bluuebunny/crossref_metadata_2025 huggingface dataset:
Amplifying role of convergence in olfactory system a comparative study of receptor cell and second-order neuron sensitivities
Authors: Duchamp-Viret P. , Duchamp A. , Vigouroux M.
Published: December 2017

1. Extracellular unitary responses of receptor cells of second-order neurons identified as output cells were recorded in the frog. Four odorants of defined concentrations distributed over a wide range were delivered in the form of 2-s square pulses to the olfactory mucosa with a multistage dynamic flow dilution olfactometer. Bulbar responses were studied under two conditions, the stimuli being delivered either to the ventral or to the entire mucosa. 2. Overall responsiveness of the cells was compared. For the second-order neurons, the response ratio (excitation or inhibition) clearly depended on the condition of stimulation when the entire mucosa was stimulated, the bulbar response ratio was increased, as compared with that obtained when only the ventral mucosa received stimuli. Furthermore, when the stimuli were delivered to the whole mucosa, the bulbar excitation ratio was found to be similar to those of receptor cells and second-order neurons. 3. Response thresholds were determined from a comparison of the interspike interval values in the 30-s pre- and in the 12-s poststimulus time periods, using the Mann-Whitney U test (Table 2). The distribution of response thresholds of receptor cells as a function of stimulus concentration did not significantly differ from that of second-order neurons as excited by stimulating the ventral mucosa. These two distributions differed significantly from the distribution of second-order neurons as stimulated through the entire mucosa. In this last experimental condition, the bulbar neurons displayed an improved sensitivity. 4. The overall recruitment process, represented by the cumulative percentage of cells responding with excitation as a function of concentration, was found to be continuous over the entire concentration range. At the bulbar level, when the entire mucosa was stimulated, the recruitment occurred at lower concentrations than when only the ventral mucosa was stimulated. In this last case, the dynamics of the bulbar recruitment did not differ from that of receptor cells. 5. The recruitment process was further studied for each stimulus, for receptor cells as well as for second-order neurons. Differences in recruitment were found between stimuli and, as for the bulbar neurons, they depended on the condition of stimulation. 6. The main outcome of these results is the demonstration that the convergence of receptor cells onto second-order neurons is functionally implicated in an amplification process of the primary signal in olfaction.(ABSTRACT TRUNCATED AT 400 WORDS)
Horizontal cells isolated from catfish retina contain two types of excitatory amino acid receptors
Authors: O'Dell T. J. , Christensen B. N.
Published: December 2017

1. Inward going membrane currents elicited by N-methyl-D-aspartate (NMDA), glutamate (GLU), and glutamate analogues were recorded from isolated catfish (Ictalurus punctatus) cone horizontal cells using the patch-clamp technique in the whole-cell mode. 2. Currents elicited by the N-methyl-D-aspartate receptor agonists NMDA, L-aspartate (ASP) or L-homocysteate (L-HCA) in nominally Mg-free saline were completely blocked by 100 microM 2-amino-5-phosphonovalerate (AP-5) but responses to non-NMDA receptor agonists kainate (KA), quisqualate (QA), or alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) in normal Mg2+ saline were unaffected. Responses to GLU were partially blocked. Kynurenic acid (1 mM) effectively blocked responses to all agonists. 3. Concentration-response curves obtained from measured responses in the presence of different NMDA receptor agonists gave Hill coefficients of near 1 indicating a single binding site for channel activation. The rank order of agonist affinity at the NMDA receptor is L-HCA greater than NMDA greater than ASP. Glycine potentiates responses to NMDA in horizontal cells. 4. The NMDA-activated channel is blocked in a voltage-dependent manner by Mg2+, Ni2+, and Co2+ and in a voltage-independent manner by Zn2+. Both the NMDA- and KA-activated channel were permeable to monovalent cations but the NMDA-activated channel appeared to have a greater permeability to Ca2+ than the KA-activated channel. 5. Concentration-response curves measured from responses to the non-NMDA receptor agonists QA, KA, and AMPA gave Hill coefficients of approximately 1.5 suggesting multiple binding sites for channel activation and cooperativity. The rank-order affinity was QA greater than AMPA greater than GLU greater than KA. KA was the most efficacious of the agonists resulting in the largest Imax. Rapid desensitization was observed only in the presence of QA, AMPA, or GLU and this desensitization could be removed by pretreatment with conconavalin A (Con A). 6. Single-channel conductance and mean open time were measured from the fluctuations in current noise in the presence of the agonists. The single-channel conductance estimated from the slope of a linear regression obtained from a plot of the variance of the conductance versus the whole-cell conductance measured in NMDA and ASP was 4.7 pS. The mean channel open time was 1.3 ms. These same parameters measured for KA and QA were 5.7 and 5.9 pS and 1.1 to 1.3 ms, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
Mastication in the rabbit: a description of movement and muscle activity
Authors: Schwartz G. , Enomoto S. , Valiquette C. , Lund J. P.
Published: December 2017

1. Mastication was studied in awake rabbits that had previously been prepared for chronic recording of jaw movement and jaw muscle electromyography (EMG) under general anesthesia. Data were stored on tape and replayed for computer-assisted analysis. Most data was taken from the mastication of rabbit chow, but the basic features described in the paper also apply to eating of other foods. The series of movements was divided into cycles, and the phases that compose them, using peaks in the vertical movement, velocity, and acceleration. 2. The whole series of movements from ingestion to swallowing was termed the masticatory sequence. We found, as have others, that the sequence can be divided into three consecutive periods, based on the form of the movements. These were named the preparatory, reduction, and preswallowing series of cycles. 3. The results of earlier studies suggest that the food is transported back to the molar teeth during the preparatory series, ground up during the reduction series, and that the bolus is formed for swallowing during the preswallowing series. 4. The typical cycle of the preparatory series was called type I; it had two phases: opening (O) and fast closing (FC). The jaw-opening muscles were very active during O, but EMG bursts from the closer muscles were small or undefinable during FC. There was not much movement away from the midline in either phase, and the cycles were the shortest in the sequence. 5. The reduction series was predominantly composed of type II cycles. These were of intermediate duration and had three phases [O, a short FC, and a slow closing phase (SC)], during which the pellets were crushed between the molar teeth. The jaw moved toward the working side during FC. At or soon after the start of SC, the closer muscles became very active and continued to contract as the teeth were drawn toward the midline and slightly backwards. 6. The preswallowing series was made up of five-phase cycles that we called type III. These were the longest of the sequence. Jaw opening now occurred in three stages: O1 was the fall from tooth contact to approximately the postural position, O2 was a pause, and O3 was defined as the final movement to maximum opening. The digastric burst occurred during O3. There were again two closing phases, FC and SC, but closer bursts were smaller than in type II, and SC was shorter.(ABSTRACT TRUNCATED AT 400 WORDS)
Lidocaine-induced unilateral internuclear ophthalmoplegia: effects on convergence and conjugate eye movements
Authors: Gamlin P. D. , Gnadt J. W. , Mays L. E.
Published: December 2017

1. To characterize the vergence signal carried by the medial longitudinal fasciculus (MLF), it was subjected to reversible blockade by small injections of 10% lidocaine hydrochloride. The effects of these blockades on both conjugate and vergence eye movements were studied. 2. With this procedure, experimentally induced internuclear ophthalmoplegia (INO) and its effects on conjugate eye movements could be studied acutely, without possible contamination from long-term oculomotor adaptation. In the eye contralateral to the MLF blockade, saccadic and horizontal smooth-pursuit eye movements were normal. Horizontal abducting nystagmus, often seen in patients with INO, was not observed in this eye. 3. As previously reported for INO, profound oculomotor deficits were seen in the eye ipsilateral to the MLF blockade. During maximal blockade, adducting saccades and horizontal smooth-pursuit movements in this eye did not cross the midline. Adducting saccades were reduced in amplitude and peak velocity and showed significantly increased durations. Abducting saccades, which were slightly hypometric, displayed a marked postsaccadic centripetal drift. 4. The eye ipsilateral to the blockade displayed a pronounced, upward, slow drift, whereas the eye contralateral to the blockade showed virtually no drift. Furthermore, although vertical saccades to visual targets remained essentially conjugate, the size of the resetting quick phases in each eye was related to the amplitude of the slow phase movement in that eye. Thus the eye on the affected side displayed large quick phases, whereas the eye on the unaffected side showed only slight movements. On occasion, unilateral downbeating nystagmus was seen. This strongly suggests that the vertical saccade generators for the two eyes can act independently. 5. The effect of MLF blockade on the vergence gain of the eye on the affected side was investigated. As a measure of open-loop vergence gain, the relationship of accommodative convergence to accommodation (AC/A) was measured before, during, and after reversible lidocaine block of the MLF. After taking conjugate deficits into account, the net vergence signal to the eye ipsilateral to the injection was found to increase significantly during the reversible blockade. 6. The most parsimonious explanation for this increased vergence signal is suggested by the accompanying single-unit study. This study showed that abducens internuclear neurons, whose axons course in the MLF, provide medial rectus motoneurons with an appropriate horizontal conjugate eye position signal but an inappropriate vergence signal. Ordinarily, this incorrect vergence signal is overcome by another, more potent, v
Deep neurons in piriform cortex. II. Membrane properties that underlie unusual synaptic responses
Authors: Tseng G. F. , Haberly L. B.
Published: December 2017

1. Membrane properties of deep pyramidal and multipolar cells in layer III of the rat piriform cortex and multipolar cells in the underlying endopiriform nucleus (layer IV) were studied in a slice preparation with the primary goal of elucidating the origin of the unusual synaptic responses described in the companion paper. 2. Micropipettes containing either Lucifer yellow (LY) for combined morphological-physiological analysis or potassium acetate (KAc) were used for the analysis. Comparison of membrane properties of pyramidal cells measured with these two electrolytes revealed significant differences. With LY and other Li+ salts, resting membrane potentials were more depolarized, input resistances higher, spike amplitudes lower, and spike durations longer. 3. As measured with KAc-containing electrodes, membrane properties of deep pyramidal and multipolar cells were similar to each other, but differed from those of superficial pyramidal cells. Resting membrane potentials were more depolarized, thresholds lower, input resistances higher, membrane time constants slower, and spikes smaller and slower. 4. In response to depolarizing current pulses, both deep pyramidal and multipolar cells exhibited an initial depolarizing peak of graded amplitude that fell to a steady state within 150 ms. Current-voltage (I-V) relationships displayed a large increase in slope resistance during the depolarizing peak, but were relatively linear in the depolarizing direction at steady state. In cells with relatively hyperpolarized resting membrane potentials, threshold for the depolarizing peak could be -65 mV or below. Based on a reduction by steady depolarization, reduction by Co2+ and potentiation by Ba2+, it is postulated that the peak is generated in part by a low threshold inactivating Ca2+ current. A partial blockage of this peak by tetrodotoxin (TTX) suggests that a Na+ current also contributes. 5. In response to hyperpolarizing current pulses, especially at depolarized membrane potentials, there was usually a sag from an initial maximum and a depolarizing rebound after current offset in both deep pyramidal and multipolar cells. Based on the dependence on membrane potential (Vm), insensitivity to TTX and blockage by carbamylcholine chloride (carbachol), it is postulated that an M-current contributes to the sag and rebound. 6. The depolarizing rebound that followed offset of hyperpolarizing current pulses could trigger a Ba2+-potentiated local response that resembled the depolarizing peak triggered by depolarizing current, suggesting that the postulated low-threshold inactivating Ca2+ current contributes to its generation.(ABSTRACT TRUNCATED AT 400 WORDS)
Kinematic strategies and sensorimotor transformations in the wiping movements of frogs
Authors: Giszter S. F. , McIntyre J. , Bizzi E.
Published: December 2017

1. Spinal frogs are known to make coordinated and successful wiping movements to almost all places on the body and legs. Such wiping movements involve a sensorimotor transformation. Information from both the spatial locations of stimuli on the skin and the body configuration of the frog is transformed into a set of motor commands that generate body movements adequate to successfully remove the irritant. The spinal cord itself therefore has a limited capacity for sensorimotor transformations. 2. We examined the kinematics of wiping motions in both spinal and intact leopard frogs and bullfrogs. This data was used to assess the flexibility, precision, and strategy of the kinematic sensorimotor transformations used during wiping. The movements involved the use of redundant degrees of freedom in the limbs. Thus many possible movements or solutions could generate successful wiping. This redundancy allows motor-equivalent movements to be used by the frog. 3. Movements were examined in two dimensions by the use of VHS shuttered-video recording and in three dimensions with the use of a WATSMART system of infrared diodes and cameras. The kinematic analysis was applied to those motions in which the limbs did not interact with kinematic constraints, such as the surface of the substrate or body. These unconstrained motions are directly related to motor commands and thus more easily interpreted. 4. Wiping movements to the back were retained in essentially the same form in both spinal and intact frogs. In both cases wiping had four phases with a fifth occasionally present. The phases included flexion, placing, aiming, and whisking, with occasional extension and multiply repeated wipes. However, the aiming phase was often very brief or absent in this data, and flexion was sometimes omitted in multiple wipes. We found that the placing posture was adjusted in a simple way in response to variations in the location of the target stimulus. The rostrocaudal position of the foot tip was strongly and linearly related to the rostrocaudal stimulus location. 5. During the placing posture, joint angles as well as the limb tip in back wipes had linear relationships to the stimulus' rostrocaudal coordinate. The limb configuration used by the frog allowed a strategy of linear (and potentially independent) postural adjustment of joint angle to stimulus position to generate almost linear endpoint adjustments in the placing phase of wiping. This solution to the ill-posed problem of choosing a joint angle for the placing posture in back-wiping may be computationally simple.(ABSTRACT TRUNCATED AT 400 WORDS)
Encoding of nociceptive thermal stimuli by diffuse noxious inhibitory controls in humans
Authors: Willer J. C. , De Broucker T. , Le Bars D.
Published: December 2017

1. It has previously been shown that, in normal humans, heterotopic painful thermal conditioning stimuli induce parallel increase in the thresholds of a spinal nociceptive flexion reflex (RIII reflex) and the concurrent sensation of pain elicited by electrical stimulation of the sural nerve. On the basis of analogous animal studies, we proposed that such phenomena could be related to diffuse noxious inhibitory controls (DNIC), which have been described in the rat. The present study, which was carried out on normal volunteer subjects, was particularly concerned with the extent and temporal characteristics of the depressive effects of DNIC triggered by painful thermal stimuli on RIII reflex activity. In addition, because it was possible that these depressive effects could have resulted from a direct postsynaptic inhibition of motoneurons, a second part of the study was aimed at determining whether or not the heterotopic noxious thermal stimuli also affected the excitability of alpha-motoneurons, as monitored by the monosynaptic Hoffmann reflex (H reflex) technique. 2. In the 11 subjects under study, application of moderate, nonnoxious temperatures (40-44 degree C) to the contralateral hand (via a thermoregulated and agitated waterbath) did not modify the RIII reflex nor the associated sensation of pain. By contrast noxious temperatures clearly depressed the RIII reflex and the concurrent sensation of pain, both during and after the conditioning procedure (CP), in a direct linear relationship to the temperature of the waterbath in the 45-47 degree C range; the maximal depressive effect was observed with the highest conditioning temperature. A significant relationship was also found between the extent of the RIII depression during the CP and that during a 10-min period of post-CP observation. 3. The depressive effects observed on both the RIII reflex and pain were not associated with clear change in autonomic functions. Respiration remained stable during the sessions, with no significant relationship between the temperatures of the waterbath and respiratory rate. Heart rate was slightly but significantly increased during the immersion of the hand in the 46 or 47 degree C waterbaths; this increase, however, ceased with the end of CP. 4. Application of thermal conditioning stimuli produced a slight but nonsignificant increase of the monosynaptic H reflex during the first minute of CP, no matter what was the temperature of the waterbath. However, there were no subsequent variations during the 6-min period of post-CP observation.(ABSTRACT TRUNCATED AT 400 WORDS)
Synchronized discharge of taste neurons recorded simultaneously in rat parabrachial nucleus
Authors: Yamada S. , Ohshima T. , Oda H. , Adachi M. , Satoh T.
Published: December 2017

1. Cross-correlation analysis was made in the taste-sensitive neuron pairs recorded simultaneously from the parabrachial nucleus (PBN) of rats. Three indexes were adopted to evaluate the activities of the taste neurons; namely, 1) spike response density (RD value), which is the net spike density to stimulation with the four basic tastes; 2) the frequency of correlated discharges (FC value in spikes per second), which was determined by measuring the area of the peak appearing in the cross-correlogram (CC) during application of the test fluids; and 3) the weight of correlated discharge (WC = FC/RD), which shows the relative importance of correlated discharges in the taste signals delivered by a component neuron of a given pair. 2. In 11 of 23 pairs, the CCs exhibited peaks during stimulation with tastants. These 11 pairs, which were recorded in the pontine taste area, were composed of 18 NaCl-best (most sensitive to NaCl) and 4 HCl-best neurons. In eight pairs, the best-stimulus of both of the component neurons was NaCl, and it was HCl in one pair (homo-type pairs). The remaining two pairs were composed of an NaCl-best and an HCl-best neuron (hetero-type pairs). 3. In eight homo-type pairs (7 NaCl-best pairs and 1 HCl-best pair), each pair exhibited the maximal FC value during stimulation with the best-stimulus of the component neurons (2.3 less than or equal to maximal FC less than or equal to 26.6 Hz). In the remaining three pairs, the maximal FC values were low (0.8-1.9 Hz).(ABSTRACT TRUNCATED AT 250 WORDS)
Gustatory responses of single neurons in the insula of the macaque monkey
Authors: Yaxley S. , Rolls E. T. , Sienkiewicz Z. J.
Published: December 2017

1. In recordings made from 2,925 single neurons, a region of primary taste cortex was localized to the rostral and dorsal part of the insula of the cynomolgus macaque monkey, Macaca fascicularis. The area is part of the dysgranular field of the insula and is bordered laterally by the frontal opercular taste cortex. 2. The responses of 65 single neurons with gustatory responses were analyzed in awake macaques with the use of the taste stimuli glucose, NaCl, HCl, quinine HCl (QHCl), water, and black currant juice. 3. Intensity-response functions showed that the lowest concentration in the dynamic part of the range conformed well to human thresholds for the basic taste stimuli. 4. A breadth-of-tuning coefficient was calculated for each neuron. This is a metric that can range from 0.0 for a neuron that responds specifically to only one of the four basic taste stimuli to 1.0 for one that responds equally to all four stimuli. The mean coefficient for 65 cells in the taste insula was 0.56. This tuning is sharper than that of neurons in the nucleus of the solitary tract of the monkey, and similar to that of neurons in the primary frontal opercular taste cortex. 5. A cluster analysis showed that at least six different groups of neurons were present. For each of the taste stimuli, glucose, NaCl, HCl, QHCl, water, and black currant juice, there was one group of neurons that responded much more to that tastant than to the other tastants. Other subgroups of these neurons responded to two or more of these tastants, such as glucose and black currant juice, or NaCl and QHCl. 6. On the basis of this and other evidence, it is concluded that the primary insular taste cortex, in common with the primary frontal opercular taste cortex, represents a stage of information processing in the taste system of the primate at which the tuning of neurons has become sharper than that of neurons in the nucleus of the solitary tract, and is moving toward the fineness achieved in the secondary taste cortex in the caudolateral orbitofrontal taste cortex, where motivation-dependence first becomes manifest in the taste system.
Simulation of motion on the skin. III. Mechanisms used by rapidly adapting cutaneous mechanoreceptors in the primate hand for spatiotemporal resolution and two-point discrimination
Authors: Gardner E. P. , Palmer C. I.
Published: December 2017

1. The contribution of rapidly adapting (RA) mechanoreceptors to two-point discrimination has been evaluated by examining their ability to resolve the spacing of grating patterns shifted across the skin. The experiments test two different neural coding mechanisms that have been proposed to underlie resolution of spatial detail on the hand: 1) a rate-intensity code in which the spacing of surface features is encoded by the average frequency of firing of individual sensory afferents, and 2) an isomorphic representation of shape in which variations in the firing patterns of individual afferents reflect the spatiotemporal profile of skin indentation. 2. To measure the spatial acuity of RA mechanoreceptors innervating the hands of macaque monkeys, we displayed pairs of horizontal bars spaced 1-13 mm apart on a computer-controlled OPTACON stimulator placed over glabrous skin. Two-point resolution was measured by simultaneously pulsing pairs of rows at rates of 100, 50 and 25 Hz; each pair was shifted in tandem across the hand to simulate lateral motion. Single-fiber recordings were made from physiologically identified RA afferents in anesthetized monkeys. 3. Receptive field diameter appears to be the critical determinant of spatial resolution of gaps between two bars. RAs fire continuously if bar spacing is less than the field diameter but do not summate inputs when both active rows are contained within the field. Response profiles evoked by two bars spaced less than 4.8 mm apart can be predicted from the single-bar profiles, assuming occlusion between overlapping inputs with the strongest member dominating axonal output. Two-thirds of the RAs tested discharge 1 spike/pulse as bar patterns cross the field, yielding a uniform spike train whose frequency reflects stimulus pulse rates but fails to indicate gaps between bars. An additional 17% fire 2 spikes/pulse when the bars contact or straddle the field center, but also fail to differentiate individual stripes spaced less than 3.6 mm apart. 4. Only 17% of RAs represent gaps narrower than the field diameter. These fibers show double-peaked response profiles to bar patterns spaced at least 2.4 mm apart, firing 2 spikes/pulse as first one, and then the second stripe crosses the field center. Timing between peaks corresponds to bar spacing. Responses are reduced in amplitude when adjacent bars straddle the field center, as occlusion between simultaneous inputs prevents summation of inputs from the two stimuli. Fifteen of 16 RAs failed to resolve bars spaced 1.2 mm apart, as double-spike responses were evoked only by the leading stripe.(ABSTRACT TRUNCATED AT 400 WORDS)
Fourier analysis of saccades in monkeys and humans
Authors: Harris C. M. , Wallman J. , Scudder C. A.
Published: December 2017

1. By recording eye movements with the search coil technique and subjecting them to an accurate infinite Fourier transform algorithm, we describe the Fourier spectra of human and monkey saccades. In both species we find heretofore undescribed features consisting of a regular pattern of local minima in the power plot, which cannot be attributed to noise. The frequency of these minima is well correlated with saccade duration. 2. Computer simulation shows that if the pulse component of the saccade is considered to be rectangular, then the first of these minima (called M1) occurs at a frequency that is the reciprocal of the duration of the pulse. 3. Comparing the position of this component during individual monkey saccades with electrophysiological recordings of motoneurons during the same saccades leads to the conclusion that these minima are related to the burst components in ocular motoneuron discharges. Specifically, the reciprocals of the frequencies of these minima are correlated with the duration of the burst component in the motoneuron discharge. 4. In the Fourier spectra of human saccades, the relationship of the frequency of M1 to saccadic duration is a function similar to that in the monkey. This adds to the evidence that the human saccade also is driven by a pulse-step signal. 5. In both monkeys and humans, T1, the reciprocal of the frequency of M1, is shorter than both the saccade duration and the burst duration of individual motoneurons, even though neurophysiological studies in monkeys generally report the saccadic burst duration to be equal to the saccade duration. This probably arises because the saccadic pulse is not rectangular, with the extremes contributing very little energy to the Fourier spectrum. By further computer modeling we show these shape effects explicitly: as the rise- and falltime increase, making the pulse less rectangular, T1 becomes shorter; in addition, as the asymmetry of rise and fall increases, the depth of the minima is reduced. We conclude that T1 measures the "effective pulse" duration of the motoneuron. 6. There is a difference in the relationship of effective pulse duration to the saccade duration between short and long saccades. For saccades shorter than approximately 40 ms in the human and 50 ms in the monkey, the pulse width as measured by this technique varies little with saccade duration. For longer saccades, effective pulse width increases linearly with duration. We agree with others that for short saccades the pulse is both height- and width-modulated; but for longer saccades, height modulation saturates and only width modulation remains.(ABSTRACT TRUNCATED AT 400 WORDS)
Convergence of heterotopic nociceptive information onto neurons of caudal medullary reticular formation in monkey (Macaca fascicularis)
Authors: Villanueva L. , Cliffer K. D. , Sorkin L. S. , Le Bars D. , Willis W. D.
Published: December 2017

1. Recordings were made in anesthetized monkeys from neurons in the medullary reticular formation (MRF) caudal to the obex. Responses of 19 MRF neurons to mechanical, thermal, and/or electrical stimulation were examined. MRF neurons exhibited convergence of nociceptive cutaneous inputs from widespread areas of the body and face. 2. MRF neurons exhibited low levels of background activity. Background activity increased after periods of intense cutaneous mechanical or thermal stimulation. Nearly all MRF neurons tested failed to respond to heterosensory stimuli (flashes, whistle sounds), and none responded to joint movements. 3. MRF neurons were excited by and encoded the intensity of noxious mechanical stimulation. Responses to stimuli on contralateral limbs were greater than those to stimuli on ipsilateral limbs. Responses were greater to stimuli on the forelimbs than to stimuli on the hindlimbs. 4. MRF neurons responded to noxious thermal stimulation (51 degrees C) of widespread areas of the body. Mean responses from stimulation at different locations were generally parallel to those for noxious mechanical stimulation. Responses increased with intensity of noxious thermal stimulation (45-50 degrees C). 5. MRF neurons responded with one or two peaks of activation to percutaneous electrical stimulation applied to the limbs, the face, or the tail. The differences in latency of responses to stimulating two locations along the tail suggested that activity was elicited by activation of peripheral fibers with a mean conduction velocity in the A delta range. Stimulation of the contralateral hindlimb elicited greater responses, with lower thresholds and shorter latencies, than did stimulation of the ipsilateral hindlimb. 6. Electrophysiological properties of monkey MRF neurons resembled those of neurons in the medullary subnucleus reticularis dorsalis (SRD) in the rat. Neurons in the caudal medullary reticular formation could play a role in processing nociceptive information. Convergence of nociceptive cutaneous input from widespread areas of the body suggests that MRF neurons may contribute to autonomic, affective, attentional, and/or sensory-motor processes related to pain.
The representations of the steady-state vowel sound /e/ in the discharge patterns of cat anteroventral cochlear nucleus neurons
Authors: Blackburn C. C. , Sachs M. B.
Published: December 2017

1. We have recorded the responses of neurons in the anteroventral cochlear nucleus (AVCN) of barbiturate-anesthetized cats to the synthetic, steady-state-vowel sound /e/, presented over a range of stimulus intensities. 2. The responses of (putative) spherical bushy cells [primary-like (Pri) units] to the vowel resemble those of auditory-nerve fibers (ANFs) in terms of both rate and temporal encoding at low and moderate stimulus levels. It was not possible to study the responses of most Pri units at the highest stimulus level because of the large neurophonic component present in recordings from most primarylike units at higher stimulus levels. 3. The responses of many (putative) globular bushy cells [primarylike with notch (PN) units] to the vowel resemble those of ANFs; however, there appears to be greater heterogeneity in the responses of units in the PN population than in the Pri population in terms of both temporal and rate encoding. 4. Populations of stellate cells (chopper units) have degraded representations of the temporal information in ANF population discharge patterns in response to the vowel; this is consistent with the responses of these units to pure tones. Both regular (ChS) and irregular (ChT) chopper subpopulations, however, maintain better rate-place representations of the vowel spectrum than does the population of ANFs as a whole. The rate-place representations of the vowel spectrum by both chopper populations closely resemble those of low and medium spontaneous rate ANFs at most stimulus levels. 5. The data presented in this paper suggest that a functional partition of the AVCN chopper population could yield two distinct rate representations in response to a complex stimulus: one that is graded with stimulus level (over a 30 to 40 dB range) and that, even at rate saturation, maintains a "low contrast" stimulus representation; and a second that maintains a robust, "high contrast" stimulus representation at all levels but that confers less information about stimulus level.
GABAA-receptor-activated current in dorsal root ganglion neurons freshly isolated from adult rats
Authors: White G.
Published: December 2017

1. gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter affecting dorsal root ganglion (DRG) neurons. This study compares properties of current activated by the GABAA receptor in two populations of DRG neurons. DRG neurons were isolated from adult rat with the use of enzymatic and mechanical means. Within hours of being isolated, neurons were recorded from with the use of the whole-cell variant of the patch-clamp technique. 2. One population of neurons exhibited an afterdepolarizing potential (ADP), a low threshold for action-potential generation (-45 to -50 mV), a short-duration action potential (less than 2 ms) that was abolished in the presence of 1-2 microM tetrodotoxin (TTX), and an insensitivity to 50 nM capsaicin. The second population of neurons exhibited a high threshold for action-potential generation (less than -40 mV), a shoulder on the falling phase of the action potential, insensitivity of action-potential generation to TTX (1-2 microM), and a depolarizing response to application of 50 nM capsaicin. 3. Sensitivity to GABA (over the range of 1–1,000 microM) was comparable for the two populations of neurons. 4. GABA-activated current was greater in ADP neurons than in non-ADP-type neurons of a comparable diameter (30-50 microns). The mean +/- SE amplitude of current activated by 10 microM GABA in ADP neurons was 0.310 +/- 0.050 nA (range = 0.110-0.460 nA, n = 8), and 0.037 +/- 0.016 nA (range = 0.010-0.130 pA, n = 7) in non-ADP neurons. Ten microM GABA elicited cell firing in ADP neurons but not in non-ADP neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Properties and distribution of single voltage-gated calcium channels in adult hippocampal neurons
Authors: Fisher R. E. , Gray R. , Johnston D.
Published: December 2017

1. The properties of single voltage-gated calcium channels were investigated in acutely exposed CA3 and CA1 pyramidal neurons and granule cells of area dentata in the adult guinea pig hippocampal formation. 2. Guinea pig hippocampal slices were prepared in a conventional manner, then treated with proteolytic enzymes and gently shaken to expose the somata of the three cell types studied. Standard patch-clamp techniques were used to record current flow through calcium channels in cell-attached membrane patches with isotonic barium as the charge carrier. 3. Single-channel current amplitudes were measured at different membrane potentials. Single-channel current-voltage plots were constructed and single-channel slope conductances were found to fall into three classes. These were (approximately) 8, 14, and 25 pS, and were observed in all three cell types. 4. The three groups of channels differed from each other in voltage dependence of activation: from a holding potential of -80, the small-conductance channel began to activate at about -40 to -30 mV, the medium-conductance channel at about -20 mV, and the large-conductance channel at approximately 0 mV. 5. Ensemble averages of single-channel currents during voltage steps revealed differences in voltage-dependent inactivation. The small-conductance channel inactivated completely within approximately 50 ms during steps from -80 to -10 mV or more positive. Steps to less positive potentials resulted in less inactivation. The medium-conductance channel displayed variable inactivation during steps from -80 to 0 mV. Inactivation of this channel during a 160-ms step ranged from virtually zero to approximately 100%. The large-conductance channel displayed no significant inactivation during steps as long as 400 ms. 6. The large-conductance channel was strikingly affected by the dihydropyridine agonist Bay K8644 (0.5-2.0 microM), resulting in a high probability of channel opening, prolonged openings, and an apparent increase in the number of channels available for activation. The medium and small-conductance channels were not noticeably affected by the drug. 7. The large-conductance channel could be induced to open at very negative membrane potentials by holding the patch for several seconds at 20 or 30 mV and stepping to -30 or -40 mV. This process was enhanced by Bay K8644, resulting in prolonged openings at potentials as negative as -100 mV.(ABSTRACT TRUNCATED AT 400 WORDS)
Excitatory synaptic transmission in cultures of rat olfactory bulb
Authors: Trombley P. Q. , Westbrook G. L.
Published: December 2017

1. Olfactory bulb neurons were dissociated from neonatal rats and plated at low density on a confluent layer of olfactory bulb astrocytes. Intracellular stimulation of presumptive mitral/tufted (M/T) cells evoked monosynaptic excitatory postsynaptic potentials (EPSPs) in adjacent neurons. Whole-cell recording techniques and a flow-pipe drug delivery system were used to compare EPSPs with voltage-clamp recordings of currents evoked by excitatory amino acids (EAA) including N-acetylaspartylglutamate (NAAG), a putative mitral cell transmitter. 2. Cultured olfactory bulb neurons were morphologically and physiologically distinct. Large pyramidal-shaped neurons were present, which were NAAG immunoreactive; stimulation of these neurons invariably evoked EPSPs, suggesting that they were M/T cells. The majority of small bipolar neurons were glutamic acid decarboxylase (GAD) immunoreactive consistent with granule or periglomerular gamma-aminobutyric acid (GABA)ergic interneurons. 3. Monosynaptic EPSPs between M/T cells could be separated into fast and slow components by the use of EAA receptor antagonists. A fast component with a time-to-peak of 7.7 +/- 1.0 (SE) ms and half-width of 31.8 +/- 7.4 ms was blocked by the non-NMDA receptor antagonist 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX, 2.5 microM). The slow component (time-to-peak = 41.4 +/- 7.2 ms; half-width = 218.9 +/- 40.4 ms) was blocked by the N-methyl-D-aspartate (NMDA) receptor antagonist DL-2-amino-5-phosphonovaleric acid (AP5, 100 microM). 4. Under voltage clamp, flow-pipe applications of NAAG (10-1,000 microM) evoked inward currents at a holding potential of -60 mV in Mg-free solutions.(ABSTRACT TRUNCATED AT 250 WORDS)
Purkinje cell simple spike activity during grasping and lifting objects of different textures and weights
Authors: Espinoza E. , Smith A. M.
Published: December 2017

1. Three monkeys (2.5-3.5 kg) were trained to pinch an object between the thumb and forefinger and to lift it a vertical distance of 1.0-2.0 cm. Either the object weight (15, 65, or 115 g) or the surface texture (sand paper or polished metal) contacting the fingers could be varied. The object was equipped with a vertical position transducer, an accelerometer, and strain gauges that measured the grip force and the vertical load force. 2. In accordance with similar previously published studies on human subjects, it was found that monkeys appropriately scaled the grip forces according to the weight and coefficient of friction of the object. The grip force preceded the load force by 25 ms, and they both covaried with the changes in surface friction. 3. An analysis of electromyograms (EMGs) recorded intramuscularly from the muscles of the wrist and fingers including both flexors and extensors indicated that 26 muscles were active during pinching and lifting. Of these, 17 produced the maximum activity for the slippery surface and the greatest weight and the least activity with the roughest surface and lightest weight. 4. A total of 59 Purkinje cells and 123 unidentified units recorded from the paravermal and lateral cerebellar cortex were found to change their firing frequency during lifting the experimental object. 5. Increased discharge during the grasping and lifting was found for 56% (33/59) of the Purkinje cells and 80% (98/123) of the unidentified neurons, whereas 44% (26/59) of the Purkinje cells and 20% of the unidentified neurons decreased activity during the same period. 6. Significant modulations of the firing frequency with surface texture or object weight occurred for 59% (35/59) of the Purkinje cells and 67% (82/123) of the unidentified neurons. 7. One hundred and three Purkinje and unidentified neurons recorded in the paravermal and lateral region of the cerebellar cortex were examined for peripheral receptive fields, and of these, 43/103 (42%) responded exclusively to imposed displacements and tapping of muscles suggesting afferents originating from proprioceptors. A further 28/103 (27%) had exclusively cutaneous receptive fields on the hand that could be stimulated by brushing the skin lightly with a sable hair brush. Only six neurons demonstrated convergent cutaneous and proprioceptive receptive fields and no response to peripheral stimulation could be found for 26 neurons. No difference was found between the receptive fields of Purkinje cells and those of the unidentified neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Electrical stimulation of cervical vagal afferents. I. Central relays for modulation of spinal nociceptive transmission
Authors: Ren K. , Randich A. , Gebhart G. F.
Published: December 2017

1. Supraspinal relays for vagal afferent modulation of responses of spinal dorsal horn neurons to 50 degrees C heating of the skin were examined by the use of nonselective, reversible local anesthesia or soma-selective, irreversible neurotoxic damage of neural tissue. Eighty-five neurons were isolated in the lumbar spinal dorsal horn of 80 pentobarbital-anesthetized, paralyzed rats. All neurons studied had receptive fields on the glabrous skin of the plantar surface of the ipsilateral hind paw and responded to mechanical stimuli of both low and high intensity as well as noxious thermal stimulation. 2. Intensity-dependent modulation by vagal afferent stimulation (VAS) of neuronal responses to heating of the skin was established. Responses of 40 units were facilitated by low and inhibited by greater intensities of VAS. Another 36 units were only inhibited by VAS, and four were only facilitated. 3. Local anesthesia of the dorsolateral pons by bilateral microinjections of lidocaine (4%, 0.5 microliter) were made to examine the contribution of this area to VAS-produced spinal modulation. The microinjection of lidocaine bilaterally into the ventral locus coeruleus/subcoeruleus (LC/SC) reversibly and significantly attenuated VAS-produced inhibition of unit responses to heat from 63 to 89% of control and abolished VAS-produced facilitation. The microinjection of lidocaine bilaterally into the dorsal LC had no significant effect on VAS-produced modulation of spinal dorsal horn neurons. 4. Ibotenic acid (10 micrograms, 0.5 microliter) was microinjected into the dorsolateral pons to determine the relative contributions of cell bodies in this area to VAS-produced spinal modulation. Unilateral microinjection of ibotenic acid into the LC/SC ipsilateral to the vagus nerve stimulated had no significant effect on VAS-produced inhibition but significantly attenuated VAS-produced facilitation of unit responses to heat. Bilateral microinjections of ibotenic acid significantly attenuated VAS-produced inhibition of unit responses to heat from 48 to 94% of control. 5. Local anesthesia of the medial rostroventral medulla (RVM), primarily the nucleus raphe magnus (NRM), significantly attenuated VAS-produced inhibition of unit responses to heat from 55 to 87% of control but had no significant effect on VAS-produced facilitation. Microinjection of ibotenic acid into the RVM also significantly reduced VAS-produced inhibition of unit responses to heat. No significant change in VAS-produced spinal modulation was found after lidocaine microinjection into areas dorsal to the NRM, the nucleus raphe pallidus, or the olivary nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)
Functional topography of cat primary auditory cortex: distribution of integrated excitation
Authors: Schreiner C. E. , Mendelson J. R.
Published: December 2017

1. Neuronal responses to tones and transient stimuli were mapped with microelectrodes in the primary auditory cortex (AI) of barbiturate anesthetized cats. Most of the dorsoventral extent of AI was mapped with multiple-unit recordings in the high-frequency domain (between 5.8 and 26.3 kHz) of all six studied cases. The spatial distributions of 1) sharpness of tuning measured with pure tones and 2) response magnitudes to a broadband transient were determined in each of three intensively studied cases. 2. The sharpness of tuning of integrated cluster responses was defined 10 dB above threshold (Q10 dB, integrated excitatory bandwidth). The spatial reconstructions revealed a frequency-independent maximum located near the center of the dorsoventral extent of AI. The sharpness of tuning gradually decreased toward the dorsal and ventral border of AI in all three cases. 3. The sharpness of tuning 40 dB above response threshold was also analyzed (Q40 dB). The Q40 dB values were less than one-half of the corresponding Q10 dB value. The spatial distribution showed a maximum in the center of AI, similar to the Q10 dB distribution. In two out of three cases, restricted additional maxima were recorded dorsal to the main maximum. Overall, Q10 dB and Q40 dB were only moderately correlated, indicating that the integrated excitatory bandwidth at higher stimulus levels can be influenced by additional mechanisms that are not active at lower levels. 4. The magnitude of excitatory responses to a broadband transient (frequency-step response) was determined. The normalized response magnitude varied between less than 1% and up to 100% relative to a characteristic frequency (CF) tone response. The step-response magnitude showed a systematic spatial distribution. An area dorsal to the Q10 dB maximum consistently showed the largest response magnitude surrounded by areas of lower responsivity. A second spatially more restricted maximum was recorded in the ventral-third of each map. Areas with high-transient responsiveness coincided with areas of broad integrated excitatory bandwidth at comparable stimulus levels. 5. The distribution of excitation produced by narrowband and broadband signals suggest that there exists a clear functional organization in the isofrequency domain of AI that is orthogonal to the main cochleotopic organization of the AI. Systematic spatial variations of the integrated excitatory bandwidth reflect underlying cortical processing capacities that may contribute to a parallel analysis of spectral complexity, e.g., spectral shape and contrast, at any given frequency.(ABSTRACT TRUNCATED AT 400 WORDS)