bluuebunny/crossref_metadata_2025 huggingface dataset:
Dendritic origin of late events in optical recordings from salamander olfactory bulb
Authors: Cinelli A. R. , Salzberg B. M.
Published: December 2017

1. Optical recordings of membrane-potential changes were used to characterize the origin and properties of the electrical signals from the dendritic level in slices of the salamander olfactory bulb. 2. The optical events were correlated with field-potential waves recorded simultaneously. Both responses exhibited patterns similar to those found in other species. 3. Orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by two additional principal waves (N1 and N2). These field-potential waves reflected excitatory postsynaptic potentials at the primary mitral/tufted and granule cell dendrites, respectively. 4. Extrinsic optical signals from horizontal slices stained with the pyrazo-oxonal dye RH-155 showed a characteristic sequence of depolarizing and hyperpolarizing events. All of the signals exhibited a wavelength dependence expected for this dye and were abolished in the presence of high K+ in the bath. 5. According to their time courses, depolarizing responses under normal recording conditions were divided into two components, fast and slow. Orthodromic stimuli evoked a fast presynaptic response that represents synchronous compound action potentials from olfactory nerve fibers. At subglomerular levels, additional fast responses could often be recorded at the peri/subglomerular level and in the mitral/tufted somata region. These postsynaptic responses partially coincided with the rising phase of a different depolarizing signal, a slow component characterized by its prolonged time course. 6. With orthodromic stimulation, this slow signal attained its largest amplitude in the zone between the glomeruli and the superficial part of the external plexiform layer (EPL). Antidromic stimuli evoked a signal with some similarities to the one evoked orthodromically, but originating in deeper EPL regions. 7. Slow components were characterized by their Ca dependence. Low Ca2+ medium, or calcium channel blockers, suppressed this optical component, whether evoked orthodromically, antidromically, or by direct stimulation. In addition, Ba2+ (2.5–3.6 mM) in the bath did not abolish these responses, suggesting that they do not reflect a glial depolarization in response to elevated extracellular K+ concentration ([K+]o). 8. Locally applied stimuli next to the glomerular layer elicited these signals in 5–10 microM tetrodotoxin (TTX) or in low extracellular Na+ concentration ([Na+]o) medium, but antidromic or orthodromic stimuli failed to evoke the response under these conditions. The sizes of the responses to local stimuli remained constant, but an increase in their duration was observed in either TTX or low [Na+]o. 9. gamma-Aminobutyric acid (GABA) and baclofen reduced the size of the slow components in a dose-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS)
Control of elevator muscle activity during simulated chewing with varying food resistance in humans
Authors: Ottenhoff F. A. , van der Bilt A. , van der Glas H. W. , Bosman F.
Published: December 2017

1. During chewing, a small part of the observed muscle activity is needed for the basic open-close movements of the mandible, and much additional muscle activity (AMA) is needed to overcome the resistance of the food. In chewing cycles in which a counteracting force is expected, the AMA is mainly generated by peripheral induction with a latency of approximately 23 ms. It was investigated whether an open-loop or closed-loop mechanism is involved in the control of the AMA in these cycles. 2. Subjects made rhythmic open-close movements at their natural chewing frequency controlled by a metronome. Food resistance was simulated by an external force, acting on the jaw in a downward direction during part of the closing movement. Sequences of cycles with a force were unexpectedly alternated with sequences of cycles with a different force. The force changed from 19 to 0 N and vice versa, and from 25 to 6 N and vice versa. Jaw movement and surface electromyogram of the masseter, temporalis, and suprahyoid muscles on both sides were recorded during cycles before and after the transition from one force condition to another. 3. The movement trajectory and AMA of the second and following cycles with a new force appeared to be similar. Thus adaptation to the changed circumstances occurred within two open-close cycles. 4. In the first cycle with 0 or 6 N in the 19----0 N and 25----6 N experiments respectively, a large part of the AMA had disappeared. The AMA in this cycle started to differ from the AMA in the previous cycle approximately 23 ms after the moment the force in this cycle started to differ from the previous cycle. 5. In the first cycle with 19 or 25 N in the reverse experiments, the AMA increased 120–136 ms after the moment the force in this cycle started to differ from the previous cycle. 6. During the closing phase of each open-close cycle, no muscle activity of the suprahyoid muscles was observed; thus co-contraction with the elevator muscles did not occur. 7. It was concluded that the AMA is under control of a closed-loop mechanism with a latency of approximately 23 ms. However, the reflex output has a maximum, depending on information about the food resistance gained in previous cycles.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of inferior temporal neurons in visual memory. I. Temporal encoding of information about visual images, recalled images, and behavioral context
Authors: Eskandar E. N. , Richmond B. J. , Optican L. M.
Published: December 2017

1. Lesions of the inferior temporal (IT) cortex selectively hamper monkeys in tasks requiring visual memory. A system that recognizes images must be able to encode a current stimulus, recall the code of a previous stimulus, compare the codes of the two stimuli, and make a decision on the basis of the outcome of the comparison. Therefore, IT neurons must be involved in at least one of these processes. To determine the specific role of IT neurons in visual memory, we measured the information conveyed in the neuronal responses about current patterns, recalled patterns, and behavioral context. 2. Two monkeys were trained to perform a sequential matching task using a set of 32 black and white Walsh patterns. In the course of an experiment, each pattern was presented repeatedly in sample, match, and nonmatch behavioral contexts. While the monkeys were performing the task, we recorded the activity of 76 neurons from area TE of IT. The neuronal responses to the stimuli were converted to spike density functions, and the resultant waveforms were quantified using their principal components. The relationships between the responses and the stimuli were studied using analysis of variance and information theory. 3. The analysis of variance was applied to the neuronal response waveforms using the context (sample, match, or nonmatch) and the patterns of the stimuli as independent variables and the spike count or the coefficients of the principal components as the dependent variables. We found that the waveforms of most neurons were significantly modulated by both the pattern and the context of the stimulus presentation. 4. We also analyzed the stimulus-response relationships using information theory. The input codes were based on the pattern and context of the stimuli, and the output codes were based on the spike count or the principal components of the responses. The neuronal response waveforms were found to convey significant amounts of information about both the pattern and context of the stimuli. Transmitted information was greatest when the response of a neuron was interpreted as a message about the combination of pattern and context. Nevertheless, there was information about context independent of pattern and vice versa. 5. We also used information theory to determine whether the neuronal responses to the second, or test, stimulus conveyed information about the pattern of the first, or sample, stimulus. The input codes were based on the patterns of the sample stimuli, and the output codes were based on the responses to the nonmatch test stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)
Experimental tests of a superposition hypothesis to explain the relationship between the vestibuloocular reflex and smooth pursuit during horizontal combined eye-head tracking in humans
Authors: Huebner W. P. , Leigh R. J. , Seidman S. H. , Thomas C. W. , Billian C. , DiScenna A. O. , Dell'Osso L. F.
Published: December 2017

1. We used a modeling approach to test the hypothesis that, in humans, the smooth pursuit (SP) system provides the primary signal for cancelling the vestibuloocular reflex (VOR) during combined eye-head tracking (CEHT) of a target moving smoothly in the horizontal plane. Separate models for SP and the VOR were developed. The optimal values of parameters of the two models were calculated using measured responses of four subjects to trials of SP and the visually enhanced VOR. After optimal parameter values were specified, each model generated waveforms that accurately reflected the subjects' responses to SP and vestibular stimuli. The models were then combined into a CEHT model wherein the final eye movement command signal was generated as the linear summation of the signals from the SP and VOR pathways. 2. The SP-VOR superposition hypothesis was tested using two types of CEHT stimuli, both of which involved passive rotation of subjects in a vestibular chair. The first stimulus consisted of a "chair brake" or sudden stop of the subject's head during CEHT; the visual target continued to move. The second stimulus consisted of a sudden change from the visually enhanced VOR to CEHT ("delayed target onset" paradigm); as the vestibular chair rotated past the angular position of the stationary visual stimulus, the latter started to move in synchrony with the chair. Data collected during experiments that employed these stimuli were compared quantitatively with predictions made by the CEHT model. 3. During CEHT, when the chair was suddenly and unexpectedly stopped, the eye promptly began to move in the orbit to track the moving target. Initially, gaze velocity did not completely match target velocity, however; this finally occurred approximately 100 ms after the brake onset. The model did predict the prompt onset of eye-in-orbit motion after the brake, but it did not predict that gaze velocity would initially be only approximately 70% of target velocity. One possible explanation for this discrepancy is that VOR gain can be dynamically modulated and, during sustained CEHT, it may assume a lower value. Consequently, during CEHT, a smaller-amplitude SP signal would be needed to cancel the lower-gain VOR. This reduction of the SP signal could account for the attenuated tracking response observed immediately after the brake. We found evidence for the dynamic modulation of VOR gain by noting differences in responses to the onset and offset of head rotation in trials of the visually enhanced VOR.(ABSTRACT TRUNCATED AT 400 WORDS)
Short-term modulation of cerebellar Purkinje cell activity after spontaneous climbing fiber input
Authors: Sato Y. , Miura A. , Fushiki H. , Kawasaki T.
Published: December 2017

1. There are two opposite points of view concerning the way climbing fiber input in a Purkinje cell modifies simple spike (SS) activity transiently: depression versus enhancement of SS activity. The different groups of investigators favored one effect predominating over the other. In the decerebrate unanesthetized cat, we recorded spontaneous activity of single Purkinje cells and investigated time course of SS activity after the complex spike (CS). 2. In the peri-CS time histogram, there was a SS pause lasting, on average, 10.8 ms after onset of the CS in all of the 316 cells recorded. The pause was followed by a rapid increase in SS activity to a maximum, which was on average 175.6% of a pre-CS control level, and a gradual return to around the control level in the majority of the cells recorded (pause-facilitation type, 71.2%). The increase in SS activity was significant (P < 0.01, t test) during 20-100 ms. The SS activity during the 20-100 ms was, on average, 163.7% of the control level. In some cells (pure-pause type, 25.3%), no significant changes were found (P > 0.01) in the post-pause SS firing. In contrast, only 3.5% of the cells (pause-reduction type) showed a significant (P < 0.01) firing decrease (average 54.0% of the control level) lasting 20-60 ms after the pause period. 3. Analysis of the pre-CS time histogram revealed no significant differences (P > 0.01) in the SS activity between pre-CS periods in all of the cells recorded, suggesting that the SS activity enhancement is not due to a coactivated mossy fiber input just preceding the activation of the climbing fiber input. 4. Analysis of the raster diagram revealed variability of individual SS responses after the CS. The probability of occurrence of the increase in SS number during a post-CS period of 0-100 ms with respect to that during a pre-CS period of -100-0 ms in individual raster traces was high (on average 78.2%), medium (57.3%), and low (36.3%) in the pause-facilitation, pure-pause, and pause-reduction types of the cell, respectively. 5. Nonsequential time histograms showing frequency distribution of the pause duration after the CS in individual raster traces and that showing interspike intervals of the SS were constructed.(ABSTRACT TRUNCATED AT 400 WORDS)
Speed and direction selectivity of macaque middle temporal neurons
Authors: Lagae L. , Raiguel S. , Orban G. A.
Published: December 2017

1. We tested quantitatively the responses of 147 middle temporal (MT) cells to light and dark bars moving at different speeds ranging over a 1,000-fold range (0.5–512 deg/s). 2. We derived the following quantities from the speed-response (SR) curves obtained for opposite directions of motion. Speed selectivity was characterized by the maximum response, optimum speed, upper cutoff speed, response to slow movement, and tuning width. Direction selectivity was characterized by the direction index (DI) averaged over speeds yielding significant responses (MDI) and by the direction index at optimal speed (PDI). 3. There was an excellent correlation between speed characteristics for light and dark bars. These correlations were stronger than the correlations between direction indexes. The strongest correlations were obtained for maximum response and upper cutoff. 4. SR curves were classified into three groups: low pass (25%), tuned (43%), and broadband (28%), leaving 4% unclassified. 5. In the majority (75%) of MT cells, there was an agreement between the typology of speed selectivity for light and dark bars. Cells were classified as tuned (33%), low pass (22%), broadband (19%), and mixed (22%), leaving 4% unclassified. In addition to differences in speed characteristics, these groups also differed in response level, direction selectivity, and distribution of preferred directions. 6. For tuned cells, there was a very tight correlation of most speed characteristics for light and dark bars. 7. Direction selectivity depended on stimulus speed in most neurons, yielding a tuned average speed-DI curve. 8. Speed characteristics, proportions of speed selectivity types, and direction selectivity indexes showed little dependence on laminar position. 9. Speed characteristics and direction selectivity indexes were not dependent on eccentricity. Proportion of speed selectivity types however, changed dramatically with eccentricity: low-pass cells dominated foveally, tuned cells parafoveally, and broadband cells peripherally. 10. There were also small eccentricity effects on the range of optimal speeds shown by tuned cells and on the speed at which direction selectivity decreases in the slow speed range.
Functional differences between afferent fibers in the hypogastric and pelvic nerves innervating female reproductive organs in the rat
Authors: Berkley K. J. , Robbins A. , Sato Y.
Published: December 2017

1. The uterus, cervix, and vaginal canal are innervated by afferent fibers in the hypogastric and pelvic nerves. Four studies compared the innervation territory and sensitivity to peripheral stimuli of the two sets of fibers in adult virgin rats. 2. Innervation territory was studied anatomically by injecting different fluorescent dyes into different parts of the reproductive, lower urinary, and lower digestive tracts and examining retrogradely labeled neurons in dorsal root ganglia. It was also studied electrophysiologically in anesthetized rats by summing potentials evoked in branches of the two nerves by electrical stimulation of different parts of the reproductive tract. 3. In both studies sensory innervation of the reproductive tract shifted from the pelvic to the hypogastric nerve (i.e., shifted entry into the spinal cord from the L6-S1 to the T13-L3 dorsal root ganglia, respectively) as the dye or stimulating electrode shifted from the vaginal entrance to the uterine horns, with fibers from both nerves densely innervating the cervix region (i.e., entering the spinal cord through both sets of ganglia). The anatomic results suggested that the regions innervated by fibers in one nerve might also be innervated by a small component of normally quiescent fibers in the other nerve. 4. Response sensitivity was studied electrophysiologically by simultaneously recording multiunit activity in branches of the hypogastric and pelvic nerves in two ways. First, in intact, anesthetized rats, activity was recorded during mechanical stimulation of the reproductive tract (distension of the vagina and uterus, probing the cervix). Second, in an in vitro organ preparation of the uterus and vagina, activity was recorded during chemical stimulation through the uterine artery with bradykinin, serotonin, NaCN, CO2, and KCl. 5. Pelvic nerve fibers were markedly more sensitive than hypogastric nerve fibers to uterine and cervical mechanostimulation. Similarly, pelvic nerve fibers were more likely to respond or responded more vigorously than hypogastric nerve fibers to all chemical stimuli (except KCl). 6. These results provide strong evidence that afferent fibers in the pelvic and hypogastric nerves of nulliparous adult rats subserve different functions in reproduction and sensation. Pelvic nerve fibers seem closely tied to sensory and behavioral processes associated with mating and conception, whereas hypogastric fibers seem closely tied to pregnancy and nociception, with fibers in both nerves serving functions during parturition.
Alpha-adrenergic modulation of ionic currents in cultured parasympathetic neurons from rat intracardiac ganglia
Authors: Xu Z. J. , Adams D. J.
Published: December 2017

1. Modulation of ionic conductances by alpha-adrenergic agonists was investigated in cultured parasympathetic neurons from rat intracardiac ganglia. Application of norepinephrine (NE, 25-100 microM) to the soma of isolated neurons reversibly reduced both the amplitude and duration of the Ca(2+)-dependent action potential evoked by injection of depolarizing current when Na+ and K+ currents were blocked pharmacologically. 2. In the whole-cell voltage-clamp mode, application of NE reversibly reduced the amplitude and rate of activation of Ca2+ current (ICa). The amplitude inhibition was greater at the peak of the current (55%) than at the end of a 700-ms pulse (20%). Maximal doses of NE produced only approximately 60% inhibition of peak ICa amplitude. 3. Inactivation of ICa was best fit by the sum of two exponential functions in the absence of NE, but was described by a single exponential function in the presence of NE. These results suggest that NE preferentially inhibited a fast inactivating component of the Ca2+ current in these parasympathetic neurons. 4. NE reversibly reduced the amplitude of Ba2+ tail currents through open Ca channels at all voltages from -40 to +150 mV with a slight shift in the activation curve determined from the current-voltage (I-V) relationship for the tail currents. NE did not change the voltage dependence of the steady-state inactivation of the calcium channels. 5. NE inhibited Ca2+ current either in the absence or presence of nifedipine but to a lesser extent in the presence of omega-conotoxin (omega-CGTX), suggesting that the Ca channels inhibited by NE are predominantly omega-CGTX sensitive. 6. The inhibition of ICa by NE was mimicked by the alpha 1-adrenergic agonists methoxamine and phenylephrine and potentiated in the presence of the alpha 2-adrenoceptor antagonist yohimbine (10 microM). NE inhibition of ICa was antagonized by bath application of the alpha-adrenergic antagonist phentolamine (1 microM), but not by prazosin (1-10 microM), yohimbine, or the beta-adrenergic antagonist propranolol (1 microM). Taken together, these results suggest that NE inhibition of Ca2+ current in rat parasympathetic cardiac neurons is mediated by an alpha-adrenergic receptor with properties that may differ from alpha 1- and alpha 2-adrenoceptors. 7. In approximately 35% of neurons studied, NE not only reduced depolarization-activated inward Ca2+ current but also increased an outward current, with a shift of the I-V curve and reversal potential to more negative voltages.(ABSTRACT TRUNCATED AT 400 WORDS)
Prenatal development of the receptive fields of individual trigeminal ganglion cells in the rat
Authors: Chiaia N. L. , Bauer W. R. , Rhoades R. W.
Published: December 2017

1. Extracellular single-unit recording and receptive-field mapping techniques were used to evaluate the response characteristics of trigeminal (V) ganglion cells in unanesthetized, decerebrate, fetal rats between the ages of embryonic (E-) day 15 and E-20 (E-0 is the day of conception). 2. The receptive-field properties of the cells (n = 282) recorded at all of these ages except E-15 were remarkably similar; V primary afferents were generally silent in the absence of peripheral stimulation (94.3%) and gave rapidly adapting responses to innocuous tactile stimuli (97.5%). Rapid response decrements to repeated stimuli were observed in 9 of the 14 cells (64%) tested. 3. None of the cells recorded were activated by either heat or cold. No attempt was made to evaluate responses to noxious mechanical stimuli. 4. Particular attention was paid to neurons whose receptive fields involved mystacial vibrissae follicles. At all ages, neurons were recorded that responded to indentation of the skin at the base of the vibrissae, but vibrissa deflection was not an adequate stimulus for any of the cells tested. At all ages, nearly all (89.0%) of the 127 cells with vibrissa-related receptive fields responded to indentation of one and only one follicle. 5. These results indicate that the response properties (e.g., adaptation characteristics, ability to respond to repeated stimuli) of V primary afferents in fetal rats differ substantially from those of V ganglion cells in adult animals, but that the receptive-field size for these neurons in prenatal rats is, with very rare exceptions, adult-like from the earliest age at which they can be recorded. 6. These results, when considered together with the results of previous retrograde tracing experiments in fetal animals, suggest that the initial projections of V primary afferents to their peripheral targets may be quite accurate.
Intracellular recordings from morphologically identified neurons of the basolateral amygdala
Authors: Rainnie D. G. , Asprodini E. K. , Shinnick-Gallagher P.
Published: December 2017

1. Intracellular current-clamp recordings were made from neurons of the basolateral nucleus of the amygdala (BLA) of the rat in the in vitro slice preparation. Neurons were identified morphologically after intracellular injection of biocytin, and the electrophysiological properties and morphological characteristics were correlated. 2. Three distinct morphological subtypes were identified: Class I pyramidal neurons, Class I stellate neurons, and Class II neurons. Each morphological subtype could also be distinguished according to its characteristic electrophysiological properties. 3. Class I pyramidal neurons typically had pyramidal perikarya (cross-sectional area = 245 microns2) with spine-laden apical and basal dendrites. The axon originated from the largest basal dendrite and produced several collaterals that ramified throughout the dendritic arborization of the parent cell. These neurons were characterized electrophysiologically by their higher input resistance (65.6 M omega), long time constant of membrane charging tau 0 (27.8 ms), long duration action potential (half-width = 0.85 ms), and regular firing pattern [1st interspike interval ISI) = 91 ms]. 4. Class I stellate neurons differed morphologically from Class I pyramidal neurons only in the size (cross sectional area = 330 microns 2) and stellate appearance of their perikarya. These neurons had characteristic lower input resistance (40.1 M omega), shorter time constant of membrane charging tau 0 (14.5 ms), shorter duration action potential (half-width = 0.7 ms), and a burst firing pattern (1st ISI = 6.0 ms), all of which were statistically different from Class I pyramidal neurons. 5. Class II neurons were multipolar (cross sectional area = 235 microns 2) and were distinguishable from Class I neurons by the almost complete absence of dendritic spines. Class II neurons were characterized electrophysiologically by a midrange input resistance (58 M omega), intermediate time constant of membrane charging tau 0 (19 ms), intermediate action-potential duration (half-width = 0.77 ms), and a burst firing pattern (1st ISI = 6.0 ms). In contrast to Class I neurons, action-potential firing of Class II neurons did not accommodate in response to prolonged depolarizing current injection. 6. In conclusion, BLA neurons may be characterized by their specific electrophysiological properties as well as by their morphological traits. Therefore, permitting assessment of signal transduction in identified populations of neurons within this nucleus.
Dynamics of reflex cocontraction in hermit crab abdomen: experiments and a systems model
Authors: Chapple W. D.
Published: December 2017

1. Both stretch and release of the ventral superficial muscles (VSM) in the abdomen of the hermit crab, Pagurus pollicarus, activate the VSM motoneurons in the intact animal and in the isolated abdomen. 2. This reflex was studied by recording intracellularly from muscle fibers innervated by single motoneurons during stretch and release of the VSM. The three motoneurons of the right fourth segment respond to both stretch and release with a phasic burst lasting approximately 250 ms. The burst in the two tonic motoneurons has two components, a short burst lasting 10-20 ms, with a latency from the beginning of stretch of 60-90 ms, and a longer burst of variable length, with a latency of 120 ms. Ramp stretches of different amplitudes and velocities were used to show that the first component is proportional to the absolute value of the second derivative of force and the second component to the absolute value of the first derivative of force. 3. Stretch and release of the VSM also simultaneously evoke phasic bursts in the motoneurons of the dorsal superficial muscles and the VSM circular muscles (functional antagonists of the longitudinal VSM), as well as in contralateral homologues of the same segment and in ipsilateral homologues of the next anterior segment. The effect of this coactivation is to stiffen the abdomen in response to perturbations in any direction. 4. Stretch or release of phasic mechanoreceptors in the VSM evokes this reflex. Isometric electrical stimulation of the isolated muscle also activates them, showing that they are transducing changes in force and suggesting that they operate to increase muscle stiffness by positive feedback. 5. A mathematical systems model of this reflex, composed of two parallel pathways activating the motoneurons, was constructed. The first pathway produces a signal proportional to the absolute value of the second derivative of force, the second pathway a signal proportional to the first derivative of force. The sum of the signals from the two pathways is filtered by an adaptation process, which is followed by a low-pass filter representing muscle activation kinetics. The muscle activation signal is then fed back to multiple muscle force. 6. Simulations using this model generate the phasic bursts to stretch and release as well as reproducing the frequency dependence of this reflex. The predominant action of this reflex is to enhance muscle stiffness.
Coherent network oscillations by olfactory interneurons: modulation by endogenous amines
Authors: Gelperin A. , Rhines L. D. , Flores J. , Tank D. W.
Published: December 2017

1. The procerebral (PC) lobe of the terrestrial mollusk Limax maximus contains a highly interconnected network of local olfactory interneurons that receives direct axonal projections from the two pairs of noses. This olfactory processing network generates a 0.7-Hz oscillation in its local field potential (LFP) that is coherent throughout the network. The oscillating LFP is modulated by natural odorants applied to the neuroepithelium of the superior nose. 2. Two amines known to be present in the PC lobe, dopamine and serotonin, increase the frequency of the PC lobe oscillation and alter its waveform. 3. Glutamate, another putative neurotransmitter known to be present in the lobe, suppresses the PC lobe oscillation by a quisqualate-type receptor and appears to be used by one of the two classes of neurons in the PC lobe to generate the basic LFP oscillation. 4. The known activation of second messengers in Limax PC lobe by dopamine and serotonin together with their effects on the oscillatory rhythm suggest the hypothesis that these amines augment mechanisms mediating synaptic plasticity in the olfactory network, similar to hypothesized effects of amines in vertebrate olfactory systems. 5. The use of a distributed network of interneurons showing coherent oscillations may relate to the highly developed odor recognition and odor learning ability of Limax.
Small-caliber afferent inputs produce a heterosynaptic facilitation of the synaptic responses evoked by primary afferent A-fibers in the neonatal rat spinal cord in vitro
Authors: Thompson S. W. , Woolf C. J. , Sivilotti L. G.
Published: December 2017

1. The effect of brief primary afferent inputs on the amplitude and duration of the synaptic potentials evoked in ventral horn (VH) neurons by the activation of other unconditioned primary afferents was studied by current-clamp intracellular recording in the neonatal rat hemisected spinal cord in vitro. Low-frequency (1 Hz) trains of stimulation were applied to a lumbar dorsal root (Conditioning root) for 20-30 s. Test excitatory synaptic potentials (EPSPs) were evoked by single electrical shocks applied to an adjacent Test dorsal root. 2. Test and Conditioning inputs were generated at stimulation strengths sufficient to activate A beta-, A delta- and C-afferent fibers successively. At A delta- and C-fiber strength the EPSPs lasted for 4-6 s, and, during the repetitive Conditioning inputs, these summated to produce a progressively incrementing cumulative depolarization that slowly decayed back to the control Vm over tens of seconds. 3. Dorsal root conditioning produced heterosynaptic facilitation, defined as an enhancement of Test EPSPs above their DC matched controls, in 7 out of 20 neurons. To facilitate the unconditioned afferent input, the intensity of conditioning stimulation had to exceed the threshold for the activation of thin myelinated (A delta) afferents: conditioning at A beta-fiber strength had no effect, whereas A delta- and C-fiber strength conditioning were equally effective. 4. Heterosynaptic facilitation of only A beta- or A delta-fiber-evoked Test EPSPs was observed, no enhancement of C-fiber strength Test EPSPs could be demonstrated. The facilitation manifested as increases in the EPSP peak amplitude, area or the number of action potentials evoked. 5. Conditioning trials that produced heterosynaptic facilitation generated cumulative depolarizations larger than those produced by ineffective conditioning trials (9.1 +/- 3.1 vs. 3.3 +/- 0.5 mV after 20 s conditioning at resting Vm, mean +/- SE, n = 6 and 13, respectively; P < 0.05). The slope of the Vm trajectory during the summation of the conditioning EPSPs was higher in trials resulting in heterosynaptic facilitation, at 0.31 +/- 0.10 mV/s in neurons with heterosynaptic facilitation and 0.06 +/- 0.02 mV/s in cells without heterosynaptic facilitation (P < 0.05). 5. Four of the 20 VH neurons in our sample responded to A delta/C-fiber conditioning with action-potential windup: all 4 also displayed heterosynaptic facilitation. 6. Heterosynaptic facilitation decayed after the completion of the conditioning stimulus with a time course that was parallel to but not superimposable on that of the slow Vm depolarization evoked by the conditioning.(ABSTRACT TRUNCATED AT 400 WORDS)
Voltage dependence of the rat chorda tympani response to Na+ salts: implications for the functional organization of taste receptor cells
Authors: Ye Q. , Heck G. L. , DeSimone J. A.
Published: December 2017

1. Voltage-clamp and current-clamp data were obtained from a circumscribed region of the anterior rat lingual epithelium while simultaneously monitoring the afferent, stimulus-evoked, neural response from the same receptive field. 2. Chorda tympani (CT) responses at constant Na(+)-salt concentration were enhanced by submucosa negative voltage clamp and suppressed by positive voltage clamp. The complete CT response profile, including the time course of adaptation, was not uniquely determined by NaCl concentration alone. The response could be reproduced at different NaCl concentrations by applying a compensating voltage. 3. The form of the concentration and voltage dependence of the CT response indicates that the complete stimulus energy is the Na+ electrochemical potential difference across receptor cell apical membranes, and not Na+ concentration alone. This is the underlying principal behind the equivalence of chemical and electric taste for Na+ salts. 4. CT responses to sodium gluconate (25 and 200 mM) and 25 mM NaCl produced amiloride-insensitive components (AIC) of low magnitude. NaCl at 200 mM produced a significantly larger AIC. The AIC was voltage-clamp independent. The relative magnitude of the AIC was positively correlated with the transepithelial conductance of each salt. This suggests that the large AIC for 200 mM NaCl results from its relatively high permeability through the paracellular pathway. 5. Analysis of the CT response under voltage clamp revealed two anion effects on Na(+)-salt taste, both of which act through the paracellular shunt. 1) Anions modify the transepithelial potential (TP) across tight junctions and thereby modulate the cell receptor potential. This anion effect can be eliminated by voltage clamping the TP. 2) Sufficiently mobile anions facilitate electroneutral diffusion of Na+ salts through tight junctions. This effect is observed especially when Cl- is the anion and when the stimulus concentration favors NaCl influx, allowing Na+ to stimulate receptor cells from the submucosal side. Because the submucosal intercellular spaces are nearly isopotential regions, this effect is insensitive to voltage clamp of the TP. The large AIC associated with this anion effect is due to the low permeability of amiloride.
Differential ontogenesis of presynaptic and postsynaptic GABAB inhibition in rat somatosensory cortex
Authors: Fukuda A. , Mody I. , Prince D. A.
Published: December 2017

1. The postnatal maturation of gamma-aminobutyric acid (GABA)B receptor-mediated presynaptic inhibition was studied in brain slices of rat somatosensory cortex maintained in vitro. Patchclamp techniques were used to record whole-cell inhibitory post-synaptic currents from layer II-III neurons in animals from postnatal days (P) 7-24. Monosynaptic inhibitory postsynaptic currents (IPSCs) were evoked after N-methyl-D-aspartate (NMDA) and non-NMDA type glutamate receptors had been blocked by D-amino-phosphonovaleric acid (D-AP5, 20 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM), respectively. These IPSCs were solely mediated by postsynaptic GABAA receptors because they were abolished by bicuculline (10 microM), reversed polarity near the chloride equilibrium potential, and were recorded with electrodes that contained Cs+ to block postsynaptic GABAB responses. 2. When pairs of stimuli separated by intervals of 0.1-10 s were used to evoke IPSCs, the second response was depressed, an effect that was maximal at 300 ms. Evoked IPSCs were also depressed by baclofen (10 microM). The paired pulse depression (PPD) of monosynaptic IPSCs was decreased or eliminated by 2-OH-saclofen (200 microM). These findings indicate that PPD of monosynaptic IPSCs was due to presynaptic GABAB receptor-mediated inhibition of GABA release. 3. There were no significant differences in the amounts of PPD in neurons from different age groups (P7-10, P12-17, P22-24) at any interstimulus interval tested (0.1-10 s).(ABSTRACT TRUNCATED AT 250 WORDS)
Rat tail flick reflex: magnitude measurement of stimulus-response function, suppression by morphine and habituation
Authors: Carstens E. , Wilson C.
Published: December 2017

1. To quantitatively investigate a nocifensive behavioral response, we developed a method to measure the magnitude of the rat's tail flick reflex and its modulation. A radial array of force transducers measured forces of tail flicks (in rostral, horizontal, and vertical planes) elicited by graded noxious radiant thermal stimulation of the conscious rat's tail, from which the overall movement vector was calculated. 2. The rostrally directed component of tail flicks was always larger than dorsal or horizontal components; the latter was usually in a preferred (left or right) direction regardless of which side of the tail was heated. Tail flick force vectors increased from 40 to 46-52 degrees C and then leveled off. Stimulus-response functions were reproducible within and across rats and were fitted by second-order polynomial functions, whose correlation coefficients were similar when the left or right side of the tail was stimulated in separate sessions (r2 = 0.408 and 0.451, respectively). The inverse latency of tail flicks also increased with temperature in a manner fitted by a second-order polynomial (r2 = 0.707, 0.553 for left and right side, respectively). 3. Systemic administration of morphine (1 or 2 mg/kg ip) usually suppressed tail flicks in an all-or-none manner; i.e., flicks at all stimulus temperatures were either totally abolished (n = 7) or unaffected (n = 5) after morphine. In three rats, 1 mg/kg morphine suppressed tail flick magnitude subtotally, reducing the slope of the linear portion of the stimulus-response function. Morphine effects were reversed by the opiate antagonist naloxone. 4. Tail flick magnitude decreased over repeated trials of 44 degrees C heat stimuli delivered to one tail site, recovered after a 15-min rest period, and decremented more quickly with subsequent stimulus repetition. The decrement was less at long (2 or 4 min) than at short (1 min) interstimulus intervals, and high (50 degrees C) than at low (44 degrees C) stimulus intensities. The reflex decrement transferred to a nearby stimulus site in some rats, and was "dishabituated" after a noxious tail pinch. These observations are consistent with habituation of the tail flick reflex. 5. This method, therefore, provides a quantitative and reproducible measure of tail flick reflex magnitude that is sensitive to morphine. The underlying neural circuitry of the tail flick reflex is discussed in relation to limb withdrawal reflexes.
Information encoding and the responses of single neurons in the primate temporal visual cortex
Authors: Tovee M. J. , Rolls E. T. , Treves A. , Bellis R. P.
Published: December 2017

1. The possibility of temporal encoding in the spike trains of single neurons recorded in the temporal lobe visual cortical areas of rhesus macaques was analyzed with the use of principal component and information theory analyses of smoothed spike trains. The neurons analyzed had responses selective for faces. 2. Provided that a correction was applied to earlier methods of principal component analysis used for neuronal spike trains, it was shown that the first principal component provides by a great extent the most information, with the second and third adding only small proportions (on average 18.8 and 8.4%, respectively). 3. It was shown that the magnitude of the second and higher principal components is even smaller if the spike train analysis is started after the onset of the neuronal response, instead of before the neuronal response has started. This suggests that variations in response latency are at least a part of what is reflected by the second and higher principal components. 4. The first principal component was correlated with the mean firing rate of the neurons. The second and higher principal components reflected at least partly the onset properties of the neuronal responses, such as response latency differences between the stimuli. 5. A considerable proportion of the information available from principal components 1-3 is available in the firing rate of the neuron. 6. Periods of the firing rate of as little as 50 or even 20 ms are sufficient to give a reasonable estimate of the firing rate of the neuron. 7. Information theory analysis showed that in short epochs (e.g., 50 ms) the information available from the firing rate can be as high, on average, as 84.4% of that available from the firing rate calculated over 400 ms, and 52.0% of that available from principal components 1-3 in the 400-ms period. It was also found that 44.0% of the information calculated from the first three principal components is available in the firing rates calculated over epochs as short as 20 ms. 8. More information was available near the start of the neuronal response, and the information available from short epochs became less later in the neuronal response. 9. Taken together, these analyses provide evidence that a short period of firing taken close to the start of the neuronal response provides a reasonable proportion of the total information that would be available if a long period of neuronal firing (e.g., 400 ms) were utilized to extract it, even if temporal encoding were used.(ABSTRACT TRUNCATED AT 400 WORDS)
Muscle synergies and isometric torque production: influence of supination and pronation level on elbow flexion
Authors: Jamison J. C. , Caldwell G. E.
Published: December 2017

1. Twenty normal subjects performed a series of isometric elbow flexion (F) maximum voluntary contractions (MVC) while simultaneously maintaining one of seven targeted torque levels in the supination/pronation (S/P) degree of freedom (df). Experimental measures were torque in both df s and surface electromyograms (EMG) from brachioradialis (BRAD), triceps brachii (TB), biceps brachii (BB) short head (BBSH), and a medial and lateral site on biceps brachii long head (MED BB and LAT BB). Task effects were tested for significance using analysis of covariance models for the torque and EMG variables. Polynomial multiple regression models were developed for significant effects. The synergism among muscles was examined by statistically testing the EMG data for differing responses to the S/P torque changes across the five electrode sites. 2. The magnitude of the S/P target torque had a statistically significant effect on flexion MVC (F MVC) torque. Changes in S/P torque markedly influenced the F MVC torque magnitude, with as much as a 25% F torque decrement relative to an F MVC with an S/P torque target of 0. This suggests that the second df task affects some aspect of joint function that causes the CNS to reduce F torque capacity. 3. The S/P torque had a significant effect on EMG amplitude at all electrode sites other than TB. The EMG amplitude at the BB sites responded strongly to both F and S/P torque changes. The F+S tasks tended to facilitate BB EMG, whereas the F+P tasks tended to diminish it. The BRAD EMG, although primarily related to F torque amplitude, also was influenced by the S/P torque changes. The trends for BRAD EMG were opposite those for the BB in that BRAD EMG tended to be enhanced by the F+P tasks and reduced by the F+S tasks. 4. The synergistic pattern of stimulation (i.e., the relationship among the 5 EMG amplitude measures) was also significantly influenced by the S/P df task. Significant differences in the EMG behavior between BBSH and LAT BB were detected; however, no statistically significant differences were found between LAT BB and MED BB. The EMG behaviors at the BRAD and TB electrode sites were significantly different from those at the BB sites. 5. These inversely related responses from the BB and BRAD stress the importance of understanding the relationship between muscular activity and the function of muscles in more than one df. This finding further suggests that the synergistic relationships between muscles are dynamically related to task in all applicable dfs. It is suggested that this dynamic synergism is a natural consequence of the redundant musculoskeletal system.(ABSTRACT TRUNCATED AT 400 WORDS)
Responses of single hamster parabrachial neurons to binary taste mixtures of citric acid with sucrose or NaCl
Authors: Vogt M. B. , Smith D. V.
Published: December 2017

1. Although taste experience generally arises from a mixture of gustatory stimuli, most neurophysiological studies of the mammalian central gustatory system have focused on responses to single chemical stimuli. Recently, in a study of single third-order neurons in the hamster parabrachial nucleus (PbN), we reported that mixture suppression occurs in the responses to binary mixtures of sucrose and QHCl presented to the anterior tongue. Mixture suppression was reflected both in reduced response frequencies and in an altered pattern of responses across neurons. In the current report we extend our investigation of CNS neuron responses to binary mixtures of heterogeneous stimuli to include sucrose+citric acid mixtures and NaCl+citric acid mixtures. The response to each mixture was compared with the response to the more effective component (MEC) presented alone, and those that differed by more than a selected criterion (based on response variability) were identified. 2. For all mixture responses recorded, 29% (79/256) involved mixture suppression (mixture response < MEC response), only 6% (18/276) were greater than the response to MEC, and 65% (179/276) did not differ from the response to the MEC. 3. In Experiments 1 and 2, neurons were tested with four concentrations of sucrose or citric acid each presented alone and in binary mixtures with a single strong concentration of the other stimulus. Sucrose suppression (mixture response < sucrose response) occurred in 24% of mixture responses and was exhibited almost exclusively by sucrose-best neurons, primarily to the mixtures that contained the stronger sucrose and citric acid concentrations. Sucrose suppression involved a 40% reduction of mixture response frequencies compared with responses to the sucrose component alone. 4. In Experiments 3 and 4, neurons were tested with four concentrations of NaCl or citric acid each presented alone and in binary mixtures with a single strong concentration of the other stimulus. NaCl suppression (mixture response < NaCl response) occurred in 21% of mixture responses and was displayed by both sucrose-best and NaCl-best neurons. NaCl suppression involved a 28% reduction in mixture response frequencies compared with responses to the NaCl component alone. In all experiments citric acid suppression (mixture response < citric acid response) was observed in only 6% of mixture responses and was relatively small in magnitude. 5. The across-neuron patterns (ANPs) of taste responses, which are correlated with behavioral measures of taste similarity, were compared for mixtures and components.(ABSTRACT TRUNCATED AT 400 WORDS)