bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of Stimulus-Dependent Correlated Activity in the Dorsal Cochlear Nucleus of Decerebrate Gerbils
Authors: Davis Kevin A. , Voigt Herbert F.
Published: December 2017

Davis, Kevin A. and Herbert F. Voigt. Evidence of stimulus-dependent correlated activity in the dorsal cochlear nucleus of decerebrate gerbils. J. Neurophysiol. 78: 229–247, 1997. Cross-correlation analysis of simultaneously recorded spike trains was used to study the internal organization of the dorsal cochlear nucleus (DCN) of unanesthetized decerebrate Mongolian gerbils. The goal was to test the model (adapted from cat) that its principal cells (type III and type IV units) receive three sources of shared auditory input: excitatory input from the auditory nerve; inhibitory input from DCN interneurons (vertical cells; type II and typeIII-i units) that respond vigorously to tones; and inhibitory input from ventral cochlear nucleus principal cells (D-stellate cells; wideband inhibitors) that conversely respond vigorously to noise. Records of spontaneous and/or driven activities (to long-duration tones and frozen broadband noise) were obtained for 51 pairs consisting of type II, type III, and type IV units; type III units inhibited by low-level noise were subclassified as type III-i units. Pairs were isolated with two electrodes to study the effect of differences in unit best frequencies (BFs) on correlation. All correlated pairs composed of type III and type IV units (17 of 31 pairs) showed central mounds (CMs), indicative of shared input, in their cross-correlograms. These data exhibited two important properties: pairs with similar BFs were more likely to show CMs, and the shape of the CMs was stimulus dependent. That is, CM width typically changed sharply from wide to narrow with increasing level; significantly, transition-level CMs were either a composite of these shapes or not present. The transition to only narrow CMs occurred above the thresholds of type II and type III-i units to tones, but below their thresholds to noise. Cross-correlograms derived from the tone-evoked activities of pairs involving type II units (3 of 6 pairs) showed inhibitory troughs (ITs); unexpectedly, type III-i units were involved in both IT and CM pairs, suggesting that this unit type may reflect recordings from both vertical and principal cells. Overall, the results are interpretable in terms of the model of gerbil DCN that was adapted from cat, suggesting that the model generalizes across species. Compared with cat, however, gerbil principal cell responses (predominantly type III unit properties) are less dominated by inhibition.
Mechanical Responses to Two-Tone Distortion Products in the Apical and Basal Turns of the Mammalian Cochlea
Authors: Cooper N. P. , Rhode W. S.
Published: December 2017

Cooper, N. P. and W. S. Rhode. Mechanical responses to two-tone distortion products in the apical and basal turns of the mammalian cochlea. J. Neurophysiol. 78: 261–270, 1997. Mechanical responses to one- and two-tone acoustic stimuli were recorded from the cochlear partition in the apical turn of the chinchilla cochlea, the basal turn of the guinea pig cochlea, and the hook region of the guinea pig cochlea. The most sensitive or “best” frequencies (BFs) for the sites studied were ∼500 Hz, 17 kHz, and 30 kHz, respectively. Responses to the cubic difference tone (CDT), 2 F 1 − F 2 (where F 1 and F 2 are the frequencies of the primary stimuli), were characterized at each site. Responses to the quadratic difference tone (QDT), F 2 − F 1, were also characterized in the apical turn preparations (QDT responses were too small to measure in the basal cochlea). The observed responses to BF QDTs and CDTs and to BF CDTs at each site appeared similar in many ways; the relative magnitudes of the responses were highest at low-to-moderate sound pressure levels (SPLs), for example, and the absolute magnitudes grew nonmonotonically with increases in the level of either primary ( L 1 or L 2) alone. The peak effective levels of the CDT and QDT responses were also similar, at around −20 dB re L 1 and/or L 2. In other respects, however, the responses to CDTs and QDTs and to BF CDTs at each site behaved quite differently. At low-to-moderate SPLs, for example, most CDT phase leads decreased with increases in either L 1 or L 2, whereas most QDT phase leads increased with increasing L 1 and varied little with L 2. Most CDT responses also varied monotonically with equal-level primaries (i.e., when L 1 = L 2), whereas most QDT responses varied nonmonotonically. Different responses also varied in different ways when F 1 and F 2 were varied. Apical turn QDT responses were observed over a very wide F 1/ F 2 range ( F 1 =1–12 kHz), but were usually largest for stimuli <2–4 kHz. Apical turn CDT levels decreased (at rates of ∼40–80 dB/octave) only when the frequency ratio F 2/ F 1 increased beyond ∼1.4–1.5. In the basal turn and hook regions, the CDT levels depended nonmonotonically on F 2/ F 1, with the eventual rates of decrease being ∼200 dB/octave. Optimal frequency ratios for the CDT increased from ( F 2 < 1.1 F 1) to ( F 2 ≈ 1.2 F 1) with increasing SPL in the basal turn, but were stable at around F 2/ F 1 ≈ 1.05 in the hook region. CDT phase leads tended to increase with increasing F 2/ F 1 in all three regions of the cochlea, particularly at low-to-moderate SPLs. These findings are discussed in relation to previous studies of cochlear mechanics, physiology, and psychophysics.
Cannabinoids Inhibit N- and P/Q-Type Calcium Channels in Cultured Rat Hippocampal Neurons
Authors: Twitchell W. , Brown S. , Mackie K.
Published: December 2017

Twitchell, W., S. Brown, and K. Mackie. Cannabinoids inhibit N- and P/Q-type calcium channels in cultured rat hippocampal neurons. J. Neurophysiol. 78: 43–50, 1997. Cannabinoids and their analogues have been found to inhibit N- and P/Q-type Ca2+ currents in cell lines and sympathetic neurons transfected with cannabinoid CB1 receptor. However, the effects of cannabinoids on Ca2+ currents in the CNS are largely unexplored. In this study we investigated whether these compounds inhibit Ca2+ channels in cultured rat hippocampal neurons. With the use of antibodies directed against the amino-terminus of the CB1 receptor, we found that in 5-day cultures pyramidally shaped neurons expressed somatic CB1 receptors, whereas in 4-wk cultures the receptor was predomintely located on neurites. In early cultures, the cannabimimetic WIN 55,212-2 reversibly inhibited whole cell Ba2+ current in a concentration-dependent ( K 1/2 = 21 nM) and pertussis-toxin-sensitive fashion. Inhibition was reduced by the CB1 antagonist SR141716. The current was unaffected by the nonpsychoactive enantiomer WIN 55,212-3. Maximal inhibition by the nonclassical cannabinoid agonist CP 55,940 and by an endogenous cannabinoid, anandamide, were similar to that seen with maximal concentrations of WIN 55,212-2. The Ba2+ current modulated by cannabinoids was carried by N-type (ω-conotoxin-GVIA-sensitive) and P/Q-type (ω-conotoxin-MVIIC-sensitive) channels. These results demonstrate cannabinoid-receptor-mediated inhibition of distinct Ca2+ channels in central neurons. Because the channels that underlie these currents are chiefly located presynaptically, and are required for evoked neurotransmitter release, our results suggest a major role for cannabinoids (endogenous and exogenous) in the modulation of synaptic transmission at CNS synapses.
Postnatal Development of Ionic Currents in Rat Hippocampal Astrocytes In Situ
Authors: Bordey Angélique , Sontheimer Harald
Published: December 2017

Bordey, Angélique and Harald Sontheimer. Postnatal development of ionic currents in rat hippocampal astrocytes in situ. J. Neurophysiol. 78: 461–477, 1997. Developmental changes in ion channel expression and cell morphology were studied in glial cells with the use of whole cell patch-clamp recordings in rat [postnatal day (P)5–P50] hippocampal slices. Recordings were obtained from 234 cells, presumed to be glia, in stratum radiatum and stratum lacunosum-moleculare of the CA1 region. Of 66 recorded cells filled with Lucifer yellow, 48 stained positive for glial fibrillary acidic protein, which identified them as astrocytes. All glial cells studied were of a stellate morphology, and developmental changes primarily comprised an increase in the length and number of cell processes associated with an overall increase in cell size and membrane capacitance. Two distinct outward potassium currents could be identified: a transient 4-aminopyridine-sensitive current ( I a) and a persistent outward current sensitive to tetraethylammonium ( I d). I a activated at −40 mV, and steady-state activation and inactivation midpoints were −16 and −74 mV, respectively. Decay time constants ranged from 7 ms at −30 mV to 19 ms at +80 mV. I d activated at −30 mV. A third K+ current sensitive to cesium activated with hyperpolarizing command voltages and showed strong inward rectification. Transient, voltage-activated sodium currents ( I Na) were tetrodotoxin sensitive (100 nM) and activated at about −40 mV, peaked at about −10 mV, and reversed at +63 mV. I Na was half-inactivated at −49 mV and half-activated at −19 mV. During the first 2 wk of postnatal development, the percentage of cells showing inwardly rectifying K+ current ( I r), I a, and I Na increased significantly from 40% (at P5) to 90% (at P20–P50). By contrast, almost all cells independent of age expressed I d. Specific conductances for I r ( g ir) and I a increased significantly between P5 and P20, concomitant with a decrease in input resistance. By contrast, specific conductance of the outwardly rectifying K+ current ( g d) decreased threefold between P5 and P20. Specific Na+ conductance was always <1/4 of the total potassium conductance. These results indicate that CA1 hippocampal astrocytes are characterized by expression of voltage-activated Na+ channels and three types of K+ channels showing changes in their relative expression during early postnatal development: 1) the number of cells expressing I a, I r, and I Na increases significantly and 2) their specific conductance changes such that g d, predominant at P5–P20, is gradually replaced by g ir, the predominant conductance in adult astrocytes. Adult morphological and electrophysiological phenotypes are established at about P20. These data suggest that previous studies in which cultured or acutely isolated cells from immature or embryonic rats were used were not adequately reflecting the properties of hippocampal astrocytes in situ.
Relationship of Cerebellar Purkinje Cell Simple Spike Discharge to Movement Kinematics in the Monkey
Authors: Fu Q.-G. , Flament D. , Coltz J. D. , Ebner T. J.
Published: December 2017

Fu, Q.-G., D. Flament, J. D. Coltz, and T. J. Ebner. Relationship of cerebellar Purkinje cell simple spike discharge to movement kinematics in the monkey. J. Neurophysiol. 78: 478–491, 1997. The simple spike discharge of 231 cerebellar Purkinje cells in ipsilateral lobules V and VI was recorded in three monkeys trained to perform a visually guided reaching task requiring movements of different directions and distances. The discharge of 179 cells was significantly modulated during movement to one or more targets. Mean simple spike rate was fitted to a cosine function for direction tuning, a simple linear function for distance modulation, and a multiple linear regression model that included terms for direction, distance, and target position. On the basis of the fit to the direction and distance models, there were more distance-related than direction-related Purkinje cells. The simple spike discharge of most direction-related cells modulated at only one target distance. The preferred directions for the simple spike tuning were not uniformly distributed across the workspace. The discharge of most distance-related cells modulated along only one movement direction. On the basis of the multiple linear regression model, simple spike discharge was also correlated with target position, in addition to direction and distance. Approximately half of the Purkinje cells had simple spike activity associated with only a single parameter, and only a small fraction of the cells with all three. The multiple regression model was extended to evaluate the correlations as a function of time. Considerable overlap occurred in the timing of the simple spike correlations with the parameters. The latency for correlation with movement direction occurred mainly in a 500-ms interval centered on movement onset. The correlations with target position also occurred around movement onset, in the range of −200–500 ms. Distance correlations were more variable, with onset latencies from −500 to 1,000 ms. These results demonstrate that the simple spike discharge of cerebellar Purkinje cells is correlated with movement direction, distance, and target position. Comparing these results to motor cortical discharge shows that the correlations with these parameters were weaker in Purkinje cell simple spike discharge, and that, for the majority of Purkinje cells, the simple spike discharge was significantly related to only a single movement parameter. Other differences between simple spike responses and those of motor cortical cells include the nonuniform distribution of preferred directions and the extensive overlap in the timing of the correlations. These differences suggest that Purkinje cells process, encode, and use kinematic information differently than motor cortical neurons.
Neurons Sensitive to Interaural Temporal Disparities in the Medial Part of the Ventral Nucleus of the Lateral Lemniscus
Authors: Batra Ranjan , Fitzpatrick Douglas C.
Published: December 2017

Batra, Ranjan and Douglas C. Fitzpatrick. Neurons sensitive to interaural temporal disparities in the medial part of the ventral nucleus of the lateral lemniscus. J. Neurophysiol. 78: 511–515, 1997. The ventral nucleus of the lateral lemniscus (VNLL) is implicated in processing monaural sounds, because its neurons receive input chiefly from the contralateral cochlear nucleus. However, we demonstrate here that a region of the VNLL contains a distinct population of neurons that process binaural sounds and are sensitive to interaural temporal disparities (ITDs). Responses of single neurons were recorded from unanesthetized rabbits by using metal electrodes or micropipettes loaded with dextran tagged with either biotin or a fluorescent label. Reconstructions of recording sites based on a few marks indicated that ITD-sensitive neurons were located in a medial region of VNLL that has a low density of neurons or in the adjacent reticular formation. In one animal the locations of five ITD-sensitive neurons were marked directly by injection of dextrans with different tags. All of these neurons lay in the medial region of the VNLL. The ITD-sensitive neurons of the VNLL had characteristic responses. Most neurons responded only at the onset of contralaterally or binaurally presented tones; many did not respond to ipsilateral stimulation alone and did not follow dynamic changes in the ITD. The presence of ITD-sensitive neurons in the VNLL that responded only at the onset of tones suggests that this center plays a role in the localization of transient sounds.
GABAB-Receptor-Mediated Inhibition in Developing Mouse Ventral Posterior Thalamic Nucleus
Authors: Warren Richard A. , Golshani Peyman , Jones Edward G.
Published: December 2017

Warren, Richard A., Peyman Golshani, and Edward G. Jones. GABAB-receptor-mediated inhibition in developing mouse ventral posterior thalamic nucleus. J. Neurophysiol. 78: 549–553, 1997. Inhibitory postsynaptic potentials (IPSPs) generated by activation of the thalamic reticular nucleus (RTN) were recorded in neurons of the ventral posterior nucleus (VP) in vitro in slices from mice aged postnatal day (P)1–P17. An early IPSP peaking 41 ± 2.5 (SE) ms after electrical stimulation of the internal capsule or RTN was found in 96% of VP neurons. This early IPSP was blocked by bicuculline, showing its dependence on γ-aminobutyric acid-A (GABAA) receptors. A late IPSP peaking 357 ± 27 ms after the stimulus was observed in 22% of VP neurons in control medium but was uncovered in 38% of neurons when bicuculline was added. The late IPSP was blocked by addition of a GABAB antagonist, 2-hydroxysaclofen, to the medium ( n = 7); it had a reversal potential of −98 ± 1.3 mV, 14 mV negative to the early component. In contrast to the early IPSP, whose reversal potential became more negative during postnatal development, the reversal potential of the late IPSP remained constant throughout the postnatal period studied. The most significant change in the late IPSP was shortening in duration, with reduction in latency-to-peak by >400 ms, between P1 and P10. No changes of comparable magnitude were observed in the duration of the earlier GABAA response. These results show that both GABAA and GABAB IPSPs are present very early in the postnatal thalamus and that their characteristics evolve along independent paths during postnatal development.
Adrenoceptor-Mediated Elevation of Ambient GABA Levels Activates Presynaptic GABAB Receptors in Rat Sensorimotor Cortex
Authors: Bennett Ben D. , Huguenard John R. , Prince David A.
Published: December 2017

Bennett, Ben D., John R. Huguenard, and David A. Prince. Adrenoceptor-mediated elevation of ambient GABA levels activates presynaptic GABAB receptors in rat sensorimotor cortex. J. Neurophysiol. 78: 561–566, 1997. At inhibitory synapses in the mature neocortex and hippocampus in vitro, spontaneous action-potential-dependent and -independent release of γ-aminobutyric acid (GABA) activates postsynaptic GABAA receptors but not pre- or postsynaptic GABAB receptors. Elevation of synaptic GABA levels with pharmacological agents or electrical stimulation can cause activation of GABAB receptors, but the physiological conditions under which such activation occurs need further elucidation. In rodent sensorimotor cortex, epinephrine produced a depression in the amplitude of evoked monosynaptic inhibitory postsynaptic currents (IPSCs) and a concomitant, adrenoceptor-mediated increase in the frequency of spontaneous IPSCs. Blockade of GABAB receptors prevented the depression of evoked IPSC amplitude by epinephrine but did not affect the increase in spontaneous IPSC frequency. These data show that adrenoceptor-mediated increases in spontaneous IPSCs can cause activation of presynaptic GABAB receptors and indirectly modulate impulse-related GABA release, presumably through elevation of synaptic GABA levels.
Mechanisms Underlying the Chronotropic Effect of Angiotensin II on Cultured Neurons From Rat Hypothalamus and Brain Stem
Authors: Wang Desuo , Gelband Craig H. , Sumners Colin , Posner Philip
Published: December 2017

Wang, Desuo, Craig H. Gelband, Colin Sumners, and Philip Posner. Mechanisms underlying the chronotropic effect of angiotensin II on cultured neurons from rat hypothalamus and brain stem. J. Neurophysiol. 78: 1013–1020, 1997. The chronotropic effect of angiotensin II (Ang II) was studied in cultured neurons from rat hypothalamus and brain stem with the use of the patch-clamp technique. Ang II (100 nM) increased the neuronal spontaneous firing rate from 0.8 ± 0.3 (SE) Hz in control to 1.3 ± 0.4 Hz ( n = 7, P < 0.05). The amplitude of threshold stimulation was decreased by Ang II (100 nM) from 82 ± 4 pA to 62 ± 5 pA ( n = 4, P < 0.05). These actions of Ang II were reversed by the angiotensin type 1 (AT1) receptor antagonist losartan (1 μM). In the presence of tetrodotoxin, Ang II (100 nM) significantly increased the frequency and the amplitude of the Cd2+-sensitive subthreshold activity of the cultured neurons. Ang II also stimulated the subthreshold early afterdepolarizations (EADs) to become fully developed action potentials. Similar to the action of Ang II, the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA, 100 nM) increased the firing rate from 0.76 ± 0.3 Hz to 2.3 ± 0.5 Hz ( n = 6, P < 0.05) and increased the neuronal subthreshold activity. After neurons were intracellularly dialyzed with PKC inhibitory peptide (PKCIP, 5 μM), PMA alone, Ang II alone, or PMA plus Ang II no longer increased the action potential firing initiated from the resting membrane potential level. However, superfusion of PMA plus Ang II or Ang II alone increased the number of EADs that reached threshold and produced action potentials even in the presence of PKCIP (5 μM, n = 4). The actions of Ang II could also be mimicked by depolarizing pulse and K+ channel blockers (tetraethylammonium chloride or 4-aminopyridine). These results indicate that Ang II by activation of AT1 receptors increases neuronal excitability and firing frequency, and that this may involve both PKC dependent and-independent mechanisms.
Effect of Remote Distractors on Saccade Programming: Evidence for an Extended Fixation Zone
Authors: Walker Robin , Deubel Heiner , Schneider Werner X. , Findlay John M.
Published: December 2017

Walker, Robin, Heiner Deubel, Werner X. Schneider, and John M. Findlay. Effect of remote distractors on saccade programming: evidence for an extended fixation zone. J. Neurophysiol. 78: 1108–1119, 1997. In a series of experiments, we examined the increase in saccade latency that is observed consistently when distractor stimuli are presented simultaneously with the saccade target at various nontarget locations. In the first experiment, targets and distractors were presented on the horizontal axis. We found that saccade latency was increased when distractors appeared at fixation and in the contralateral nontarget hemifield (at eccentricities ≤10°). In contrast, latency was unaffected by distractors presented along the ipsilateral target axis, but amplitude was increased as saccades tended to land at intermediate locations between the two stimuli (global effect). The effect of presenting distractors at various two-dimensional locations in both the target and nontarget hemifields then was examined, and the maximum latency increase again was observed when distractors appeared at fixation. Distractors presented on any of the eight principal axes in either hemifield, other than on the horizontal target axis, also increased latency. The relationship between the effects of distractors on latency and amplitude was reciprocal. Within ∼20° of the target axis itself, distractors affected saccade amplitude but not latency. In contrast, distractors presented outside this “window” increased saccade latency without affecting amplitude. A systematic quantitative relationship was revealed between the increase in latency and the ratio between target and distractor eccentricities. The latency increase was largest with small values of the ratio and reached a peak with distractors at the fixation location. The finding that the increase observed for more eccentric distractor locations fitted the same function as that at fixation shows that inhibitory effects operate over large areas of the visual field. The increase in latency under distractor conditions is interpreted in light of recent neurophysiological findings of inhibitory processes operating in the rostral region of the superior colliculus. Our results suggest that these inhibitory processes are not restricted to the central foveal region alone but operate over wider regions of the visual field.
N-Methyl-d-Aspartate Evokes Rapid Net Depolymerization of Filamentous Actin in Cultured Rat Cerebellar Granule Cells
Authors: Shorte Spencer L.
Published: December 2017

Shorte, Spencer L. N-methyl-d-aspartate evokes rapid net depolymerization of filamentous actin in cultured rat cerebellar granule cells. J. Neurophysiol. 78: 1135–1143, 1997. Filamentous actin(F-actin) was measured in cultured rat cerebellum granule neurons with the use of fluorescently labeled phallotoxin as a site-specific probe for F-actin, and fluorescence microscopy. The averaged apparent intensity of soma-associated F-actin-derived fluorescence ( Fapp) was measured from fixed cells after incubation in either 1) normal Krebs solution containing 2 mM extracellular calcium ([Ca2+]ex) or 2) normal Krebs solution plus N-methyl-d-aspartate (NMDA) for 2 min immediately before fixation. NMDA (10, 50, and 100 μM) decreased Fappto 63 ± 5% (mean ± SE), 53 ± 4%, and 47 ± 2%, respectively, of that measured from control cells. This effect was mimicked by treatment of cells with ionomycin. The ability of NMDA to reduce the Fappin the presence of [Ca2+]ex was abolished when cells were maintained in [Ca2+]ex-free medium. Cells first treated with NMDA for 2 min and then left in normal medium for 30 min before fixation gave Fappfluorescence similar to control values (91 ± 12%). However, if the F-actin polymerization inhibitor cytochalasin D was added to cells immediately after NMDA was removed, the Fappdid not recover with time (36 ± 3%). Cells treated for 30 min with cytochalasin D alone showed a small reduction in staining (∼20%). It is concluded that the actin polymerization state of rat cerebellar granule neurons is sensitive to changes in intracellular calcium, and that NMDA receptor activation evokes an initial rapid depolymerization of F-actin.
Regional Variability of Stretch Reflex Amplitude in the Cat Medial Gastrocnemius Muscle During a Postural Task
Authors: Eng Janice J. , Hoffer J. A.
Published: December 2017

Eng, Janice J. and J. A. Hoffer. Regional variability of stretch reflex amplitude in the cat medial gastrocnemius muscle during a postural task. J. Neurophysiol. 78: 1150–1154, 1997. The relationship between local fibre stretch velocity (mechanical input) and the corresponding local reflex electromyographic (EMG) amplitude (a measure of the neural output) was assessed to determine the contribution of muscle spindle feedback in postural control. We hypothesized that traditionally measured input variables (e.g., the velocity of an external movement or whole muscle velocity) may not accurately represent the mechanical input to the muscle spindles, especially when the background forces are small. Three cats were trained to stand on pedestals while ankle rotations were applied to the left hindlimb. EMG and fiber movement in both proximal and distal regions of the muscle were recorded in addition to muscle length and tendon force. We found that local muscle velocity was correlated poorly with whole muscle velocity, demonstrating that internal and external muscle movements are often dissimilar, particularly during tasks that involve modest levels of muscle activation. Local EMG reflex amplitudes were correlated well with the corresponding local fiber stretch velocities ( R values ranging from 0.5 to 0.8) but not with muscle stretch velocity. The lack of crossed correlations between fiber stretch velocities and reflex EMG amplitudes measured in proximal versus distal regions of the muscle suggests the presence of a local reflex component. It is concluded that changes in local muscle fiber length represent the mechanical input to spindles better than changes in the total muscle length. Additionally, spindles have a specific role in the reflex activation of nearby muscle fibers.
Subcortical Modulation of High-Frequency (Gamma Band) Oscillating Potentials in Auditory Cortex
Authors: Brett Barbara , Barth Daniel S.
Published: December 2017

Brett, Barbara and Daniel S. Barth. Subcortical modulation of high-frequency (gamma band) oscillating potentials in auditory cortex. J. Neurophysiol. 78: 573–581, 1997. The purpose of this study was to use depth electrical stimulation and retrograde horseradish peroxidase (HRP) labeling to determine what role certain subcortical nuclei play in the neurogenesis of high-frequency gamma (∼40 Hz) oscillations in rat auditory cortex. Evoked and spontaneous electrocortical oscillations were recorded with the use of a high-spatial-resolution multichannel epipial electrode array while electrical stimulation was delivered to the posterior intralaminar (PIL) region of the ventral acoustic thalamus and to the centrolateral nucleus (CL) and the nucleus basalis (NB), which have been previously implicated in the production of cortical gamma oscillations. PIL stimulation consistently evoked gamma oscillations confined to a location between primary and secondary auditory cortex, corresponding to the region where spontaneous gamma oscillations were also recorded. Stimulation of the CL and NB did not evoke gamma oscillations in auditory cortex. HRP placed in the cortical focus of evoked gamma oscillations labeled cell bodies in the PIL, and in more lateral regions of the ventral acoustic thalamus, which on subsequent stimulation also evoked gamma oscillations in auditory cortex. No cells were labeled in either the CL or NB. These results indicate that the PIL and the lateral regions of ventral acoustic thalamus provide anatomically distinct input to auditory cortex and may play an exclusive and modality-specific role in modulating gamma oscillations in the auditory system.
Linear and Nonlinear Spectral Integration in Type IV Neurons of the Dorsal Cochlear Nucleus. I. Regions of Linear Interaction
Authors: Nelken Israel , Young Eric D.
Published: December 2017

Nelken, Israel and Eric D. Young. Linear and nonlinear spectral integration in type IV neurons of the dorsal cochlear nucleus. I. Regions of linear interaction. J. Neurophysiol. 78: 790–799, 1997. The principal neurons of the dorsal cochlear nucleus have complex response properties, many of which are classified as type IV. These units integrate energy in the acoustic signal in a nonlinear fashion; for example, at high sound levels the response to a noise of narrow bandwidth and to a band-reject filtered noise with a spectral notch of the same bandwidth may both be inhibitory. However, the sum of these two stimuli, which is broadband noise (BBN), generally gives an excitatory response. In other situations, linear interactions among stimulus components are observed. In this paper, three regimes of approximate linearity were identified. First, best-frequency (BF) tones and equal-energy narrow noisebands centered at BF evoke almost the same response, which is consistent with a stage of linear filtering followed by a nonlinearity that generates the rate responses of the neuron. Second, for sounds close to threshold (10–15 dB re threshold), energy over the full bandwidth of the unit is integrated linearly. Within this regime, responses to the narrow noiseband and the spectral notch mentioned above do sum to equal the response to BBN. Finally, two noisebands centered at different frequencies, such that their sum is a notch in a broad band of noise, sum linearly at low sound levels; the degree of linearity improves as the separation between the noisebands increases. The results are interpreted in terms of a model of type IV response generation containing two inhibitory interneurons: type II units, which are active for narrowband stimuli, including tones, and the wideband inhibitor, which is active for broadband stimuli. In most cases, the onset of nonlinearity occurs for stimuli that significantly activate the type II inhibitory interneuron.
Evolution of Anisotropic Diffusion in the Developing Rat Corpus Callosum
Authors: Voříšek Ivan , Syková Eva
Published: December 2017

Vořı́šek, Ivan and Eva Syková. Evolution of anisotropic diffusion in the developing rat corpus callosum. J. Neurophysiol. 78: 912–919, 1997. Diffusion anisotropy was investigated in the developing rat brain [postnatal day (P)6–29] with the use of ion-selective microelectrodes to measure the three-dimensional distribution of tetramethylammonium (TMA+) iontophoresed into the extracellular space (ECS). The diffusion parameters, ECS volume fraction α (α = ECS volume/total tissue volume), tortuosity λ (λ2 = apparent diffusion coefficient/free diffusion coefficient), and nonspecific TMA+ uptake ( k′), were studied in cortical gray matter (layer V) and corpus callosum (CC) of anesthetized rats. ECS volume fraction in cortex and CC was about twice as large in the newborn rat as in adults. In this study, more detailed analysis revealed that α in CC gradually decreased from P4, when α ranged between 0.42 and 0.45, and reached a final value of 0.26 ± 0.01 (SE, n = 12 measurements, 6 animals) at about P21. Diffusion in the ECS of CC was isotropic until about P12, i.e., there was no significant difference in the tortuosity factor, λ, between the three perpendicular axes. From P13 to P17 anisotropy greatly increased as a result of preferential diffusion along the myelinated axons ( X-axis). At P21–23 the tortuosity values were λ x = 1.46 ± 0.03, λ y  = 1.70 ± 0.01, and λ z = 1.72 ± 0.02 ( n = 12), and there were no further changes up to the last postnatal day studied, P29. In contrast to the myelinated CC, cortical gray matter remained isotropic up to P29, with a tortuosity of 1.54 ± 0.02 ( n = 12). The results suggest that diffusion anisotropy in the rat CC is related to myelination; it reaches a maximum at P17, when myelination is well advanced. In myelinated pathways, preferential diffusion of ions and transmitters occurs along the axons. These results are relevant to volume transmission and the interpretation of diffusion-weighted magnetic resonance imaging.
Frontal and Parietal Networks for Conditional Motor Learning: A Positron Emission Tomography Study
Authors: Deiber M.-P. , Wise S. P. , Honda M. , Catalan M. J. , Grafman J. , Hallett M.
Published: December 2017

Deiber, M.-P., S. P. Wise, M. Honda, M. J. Catalan, J. Grafman, and M. Hallett. Frontal and parietal networks for conditional motor learning: a positron emission tomography study. J. Neurophysiol. 78: 977–991, 1997. Studies on nonhuman primates show that the premotor (PM) and prefrontal (PF) areas are necessary for the arbitrary mapping of a set of stimuli onto a set of responses. However, positron emission tomography (PET) measurements of regional cerebral blood flow (rCBF) in human subjects have failed to reveal the predicted rCBF changes during such behavior. We therefore studied rCBF while subjects learned two arbitrary mapping tasks. In the conditional motor task, visual stimuli instructed which of four directions to move a joystick (with the right, dominant hand). In the evaluation task, subjects moved the joystick in a predetermined direction to report whether an arrow pointed in the direction associated with a given stimulus. For both tasks there were three rules: for the nonspatial rule, the pattern within each stimulus determined the correct direction; for the spatial rule, the location of the stimulus did so; and for the fixed-response rule, movement direction was constant regardless of the pattern or its location. For the nonspatial rule, performance of the evaluation task led to a learning-related increase in rCBF in a caudal and ventral part of the premotor cortex (PMvc, area 6), bilaterally, as well as in the putamen and a cingulate motor area (CM, area 24) of the left hemisphere. Decreases in rCBF were observed in several areas: the left ventro-orbital prefrontal cortex (PFv, area 47/12), the left lateral cerebellar hemisphere, and, in the right hemisphere, a dorsal and rostral aspect of PM (PMdr, area 6), dorsal PF (PFd, area 9), and the posterior parietal cortex (area 39/40). During performance of the conditional motor task, there was only a decrease in the parietal area. For the spatial rule, no rCBF change reached significance for the evaluation task, but in the conditional motor task, a ventral and rostral premotor region (PMvr, area 6), the dorsolateral prefrontal cortex (PFdl, area 46), and the posterior parietal cortex (area 39/40) showed decreasing rCBF during learning, all in the right hemisphere. These data confirm the predicted rCBF changes in premotor and prefrontal areas during arbitrary mapping tasks and suggest that a broad frontoparietal network may show decreased synaptic activity as arbitrary rules become more familiar.
Sensitivity to Interaural Temporal Disparities of Low- and High-Frequency Neurons in the Superior Olivary Complex. I. Heterogeneity of Responses
Authors: Batra Ranjan , Kuwada Shigeyuki , Fitzpatrick Douglas C.
Published: December 2017

Batra, Ranjan, Shigeyuki Kuwada, and Douglas C. Fitzpatrick. Sensitivity to interaural temporal disparities of low- and high-frequency neurons in the superior olivary complex. I. Heterogeneity of responses. J. Neurophysiol. 78: 1222–1236, 1997. Interaural temporal disparities (ITDs) are a cue for localization of sounds along the azimuth. Listeners can detect ITDs in the fine structure of low-frequency sounds and also in the envelopes of high-frequency sounds. Sensitivity to ITDs originates in the main nuclei of the superior olivary complex (SOC), the medial and lateral superior olives (MSO and LSO, respectively). This sensitivity is believed to arise from bilateral excitation converging on neurons of the MSO and ipsilateral excitation converging with contralateral inhibition on neurons of the LSO. Here we investigate whether the sensitivity of neurons in the SOC to ITDs can be adequately explained by one of these two mechanisms. Single and multiple units ( n = 124) were studied extracellularly in the SOC of unanesthetized rabbits. We found units that were sensitive to ITDs in the fine structure of low-frequency (<2 kHz) tones and also units that were sensitive to ITDs in the envelopes of sinusoidally amplitude-modulated high-frequency tones. For both categories there were “peak-type” units that discharged maximally at a particular ITD across frequencies or modulation frequencies. These units were consistent with an MSO-type mechanism. There were also “trough-type” units that discharged minimally at a particular ITD. These units were consistent with an LSO-type mechanism. There was a general trend for peak-type units to be located in the vicinity of the MSO and for trough-type units to be located in the vicinity of the LSO. Units of both types appeared to encode ITDs within the estimated free-field range of the rabbit (±300 μs). Many units had varying degrees of irregularities in their responses, which manifested themselves in one of two ways. First, for some units there was no ITD at which the response was consistently maximal or minimal across frequencies. Instead there was an ITD at which the unit consistently responded at some intermediate level. Second, a unit could display considerable jitter from frequency to frequency in the ITD at which it responded maximally or minimally. Units with irregular responses had properties that were continuous with those of other units. They therefore appeared to be variants of peak- and trough-type units. The irregular responses could be modeled by assuming additional phase-locked inputs to a neuron in the MSO or LSO. The function of irregularities may be to shift the ITD sensitivity of a neuron without requiring changes in the anatomic delays of its inputs.
Inhibition of Bradykinin-Induced Plasma Extravasation Produced by Noxious Cutaneous and Visceral Stimuli and Its Modulation by Vagal Activity
Authors: Miao Frederick Jia-Pei , Jänig Wilfrid , Green Paul G. , Levine Jon D.
Published: December 2017

Miao, Frederick Jia-Pei, Wilfrid Jänig, Paul G. Green, and Jon D. Levine. Inhibition of bradykinin-induced plasma extravasation produced by noxious cutaneous and visceral stimuli and its modulation by vagal activity. J. Neurophysiol. 78: 1285–1292, 1997. Intrathecally applied nicotine reduces bradykinin-induced plasma extravasation (BK-induced PE) in the rat knee joint. This depression is mediated by the hypothalamo-pituitary-adrenal (HPA) axis and is enhanced by interruption of impulse traffic in afferents of the abdominal vagus nerve. Like intrathecal nicotine, electrical stimulation of unmyelinated cutaneous fibers also depresses BK-induced PE, which is also dependent on an intact HPA axis. In this study, we investigated whether the inhibitory effect of intrathecal nicotine can be mimicked by noxious stimulation of skin and of viscera. Furthermore we determined whether this depression is potentiated after subdiaphragmatic vagotomy. Stimulation of visceral afferents in the peritoneum, by intraperitoneal capsaicin injection, dose-dependently decreased BK-induced PE. The capsaicin dose-response function was shifted by 1.5–2 orders of magnitude to the left after vagotomy. Stimulation of visceral afferents in the urinary bladder by capsaicin also dose-dependently reduced BK-induced PE, which similarly was potentiated after vagotomy. Transcutaneous stimulation of unmyelinated nociceptive afferents from the plantar skin of the paw depressed BK-induced PE. This depression had a threshold of ∼0.25 Hz and was maximal at a stimulation frequency of ∼1 Hz. After subdiaphragmatic vagotomy, the stimulus response function shifted to the left and the inhibition was significantly larger than in control, in the range of 0.125–1 Hz stimulation. These results show that noxious stimulation of skin and viscera depressed BK-induced PE and that such depression was potentiated after subdiaphragmatic vagotomy in a manner similar to that of intrathecally applied nicotine. Based on these observations, we hypothesize that intrathecal nicotine depresses BK-induced PE by exciting spinal nociceptive neurons or the central projections of nociceptive primary afferent neurons.
Calcium Channel Subtypes in Lamprey Sensory and Motor Neurons
Authors: Manira A. El , Bussières N.
Published: December 2017

El Manira, A. and N. Bussières. Calcium channel subtypes in lamprey sensory and motor neurons. J. Neurophysiol. 78: 1334–1340, 1997. Pharmacologically distinct calcium channels have been characterized in dissociated cutaneous sensory neurons and motoneurons of the larval lamprey spinal cord. To enable cell identification, sensory dorsal cells and motoneurons were selectively labeled with fluorescein-coupled dextran amine in the intact spinal cord in vitro before dissociation. Calcium channels present in sensory dorsal cells, motoneurons, and other spinal cord neurons were characterized with the use of whole cell voltage-clamp recordings and specific calcium channel agonist and antagonists. The results show that a transient low-voltage-activated (LVA) calcium current was present in a proportion of sensory dorsal cells but not in motoneurons, whereas high-voltage-activated (HVA) calcium currents were seen in all neurons recorded. The different components of HVA current were dissected pharmacologically and similar results were obtained for both dorsal cells and motoneurons. The N-type calcium channel antagonist ω-conotoxin-GVIA(ω-CgTx) blocked >70% of the HVA current. A large part of the ω-CgTx block was reversed after washout of the toxin. The L-type calcium channel antagonist nimodipine blocked ∼15% of the total HVA current. The dihydropyridine agonist (±)-BayK 8644 markedly increased the amplitude of the calcium channel current. The BayK-potentiated current was not affected by ω-CgTx, indicating that the reversibility of the ω-CgTx effect is not due to a blockade of L-type channels. Simultaneous application of ω-CgTx and nimodipine left ∼15% of the HVA calcium channel current, a small part of which was blocked by the P/Q-type channel antagonist ω-agatoxin-IVA. In the presence of the three antagonists, the persistent residual current (∼10%) was completely blocked by cadmium. Our results provide evidence for the existence of HVA calcium channels of the N, L, and P/Q types and other HVA calcium channels in lamprey sensory neurons and motoneurons. In addition, certain types of neurons express LVA calcium channels.
Spatial Processing in the Monkey Frontal Eye Field. I. Predictive Visual Responses
Authors: Umeno Marc M. , Goldberg Michael E.
Published: December 2017

Umeno, M. M. and Goldberg, M. E. Spatial processing in the monkey frontal eye field. I. Predictive visual responses. J. Neurophysiol. 78: 1373–1383, 1997. Neurons in the lateral intraparietal area and intermediate layers of the superior colliculus show predictive visual responses. They respond before an impending saccade to a stimulus that will be brought into their receptive field by that saccade. In these experiments we sought to establish whether the monkey frontal eye field had a similar predictive response. We recorded from 100 presaccadic frontal eye field neurons (32 visual cells, 48 visuomovement cells, and 20 movement cells) with the use of the classification criteria of Bruce and Goldberg. We studied each cell in a continuous stimulus task, where the monkey made a saccade that brought a recently appearing stimulus into its receptive field. The latency of response in the continuous stimulus task varied from 52 ms before the saccade to 272 ms after the saccade. We classified cells as having predictive visual responses if their latency in the continuous stimulus task was less than the latency of their visual on response to a stimulus in their receptive or movement field as described in a visual fixation task. Thirty-four percent (11 of 32) of the visual cells, 31% (15 of 48) of the visuomovement cells, and no (0 of 20) movement cells showed a predictive visual response. The cells with predictive responses never responded to the stimulus when the monkey did not make the saccade that would bring that stimulus into the receptive field, and never discharged in association with that saccade unless it brought a stimulus into the receptive field. The response in the continuous stimulus task was almost always weaker than the visual on response to a stimulus flashed in the receptive field. Because cells with visual responses but not cells with movement activity alone showed the effect, we conclude that the predictive visual response is a property of the visual processing in the frontal eye field, i.e., a response to the stimulus in the future receptive field. It is not dependent on the actual planning or execution of a saccade to that stimulus. We suggest that the predictive visual mechanism is one in which the brain dynamically calculates the spatial location of objects in terms of desired displacement. This enables the oculomotor system to perform in a spatially accurate manner when there is a dissonance between the retinal location of a target and the saccade necessary to acquire that target. This mechanism does not require an explicit calculation of target position in some supraretinal coordinatesystem.