bluuebunny/crossref_metadata_2025 huggingface dataset:
Responses of monkey medullary dorsal horn neurons during the detection of noxious heat stimuli
Authors: Maixner W. , Dubner R. , Kenshalo D. R. , Bushnell M. C. , Oliveras J. L.
Published: December 2017

1. We examined the activity of thermally sensitive trigeminothalamic neurons and nonprojection neurons in the medullary dorsal horn (trigeminal nucleus caudalis) in three monkeys performing thermal and visual detection tasks. 2. An examination of neuronal stimulus-response functions, obtained during thermal-detection tasks in which noxious heat stimuli were applied to the face, indicated that wide-dynamic-range neurons (WDR, responsive to innocuous mechanical stimuli with greater responses to noxious mechanical stimuli) could be subclassified based on the slope values of linear regression lines. WDR1 neurons exhibited significantly greater sensitivity to noxious heat stimulation than WDR2 neurons or nociceptive-specific neurons (NS, responsive only to noxious stimuli). 3. In one behavioral task, the monkeys detected 1.0 degrees C increases in noxious heat from preceding noxious heat stimuli ranging from 44 to 48 degrees C. WDR1, WDR2, and NS neurons increased their discharge frequency as a function of the intensity of the first noxious heat temperature (T1) as well as the final temperature (T2). The responses of WDR1 neurons were greater than those produced by WDR2 or NS neurons across all the temperatures examined. The order of stimulus presentation affected the responses of WDR1 neurons to 1.0 degrees C increases in the noxious heat range but not those of WDR2 or NS neurons. 4. In a second behavioral task, the monkeys detected small increases in noxious heat (0.2-0.8 degrees C) from a first temperature of 46 degrees C. Although the responses of all three classes of neurons were monotonically related to stimulus intensity, WDR1 neurons exhibited greater sensitivity to small temperature increases than either WDR2 or NS neurons. 5. Subpopulations of all three classes of neurons exhibited responses that were independent of thermal stimulus parameters or sensory modality and that only occurred during the behavioral task. These task-related responses were time-locked to specific behavioral events associated with trial initiation and trial continuation. 6. These data provide evidence that a subpopulation of WDR neurons is the dorsal horn cell type most sensitive to small increases in noxious heat in the 45-49 degrees C temperature range and provides the most information about stimulus intensity. The findings support the view that nociceptive neurons have the capacity to precisely encode stimulus features in the noxious range and that WDR neurons are likely to participate in the monkeys' ability to perceive the intensity of such stimuli.
The correlation of monkey medullary dorsal horn neuronal activity and the perceived intensity of noxious heat stimuli
Authors: Dubner R. , Kenshalo D. R. , Maixner W. , Bushnell M. C. , Oliveras J. L.
Published: December 2017

1. We examined the relationship between the activity of medullary dorsal horn nociceptive neurons and the monkeys' ability to detect noxious heat stimuli. In two different detection tasks, the temperature of a contact thermode positioned on the monkey's face increased from 38 degrees C to temperatures between 44 and 48 degrees C (T1). After a variable time period, the thermode temperature increased an additional 0.2-1.5 degrees C (T2), and the monkeys' detection speed from the onset of T2 was determined. We previously have established that detection speed is a measure of the perceived intensity of noxious thermal stimuli. Nociceptive neurons were classified as wide-dynamic-range (WDR, responsive to innocuous mechanical stimuli with greater responses to noxious mechanical stimuli) and nociceptive-specific (NS, responsive only to noxious stimuli). WDR neurons were subclassified as WDR1 and WDR2 based on the higher slope values of the stimulus-response functions of WDR1 neurons. The monkeys were trained to detect small increases in noxious heat, and their detection speeds were correlated with the responses of WDR1, WDR2, and NS neurons. 2. Detection speeds to T2 temperatures of 1.0 degrees C from preceding T1 temperatures of 45 and 46 degrees C were faster during a preceding ascending series of stimuli than during a descending series. Similarly, the peak discharge frequencies of WDR1 neurons in response to the same stimuli were greater during the ascending series of T2 temperatures. In contrast, the responses of WDR2 and NS neurons showed no significant differences during the ascending and descending series of stimuli. 3. Detection speeds following 0.4, 0.6, and 0.8 degrees C T2 stimuli were higher when the preceding T1 temperature was 46 degrees C as compared with detection speeds to the identical stimuli when the preceding T1 temperature was 45 degrees C. WDR1 neurons also exhibited a significant increase in peak discharge frequency to these same T2 stimuli when the preceding T1 temperature was 46 degrees C. In contrast, the neuronal activity of WDR2 and NS neurons did not differ on 45 and 46 degrees C T1 trials. 4. The relationship between detection speed and neuronal peak discharge frequency was examined in response to different pairs of T1 and T2 stimuli when T1 was either 45 or 46 degrees C. There was a significant correlation between detection speed and neuronal discharge for WDR1 and WDR2 neurons. No correlation was observed for NS neurons. 5. The magnitude of neuronal activity on correctly detected and nondetected trials was compared when T1 was 46 degrees C and T2 was 0.2 degree C.(ABSTRACT TRUNCATED AT 400 WORDS)
Analysis of vertebrate eye movements following intravitreal drug injections. III. Spontaneous nystagmus is modulated by the GABAa receptor
Authors: Ariel M.
Published: December 2017

1. Turtle eye movements were recorded in response to horizontal motion of patterned stimuli and intravitreal injections of selective GABAergic drugs by using a contact lens search-coil technique. Similar to results from rabbit and cat, injection of picrotoxin into the turtle's eye results in a spontaneous horizontal nystagmus, with its slow-phase movement in a temporal-to-nasal direction with respect to the injected eye. In contrast, there were no prominent vertical eye movements in response to either horizontal optokinetic stimuli or drug injections. 2. Injections of bicuculline or bicuculline methyl iodide (BMI), which selectively block the GABAa receptor, had effects similar to those of picrotoxin. The GABAa agonist muscimol, on the other hand, blocked optokinetic nystagmus (OKN). Furthermore, combinations of these drugs demonstrated competitive interactions between the agonists and antagonists. 3. The threshold dose for the eye-movement effects of each drug was ascertained with the use of a radioactive calibration procedure. Tritiated inulin was injected into the vitreous. After 1 h, ocular components were assayed for radioactivity. Then, by the use of an estimate of vitreal/retinal dilution, the retinal concentrations of these threshold doses were calculated. The computed threshold retinal concentrations of the GABAa drugs were found to be in the low micromolar range. 4. These results are discussed in terms of the directionally sensitive (DS) processing which occurs in the retina, and the output of retinal DS cells to pathways involved in oculomotor control of retinal image stabilization. It is known that intravitreal application of picrotoxin makes DS retinal ganglion cells lose their selectivity for any one direction. Based on the effect of picrotoxin on OKN, it is argued that DS retinal cells provide a major input to oculomotor subsystems involved in the stabilization of gaze. Furthermore, these intravitreal drug effects on OKN are selective for GABAa drugs, suggesting that GABAa receptors play a major role in DS processing in the retina.
Cross-correlation analysis of taste neuron pairs in rat solitary tract nucleus
Authors: Adachi M. , Ohshima T. , Yamada S. , Satoh T.
Published: December 2017

1. Experiments were conducted to examine the possibility that the taste-sensitive neurons with similar taste-selectivity are preferentially innervated by common driving neurons whose taste-selectivity is also similar. 2. Multiple microelectrodes, in most cases a pair of glued electrodes, were inserted into the unilateral solitary tract nucleus (NTS) of the rat, and simultaneous recordings were made in neuron pairs responding to the four basic taste stimuli. The spike response density (RD) of each neuron during tastant stimulation was determined. Correlation coefficients of spike occurrence were calculated for each neuron pair during application of tastants and distilled water and also during spontaneous background activity. The frequency of correlated discharge (FC) of a neuron pair was measured as the area of the peak appearing on the cross-correlogram (CC). The FC value was divided by the RD value to calculate the weight of the correlated discharges in the output of each neuron (WC value). 3. Eleven pairs showed peaks in the CC constructed during tastant stimulation, whereas in other 11 pairs no peaks were found. The cross-correlation-positive group with peaks was composed of 18 NaCl-best (responding most vigorously to NaCl) and 4 HCl-best neurons, whereas the negative group without peaks included 9 NaCl-best, 9 HCl-best, and 4 sucrose-best neurons. 4. In the cross-correlation-positive pairs the taste quality most effective for one of the component neurons was often (13 NaCl-best and 2 HCl-best, 15/22 = 0.681) identical to the taste quality giving the highest probability of correlated discharge, i.e., highest FC value, in the neuron pair. 5. There were five cross-correlation-positive pairs (5/11 = 0.455) in which both of the component neurons were NaCl-best and the FC value was highest during NaCl stimulation. 6. The CCs constructed during water application exhibited peaks for all the pairs which gave positive cross-correlation in response to stimulation with tastants, whereas all pairs with negative cross-correlation during tastant stimulation never gave a detectable peak during water application. 7. In three pairs of the cross-correlation-positive group, the CCs constructed during spontaneous background activity without application of any liquid showed a small peak. 8. During NaCl stimulation some neurons exhibited relatively high FC values, but the WC values were always low. In contrast, during sucrose stimulation, the FC value was always low, but the WC value was quite high in some neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Monocular and binocular response properties of cells in the striate-recipient zone of the cat's lateral posterior-pulvinar complex
Authors: Casanova C. , Freeman R. D. , Nordmann J. P.
Published: December 2017

1. We have studied response properties of single cells in the striate-recipient zone of the cat's lateral posterior-pulvinar (LP-P) complex. This zone is in the lateral section of the lateral posterior nucleus (LP1). Our purpose was to determine basic response characteristics of these cells and to investigate the possibility that the LP-P complex is a center of integration that is dominated by input from visual cortex. 2. The majority (72%) of cells in the striate-recipient zone respond to drifting sinusoidal gratings with unmodulated discharge. 3. Cells in the LP1 are selective to the orientation of gratings, and tuning functions have a mean bandwidth of 31 degrees. More than one-half of these units are direction-selective. The preferred orientation and the tuning widths for the two eyes are generally well matched. However, a few cells exhibited the interesting property of opposite preferred directions for the two eyes. Orientation tuning for a small group of cells was different for the mean discharge and first harmonic components, suggesting a convergence from different inputs to these cells. 4. Two-thirds of LP1 cells are tuned to low spatial frequencies (less than 0.5 c/deg). The tuning is broad with a mean bandwidth of 2.2 octaves. The remaining one-third of the units are low-pass because they show no attenuation of their responses to low spatial frequencies. Both eyes exhibit the same spatial frequency preference and the same spatial frequency tuning. There is a high correlation between spatial frequency and orientation selectivities. 5. All cells tested are tuned for temporal frequency with a sharp attenuation for low frequencies. The optimal values range between 4 and 8 Hz, and the mean bandwidth is 2.2 octaves. 6. Cells in LP1 are mostly binocular. When monocular, cells are almost always contralaterally driven. Dichoptic presentation of gratings reveals the presence of strong binocular interaction. In almost all cases, these interactions are phase specific. The cell's discharge is facilitated at particular phases and inhibited at phases 180 degrees away. These binocular interactions are orientation dependent. 7. Twenty-five percent of the cells with phase-specific binocular facilitation appear to be monocular when each eye is tested separately. For three cells, we observed a non-phase-specific inhibitory effect of the silent eye. 8. Our findings indicate that LP1 cells form a relatively homogeneous group, suggesting a high degree of integration of multiple cortical inputs.(ABSTRACT TRUNCATED AT 400 WORDS)
Patterns of intracellular potentials in salamander mitral/tufted cells in response to odor stimulation
Authors: Hamilton K. A. , Kauer J. S.
Published: December 2017

1. Changes in membrane potential and temporal patterns of spikes were analyzed in 30 output cells in the salamander olfactory bulb in response to stimulation with 1-s pulses of the odorants isoamyl acetate, cineole, and camphor. The odor responses were more complex than responses to electrical stimulation of the olfactory nerve or olfactory tracts, with which they were compared. Most began with hyperpolarization and contained prolonged hyperpolarizing and depolarizing potentials that appeared to be compound postsynaptic potentials. These potentials were related to periods of spike inhibition and excitation. The temporal patterns of the responses resembled S-type (for suppression) and E-type (for excitation) patterns described previously in extracellular-unit studies. 2. In single cells, graded but nonmonotonic changes in the responses were observed with increases in the odor concentration from 10(-3) to 10(-1) vapor-phase saturation. Abrupt changes from one category of temporal response pattern to another were generally not observed in response to different concentrations of a single odorant but were frequently observed when the stimulus was changed from one odorant to another. 3. In S-type patterns, the first event was always membrane hyperpolarization and spike inhibition, regardless of the odor concentration. At all concentrations, simple S-type responses were observed in which a single period of hyperpolarization and inhibition lasted several seconds. At moderate to high concentrations, complex S-type responses were observed in which a period of excitation followed an initial period of hyperpolarization and inhibition. In these responses, spikes were often elicited near the termination of the odor pulse, occasionally as early as 300-400 ms after pulse onset. A prolonged period of inhibition followed the period of excitation. 4. In E-type patterns, the first event depended on the odor concentration. At all concentrations, complex responses were observed in which a period of excitation occurred with short latency, followed by a period of inhibition. At low to moderate concentrations, a brief initial period of hyperpolarization preceded the excitation. This initial period of hyperpolarization was always shorter than those in complex S-type responses to equivalent concentrations. However, the range of spike latencies overlapped that of S-type responses to high concentrations. With increasing odor concentration, spike latencies in the E-type responses decreased relative to the onset and peak of the initial hyperpolarization. At high concentrations. spikes were frequently elicited preceding a single period of hyperpolarization and inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)
Underlying mechanisms of the response specificity of expansion/contraction and rotation cells in the dorsal part of the medial superior temporal area of the macaque monkey
Authors: Tanaka K. , Fukada Y. , Saito H. A.
Published: December 2017

1. The dorsal part of medial superior temporal area (MST) has two unique types of visually responsive cells: 1) expansion/contraction cells, which selectively respond to either an expansion or a contraction; and 2) rotation cells, which selectively respond to either a clockwise or a counterclockwise rotation. In addition to selectivity for the mode of motion, both types of cells respond preferentially to movements over a wide field rather than over a small field. With the aim of understanding the underlying mechanisms of these selectivities, we carried out experiments on immobilized monkeys anesthetized with N2O. 2. Expansion/contraction and rotation of a pattern extending over a wide field contain three stimulus factors: 1) the spatial arrangement of different directions of movement, 2) the gradient in the speed of regional movement from the center to the periphery of the stimulus, and 3) the size change of texture components of the pattern in the expansion/contraction and the acceleration of movement of texture components toward the center of the stimulus in the rotation. The contribution of each factor to the activation of the cells was evaluated by comparing the response before and after removing the factor from the stimulus. The moving stimuli that lacked one or two of the factors were produced by the use of a cinematographic animation technique. 3. Withdrawal of the first factor, the spatial arrangement of different directions of movement, reduced the response of both Expansion/contraction and Rotation cells much more severely than either of the other two factors. We concluded that the first factor is far more important for activation than the other two. 4. These results are consistent with the model that Expansion/contraction and Rotation cells receive converging inputs from many directional cells with relatively small receptive fields in different parts of the visual field. Because MST receives strong fiber projections from MT, MT cells are candidates for the input cells. According to the model, if the convergence is organized so that the preferred directions of the input cells are arranged radially, the target cell will be an Expansion/contraction cell; if the input cells are arranged circularly, a Rotation cell will result.
Responses of primate spinothalamic tract neurons to renal pelvic distension
Authors: Ammons W. S.
Published: December 2017

1. Experiments were performed to examine responses of spinothalamic tract (STT) neurons to distension of the renal pelvis. Nineteen monkeys (Macaca fascicularis) were anesthetized with alpha-chloralose, paralyzed, and artificially ventilated. Fifty-four STT neurons in the T11-L2 segments were studied. Each cell was excited by renal nerve stimulation and had a somatic receptive field in the left flank and/or the abdomen. 2. Distension of the left renal pelvis to 50 mmHg for 20-30 s increased activity of 40 STT neurons. Two types of responses were observed. Six cells responded rapidly to the increase in renal pelvic pressure. Thereafter activity of these cells completely adapted. The other 34 cells also responded rapidly to the distension: however, the subsequent adaptation was not complete. Average activity before distension was 13 +/- 1 (SE) spikes/s. Distension increased activity to a peak of 42 +/- 3 spikes/s. Mean activity just before the end of the distension was 27 +/- 3 spikes/s. 3. The pelvic pressure-cell response relation was determined for 16 cells. Only one cell responded to a pressure of 20 mmHg. Three responded to 30 mmHg, and all others responded to 40 mmHg and higher. The average response threshold was 32 +/- 1 mmHg. Peak responses increased as distending pressure increased from 40-80 mmHg. Responses to a pressure of 100 mmHg were no greater than to 80 mmHg. Adapted levels of activity were also a function of distending pressure in the 40-80 mmHg range. 4. Probability of responses was unrelated to somatic input. However, cells with A delta- and C-fiber renal input were significantly more likely to respond to renal pelvic distension than cells with only A delta-renal input. Magnitude of responses to a pressure of 50 mmHg was not related to the type of renal input to the cells; however, among the cells tested at all pressures, cells with A delta- and C-fiber input had significantly greater responses to pressures of 80 and 100 mmHg. 5. Cells were studied in laminae I and IV-VII: responses were unrelated to laminar location. None of the 6 cells located in L2 responded to renal pelvic distension; 8 of 12 in L1 responded; 24 of 28 in T12 responded; and all 8 cells in T11 responded. 6. Stimulation of inhibitory receptive fields on the right hindlimb reduced activity of four cells to a significantly greater extent during pelvic distension than before pelvic distension.(ABSTRACT TRUNCATED AT 400 WORDS)
K+-channel blockade in trigeminal root ganglion neurons: effects on membrane outward currents
Authors: Spigelman I. , Puil E.
Published: December 2017

1. The effects of the applications of three K+-channel blockers on the membrane outward currents of neurons were studied with single-electrode voltage-clamp techniques in in vitro slice preparations of the trigeminal root ganglion (TRG) of guinea pigs. The investigations are the first reported attempts to apply these techniques to TRG neurons. 2. During perfusion with tetrodotoxin (TTX; 1 microM), transient outward currents were elicited at the termination of hyperpolarizing voltage commands from holding potentials near -40 mV. The amplitudes of these currents were reduced in conditions of high extracellular [K+]. The activation of such currents was rapid (less than 5 ms), and inactivation was complete at potentials within the activation range. Perfusion with low-[Ca2+], Co2+-containing solutions only slightly and inconsistently reduced the transient outward currents. 3. During combined application of TTX (1 microM) and tetraethylammonium (TEA) (10 mM), fast-activating sustained currents (greater than 1 s) were evoked by depolarizing commands from holding potentials near -70 mV. These currents were blocked completely by the additional inclusion of 5 mM 4-aminopyridine (4-AP) in the perfusing solution. 4. Applications of TEA (0.1-10 mM) produced dose-dependent reductions in the amplitudes of the transient outward currents. Applications of Cs+ also greatly reduced the currents. However, administrations of 4-AP (50 microM-5 mM) diminished these currents only slightly, and high doses of muscarinic agonists had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of electrical stimulation of locus coeruleus on the activity of neurons in the cat visual cortex
Authors: Sato H. , Fox K. , Daw N. W.
Published: December 2017

1. We studied the effect of electrically stimulating the locus coeruleus (LC) and iontophoresing noradrenergic antagonists on visual responses and spontaneous activity of individual cells in the cat primary visual cortex. 2. A bilateral projection from LC to visual cortex was demonstrated anatomically, by retrograde labeling using horseradish peroxidase. Where electrical stimulation of both ipsilateral and contralateral LC affected a cortical neuron, the effect induced by stimulating each side was similar. 3. One hundred and two cells were recorded in area 17: 52% of them had their activity suppressed and 36% had their activity facilitated by LC stimulation. The suppressive effect was predominant in cortical layers II + III and IV, whereas most cells in layer V and one-half of the cells in layer VI were facilitated by LC stimulation. This suggests that LC neurons innervate each cortical layer in a different manner. 4. Simple and complex cells were equally sensitive to LC stimulation. For simple cells, the suppressive effect of LC stimulation was dominant throughout all layers. For complex cells, the suppressive effect was dominant in layers II + III and IV, whereas the facilitatory effect was dominant in layers V and VI. 5. The suppressive effect of LC stimulation was blocked by iontophoretic application of beta-adrenergic receptor antagonists and the facilitatory effect was blocked by either alpha- or beta-adrenergic receptor antagonists. 6. Nonselective alpha-, and selective alpha 1- and alpha 2-receptor antagonists suppressed visual and spontaneous activity in almost all neurons tested, suggesting that these receptors are either facilitatory at a postsynaptic site or inhibitory at a site presynaptic to an inhibitory synapse in the visual cortex. 7. beta-Receptor antagonists facilitated activity in 45% and suppressed activity in 36% of the cells tested, suggesting there are both suppressive and facilitatory types of beta-receptors. 8. The effectiveness of alpha- and beta-antagonists on the activity of neurons without LC stimulation also suggested that spontaneously released noradrenaline activated noradrenergic receptors in the visual cortex even in the anesthetized and paralyzed cat. 9. In most cells tested, both alpha- and beta-receptor antagonists exerted effects on single neurons suggesting that endogenous noradrenaline acts on both alpha- and beta-receptors on the same cell. 10. The activation of LC did not improve the signal- (visual response)to-noise (spontaneous discharge) ratio of neurons in the visual cortex. 11. LC seemed to control the activity of each cortical layer differently, by activating different kinds of noradrenergic receptors in different layers.
Digit-muscle responses evoked from multiple intracortical foci in monkey precentral motor cortex
Authors: Sato K. C. , Tanji J.
Published: December 2017

1. The precentral motor cortex, including the anterior bank of the central sulcus of monkey (Macaca fuscata), was systemically penetrated with microelectrodes to determine the spatial organization of the microexcitable cortical elements that can produce responses in digit muscles. 2. At 200-microns intervals on each electrode track, low-current intracortical microstimuli were delivered and the muscle responses evoked from four digit muscles were recorded. The responses, obtained with 5, 8, 15, and 25 microA, were quantified and plotted on a map displaying an unfolded view of the precentral gyrus. 3. For all four muscles studied [first interosseus, thenar, extensor digitorum communis (EDC) and flexor digitorum profundus (FDP)], the effective stimulus points evoking muscle responses at a current of 5 microA were scattered over wide areas. The low-threshold foci, largely buried in the anterior bank of the central sulcus but partly extending to a region rostral to the sulcus, were found in multiple spots separated by a few millimeters. 4. Stimulation of individual sites at a current of 5 microA often evoked responses in several different muscles. Antagonist muscles were frequently coactivated. 5. A three-dimensional display of the distribution of response magnitude evoked from the precentral cortex indicates several peaks for each digit muscle. The peaks were either sharply demarcated from surrounding areas of minimal responses or gradually shifted into regions of low-grade responses. 6. Taken together, the data suggest that the digit area of motor cortex does not have a simple organization in which each muscle is represented by a single focus. Rather, each muscle has multiple foci that have varying degrees of efficacy in producing responses and with variable overlap onto foci of other muscles.
Responses of pigeon horizontal semicircular canal afferent fibers. II. High-frequency mechanical stimulation
Authors: Dickman J. D. , Correia M. J.
Published: December 2017

1. The horizontal semicircular canals of anesthetized (barbiturate/ketamine) pigeons were mechanically stimulated by the use of a piezoelectric micropusher that provided controlled indentation of the surgically exposed membranous horizontal semicircular duct. 2. Extracellular action potentials from single horizontal semicircular canal afferent (HCA) fibers were recorded during sinusoidal mechanical stimulation. This method of stimulation was shown in the companion paper to produce equivalent responses to those produced by rotation for frequencies ranging from 0.01 to 10 Hz. 3. Sinusoidal mechanical stimulation produced clearly entrained action potentials in some HCA fibers up to a frequency of 400 Hz (highest stimulus frequency tested), with stimulus probe displacements of +/- 1.0 and +/- 2.5 microns. Thirty-four HCA fibers were thoroughly studied. 4. For most HCA fibers, the number of action potentials per stimulus cycle decreased as stimulus frequency increased, until only one action potential per stimulus cycle was elicited. The point at which only one spike per stimulus cycle was observed was dependent on both the fiber's resting mean discharge rate (MDR) and the fiber's coefficient of variation (CV) obtained during the MDR. 5. Dynamic response properties of individual HCA fibers were found to be correlated with the fiber's CV and the resting level MDR. Neurons with lower CV values had less adaptation, higher short time constants, and lower high corner frequencies than did neurons with high CV values. For a given CV class of HCA fibers, neurons with higher MDRs had more enhanced gains and more advanced phase shifts at high stimulus frequencies than did neurons with lower MDRs. 6. Transfer function parameters affecting the dynamics of the high-frequency response were derived from the mean gain and phase shift values of regular-, intermediate-, and irregular-firing HCA fibers. Best-fit short time constant (tau S) values of 4.6, 1.9, and 2.0 ms; hair cell membrane time constant (tau M) values of 10.3, 13, and 7 ms; excitatory postsynaptic membrane time constant (tau E) values of 0.8, 0.4, and 0.5 ms; and synaptic delay time constant (tau D) values of 0.5, 0.5, and 1.4 ms were determined for regular, intermediate, and irregular classes of HCA fibers, respectively. 7. The values of 4.6, 1.9, and 2.0 ms derived for the regular, intermediate, and irregular afferents would suggest upper-corner frequencies of 35, 84, and 80 Hz for these classes of HCA fibers, respectively.
Corticomotoneuronal postspike effects in averages of unrectified EMG activity
Authors: Botteron G. W. , Cheney P. D.
Published: December 2017

1. Spike-triggered averaging (SpTA) of rectified electromyograms (EMGs) in awake monkeys is recognized as an effective means of establishing causal relations between cortical/cell discharge and muscle activity. The appearance of postspike facilitation (PSF) in averages of rectified EMG activity is interpreted as evidence of an underlying excitatory synaptic linkage between the trigger cell and motoneurons. Cells producing PSF are referred to as corticomotoneuronal (CM) cells. Similarly, postspike suppression (PSS) is interpreted as evidence of underlying inhibitory synaptic linkages. Studies to date have focused almost exclusively on averages of full-wave rectified EMG activity. Because the potential utility of SpTA of unrectified EMG activity has not been systematically examined, we compared postspike effects in SpTAs of rectified and unrectified EMGs for 44 cortical cells yielding 293 cell-target muscle pairs (CMPs). 2. Clear PSF was found in 110 of 293 averages of rectified EMG activity from 28 known CM cells. Forty-nine of these 110 CMPs (45%) also showed clear postspike effects (PSE) in the corresponding averages of unrectified EMGs activity. Loss of effects in averages of unrectified EMGs can be attributed to cancellation of the negative and positive phases of motor unit potentials. Mean onset latencies were similar for effects in rectified and unrectified EMGs [6.9 +/- 1.8 (SD) ms vs. 6.6 +/- 1.2 (SD) ms]. Overall, the magnitudes of effects measured as peak-to-noise ratios were also similar for effects in the two groups (8.8 vs. 8.7). The 61 CMPs that showed clear PSF in rectified EMGs but no effects in corresponding unrectified EMGs had, as a group, longer and more dispersed onset latencies and were weaker in magnitude than those that showed effects in both rectified and unrectified EMGs. Moreover, the occurrence of clear effects in averages of unrectified EMGs was correlated with the strength of PSF (75% of strong but only 29% of weak PSFs showed clear PSEs in averages of unrectified EMG activity). 3. Clear PSS was observed in 24 (8%) averages of rectified EMGs derived from nine cells. Remarkably, clear PSEs were found in 12 of the corresponding averages of unrectified EMG activity.(ABSTRACT TRUNCATED AT 400 WORDS)
Spatiospectral properties of goldfish retinal ganglion cells
Authors: Bilotta J. , Abramov I.
Published: December 2017

1. Responses of single ganglion cells from isolated goldfish retinas were recorded during presentation of various spatial and spectral stimuli. Each cell was classified along several spatial [spatial summation class, spatial contrast sensitivity function (CSF), and response to contrast] and spectral (Red-ON, Red-OFF or Red-ON/OFF, and spectral opponency/nonopponency) dimensions. 2. Linearity of spatial summation was determined from responses to contrast-reversal sinusoidal gratings positioned at various locations across the receptive field of the cell. CSFs were derived from responses to sinusoidal gratings of various spatial frequencies and contrasts, drifting across the cell's receptive field at a rate of 4 Hz. Response to contrast was determined from responses to variations in contrast of a sinusoidal grating of optimal spatial frequency. Spectral classifications were based on responses to monochromatic stimuli presented separately to the center and surround portions of the receptive field. 3. Linearity of spatial summation (X-, Y-, and W-like) was independent of the cell's spectral properties; for example, an X-like cell could be classified as either a Red-ON, Red-OFF, or Red-ON/OFF center cell and as spectrally opponent or nonopponent. 4. There were differences in response to contrast across spectral categories. Red-OFF center cells were very sensitive to contrast compared with Red-ON center cells. Spectrally nonopponent cells were more responsive to contrast than spectrally opponent cells. 5. There were dramatic differences across the spectral categories in relative sensitivity to low spatial frequency stimuli; however, the spatial resolution (i.e., sensitivity to high spatial frequencies) of each spectral classification appeared to be similar.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of competition among sensory neurons in regulation of pattern of innervation at their central and peripheral targets
Authors: Mendelson B. , Frank E.
Published: December 2017

1. The importance of competitive interactions among muscle sensory afferents on their projections to central and peripheral targets was studied by producing large reductions in the number of afferents during development. Removal of the brachial dorsal root ganglion (DRG2), which normally supplies the entire sensory innervation of the forelimb, in bullfrog (Rana catesbeiana) tadpoles caused a smaller number of neurons in the adjacent thoracic ganglion (DRG3) to sprout into the forelimb and into the brachial spinal cord. 2. Horseradish peroxidase labeling in postmetamorphic animals showed that DRG3 neurons innervating the triceps muscle arborize in a novel but now appropriate area of the spinal cord, the region containing motoneuronal dendrites. These foreign afferents do not arborize in inappropriate regions of the spinal gray matter, and their collaterals have the same rostrocaudal distribution as those of normal DRG2 muscle afferents. 3. After metamorphosis, the number of DRG3 sensory axons in individual triceps muscle nerves was determined. Normally, two-thirds of all triceps afferents project to the medial head alone, even though each of the three heads is of similar size and is contacted by similar numbers of motoneurons. After DRG2 removal, although the total number of DRG3 afferents projecting to the triceps muscle was smaller than normal, the medial head still received approximately two-thirds of the axons, just as in normal frogs. These results suggest that the proportional sensory innervation of the triceps muscle-heads is not dependent on competitive interactions among afferents. 4. DRG3 afferents projecting to the forelimb also sprouted to innervate appropriate brachial motoneurons. The average strength of connection between individual sensory and motor neurons was found to be the same as in normal animals, even though there was presumably more central target space available for each afferent axon. This suggests that the number and/or strength of central connections made by individual fibers may be an intrinsic property of muscle sensory neurons.
Conjoint action of phosphatidylinositol and adenylate cyclase systems in serotonin-induced facilitation at the crayfish neuromuscular junction
Authors: Dixon D. , Atwood H. L.
Published: December 2017

1. Pulsatile application of serotonin (5-HT) leads to facilitation of excitatory postsynaptic potentials (EPSPs) in crayfish "opener" neuromuscular preparations. The facilitation resulting from a single application of serotonin shows two phases: an early, rapidly decaying phase, and a less intense, long-lasting phase of 1- to 2-h duration. A previous study implicated the phosphatidylinositol system as an essential component in serotonin-induced facilitation, especially the early phase. The present study was conducted to determine the roles of the adenylate cyclase and phosphatidylinositol systems in both phases of serotonin-induced facilitation. 2. Relatively brief applications of agents known to affect the intracellular concentration of cAMP (forskolin, 1 microM; and IBMX, 100 microM) cause an increase in EPSP amplitude, which persists for 1-2 h. 3. The duration of the less intense, long-lasting phase of serotonin-induced facilitation is prolonged in the presence of 1 microM IBMX. This concentration of IBMX does not affect EPSP amplitude by itself. A membrane-permeant analog of cAMP (applied in concentrations less than or equal to 1 mM) is also not effective in altering EPSP amplitude. However, when dibutyryl cAMP is applied in the presence of 1 microM IBMX, EPSP amplitude is increased (60-80%). 4. Localized presynaptic injection of the "Walsh Inhibitor" (PKI), which inhibits cAMP-activated protein kinase, blocks the less intense, long-lasting phase of serotonin-induced facilitation at synapses near the site of injection. Normal facilitation develops at synapses within the same preparation remote from the site of injection. Distribution of the injected inhibitor within the axon can be visualized by tagging PKI with a fluorescent marker.(ABSTRACT TRUNCATED AT 250 WORDS)
Morphological and functional aspects of two different types of hair cells in the goldfish sacculus
Authors: Sugihara I. , Furukawa T.
Published: December 2017

1. With the use of whole-cell mode of the patch-clamp method, we examined the electrical responses of hair cells enzymatically isolated from the goldfish sacculus. 2. Hair cells from the rostral saccule had a short cell body and were ovoidal or eggplantlike in shape, whereas hair cells from the caudal saccule had a variable shape. Many had a longer cell body and were cylindrical or gourd-like in shape, but some short hair cells were also present in the caudal saccule. 3. The short hair cells had a resting potential of about -75 mV. In current-clamp experiments, these hair cells elicited damped oscillatory-potential changes of a relatively small amplitude in response to a depolarizing current. A current in the opposite direction produced a slow hyperpolarization, much larger in amplitude. 4. Resonant frequency of the short, or the oscillatory, type of hair cells ranged from 40 to 200 Hz or higher. However, resonance was generally of a poor quality as compared with that noted for hair cells in the turtle cochlea or frog sacculus. 5. The long hair cells had a resting potential of -90 to -100 mV. In current-clamp experiments, these hair cells elicited an all-or-none spike approximately 50 mV in amplitude in response to a depolarizing current. The spike was usually followed by a plateau, which was maintained for the duration of the depolarizing pulse. In some hair cells, damped slow oscillatory waves were evoked at a rate of 5-15 Hz. On the other hand, a hyperpolarizing current produced potential changes much smaller in amplitude. 6. Voltage-clamp experiments showed that Ca2+-activated K+ channel and A-current, especially its high-threshold subclass, were involved in the generation of outward rectification in the oscillatory-type hair cells. On the other hand, Na+, in addition to Ca2+, was involved in the generation of spike in the spike-type hair cells. Spike potentials were elicited even in the presence of tetrodotoxin (TTX), but the rate of rise was slower as compared with the intact spikes. 7. The spike-type hair cells had an inwardly rectifying K+ channel similar to that noted in the tunicate egg and chick vestibular hair cell. However, the oscillatory-type hair cells had an inwardly rectifying channel similar to the hyperpolarization-activated current, Ih, of the rod inner segment, or sinoatrial nodal cell, or lacked the inwardly rectifying channel. Differences in the resting membrane potential between the oscillatory- and spike-type hair cells are probably related to differences in the inwardly rectifying channels. 8. Effects of sound stimulation were simulated by injecting a half-wave rectified sinusoidal current of various frequencies.(ABSTRACT TRUNCATED AT 400 WORDS)
Does an extraocular proprioceptive signal reach the superior colliculus?
Authors: Nelson J. S. , Meredith M. A. , Stein B. E.
Published: December 2017

1. The primary functions of the superior colliculus (SC) are thought to include both the spatial localization of sensory stimuli and the initiation of an orienting response. It has been hypothesized that, in cat, both of these SC functions may be influenced by feedback from the extraocular muscles. The present investigation was initiated to determine which SC cells receive this extraocular muscle feedback and how this feedback influences the discharge properties of SC cells and their ability to integrate input from other sensory modalities. These questions were addressed in cats prepared with various anesthetic agents. 2. During the course of these experiments it became apparent that responses of SC cells to extraocular muscle stimulation could be elicited only under very specific conditions, and these observations questioned the existence of functional extraocular inputs to SC cells. 3. Rotating the eye or stretching the extraocular muscles was never found to be effective in activating SC cells unless the drug chloralose was used in the experimental preparation. In these chloralose-anesthetized animals, responses to eye rotation or muscle stretch were long and variable in latency, the discharge did not reflect the metrics of the stimulus, and the velocity and amplitude thresholds of these cells usually exceeded the cat's oculomotor range. Responses usually consisted of one to three impulses and, in appropriate conditions, could be inhibited by responses to visual or auditory stimuli. 4. The origin of this SC response to eye rotation/extraocular-muscle stretch could not be localized to the extraocular muscles. Responses to passive stretch of extraocular muscles were not eliminated by anesthetizing the muscles with injections of lidocaine. Active contraction of the extraocular muscles induced by electrical stimulation of the oculomotor nerve was never observed to evoke SC responses. Furthermore, transection of the muscle nerves, which isolated the extraocular-muscle receptors from the CNS, did not affect the response initiated by stretching the extraocular muscles. However, in the absence of intact muscle nerves, pulling the periorbital tissue elicited responses very much like those produced by stretching the muscles in the intact preparation, suggesting the periorbita as the source of responses in intact preparations as well. 5. These data are not consistent with the hypothesis that feedback from extraocular-muscle receptors influences the activity of SC cells.
Simulation of motion on the skin. II. Cutaneous mechanoreceptor coding of the width and texture of bar patterns displaced across the OPTACON
Authors: Gardner E. P. , Palmer C. I.
Published: December 2017

1. These experiments assay the functional significance of receptive-field architecture for information processing. Rapidly adapting (RA) afferents have been previously shown to converge information from clusters of 14-25 Meissner's corpuscles, whereas afferents innervating Pacinian corpuscles (PCs) have only a single, large receptor terminal. We tested two opposing hypotheses of functional architecture: 1) summation models, in which an afferent integrates signals from all of its terminals, showing monotonic increases in activity as a function of contact area, and 2) winner-take-all models, in which the most strongly activated receptor in the cluster dominates axonal output by cancellation of signals from other branches. 2. Bar and stripe patterns have been swept across the finger or palm of the monkey's hand at speeds of 30-120 mm/s with the use of a computer-controlled grid of sequentially activated miniature probes (OPTACON stimulator). The dense packing of OPTACON probes permits placement of up to five groups of stimulators within an individual receptive field, allowing us to activate one or more clusters of Meissner's corpuscles simultaneously and to stimulate the bulbar corpuscle of PC afferents at different orientations through the skin. Integration of information from moving bar patterns has been tested with two protocols. In the variable width protocol, the total number of activated rows in the pattern is varied from one to five, with a constant spacing of 1.2 mm between pulsed rows. In the variable density protocol, the length of skin stimulated is held constant at 5 mm and the spacing of stimuli varied. 3. RA afferents show no evidence of summation of inputs within their receptive fields. Motion of wide bars across the field increases the duration of firing but not the total spikes evoked by each pulse. Responses to the leading edge of wide bars were found to be identical to those evoked by a single-row bar. Simultaneous activation of two to five rows evokes the same or fewer spikes per pulse than the most effective individual row tested alone. When broad-bar patterns are centered over the field, contacting the maximum number of receptors, RAs follow activity in the dominant branch or terminus, suppressing additional inputs. Lack of summation is observed at all pulse frequencies tested (25-100 Hz). 4. Moving bar patterns evoke responses as long as at least one row stimulates the receptive field; broader patterns evoke longer spike trains whose total number of impulses is proportional to bar width.(ABSTRACT TRUNCATED AT 400 WORDS)