bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional relations among inferotemporal cortex, amygdala, and lateral hypothalamus in monkey operant feeding behavior
Authors: Fukuda M. , Ono T. , Nakamura K.
Published: December 2017

Neural activity in either the amygdala (AM) or lateral hypothalamus (LHA) was examined while monkeys obtained food as a reward for operant bar pressing. Neurons in the AM were tested before, during, and after reversible cooling of the inferotemporal cortex (ITCx). LHA neurons were tested similarly except that the cooling probe was located in the AM. Cooling probes were chronically implanted bilaterally over the dura of the anterior ITCx in one monkey and in the lateral part of the AM in two monkeys. The activity of 43 AM neurons was analyzed. Before ITCx cooling, each AM neuron was classified into one of four groups based on its response pattern: 6 neurons responded primarily to the sight of food, 11 responded primarily to the sight of nonfood objects, 21 responded to the sight of both food and nonfood (arousal related), and 5 neurons did not respond. ITCx cooling changed the spontaneous firing rate of 15 AM neurons (2 increased, 13 decreased). Responses to the sight of food and/or nonfood of two food-related, four nonfood-related, and seven arousal-related neurons were depressed, and responses of two nonfood-related and three arousal-related neurons were enhanced. Of 17 neurons that were normally food or nonfood specific, 8 became nondiscriminative during ITCx cooling. The activity of 55 LHA neurons was tested. Of these, 22 were food related, 6 responded primarily during ingestion, 22 were arousal related, and 5 did not respond. AM cooling changed the spontaneous firing rates of 21 LHA neurons (12 increased, 9 decreased). Visual responses of nine food-related neurons and two arousal-related neurons were depressed by AM cooling. Ingestion-related responses in the AM (3 of 6 food-related neurons) were not affected by ITCx cooling, but responses of three ingestion-related LHA neurons (3/6) were depressed by AM cooling. The data suggest that dynamic interactions among the ITCx, the AM, and the LHA are important in discriminating between food and nonfood, and, consequently, in the stimulus-reinforcement process, i.e., recognition of reward or no reward. The results are discussed in terms of known anatomical data and behavioral evidence from earlier lesion experiments.
Receptive field properties of neurons in area V3 of macaque monkey extrastriate cortex
Authors: Felleman D. J. , Van Essen D. C.
Published: December 2017

Receptive field properties of 147 neurons histologically verified to be located in area V3 were investigated during semichronic recording from paralyzed anesthetized macaque monkeys. Quantitative analyses were made of neuron selectivities for direction, orientation, speed, binocular disparity, and color. The majority of neurons in V3 (76%) were strongly orientation selective; 40% demonstrated strong direction selectivity. Most cells were tuned for stimulus speed and almost half showed optimum responses at 16 degrees/s. The distribution of optimum speeds ranged primarily from 4 to 32 degrees/s. Several cells in V3 displayed multi-peaked orientation- and/or direction-tuning curves. These cells had two or more narrowly tuned peaks that were not co-axial. In some ways, they resemble higher-order hypercomplex cells of cat area 19 and may subserve a higher level of form or motion analysis than is seen at antecedent visual areas. Roughly half (45%) of the cells were selective for binocular disparity. Approximately half of these were tuned excitatory in that they showed weak responses when tested through either eye alone, but showed strong binocular facilitation centered on the fixation plane. The other disparity-selective cells were tuned inhibitory or asymmetric in their responses in front and behind the fixation plane. Contrary to previous reports, approximately 20% of the neurons in V3 were color selective in terms of showing a severalfold greater response to the best monochromatic wavelength compared with the worst. Color-tuning curves of the subset of color selective cells had, on average, a full bandwidth at half maximum response of 80-100 nm. A comparison of the receptive field properties of neurons in V3 to those in other areas of visual cortex suggests that V3, like MT, is well suited for the analysis of several aspects of stimulus motion. V3 may also be involved in some aspects of form analysis, particularly at low contrast levels. Comparison with area VP, a thin strip of cortex anterior to ventral V2, which was previously considered part of V3, indicates that direction selectivity is much more prevalent in V3 than in VP. Conversely, color-selective cells are the majority in VP but a minority in V3. This suggests that visual information is processed differently in the upper and lower visual fields.
Properties of proprioceptive neurons in the cuneate nucleus of the cat
Authors: Surmeier D. J. , Towe A. L.
Published: December 2017

Fifty-two slowly adapting proprioceptive neurons in the cuneate nucleus of chloralose-anesthetized cats were studied. Recordings were made from 3 mm rostral to the obex to 5 mm caudal. The highest densities of proprioceptive neurons were found above and more than 3 mm caudal to the obex. Analysis of the spike trains produced with the forelimb held fixed revealed three basic periodic patterns. Neurons exhibiting these patterns were partitioned into three groups, referred to as the A, B, and C classes. Class A neurons (42%; 22/52) produced regular spike trains that were qualitatively similar to muscle spindle fibers. Interval distributions for this class were typically unimodal and slightly positively skewed. Adjacent intervals were frequently positively correlated. Spectral analysis suggested that 91% of class A spike trains had one to two periodic components. Class B neurons (21%; 11/52) had additional spikes interposed in their periodic discharge; these "interrupting" spikes did not significantly alter the timing of the dominant periodic discharge. Interval distributions were typically bimodal and adjacent intervals were negatively correlated. Spectral analysis suggested that two or more periodic components were present in their spike trains. Class C neurons (36%; 26/52) had spike trains with a basic rhymicity, but when this specific discharge was interrupted, the subsequent interval was near modal length; thus, they were "reset." Interval distributions were usually multimodal and adjacent intervals were frequently negatively correlated. Spectral analysis suggested that C spike trains usually had four or more periodic components. Estimates of information-carrying capacity of each class using a mean rate code and those of primary muscle spindle fibers suggested that a sizable information loss may occur in synaptic transmission. This potential loss was smaller for A-neurons (40%) than for B- (69%) or C-neurons (64%). Electrical stimulation of cutaneous structures influenced 55% (22/52) of the sample. All were members of the B and C classes. Responses were typically biphasic. The cutaneous receptive fields nearly always included a portion of the forepaw. No relationship was found between movement sensitivity and receptive field topography. Contralateral input was found in half (10/20) the neurons tested.
Intrinsic features contributing to spike train patterning in proprioceptive cuneate neurons
Authors: Surmeier D. J. , Towe A. L.
Published: December 2017

The intrinsic processes contributing to the three discharge patterns of proprioceptive cuneate neurons described by Surmeier and Towe were studied experimentally and with computer simulation. Examination of the alterations in excitability produced by antidromic activation suggested that a prolonged inhibition was a concomitant of discharge in proprioceptive cuneate neurons. Computer simulation was performed to test the possible roles of inhibitory hyperpolarizing processes in governing the observed discharge patterns. These simulations used two constant threshold models. The simplest model linearly integrated synaptic potentials until the spike threshold was reached. After the discharge, synaptic potentials that preceded the spike were ignored (i.e., the model was "reset"). The second model was similar to the first except that following a spike two hyperpolarizing processes were activated and preceding events continued to play a role in membrane potential. Simulation of class A spike trains that possessed positive correlations between nearby intervals was successful only with a resetting model. This suggested that class A neurons have fast, no-memory postspike conductance changes, which effectively shunt synaptic charge. Simulation of class B spike trains was possible with the nonresetting model. At least two periodic inputs, which evoked brief, relatively large EPSPs, were required. In addition, a prominent, fast, spike-dependent hyperpolarization and a small-amplitude, slow hyperpolarization were required. Simulation of class C spike trains was also possible with the nonresetting model. Several periodic inputs were required; one input had to evoke a slow suprathreshold EPSP. In contrast to class B simulations, class C spike train simulation required that a large-amplitude, slow hyperpolarization, as well as a brief hyperpolarization, following spike initiation. The results of class B and C simulations suggested that these two groups differed primarily in the amplitude of a slow, hyperpolarizing, postspike conductance. Some role may also be played by the time course of the driving EPSPs.
Directional pursuit deficits following lesions of the foveal representation within the superior temporal sulcus of the macaque monkey
Authors: Dursteler M. R. , Wurtz R. H. , Newsome W. T.
Published: December 2017

Ibotenic acid lesions of the middle temporal visual area (MT) have previously been shown to impair a monkey's ability to initiate smooth pursuit eye movements to targets moving in the extrafoveal visual field (30). This is a retinotopic deficit: pursuit is impaired in all directions within the affected portion of the contralateral visual field. In the present experiments we analyzed the effects of lesions of the foveal representation of MT on the maintenance of foveal pursuit. Injections of ibotenic acid were directed toward the representation of the fovea within MT but spread into extrafoveal regions of MT and adjacent visual areas within the superior temporal sulcus. Chemical lesions of the foveal representation produced a directional deficit in the maintenance of pursuit: the monkey failed to match eye speed to target speed when pursuing a target that moved toward the side of the brain with the lesion. This deficit was evident regardless of the part of the visual field in which target motion began, and pursuit at higher target speeds was more severely affected. The directional deficit was qualitatively similar to pursuit deficits observed in human patients following large parietal-occipital lesions. Extension of the lesions into extrafoveal regions of the contralateral visual field representation also resulted in retinotopic deficits for pursuit initiation: the monkey was unable to match the speed of its pursuit eye movement to that of a target or to adjust the amplitude of its saccade to compensate for target motion. The errors in pursuit speed and saccade amplitude for initiation of pursuit into the contralateral visual field were linearly related, which supports the hypothesis that both deficits arise from damage to the same underlying visual motion processing mechanism. The selectivity of the retinotopic deficit for motion information was also investigated by reducing retinal motion through the use of a stabilized image. After the lesion, the monkeys continued normal pursuit when a position error was present during stabilization, supporting the view that the deficit was related to loss of motion but not position information.
Topography of the oculomotor area of the cerebellar vermis in macaques as determined by microstimulation
Authors: Noda H. , Fujikado T.
Published: December 2017

1. Oculomotor responses to microstimulation of the cerebellar vermis of macaque monkeys were investigated by using a magnetic search-coil method. 2. The oculomotor responses were conjugate eye movements with an ipsilateral horizontal component. Analyses of amplitude-velocity and amplitude-duration relationships revealed that the peak eye velocities and the durations of the responses were comparable to those of saccadic eye movements. 3. Systematic mapping with microstimulation disclosed that the region in the cerebellar vermis that yielded saccades with weak stimulus currents was confined to lobule VII in five monkeys but included a part of folium VIc in the other four monkeys. This region coincided with the distribution of the saccade-related neural activity observed in the present study and also corresponded to the vermal folia from which we recorded the burst mossy-fiber units and the oculomotor Purkinje cell activity. 4. The oculomotor vermis was defined as that region of the cerebellar vermis that met the following criteria: 1) saccades were evoked with low-intensity microstimulation (with currents less than 10 microA); 2) vigorous saccade-related neural activity was present; and 3) Purkinje cell discharges were modulated with eye movements. The oculomotor vermis was more circumscribed and located more posteriorly than the vermal cortex explored in previous microstimulation experiments on monkeys. 5. Microstimulation of the oculomotor vermis evoked more or less curved saccades in oblique directions. The horizontal and vertical components were not simultaneous in some saccades: the shorter component started later or ended earlier than the other component and their peak velocities were not always synchronous. 6. The amplitude of the saccade depended on stimulus parameters; microstimulation with 10-12 pulses within a period of approximately 20 ms (500-600 Hz) was shown to be optimal. When the pulses were applied to the white matter or to the granular layer, a stimulus current of 10 microA was sufficient to evoke saccades. When the molecular layer was stimulated, evoked saccades were smaller and frequently curved, and an increase in the stimulus current changed either the initial direction or the trajectory of the saccade. 7. When the stimulus current was carefully controlled and maintained near the threshold, the direction of the saccade evoked from the oculomotor vermis was topographically organized.(ABSTRACT TRUNCATED AT 400 WORDS)
The organization and activity patterns of the anterior and posterior heads of the guinea pig digastric muscle
Authors: Lev-Tov A. , Tal M.
Published: December 2017

The structure and activity patterns of the anterior and posterior heads of the guinea pig digastric muscle (DG) were studied in ketamine-anesthetized guinea pigs. Collagen staining of longitudinal and transverse sections of the muscle revealed that the guinea pig DG is comprised of a unicompartmental anterior head (ADG) and a multicompartmental posterior head (PDG). The two heads are separated by a thin tendinous inscription that, unlike the intermediate tendon of the DG in humans, is not attached to the hyoid bone. The motor nuclei of the guinea pig DG were reconstructed using retrograde labeling with horseradish peroxidase. The motoneurons of the ADG were clustered in a longitudinal column within the trigeminal motor nucleus. The motoneurons of the PDG were segregated into two clusters within the facial motor nucleus. The cross-sectional areas of the ADG and PDG motoneuron somata exhibited unimodal frequency distributions and the average soma area was larger for ADG than PDG motoneurons. Histochemical characterization of ADG and PDG revealed that the two muscle heads contained the three main histochemical types of muscle fibers identified in limb muscles. The frequency distribution of fiber types in ADG and PDG were not significantly different. Both muscle heads were predominantly fast with slow oxidative fibers accounting for only 1.1 and 0.3% of the fibers in narrow dorsal regions of ADG and PDG, respectively, and 13.6 and 12.9% in the more ventral regions of ADG and PDG, respectively. Simultaneous recordings of EMGs from the ADG and PDG were carried out during spontaneously occurring rhythmical jaw movements. These recordings revealed a high degree of synchrony between the activities of the two heads, although differences were observed in the onset and duration of the EMG bursts. Activity in the PDG preceded activity in the ADG in most of the rhythmical cycles and persisted longer. The differences in latencies of time-locked EMGs evoked in the ADG and PDG by four-pulse cortical stimulation were much smaller than those observed between the activity bursts of the two heads during rhythmical jaw movements. It is suggested that the early activity in the PDG is accounted for by shorter central conduction times in the pathways onto it and/or by higher recruitability of its motor units. The early activity in PDG may serve to optimize the location of ADG on its length-tension curve prior to and during the active state.
Voluntary control of motor units in human antagonist muscles: coactivation and reciprocal activation
Authors: De Luca C. J. , Mambrito B.
Published: December 2017

1. Myoelectric (ME) activity of several motor units was detected simultaneously from the human flexor pollicis longus and extensor pollicis longus muscles, the only two muscles that control the interphalangeal joint of the thumb. The ME signals were detected while the subjects produced isometric force outputs to track three different paradigms: triangular trajectories, random-force trajectories requiring both flexion and extension contractions, and net zero force resulting from stiffening the joint by voluntarily coactivating both muscles. 2. The ME signals were decomposed into their constituent motor-unit action potential trains. The firing rate behavior of the concurrently active motor units was studied using cross-correlation techniques. 3. During isometric contractions, the firing rates of motor units within a muscle were greatly cross-correlated with essentially zero time shift with respect to each other. This observation confirms our previous report of this behavior, which has been called common drive. Common drive was also found among the motor units of the agonist and antagonist muscles during voluntary coactivation to stiffen the interphalangeal joint. This observation suggests two interesting points: 1) that the common drive mechanism has a component of central origin, and 2) that the central nervous system may control the motoneuron pools of an agonist-antagonist muscle pair as if they were one pool when both are performing the same task. 4. During force reversals, the firing rates of motor units reverse in an orderly manner: earlier recruited motor units decrease their firing rate before later recruited motor units. This orderly reversal of firing rates is consistent with the concept of orderly recruitment and derecruitment. 5. A control scheme is suggested to explain the behavior of the motor units in both muscles during force reversal. It consists of centrally mediated reciprocally organized flexion and extension commands along with a common coactivation command to both muscles. This control scheme allows for coactivation and reciprocal activation of an agonist-antagonist set. 6. The agonist-antagonist pair was observed to generate a net force in two control modalities: proportional activation and reciprocal activation. In proportional activation, the agonist-antagonist set is coactivated during either of two states: when uncertainty exists in the required task or when a compensatory force contraction is perceived to be required.(ABSTRACT TRUNCATED AT 400 WORDS)
Models of synchronized hippocampal bursts in the presence of inhibition. II. Ongoing spontaneous population events
Authors: Traub R. D. , Miles R. , Wong R. K. , Schulman L. S. , Schneiderman J. H.
Published: December 2017

1. We extended our computer model of the CA3 region of the hippocampal slice in order to study spontaneous activity occurring in the presence and absence of synaptic inhibition. This was done by providing a steady inward current to the excitatory neurons, whose value was randomly chosen for each cell. With the parameters used, many of the excitatory cells would, if synaptically isolated, remain quiescent, whereas others would burst periodically with periods as brief as 750 ms. Simulations were run for as long as 10 s of neural activity. 2. In the presence of synaptic inhibition, neural activity became organized into recurring, partially synchronized events: clusters of neurons (6% to 12% of the population) would discharge together, with a period averaging 340 ms, shorter than the burst period of any individual neuron. A consequence of periodic clusters of cellular bursts was the widespread occurrence of periodic synchronized synaptic potentials, as have been observed in hippocampal slices and human temporal neocortical slices. The periods between these synaptic potentials are similar in the model to those observed experimentally. 3. The period could be slowed by either increasing the time constant of the slow inhibitory postsynaptic potential (IPSP), or by making the excitatory synapses more powerful. The period seems to be generated in part as follows. Consider those cells with rapid spontaneous discharge rates. An upper bound for the period corresponds to the interval between 1) such a cell's becoming responsive enough to an excitatory synaptic input to burst, and 2) such a cell's bursting spontaneously (i.e., in response to its own intrinsic inward current). For cells with rapid spontaneous discharge rates, the interval defined in this way is approximately 350 ms. 4. Different cells participated in each cluster. A given cluster was initiated by one cell or by two cells bursting together, and spread via excitatory synapses. Excitatory synaptic paths could be traced from the initiating cell(s), directly or through other participants, to all cells participating in a cluster. Spread of activity was limited by two mechanisms, so that not all cells synaptically excited by a participating cell would themselves participate. First, cells might be refractory from having participated in a recent cluster (since the intercluster period was less than the refractory time from a cellular burst to its responsiveness to a synaptic stimulus). Second, some cells might be synaptically inhibited. Synaptic inhibition in this model did not act rapidly enough to suppress the cluster totally.(ABSTRACT TRUNCATED AT 400 WORDS)
The period of susceptibility of visual cortical binocularity to unilateral proprioceptive deafferentation of extraocular muscles
Authors: Trotter Y. , Fregnac Y. , Buisseret P.
Published: December 2017

1. The electrophysiological effects of section of extraocular muscle proprioceptive afferents have been investigated in kitten area 17. Extraocular proprioceptive afferents were interrupted by cutting the ophthalmic branch of the fifth trigeminal nerve (V1 nerve) unilaterally in 15 normally reared kittens (NR) between 3 and 12 wk postnatal, in 3 NR adult cats, and in 7 dark-reared (DR) kittens at 6 wk postnatal. Bilateral sections of the V1 nerve were performed in two kittens at 6 wk postnatal. NR kittens were maintained in a normal environment after the section. DR kittens were returned to the darkroom until the recording session. Receptive-field properties of area 17 neurons were studied after a postsurgical delay of 4-7 wk in most NR kittens and of 4 days to 5 wk in DR kittens. In one NR kitten and in the operated adult cats, the delay was 1-2.5 yr. This study is based on a total sample of 1,190 visual cortical units. 2. When performed in NR kittens between 4 and 8 wk of age, the unilateral section of extraocular proprioceptive afferents significantly reduced the proportion of binocular cells: 1 mo after the section of the V1 nerve, half of the visual cortical cells were monocularly activated. A similar reduction in the proportion of binocular cells was also observed in DR kittens operated at 6 wk of age and then maintained in the dark for 5-7 wk. In contrast to the unilateral section, the bilateral section of the V1 nerve performed in 6-wk-old NR kittens did not disrupt cortical binocularity. 3. In 10 of the 22 kittens that had undergone unilateral sections, there was a strong asymmetry in the ocular dominance distribution in favor of one eye. This asymmetry was not related to the side of the section and was the same in both hemispheres for a given kitten. 4. The postsurgical delay played an important role in the appearance of the cortical deficit: binocularity loss was not found within the week following the section but was present 1 mo after the section. This functional impairment appeared to be permanent, since it was still observed 2.5 yr after the section. 5. Cortical cells were classified in two ways on the basis of their receptive-field organization: 1) into S- or C-types (38, 73), and 2) into small area slow (SAS), large area slow (LAS), or Fast (F)-types (42, 57).(ABSTRACT TRUNCATED AT 400 WORDS)
Action and localization of acetylcholine in the cat retina
Authors: Schmidt M. , Humphrey M. F. , Wassle H.
Published: December 2017

1. Retinal ganglion cells were recorded extracellularly in the intact eye of anesthetized adult cats. The effects of acetylcholine (ACh), the muscarinic antagonist scopolamine (Sco), the nicotinic antagonist dihydro-beta-erythroidine (DBE), and the acetylcholinesterase inhibitor physostigmine (Phy) on maintained and light-evoked ganglion cell discharge was examined using iontophoresis techniques. 2. A monoclonal antibody directed against the ACh synthesizing enzyme choline acetyltransferase (ChAT) was used to label cholinergic cells in retinal wholemounts. The topographical distribution of these cells was studied. 3. Intracellular filling with the fluorescent dye lucifer yellow (LY) was performed to identify the dendritic morphology of putative cholinergic neurons. 4. ACh increased and Sco decreased neuronal activity of all brisk ganglion cell types under all stimulus conditions tested in this study. The action of ACh was abolished during simultaneous application of Sco. 5. DBE raised the firing rate of ON-center brisk cells and decreased activity of OFF-center brisk cells. Again there was no difference under different stimulus conditions. During DBE application the ACh action on OFF-center cells was completely blocked. The ACh action on ON-center cells was diminished. 6. Phy prolonged and enhanced ACh action on all ganglion cell types. During simultaneous stimulation of the receptive-field center and the surround, Phy caused an activity shift in favor of the center response. 7. Immunocytochemical staining revealed two populations of amacrine cells, one in the inner nuclear layer, and the other in the ganglion cell layer. Their total density increased from 250 cells/mm2 in the periphery to 2,700 cells/mm2 in the central area. Analysis of the distribution pattern indicated a functional independence of the two subpopulations. 8. The dendritic morphology of putative cholinergic amacrine cells in the cat retina resembled that of rabbit and rat "starburst" amacrines, which are known to be cholinergic. 9. The possible function of cholinergic amacrine cells in the cat retina is discussed in view of the present findings and compared with results from other mammalian species.
An evaluation of the two-dimensional Gabor filter model of simple receptive fields in cat striate cortex
Authors: Jones J. P. , Palmer L. A.
Published: December 2017

1. Using the two-dimensional (2D) spatial and spectral response profiles described in the previous two reports, we test Daugman's generalization of Marcelja's hypothesis that simple receptive fields belong to a class of linear spatial filters analogous to those described by Gabor and referred to here as 2D Gabor filters. 2. In the space domain, we found 2D Gabor filters that fit the 2D spatial response profile of each simple cell in the least-squared error sense (with a simplex algorithm), and we show that the residual error is devoid of spatial structure and statistically indistinguishable from random error. 3. Although a rigorous statistical approach was not possible with our spectral data, we also found a Gabor function that fit the 2D spectral response profile of each simple cell and observed that the residual errors are everywhere small and unstructured. 4. As an assay of spatial linearity in two dimensions, on which the applicability of Gabor theory is dependent, we compare the filter parameters estimated from the independent 2D spatial and spectral measurements described above. Estimates of most parameters from the two domains are highly correlated, indicating that assumptions about spatial linearity are valid. 5. Finally, we show that the functional form of the 2D Gabor filter provides a concise mathematical expression, which incorporates the important spatial characteristics of simple receptive fields demonstrated in the previous two reports. Prominent here are 1) Cartesian separable spatial response profiles, 2) spatial receptive fields with staggered subregion placement, 3) Cartesian separable spectral response profiles, 4) spectral response profiles with axes of symmetry not including the origin, and 5) the uniform distribution of spatial phase angles. 6. We conclude that the Gabor function provides a useful and reasonably accurate description of most spatial aspects of simple receptive fields. Thus it seems that an optimal strategy has evolved for sampling images simultaneously in the 2D spatial and spatial frequency domains.
Afferent fibers supplying the uterus in the rat
Authors: Berkley K. J. , Robbins A. , Sato Y.
Published: December 2017

1. In the present three-part study electrophysiological techniques were used to characterize responses of afferent fibers in the rat hypogastric nerve to mechanical or chemical stimulation of the uterus, and anatomical techniques were used to identify the spinal segments through which uterine afferent fibers enter the spinal cord. 2. In an in vivo barbiturate-anesthetized preparation, hypogastric afferent fibers responded in a time-locked manner to mechanical stimulation confined to restricted regions of the uterus and adjacent ligament. Receptive fields were most often located on the uterine body, particularly over the cervix. The few located on the uterine horn were usually near regions irritated during preparative surgery. Effective mechanical stimuli (pressure, stretching, squeezing, probing, rarely contractions) were typically greater than 5 g and simultaneously accompanied by transient ischemia around the probe or contracted area. Distension, unless extreme, was not an effective stimulus. Retrospective analysis of the data indicated that fibers may be more sensitive to uterine stimulation when rats are in vaginal estrus/proestrus than in diestrus/metestrus. 3. In an in vitro preparation, hypogastric afferent fibers responded in a dose-dependent fashion to injections into the uterine artery of the algesic chemicals bradykinin, 5-hydroxytryptamine, and KCl. They also responded to high doses of CO2 (in saline) and NaCN, but rarely to lower doses. Nearly all fibers responded to more than one chemical with response characteristics unique to each chemical (e.g., latency, duration, peak rate). 4. Injections of horseradish peroxidase into the uterine body and small portions of the adjacent horns in rats in vaginal estrus consistently labeled a small number of cells in the L1-S1 dorsal root ganglia, with peaks at L2 and L6. Virtually no cells were labeled in rats whose estrous cycle had been disrupted (by inadvertently keeping them in constant light conditions for several weeks). 5. These results indicate that uterine afferent fibers travel to the central nervous system through both the hypogastric (e.g., L1-L4 ganglia) and pelvic (e.g., L5-S1 ganglia) nerves in the rat, and that hypogastric fibers are capable of conveying fairly precise information about temporal and spatial aspects of uterine mechanical and chemical stimulation. The results also encourage future research into the possibility that the responses of these fibers vary as a function of estrous stage or other aspects of the condition of the uterus (e.g., its irritation).(ABSTRACT TRUNCATED AT 400 WORDS)
The spinal projection of individual identified A-delta- and C-fibers
Authors: Traub R. J. , Mendell L. M.
Published: December 2017

1. Recordings were made from individual sensory neurons with an A-delta peripheral conduction velocity, either intrasomally in the L7 dorsal root ganglion, or extracellularly in Lissauer's Tract or in the dorsal root close to the root entry zone. The spinal projection of these afferents was assessed by their antidromic response to stimulation of the dorsal columns (DC) or Lissauer's Tract (LT) at the L5/L6 border. The adequate stimulus was also ascertained. 2. A-delta-fibers could be divided into two groups: high-threshold mechanoreceptors from either skin or muscle (HTMRs) and low-threshold mechanoreceptors (LTMs), primarily Down Hairs. A third group of cells recorded intrasomally had broad spikes with shoulders on the downstroke characteristic of A-delta-nociceptors and were so classified provisionally, although no adequate stimulus could be identified. HTMRs and broad spike cells projected either in DC or LT, but LTMs projected only in DC, never in LT. About one-quarter of both groups failed to project rostrally as far as L5/L6. 3. Cells with unmyelinated axons recorded intrasomally were found to supply either low-threshold or high-threshold mechanoreceptors. Unlike A-delta-cells, all these cells had broad spikes with shoulders on the downstroke. Proportionally fewer C-fibers than A-delta-fibers projected as far as one segment rostral from their root entry zone. Of those that did, axons supplying low-threshold mechanoreceptors projected only in DC, whereas those innervating high-threshold mechanoreceptors could project either through LT or DC. 4. A-delta-fibers supplying LTMs and HTMRs exhibited a similar reduced conduction velocity was reduced even further in the spinal cord but much more for HTMRs than for LTMs. For C-fibers the conduction velocity decrease was more substantial in the dorsal root for HTMRs than for LTMs. 5. These findings suggest that axons innervating different peripheral receptors exhibit characteristic cellular properties. They confirm that the primary afferent component of Lissauer's Tract is specialized as a “pain pathway” but also indicate that the dorsal columns may play some role in the transmission of nociceptive information.
Single-unit analysis of the human ventral thalamic nuclear group: somatosensory responses
Authors: Lenz F. A. , Dostrovsky J. O. , Tasker R. R. , Yamashiro K. , Kwan H. C. , Murphy J. T.
Published: December 2017

1. We have studied the functional and somatotopic properties of 531 single mechanoreceptive thalamic neurons in humans undergoing stereotactic surgery for the control of movement disorders and pain. The majority of these somatosensory cells had small receptive fields (RFs) and were activated in a reproducible manner by mechanical stimuli applied to the skin or deep tissues. These neurons, which we termed "lemniscal," could be further classified into those responding to stimulation of cutaneous (76% of lemniscal sensory cells) or deep (24%) structures. 2. The incidence of neurons having cutaneous or mucosal RFs in the perioral region, thumb, and fingers (66%) was much higher than that of neurons having RFs elsewhere on the body. Most of the deep cells were activated by movements of and/or mechanical stimuli delivered to muscles or tendons controlling the elbow, wrist, and fingers. 3. Sequences of cells spanning several millimeters in the parasagittal plane often exhibited overlapping RFs. However, RFs changed markedly for cells separated by the same distances in the mediolateral direction. This suggests that the cutaneous somatotopic representation of each region of the body is organized into relatively thin sheets of cells oriented in the parasagittal plane. 4. By comparing neuronal RFs in different parasagittal planes in thalamus of individual patients we have identified a mediolateral representation of body surface following the sequence from: intraoral structures, face, thumb through fifth finger to palm, with forearm and leg laterally. 5. Along many trajectories in the parasagittal plane the sequence of cells with overlapping RFs was interrupted by another sequence of cells with RFs corresponding to a different body region. The RFs of the intervening sequence characteristically represented body regions known to be located more medially in thalamus (see 3 above). These findings could be explained if the lamellae postulated above were laterally convex. 6. Cells responding to deep stimulation (deep cells) could be further classified into those responding to joint movement (63%), deep pressure (15%), or both (22%). Deep cells were found usually at the anterior-dorsal border and sometimes at the posterior border of the region containing cells responding to cutaneous stimuli. Although there was some overlap in the RFs, deep cells representing wrist were found medial to those representing elbow, and both of these were found medial to cells representing leg.(ABSTRACT TRUNCATED AT 400 WORDS)
Multiple potassium conductances and their functions in neurons from cat sensorimotor cortex in vitro
Authors: Schwindt P. C. , Spain W. J. , Foehring R. C. , Stafstrom C. E. , Chubb M. C. , Crill W. E.
Published: December 2017

1. Potassium conductances were studied in large layer V neurons using an in vitro slice preparation of cat sensorimotor cortex. The kinetics and pharmacological sensitivity of K+ currents were studied directly using single microelectrode voltage clamp and indirectly by evoking single or multiple spikes and recording the spike repolarization and subsequent afterhyperpolarizations (AHPs). 2. A fast-decaying afterhyperpolarization (fAHP) and a subsequent medium-duration afterhyperpolarization (mAHP) followed a single spike. The amplitude and duration of the mAHP increased when multiple spikes were evoked at a fast rate (e.g., 100 Hz), and a slower afterhyperpolarization (sAHP) appeared only after sustained repetitive firing. 3. All AHPs were reduced by membrane potential hyperpolarization and raised extracellular K+ concentration, suggesting they were caused by an increased K+ conductance. Only the mAHP and sAHP reversed at the estimated value of potassium equilibrium potential (-100 mV), whereas the mean reversal potential of the fAHP was nearly identical to the mean value of resting potential (-71 mV). 4. Mechanisms underlying spike repolarization, the fAHP, and the mAHP were investigated. Two rapidly activating outward currents, a fast-inactivating current and a slowly inactivating delayed rectifier, were detected by voltage clamp. Both currents were reduced rapidly by tetraethylammonium (TEA). The fast transient current was reduced slowly after divalent cations were substituted for Ca2+ (through a mechanism unrelated to blockade of Ca2+ channels), whereas the delayed rectifier was unaffected. 5. Spike duration was increased and the fAHP was abolished only by blocking agents that reduced the fast outward currents. Effects of extracellular and intracellular TEA were similar. Effects of TEA and Ca2+-free perfusate were additive and resembled the effects of intracellular Cs+. The addition of apamin, d-tubocurare, or Cd2+ was ineffective. We conclude that the two fast outward currents reflect pharmacologically and kinetically separate K+ conductances that are primarily responsible for spike repolarization and the fAHP. 6. Voltage-clamp studies revealed two additional outward currents, which were persistent and Ca2+-mediated. Each current activated and deactivated slowly, but the kinetics of one component were approximately 10 times slower than the other. The decay of these currents gave rise to AHPs resembling the mAHP and the early sAHP. 7. Neither the mAHP nor the sAHP was reduced by TEA. The mAHP was reduced when divalent cations were substituted for Ca2+ or when Cd2+, apamin, or d-tubocurare were added.(ABSTRACT TRUNCATED AT 400 WORDS)
Noradrenergic enhancement of long-term potentiation at mossy fiber synapses in the hippocampus
Authors: Hopkins W. F. , Johnston D.
Published: December 2017

1. We tested several hypotheses related to the modulation of long-term potentiation (LTP) by norepinephrine (NE) at the mossy fiber synapses in the rat hippocampal slice preparation using extracellular and intracellular recording techniques. 2. NE exerted frequency-dependent effects on mossy fiber synaptic transmission. It had little effect on extracellular population excitatory postsynaptic potentials (pEPSPs) sampled during low-frequency stimulation, whereas it had marked effects on the duration, magnitude, and probability of induction of LTP at these synapses. 3. The beta-adrenoceptor agonist isoproterenol mimicked all of the effects of NE, whereas the beta-adrenoceptor antagonists propranolol and timolol reversibly blocked the induction of LTP, suggesting the effects of NE are mediated by a beta-adrenoceptor and that beta-adrenoceptor activation may be an important constituent for the expression of LTP at these synapses. 4. Frequency-dependent effects of NE and isoproterenol on mossy fiber pEPSPs were also observed in the presence of the gamma-aminobutyric acid (GABA) antagonist, picrotoxin, suggesting that NE can enhance LTP by a mechanism that does not depend on intact inhibition. However, propranolol did not block LTP in these disinhibited slices and did not affect LTP magnitude. 5. The adenylate cyclase activator forskolin augmented pEPSPs sampled during low-frequency stimulation in disinhibited slices and significantly enhanced LTP. Forskolin, however, did not produce LTP in the absence of tetanic stimulation. This supports the hypothesis that NE and isoproterenol augment features of LTP by stimulating adenosine 3',5'-cyclic monophosphate (cAMP) production and that cAMP plays a modulatory role in the induction of LTP. 6. The postsynaptic injection of the cAMP analogue 8-bromoadenosine 3',5'-cyclic monophosphate (8-bromo-cAMP) significantly increased the probability of induction of LTP measured intracellularly under voltage-clamp conditions with intact inhibition. An analysis of the inhibitory synaptic slope conductance during these experiments indicated that changes in this measure could neither account for the increase in mossy fiber synaptic slope conductance in those cells that displayed it nor account for the group differences in this variable. 7. The amplitude and duration of the postsynaptic depolarization during tetanic stimulation in the cells that displayed LTP in the 8-bromo-cAMP-injected group were significantly greater than in the cells that did not display LTP in the adenosine 5'-monophosphate-injected group.(ABSTRACT TRUNCATED AT 400 WORDS)
Activation of N-methyl-D-aspartate receptors parallels changes in cellular and synaptic properties of dentate gyrus granule cells after kindling
Authors: Mody I. , Stanton P. K. , Heinemann U.
Published: December 2017

1. The cellular and synaptic properties of rat dentate gyrus granule cells (GCs) were examined using intra-/extracellular and Ca2+-sensitive microelectrode recordings following epilepsy induced by kindling of the hippocampal commissures or amygdala. 2. The recordings were made in hippocampal slices prepared from sham-stimulated controls and animals that have received daily stimuli to reach stage IV-V of kindling. The average number of stimulation trials (60 Hz/1 s, 100-150 microA) required to reach full motor seizures (stage V) was 23 +/- 2 for commissural kindling and 14 +/- 1 for amygdala kindling. 3. The resting membrane potential of GCs following kindling (RMP; -72 +/- 3 mV) was not significantly different from the RMP of control GCs (-70 +/- 2 mV). Similarly, action potential height and threshold were unaffected by kindling. However, kindling altered other cellular properties of GCs regardless of the site of stimulation (hippocampal commissures or amygdala), the stage of kindling reached (IV or V), or the time elapsed between the last kindling stimulus and preparation of the hippocampal slices (24 h-6 wk). The input resistance of kindled GCs (55 +/- 4 M omega) was significantly higher than that of controls (40 +/- 3 M omega). In contrast to most control GCs, the slope conductance (GS) of kindled neurons, measured with constant-amplitude current injections at various membrane potentials, generally increased at membrane potentials more negative than rest. Furthermore, other voltage-dependent ionic conductances (see below), that were not normally encountered in control GCs, were present in kindled neurons. 4. The intracellularly recorded monosynaptic excitatory postsynaptic potentials (EPSPs) of kindled GCs, evoked through the stimulation of the lateral perforant pathway, differed significantly from the EPSPs of control GCs. The amplitudes of control EPSPs increased upon hyperpolarizations and decreased following depolarizations of the membrane, as expected for conventional EPSPs without contribution from voltage-dependent conductances. In contrast, the EPSPs of kindled GCs invariably increased in amplitude and duration at membrane potentials 5-20 mV depolarized from rest, indicating the presence of a characteristic voltage-dependent component. Frequently, following the synaptically triggered action potentials, kindled GCs displayed depolarizing afterpotentials. 5. Perfusion of the N-methyl-D-aspartate (NMDA) receptor antagonist DL-2-amino-5-phosphonovaleric acid (APV; 30 microM) had no effect on the EPSPs of control GCs, but consistently reduced the amplitude and duration of EPSPs in kindled GCs.(ABSTRACT TRUNCATED AT 400 WORDS)