We investigated, by means of intracellular recording and staining in vivo, the properties of fast-oscillating cortical neurons from cat's motor and association areas, some projecting to the thalamus, others with locally arborizing axons. At a given level of depolarization, 28% of our neuronal sample discharged high-frequency spike bursts (300–600 Hz) that recurred rhythmically between 20 and 50 Hz. Such fast rhythmic bursting neurons have been found in both superficial and deep cortical layers. Slight changes in membrane potential as well as synaptic activity in thalamocortical networks dramatically altered the discharge patterns, from single spikes to rhythmic spike-bursts, and eventually to fast tonic firing without frequency adaptation. Thus our data challenge the conventional idea that sharply defined, invariant features and distinct locations in certain cortical layers characterize some neocortical cell-classes. We demonstrate that the distinctions between intrinsic electrophysiological properties of neocortical neurons are much more labile than conventionally thought. The present results, which indicate that corticothalamic neurons discharge fast rhythmic spike bursts mainly at 30–40 Hz, suggest that this activity results in integrated fast oscillations within corticothalamic networks.
Altered Spectral Localization Cues Disrupt the Development of the Auditory Space Map in the Superior Colliculus of the Ferret
Authors: Schnupp Jan W. H. , King Andrew J. , Carlile Simon
Published: December 2017

Schnupp, Jan W. H., Andrew J. King, and Simon Carlile. Altered spectral localization cues disrupt the development of the auditory space map in the superior colliculus of the ferret. J. Neurophysiol. 79: 1053–1069, 1998. Spectral localization cues provided by the outer ear are utilized in the construction of the auditory space map in the superior colliculus (SC). The role of the outer ear in the development of this map was examined by recording from the SC of anesthetized, adult ferrets in which the pinna and concha had been removed in infancy. The acoustical consequences of this procedure were assessed by recording outer ear impulse responses via a probe-tube microphone implanted in the wall of the ear canal. Both monaural and binaural spectral cues normally show a number of asymmetric features within the horizontal plane, which allow azimuthal locations on either side of the interaural axis to be discriminated. These features were eliminated or altered by chronic pinnectomy. The responses of auditory units in the SC to noise bursts presented in the free field were examined at sound levels of ∼10 and 25 dB above unit threshold. After bilateral pinnectomy, the representation of auditory space was severely degraded at both sound levels. In contrast to normal ferrets, many units had bilobed azimuthal response profiles, indicating that they were unable to resolve sound locations on either side of the interaural axis. There was also much less order in the distribution of best azimuths or elevations of those units that were tuned to a single direction. Some units were tuned to locations that extended much further into the hemifield ipsilateral to the recording side than the normal range of best azimuths. Unilateral removal of the outer ear, which disrupts the monaural spectral cues for one side only, had a much smaller effect on the development of the auditory representation. At supra- and near-threshold sound levels, the representation of sound azimuth in the SC on both sides of the brain was less scattered than that found after bilateral pinna removal. Nevertheless, units with bilobed responses, broader tuning, and inappropriate best azimuths were observed in both the left and right SC of ferrets in which the left pinna and concha had been removed in infancy. These data illustrate that the localization cues provided by the outer ear play a critical role in the development of the auditory space map in the SC. In contrast to other manipulations of either auditory or visual inputs, the map does not appear to adapt to the changes in spectral cues brought about by pinna removal, suggesting that residual binaural cues are, by themselves, insufficient for its normal maturation.
Noise-Induced Spiral Waves in Astrocyte Syncytia Show Evidence of Self-Organized Criticality
Authors: Jung Peter , Cornell-Bell Ann , Madden Kathleen Shaver , Moss Frank
Published: December 2017

Jung, Peter, Ann Cornell-Bell, Kathleen Shaver Madden, and Frank Moss. Noise-induced spiral waves in astrocyte syncytia show evidence of self-organized criticality. J. Neurophysiol. 79: 1098–1101, 1998. Long range (a few centimeters), long lived (many seconds), spiral chemical waves of calcium ions (Ca2+) are observed in cultured networks of glial cells for normal concentrations of the neurotransmitter kainate. A new method for quantitatively measuring the spatiotemporal size of the waves is described. This measure results in a power law distribution of wave sizes, meaning that the process that creates the waves has no preferred spatial or temporal (size or lifetime) scale. This power law is one signature of self-organized critical phenomena, a class of behaviors found in many areas of science. The physiological results for glial networks are fully supported by numerical simulations of a simple network of noisy, communicating threshold elements. By contrast, waves observed in astrocytes cultured from human epileptic foci exhibited radically different behavior. The background random activity, or “noise”, of the network is controlled by the kainate concentration. The mean rate of wave nucleation is mediated by the network noise. However, the power law distribution is invariant, within our experimental precision, over the range of noise intensities tested. These observations indicate that spatially and temporally coherent Ca2+ waves, mediated by network noise may play and important role in generating correlated neural activity (waves) over long distances and times in the healthy vertebrate central nervous system.
Rapid Plasticity of Human Cortical Movement Representation Induced by Practice
Authors: Classen Joseph , Liepert Joachim , Wise Steven P. , Hallett Mark , Cohen Leonardo G.
Published: December 2017

Classen, Joseph, Joachim Liepert, Steven P. Wise, Mark Hallett, and Leonardo G. Cohen. Rapid plasticity of human cortical movement representation induced by practice. J. Neurophysiol. 79: 1117–1123, 1998. The process of acquiring motor skills through the sustained performance of complex movements is associated with neural plasticity. However, it is unknown whether even simple movements, repeated over a short period of time, are effective in inducing cortical representational changes. Whether the motor cortex can retain specific kinematic aspects of a recently practiced movement is also unknown. We used focal transcranial magnetic stimulation (TMS) of the motor cortex to evoke isolated and directionally consistent thumb movements. Thumb movements then were practiced in a different direction. Subsequently, TMS came to evoke movements in or near the recently practiced direction for several minutes before returning to the original direction. To initiate a change of the TMS-evoked movement direction, 15 or 30 min of continuous training were required in most of the subjects and, on two occasions, as little as 5 or 10 min. Substantially smaller effects followed more direct stimulation of corticofugal axons with transcranial electrical stimulation, pointing to cortex as the site of plasticity. These findings suggest that the training rapidly, and transiently, established a change in the cortical network representing the thumb, which encoded kinematic details of the practiced movement. This phenomenon may be regarded as a short-term memory for movement and be the first step of skill acquisition.
Biophysical and Pharmacological Characterization of Voltage-Dependent Ca2+Channels in Neurons Isolated From Rat Nucleus Accumbens
Authors: Churchill Dennis , Macvicar Brian A.
Published: December 2017

Churchill, Dennis and Brian A. MacVicar. Biophysical and pharmacological characterization of voltage-dependent Ca2+channels in neurons isolated from rat nucleus accumbens. J. Neurophysiol. 79: 635–647, 1998. The nucleus accumbens (NA) has an integrative role in behavior and may mediate addictive and psychotherapeutic drug action. Whole cell recording techniques were used to characterize electrophysiologically and pharmacologically high- and low-threshold voltage-dependent Ca2+currents in isolated NA neurons. High-threshold Ca2+currents, which were found in all neurons studied and include both sustained and inactivating components, activated at potentials greater than −50 mV and reached maximal activation at ∼0 mV. In contrast, low-threshold Ca2+currents activated at voltages greater than −64 mV with maximal activation occurring at −30 mV. These were observed in 42% of acutely isolated neurons. Further pharmacological characterization of high-threshold Ca2+currents was attempted using nimodipine (Nim), ω-conotoxin-GVIA (ω-CgTx) and ω-agatoxin-IVA (ωAga), which are thought to identify the L, N, and P/Q subtypes of Ca2+currents, respectively. Nim (5–10 μM) blocked 18%, ωCgTx (1–2 μM) blocked 25%, and ωAga (200 nM) blocked 17% of total Ca2+current. Nim primarily blocked a sustained high-threshold Ca2+current in a partially reversible manner. In contrast, ωCgTx irreversibly blocked both sustained and inactivating components. ωAga irreversibly blocked only a sustained component. In all three of these Ca2+channel blockers, plus 5 μM ω-conotoxin-MVIIC to eliminate a small unblocked Q-type Ca2+current (7%), a toxin-resistant high-threshold Ca2+current remained that was 32% of total Ca2+current. This current inactivated much more rapidly than the other high-threshold Ca2+currents, was depressed in 50 μM Ni2+and reached maximal activation 5–10 mV negative to the toxin-sensitive high-threshold Ca2+currents. Thus NA neurons have multiple types of high-threshold Ca2+currents with a large component being the toxin-resistant “R” component.
Transient Suppression of GABAA-Receptor–Mediated IPSPs After Epileptiform Burst Discharges in CA1 Pyramidal Cells
Authors: Beau F.E.N. Le , Alger B. E.
Published: December 2017

Le Beau, F.E.N. and B. E. Alger. Transient suppression ofGABAA-receptor–mediated IPSPs after epileptiform burst discharges in CA1 pyramidal cells. J. Neurophysiol. 79: 659–669, 1998. Epileptiform burst discharges were elicited in CA1 hippocampal pyramidal cells in the slice preparation by perfusion with Mg2+-free saline. Intracellular recordings revealed paroxysmal depolarization shifts (PDSs) that either occurred spontaneously or were evoked by stimulation of Schaffer collaterals. These bursts involved activation of N-methyl-d-aspartate receptors because burst discharges were reduced or abolished by dl-2-amino-5-phosphonovaleric acid. Bath application of carbachol caused an increase in spontaneous activity that was predominantly due to γ-aminobutyric acid-A-receptor–mediated spontaneous inhibitory postsynaptic potentials (sIPSPs). A marked reduction in sIPSPs (31%) was observed after each epileptiform burst discharge, which subsequently recovered to preburst levels after ∼4–20 s. This sIPSP suppression was not associated with any change in postsynaptic membrane conductance. A suppression of sIPSPs also was seen after burst discharges evoked by brief (100–200 ms) depolarizing current pulses. N-ethylmaleimide, which blocks pertussis-toxin–sensitive G proteins, significantly reduced the suppression of sIPSPs seen after a burst response. When increases in intracellular Ca2+ were buffered by intracellular injection of ethylene glycol bis(β-aminoethyl)ether- N,N,N′,N′-tetraacetic acid, the sIPSP suppression seen after a single spontaneous or evoked burst discharge was abolished. Although we cannot exclude other Ca2+-dependent mechanisms, this suppression of sIPSPs shared many of the characteristics of depolarization-induced suppression of inhibition (DSI) in that it involved activation of G proteins and was dependent on increases in intracellular calcium. These findings suggest that a DSI-like process may be activated by the endogenous burst firing of CA1 pyramidal neurons.