bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Neural Interactions Explains the Activation of Occipital Cortex by an Auditory Stimulus
Authors: McIntosh A. R. , Cabeza R. E. , Lobaugh N. J.
Published: December 2017

McIntosh, A. R., R. E. Cabeza, and N. J. Lobaugh. Analysis of neural interactions explains the activation of occipital cortex by an auditory stimulus . J. Neurophysiol. 80: 2790–2796, 1998. Large-scale neural interactions were characterized in human subjects as they learned that an auditory stimulus signaled a visual event. Once learned, activation of left dorsal occipital cortex (increased regional cerebral blood flow) was observed when the auditory stimulus was presented alone. Partial least-squares analysis of the interregional correlations (functional connectivity) between the occipital area and the rest of the brain identified a pattern of covariation with four dominant brain areas that could have mediated this activation: prefrontal cortex (near Brodmann area 10, A10), premotor cortex (A6), superior temporal cortex (A41/42), and contralateral occipital cortex (A18). Interactions among these regions and the occipital area were quantified with structural equation modeling to identify the strongest sources of the effect on left occipital activity (effective connectivity). Learning-related changes in feedback effects from A10 and A41/42 appeared to account for this change in occipital activity. Influences from these areas on the occipital area were initially suppressive, or negative, becoming facilitory, or positive, as the association between the auditory and visual stimuli was acquired. Evaluating the total effects within the functional models showed positive influences throughout the network, suggesting enhanced interactions may have primed the system for the now-expected visual discrimination. By characterizing both changes in activity and the interactions underlying sensory associative learning, we demonstrated how parts of the nervous system operate as a cohesive network in learning about and responding to the environment.
Effects of PKA and PKC on Miniature Excitatory Postsynaptic Currents in CA1 Pyramidal Cells
Authors: Carroll Reed C. , Nicoll Roger A. , Malenka Robert C.
Published: December 2017

Carroll, Reed C., Roger A. Nicoll, and Robert C. Malenka. Effects of PKA and PKC on miniature excitatory postsynaptic currents in CA1 pyramidal cells. J. Neurophysiol. 80: 2797–2800, 1998. Protein kinases play an important role in controlling synaptic strength at excitatory synapses on CA1 pyramidal cells. We examined the effects of activating cAMP-dependent protein kinase or protein kinase C (PKC) on the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) with perforated patch recording techniques. Both forskolin and phorbol-12,13-dibutryate (PDBu) caused a large increase in mEPSC frequency, but only PDBu increased mEPSC amplitude, an effect that was not observed when standard whole cell recording was performed. These results support biochemical observations indicating that PKC, similar to calcium/calmodulin-dependent protein kinase II, has an important role in controlling synaptic strength via modulation of AMPA receptor function, potentially through the direct phosphorylation of the GluR1 subunit.
Flare and Hyperalgesia After Intradermal Capsaicin Injection in Human Skin
Authors: Serra Jordi , Campero Mario , Ochoa José
Published: December 2017

Serra, Jordi, Mario Campero, and José Ochoa. Flare and hyperalgesia after intradermal capsaicin injection in human skin. J. Neurophysiol. 80: 2801–2810, 1998. We investigated the neurovascular mechanisms that determine the flare response to intradermal capsaicin injection in humans and delineated the associated areas of mechanical and heat hyperalgesia. The flare response was monitored both visually and with infrared telethermography. The areas of mechanical and heat hyperalgesia were determined psychophysically. Thermography detected very large areas of flare. As an early event underlying the flare and before onset of the area of rubor of the skin, thermography detected the appearance of multifocal spots of increased temperature caused by dilatation of cutaneous arterioles. Repetition of capsaicin injection days apart into the same forearm induced multifocal spots of temperature elevation identical to the ones obtained in the first session, indicating dilatation of the same arterioles. Reactive hyperemia also consisted in the appearance of multifocal spots of increased temperature, which were identical to the ones reacting during the flare response, suggesting participation of the same arterioles in both events. Strips of local anesthetic placed to block cutaneous nerves prevented the spread of both the thermographic flare and associated hyperalgesia. It is inferred that the cutaneous nerve fibers responsible for the thermographic flare branch, or have coupled axons, over a long distance. The large area of flare coincided with the area of mechanical and heat hyperalgesia. Equivalence of the areas of flare and mechanical and heat hyperalgesia induced by intradermal capsaicin injection suggests that all three phenomena are the consequence of neural factors that operate peripherally.
Lateralized Human Cortical Activity for Shifting Visuospatial Attention and Initiating Saccades
Authors: Wauschkuhn Bernd , Verleger Rolf , Wascher Edmund , Klostermann Wolfgang , Burk Marcel , Heide Wolfgang , Kömpf Detlef
Published: December 2017

Wauschkuhn, Bernd, Rolf Verleger, Edmund Wascher, Wolfgang Klostermann, Marcel Burk, Wolfgang Heide, and Detlef Kömpf. Lateralized human cortical activity for shifting visuospatial attention and initiating saccades. J. Neurophysiol. 80: 2900–2910, 1998. The relation between shifts of visual attention and saccade preparation was investigated by studying their electrophysiological correlates in human scalp-recorded electroencephalogram (EEG). Participants had to make saccades either to a saliently colored or to a gray circle, simultaneously presented in opposite visual hemifields, under different task instructions. EEG was measured within the short interval between stimulus onset and saccade, focusing on lateralized activity, contralateral either to the side of the relevant stimulus or to the direction of the saccade. Three components of lateralization were found: 1) activity contralateral to the relevant stimulus irrespective of saccade direction, peaking 250 ms after stimulus onset, largest above lateral parietal sites, 2) activity contralateral to the relevant stimulus if the stimulus was also the target of the saccade, largest 330–480 ms after stimulus onset, widespread over the scalp but with a focus again above lateral parietal sites, and 3) activity contralateral to saccade direction, beginning about 100 ms before the saccade, largest above mesial parietal sites, with some task-dependent fronto–central contribution. Because of their sensitivity to task variables, component 1 is interpreted as the shifting of attention to the relevant stimulus, component 2 is interpreted as reflecting the enhancement of the attentional shift if the relevant stimulus is also the saccade target, and component 3 is interpreted as the triggering signal for saccade execution. Thus human neurophysiological data provided evidence both for independent and interdependent processes of saccade preparation and shifts of visual attention.
Responses of Neurons in Inferior Temporal Cortex During Memory-Guided Visual Search
Authors: Chelazzi Leonardo , Duncan John , Miller Earl K. , Desimone Robert
Published: December 2017

Chelazzi, Leonardo, John Duncan, Earl K. Miller, and Robert Desimone. Responses of neurons in inferior temporal cortex during memory-guided visual search. J. Neurophysiol. 80: 2918–2940, 1998. A typical scene will contain many different objects, few of which are relevant to behavior at any given moment. Thus attentional mechanisms are needed to select relevant objects for visual processing and control over behavior. We examined this role of attention in the inferior temporal cortex of macaque monkeys, using a visual search paradigm. While the monkey maintained fixation, a cue stimulus was presented at the center of gaze, followed by a blank delay period. After the delay, an array of two to five choice stimuli was presented extrafoveally, and the monkey was rewarded for detecting a target stimulus matching the cue. The behavioral response was a saccadic eye movement to the target in one version of the task and a lever release in another. The array was composed of one “good” stimulus (effective in driving the cell when presented alone) and one or more “poor” stimuli (ineffective in driving the cell when presented alone). Most cells showed higher delay activity after a good stimulus used as the cue than after a poor stimulus. The baseline activity of cells was also higher preceding a good cue, if the animal expected it to occur. This activity may depend on a top-down bias in favor of cells coding the relevant stimulus. When the choice array was presented, most cells showed suppressive interactions between the stimuli as well as strong attention effects. When the choice array was presented in the contralateral visual field, most cells initially responded the same, regardless of which stimulus was the target. However, within 150–200 ms of array onset, responses were determined by the target stimulus. If the target was the good stimulus, the response to the array became equal to the response to the good stimulus presented alone. If the target was a poor stimulus, the response approached the response to that stimulus presented alone. Thus the influence of the nontarget stimulus was eliminated. These effects occurred well in advance of the behavioral response. When the array was positioned with stimuli on opposite sides of the vertical meridian, the contralateral stimulus appeared to dominate the response, and this dominant effect could not be overcome by attention. Overall, the results support a “biased competition” model of attention, according to which 1) objects in the visual field compete for representation in the cortex, and 2) this competition is biased in favor of the behaviorally relevant object by virtue of “top-down” feedback from structures involved in working memory.
Strobe Rearing Prevents the Convergence of Inputs With Different Response Timings Onto Area 17 Simple Cells
Authors: Humphrey Allen L. , Saul Alan B. , Feidler Jordan C.
Published: December 2017

Humphrey, Allen L., Alan B. Saul, and Jordan C. Feidler. Strobe rearing prevents the convergence of inputs with different response timings onto area 17 simple cells. J. Neurophysiol. 80: 3005–3020, 1998. The preceding paper showed that the loss of direction selectivity in simple cells induced by strobe rearing reflects the elimination of spatially ordered response timing differences across the receptive field that underlie spatiotemporal (S-T) inseparability. Here we addressed whether these changes reflected an elimination of certain timings or an alteration in how timings were associated in single cells. Timing in receptive fields was measured using stationary bars undergoing sinusoidal luminance modulation at different temporal frequencies (0.5–6 Hz). For each bar position, response phase versus temporal frequency data were fit by a line to obtain two measures: absolute phase and latency. In normal cats, many individual simple cells display a wide range of timings; in layer 4, the mean range for absolute phase and latency was 0.21 cycles and 39 ms, respectively. Strobe rearing compressed the mean timing ranges in single cells, to 0.08 cycles and 31 ms, respectively, and this compression accounted for the loss of inseparability. A similar compression was measured in layer 6 cells. In contrast, the range of timing values across the simple-cell population was relatively normal. Single cells merely sampled narrower than normal regions of the timing space. We sought to understand these cortical changes in terms of how inputs from the lateral geniculate nucleus (LGN) may have been affected by strobe rearing. In normal cats, a wide range of absolute phase and latency values exists among lagged and nonlagged LGN cells, and these thalamic timings account for most of the cortical timings. Also, S-T inseparability in many simple cells can be attributed to the convergence of lagged and/or nonlagged inputs. Strobe rearing did not change the sampling of lagged and nonlagged cells, and the geniculate timings continued to account for most of the cortical timings. However, strobe rearing virtually eliminated cortical receptive fields with mixed lagged and nonlagged timing, and it compressed the timing range in cells dominated by one or the other geniculate type. Thus strobe rearing did not eliminate certain timings in LGN or cortex, but prevented the convergence of different timings on single cells. To account for these results, we propose a developmental model in which strobe stimulation alters the correlational structure of inputs based on their response timing. Only inputs with similar timing become associated on single cortical cells, and this produces S-T separable receptive fields that lack the ability to confer a preferred direction of motion.
Reconfiguration of the Respiratory Network at the Onset of Locust Flight
Authors: Ramirez Jan-Marino
Published: December 2017

Ramirez, Jan-Marino. Reconfiguration of the respiratory network at the onset of locust flight. J. Neurophysiol. 80: 3137–3147, 1998. The respiratory interneurons 377, 378, 379 and 576 were identified within the suboesophageal ganglion (SOG) of the locust. Intracellular stimulation of these neurons excited the auxillary muscle 59 (M59), a muscle that is involved in the control of thoracic pumping in the locust. Like M59, these interneurons did not discharge during each respiratory cycle. However, the SOG interneurons were part of the respiratory rhythm generator because brief intracellular stimulation of these interneurons reset the respiratory rhythm and tonic stimulation increased the frequency of respiratory activity. At the onset of flight, the respiratory input into M59 and the SOG interneurons was suppressed, and these neurons discharged in phase with wing depression while abdominal pumping movements remained rhythmically active in phase with the slower respiratory rhythm (Fig. 9 ). The suppression of the respiratory input during flight seems to be mediated by the SOG interneuron 388. This interneuron was tonically activated during flight, and intracellular current injection suppressed the respiratory rhythmic input into M59. We conclude that the respiratory rhythm generator is reconfigured at flight onset. As part of the rhythm-generating network, the interneurons in the SOG are uncoupled from the rest of the respiratory network and discharge in phase with the flight rhythm. Because these SOG interneurons have a strong influence on thoracic pumping, we propose that this neural reconfiguration leads to a behavioral reconfiguration. In the quiescent state, thoracic pumping is coupled to the abdominal pumping movements and has auxillary functions. During flight, thoracic pumping is coupled to the flight rhythm and provides the major ventilatory movements during this energy-demanding locomotor behavior.
Both Supplementary and Presupplementary Motor Areas Are Crucial for the Temporal Organization of Multiple Movements
Authors: Shima Keisetsu , Tanji Jun
Published: December 2017

Shima, Keisetsu and Jun Tanji. Both supplementary and presupplementary motor areas are crucial for the temporal organization of multiple movements. J. Neurophysiol. 80: 3247–3260, 1998. To study the involvement of the supplementary (SMA) and presupplementary (pre-SMA) motor areas in performing sequential multiple movements that are individually separated in time, we injected muscimol, a γ-aminobutyric acid agonist, bilaterally into the part of each area that represents the forelimb. Two monkeys were trained to perform three different movements, separated by a waiting time, in four or six different orders. First, each series of movements was learned during five trials guided by visual signals that indicated the correct movements. The monkeys subsequently executed the three movements in the memorized order, without the visual signals. After the injection of muscimol (3 μl, 5 μg/μl in 10 min) into either the SMA or pre-SMA bilaterally, the animals started making errors in performing the sequence of movements correctly from memory. However, when guided with a visual signal, they could select and perform the three movements correctly. The impaired memory-based sequencing of movements worsened progressively with time until the animals could not perform the task. Yet they still could associate the visual signals with the different movements at that stage. In control experiments on two separate monkeys, we found that injections of the same amount of muscimol into either the SMA or pre-SMA did not cause problems with nonsequential reaching movement regardless of whether it was visually triggered or self-initiated. These results support the view that both the SMA and pre-SMA are crucially involved in sequencing multiple movements over time.
Frontal Eye Field Neurons Orthodromically Activated From the Superior Colliculus
Authors: Sommer Marc A. , Wurtz Robert H.
Published: December 2017

Sommer, Marc A. and Robert H. Wurtz. Frontal eye field neurons orthodromically activated from the superior colliculus. J. Neurophysiol. 80: 3331–3333, 1998. Anatomical studies have shown that the frontal eye field (FEF) and superior colliculus (SC) of monkeys are reciprocally connected, and a physiological study described the signals sent from the FEF to the SC. Nothing is known, however, about the signals sent from the SC to the FEF. We physiologically identified and characterized FEF neurons that are likely to receive input from the SC. Fifty-two FEF neurons were found that were orthodromically activated by electrical stimulation of the intermediate or deeper layers of the SC. All the neurons that we tested ( n = 34) discharged in response to visual stimulation. One-half also discharged when saccadic eye movements were made. This provides the first direct evidence that the ascending pathway from SC to FEF might carry visual- and saccade-related signals. Our findings support a hypothesis that the SC and the FEF interact bidirectionally during the events leading up to saccade generation.
Modulation of Calcium-Dependent Postsynaptic Depression Contributes to an Adaptive Sensory Filter
Authors: Bastian Joseph
Published: December 2017

Bastian, Joseph. Modulation of calcium-dependent postsynaptic depression contributes to an adaptive sensory filter. J. Neurophysiol. 80: 3352–3355, 1998. The ability of organisms to ignore unimportant patterns of sensory input may be as critical as the ability to attend to those that are behaviorally relevant. Mechanisms used to reject irrelevant inputs range from peripheral filters, which allow only restricted portions of the spectrum of possible inputs to pass, to higher-level processes, which actively select stimuli to be “attended to.” Recent studies of several lower vertebrates demonstrate the presence of adaptive sensory filters, which “learn,” with a time course of a few minutes, to cancel predictable patterns of sensory input without compromising responses to novel stimuli. Predictable stimuli include “reafferent” stimuli, which occur as a result of an animal's own activity, as well as stimuli that are simply repetitive. The adaptive characteristic of these filters depends on an anti-Hebbian form of synaptic plasticity that modulates the strength of multisensory dendritic inputs resulting in the genesis of “negative image” signals, which cancel the predicted pattern of sensory afference. This report provides evidence that the mechanism underlying the anti-Hebbian plasticity involves the modulation of a calcium-dependent form of postsynaptic depression.
Spontaneous Apamin-Sensitive Hyperpolarizations in Dopaminergic Neurons of Neonatal Rats
Authors: Seutin Vincent , Massotte Laurent , Scuvée-Moreau Jacqueline , Dresse Albert
Published: December 2017

Seutin, Vincent, Laurent Massotte, Jacqueline Scuvée-Moreau, and Albert Dresse. Spontaneous apamin-sensitive hyperpolarizations in dopaminergic neurons of neonatal rats. J. Neurophysiol. 80: 3361–3364, 1998. Intracellular recordings from substantia nigra slices revealed the existence of spontaneous hyperpolarizations (amplitude 2–8 mV, duration 100–400 ms) at −60 mV in most dopaminergic neurons of neonatal (9–15 days) but not adult rats. These events were blocked by apamin (300 nM) and bicuculline methochloride (100–300 μM), which blocks apamin-sensitive currents. They were unaffected by the selective γ-aminobutyric acid-A (GABAA) antagonists SR95531 (100 μM) and picrotoxin (30–50 μM), the GABAB antagonist CGP35348 (300 μM), the D2 antagonist haloperidol (1 μM), and the metabotropic antagonist MCPG (1 mM). The hyperpolarizations were strongly attenuated or abolished when recording electrodes contained 200 mM 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid. They were resistant to tetrodotoxin in the majority of the cells. They had some voltage dependency and were in some cases transiently potentiated when cells were briefly depolarized by current injection. We conclude that dopaminergic neurons have developmentally regulated physiological properties. These spontaneous hyperpolarizations might affect the firing rate of these cells, which was found to be lower in neonates than in adults.
Developmental Changes in the Nicotinic Responses of Ciliary Ganglion Neurons
Authors: Blumenthal Edward M. , Shoop Richard D. , Berg Darwin K.
Published: December 2017

Blumenthal, Edward M., Richard D. Shoop, and Darwin K. Berg. Developmental changes in the nicotinic responses of ciliary ganglion neurons. J. Neurophysiol. 81: 111–120, 1999. The accumulation of functional neurotransmitter receptors by neurons during development is an essential part of synapse formation. Chick ciliary ganglion neurons express two kinds of nicotinic receptors. One is abundant, contains the α7 gene product, rapidly desensitizes, and binds α-bungarotoxin. The other is less abundant, contains multiple gene products (α3, β4, α5, and β2 subunits), slowly desensitizes, and binds the monoclonal antibody mAb 35. Rapid application of agonist to freshly dissociated neurons elicits responses from both classes of receptors. Between embryonic days 8 and 15, the whole cell response of α3-containing receptors increases fivefold in peak amplitude and, normalized for cell growth, 1.7-fold in current density. In addition, the response decays more slowly in older neurons, suggesting a developmental decrease in the rate of desensitization. The whole cell response of α7-containing receptors increases 10-fold in peak amplitude over the same period and 3-fold in current density. No change in the rate of desensitization was apparent for α7-containing receptors with developmental age, but analysis was limited by overlap in responses from the two kinds of receptors. Indirect immunofluorescence measurements on dissociated neurons showed that the relative levels of α7-containing receptors on the soma increased during development to the same extent as the whole cell response attributed to them. In contrast, the relative levels of α3-containing receptors increased more during the same time period than did the whole cell response they generated. The immunofluorescence analysis also showed that both classes of receptors become distributed in prominent clusters on the cell surface as a function of developmental age. The results indicate that during this period of synaptic consolidation on the neurons, the two major classes of functional nicotinic receptors undergo substantial upregulation; α3-containing receptors as a class may undergo changes in receptor properties as well.
Serotonin Modulates Spike Backpropagation and Associated [Ca2+]iChanges in the Apical Dendrites of Hippocampal CA1 Pyramidal Neurons
Authors: Sandler Vladislav M. , Ross William N.
Published: December 2017

Sandler, Vladislav M. and William N. Ross. Serotonin modulates spike backpropagation and associated [Ca2+]ichanges in the apical dendrites of hippocampal CA1 pyramidal neurons. J. Neurophysiol. 81: 216–224, 1999. The effect of serotonin (5-HT) on somatic and dendritic properties was analyzed in pyramidal neurons from the CA1 region in slices from the rat hippocampus. Bath-applied 5-HT (10 μM) hyperpolarized the soma and apical dendrites and caused a conductance increase at both locations. In the dendrites (200–300 μm from the soma) trains of antidromically activated, backpropagating action potentials had lower peak potentials in 5-HT than in normal artificial cerebrospinal fluid. Spike amplitudes were about the same in the two solutions. Similar results were found when the action potentials were evoked synaptically with stimulation in the stratum oriens. In the soma, spike amplitudes increased in 5-HT, with only a small decrease in the peak potential. Calcium concentration measurements, made with bis-fura-2 injected through patch electrodes, showed that the amplitude of the [Ca2+]ichanges was reduced at all locations in 5-HT. The reduction of the [Ca2+]ichange in the soma was confirmed in slices where cells were loaded with fura-2-AM. The reduction at the soma in 5-HT, where the spike amplitude increased, suggests that the reduction is due primarily to direct modulation of Ca2+channels. In the dendrites, the reduction is due to a combination of this channel modulation and the lowering of the peak potential of the action potentials.
Synaptic Organization and Neurotransmitters in the Rat Accessory Olfactory Bulb
Authors: Jia Changping , Chen Wei R. , Shepherd Gordon M.
Published: December 2017

Jia, Changping, Wei R. Chen, and Gordon M. Shepherd. Synaptic organization and neurotransmitters in the rat accessory olfactory bulb. J. Neurophysiol. 81: 345–355, 1999. The accessory olfactory bulb (AOB) is the first relay station in the vomeronasal system and may play a critical role in processing pheromone signals. The AOB shows similar but less distinct lamination compared with the main olfactory bulb (MOB). In this study, synaptic organization of the AOB was analyzed in slice preparations from adult rats by using both field potential and patch-clamp recordings. Stimulation of the vomeronasal nerve (VN) evoked field potentials that showed characteristic patterns in different layers of the AOB. Current source density (CSD) analysis of the field potentials revealed spatiotemporally separated loci of inward current (sinks) that represented sequential activation of different neuronal components: VN activity (period I), synaptic excitation of mitral cell apical dendrites (period II), and activation of granule cells by mitral cell basal dendrites (period III). Stimulation of the lateral olfactory tract also evoked field potentials in the AOB, which indicated antidromic activation of the mitral cells (period I and II) followed by activation of granule cells (period III). Whole cell patch recordings from mitral and granule cells of the AOB supported that mitral cells are excited by VN terminals and subsequently activate granule cells through dendrodendritic synapses. Both CSD analysis and patch recordings provided evidence that glutamate is the neurotransmitter at the vomeronasal receptor neuron; mitral cell synapses and both NMDA and non-NMDA receptors are involved. We also demonstrated electrophysiologically that reciprocal interaction between mitral and granule cells in the AOB is through the dendrodendritic reciprocal synapses. The neurotransmitter at the mitral-to-granule synapses is glutamate and at the granule-to-mitral synapse is γ-aminobutyric acid. The synaptic interactions among receptor cell terminals, mitral cells, and granule cells in the AOB are therefore similar to those in the MOB, suggesting that processing of chemosensory information in the AOB shares similarities with that in the MOB.
Membrane Potential and Intracellular Ca2+Oscillations Activated by mGluRs in Hippocampal Stratum Oriens/Alveus Interneurons
Authors: Woodhall Gavin , Gee Christine E. , Robitaille Richard , Lacaille Jean-Claude
Published: December 2017

Woodhall, Gavin, Christine E. Gee, Richard Robitaille, and Jean-Claude Lacaille. Membrane potential and intracellular Ca2+oscillations activated by mGluRs in hippocampal stratum oriens/alveus interneurons. J. Neurophysiol. 81: 371–382, 1999. Metabotropic glutamate receptors (mGluRs) are expressed heterogeneously in hippocampal interneurons, and their signal transduction cascades remain largely unclear. We characterized an oscillatory response activated by the mGluR agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) in hippocampal interneurons of stratum oriens-alveus (OA) with simultaneous whole cell current-clamp recordings and intracellular Ca2+imaging with confocal microscopy. 1S,3R-ACPD induced oscillatory membrane depolarizations and rises in intracellular Ca2+that persisted in tetrodotoxin and were blocked by the antagonist of group I and II mGluRs (S)-α-methyl-4-carboxyphenylglycine. Membrane depolarizations and intracellular Ca2+rises were blocked by extracellular Cd2+and in Ca2+-free medium. mGluR responses therefore required Ca2+influx via voltage-gated Ca2+channels. 1S,3R-ACPD responses were also antagonized by depleting intracellular stores with thapsigargin and ryanodine, indicating that Ca2+release from intracellular stores was also necessary. These data suggest that oscillatory responses generated by group I/II mGluRs involve a coupling of Ca2+entry through voltage-gated Ca2+channels and Ca2+release from internal stores. In contrast, 1S,3R-ACPD evoked only smaller depolarizations and intracellular Ca2+rises, with no oscillations, in other hippocampal interneurons located in or near stratum lacunosum-moleculare. Thus mGluR-mediated oscillatory responses are specifically expressed in certain interneuron subtypes. This heterogeneous expression of glutamate and Ca2+signaling pathways in specific interneurons may be relevant to their selective vulnerability to excitotoxicity.
Activation of Distinct Motor Cortex Regions During Ipsilateral and Contralateral Finger Movements
Authors: Cramer Steven C. , Finklestein Seth P. , Schaechter Judith D. , Bush George , Rosen Bruce R.
Published: December 2017

Cramer, Steven C., Seth P. Finklestein, Judith D. Schaechter, George Bush, and Bruce R. Rosen. Activation of distinct motor cortex regions during ipsilateral and contralateral finger movements. J. Neurophysiol. 81: 383–387, 1999. Previous studies have shown that unilateral finger movements are normally accompanied by a small activation in ipsilateral motor cortex. The magnitude of this activation has been shown to be altered in a number of conditions, particularly in association with stroke recovery. The site of this activation, however, has received limited attention. To address this question, functional magnetic resonance imaging (MRI) was used to study precentral gyrus activation in six control and three stroke patients during right index finger tapping, then during left index finger tapping. In each hemisphere, the most significantly activated site ( P < 0.001 required) was identified during ipsilateral and during contralateral finger tapping. In the motor cortex of each hemisphere, the site activated during use of the ipsilateral hand differed from that found during use of the contralateral hand. Among the 11 control hemispheres showing significant activation during both motor tasks, the site for ipsilateral hand representation (relative to contralateral hand site in the same hemisphere) was significantly shifted ventrally in all 11 hemispheres (mean, 11 mm), laterally in 10/11 hemispheres (mean, 12 mm), and anteriorly in 8/11 hemispheres (mean, 10 mm). In 6 of 11 hemispheres, tapping of the contralateral finger simultaneously activated both the ipsilateral and the contralateral finger sites, suggesting bilateral motor control by the ipsilateral finger site. The sites activated during ipsilateral and contralateral hand movement showed similar differences in the unaffected hemisphere of stroke patients. The region of motor cortex activated during ipsilateral hand movements is spatially distinct from that identified during contralateral hand movements.
Oculomotor Control of Primary Eye Position Discriminates Between Translation and Tilt
Authors: Hess Bernhard J. M. , Angelaki Dora E.
Published: December 2017

Hess, Bernhard J. M. and Dora E. Angelaki. Oculomotor control of primary eye position discriminates between translation and tilt. J. Neurophysiol. 81: 394–398, 1999. We have previously shown that fast phase axis orientation and primary eye position in rhesus monkeys are dynamically controlled by otolith signals during head rotations that involve a reorientation of the head relative to gravity. Because of the inherent ambiguity associated with primary otolith afferent coding of linear accelerations during head translation and tilts, a similar organization might also underlie the vestibulo-ocular reflex (VOR) during translation. The ability of the oculomotor system to correctly distinguish translational accelerations from gravity in the dynamic control of primary eye position has been investigated here by comparing the eye movements elicited by sinusoidal lateral and fore-aft oscillations (0.5 Hz ± 40 cm, equivalent to ± 0.4 g) with those during yaw rotations (180°/s) about a vertically tilted axis (23.6°). We found a significant modulation of primary eye position as a function of linear acceleration (gravity) during rotation but not during lateral and fore-aft translation. This modulation was enhanced during the initial phase of rotation when there was concomitant semicircular canal input. These findings suggest that control of primary eye position and fast phase axis orientation in the VOR are based on central vestibular mechanisms that discriminate between gravity and translational head acceleration.
A Relative Energy Failure Is Associated With Low-Mg2+But Not With 4-Aminopyridine Induced Seizure-Like Events in Entorhinal Cortex
Authors: Schuchmann S. , Buchheim K. , Meierkord H. , Heinemann U.
Published: December 2017

Schuchmann, S., K. Buchheim, H. Meierkord, and U. Heinemann. A relative energy failure is associated with low-Mg2+but not with 4-aminopyridine induced seizure-like events in entorhinal cortex. J. Neurophysiol. 81: 399–403, 1999. During seizure-like events (SLEs), intracellular Ca2+concentration ([Ca2+]i) increases causing depolarization of the mitochondrial membrane and subsequent intramitochondrial accumulation of Ca2+. Mitochondrial depolarization results in an interruption of oxidative phosphorylation and increase in reactive oxygen species. Calcium activates enzymes of the citrate cycle. A characteristic feature of the low-Mg2+–induced SLEs is that they are transformed to a late activity refractory to anticonvulsant drugs, which may be regarded as a model system of difficult to treat status epilepticus. In contrast, 4-aminopyridine (4-AP)–induced activity rarely evolves to such late activity. The autofluorescence of NAD(P)H was used to monitor changes in cellular energy metabolism in the entorhinal cortex in two in vitro models of focal epilepsy. During repetitive 4-AP–induced SLEs there was a short decrease followed by a long-lasting overshoot of the NAD(P)H signal. This sequence remained unaltered during recurring SLEs. In contrast, during recurrent low-Mg2+–induced SLEs, the brief initial NADH signal reduction was unchanged but the following overshoot of NADH displayed a continuous decrease. This indicates a relative energy failure, which may contribute to the transformation to late activity in the low-Mg2+model.
Gustatory Neural Coding in the Cortex of the Alert Cynomolgus Macaque: The Quality of Bitterness
Authors: Scott Thomas R. , Giza Barbara K. , Yan Jianqun
Published: December 2017

Scott, Thomas R., Barbara K. Giza, and Jianqun Yan. Gustatory neural coding in the cortex of the alert cynomolgus macaque: the quality of bitterness. J. Neurophysiol. 81: 60–71, 1999. We sought to define the gustatory neural representation in primates for stimuli that humans describe as predominantly bitter. Thus we analyzed the responses of single neurons from the insular cortex of two alert, male cynomolgus macaques in response to the oral application of four basic taste stimuli (glucose, NaCl, HCl, and quinine HCl) and fruit juice, and to a series of 15 other chemicals to which humans ascribe a bitter component. Gustatory neurons occupied a volume of 109 mm3 across an area of 4.0 mm in the anterposterior plane, 4.4 mm in the mediolateral, and 6.2 mm in the dorsoventral. Taste cells represented 161 (8.6%) of the 1881 neurons tested for chemical sensitivity. Fifty of these could be monitored throughout the delivery of the entire stimulus series, and their responses constitute the data of this study. The mean spontaneous discharge rate of the cortical gustatory cells was 3.2 ± 3.3 spikes/s (range = 0.2–17.7 spikes/s). The mean breadth-of-tuning coefficient was a moderate 0.77 ± 0.15 (range = 0.25–0.99). Forty-eight neurons responded to taste stimuli with excitation, and two responded with inhibition. Forty-one of the 50 neurons were able to be classified into one of four functional types based on their responses to the four basic stimuli used here. These were sugar ( n = 22), salt ( n = 7), acid ( n = 7), and quinine ( n = 5). A two-dimensional space was generated from correlations among the response profiles elicited by the stimuli array. The 16 bitter chemicals formed a coherent group that was most closely related to HCl, moderately to NaCl, and bore no relationship with glucose. Within the bitter stimuli, six formed a subgroup that was most separated from all nonbitter chemicals: quinine HCl, phenlythiocarbamide, propylthiouracil, caffeine, theophylline, and phenylalanine. Humans describe these stimuli as rather purely bitter. Of the remaining 10 bitter compounds, 4 were on the fringe of the bitter group leading to NaCl: MgCl2, CaCl2, NH4Cl, and arginine. Humans characterize these as bitter-salty. Three were on the fringe leading to HCl: urea, cysteine and vitamin B1. Humans call these bitter-sour. The remaining three (nicotine, histidine, and vitamin B2) occupied the center of the bitter group. Taste quality, inferred from the position of each stimulus in the space, correlated well with human descriptions of the same stimuli, reinforcing the value of the macaque as a neural model for human gustation.
Receptor Mechanisms Underlying Heterogenic Reflexes Among the Triceps Surae Muscles of the Cat
Authors: Nichols T. Richard
Published: December 2017

Receptor mechanisms underlying heterogenic reflexes among the triceps surae muscles of the cat. The soleus (S), medial gastrocnemius (MG), and lateral gastrocnemius (LG) muscles of the cat are interlinked by rapid spinal reflex pathways. In the decerebrate state, these heterogenic reflexes are either excitatory and length dependent or inhibitory and force dependent. Mechanographic analysis was used to obtain additional evidence that the muscle spindle primary ending and the Golgi tendon organ provide the major contributions to these reflexes, respectively. The tendons of the triceps surae muscles were separated and connected to independent force transducers and servo-controlled torque motors in unanesthetized, decerebrate cats. The muscles were activated as a group using crossed-extension reflexes. Electrical stimulation of the caudal cutaneous sural nerve was used to provide a particularly strong activation of MG and decouple the forces of the triceps surae muscles. During either form of activation, the muscles were stretched either individually or in various combinations to determine the strength and characteristics of autogenic and heterogenic feedback. The corresponding force responses, including both active and passive components, were measured during the changing background tension. During activation of the entire group, the excitatory, heterogenic feedback linking the three muscles was found to be strongest onto LG and weakest onto MG, in agreement with previous results concerning the strengths of heteronymous Ia excitatory postsynaptic potentials among the triceps surae muscles. The inhibition, which is known to affect only the soleus muscle, was dependent on active contractile force and was detected essentially as rapidly as length dependent excitation. The inhibition outlasted the excitation and was blocked by intravenous strychnine. These results indicate that the excitatory and inhibitory effects are dominated by feedback from primary spindle receptors and Golgi tendon organs. The interactions between these two feedback pathways potentially can influence both the mechanical coupling between ankle and knee.
Role of Mitochondrial Dysfunction in the Ca2+-Induced Decline of Transmitter Release at K+-Depolarized Motor Neuron Terminals
Authors: Calupca Michelle A. , Hendricks Gregory M. , Hardwick Jean C. , Parsons Rodney L.
Published: December 2017

Role of mitochondrial dysfunction in the Ca2+-induced decline of transmitter release at K+-depolarized motor neuron terminals. The present study tested whether a Ca2+-induced disruption of mitochondrial function was responsible for the decline in miniature endplate current (MEPC) frequency that occurs with nerve-muscle preparations maintained in a 35 mM potassium propionate (35 mM KP) solution containing elevated calcium. When the 35 mM KP contained control Ca2+(1 mM), the MEPC frequency increased and remained elevated for many hours, and the mitochondria within twitch motor neuron terminals were similar in appearance to those in unstimulated terminals. All nerve terminals accumulated FM1–43 when the dye was present for the final 6 min of a 300-min exposure to 35 mM KP with control Ca2+. In contrast, when Ca2+ was increased to 3.6 mM in the 35 mM KP solution, the MEPC frequency initially reached frequencies >350 s− 1 but then gradually fell approaching frequencies <50 s−1. A progressive swelling and eventual distortion of mitochondria within the twitch motor neuron terminals occurred during prolonged exposure to 35 mM KP with elevated Ca2+. After ∼300 min in 35 mM KP with elevated Ca2+, only 58% of the twitch terminals accumulated FM1–43. The decline in MEPC frequency in 35 mM KP with elevated Ca2+ was less when 15 mM glucose was present or when preparations were pretreated with 10 μM oligomycin and then bathed in the 35 mM KP with glucose. When glucose was present, with or without oligomycin pretreatment, a greater percentage of twitch terminals accumulated FM1–43. However, the mitochondria in these preparations were still greatly swollen and distorted. We propose that prolonged depolarization of twitch motor neuron terminals by 35 mM KP with elevated Ca2+ produced a Ca2+-induced decrease in mitochondrial ATP production. Under these conditions, the cytosolic ATP/ADP ratio was decreased thereby compromising both transmitter release and refilling of recycled synaptic vesicles. The addition of glucose stimulated glycolysis which contributed to the maintenance of required ATP levels.
Midbrain Combinatorial Code for Temporal and Spectral Information in Concurrent Acoustic Signals
Authors: Bodnar D. A. , Bass A. H.
Published: December 2017

Midbrain combinatorial code for temporal and spectral Information in concurrent acoustic signals. All vocal species, including humans, often encounter simultaneous (concurrent) vocal signals from conspecifics. To segregate concurrent signals, the auditory system must extract information regarding the individual signals from their summed waveforms. During the breeding season, nesting male midshipman fish ( Porichthys notatus) congregate in localized regions of the intertidal zone and produce long-duration (>1 min), multi-harmonic signals (“hums”) during courtship of females. The hums of neighboring males often overlap, resulting in acoustic beats with amplitude and phase modulations at the difference frequencies (dFs) between their fundamental frequencies ( F0s) and harmonic components. Behavioral studies also show that midshipman can localize a single hum-like tone when presented with a choice between two concurrent tones that originate from separate speakers. A previous study of the neural mechanisms underlying the segregation of concurrent signals demonstrated that midbrain neurons temporally encode a beat’s dF through spike synchronization; however, spectral information about at least one of the beat’s components is also required for signal segregation. Here we examine the encoding of spectral differences in beat signals by midbrain neurons. The results show that, although the spike rate responses of many neurons are sensitive to the spectral composition of a beat, virtually all midbrain units can encode information about differences in the spectral composition of beat stimuli via their interspike intervals (ISIs) with an equal distribution of ISI spectral sensitivity across the behaviorally relevant dFs. Together, temporal encoding in the midbrain of dF information through spike synchronization and of spectral information through ISI could permit the segregation of concurrent vocal signals.
Characterization of K+ Currents Underlying Pacemaker Potentials of Fish Gonadotropin-Releasing Hormone Cells
Authors: Abe Hideki , Oka Yoshitaka
Published: December 2017

Characterization of K+ currents underlying pacemaker potentials of fish gonadotropin-releasing hormone cells. Endogenous pacemaker activities are important for the putative neuromodulator functions of the gonadotropin-releasing hormone (GnRH)-immunoreactive terminal nerve (TN) cells. We analyzed several types of voltage-dependent K+ currents to investigate the ionic mechanisms underlying the repolarizing phase of pacemaker potentials of TN-GnRH cells by using the whole brain in vitro preparation of fish (dwarf gourami, Colisa lalia). TN-GnRH cells have at least four types of voltage-dependent K+currents: 1) 4-aminopyridine (4AP)-sensitive K+current, 2) tetraethylammonium (TEA)-sensitive K+ current, and 3) and 4) two types of TEA- and 4AP-resistant K+ currents. A transient, low-threshold K+ current, which was 4AP sensitive and showed significant steady-state inactivation in the physiological membrane potential range (−40 to −60 mV), was evoked from a holding potential of −100 mV. This current thus cannot contribute to the repolarizing phase of pacemaker potentials. TEA-sensitive K+ current evoked from a holding potential of −100 mV was slowly activating, long lasting, and showed comparatively low threshold of activation. This current was only partially inactivated at steady state of −60 to −40 mV, which is equivalent to the resting membrane potential. TEA- and 4AP-resistant sustained K+ currents were evoked from a holding potential of −100 mV and were suggested to consist of two types, based on the analysis of activation curves. From the inactivation and activation curves, it was suggested that one of them with low threshold of activation may be partly involved in the repolarizing phase of pacemaker potentials. Bath application of TEA together with tetrodotoxin reversibly blocked the pacemaker potentials in current-clamp recordings. We conclude that the TEA-sensitive K+ current is the most likely candidate that contributes to the repolarizing phase of the pacemaker potentials of TN-GnRH cells.