bluuebunny/crossref_metadata_2025 huggingface dataset:
Repetitive firing properties of neurons in the ventral region of nucleus tractus solitarius. In vitro studies in adult and neonatal rat
Authors: Haddad G. G. , Getting P. A.
Published: December 2017

1. A brain stem slice preparation and intracellular techniques were used to examine the cellular properties of neurons within the ventral and ventrolateral region of the nucleus tractus solitarius (v-NTS) in adult and neonatal (3-12 days old) rats. These neurons are believed to be involved in the control of respiratory function. 2. On the basis of their active and passive electrophysiologic properties, cells in the v-NTS of adult rats were categorized into type A and type B neurons. Type A neurons fired spontaneously with rates ranging from 0.5 to 5 spikes/s at resting potential (-59.0 +/- 6 mV, mean +/- SD). When depolarized, type A cells responded with an initial high rate of firing, which rapidly declined to a steady state level. Spike-frequency adaptation (SFA) index (defined as steady state firing divided by peak activity x 100) was 40%, with a time constant for adaptation of 100-280 ms. When depolarized from membrane potentials more negative than resting, these neurons exhibited a silent period (up to 900 ms) before any spiking was observed (delayed excitation). The delay depended on the duration and magnitude of the hyperpolarizing prepulse that preceded depolarization. The action potentials of type A cells had a shoulder on the repolarization phase, measured 2-3 ms at one-half height, and increased in duration during repetitive firing. 3. At resting potential, type B neurons fired three to five times faster than type A. Although both type A and type B neurons showed spike-frequency adaptation, type B neurons adapted at a much faster rate than type A. The time constant for adaptation was 2-14 ms in type B cells. These cells displayed no delayed excitation on depolarization from membrane potentials more negative than rest. Some type B cells exhibited postinhibitory rebound (PIR) and depolarizing afterpotentials (DAPs). Both types A and B v-NTS neurons had comparable input resistance and showed inward rectification. 4. Neonatal v-NTS cells, in contrast to adult cells, belonged to a single population of neurons. Their resting membrane potential was -58 +/- 6.3 mV (mean +/- SD). The majority of these cells (30/34) were active (5-10 spikes/s) at rest. When depolarized, they showed an immediate increase in firing rate, which gradually slowed down to reach a steady state. Spike-frequency adaptation index was 59%, with a time constant for adaptation of 300-750 ms.(ABSTRACT TRUNCATED AT 400 WORDS)
Dissection of the neuron network in the catfish inner retina. IV. Bidirectional interactions between amacrine and ganglion cells
Authors: Sakai H. M. , Naka K. I.
Published: December 2017

1. We have functionally dissected the neuron network in the catfish inner retina by means of current injection. Simultaneous intracellular recordings were made from two neighboring neurons with the use of two separate electrodes. Extrinsic current was injected into one neuron, and the resulting intracellular responses were recorded from the other neuron. The test signals included 1) a single-frequency sinusoid, 2) a depolarizing or a hyperpolarizing current pulse, and 3) white-noise modulated current from which Wiener kernels were computed by an input-output cross-correlation process. 2. Extrinsic current injected into an ON amacrine (NA) cell evoked responses from a neighboring ON ganglion (GA) cell. Conversely, current injected into a GA cell elicited responses from a neighboring NA cell. Similar results were obtained for the transmission between OFF amacrine (NB) and OFF ganglion (GB) cells. Neural filters for the forward and backward transmissions between amacrine and ganglion cells of the same response polarity were low-pass, constant gain with a cutoff frequency of 40-50 Hz. The gain measured by current-amplitude relationships was comparable for the forward (N----G) and backward (G----N) transmission. 3. Similar bidirectional signal transmission was found between amacrine cells and between ganglion cells of the same response polarity. Neural filters for such transmission were also low-pass, constant gain with a cutoff frequency of 40-50 Hz. 4. Because a large portion of the current-evoked response was predicted by the first-order kernel, transmission between cells of the same response polarity was approximately linear. The current-evoked first-order kernels were brief and impulse-like compared with the light-evoked first-order kernels. 5. We conclude that ON and OFF amacrine and ganglion cells form two ON- and OFF-cell clusters in which cells are extensively and bidirectionally interconnected, enhancing the response in each cluster.
Functional properties of afferent fibers supplying reproductive and other pelvic organs in pelvic nerve of female rat
Authors: Berkley K. J. , Hotta H. , Robbins A. , Sato Y.
Published: December 2017

1. Electrophysiological techniques were used to characterize responses of afferent fibers in pelvic nerve of adult, virgin female rats to mechanical or chemical stimulation of internal reproductive organs and to mechanical stimulation of other pelvic organs. 2. In an in vivo barbiturate-anesthetized preparation, pelvic nerve afferent fibers responded to a wide variety of mechanical stimulation applied to restricted regions of the vaginal canal, caudal uterus (body and cervix), bladder, ureter, colon, or anus. 3. Single-fiber mechanoreceptive fields were invariably confined to a single organ. Notably, responses could be evoked not only by gentle stimulation of the unit's receptive field directly on the organ itself, but also by stimulating the field indirectly with intense stimulation through the appropriate part of a contiguous organ. This innervation feature is consistent with the separability of pelvic organ functions under innocuous conditions but their confusion under noxious ones. 4. Receptive fields on the reproductive organs extended from the caudal edge of the vagina to the uterine body (including the cervix) but were most often located in the fornix (vaginocervical junction). Most units had no or low levels of spontaneous activity. Their responses to mechanical stimuli were usually slowly or moderately adapting and time-locked to the stimulus. 5. Fibers with vaginal receptive fields (including the fornix) responded best either to vaginal distension with a balloon or, more often, to a probe moving along the internal vaginal surface in a direction toward the cervix. They were observed most frequently during the proestrus stage of the rat's estrous cycle. These fibers, therefore, seem particularly suited for relaying information about stimuli that occur during mating. 6. Fibers with receptive fields on the uterine cervix and body responded best to static pressure and were observed less frequently than those with vaginal fields, regardless of estrous stage. They were, however, sensitized by hypoxia. In addition, irritation of the uterus increased the probability of observing them. These fibers, therefore, may exert their primary function during reproductive conditions different from those of virgin rats, such as parturition. 7. Response activity of most of the mechanoreceptive afferent fibers supplying reproductive organs increased as the stimulus intensity increased into the noxious range; i.e., into a range in which the stimulus momentarily produced ischemia at the stimulus site. In addition, in an in vitro preparation, pelvic nerve fibers responded in a dose-dependent manner to injections through the uterine artery of bradykinin (BRAD) as well as to other algesic chemicals, 5-hydroxytryptamine (5-HT) and KCl.(ABSTRACT TRUNCATED AT 400 WORDS)
Different responses of CA1 and CA3 regions to hypoxia in rat hippocampal slice
Authors: Kawasaki K. , Traynelis S. F. , Dingledine R.
Published: December 2017

1. To study the effects of brief periods of hypoxia on cellular functions in the rat hippocampal slice, extracellular and intracellular recordings were made from pyramidal neurons, and interstitial potassium activity ([K+]o) was measured in the pyramidal cell layers. Slices were perfused in an interface chamber at 36-37 degrees C with medium containing 8.5 mM [K+]o. Hypoxia was induced by switching the overflow gas from O2-CO2 to N2-CO2. 2. Brief periods of hypoxia (5-60 s) produced electrographic seizures with typical tonic and clonic components in 53% of 293 slices that generated spontaneous interictal bursts. Hypoxia-induced seizures were usually initiated in and restricted to the Ca1 region; only 2.5% of these slices generated seizures in CA3. In contrast to the CA1 region, the CA3 region could undergo spreading depression during hypoxia. The probability of seizure generation in CA1 was increased with increasing duration of hypoxia and was greatly reduced by lowering the bath temperature a few degrees. 3. [K+]o gradually increased in the CA1 and CA3 cell layers during the 20 s leading up to an hypoxia-induced seizure. [K+]o rose to approximately 9.8 mM (from a base line of 8.5 mM) in CA1 just before a seizure and to 11.4 mM during the seizure. After hypoxia, [K+]o reached a higher level in CA1 than in CA3, regardless of whether 1 microM tetrodotoxin was present to eliminate differences in cell firing in the two regions. CA1 pyramidal cells and glia gradually depolarized by several millivolts during and after hypoxia; no initial hyperpolarizing phase was detected. 4. Burst input from CA3 was necessary for hypoxia-induced seizures. The frequency and intensity of spontaneous burst-firing in CA3 remained steady in the period leading up to a CA1 seizure episode. In contrast, the intensity of synaptically driven bursts in CA1 grew markedly just before seizure onset. N-methyl-D-aspartate (NMDA) receptors participated in the crescendo of increasingly synchronous activity in CA1, because the competitive NMDA receptor antagonist, D-2-amino-5-phosphonovaleric acid (D-APV, 30 microM), stereoselectively reduced seizure intensity. 5. Hypoxia-induced seizures were followed by a depressant phase, which was manifested most prominently by a prolonged (up to several minutes) reduction in the frequency and intensity of burst-firing in the CA3 region, hyperpolarization of CA1 neurons, and undershoot of [K+]o. In normal (3.5 mM) [K+]o, synaptically driven population spikes in CA1 were only reduced in amplitude by hypoxia; hypoxia did not induce seizures in 3.5 mM [K+]o.(ABSTRACT TRUNCATED AT 400 WORDS)
Responses from parabrachial gustatory neurons in behaving rats
Authors: Nishijo H. , Norgren R.
Published: December 2017

1. The responses of a total of 70 single neurons were recorded from the parabrachial nuclei (PBN) in awake rats. In 59 neurons, sapid stimuli (0.5 ml) elicited significant taste responses. Of these 59 neurons, 10 also had significant responses to water. The mean spontaneous rate of the taste neurons was 13.4 +/- 6.9 (SD) spikes/s. Of the remaining 11 neurons, 9 responded significantly only to water; 2 had no significant responses to the standard fluid stimuli. 2. Based on the magnitude of their response to our four standard stimuli, the taste neurons were classified as follows: 42 NaCl-best, 14 sucrose-best, 2 citric acid-best, and 1 QHCl-best. Of these, 25 responded only to one of four sapid stimuli; 20 of these specific cells responded only to NaCl. All the remaining 34 neurons responded to two or more of the four sapid stimuli, with NaCl and sucrose responsiveness dominant. For the 59 taste neurons, the mean entropy for the absolute value of the responses was 0.68; for the excitatory activity alone, it was 0.58. 3. The mean responses to NaCl and sucrose concentration series increased monotonically. Except at the lowest concentration, responses to citric acid also increased monotonically, but with a lower slope. Mean responses to QHCl, however, remained stable or even decreased with increasing concentration. Thus the power functions for the NaCl and sucrose intensity-response series were higher than those of citric acid and QHCl. 4. A hierarchical cluster analysis of 59 parabrachial neurons suggested four different categories: NaCl-best, sucrose-best, citric acid-best, and QHCl-best. These categories were less evident in the two-dimensional space produced by multidimensional analysis, because the positions of NaCl- and sucrose-best neurons formed a continuum in which neural response profiles change successively from sucrose-specific to NaCl-specific. 5. The results were consistent with previous anatomic and neurophysiological data suggesting convergence in the medulla of sensory input from receptors in the nasoincisor ducts (NID) and on the anterior tongue (AT). Taste buds in the NID respond preferentially to sucrose, whereas those on the AT respond more to NaCl.(ABSTRACT TRUNCATED AT 400 WORDS)
Vertical eye movement-related secondary vestibular neurons ascending in medial longitudinal fasciculus in cat. II. Direct connections with extraocular motoneurons
Authors: Iwamoto Y. , Kitama T. , Yoshida K.
Published: December 2017

1. The preceding study in the alert cat has shown that many secondary vestibular axons that ascend in the medial longitudinal fasciculus (MLF) increase their firing rate in proportion to downward eye position. In the present study, projection and termination of these downward-position-vestibular (DPV) neurons within extraocular motoneuron pools were studied electrophysiologically by spike-triggered averaging techniques and morphologically be reconstructing their axonal trajectory after intra-axonal injection of horseradish peroxidase (HRP). 2. Extracellular field potentials recorded within the trochlear nucleus and/or the inferior rectus subdivision of the oculomotor nucleus were averaged by the use of spike potentials of single DPV neurons as triggers. All the crossed-DPV axons tested induced negative unitary field potentials in the trochlear nucleus (n = 9) and in the inferior rectus subdivision of the oculomotor nucleus (n = 5), suggesting that they made monosynaptic excitatory connection with motoneurons in these nuclei. The four crossed-DPV axons tested in the two motoneuron pools induced unitary field potentials in both. The majority of crossed-DPV axons terminated in these nuclei were directly activated from the caudal MLF, indicating that they had descending collaterals projecting to the spinal cord as well. The uncrossed-DPV axons did not induce such unitary field potentials either in the trochlear nucleus (n = 4) or in the inferior rectus subdivision (n = 3). 3. All the uncrossed-DPV axons examined (n = 14) induced positive unitary field potentials in the superior rectus subdivision of the oculomotor nucleus, suggesting that they made monosynaptic inhibitory connections with motoneurons innervating the superior rectus muscle. These uncrossed-DPV axons displayed regular firing patterns and were not activated from the caudal MLF. None of the crossed-DPV axons tested (n = 4) induced unitary field potentials in the superior rectus subdivision. 4. Five crossed-DPV axons were injected with HRP. All these axons ascended in the MLF contralateral to their soma, gave off many collaterals to the trochlear nucleus, and projected more rostrally. For three well-stained axons, numerous terminal branches were also found in the rostroventral part of the contralateral oculomotor nucleus, the area corresponding to the inferior rectus subdivision. Some collaterals in the oculomotor nucleus recrossed the midline to terminate in the medial part of the ipsilateral oculomotor nucleus. Other terminations were observed in the interstitial nucleus of Cajal and in the periaqueductal gray adjacent to the oculomotor nucleus. The crossed axons injected included both regular and irregular types, and three of the four examined were activated from the caudal MLF.(ABSTRACT TRUNCATED AT 400 WORDS)
Discharge properties of single units in auditory part of reticular nucleus of thalamus in cat
Authors: Simm G. M. , de Ribaupierre F. , de Ribaupierre Y. , Rouiller E. M.
Published: December 2017

1. Extracellular recordings from 153 single units were obtained in the auditory part of the reticular nucleus (RE) of the thalamus of anesthetized cats. 2. In absence of acoustic stimulation, the majority of RE units (75%) had a spontaneous activity characterized by bursts of spikes lasting over 30 ms, alternating with isolated discharges; in contrast, only 30% of units in the medial geniculate body (MGB) showed these long bursts during spontaneous activity. 3. For a majority of RE units (65%), activity evoked by noise bursts consisted in complex response patterns with multiple excitatory and/or inhibitory components. For this stimulus, most units (79%) showed nonmonotonic rate-intensity functions, and median response latency to the first excitatory component was 16 ms, which is slightly longer than that obtained in the anterior part of the ventral division of the MGB for the same conditions. 4. Frequency tuning to pure tones in RE was usually broad: the median value of the width of response ranges was five octaves in RE, as compared to two octaves in the ventral division of the MGB and three octaves in the medial division of the MGB. Responses to tones were complex, usually characterized by frequent changes of response pattern with frequency. No preferential arrangement of units as a function of their best frequency was found along a rostrocaudal or a dorsolateral to ventromedial axis. 5. The present study demonstrates that units in the auditory part of RE have discharge properties clearly different from the main auditory thalamic nucleus, the MGB.
Muscle activation patterns and kinetics of human index finger movements
Authors: Darling W. G. , Cole K. J.
Published: December 2017

1. The present study was conducted to determine whether dynamic interaction torques are significant for control of digit movements and to investigate whether such torques are compensated by specific muscle activation patterns. 2. Angular positions of the metacarpophalangeal (MP) and proximal interphalangeal (PIP) joints of the index finger in the flexion/extension plane were recorded with the use of planar electrogoniometers. Muscle activation patterns were monitored with the use of fine wire and surface electromyography of intrinsic and extrinsic finger muscles. 3. Dynamic interaction torques associated with index finger movements were large in relation to joint torques produced by muscles, especially in faster movements. The significance of dynamic interaction torques was demonstrated in model simulations of two-joint finger motion in response to joint torque inputs. Removal of interaction torques from the model inputs produced movements that differed greatly from digit motions produced by human subjects. 4. Electromyogram (EMG) and torque patterns associated with finger movements of different speeds indicated that muscle activity is necessary not only for producing motion at the joints but also to counteract segmental interaction torques. This was especially evident during movements that required voluntary maintenance of a constant MP joint angle during motion of the distal segment about the PIP joint. Under these conditions, muscle moments acting at the MP acted directly to counteract torques at the MP arising from motion at the PIP. 5. Neural mechanisms underlying control of index finger movement are discussed with reference to the implications of dynamic interaction torques. Potential control strategies include accurate programming of muscle activation patterns, appropriate use of motion-dependent peripheral afferent information, and control of the finger as a viscoelastic system through coactivation of flexor and extensor musculature. It is concluded that additional research incorporating study of motion in three dimensions and the use of mechanical models of the finger and related musculature is required to determine how interaction torques are compensated during finger motion.
Insights into associative long-term potentiation from computational models of NMDA receptor-mediated calcium influx and intracellular calcium concentration changes
Authors: Holmes W. R. , Levy W. B.
Published: December 2017

1. Because induction of associative long-term potentiation (LTP) in the dentate gyrus is thought to depend on Ca2+ influx through channels controlled by N-methyl-D-aspartate (NMDA) receptors, quantitative modeling was performed of synaptically mediated Ca2+ influx as a function of synaptic coactivation. The goal was to determine whether Ca2+ influx through NMDA-receptor channels was, by itself, sufficient to explain associative LTP, including control experiments and the temporal requirements of LTP. 2. Ca2+ influx through NMDA-receptor channels was modeled at a synapse on a dendritic spine of a reconstructed hippocampal dentate granule cell when 1-115 synapses on spines at different dendritic locations were activated eight times at frequencies of 10-800 Hz. The resulting change in [Ca2+] in the spine head was estimated from the Ca2+ influx with the use of a model of a dendritic spine that included Ca2+ buffers, pumps, and diffusion. 3. To use a compelling model of synaptic activation, we developed quantitative descriptions of the NMDA and non-NMDA receptor-mediated conductances consistent with available experimental data. The experimental data reported for NMDA and non-NMDA receptor-channel properties and data from other non-LTP experiments that separated the NMDA and non-NMDA receptor-mediated components of synaptic events proved to be limiting for particular synaptic variables. Relative to the non-NMDA glutamate-type receptors, 1) the unbinding of transmitter from NMDA receptors had to be slow, 2) the transition from the bound NMDA receptor-transmitter complex to the open channel state had to be even slower, and 3) the average number of NMDA-receptor channels at a single activated synapse on a single spine head that were open and conducting at a given moment in time had to be very small (usually less than 1). 4. With the use of these quantitative synaptic conductance descriptions. Ca2+ influx through NMDA-receptor channels at a synapse was computed for a variety of conditions. For a constant number of pulses, Ca2+ influx was calculated as a function of input frequency and the number of coactivated synapses. When few synapses were coactivated, Ca2+ influx was small, even for high-frequency activation. However, with larger numbers of coactivated synapses, there was a steep increase in Ca2+ influx with increasing input frequency because of the voltage-dependent nature of the NMDA receptor-mediated conductance. Nevertheless, total Ca2+ influx was never increased more than fourfold by increasing input frequency or the number of coactivated synapses.(ABSTRACT TRUNCATED AT 400 WORDS)
Efferent neurons and suspected interneurons in S-1 forelimb representation of the awake rabbit: receptive fields and axonal properties
Authors: Swadlow H. A.
Published: December 2017

1. Receptive-field properties of antidromically identified efferent neurons within the cutaneous forelimb representation of primary somatosensory cortex (S-1) were examined in fully awake rabbits. Efferent neurons studied included callosal neurons (CC neurons, n = 52), ipsilateral corticocortical neurons (C-IC neurons, n = 48) that project to or beyond the second somatosensory cortical area (S-2), and corticofugal neurons of layer 5 (CF-5 neurons, n = 97) and layer 6 (CF-6 neurons, n = 59) that project to and/or beyond the thalamus. 2. An additional class of neurons was studied that was not activated antidromically from any stimulus site, but which responded synaptically to electrical stimulation of the ventrobasal (VB) thalamus with a burst of three or more spikes at frequencies of 600 to greater than 900 Hz. Most of these neurons also responded synaptically to stimulation of S-2 and the corpus callosum. The action potentials of these neurons were much shorter (mean = 0.45 ms) than those of efferent neurons (mean = 0.95 ms). Such properties have been associated with interneurons found throughout the central nervous system, and these neurons are thereby referred to as suspected interneurons (SINs). 3. CF-5 neurons differed from CC, C-IC, and CF-6 neurons in their spontaneous firing rates, axonal properties, and receptive-field properties. Whereas CF-5 neurons had a mean spontaneous firing rate of 5.5 spikes/s, CC, C-IC, and CF-6 neurons had mean values of less than 1/s. Axonal conduction velocities of CF-5 neurons were much higher (mean = 12.92 m/s) than either CC (mean = 2.15 m/s), C-IC (mean = 1.31 m/s), or CF-6 (mean = 2.53 m/s) neurons. A decrease in antidromic latency (the "supernormal" period) that was dependent on prior impulse activity was seen in the great majority of CC, C-IC, and CF-6 neurons but was either minimal or absent in CF-5 neurons of comparable conduction velocity. A higher proportion of CF-5 neurons (98%) responded to peripheral sensory stimulation than did either CC (75%), C-IC (71%), or CF-6 (51%) neurons. CF-6 and C-IC neurons that did not respond to sensory stimulation had significantly lower axonal conduction velocities and spontaneous firing rates than those that responded to such stimulation. 4. Cutaneous receptive fields were seen in most neurons that could be driven by peripheral stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)
Dynamic analysis of sensory-inhibitory interactions in crayfish stretch receptor neurons
Authors: Barrio L. C. , Buno W.
Published: December 2017

1. The effects of regular and random inhibition at moderate rates on the sensory response evoked by sinusoidal stretches were investigated in slowly and rapidly adapting stretch receptors of crayfish (RM1 and RM2, respectively). 2. Although the RM1 has pacemaker properties and the RM2 is spontaneously silent, inhibitory postsynaptic potential (IPSP) effects were similar in both mechanosensory neurons. The most common consequence was the expected reduction of the sensory response and the increase of the elongation needed to reach firing threshold. With regular IPSPs there were regions where pre- and postsynaptic spikes alternated at fixed integer ratios, usually 1:1, more rarely 1:2 and 1:3. Increases or decreases of the sensory excitation caused sudden postsynaptic accelerations or decelerations when specific length bounds were crossed and where pre- and postsynaptic alternations changed to lower (e.g., from 1:1 to 1:2) or higher ratios (e.g., from 1:2 to 1:1), respectively. 3. Paradoxical effects were also observed because increasing or decreasing the inhibitory rate for a given alternation ratio (e.g., 1:1) accelerated or decelerated the output rate, respectively. Alternations and paradoxical behaviors disappeared with IPSP pattern irregularization. Random IPSPs strongly irregularized the receptor's output. Inhibition, especially if the pattern was irregular, could excite under special conditions. 4. With regular IPSPs, mechanical sensitivity became zero at the lengths at which receptors were silenced, low during alternations, and maximum at transitions between successive alternation ratios. Irregular IPSPs did not have this delinearizing consequence. 5. In conclusion, inhibition introduced important complex modifications in the coding of mechanosensory information. Effects were similar in both receptor types, indicating that self-sustained oscillations are not fundamental. The observed changes were critically dependent on pre- and postsynaptic rate and pattern. They cannot be explained by simple summation of converging sensory and inhibitory inputs and represent another observation of the complex dynamic behavior of periodically driven nonlinear systems.
Afferent and association fiber differences in short-term potentiation in piriform (olfactory) cortex of the rat
Authors: Hasselmo M. E. , Bower J. M.
Published: December 2017

1. The effects of low-frequency stimulus trains on synaptically evoked responses in piriform cortex pyramidal cells were studied by the use of intracellular recording techniques in an in vitro slice preparation. Afferent and association fiber systems were differentially stimulated with electrodes placed in layer 1a or layer 1b, respectively. To quantify synapse modifiability, the heights of postsynaptic potentials (PSPs) elicited by paired-pulse stimulation (100-ms interval) were averaged over a 50-s period before and after a set of 10 stimulus trains (10 pulses each, 20 Hz, 5-s interpulse interval). 2. Afferent and association fibers showed consistent differences in their response to stimulation during the period lasting from approximately 10 to 200 s after presentation of trains. During this time period, the responses to stimulation of association fibers in layer 1b displayed a short-term potentiation, which over the 10 posttrain trials, produced an average increase in PSP height of 23.2 +/- 3.7% (mean +/- SE). On the other hand, responses to layer 1a stimulation showed an average depression of 10.9 +/- 3.6%. Layer 1b potentiation decayed with time constant roughly estimated at 79 s. Layer 1b potentiation appeared even at very low stimulus voltages and after local association fiber input had been cut, suggesting that it was largely a monosynaptic effect. 3. In the period immediately after train presentations, responses evoked by both layers showed a short-term augmentation with a time constant around 3 s. In layer 1a, this augmentation was superimposed on a depression with slow recovery. At longer times after train presentation (greater than 5 min), 2 cells out of 46 showed changes (increases) in synaptic efficacy in response to layer 1b stimulation. 4. In the current experiments both layers 1a and 1b showed statistically significant facilitation before the presentation of stimulus trains. However, layer 1b facilitation decreased from 22.7 +/- 3.5% to a statistically insignificant 3.9 +/- 3.3% after the presentation of trains, whereas layer 1a facilitation remained at a statistically significant level of 23.1 +/- 5.7%. 5. These experiments show that pyramidal cell responses to stimulation of the afferent and association fiber systems are affected differently by the previous presentation of trains of stimuli. This suggests that mechanisms of synaptic modification may differ between the afferent and intrinsic association synaptic projections onto single pyramidal cells in olfactory cortex.(ABSTRACT TRUNCATED AT 400 WORDS)
Spatial and temporal response properties of lagged and nonlagged cells in cat lateral geniculate nucleus
Authors: Saul A. B. , Humphrey A. L.
Published: December 2017

1. It has recently been shown that the X- and Y-cell classes in the A-layers of the cat lateral geniculate nucleus (LGN) are divisible into lagged and nonlagged types. We have characterized the visual response properties of 153 cells in the A-layers to 1) reveal response features that are relevant to the X/Y and lagged/nonlagged classification schemes, and 2) provide a systematic description of the properties of lagged and nonlagged cells as a basis for understanding mechanisms that affect these two groups. Responses to flashing spots and drifting gratings were measured as the contrast and spatial and temporal modulation were varied. 2. X- and Y-cells were readily distinguished by their spatial tuning. Y-cells had much lower preferred spatial frequencies and spatial resolution than X-cells. Within each functional class (X or Y), however, lagged and nonlagged cells were similar in their spatial response properties. Thus the lagged/nonlagged distinction is not one related to the spatial domain. 3. In the temporal domain X- and Y-cells showed little difference in temporal tuning, whereas lagged and nonlagged cells showed distinctive response properties. The temporal tuning functions of lagged cells were slightly shifted toward lower frequencies with optimal temporal frequencies of lagged X-cells averaging an octave lower than those of nonlagged X-cells. Temporal resolution was much lower in lagged X- and Y-cells than in their nonlagged counterparts. 4. The most dramatic differences between lagged and nonlagged cells appeared in the timing of their responses, as measured by the phase of the response relative to the sinusoidal luminance modulation of a spot centered in the receptive field. Response phase varied approximately linearly with temporal frequency. The slope of the phase versus frequency line is a measure of total integration time, which we refer to as visual latency. Lagged cells has much longer latencies than nonlagged cells. 5. The intercept of the phase versus frequency line is a measure of when in the stimulus cycle the cell responds: we refer to this as the intrinsic or absolute phase of the cell. This measure of response timing not only distinguished lagged and nonlagged cells well but also covaried with the sustained or transient nature of cells' responses to flashed stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)
Ionic mechanism of substance P actions on neurons in trigeminal root ganglia
Authors: Spigelman I. , Puil E.
Published: December 2017

1. Responses of primary sensory neurons to substance P applications by perfusion were studied with intracellular recording techniques in in vitro slice preparations of trigeminal root ganglia (guinea pigs). Application of substance P in micromolar doses produced reversible depolarizations of 2–47 mV in 48 out of 64 neurons. The depolarizing influence facilitated repetitive spike discharge evoked by current-pulse injection. Evidence of desensitization was observed during prolonged or repeated applications of the peptide. 2. The responses to substance P were associated with decreased input resistance, although increased input resistance was observed in neurons where the resting membrane potential was compensated with DC injection. In single-electrode voltage-clamp (SEVC) recordings, substance P evoked an inward shift in the holding current and reduced an outwardly rectifying component in the I-V relationships. The reversal potential for the substance P response could not be determined. These results suggested that the perikaryal response to substance P has a complex ionic mechanism involving activation and deactivation of membrane conductances. 3. Substance P-induced depolarizations were greatly attenuated during perfusion with solutions that were deficient in [Na+] or [Mg2+] and were not significantly affected during perfusion with low-[Ca2+]-, CO2(+)-containing solutions. 4. In the voltage-clamp investigations, an inward current contributed to the substance P responses during combined application with the K(+)-channel blockers, 4-aminopyridine (4-AP) and tetraethylammonium (TEA). This current was not abolished by the inclusion of CsCl in the perfusing solution or by internal Cs+ application from the recording electrode, suggesting that an anomalous inward rectifier was not involved in the responses to substance P.(ABSTRACT TRUNCATED AT 250 WORDS)
Spectral response patterns of auditory cortex neurons to harmonic complex tones in alert monkey (Macaca mulatta)
Authors: Schwarz D. W. , Tomlinson R. W.
Published: December 2017

1. The auditory cortex in the superior temporal region of the alert rhesus monkey was explored for neuronal responses to pure and harmonic complex tones and noise. The monkeys had been previously trained to recognize the similarity between harmonic complex tones with and without fundamentals. Because this suggested that they could preceive the pitch of the lacking fundamental similarly to humans, we searched for neuronal responses relevant to this perception. 2. Combination-sensitive neurons that might explain pitch perception were not found in the surveyed cortical regions. Such neurons would exhibit similar responses to stimuli with similar periodicities but differing spectral compositions. The fact that no neuron with responses to a fundamental frequency responded also to a corresponding harmonic complex missing the fundamental indicates that cochlear distortion products at the fundamental may not have been responsible for missing fundamental-pitch perception in these monkeys. 3. Neuronal responses can be expressed as relatively simple filter functions. Neurons with excitatory response areas (tuning curves) displayed various inhibitory sidebands at lower and/or higher frequencies. Thus responses varied along a continuum of combined excitatory and inhibitory filter functions. 4. Five elementary response classes along this continuum are presented to illustrate the range of response patterns. 5. “Filter (F) neurons” had little or no inhibitory sidebands and responded well when any component of a complex tone entered its pure-tone receptive field. Bandwidths increased with intensity. Filter functions of these neurons were thus similar to cochlear nerve-fiber tuning curves. 6. ”High-resolution filter (HRF) neurons” displayed narrow tuning curves with narrowband widths that displayed little growth with intensity. Such cells were able to resolve up to the lowest seven components of harmonic complex tones as distinct responses. They also responded well to wideband stimuli. 7. “Fundamental (F0) neurons” displayed similar tuning bandwidths for pure tones and corresponding fundamentals of harmonic complexes. This response pattern was due to lower harmonic complexes. This response pattern was due to lower inhibitory sidebands. Thus these cells cannot respond to missing fundamentals of harmonic complexes. Only physically present components in the pure-tone receptive field would excite such neurons. 8. Cells with no or very weak responses to pure tones or other narrowband stimuli responded well to harmonic complexes or wideband noise.(ABSTRACT TRUNCATED AT 400 WORDS)
Model of synchronized epileptiform bursts induced by high potassium in CA3 region of rat hippocampal slice. Role of spontaneous EPSPs in initiation
Authors: Traub R. D. , Dingledine R.
Published: December 2017

1. We constructed a computer model of the in vitro CA3 region of the rat hippocampal slice bathed in a high-potassium medium. Our aim was to understand better the mechanisms of initiation of synchronized bursts and the processes that regulate the interburst interval in the experimental system. 2. Our model began with a previously published model of the longitudinal CA3 hippocampal slice. The model contains three interconnected cell populations: 9,000 (excitatory) pyramidal cells; 450 inhibitory cells whose postsynaptic action is somatic and decays quickly, corresponding to chloride-dependent inhibition mediated by gamma-aminobutyric acid (GABA)A channels, and 450 inhibitory cells whose postsynaptic action is dendritic, of delayed onset and long lasting, that corresponds to K-dependent inhibition mediated by GABAB channels. 3. The model was then modified to account for specific features of the high-K experimental system: 1) the pyramidal cells do not generate intrinsic bursts; 2) EIPSP(CI) and EK are both shifted in a depolarizing direction; 3) spontaneous (i.e., not caused by presynaptic firing) excitatory postsynaptic potentials (EPSP)s were included; and 4) a steady current was injected into the pyramidal cells to depolarize them. 4. This model generates synchronized population bursts with interburst intervals of approximately 1.0-1.5 s. Bursts in individual pyramidal cells are preceded by barrages of EPSPs. These results agree with experiment. 5. Our model agrees with the following additional experiments: 1) synchronized bursts are abolished by partial blockade of excitatory synapses; 2) burst frequency is increased by partial blockade of a slow-intrinsic-K conductance; and 3) blockade of chloride-dependent inhibition leads to bursts of longer duration with longer interburst intervals. 6. The basic structural features of this model are similar to, but not identical to, the model of the disinhibited hippocampal slice. Spontaneous EPSPs appear to be critical in the high-K system for initiating, but not for synchronizing, population bursts. The experimental data and simulation results raise interesting questions about the role of spontaneous EPSPs in initiating synchronized discharges in other epileptic systems and on the possible role of spontaneous EPSPs in the normal brain.
Independent influences of rod adaptation on cone-mediated responses to light onset and offset in distal retinal neurons
Authors: Frumkes T. E. , Wu S. M.
Published: December 2017

1. The influence of rod adaptation on cone-mediated intracellular responses of distal retinal neurons was examined in the larval tiger salamander. Rods were selectively stimulated by the use of 450-520 nm adapting stimuli too dim to appreciably influence cones. Cones were primarily stimulated with the use of deep-red stimuli (maximally sensitive to wavelengths greater than 650 nm). The qualitative properties of rod-cone interaction were assessed with the use of several different photic-stimulus paradigms. 2. Confirming results of prior studies, we showed that rod adaptation changed the time course of cone-mediated responses to the onset of square-wave light flashes in horizontal cells (HCs); rod adaptation had no similar influence in other distal retinal neurons. Rod adaptation also enhanced cone-mediated responses to rapid flicker in cones, hyperpolarizing (HPBCs) and depolarizing (DPBCs) bipolar cells, as well as HCs. 3. We also examined the influence of rod-stimulating background fields on cone-mediated responses to slow (approximately 1-Hz) flicker composed of sawteeth with a rapid onset (ramp offset) or with a rapid offset (ramp onset). Such stimulation maintained a constant state of long-term adaptation while providing cones with transient-ON or transient-OFF stimulation. 4. Rod adaptation speeds up the response of HCs to rapid onset and increases response amplitude. Rod adaptation had no reliable influence on response to rapid onset in cones or bipolar cells. 5. Rod adaptation enhanced the amplitude of responses of HCs to rapid offset without altering response time course. 6. Rod adaptation greatly enhanced the amplitude of DPBC responses to rapid offset having no reliable influence on the time course of the response. 7. Rod adaptation caused responses of HPBCs to rapid offset to become much more transient. Rod backgrounds had a similar but smaller and less reliable influence on the response of cones to rapid offset. 8. The foregoing results indicate that rod adaptation exerts a minimum of two separate influences on cone-mediated responses in distal amphibian retina. Changes at light onset must reflect the operation of a mechanism that alters response kinetics of the HC membrane. Changes at light offset reflect the operation of a separate mechanism or set of mechanisms that must act in part presynaptically to the HCs.
Inferotemporal units in selective visual attention and short-term memory
Authors: Fuster J. M.
Published: December 2017

1. This research was designed to further clarify how, in the primate, the neurons of the inferotemporal (IT) cortex support the cognitive functions of visually guided behavior. Specifically, the aim was to determine the role of those neurons in 1) selective attention to behaviorally relevant features of the visual environment and 2) retention of those features in temporary memory. Monkeys were trained in a memory task in which they had to discriminate and retain individual features of compound stimuli, each stimulus consisting of a colored disk with a gray symbol in the middle. A trial began with brief presentation of one such stimulus, the sample for the trial. Depending on the symbol in it, the monkey had to memorize the symbol itself or the background color; after 10-20 s of delay (retention period), two compound stimuli appeared, and the animal had to choose the one with the symbol or with the color of the sample. Thus the test required attention to the symbol, in some trials also to the color, and short-term retention of the distinctive feature for each trial, either a symbol or a color. Single-unit activity was recorded from cortex of the IT convexity, lower and upper banks of the superior temporal sulcus (STS), and from striate cortex (V1). Firing frequency was analyzed during intertrial periods and during the entirety of every trial, except for the (match) choice period. 2. In IT cortex, as in V1, many units responded to the sample stimulus. Some responded indiscriminately to all samples, whereas others responded selectively to one of their features, i.e., to one symbol or to one color. Fifteen percent of the IT units were symbol selective and 21% color selective. These neurons appeared capable of extracting individual features from complex stimuli. Some color cells (color-attentive units) responded significantly more to their preferred color when it was relevant (i.e., had to be retained) than when it was not. 3. The latency of IT-unit response to the sample stimulus was, on the average, relatively short in unselective units (mean 159 ms), longer in symbol units (mean 203 ms), and longest in color-attentive units (mean 270 ms). This order of latencies corresponds to the presumed order of participation of those three types of units in the selective attention to the component features of the sample as required by the task. It suggests intervening steps of serial processing before color information reached color-attentive cells.(ABSTRACT TRUNCATED AT 400 WORDS)
Distribution and response properties of cat SI neurons responsive to changes in tooth temperature
Authors: Iwata K. , Tsuboi Y. , Muramatsu H. , Sumino R.
Published: December 2017

1. The activity of 214 tooth pulp-driven neurons (TPNs) in the primary somatosensory cortex (SI) activated by electrical stimulation of the canine tooth pulp was studied in anesthetized cats. These neurons were tested for their responses to thermal stimulation of the tooth pulp. 2. One hundred fifty-five TPNs were not responsive to changes in tooth temperature (thermally insensitive, TINS-TPNs) and 59 TPNs were responsive (thermally sensitive, TS-TPNs: 38 TS-TPNs were heat sensitive and 21 were cold sensitive). TS-TPNs were also tested for responsiveness to mechanical and thermal stimulation of the skin, mucosa, or periodontal membrane. Each TS-TPN was classified on the basis of cutaneous, mucosal, or periodontal mechanical receptive-field properties as either low-threshold mechanoreceptive (LTM: 57%), wide dynamic range (WDR: 25%), nociceptive specific (NS: 10%) or pulp specific (PS: 8%). 3. TS-TPNs were distributed in an upper bank of the orbital sulcus of SI. The majority were located in laminae III (32%) and IV (60%) of area 3b. 4. Heat-sensitive LTM, WDR, PS TS-TPNs, and cold-sensitive LTM TS-TPNs were characterized by a rapid rise in firing rate during thermal stimulation of the tooth pulp. In contrast, heat-sensitive NS and cold-sensitive NS and PS TS-TPNs responded with a slow rise in firing frequency during thermal stimuli delivered to the tooth pulp. 5. A linear regression analysis was applied to the stimulus-response functions of neuronal discharges of TS-TPNs. Fifty-six percent of heat-sensitive LTM, WDR, and cold-sensitive LTM TS-TPNs showed statistically significant relation (P less than 0.5) between peak firing frequency and stimulus temperature and increasing firing frequency after increases in stimulus temperature, whereas heat-sensitive and cold-sensitive NS and PS TS-TPNs did not show a clear increase in firing frequency during the thermal stimulus. 6. These findings suggest that heat-sensitive LTM and WDR TS-TPNs and cold-sensitive LTM TS-TPNs that showed high regression coefficients in stimulus-response function may be involved in encoding the intensity of noxious thermal stimulation of the tooth pulp.