bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular factors influencing GABA response in hippocampal pyramidal cells
Authors: Wong R. K. , Watkins D. J.
Published: December 2017

1. The action of gamma-aminobutyric acid (GABA) on the hippocampal pyramidal cells was studied by intracellular recordings using an in vitro slice preparation. 2. Orthodromic tetanic stimulation induced dramatic modifications of the GABA response. Initial hyperpolarizing GABA responses were observed to invert to depolarizations following the tetanic shock. 3. The hyperpolarizing and depolarizing GABA responses exhibited differential sensitivity to GABA and bicuculline. Application of low concentrations of GABA predominantly activated the hyperpolarizing response. Activation of depolarizing response in both the dendrites and somata required a larger quantity of GABA. Bicuculline antagonized both the hyperpolarizing and depolarizing responses; however, the agent appeared to exert a stronger influence on the depolarizing response. At the concentration of 10(-5) M, bicuculline completely blocked the depolarizing response while the hyperpolarizing response was only suppressed by 50%. 4. During prolonged periods of GABA application (10 s or more), the GABA-induced conductance increase was not maintained, suggesting that the GABA response underwent desensitization. The results also suggest that the desensitization process affected both the hyperpolarizing and depolarizing responses. 5. The depolarizing response elicited by GABA was facilitated by increasing the extracellular potassium concentration. 6. It is possible that the modification of the GABA response following tetanic stimulation is in part caused by the desensitization of the GABA response and an accumulation of extracellular K+ and GABA.
Activity of myotomal motoneurons during fictive swimming in frog embryos
Authors: Soffe S. R. , Roberts A.
Published: December 2017

1. Dye-filled microelectrodes have been used to identify and to examine the electrical activity of spinal cord motoneurons during fictive swimming in amphibian embryos. 2. Impaled neurons all had ventral cell bodies, dorsal, lateral, or ventral dendrites, and most showed either damaged or complete peripheral axons projecting out to the myotomes. It was rarely possible to identify cells by recording 1:1 motor root spikes evoked by intracellular current pulses. 3. During fictive swimming, motoneurons are tonically depolarized, fire 1 spike per swimming cycle, and are inhibited in phase with motor root activity on the opposite side. Motoneurons can also fire synchronously on the two sides, at double the normal swimming frequency. They occasionally also show a pattern of lower frequency alternating activity in which there is a prolonged burst of discharge on each cycle.
Tonic and phasic synaptic input to spinal cord motoneurons during fictive locomotion in frog embryos
Authors: Soffe S. R. , Roberts A.
Published: December 2017

1. In curarized, late developmental stage Xenopus embryos, episodes of rhythmic motor root discharge, termed fictive swimming (17), may be evoked by touch or by dimming the lights, as in unparalyzed animals. Motoneurons are tonically depolarized throughout each episode, are phasically excited to fire 1 spike per cycle, and receive a midcycle inhibitory postsynaptic potential (IPSP) in phase with motor root activity on the opposite side. 2. Rostral hemisection of the spinal cord abolishes motor root discharge on the operated side caudal to the cut but leaves activity on the intact side unaffected. In motoneurons, the tonic depolarization is abolished on the hemisected side but is still present on the intact side. This is evidence that the tonic depolarization is a descending drive. 3. Midcycle IPSPs normally seen in motoneurons during fictive swimming are abolished by rostral hemisection of the opposite side of the cord but are still recorded on the cut side. The simplest conclusion is that the inhibitory interneurons responsible lie on the opposite side of the spinal cord to the motoneurons they inhibit, and so represent a reciprocal inhibitory pathway. 4. The phasic excitatory postsynaptic potentials (EPSPs), which drive motoneuron spikes during swimming, are still present on the intact side of a rostrally hemisected cord but are abolished on the operated side. We conclude that the excitatory interneurons responsible lie on the same side of the cord as the motoneurons they excite.
Mechanisms of neocortical epileptogenesis in vitro
Authors: Gutnick M. J. , Connors B. W. , Prince D. A.
Published: December 2017

1. The cellular mechanisms underlying interictal epileptogenesis have been examined in an in vitro slice preparation of guinea pig neocortex. Penicillin or bicuculline was applied to the tissue, and intracellular recordings were obtained from neurons and glia. 2. Following convulsant application, stimulation could elicit a short-latency excitatory postsynaptic potential (EPSP) and a large, longer latency depolarization shift (DS) in single neurons. DSs in neurons of the slice were very similar to those evoked in neurons of neocortex in vivo in that they displayed an all-or-none character, large shifts in latency during repetitive stimuli, long afterpotentials, and a prolonged refractory period. In contrast to epileptogenesis produced by penicillin in intact cortex, neither spontaneous DSs nor ictal episodes were observed in neocortical slices. 3. In simultaneous recordings from pairs of neurons within the same cortical column, DS generation and latency shifts were invariably synchronous. DS generation in neurons was also coincident with large, paroxysmal increases of extracellular [K+], as indicated by simultaneous recordings from glia. 4. When polarizing currents were applied to neurons injected with the local anesthetic QX-314, the DS amplitude varied monotonically and had an extrapolated reversal potential near 0 mV. In neurons injected with the K+-current blocker Cs+, large displacements of membrane potential were possible, and both the short-latency EPSP and the peak of the DS diminished completely at about 0 mV. At potentials positive to this, the short-latency EPSP was reversed, and the DS was replaced by a paroxysmal hyperpolarization whose rise time and peak latency were prolonged compared to the DS evoked at resting potential. The paroxysmal hyperpolarization probably represents the prolonged activation of the impaled neuron by EPSPs. 5. Voltage-dependent components, including slow spikes, appeared to contribute to generation of the DS at resting potential in Cs+-filled cells, and these components were blocked during large depolarizations. 6. The results suggest that DS generation in single neocortical neurons occurs during synchronous synaptic activation of a large group of cells. DS onset in a given neuron is determined by the timing of a variable-latency excitatory input that differs from the short-latency EPSP. The DS slow envelope appears to be generated by long-duration excitatory synaptic currents and may be modulated by intrinsic voltage-dependent membrane conductances. 7. We present a hypothesis for the initiation of the DS, based on the anatomical and physiological organization of the intrinsic neocortical circuits.
Functional organization of neurons in cat striate cortex: variations in ocular dominance and receptive-field type with cortical laminae and location in visual field
Authors: Berman N. , Payne B. R. , Labar D. R. , Murphy E. H.
Published: December 2017

1. Binocularity and receptive-field type of cortical neurons were assessed relative to the cortical layer in which the neurons were recorded and to receptive-field position in the visual field. 2. Receptive fields were observed up to 2 degrees into the ipsilateral half of the visual field. In the region up to 2 degrees on either side of the vertical meridian, the relative contribution of the ipsilateral eye was reduced. This progression in ocular dominance from ipsilateral to contralateral visual field agrees well with the distribution of X-cells about the nasotemporal division. 3. The region of maximum binocularity in each hemifield was found to be a 12 degree wide vertical strip extending from the vertical meridian to 12 degrees contralateral. In the representation of the central 12 degree strip, most units in all cortical layers were binocular. 4. Low levels of binocularity were observed at a considerable distance before the monocular portion of the visual field was reached. 5. The decrease in binocularity for simple cells occurred closer to the vertical meridian than for complex cells. 6. The proportions of cells classified as simple or complex did not change with position in the visual field. 7. At all locations in the visual field, complex cells showed a higher percentage of binocularity than simple cells. 8. The proportions of two types of simple cells, I and II, and complex cells were variable between cortical layers. Layer IV contained predominantly simple II cells, whereas layer V contained predominantly complex cells. 9. The results are discussed in terms of visual perception and the dynamic pattern of visual stimulation around a moving animal, the optic flow field.
Mechanisms underlying pattern generation in lobster stomatogastric ganglion as determined by selective inactivation of identified neurons. III. Synaptic connections of electrically coupled pyloric neurons
Authors: Eisen J. S. , Marder E.
Published: December 2017

1. The pyloric dilator (PD) and anterior burster (AB) neurons in the pyloric system of the lobster stomatogastric ganglion are electrically coupled and synchronously active. We have used the lucifer yellow photoinactivation technique to separate the connections made by the PD motor neurons from those made by the AB interneuron. 2. Photoinactivation of either the two PD neurons or the single AB neuron allowed us to separate the compound inhibitory postsynaptic potentials (IPSPs) in the lateral pyloric (LP) and pyloric (PY) motor neurons resulting from synchronous PD and AB activity into AB-evoked and PD-evoked components. These IPSPs have different time courses, reversal potentials, ion selectivities, and pharmacological properties. 3. Photoinactivation and membrane-potential manipulations indicated that a readily observable IPSP recorded in the AB neuron and correlated with action potentials in the LP neuron is actually an electrotonic potential due to an LP-evoked IPSP in the PD neurons. 4. Selective inactivation of either the two PD neurons or the AB neuron revealed that the IPSP recorded in the ventricular dilator (VD) motor neuron is due solely to AB-released transmitter. 5. The electrical coupling potentials measurable between the AB, PD, and VD neuron somata are due to direct electrical coupling between all of these neurons. 6. Circuit analysis and transmitter identification may be complicated by electrical coupling. We suggest that the presence of electrical coupling between nonidentical neurons may provide a new mechanism that allows changes in synaptic characteristics among neurons within a "hard-wired" circuit.
A further examination of effects of cortical stimulation on primate spinothalamic tract cells
Authors: Yezierski R. P. , Gerhart K. D. , Schrock B. J. , Willis W. D.
Published: December 2017

1. Stimulation of the sensorimotor cortex was found to excite and/or inhibit nociceptive spinothalamic tract cells. Thirteen wide dynamic range cells were inhibited by cortical stimulation, 6 were excited and 14 were both excited and inhibited. Four of six high-threshold cells were excited and one was inhibited. 2. Intermediate (200 ms) or long (2 s) duration conditioning trains were effective in reducing responses of spinothalamic cells evoked by noxious mechanical or thermal stimuli and by A- and C-fiber volleys in the sural nerve. Preferential inhibition of low-threshold responses with little or no effect on high-threshold discharges was observed in some cases. 3. Inhibitory actions were obtained primarily from stimulation of the SI sensory cortex and area 5, while excitation or excitation followed by inhibition was the dominant effect from motor cortex (area 4). Spinothalamic cells were also excited by stimulation of the medullary pyramid. 4. In eight animals extensive mapping of the sensorimotor cortex showed that for a given cell, stimulation of the sensory cortex produced inhibition while stimulation of motor cortex resulted in excitation. 5. The average latency of inhibition from sensory cortex was 29.8 +/- 10 ms, while the average latency of excitation from motor cortex was significantly shorter, 13.5 +/- 9 ms. The shortest latencies for excitation from pyramidal stimulation in the cases evaluated ranged from 2 to 9 ms. 6. Spinal cord lesions were made in five animals to determine the descending pathway(s) mediating corticofugal effects. Cortical and pyramidal effects were eliminated or considerably reduced by lesions involving the dorsal part of the lateral funiculus. This observation combined with latency data suggest that the corticospinal tract may be involved in the mediation of cortical excitation, while both pyramidal and extrapyramidal pathways are likely to be involved in cortical inhibition.
Activity of cells in area 17 of the cat in absence of input from layer a of lateral geniculate nucleus
Authors: Malpeli J. G.
Published: December 2017

1. Injections of 4 mM cobaltous chloride were used to block synaptic transmission in layer A of the lateral geniculate nucleus (LGN) without blocking fibers of passage going to or arising from other layers. 2. Selective inactivation of geniculate layer A virtually abolished all visual activity in cortical layers 4ab, 4c, and 6. Under these conditions, the stimulus-evoked response, orientation selectivity, and direction selectivity of cells in layers 2 and 3 were not seriously affected. In layer 5, the effects of the block were more variable, with special complex cells least affected and simple cells most affected. 3. Since the organization of complex receptive fields and the maintenance of normal orientation selectivity in supragranular layers survive disruption of major interlaminar interactions, it appears that much of the functional architecture of cat striate cortex does not depend on the integrity of the column. 4. These results support the idea that each layer of the LGN is a functional unit with a unique pattern of access to the various layers of visual cortex.
Distribution of electrotonic synapses on identified lamprey neurons: a comparison of a model prediction with an electron microscopic analysis
Authors: Christensen B. N.
Published: December 2017

1. Intracellular recordings of the monosynaptic excitatory postsynaptic potential (EPSP) were made from an identified giant interneuron in the lamprey spinal cord following stimulation of a single identified presynaptic giant axon. The EPSP had both electrotonic and chemical components. 2. The giant interneuron and sometimes the giant axon were labeled with horseradish peroxidase (HRP). Using combined light and electron microscopy (EM), gap junctions formed by the axon on the HRP-labeled dendritic trees of seven interneurons were identified and their position marked on dendritic diagrams made from tracings of the cells. 3. The total number of gap junctions on a giant interneuron varied from a minimum of 9 to a maximum of 23. The number of gap junctions on a branch of a dendritic tree varied from 1 to 9. For all seven neurons the closest gap junction was located approximately 65 microns from the soma and the furthest 280 microns from the soma. 4. When gap junction position was plotted as a function of electrotonic distance from the soma, the variability in their distribution decreased significantly. Synaptic location was found to be on the average about 0.5 space constants from the soma, and this value compared favorably with that determined from an analysis of half-width and rise time of the electrotonic synaptic potential for these neurons. 5. These results suggest that the presynaptic axon tends to make, on the average, synaptic contact at the same electrical distance from the soma.
Physiological effects of unequal alternating monocular exposure
Authors: Tieman D. G. , McCall M. A. , Hirsch H. V.
Published: December 2017

1. In order to investigate the effects of an imbalance in stimulation to the eyes without the confounding influence of continuous deprivation of one eye, we reared cats with unequal alternating monocular exposure (AME) and, for comparison, cats with equal AME. We recorded extracellularly from single cells in area 17 of visual cortex. 2. For unequal AME cats, a majority of the cells that were visually responsive were dominated by the eye that had received more patterned visual experience. The percentage of cells dominated by the more experienced eye was greater with a large imbalance in stimulation to the two eyes (AME 8/1, 77%) than with a small imbalance (AME 8/4, 62%). 3. For both equal AME cats and unequal AME cats, we obtained evidence for differences in cells activated by the contralateral and by the ipsilateral afferents. a) In equal AME cats receiving only 1 h of exposure per day, we obtained a greater dominance by the contralateral eye (60%) than in equal AME cats receiving 8 h of exposure per day (42%). b) Although a large imbalance in stimulation (AME 8/1) resulted in a shift in ocular dominance in both cortical hemispheres, a moderate imbalance (AME 8/4) resulted in a smaller shift, which was apparent only in the hemisphere ipsilateral to the less-experienced eye. 4. The percentage of cortical cells responsive to each eye was uniform throughout the depth of cortex. Thus, for the unequal AME cats, cells activated by the less-experienced eye were no more frequent in layer IV of visual cortex than in the infragranular and supragranular layers. 5. Although almost all cells recorded from AME cats had relatively normal receptive-field properties, three receptive-field properties of cells in unequal AME cats showed an effect of the rearing. In each case cells dominated by the less-experienced eye and recorded in the cortical hemisphere ipsilateral to it showed the largest changes. These cells a) were more poorly tuned, b) had lower cutoff velocities, and c) had smaller receptive fields. 6. It is suggested that cortical cells that putatively receive Y-cell afferents from the dorsal lateral geniculate nucleus (LGNd) are more affected by an imbalance in stimulation than are cortical cells that putatively receive X-cell afferents. Thus, the decrease in mean receptive-field area and cutoff velocity for the cells dominated by the less-experienced eye is suggested to be due to a greater shift in ocular dominance by the cortical cells receiving Y-cell afferents from the LGNd. 7. The interaction between binocular competition and deprivation of pattern vision may contribute to differences between monocularly deprived cats and unequal AME cats.
Identified cholinergic neurons R2 and LPl1 control mucus release in Aplysia
Authors: Rayport S. G. , Ambron R. T. , Babiarz J.
Published: December 2017

1. R2 and LPl1 are homologous giant cholinergic neurons in the nervous system of Aplysia with overlapping and almost symmetrical axonal trees extending over most of the body wall. In spite of much experimental study, the behavioral role of the cells has remained unknown. 2. After intrasomatic injection of R2 and LPl1 with horseradish peroxidase (HRP), the giant cell axons were traced to the periphery and found to contact subepidermal glands in the body wall exclusively. 3. The axons penetrated the glandular basal lamina, indenting the gland cell cytoplasm, and expanded into varicosities containing putative cholinergic transmissive sites. 4. Histochemical characterization of the contents of the glands showed that they contain mucus, suggesting that the giant cells control mucus release from the body wall. 5. Stimulation of R2 or LPl1 resulted in glandular discharge, as measured both by an increase in the appearance of protein and of mucus on the body wall. 6. R2 and LPl1 control mucus release from the body wall, thus providing a new system for investigations of neuroglandular control as well as a behavioral context for cellular studies using these two neurons.
Direct and indirect visual inputs to superficial layers of cat superior colliculus: a current source-density analysis of electrically evoked potentials
Authors: Freeman B. , Singer W.
Published: December 2017

1. The spatiotemporal pattern of visual inputs to the stratum griseum superficiale (SGS) and stratum opticum (SO) of the cat superior colliculus (SC) has been determined by an analysis of the current sinks occurring during postsynaptic activity following stimulation of each optic nerve (ON) and the optic chiasm (OX). Electrolytic lesions were used to determine the locations of the five major current sinks. 2. Direct SC afferents from the contralateral ON induced three current sinks whose maxima were located a) in the upper part of the SGS, b) in the middle part of the SGS, and c) in the lower part of the SGS and upper part of the SO. These three sinks were generated by three afferent fiber groups conducting in the optic nerve with modal and maximum velocities, respectively, of a) 4 and 5 m/s (slow W-group), b) 7 and 10 m/s (fast W-group), and c) 32 and 43 m/s (Y-group). 3. Indirect SC inputs from the contralateral ON via the ipsilateral visual cortex were identified by comparing the pattern of current sinks generated by OX stimulation before and after cortical ablation. The most prominent and fastest indirect sink (Y-group) was found in ;the lower half of the SGS and uppermost part of the SO. Low-amplitude, long-latency indirect current sinks were also found in the upper and lower thirds of the SGS. 4. The principal conclusions of this report are first, that the SGS is divisible into three physiologic regions according to the spatiotemporal pattern of excitatory synaptic activity generated by the afferent inputs and second, that there is a spatiotemporal matching of the direct collicular afferents from the contralateral retina and the indirect retinal afferents relaying through the ipsilateral visual cortex.
Favored patterns in spike trains. I. Detection
Authors: Dayhoff J. E. , Gerstein G. L.
Published: December 2017

Traditional spike-train analysis methods cannot identify patterns of firing that occur frequently but at arbitrary times. It is appropriate to search for recurring patterns because such patterns could be used for information transfer. In this paper, we present two methods for identifying "favored patterns" --patterns that occur more often than is reasonably expected at random. The quantized Monte Carlo method identifies and establishes significance for favored patterns whose detailed timing may vary but that do not have extra or missing spikes. The template method identifies favored patterns whose occurrences may have extra or missing spikes. This method is useful when employed after the results of the first method are known. Studies with simulated spike trains containing known interpolated patterns are used to establish the sensitivity and accuracy of the quantized Monte Carlo method. Certain trends with regard to parameters of the detected patterns and of the analysis methods are described. Application of these methods to neurophysiological data has shown that a large proportion of spike trains have favored patterns. These findings are described in the accompanying paper (3).
Synaptic interactions between mammalian central neurons in cell culture. III. Morphophysiological correlates of quantal synaptic transmission
Authors: Neale E. A. , Nelson P. G. , Macdonald R. L. , Christian C. N. , Bowers L. M.
Published: December 2017

The statistical properties of excitatory synaptic transmission between neurons in cell cultures of fetal mouse spinal cord were studied and the anatomical extent of these connections demonstrated by horseradish peroxidase (HRP) injection of the presynaptic cell. In conjunction with previous experiments (7), we have correlated the number of boutons involved in a given synaptic connection with the physiologically determined number of release elements. The number of boutons is somewhat greater than the number of release elements, and our results are supportive of the conclusion of others (1, 2) that the physiologically defined release element corresponds to the bouton. We interpret this to suggest that a rate-limiting mechanism may operate at the level of the bouton to allow release of no more than one quantal unit of transmitter with each presynaptic action potential.
Organization of synaptic inputs to paracerebral feeding command interneurons of Pleurobranchaea californica. III. Modifications induced by experience
Authors: Davis W. J. , Gillette R. , Kovac M. P. , Croll R. P. , Matera E. M.
Published: December 2017

Phasic paracerebral feeding command interneurons (PCP's) were studied in whole-animal preparations of Pleurobranchaea drawn from four populations with different behavioral histories: food avoidance conditioned, yoked controls, food satiated, and naive. PCP responses to chemosensory food stimuli (liquefied squid) and mechanosensory touch stimuli (tactile stimulation of anterior and posterior structures) were recorded intracellularly, scored blind, and compared quantitatively across the four populations. PCP's from avoidance-conditioned specimens (10, 18, 19) showed decreased excitatory and increased inhibitory responses to food and touch in comparison with naive (untrained) specimens. Control animals did not show these effects. PCP's from satiated specimens showed decreased excitatory and increased inhibitory responses to food and touch in comparison with PCP's from control, naive, and conditioned specimens. Inhibitory postsynaptic potentials (IPSPs) induced in PCP's of conditioned and satiated specimens by food and touch are indistinguishable in amplitude and waveform from IPSPs produced in the same PCP's by the previously described cyclic inhibitory network (CIN; Ref. 13). In addition, tonic paracerebral neurons (PCT's) that lack input from the CIN, are not inhibited but rather are excited in trained and satiated animals. Therefore the inhibitory responses to food and touch by PCP's of conditioned and satiated specimens appear to be mediated by the CIN. This study demonstrates that associative and nonassociative processes (learning and food satiation, respectively) manifest similarly at the level of command interneurons. The findings furnish a neurophysiological explanation for behavioral motivation in Pleurobranchaea, namely, modulation of the balance of excitation/inhibition in command neurons controlling the corresponding behavior. A cellular model of food avoidance learning and food satiation is formulated to account for these data, based on the identified neural circuitry of the paracerebral command system (15, 17).
Swimming rhythm in decerebrated, paralyzed stingrays: normal and abnormal coupling
Authors: Droge M. H. , Leonard R. B.
Published: December 2017

Rhythmic motoneuronal activity was recorded from decerebrated, paralyzed stingrays and compared with electromyograms recorded from the same animals. Before and after paralysis, a rostral-to-caudal sequence of alternation occurred between dorsal (elevator) and ventral (depressor) efferents. The swimming pattern was thus observed in the absence of phasic afferent input, and this constitutes fictive locomotion. After paralysis, both the intersegmental delay (time between activation at progressively caudal recording sites) and the burst duration remained linearly related to the swim cycle period. In many instances, neither the slope nor the intercept was significantly altered by immobilization. The intercepts all fell near the origin, indicating that the fictive rhythm remains constant phase coupled. Although the swimming rhythm was obtained after paralysis, some differences occurred. These included fewer and shorter spontaneous sequences, a greater range of cycle periods, and longer burst durations. During fictive swimming, the burst duration:cycle period ratio usually increased to 0.53 from 0.39 observed before paralysis. Therefore, the silent periods seen between burst discharges in antagonist efferents during movement were often absent after paralysis. Mechanical stimulation of the tail reduced both cycle periods and burst durations; however, the burst:cycle ratio remained greater than or equal to 0.50. The linear relation between burst duration and cycle period found for spontaneous sequences was not changed by stimulation of the tail. During fictive swimming the inter- and intrasegmental coupling that characterizes stingray swimming becomes labile. Abnormal coupling appears more often during sequences with long swim cycles. Intrasegmental coupling is tighter than intersegmental coupling at any cycle period. Rhythmic activity at one segmental level can be independent of activity at other levels. This suggests that multiple oscillator circuits exist that are not dependent on propriospinal circuits interconnecting different segments. Rhythmicity in elevator and depressor motoneurons is not dependent on reciprocal connections between the circuitry driving the motor nuclei. Therefore, separate oscillators for elevators and depressors appear to be present within one spinal segment.
Inhibition of spinal dorsal horn neuronal responses to noxious skin heating by lateral hypothalamic stimulation in the cat
Authors: Carstens E. , Fraunhoffer M. , Suberg S. N.
Published: December 2017

The responses of single lumbar dorsal horn units to noxious radiant heating (50 degrees C, 10 s) of glabrous foot pad skin were recorded in cats anesthetized with sodium pentobarbital and 70% N2O. The heat-evoked responses of each of 38 units were markedly reduced during electrical stimulation (100-ms trains at 100 Hz, 3/s, 25-300 microA) in the lateral hypothalamic area (LH). LH sites at which stimulation inhibited dorsal horn unit heat-evoked responses were mapped by systematically varying the position of the stimulating electrode. Inhibition was generated at posterior through anterior hypothalamic levels in a region extending laterally from the periventricular gray (PVG) to the cerebral peduncles on both sides and ventrally to the base of the brain. The magnitude of inhibition increased with graded increases in LH stimulation intensity. Respective mean current intensities at threshold for generating inhibition were 27.6 +/- 17.4 (SD) microA for contralateral and 30.1 +/- 23.7 microA for ipsilateral LH stimulation. Dorsal horn unit responses to a series of graded noxious heat stimuli generally increased linearly from threshold (38-45 degrees C) to 52 degrees C. The slopes of such linear temperature-response functions were reduced, with no significant change in threshold, when the temperature series was repeated during concomitant ipsilateral LH stimulation. Contralateral LH stimulation produced similar slope reductions but additionally produced a significant mean threshold increase of 1.7 degrees C. The inhibitory effect of LH stimulation was significantly reduced in nine units from a mean of 28 +/- 18% of control to a mean of 59 +/- 18% following systemic administration of the serotonin (5-hydroxytryptamine, 5-HT) antagonist, methysergide (0.3-1 mg/kg). Possible functional relationships of LH with brain stem inhibitory systems and its role in analgesic mechanisms are discussed.
Interneurons mediating fast postsynaptic inhibition in pyriform cortex of the rabbit
Authors: Satou M. , Mori K. , Tazawa Y. , Takagi S. F.
Published: December 2017

Interneurons mediating the fast IPSPs in principal cells in the pyriform cortex (PC) of the rabbit were searched for using criteria derived from the analysis of the properties of the fast inhibitory postsynaptic potentials (IPSPs). Thirty units were identified as inhibitory interneurons. The interneurons were activated synaptically by volleys from the olfactory bulb (OB), the lateral olfactory tract (LOT), the anterior commissure (AC), and deep-lying structures of the PC (DPC). The interneurons showed a tendency to discharge repetitively in response to shocks applied to these structures of the basal forebrain (OB, LOT, AC, and DPC). The conditioning OB shocks eliminated the testing LOT-evoked discharges of the interneurons. The conditioning OB shocks eliminated the initial part of the testing OB-evoked discharges, leaving the later part relatively unchanged. On the other hand, the conditioning OB shocks did not completely eliminate the testing DPC- or AC-evoked discharges. A temporal facilitation of discharges in the interneurons was observed in response to volleys from the OB, DPC, or AC. A spatial facilitation of discharges in the interneurons was observed in response to a combination of shocks applied to the OB, DPC, and AC. The interneurons were recorded at depths 525-2,755 microns deep to the turnover point of the component 2 wave of field potentials evoked by volleys through the LOT fibers. They were located mostly in the deeper part of layer III of the PC. Intracellular recordings from the presumed inhibitory interneurons showed that OB stimulation elicited two successive excitatory postsynaptic potentials (EPSPs) on which the bursting discharges were superimposed. These EPSPs were followed by a long-lasting hyperpolarizing potential. A comparison of the latencies of the antidromic activation of the principal cells and the synaptic activation of the inhibitory interneurons following OB or DPC stimulation suggested that the inhibitory interneurons are activated at least partly through the axon collaterals of the principal cells, which project their main axons to the OB or DPC. A circuit diagram was proposed for the neuronal pathways responsible for the fast IPSPs of principal cells in the PC.
Location and spike-train characteristics of cells in anterodorsal pons having selective decreases in firing rate during desynchronized sleep
Authors: Hobson J. A. , McCarley R. W. , Nelson J. P.
Published: December 2017

Extracellular microelectrode recordings were made from single neurons in the pontomesencephalic brain stem of head-restrained but nonanesthetized cats whose behavioral state was continuously monitored polygraphically. A population of neurons was encountered with the unusual property of progressively decreasing discharge rate as the cats passed from waking (W) through synchronized sleep (S) to desynchronized sleep (D). In many cases there was a complete cessation of firing in desynchronized sleep, suggesting the designation D-off cell for this neuronal subtype. The D-off cell population was distributed in a bandlike zone across the brain stem at the pontomesencephalic junction with dense concentration of cells in aminergic nuclei: the serotonergic dorsal raphe and raphe linearis centralis and noradrenergic locus ceruleus and peribrachial regions. Aside from a sparse distribution in the central tegmental field, there were no D-off cells in pontine reticular nuclei where cells of the D-on type abound. The proportion of cells showing the D-off property and the magnitude of the state-related change were correlated across nuclear groups as follows: raphe and peribrachial (highest), locus ceruleus (intermediate), and reticular (lowest) for both values. The firing rates of D-off cells tended to be low in waking with very regular interspike intervals. This characteristic firing pattern and the anatomical distribution suggests that D-off cells may be tentatively identified as aminergic. The marked contrasts in aminergic neuronal activity between waking and desynchronized sleep are interpreted as possibly playing a role in state generation through progressive distribution of cholinergic neurons postsynaptic to the D-off cell population. Predictable results would not only be a change in the excitability of the postsynaptic population but also a change in response mode related to a shift in neurotransmitter throughout the brain.
Organization of a fourth somatosensory area of cortex in cat
Authors: Clemo H. R. , Stein B. E.
Published: December 2017

The organization of sensory representations in the cortex of the anterior ectosylvian sulcus (AES) of the cat was investigated using single-unit recording techniques. Somatic, auditory, and visual cells were found in the AES but were partially segregated. Somatic cells were concentrated in the rostral two-thirds of the sulcus, auditory cells were found in the caudal third, and visual cells were distributed along the fundus. A distinct, heretofore unknown, somatotopic representation of the body surface was observed in the AES and was designated SIV. The representation of the body in SIV extends along a rostrocaudal axis and the entire somatotopic map is inverted, with the head rostral and the hindquarters caudal. The representation of the paws extends over the lip of the sulcus to abut the paw representations in SII, and the SIV-SII boundary is marked by a reversal in the sequence of receptive fields along the AEG-AES. The SIV representation (SII) on the crown of the anterior ectosylvian gyrus (AEG). The somatotopic map in SII was found to extend further lateral on the AEG than shown by some investigations and it contains a double representation of the limbs: a large representation with the limbs having the opposite orientation to and abutting the SIV map and a smaller representation located more medial on the AEG and extending into the suprasylvian sulcus. The presence of this double representation may help to explain previous discrepancies regarding the overall orientation of the body in SII.
Dorsolateral pontine inhibition of dorsal horn cell responses to cutaneous stimulation: lack of dependence on catecholaminergic systems in cat
Authors: Hodge C. J. , Apkarian A. V. , Stevens R. T. , Vogelsang G. D. , Brown O. , Franck J. I.
Published: December 2017

The effect of stimulating the dorsolateral pons (DLP) in the region of locus ceruleus (LC) on lumbar dorsal horn cell responses to innocuous and noxious cutaneous stimuli was assessed and the dependence of these effects on intact pontospinal catecholaminergic systems was tested in chloralose-anesthetized cats. DLP stimulation inhibited the responses of dorsal horn cells to both noxious and innocuous skin stimuli. The inhibitory effect was most prominent when the responses to noxious stimuli were tested. The thresholds for eliciting DLP-spinal inhibition were lowest (less than 30 microA) in the region of LC. The inhibitory effect was found in both ipsilateral and contralateral dorsal horns. The DLP-spinal inhibition was unaltered by depletion of spinal catecholamines brought about by repeated lumbar intrathecal administration of 6-hydroxydopamine or systemic administration of reserpine. We conclude that the DLP-dorsal horn inhibition is not related to a catecholaminergic ceruleospinal system in the cat and that the dependence of pain modulation by catecholamine systems is a reflection of other descending pathways.
Response properties of cells in rabbit's lateral geniculate nucleus during reversible blockade of retinal on-center channel
Authors: Knapp A. G. , Mistler L. A.
Published: December 2017

In the vertebrate retina, visual information is segregated into an on channel excited by light increment and a complementary off channel excited by light decrement. We used 2-amino-4-phosphonobutyric acid (APB), which selectively blocks the on channel in the retina (29), to determine the contributions of the on and off pathways to response properties of neurons in the lateral geniculate nucleus (LGN) of anesthetized, paralyzed rabbits. Visually evoked responses were recorded from 46 single cells in the LGN before, during, and after vitreal perfusion with 200-1,000 microM APB. APB reversibly blocked responses of on uniform-field cells and on center concentric-field cells to stationary, flashing spots of light. Responses to off uniform-field cells and off-center concentric-field cells were largely unaffected. APB did not differentially affect responses elicited from the receptive-field centers, as opposed to the surrounds, of on-center concentric-field cells. This finding suggests that these cells are driven exclusively by the on retinal channel and that the center-surround organization of their receptive fields does not result from a convergence of the on and off pathways. We studied a small number of cells that were selective for stimulus direction or motion. In each case, APB eliminated the cell's response to a moving light edge. The surviving response to a moving dark edge retained its original direction or motion preference, suggesting that these response properties do not depend critically on interactions between the on and the off pathways. The findings obtained in the rabbit are reminiscent of the results of similar investigations in the cat (10, 11) and the monkey (25). Taken together, they indicate that in the LGN of several vertebrate species there is a precise segregation vertebrate species there is a precise segregation of on and off information, at least for some functional classes of cells. The combination of on and off information does not seem to play a major role in establishing the response properties observed at this level in the visual system.
Adaptive plasticity in primate spinal stretch reflex: behavior of synergist and antagonist muscles
Authors: Wolpaw J. R. , Seegal R. F. , O'Keefe J. A.
Published: December 2017

Monkeys can gradually change the amplitude of the biceps spinal stretch reflex (SSR) without change in initial muscle length or biceps background electromyographic activity (EMG) (17). We investigated the concurrent behavior of synergist (brachialis and brachioradialis) and antagonist (triceps) muscles. Synergist background EMG remained stable while marked change occurred in biceps SSR amplitude. Triceps background EMG was minimal under all conditions. Thus biceps SSR amplitude change was not due to change in the background activity of closely related muscles. When biceps SSR amplitude changed, synergist SSR amplitude changed similarly but to a lesser extent. Brachialis change averaged 72% of biceps change, while brachioradialis change averaged 33%. By indicating that SSR amplitude change is relatively specific to the agonist muscle, this finding eliminates a number of nonspecific mechanisms as possible origins of SSR amplitude change. Thus it supports the potential value of the SSR as a system for studying the neuronal and synaptic bases of memory in the primate central nervous system (CNS).
Fast ballistic arm movements triggered by visual, auditory, and somesthetic stimuli in the monkey. I. Activity of precentral cortical neurons
Authors: Lamarre Y. , Busby L. , Spidalieri G.
Published: December 2017

Single<unit recordings from motor cortex (area 4) were obtained in two monkeys trained to perform simple flexion and extension movements of the arm in response to somesthetic, visual, and auditory signals. All neurons tested showed movement-related responses that were identical for equivalent movements irrespective of the modality of the triggering stimulus. Progressively longer reaction times were always associated with progressively longer latencies of unit responses. When visual and auditory stimuli were presented simultaneously, the intensity and the duration of both motor and unitary responses remained unchanged as if only one stimulus (auditory) had been given. When the auditory stimulus was appropriately delayed with respect to the visual one, shortening of motor reaction time was observed with a corresponding shortening of the latency of unit responses. In addition to movement-related responses, some neurons showed sensory-related responses mainly to the somesthetic stimulus (37%) and more rarely to the auditory (11%) and visual stimuli (3%). These “sensory” responses preceded and were independent of the movement-related responses; they showed no obvious correlation with the reaction time. Whenever tested, the somatosensory responses persisted after extinction of the motor responses. These findings suggest that, in our experimental conditions, area 4 neurons of the monkey are not involved in the early processing of sensory information required for the initiation of simple, triggered movements. Rather, they appear to generate signals that are mainly related to the characteristics of the motor responses.
Velocity tuning of cells in dorsal lateral geniculate nucleus and retina of the cat
Authors: Frishman L. J. , Schweitzer-Tong D. E. , Goldstein E. B.
Published: December 2017

Velocity tuning curves were measured for on-center cells in the dorsal lateral geniculate nucleus of the cat using a stimulus approximately the height and one-fourth the width of the hand-plotted receptive-field center. The standard stimulus strength was 1 log unit above the mesopic background luminance. Lateral geniculate Y-cells had significantly higher preferred velocities than geniculate X-cells when cells with receptive fields having the same range of retinal eccentricities were compared. Preferred velocity increased for both classes of cells as a function of retinal eccentricity. For all geniculate cells, preferred velocity increased with stimulus strength, showing an approximately threefold increase in preferred velocity for each log unit of stimulus strength. Preferred velocity was measured for on-center retinal ganglion cells with receptive fields at the same range of retinal eccentricities as the geniculate sample and under the same stimulus conditions. Preferred velocities of retinal ganglion Y-cells were significantly higher than those of ganglion X-cells, and as for geniculate cells, preferred velocities increased with increasing stimulus strength. However, the classes were better separated in the geniculate than in the retina; with geniculate X-cells having lower preferred velocities than retinal X-cells, and the geniculate Y-cells having higher preferred velocities than retinal Y-cells. For retinal ganglion cells, smaller receptive-field center sizes of the X-cells than the Y-cells could account in large part for the lower preferred velocities of the X-cells. However, for geniculate cells, differences in receptive-field center size could not account as well for the differences in preferred velocity between X- and Y-cells. Furthermore, field size differences could not account for the differences in preferred velocity between ganglion and geniculate cells of the same functional class. Experiments comparing responses to moving stimuli and flashed stationary stimuli show that stimuli moving at high velocities are in effect equivalent to brief-duration flashes, and responses are governed by the same laws of temporal summation in both cases. When velocity tuning curves were measured with long bars that enhanced peripheral inhibition, geniculate X- and Y-cells were better separated than ganglion X- and Y-cells, not only with respect to preferred velocity but also, with respect to velocity selectivity (width of the velocity tuning curve) and differential velocity sensitivity (slope of the leg of the velocity tuning curves ascending from low velocities to the peak).(ABSTRACT TRUNCATED AT 400 WORDS)