bluuebunny/crossref_metadata_2025 huggingface dataset:
Response similarity to odors in olfactory bulb output cells presumed to be connected to the same glomerulus: electrophysiological study using simultaneous single-unit recordings
Authors: Buonviso N. , Chaput M. A.
Published: December 2017

1. The glomeruli of the olfactory bulb are discrete anatomic structures in which the terminals of receptor cell axons make extensive contacts with the primary dendrites of the mitral and tufted output cells. In mammals, each mitral and deep tufted (M/T) cell possesses a single primary dendrite and sends it toward the glomerulus situated just in front of its somata. 2. We tested the hypothesis that the glomeruli, which appear to form anatomic units, could act to some extent as functional units. A unitary functioning implies that the M/T cells connected to the same glomerulus will more often display similar responses to odorants than cells having no common glomerular relationships, including cells related to adjacent glomeruli. 3. In anesthetized adult rats, we recorded the extracellular single-unit responses of pairs of M/T cells to a series of five odorants. Recordings were performed with the use of twin microelectrodes whose tips were separated either by less than 40 or by 150-200 microns. Because of the olfactory bulb organization, we assumed that the close cells, recorded at a distance less than 40 microns, were more often connected to the same glomerulus, whereas the distant cells, recorded at a distance of 150-200 microns, were more often connected to adjacent glomeruli. 4. Stimulus-evoked changes in firing rate were classified as either excitatory (+), suppressive (-), or null (0) responses. The collection of response types of a given cell to the 5 odorants composed its response profile. Response profiles were used to compare the responsiveness within close and within distant cell pairs with that observed within control pairs of cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Premotor neurons B51 and B52 in the buccal ganglia of Aplysia californica: synaptic connections, effects on ongoing motor rhythms, and peptide modulation
Authors: Plummer M. R. , Kirk M. D.
Published: December 2017

1. Two buccal ganglia interneurons, labeled here as B51 and B52, have been identified on the basis of morphological and physiological criteria. 2. These neurons have multipolar cell bodies. B51 extends a major neurite, which arborizes in the neuropil ipsilateral to the soma; extends into the buccal commissure, where it branches profusely; and projects an axon out the radular nerve (n1); other processes emanating from the soma arborize in the adjacent cell body layer. B52 arborizes ipsilateral to its cell body and sends a major process out of the ipsilateral hemiganglion into the sheath that attaches the buccal ganglia to the buccal mass proper. Here the B52 axon projects through a previously undescribed structure, which forms an arch over the buccal commissure that we designate the commissural arch. The extraganglionic B52 axon sends several branches into the connective tissue and then returns to the contralateral hemiganglion, where it again branches. 3. Each neuron exhibits a unique set of physiological properties. B51 frequently produces plateau potentials, which persist and are even enhanced in solutions where Ca2+ is replaced with Co2+. On the other hand, B52 shows a powerful posthyperpolarization rebound that contributes to its burst formation during spontaneous and nerve-elicited cyclic motor output. 4. B51 and B52 display distinctive rhythmic bursting on stimulation of the radular nerve or esophageal nerve. Their burst-firing tended to occur at certain phase relationships with respect to firing in other buccal premotor and motor neurons. 5. When firing frequency is measured as a function of intracellularly injected current, B51 shows a steplike increase in firing with increasing current, whereas B52 firing frequency is continuously graded. 6. B51 and B52 were found to make extensive synaptic connections within the buccal ganglia. B51 exhibited primarily excitatory electrical connections with known premotor and motor neurons, including an electrotonic synapse with its contralateral homologue. 7. In contrast, B52 made bilateral inhibitory synapses with nearly all of the premotor and motor neurons of the ventral motor cluster. Most of these connections appeared to be monosynaptic, producing synaptic potentials with short and fixed latencies that persisted when the ganglia were bathed in solutions containing elevated concentrations of Ca2+ and Mg2+. 8. Other synaptic potentials produced by B52 were more variable in size and latency; these included slow inhibition of the B4 and B5 neurons and excitation of an identifiable neuron that projected out the radular nerve.(ABSTRACT TRUNCATED AT 400 WORDS)
Responses of nociceptive SI neurons in monkeys and pain sensation in humans elicited by noxious thermal stimulation: effect of interstimulus interval
Authors: Chudler E. H. , Anton F. , Dubner R. , Kenshalo D. R.
Published: December 2017

1. Twenty-six nociceptive neurons in the primary somatosensory cortex (SI) of anesthetized monkeys were responsive to noxious thermal stimulation applied to the face. Thermode temperature increased from a base line of 38 degrees C to temperatures ranging from 44 to 49 degrees C (T1). After a period of 5 s, the temperature increased an additional 1 degree C (T2). The neuronal responses to noxious thermal stimuli were compared when the interstimulus interval (ISI) was 30 or 180 s. 2. A linear regression analysis was applied to the stimulus-response functions of neuronal responses to T1 stimuli obtained at ISIs of 180 s. Based on the slopes and linear regression coefficients of these stimulus-response functions, two populations of nociceptive neurons were identified. The neuronal responses of one population of nociceptive SI neurons (WDR1) to T1 stimuli were characterized by steep slopes and high regression coefficients, whereas the other population (WDR2) had flatter slopes and lower regression coefficients. WDR1 neurons responded with monotonic increases in neuronal activity as the stimulus intensity increased. However, the peak frequency of WDR2 neurons often reached a plateau below 47 degrees C. Both WDR1 and WDR2 neurons had receptive fields that encompassed one or two divisions of the trigeminal nerve. 3. The T1 neuronal responses of WDR1 neurons were significantly suppressed when thermal stimuli were delivered with ISIs of 30 s. The T1 neuronal responses of WDR2 and the T2 responses of both WDR1 and WDR2 neurons were not significantly different when ISIs of 30 and 180 s were used. The T1 thresholds of WDR1 and WDR2 neurons were significantly higher when stimuli were delivered with ISIs of 30 s compared with ISIs of 180 s. 4. Most nociceptive SI neurons were located in layers III and IV of area 1-2. In a number of instances, multiple nociceptive neurons were found in the same microelectrode penetration. 5. The humans' intensity of pain sensation paralleled the neuronal responses of nociceptive SI neurons. With the use of a similar paradigm as in the monkey experiments, increases in T1 and T2 temperatures resulted in monotonic increases in pain ratings and change in pain sensation, respectively. However, the intensity of pain sensation to T1 temperatures was suppressed by ISIs of 30 s. Neither ISI produced statistically significant changes in the intensity of pain sensation to T2 stimuli. 6. These data demonstrate that manipulations that alter the intensity of pain sensation also produce concomitant changes in the responsiveness of nociceptive SI neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Dopamine neurons of the monkey midbrain: contingencies of responses to active touch during self-initiated arm movements
Authors: Romo R. , Schultz W.
Published: December 2017

1. Previous studies have shown that midbrain dopamine (DA) neurons in monkeys respond to external stimuli that are used to initiate behavioral reactions. In the present study, we investigated to what extent changes in neuronal activity would occur when behavioral acts are generated internally or whether they would depend solely on external stimuli. 2. Monkeys performed self-initiated arm movements from a resting key into a covered, food-containing box at a self-chosen moment and without external preparatory or triggering signals. In a second task, the arm movement was triggered by rapid opening of the door of the food box. This stimulus was either audible and visible or only audible to the animal. Impulses of DA neurons were recorded with movable microelectrodes from the pars compacta of substantia nigra (area A9) and areas A8 and A10 and were discriminated from those of other neurons by their long duration (1.5-5.0 ms) and low spontaneous frequency (0.5-8.5 imp/s). 3. The activity of 12% of 104 DA neurons increased slowly and moderately up to 1,500 ms before the onset of individual self-initiated arm movements. Median increases amounted to 91% over background discharge rate. A further 16% of DA neurons were activated together with the onset of muscle activity and during the movement. 4. During self-initiated movements, a nonhabituating, phasic burst of impulses occurred when the monkey's hand touched a morsel of food inside the box. This response was seen in 84% of 154 neurons on the contralateral side, with median onset latency of 65 ms and duration of 160 ms. A comparable percentage of neurons responded to ipsilateral touch with similar latency and duration. 5. The touch response during self-initiated movements was absent, both on the contra- and ipsilateral sides, when the animal's hand touched the bare wire normally holding the food, when touching nonfood objects, or during tactile exploration of the empty interior of the food box. Thus responses appeared to be related to the appetitive properties of the object being touched rather than the object itself. 6. In the task employing stimulus-triggered movements, 77% of 86 DA neurons discharged a burst of impulses in response to door opening but entirely failed to respond to the touch of food in the box. The response to door opening in this task was similar to the touch response during self-initiated movements in the same neurons in terms of latency, duration, and magnitude.(ABSTRACT TRUNCATED AT 400 WORDS)
Synaptic and intrinsic control of membrane excitability of neostriatal neurons. II. An in vitro analysis
Authors: Calabresi P. , Mercuri N. B. , Bernardi G.
Published: December 2017

1. The effects of intrinsic membrane properties on the spontaneous and synaptically evoked activity of neostriatal neurons were studied in an in vitro slice preparation with the use of intracellular recordings. The recorded neurons did not show spontaneous action potentials at rest; depolarizing current pulses triggered a tonic firing pattern. 2. Subthreshold spontaneous depolarizing potentials (SDPs) were observed in 52% of the recorded neurons. The amplitude of these potentials at rest ranged between 2 and 15 mV, and their duration between 4 and 100 ms. The frequency and the amplitude of the SDPs were functions of the membrane potential: membrane depolarization by constant positive current increased the frequency of the SDPs and reduced their amplitude; hyperpolarization of the membrane decreased their frequency and increased their amplitude. Often, at membrane potentials more negative than -90 mV, SDPs were completely suppressed. 3. SDPs were blocked by low calcium-cobalt containing solutions. In the presence of tetrodotoxin (TTX, 1-3 microM), SDPs were completely abolished in 50% of the tested neurons; in the remaining neurons, small (1-4 mV) TTX-resistant SDPs were observed. In most of the neurons, bicuculline (BIC, 10-100 microM) and low concentrations of tetanus toxin (5-10 micrograms/ml) did not clearly affect the SDPs. Higher concentrations of tetanus toxin (100 micrograms/ml) blocked the SDPs as well as the synaptic potentials evoked by intrastriatal stimulation. 4. At resting membrane potential, intrastriatal stimulation produced a fast depolarizing postsynaptic potential (EPSP) that was reduced by BIC (10-100 microM). The relationship between EPSP amplitude and membrane potential was studied either by utilizing K(+)-chloride electrodes or by the use of cesium-chloride electrodes. In both these cases, the reversal potential for the EPSPs was between 0 and -14 mV. In cesium-loaded neurons, the decrease of the EPSP, usually observed at negative membrane potentials (below -85 mV), was clearly reduced. Internal cesium prolonged the duration of the SDPs and the EPSPs evoked by intrastriatal stimulation. 5. The relationship between spontaneous and evoked synaptic activity and membrane potential was studied in the presence of different external potassium blockers. 4-Aminopyridine (4AP, 0.1-1 mM) increased the EPSP amplitude and the frequency of the SDPs, but did not decrease membrane rectification and the shunt of the EPSPs present at negative membrane potentials. On the contrary, rectification of the membrane and the shunt of the EPSPs below -85 mV were clearly reduced by tetraethylammonium (TEA, 10-20 mM).(ABSTRACT TRUNCATED AT 400 WORDS)
Visual tracking in monkeys: evidence for short-latency suppression of the vestibuloocular reflex
Authors: Lisberger S. G.
Published: December 2017

1. Monkeys normally use a combination of smooth head and eye movements to keep the eyes pointed at a slowly moving object. The visual inputs from target motion evoke smooth pursuit eye movements, whereas the vestibular inputs from head motion evoke a vestibuloocular reflex (VOR). Our study asks how the eye movements of pursuit and the VOR interact. Is there a linear addition of independent commands for pursuit and the VOR? Or does the interaction of visual and vestibular stimuli cause momentary, "parametric" modulation of transmission through VOR pathways? 2. We probed for the state of the VOR and pursuit by presenting transient perturbations of target and/or head motion under different steady-state tracking conditions. Tracking conditions included fixation at straight-ahead gaze, in which both the head and the target were stationary; "times-zero (X0) tracking," in which the target and head moved in the same direction at the same speed; and "times-two (X2) tracking," in which the target and head moved in opposite directions at the same speed. 3. Comparison of the eye velocities evoked by changes in the direction of X0 versus X2 tracking revealed two components of the tracking response. The earliest component, which we attribute to the VOR, had a latency of 14 ms and a trajectory that did not depend on initial tracking conditions. The later component had a latency of 70 ms or less and a trajectory that did depend on tracking conditions. 4. To probe the latency of pursuit eye movements, we imposed perturbations of target velocity imposed during X0 and X2 tracking. The resulting changes in eye velocity had latencies of at least 100 ms. We conclude that the effects of initial tracking conditions on eye velocity at latencies of less than 70 ms cannot be caused by visual feedback through the smooth-pursuit system. Instead, there must be another mechanism for short-latency control over the VOR; we call this component of the response "short-latency tracking." 5. Perturbations of head velocity or head and target velocity during X0 and X2 tracking showed that short-latency tracking depended only on the tracking conditions at the time the perturbation was imposed. The VOR appeared to be suppressed when the initial conditions were X0 tracking. 6. The magnitude of short-latency tracking depended on the speed of initial head and target movement. During X0 tracking at 15 deg/s, short-latency tracking was modest. When the initial speed of head and target motion was 60 deg/s, the amplitude of short-latency tracking was quite large and its latency became as short as 36 ms.(ABSTRACT TRUNCATED AT 400 WORDS)
The vestibular nerve of the chinchilla. III. Peripheral innervation patterns in the utricular macula
Authors: Fernandez C. , Goldberg J. M. , Baird R. A.
Published: December 2017

1. Nerve fibers supplying the utricular macula of the chinchilla were labeled by extracellular injection of horseradish peroxidase into the vestibular nerve. The peripheral terminations of individual fibers were reconstructed and related to the regions of the end organ they innervated and to the sizes of their parent axons. 2. The macula is divided into medial and lateral parts by the striola, a narrow zone that runs for almost the entire length of the sensory epithelium. The striola can be distinguished from the extrastriolar regions to either side of it by the wider spacing of its hair cells. Calyx endings in the striola have especially thick walls, and, unlike similar endings in the extrastriola, many of them innervate more than one hair cell. The striola occupies 10% of the sensory epithelium; the lateral extrastriola, 50%; and the medial extrastriola, 40%. 3. The utricular nerve penetrates the bony labyrinth anterior to the end organ. Axons reaching the anterior part of the sensory epithelium run directly through the connective tissue stroma. Those supplying more posterior regions first enter a fiber layer located at the bottom of the stroma. Approximately one-third of the axons bifurcate below the epithelium, usually within 5-20 microns of the basement membrane. Bifurcations are more common in fibers destined for the extrastriola than for the striola. 4. Both calyx and bouton endings were labeled. Calyces can be simple or complex. Simple calyces innervate individual hair cells, whereas complex calyces supply 2-4 adjacent hair cells. Complex endings are more heavily concentrated in the striola than in the extrastriola. Simple calyces and boutons are found in all parts of the epithelium. Calyces emerge from the parent axon or one of its thick branches. Boutons, whether en passant or terminal, are located on thin collaterals. 5. Fibers can be classified into calyx, bouton, or dimorphic categories. The first type only has calyx endings; the second, only bouton endings; and the third, both kinds of endings. Calyx units make up 6% of the labeled fibers, bouton units less than 2%, and dimorphic units greater than 92%. The three fiber types differ in the macular zones they supply and in the diameters of their parent axons. Calyx units were restricted to the striola. The few bouton units were found in the extrastriola.(ABSTRACT TRUNCATED AT 400 WORDS)
The vestibular nerve of the chinchilla. IV. Discharge properties of utricular afferents
Authors: Goldberg J. M. , Desmadryl G. , Baird R. A. , Fernandez C.
Published: December 2017

1. Extracellular recording techniques were used in the chinchilla to study the discharge properties of utricular afferents, including their discharge regularity, background discharge, and responses to both externally applied galvanic currents and centrifugal forces. 2. A normalized coefficient of variation (CV*), independent of discharge rate, was used to classify units as regularly (CV* less than 0.10), intermediate (0.10 less than or equal to CV* less than or equal to 0.20), or irregularly discharging (CV* greater than 0.20). In some circumstances, it was useful to recognize a group of very regularly discharging afferents (CV* less than 0.05). The CV* ranged from less than 0.020 to greater than 0.60. Regular units outnumbered irregular units by an approximate 3:1 ratio. The distribution of CV*s was bimodal: there was a major peak at CV* = 0.03 and a minor peak at CV* = 0.3. 3. Background rates were measured with the head in a horizontal position. Those of regular units usually fell between 40 and 80 spikes/s (mean: 54 spikes/s); those of irregular units were more broadly distributed (mean: 47 spikes/s). 4. Units were categorized in terms of the tilt directions resulting in increased discharge. There is a broad distribution of excitatory tilt directions with some units excited by ipsilateral rolls, others by contralateral rolls, some by nose-up pitches, and still others by nose-down pitches. In the chinchilla, there are almost equal numbers of units excited by ipsilateral or contralateral tilts. This is in contrast to previous findings in the cat and squirrel monkey, where the former units predominant by a 3:1 ratio. The difference can be related to the fact that the medial zone of the macula, where units excited by ipsilateral tilts reside, makes up a smaller proportion of the sensory epithelium in the chinchilla than in the monkey. 5. Galvanic sensitivity (beta *) and discharge regularity (CV*) were related by a power law, beta* = (CV*), with an exponent, b = 0.70. 6. Responses to sinusoidal centrifugal forces in the frequency range, f, between DC and 2 Hz were characterized by their gains (gf) and phases (phi f), taken with respect to peak linear force. Response linearity was studied by varying the amplitude of a 0.1-Hz sinusoid from 0.05 to 0.4 g. Nonlinear distortion was small (approximately 10%), as was the variation of gain (+/- 10%) and phase (+/- 5 degrees) with amplitude. 7. Response dynamics vary with discharge regularity. Very regular units are tonic. Their gains are typically 50 spikes.s-1/g and almost constant (+/- 10%) over the entire frequency range. Phases hover near zero with small (5 degrees) phase leads at low frequencies and slightly larger (10 degrees) phase lags at high frequencies. Irregular units are more phasic.(ABSTRACT TRUNCATED AT 400 WORDS)
Tonic descending influences on receptive-field properties of nociceptive dorsal horn neurons in sacral spinal cord of rat
Authors: Laird J. M. , Cervero F.
Published: December 2017

1. Single-unit electrical activity has been recorded from 34 dorsal horn neurons in the sacral segments (S1-2) of the spinal cord in halothane-anesthetized rats. All of the neurons had cutaneous receptive fields (RFs) on the rat's tail. The neurons were classified according to their responses to both innocuous and noxious mechanical stimulation of their RFs. Twenty-five cells were driven by both innocuous and noxious skin stimulation (multireceptive or class 2), and 9 neurons were driven only by noxious skin stimulation (nocireceptive or class 3). 2. The RF size, mechanical threshold, and afferent input properties of these neurons were determined in the intact anesthetized and spinalized states. Reversible spinalization was achieved by cooling the cervical spinal cord to 4 degrees C. 3. The class 2 neurons had a mean RF size of 919.8 +/- 112.0 (SE) mm2 in the intact animal. Fourteen of the 25 class 2 cells had larger RFs in the spinal state (mean increase = 330.0 mm2, SE = 79.2) and so were under tonic descending inhibition. Five neurons, all with C-fiber input, had smaller RFs (mean decrease = 247.6 mm2, SE = 136.6) and higher mechanical thresholds in the spinal state and so were under tonic descending excitation. Six neurons were unaffected by spinalization. 4. Five class 3 neurons recorded in the superficial dorsal horn had small RFs in the intact animal (mean = 201.0 mm2, SE = 48.8) and showed little or no change in RF size on spinalization (mean increase = 33.4 mm2, SE = 16.7), but their mechanical thresholds did decrease, indicating weak tonic descending inhibition. In contrast, four class 3 neurons recorded in the deep dorsal horn had larger RFs in the intact animal (mean = 566.8 mm2, SE = 156.8), and were under strong tonic descending inhibition, because they had much larger RFs (mean increase = 461.0 mm2, SE = 68.3), lower mechanical thresholds, and stronger C-fiber afferent input in the spinal state. 5. We conclude that the majority of nociceptive dorsal horn neurons are subject to a net tonic descending control of their RF properties. The class 2 neurons in the deep dorsal horn appear to be a heterogeneous population, some cells being under tonic descending excitation and others under tonic descending inhibition. Class 3 cells can be separated into those located in the superficial dorsal horn, whose RF properties show very little change on spinalization, and those in the deep dorsal horn, whose RF properties change markedly on spinalization.(ABSTRACT TRUNCATED AT 400 WORDS)
Neurotransmitter receptors mediating excitatory input to cells in the cat lateral geniculate nucleus. I. Lagged cells
Authors: Heggelund P. , Hartveit E.
Published: December 2017

1. Synaptic mechanisms that might explain the functional properties of the recently discovered class of lagged cells in the dorsal lateral geniculate nucleus (LGN) were analyzed with electrophysiological and pharmacologic techniques. To study the type of excitatory amino acid (EAA) receptor that mediates visual responses of lagged cells, we recorded the response of single cells to a stationary flashing light spot before, during, and after microiontophoretic application of antagonists and agonists to EAA receptors. 2. The visual response of the lagged cells could be almost completely blocked by an antagonist to the N-methyl-D-aspartate (NMDA) receptor. The degree of suppression was dose dependent, and the average maximum degree of suppression for all the cells was 94%. NMDA enhanced the response, and this enhancement was antagonized by NMDA antagonists. A quisqualate/kainate receptor antagonist had no significant effect on the lagged cells. 3. These findings indicate that the visual response in lagged cells is dependent upon activation of NMDA receptors, which may directly result from activation of retinal inputs. 4. No pharmacologic difference was seen between lagged X- and Y-cells, or between lagged ON- and OFF-center cells. 5. gamma-Aminobutyric acid-A (GABA-A) receptor antagonists were used to study whether the characteristic lag of the visual response and the suppression of the initial transient response component of the lagged cells are dependent on geniculate inhibition. Beside enhancement of the visual response, the GABA antagonists strongly reduced the lag of the visual response, and an initial transient response component occurred instead of the initial suppression. The lag remained slightly longer than for nonlagged cells, and the peak firing rate of the transient was below values typical for nonlagged cells, indicating that the lagged cell properties are dependent on other factors beside GABA-A receptor-mediated inhibition. 6. The enhanced visual response during iontophoresis of GABA antagonists could be completely blocked by simultaneous iontophoresis of an NMDA-receptor antagonist. This gives further support to the hypothesis that the retinal input to these cells is mediated by NMDA receptors. 7. The NMDA-receptor/ionophore complex mediates excitatory postsynaptic potentials (EPSPs) characterized by slow rise and decay times and long duration. The ionophore is characterized by a voltage-dependent blockade that makes these receptors particularly sensitive to inhibitory input. The temporal interplay between the slow NMDA receptor-mediated EPSPs and the fast GABA receptor-mediated inhibitory postsynaptic potentials (IPSPs) may explain the characteristic response properties of the lagged cells.
Excitation and inhibition of the heart of the snail, Lymnaea, by non-FMRFamidergic motoneurons
Authors: Buckett K. J. , Peters M. , Benjamin P. R.
Published: December 2017

1. The present paper extends the model of neuronal control of the Lymnaea heart by the use of intracellular recording techniques to identify further types of cardioactive neurons in the CNS that, like the previously described E heart excitor (Ehe) cells, influence the myogenic heartbeat. 2. Four new types of neuron that act on the heart are described. These are excitatory Hhe and She cells (H and S heart excitors) and the inhibitory Khi cell (K heart inhibitor). The fourth class, tonus pericardium excitor (Tpe), modulates the heart by action on pericardial tissue. 3. Pharmacologic, electrophysiological, and anatomic evidence is presented that shows that these cells are motoneurons, innervating heart muscle fibers directly: blocking central chemical synapses failed to prevent the actions of the neurons on the heart; simultaneous intracellular recordings showed unitary EJPs in heart muscle after 1:1 and with constant delay from evoked neuronal action potentials; intracellular injection of the dye Lucifer yellow showed all cells had axonal branches entering the intestinal nerve (which innervates the heart). 4. The use of selective antagonists to 5-hydroxytryptamine (5-HT) (cinanserin), dopamine (ergonovine), and acetylcholine (alpha-bungarotoxin) provided evidence that the actions of She and Hhe cells are mediated by 5-HT, whereas those of the Khi cell are mediated by acetylcholine. 5. A cyclically active network of three interneuronal inputs acting on the heart motoneurons is described. 6. One of these, input 3, is responsible for periodic excitation of the heart via its effects on the Hhe cells.
Single-unit selectivity to azimuthal direction and sound pressure level of noise bursts in cat high-frequency primary auditory cortex
Authors: Imig T. J. , Irons W. A. , Samson F. R.
Published: December 2017

1. The azimuth and sound pressure level (SPL) selectivities of single-unit responses recorded in primary auditory cortex of barbiturate-anesthetized cats were studied by the use of broadband noise bursts delivered in the free field from a moveable loud-speaker. The experiments were carried out with cats located inside a quasianechoic sound-isolation chamber. We studied 71 units with relatively stable response properties. All units were located in the frequency representation between 5.8 and 31 kHz. The data obtained for each unit were displayed as an azimuth-level response area, a contour plot that displays the distribution of response magnitude as a joint function of SPL and azimuth at 0 degrees elevation. From these, azimuth and level functions were obtained to derive descriptors of azimuth and level selectivity. 2. Sensitivity to sound-source azimuth was assessed from the modulation of the average azimuth function (average of azimuth functions obtained to each SPL of noise that was presented) for each unit. The sample was arbitrarily divided into a high-directionality (HD) group (66%) whose average azimuth functions had modulation values of greater than or equal to 75% and a low-directionality (LD) group (34%). The distinction between HD and LD groups was made so that we could analyze the characteristics of units likely to be involved in the representation of sound-source azimuth. 3. There is an overrepresentation of the contralateral sound field and the midline in the sample of HD units. The preferred sector for each unit was defined as the range of azimuths within the frontal sound field throughout which unit response was greater than or equal to 75% of maximum. Each unit was classified as either midline preferring (17%, the midpoint of the preferred sector, i.e., best azimuth, was located within 5 degrees of the midline), contralateral preferring (60%), or ipsilateral preferring (23%). The ratio of contralateral- to ipsilateral-preferring units was 2.5:1. A higher proportion of units had best azimuths located in the 10 degrees sector centered on the midline than in any other 10 degrees sector of the frontal sound field. 4. In one animal, recordings were obtained at seven closely spaced sites in layer IV from single- and multiunit responses, which were narrowly tuned to both azimuth and SPL. The units located along a 1-mm length of an isofrequency strip were tuned to similar frequencies and SPLs but had five distinctly different directional preferences distributed throughout the entire frontal sound field.(ABSTRACT TRUNCATED AT 400 WORDS)
A reevaluation of excitatory amino acid-mediated synaptic transmission in rat dentate gyrus
Authors: Lambert J. D. , Jones R. S.
Published: December 2017

1. Intracellular recordings were made from granule cells in combined slices of the hippocampus and parahippocampal cortex from adult Wistar rats. The neurons had a mean resting membrane potential (EM) of -85.1 +/- 0.7 (SE) mV, input resistance (Rin) of 30.9 +/- 1.5 M omega and action potential (AP) amplitude of 79.9 +/- 1.06 mV measured from the threshold potential. The threshold for AP generation was approximately 40 mV positive to EM. 2. The passive current-voltage relationship showed anomalous rectification, with Rin increasing by 34% on average at modest depolarizations. With large excursions of the EM (by +/- 30 mV or more), there was a marked fall in Rin. 3. With extracellular recording, a monophasic, positive-going field potential of 5–15 mV was evoked by stimulation of the perforant path (PP). Intracellularly, an excitatory postsynaptic potential (EPSP) of up to 40 mV in size was recorded. It was unusual to evoke an AP on orthodromic stimulation. Perfusion with picrotoxin (PTX, up to 20 microM) had small and variable effects on the EPSP, which implies that GABAergic inhibition does not play a major role. 4. Tonic depolarization reduced the EPSP. Hyperpolarization either had no effect or again decreased the EPSP. 5. The role of excitatory amino acid (EAA) receptor subtypes in mediation of the EPSP was investigated. Perfusion with the non-N-methyl-D-aspartate (NMDA) receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) caused a dose-dependent reduction of the EPSP with a shift to the right of the input-output relationship. The ED50 for this effect was approximately 2 microM. 6. In the presence of 5–10 microM CNQX a small component of the EPSP usually remained, which could be blocked by the NMDA receptor antagonist +/- 2-amino-5-phosphonovaleric acid (APV, 20–50 microM). This depolarizing component was markedly enhanced during perfusion with Mg2(+)-free medium. It increased in size and duration when the membrane was depolarized and decreased with hyperpolarization. These properties are consistent with the mediation of this potential via NMDA receptors. 7. These results indicate that NMDA receptors contribute to transmission at the synapse between the PP and the granule cell. This was confirmed by demonstrating that APV caused a small reduction in the size of the untreated EPSP and a shortening of the recovery phase.(ABSTRACT TRUNCATED AT 400 WORDS)
Kinematic analysis of the defense response in crayfish
Authors: Kelly T. M. , Chapple W. D.
Published: December 2017

1. A threatening visual stimulus frequently elicits the defense response (DR) in crayfish, a behavior that comprises orienting the body to face the stimulus, raising the thorax, and extending and opening the claws. Although this behavior has been reported previously, its kinematics have not been characterized. This work employs kinematic analysis to provide a quantitative description of the claw (cheliped) as it is moved during the DR. 2. The cheliped was modeled as an open kinematic chain with three segments and 4 df. Simulations employing the model were compared with actual cheliped trajectories during the DR to ascertain the applicability of the model. The model was then employed to demonstrate the effects of individual joint rotations on the overall trajectory of the claw. 3. The individual segments of the cheliped were monitored during the DR, and spatial trajectories, tangential velocities, and intersegmental joint angles were calculated. 4. The joint angles assumed at the final position of the DR were highly stereotyped. This constancy in joint angle at the endpoint of the movement stands in contrast to the variability in both the angular and spatial trajectories of the cheliped as it was moved towards the final position. 5. Movement time was relatively constant. Larger amplitude movements were performed with a proportional increase in velocity similar to arm movements in primates. 6. The DR positions the cheliped in a fixed location in the workspace. Unlike the primate arm during reaching, the cheliped does not proceed towards the endpoint with a smooth controlled trajectory characteristic of a system with fine interjoint coordination. Instead, it appears that individual joint rotations are performed independently, thus precluding trajectory control although permitting an accurate specification of the endpoint.A
Background-induced flicker enhancement in cat retinal horizontal cells. I. Temporal and spectral properties
Authors: Pflug R. , Nelson R. , Ahnelt P. K.
Published: December 2017

1. Dim backgrounds can enhance small-spot flicker responses of cat retinal horizontal cells by a factor of 2 or more. 2. Intracellular marking with horseradish peroxidase (HRP) reveals that this enhancement effect occurs in--but is not necessarily limited to--the cone-connected, A-type horizontal cell. 3. Flicker amplitudes decrease over a frequency range from 3 to 36 Hz of square-wave photic stimulation. There is little evidence of flicker-response enhancement at 3 Hz. Flicker-response enhancement is typically 2-6 times larger at 35 than at 6 Hz. 4. Inspection of flicker waveforms indicates both a scaling-up of response signals with backgrounds and a distortion composed of 2- to 5-ms-latency decrease, expressed primarily within a quick component of OFF-repolarization. 5. Flicker enhancement first increases as a function of background irradiance and then decreases. The increasing limb has the dynamic range and spectral sensitivity of cat rods (507-nm peak). Enhancement is maintained during rod after-effects. The decreasing limb of the background-versus-intensity function results from light adaptation of cat, long-wavelength (red) cones. 6. The flicker responses themselves peak spectrally at approximately 555 nm and reflect only the activity of cat long-wavelength (red) cones, without evidence of intermixing of other photoreceptor mechanisms. 7. Thus within the first synaptic layer of the cat visual system, rod signals interact with the flicker responses of red cones, both increasing cone-signal amplitudes and modifying cone-signal waveforms. 8. The results are closely analogous to "suppressive rod-cone interaction" (SRCI) as described in human psychophysics. 9. An outer-plexiform-layer circuit involving rods, horizontal cells and cones may mediate rod-induced enhancement of cone flicker. This being the case, notions of horizontal-cell feedback interactions with cones may have to be modified and extended. A specific feedback model is elaborated in the companion paper.
Temporal encoding of two-dimensional patterns by single units in primate primary visual cortex. II. Information transmission
Authors: Richmond B. J. , Optican L. M.
Published: December 2017

1. Previously, we studied how picture information was processed by neurons in inferior temporal cortex. We found that responses varying in both response strength and temporal waveform carried information about briefly flashed stationary black-and-white patterns. Now, we have applied that same paradigm to the study of striate cortical neurons. 2. In this approach the responses to a set of basic black and white pictures were quantified through use of a set of basic waveforms, the principal components (extracted from all the responses of each neuron). We found that the first principal component, which corresponds to the response strength, and others, which correspond to different basic temporal activity patterns, were significantly related to the stimuli, i.e., the stimulus drove both the response strength and its temporal pattern. 3. Our previous study had shown that, when information theory was used to quantify the stimulus-response relation, inferior temporal neurons convey over twice as much information in a response code that includes temporal modulation as in a response code that includes only the response strength. This study shows that striate cortical neurons also carry twice as much information in a temporal code as in a response strength code. Thus single visual neurons at both ends of a cortical processing chain for visual pattern use a multidimensional temporal code to carry stimulus-related information. 4. These results support our multiplex-filter hypothesis, which states that single visual system neurons can be regarded as several simultaneously active parallel channels, each of which conveys independent information about the stimulus.
Contributions of arachidonic acid derivatives and substance P to the sensitization of cutaneous nociceptors
Authors: Cohen R. H. , Perl E. R.
Published: December 2017

1. The role of presumed chemical mediators of inflammation in the heat-induced sensitization of cutaneous C-polymodal nociceptors (CPNs) was examined in a rabbit ear preparation maintained in vitro by intra-arterial perfusion with a solution free of protein and cellular elements. 2. In this preparation, CPNs consistently showed enhanced responsiveness after repeated exposure of their receptive fields to noxious levels of heat. The average magnitude of sensitization was quantitatively similar to that observed in vivo, suggesting that blood-born factors are not essential for development of sensitization. 3. Sensitization in one-half of randomly selected CPNs was blocked or reduced when the perfusate contained a cyclooxygenase inhibitor, indomethacin or dipyrone, or the dual cyclooxygenase/lipoxygenase inhibitor, BW755C, even though initial responsiveness to heat and pressure was unaltered. These observations suggest that arachidonic acid breakdown products, possibly prostaglandins, are intermediaries in the sensitization of some, but not all, C-fiber nociceptors of the skin. In addition, heat-induced sensitization for some C-fiber cutaneous nociceptors is the result of processes that are at least partially independent of those involved in excitation. 4. Substance P (SP) or the putative SP antagonists, [D-Pro2, D-Trp7.9]-SP or [D-Pro2, D-Phe7, D-Trip9]-SP, produced no significant effect on heat-responsiveness or sensitization, although ongoing activity may have marginally increased over control levels after repeated heat stimulations. We conclude that SP in an in vitro preparation is not involved in the enhancement of cutaneous C-fiber nociceptor responsiveness after repeated thermal insults.
Primate frontal eye fields. III. Maintenance of a spatially accurate saccade signal
Authors: Goldberg M. E. , Bruce C. J.
Published: December 2017

1. We studied the activity of single neurons in the monkey frontal eye fields during oculomotor tasks designed to assess the activity of these neurons when there was a dissonance between the spatial location of a target and its position on the retina. 2. Neurons with presaccadic activity were first studied to determine their receptive or movement fields and to classify them as visual, visuomovement, or movement cells with the use of the criteria described previously (Bruce and Goldberg 1985). The neurons were then studied by the use of double-step tasks that dissociated the retinal coordinates of visual targets from the dimensions of saccadic eye movements necessary to acquire those targets. These tasks required that the monkeys make two successive saccades to follow two sequentially flashed targets. Because the second target disappeared before the first saccade occurred, the dimensions of the second saccade could not be based solely on the retinal coordinates of the target but also depended on the dimensions of the first saccade. We used two versions of the double-step task. In one version neither target appeared in the cell's receptive or movement field, but the second eye movement was the optimum amplitude and direction for the cell (right-EM/wrong-RF task). In the other the second stimulus appeared in the cell's receptive field, but neither eye movement was appropriate for the cell (wrong-EM/right-RF task). 3. Most frontal-eye-field cells discharged in the right-EM/wrong-RF version of the double-step task. Their discharge began after the first saccade and continued until the second saccade was made. They usually discharged even on occasional trials in which the monkey failed to make the second saccade. They discharged much less, or not at all, in the wrong-EM/right-RF version of the double-step paradigm. Thus most presaccadic cells in the frontal eye fields were tuned to the dimensions of saccadic eye movements rather than to the coordinates of retinal stimulation. 4. Eleven movement cells (including 1 which also had independent postsaccadic activity for saccades opposite its presaccadic movement field) were studied, and all had significant activity in the right-EM/wrong-RF task. 5. Almost all (28/32) visuomovement cells, including 12 with independent postsaccadic activity, discharged in the right-EM/wrong-RF task. None of the four that failed had independent postsaccadic activity. 6. The majority (26/40) of visual cells were responsive in the right-EM/wrong-RF task.(ABSTRACT TRUNCATED AT 400 WORDS)
Gaze control in the cat: studies and modeling of the coupling between orienting eye and head movements in different behavioral tasks
Authors: Guitton D. , Munoz D. P. , Galiana H. L.
Published: December 2017

1. Orienting movements, consisting of coordinated eye and head displacements, direct the visual axis to the source of a sensory stimulus. A recent hypothesis suggests that the CNS may control gaze position (gaze = eye-relative-to-space = eye-relative-to-head + head-relative-to-space) by the use of a feedback circuit wherein an internally derived representation of gaze motor error drives both eye and head premotor circuits. In this paper we examine the effect of behavioral task on the individual and summed trajectories of horizontal eye- and head-orienting movements to gain more insight into how the eyes and head are coupled and controlled in different behavioral situations. 2. Cats whose heads were either restrained (head-fixed) or unrestrained (head-free) were trained to make orienting movements of any desired amplitude in a simple cat-and-mouse game we call the barrier paradigm. A rectangular opaque barrier was placed in front of the hungry animal who either oriented to a food target that was visible to one side of the barrier or oriented to a location on an edge of the barrier where it predicted the target would reappear from behind the barrier. 3. The dynamics (e.g., maximum velocity) and duration of eye- and head-orienting movements were affected by the task. Saccadic eye movements (head-fixed) elicited by the visible target attained greater velocity and had shorter durations than comparable amplitude saccades directed toward the predicted target. A similar observation has been made in human and monkey. In addition, when the head was unrestrained both the eye and head movements (and therefore gaze movements) were faster and shorter in the visible- compared with the predicted-target conditions. Nevertheless, the relative contributions of the eye and head to the overall gaze displacement remained task independent: i.e., the distance traveled by the eye and head movements was determined by the size of the gaze shift only. This relationship was maintained because the velocities of the eye and head movements covaried in the different behavioral situations. Gaze-velocity profiles also had characteristic shapes that were dependent on task. In the predicted-target condition these profiles tended to have flattened peaks, whereas when the target was visible the peaks were sharper. 4. Presentation of a visual cue (e.g., reappearance of food target) immediately before (less than 50 ms) the onset of a gaze shift to a predicted target triggered a midflight increase in first the eye- and, after approximately 20 ms, the head-movement velocity.(ABSTRACT TRUNCATED AT 400 WORDS)