bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantal release and facilitation at frog neuromuscular junctions at about 0 degrees C
Authors: Molgo J. , Van der Kloot W.
Published: December 2017

1. It has been reported that at the frog neuromuscular junction at temperatures around 0 degrees C the release of transmitter quanta following nerve stimulation becomes disrupted, and the facilitation obtained after a second stimulus is no longer detectable. We thought that further investigation might give insight into the mechanism of quantal release, so we undertook experiments on Rana pipiens and Rana berlanieri. 2. In these species neuromuscular transmission occurs at temperatures as low as -0.8 degrees C. As the temperature is decreased further, transmission fails, apparently by a block in nerve conduction. The number of quanta released per stimulus decreases as temperature is lowered, with a Q10 of approximately 2.4. Owing to the decrease in the quantal output and the probabilistic nature of the release process, in occasional single records of an end-plate current (EPC), the pattern of release appeared disrupted. The kinetics of quantal release was studied by the use of a deconvolution method, which requires recording of EPCs and miniature EPCs (MEPCs) in preparations in high Mg(2+)-low Ca2+ solution. At approximately 0 degrees C the pattern of quantal release was similar to that at higher temperatures, although with a slower time course. At 0 degrees C the peak of release occurred approximately 3.5 ms after onset. 3. In our experiments there was almost no difference in the frequency of MEPCs at 22 degrees C and at 0 degree C. 4. We observed as much facilitation to a second stimulus at 0 degree C as at 10 degrees C. The Q10 for the decay of facilitation with time was between 1.9 and 2.3.(ABSTRACT TRUNCATED AT 250 WORDS)
Selectivity for relative motion in the monkey superior colliculus
Authors: Davidson R. M. , Bender D. B.
Published: December 2017

1. Cells in the superficial layers of the colliculus were studied in immobilized monkeys anesthetized with nitrous oxide. We examined sensitivity to the relative motion between two stimuli: a small target in a cell's receptive field and a large random-dot background pattern that filled most of the visual field outside the receptive field. 2. Most cells were nonselective for either target direction or speed when the background pattern was stationary but were selective for both direction and speed relative to a moving background. Selectivity for relative motion was independent of the absolute direction and speed of both target and background. When both moved at the same speed in the same direction, the response evoked by the target was strongly suppressed. Changing the background direction relative to the target reduced the suppression; suppression was minimal when the two moved in opposite directions. Selectivity for relative direction was broad: the average tuning width at half-amplitude was 136 degrees. When target and background moved in the same direction, increasing or decreasing background speed relative to the target likewise reduced suppression. Average tuning width for relative speed was 1.4 log units. 3. Selectivity for relative motion was a global phenomenon. Suppression was present even when the background pattern was excluded from a region 10 times the receptive-field diameter. However, suppression gradually diminished with increasing distance between the receptive field and the background pattern. 4. Relative motion selectivity was most common in the deeper part of the superficial layers. Ninety percent of the cells below the middle of the stratum griseum superficiale were selective for relative direction, whereas above this level only 45% of the cells were. 5. Cells in the magnocellular and parvocellular layers of the lateral geniculate nucleus did not show selectivity for relative direction. 6. We suggest that the lower one-half of the superficial grey layer and the stratum opticum together constitute a subdivision of the superior colliculus that is specialized to detect strong discontinuities in relative motion. Descending input by way of the corticotectal tract is probably essential for the detection process. the projections from this tectal motion zone to the pulvinar, and from there to prestriate cortex, may provide a feedback pathway through which motion discontinuities such as occur at dynamic occlusion boundaries can influence local feature detection by cortical neurons.
Delayed excitatory connections in the flight system of the locust
Authors: Robertson R. M.
Published: December 2017

1. Synaptic interactions between identified neurons in the flight system of the locust were investigated by the use of standard intracellular recording and staining techniques. The intent was to determine the distribution and functional significance of delayed excitatory connections, which have been previously described. 2. For one inhibitory connection it was demonstrated that subthreshold depolarization of the presynaptic neuron was sufficient to cause release of transmitter at the synapse. This established the existence of graded interactions between spiking flight neurons. 3. Three inhibitory interneurons were found to cause delayed excitatory responses in several other neurons. Often these were coupled with direct inhibitory connections between the same pre- and postsynaptic neurons, resulting in an inhibitory/excitatory (I/E) postsynaptic potential (PSP). The two phases of this PSP were variable. 4. Delayed excitatory connections appeared powerful while the flight system was inactive. However, these connections were disabled during flight rhythms at the phase when the presynaptic neuron was depolarized and firing action potentials. This was likely to be due to the nature of the disynaptic disinhibitory interaction being via (an) intervening neuron(s) with oscillating membrane potentials and thresholds for release of transmitter. 5. Thus connections demonstrated when flight rhythms were not expressed changed their character during flight rhythms. The delayed excitatory connections in this system probably reflect complex circuits of inhibition mediated by graded interactions and have little functional significance as phenomena in their own right.
Changes in central delay of soleus H reflex after facilitatory or inhibitory conditioning in humans
Authors: Abbruzzese M. , Reni L. , Favale E.
Published: December 2017

1. Central delay (CD) changes after facilitatory or inhibitory conditioning of the soleus H reflex have been investigated in a group of normal subjects as a function of the conditioning and test stimulus intensities and also as a function of the Hmax/Mmax ratio. Both facilitation and inhibition of the reflex response have been obtained by conditioning stimulation of the ipsilateral tibial nerve at suitable conditioning-test stimulus intervals. CD changes have been extrapolated from the variations of the time interval between afferent and efferent neural volleys underlying the H reflex, directly recorded from the sciatic nerve. 2. The CD was significantly decreased by facilitatory and increased by inhibitory conditioning. Facilitatory CD changes were positively related to test stimulus strength (at a given conditioning stimulus intensity) and negatively related to conditioning stimulus strength (at a given test stimulus intensity). Both trends were reversed after inhibitory conditioning. The effectiveness of facilitatory conditioning was positively related to the individual Hmax/Mmax ratio whereas a negative relationship could be observed after inhibitory conditioning. 3. Also, the "conditioning threshold" (the minimal conditioning stimulus strength affecting the reflex size) and the "maximal conditioning effect" (the conditioning stimulus intensities leading to either the saturation of the facilitatory effect or the suppression of the reflex response) were significantly related to the Hmax/Mmax ratio. 4. We suggest that temporal changes in the H reflex pathway after facilitatory or inhibitory conditioning stimuli depend both on the size of the motoneuronal pool underlying the reflex response, as determined by the test stimulus intensity, and on the individual excitability of the motoneuronal pool, as defined by the Hmax/Mmax ratio.(ABSTRACT TRUNCATED AT 250 WORDS)
Anesthetic blockade of the dorsolateral funiculus enhances evoked activity of spinal cord dorsal horn neurons
Authors: Pubols L. M. , Simone D. A. , Bernau N. A. , Atkinson J. D.
Published: December 2017

1. A previous study of cat lumbar dorsal horn neurons found reduced responsiveness to A-fiber stimulation 1.5-12 h after thoracic dorsolateral funiculus (DLF) lesions. The present study was undertaken to determine whether this was due to the loss of descending activity or to factors specifically associated with injury by examining the response properties of dorsal horn cells before and during lidocaine blockade of the ipsilateral DLF. Electric shocks applied to the dorsal columns were used to search for dorsal horn cells. Noxious and nonnoxious cutaneous mechanical stimuli and graded electrical stimuli applied to the tibial nerve were used to activate peripheral afferent fibers. Cells were classed as low threshold (LT), high threshold (HT), or multireceptive (MR), according to their responses to natural stimuli. Baseline data were collected from a total of 58 cells. Twelve of these were further studied after lidocaine injection of the DLF. All cells examined with lidocaine were in dorsal horn laminae III-V. 2. All cells responded to activation of tibial nerve A fibers. However, the median threshold for the HT and MR cells (200 microA) was significantly higher than that of the LT cells (75 microA). Some cells in each class were also activated by C fibers (10, 70, and 64% of the LT, HT, and MR cells, respectively). 3. For the cells that were further characterized by lidocaine blockade of the DLF, all LT cells (n = 3) responded only to A-fiber stimulation, and all HT (n = 3) and MR cells (n = 6) responded to both A- and C-fiber stimulation. 4. For LT cells, responses evoked by mechanical and electrical stimuli were unaltered by lidocaine blockade. 5. HT and MR cells showed enhanced responses to electrical stimulation of C fibers during DLF blockade. There was no consistent effect of the blockade on A-fiber-evoked responses. 6. Two of three HT and four of six MR cells studied with lidocaine had spontaneous activity, which exhibited a small but significant increase during DLF blockade. 7. Receptive fields for noxious stimulation expanded in two of six MR cells during DLF blockade. Two of three HT cells developed responses to tactile stimuli during the blockade. 8. In two additional cells (1 HT and 1 MR), spontaneous activity and responses to C-fiber input increased after the DLF was cut.(ABSTRACT TRUNCATED AT 400 WORDS)
Excitatory amino acid receptor-mediated transmission in geniculocortical and intracortical pathways within visual cortex
Authors: Larson-Prior L. J. , Ulinski P. S. , Slater N. T.
Published: December 2017

1. A preparation of turtle (Chrysemys picta and Pseudemys scripta) brain in which the integrity of the intracortical and geniculocortical pathways in visual cortex are maintained in vitro has been used to differentiate the excitatory amino acid (EAA) receptor subtypes involved in geniculocortical and intracortical synapses. 2. Stimulation of the geniculocortical fibers at subcortical loci produces monosynaptic excitatory postsynaptic potentials (EPSPs) in visual cortical neurons. These EPSPs are blocked by the broad-spectrum EAA receptor antagonist kynurenate (1-2 mM) and the non-N-methyl-D-aspartate (NMDA) antagonist 6, 7-dinitroquinoxaline-2,3-dione (DNQX, 10 microM), but not by the NMDA antagonist D,L-2-amino-5-phosphonovalerate (D,L-AP-5, 100 microM). These results indicate that the geniculocortical EPSP is mediated by EAAs that access principally, if not exclusively, EAA receptors of the non-NMDA subtypes. 3. Stimulation of intracortical fibers evokes compound EPSPs that could be resolved into three components differing in latency to peak. The component with the shortest latency was not affected by any of the EAA-receptor antagonists tested. The second component, of intermediate latency, was blocked by kyurenate and DNQX but not by D,L-AP-5. The component of longest latency was blocked by kynurenate and D,L-AP-5, but not by DNQX. These results indicate that the compound intracortical EPSP is comprised of three pharmacologically distinct components that are mediated by an unknown receptor, by quisqualate/kainate, and by NMDA receptors, respectively. 4. Repetitive stimulation of intracortical pathways at 0.33 Hz produces a dramatic potentiation of the late, D,L-AP-5-sensitive component of the intracortical EPSP. 5. These experiments lead to a hypothesis about the subtypes of EAA receptors that are accessed by the geniculocortical and intracortical pathways within visual cortex.
Long-term optical recording of patterns of electrical activity in ensembles of cultured Aplysia neurons
Authors: Parsons T. D. , Salzberg B. M. , Obaid A. L. , Raccuia-Behling F. , Kleinfeld D.
Published: December 2017

1. Left upper quadrant (LUQ) cells isolated from the abdominal ganglion of Aplysia were maintained in culture to study how the cellular and synaptic properties of individual neurons contribute to the generation of patterns of electrical activity by neuronal ensembles. 2. Conventional microelectrodes were used to examine the spiking characteristics of individually cultured LUQ cells in vitro and to characterize their synaptic interactions. 3. In vitro, in contrast to in situ, LUQ neurons innervate other LUQ neurons. Intracellular recordings from pairs of LUQ cells showed that the prevalent type of postsynaptic potential was purely inhibitory. The other type of response was a dual-action postsynaptic potential, with inhibition followed by a delayed, slow excitation. 4. We established a set of criteria for the use of multiple-site optical recording techniques, in combination with impermeant probes of membrane potential, to observe the patterns of electrical activity generated by ensembles of co-cultured LUQ cells. 5. The spiking activity of individual cells within the neuronal ensembles was detected by means of the change in optical absorption of cells that were vitally stained with the dye RH155. The change in absorption was typically delta A congruent to 4 X 10(-4) per spike. We achieved a signal-to-noise (peak-to-peak) ratio of approximately 10 for a 50 X 50-microns photodetector field and an incident intensity of approximately 10 mW/cm2, close to the theoretical limit. 6. These conditions permitted, for the first time, continuous optical recording from cultured neurons for periods of up to 3 h with no discernible photodynamic damage or photobleaching. This long-term optical recording permitted examination of the different patterns of electrical activity generated by individual neuronal ensembles under several different experimental conditions. 7. An elaborate tracery of regenerated neurites present in these cultures resulted in individual photodetectors recording simultaneously the activity of multiple neurons. We reconstructed the temporal firing patterns for individual neurons within ensembles even with all the neurons active simultaneously and determined the functional connections in the ensemble by analyzing the temporal relationships between firing patterns of individual neurons. Excitatory as well as inhibitory functional interactions could be observed within the neuronal ensemble, the latter after the tonic activity of the neurons was increased by reducing the extracellular [Mg2+]. 8. Examination of the optical data from ensembles constructed from identified cells having characteristic physiological responses allowed us to address the question of how cellular and synaptic properties affect the patterns of electrical activity generated by neuronal ensembles.(ABSTRACT TRUNCATED AT 400 WORDS)
Different mechanical transduction mechanisms for the immediate and delayed responses of rat C-fiber nociceptors
Authors: White D. M. , Levine J. D.
Published: December 2017

1. In this electrophysiological study, action potentials from single C-fibers were recorded in fine filaments teased from the rat saphenous nerve. We evaluated the effect of pharmacological agents on the responses of C-fiber mechanoheat nociceptors (C-MH; n = 53) after sustained suprathreshold and subthreshold stimuli. 2. Sustained suprathreshold mechanical stimuli elicit an immediate burst of activity that quickly adapts to a low-level firing that is maintained during the stimulus. Sustained subthreshold stimuli activate C-MHs after a delay and elicit a constant, low-level firing. 3. Gentamicin, a known suppressor of mechanosensory cell activity, blocked the initial rapid burst response to suprathreshold stimuli (n = 11) but had no effect on the adaptive low-level firing. The latency of the delayed activation of C-MHs induced by sustained subthreshold stimuli was not affected by gentamicin. 4. Sphingosine, a protein kinase inhibitor, increased the latency of the delayed activation of C-MHs (n = 7) to sustained subthreshold stimuli; phorbol 12-myristate 13-acetate (TPA), a protein kinase C activator, decreased the latency of the delayed activation of C-MHs (n = 9); and 4 alpha-phorbol, an inactive isomer of TPA, had no effect on the latency of the delayed activation (n = 7). Sphingosine, TPA, and 4 alpha-phorbol had no affect on the initial burst response induced by suprathreshold stimuli. 5. K+ channel blockers, 4-aminopyridine (n = 9) and noxiustoxin (n = 5), decreased the latency of the delayed activation of C-MHs to sustained subthreshold stimuli but had no effect on the initial burst response of C-MHs to suprathreshold stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)
Isotropic connections generate functional asymmetrical behavior in visual cortical cells
Authors: Worgotter F. , Niebur E. , Koch C.
Published: December 2017

1. We study the relationship between structure and function in inhibitory long-range interactions in visual cortex. The sharpening of orientation tuning with "cross-orientation inhibition" is used as an example to discuss anisotropies that are generated by long-range connections. 2. In this study, as opposed to the detailed cortex model described in a previous report, a model of the cortical orientation column structure is proposed in which cortical cells are described only by their orientation preference. 3. We present results using different geometric arrangements of orientation columns. In the simplest case, straight parallel orientation columns were used. We also utilized more realistic, curved columns generated by a simple algorithm. The results were confirmed by the study of a patch of real column structure, determined experimentally by Swindale et al. 4. A given cell receives functionally defined cross-orientation inhibition if the cell receives inhibitory input that is strongest along its nonpreferred orientation. On the other hand, a cell is said to receive structurally defined cross-orientation inhibition if the inhibition arises from source cells with an orientation preference orthogonal to that of the target cell. Even though those definitions seem to describe similar situations, we show that, in the general case, structurally defined cross-orientation inhibition does not efficiently sharpen orientation selectivity. In particular, for straight and parallel columns, structurally defined cross-orientation inhibition results in unequal amounts of inhibition for whole cell populations with different preferred orientations. 5. In more realistic column structures, we studied the question of whether structural cross-orientation inhibition could be implemented in a more efficient way. However, for the majority of cells, it is demonstrated that their nonpreferred stimulus will not preferably excite "cross-oriented" cells. Thus structural cross-orientation inhibition is not efficient in real cortical columns. 6. We propose a new mechanism called circular inhibition. In this connection scheme, a target cell receives inhibitory input from source cells that are located at a given distance (the same for all cells) from the target cell. Circular inhibition can be regarded as two-dimensional long-range lateral inhibition. As opposed to structural cross-orientation inhibition, this mechanism does not introduce unwanted anisotropies in the orientation tuning of the target cells. It is also conceptually much simpler and developmentally advantageous. It is shown that this connection scheme results in a net functional cross-orientation inhibition in all realistic column geometries. The inhibitory tuning strength obtained with circular inhibition is weak and similar to that measured in reality.(ABSTRACT TRUNCATED AT 400 WORDS)
Quinolones and fenbufen interact with GABAA receptor in dissociated hippocampal cells of rat
Authors: Akaike N. , Shirasaki T. , Yakushiji T.
Published: December 2017

1. Interaction of quinolone antibiotics and the anti-inflammatory agent fenbufen with the gamma-aminobutyric acid-A (GABAA) receptor-chloride channel complex in pyramidal neurons freshly dissociated from the hippocampal CA1 region of the rats was investigated in whole-cell mode, using the patch-clamp technique under voltage-clamp conditions. 2. Quinolones in clinical doses had no effects on the GABA-gated Cl- current (ICl) but slightly suppressed the response at concentrations greater than 10(-5) M. A metabolite of fenbufen, 4-biphenylacetic acid (BPA), also had little effect on the GABA response at therapeutic concentrations. 3. Coadministration of one of quinolones and BPA suppressed the GABA-gated ICl with increase in each of them in a concentration-dependent manner, and there was a parallel shift of the concentration-response curve for GABA to the right but with no effect on the maximum response, thereby indicating a competitive antagonism. The inhibitory potency of antibiotics in combination with BPA was in the order of norfloxacin much greater than enoxacin greater than cyprofloxacin greater than pipemidic acid much greater than ofloxacin greater than cinoxacin = piromidic acid = nalidixic acid = 0. 4. Norfloxacin and BPA, administered simultaneously, also strongly suppressed pentobarbital sodium (PB)-gated ICl, but they did not act on benzodiazepine (BZP) receptors. 5. Both GABA- and PB-induced ICls reversed at the Cl- equilibrium potential (ECl). In the presence of BPA, the quinolone-induced inhibition of GABA-gated ICls showed no voltage dependence. 6. It was concluded that, in the presence of an anti-inflammatory agent, the quinolone antibiotics decrease the affinity of GABAA receptors, the result being induction of epileptogenic neurotoxicities.
Ocular responses to translation and their dependence on viewing distance. II. Motion of the scene
Authors: Busettini C. , Miles F. A. , Schwarz U.
Published: December 2017

1. The ocular following responses induced by brief (100-ms) movements of the visual scene were examined for their dependence on viewing distance in 5 monkeys (Macaca mulatta). The horizontal positions of both eyes and the vertical position of one eye were recorded using the electromagnetic search-coil technique. Accommodation was monitored in selected experiments by use of an infrared optometer. Test patterns (random dots) were back-projected onto a translucent tangent screen facing the animal. Six viewing distances were used (range, 20-150 cm), the size and speed of the image on the screen being adjusted for each so as to preserve a constant retinal image. 2. Response measures based on the amplitude of the first peak in the eye acceleration profile or the eye velocity achieved at specific times all indicated that ocular following responses were inversely related to viewing distance, the relationship being linear for the earliest measures. On average, the sensitivity to viewing distance was comparable with that reported for the translational vestibuloocular reflex (TVOR) in the preceding paper: as viewing distance increased from 20 cm, ocular following decremented at a mean rate (+/- SD) of 17 +/- 3% per m-1, while the TVOR decremented at a mean rate (+/- SD) of 18 +/- 1% per m-1. 3. Ocular following responses showed the postsaccadic enhancement described by Kawano and Miles regardless of viewing distance. To a first approximation, the effects of postsaccadic enhancement and viewing distance summed linearly. 4. The dependence of ocular following on speed showed the progressive saturation previously described by Miles et al. at all viewing distances, the peak eye velocity achieved being inversely related to the viewing distance, indicating that the saturation must originate upstream of the dependence on viewing distance. Under normal viewing conditions, this speed saturation will tend to offset the dependence on viewing distance because the retinal slip speeds experienced by the moving observer will tend to vary inversely with viewing distance, resulting in greater saturation with nearer viewing. 5. Wedge prisms were used to dissociate vergence and accommodation and indicated that ocular following responses were sensitive to selective increases in either vergence (base-out prism with the screen at 100 cm) or accommodation (base-in prism with the screen at 20 cm). However, as with the TVOR, the magnitude of the effects showed considerable variability from one animal to another and, in some particular animals, from one direction to another.(ABSTRACT TRUNCATED AT 400 WORDS)
Potassium current kinetics in bursting secretory neurons: effects of intracellular calcium
Authors: Martinez J. J. , Onetti C. G. , Garcia E. , Hernandez S.
Published: December 2017

1. The kinetics of delayed rectifier (IK) and transient potassium (IA) currents and their modification by intracellular calcium ions in bursting X-organ neurons of the crayfish were studied with whole-cell patch-clamp technique. Activation and inactivation kinetics were analyzed according to Hodgkin and Huxley-type equations. 2. IK activates with sigmoidal time course at membrane potentials more positive than -38.4 +/- 3.5 (SD) mV (n = 5), and does not inactivate. The conductance through delayed rectifier channels (gK) is described by the equation gK = GKn2. 3. IA activates at membrane potentials close to the resting potential (-52.2 +/- 4.3 mV, n = 5) and, after a peak, inactivates completely. The conductance through A-channels (gA) can be described by the product of independent activation and inactivation parameters: gA = GAa4b. Both activation and inactivation processes are voltage and time dependent. 4. Steady-state activation of IK and IA as well as inactivation of IA can be described by Boltzmann distributions for single particles with valencies of 2.55 +/- 0.01 (n = 5), 1.60 +/- 0.25 (n = 5), and 3.87 +/- 0.39 (n = 3), respectively. 5. Increasing [Ca2+]i, we observed the following: 1) a considerable inactivation of IK during test pulses, 2) an increase of maximal conductance for IA, 3) a reduction of the valency of IA inactivation gating particle (from 3.87 to 2.27), 4) a reduction of the inactivation time constants of IA, and 5) a shift of the inactivation steady-state curve to more positive membrane potentials.(ABSTRACT TRUNCATED AT 250 WORDS)
Control of orienting gaze shifts by the tectoreticulospinal system in the head-free cat. I. Identification, localization, and effects of behavior on sensory responses
Authors: Guitton D. , Munoz D. P.
Published: December 2017

1. The input-output connectivity, in cat, of tectoreticular (TRNs) and tectoreticulospinal (TRSNs) neurons [together called TR(S)Ns] suggests a role for these cells in the sensorimotor transformations necessary for controlling orienting behavior. Multimodal sensory information converges directly onto these tectal neurons, and they project to several brain stem and spinal cord centers involved in the control of eye- and head-orienting movements. In this and the following two papers, we describe the sensorimotor discharges of antidromically identified TR(S)Ns. Here we describe the process of localizing and identifying them, characteristics of both their antidromic and sensory responses, and effects of behavioral context on these responses. 2. In 13 alert, chronically prepared cats, a total of 293 neurons were antidromically identified from either the predorsal bundle (PDB) immediately rostral to abducens nucleus or the ventromedial funiculus of the spinal cord at the level of the first cervical vertebra (C1). The cell bodies of all identified TR(S)Ns were confined to the intermediate and deep laminae of the superior colliculus (SC). The antidromic nature of the action potential evoked by stimulating either the PDB or C1 was verified by the use of a number of established criteria, including collision testing. 3. The mean antidromic latency from the PDB (TRNs + TRSNs) was 0.84 +/- 0.59 (SD) ms (n = 217). The conduction velocities of all cells activated by PDB stimulation ranged from 4 to 40 m/s. The mean latency from C1 (TRSNs) was 1.03 +/- 0.52 ms (SD) (n = 64), whereas conduction velocities ranged from 14 to 80 m/s. 4. One hundred thirty-eight TR(S)Ns were studied long enough to yield significant data regarding their involvement in visuomotor-orienting behavior. Ninety-eight percent (130/133) of the TR(S)Ns tested for visual responses could be induced to discharge action potentials in response to some form of visual stimulation. The other three neurons remained silent, even in response to the most provocative stimuli. These silent neurons nevertheless were shown to be depolarized by visual stimuli. TR(S)Ns were occasionally tested for auditory and somatosensory responses and some were multimodal. 5. TR(S)Ns had visual receptive fields that conformed to the retinotopic map of the visual field that is represented within the SC. Cells found in the lateral SC had receptive fields located in the lower visual field, whereas neurons that were situated medially had receptive fields in the upper visual field. Cells found in the rostral SC had small fields that included a representation of the area centralis.(ABSTRACT TRUNCATED AT 400 WORDS)
Control of orienting gaze shifts by the tectoreticulospinal system in the head-free cat. III. Spatiotemporal characteristics of phasic motor discharges
Authors: Munoz D. P. , Guitton D. , Pelisson D.
Published: December 2017

1. In this paper we describe the movement-related discharges of tectoreticular and tectoreticulospinal neurons [together called TR (S) Ns] that were recorded in the superior colliculus (SC) of alert cats trained to generate orienting movements in various behavioral situations; the cats' heads were either completely unrestrained (head free) or immobilized (head fixed). TR (S) Ns are organized into a retinotopically coded motor map. These cells can be divided into two groups, fixation TR (S) Ns [f TR (S) Ns] and orientation TR (S) Ns [oTR(S)Ns], depending on whether they are located, respectively, within or outside the zero (or area centralis) representation of the motor map in the rostral SC. 2. oTR(S)Ns discharged phasic motor bursts immediately before the onset of gaze shifts in both the head-free and head-fixed conditions. Ninety-five percent of the oTR(S)Ns tested (62/65) increased their rate of discharge before a visually triggered gaze shift, the amplitude and direction of which matched the cell's preferred movement vector. For movements along the optimal direction, each cell produced a burst discharge for gaze shifts of all amplitudes equal to or greater than the optimum. Hence, oTR(S)Ns had no distal limit to their movement fields. The timing of the burst relative to the onset of the gaze shift, however, depended on gaze shift amplitude: each TR(S)N reached its peak discharge when the instantaneous position of the visual axis relative to the target (i.e., instantaneous gaze motor error) matched the cell's optimal vector, regardless of the overall amplitude of the movement. 3. The intensity of the movement-related burst discharge depended on the behavioral context. For the same vector, the movement-related increase in firing was greatest for visually triggered movements and less pronounced when the cat oriented to a predicted target, a condition in which only 76% of the cells tested (35/46) increased their discharge rate. The weakest movement-related discharges were associated with spontaneous gaze shifts. 4. For some oTR(S)Ns, the average firing frequency in the movement-related burst was correlated to the peak velocity of the movement trajectory in both head-fixed and head-free conditions. Typically, when the head was unrestrained, the correlation to peak gaze velocity was better than that to either peak eye or head velocity alone. 5. Gaze shifts triggered by a high-frequency train of collicular microstimulation had greater peak velocities than comparable amplitude movements elicited by a low-frequency train of stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)
Somatosensory responses in the cat motor cortex. I. Identification and course of an afferent pathway
Authors: Padel Y. , Relova J. L.
Published: December 2017

1. The main aim of the present series of experiments was to demonstrate with electrophysiological methods that the spinothalamocortical system may send somesthetic information to the pyramidal and corticospinal tract cells in the motor cortex of the cat. 2. Experiments were carried out on acutely prepared cats anesthetized with alpha-chloralose. Extra- and intracellular recordings were made from the cells located in the pericruciate motor cortex (the lateral portion of area 4 gamma). They were identified by their antidromic responses to pyramidal stimulation and/or stimulation of the dorsolateral funiculus of the spinal cord. The animals were subjected to a set of nervous tissue lesions to prevent any transit of extereoceptive information to the motor cortex via the cerebellum and the somatosensory cortex. A lesion of the dorsal part of the spinal cord was also made, leaving intact only the afferent inflow ascending in the spinal ventral half, i.e., the spinothalamic system. 3. In this cat preparation it was observed that both electrical and natural stimulation of the limbs still efficiently activated the motor cortical efferent cells. 4. The pathway was mapped by applying microstimulation along its whole course in the spinal cord and brain stem. Stimulation of the primary afferent fibers running in the dorsal columns caudally to the spinal cord lesion produced activation and/or inhibition of the cortical cells. The existence of these responses may be attributable to the existence of collaterals from primary afferent fibers located in the dorsal columns, which activate the spinothalamic tract cells either mono- or polysynaptically. In the brain stem the fibers join the medial lemniscus. 5. In view of the short latency of the responses (mean latency 10.5 ms from the spinal cord) it is suggested that this component of the spinothalamic system may play an important role in the sensory regulation of ongoing movements.
Excitation of cutaneous sensory nerve endings in the rat by 4-aminopyridine and tetraethylammonium
Authors: Kirchhoff C. , Leah J. D. , Jung S. , Reeh P. W.
Published: December 2017

1. The effects of the potassium channel blockers 4-aminopyridine (4-AP) and tetraethylammonium (TEA) on cutaneous sensory nerve endings have been investigated with the use of an in vitro skin-nerve preparation from the rat. 2. Direct application of these compounds to the nerve endings, but not to the axons, induced continuous discharges in most A beta, A delta, and C fibers. There was no relationship between the fibers' responsiveness or the threshold concentration required to induce discharges and either the conduction velocity or sensory properties of the fibers. 3. The rate of induced discharges increased linearly with increasing concentrations of 4-AP. At threshold concentrations of 10(-6)-10(-5) M, low-frequency, irregular discharges developed; but at the highest concentration of 10(-3) M, a characteristic doublet or bursting discharges usually emerged. 4. During and after the induced discharges there did not appear to be an alteration in the sensitivity of the sensory nerve endings to mechanical or thermal stimuli. 5. It is concluded that the induced activity arises from an action of these potassium channel blockers at or near the action potential generator region at the nerve endings.
Patch-clamp study of postnatal development of CA1 neurons in rat hippocampal slices: membrane excitability and K+ currents
Authors: Spigelman I. , Zhang L. , Carlen P. L.
Published: December 2017

1. The postnatal development of membrane properties and outward K+ currents in CA1 neurons in rat hippocampal slices was studied with the use of whole-cell patch-clamp techniques. 2. Neurons at all postnatal ages (2-30 days; P2-30) were capable of generating tetrodotoxin (TTX)-sensitive action potentials in response to intracellular injection of depolarizing current pulses. There was a gradual increase in the amplitude and a decrease in the duration of these action potentials with age. Stable values for spike duration were reached by P15, whereas spike amplitude increased until P20-25. In P2-5 neurons, the duration of action potentials was greatly prolonged by depolarization from the resting membrane potential, indicating a weak spike repolarizing mechanism at depolarized potentials. In contrast, the duration of spikes evoked in P20-30 neurons was not affected by similar changes in the membrane potential. 3. Application of tetraethylammonium (TEA, 10 mM) had no effect on the duration of spikes in P3-5 neurons, whereas application of 4-aminopyridine (4-AP, 2 mM) produced large increases in spike duration. In contrast, the duration of spikes in P26 neurons was greatly increased after TEA application, whereas 4-AP had smaller effects on spike duration in these neurons. 4. The input resistance and membrane time constant decreased with age from P2 to P15. The values for both parameters were considerably greater than those reported with conventional intracellular recording electrodes in the immature hippocampus. The resting membrane potential became more hyperpolarized with age. When the recording pipettes contained KCl (140 mM), the resting potential of P3-4 neurons was 34 mV depolarized compared with resting potentials observed with potassium gluconate-filled pipettes. Only a 13-mV change in resting potential was observed during similar comparisons in P27-28 neurons. 5. Outward currents activated by depolarization were examined with the use of voltage-clamp techniques in P2-30 neurons. In P2-5 cells, a small, slowly inactivating outward current was evoked with depolarizing commands from holding potentials near -50 mV. By preceding the depolarizing commands with a hyperpolarizing prepulse, an additional early transient outward current was evoked. The sustained and transient outward currents were separated by their kinetic properties and their sensitivity to cobalt (Co2+), TEA, and 4-AP.(ABSTRACT TRUNCATED AT 400 WORDS)
Constraints on arm position when pointing in three dimensions: Donders' law and the Fick gimbal strategy
Authors: Hore J. , Watts S. , Vilis T.
Published: December 2017

1. While making saccades between targets with the head stationary, eye positions are constrained to two of the possible three degrees of freedom. Classically this constraint has been described by Donders' and Listing's laws. The objective was to determine whether these laws also apply for the straight arm when pointing between different targets. Thus we determined whether the arm adopts only one angular position for every pointing direction (Donders' law) and whether these positions can be described by rotations from a reference position about axes that lie in a plane (Listing's law). 2. The angular positions (orientations) of the arm in three-dimensional space were studied as subjects pointed with a straight arm at different targets. Arm position was measured with the search coil technique by means of coils attached to the back of the hand. Pointing was studied over a range of +/- 45 degrees in all directions from a central target located 45 degrees to the right of the straight-ahead position. 3. The positions of the arm in space were described by quaternion vectors, i.e., a particular position was described in terms of the axis and amplitude of a rotation from a reference position to that position. Using this description, it was found that the straight arm adopted a similar orientation (standard deviations ranged from 2.8 to 4.8 degrees) when pointing at a particular target irrespective of which target from which it had moved. 4. The angular position vectors for arm positions associated with relatively small movements (e.g., less than +/- 30 degrees) lay in a flat surface with minimal torsion. At first sight, this surface appeared to be similar to Listing's plane of the eye. However, for positions associated with larger movements (e.g., +/- 45 degrees) it became apparent that, unlike the eye, the surface deviated from one obeying Listing's law, i.e., it was twisted and showed torsion like that produced by rotations around the horizontal and vertical axes of a Fick gimbal. (The characteristic of a Fick gimbal is that the vertical axis is fixed, whereas the horizontal axis moves with the gimbal.) 5. Although there were differences between subjects, all showed a twisted position vector surface. The twist was always in the same direction, and it was always less than that of a Fick gimbal. 6. This position vector surface had a similar shape whether the arm was stationary or was moving between targets, whether subjects pointed with or without vision, and whether the pointing arm had moved between targets or from a bent-elbow position on the lap.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of inferior temporal neurons in visual memory. II. Multiplying temporal waveforms related to vision and memory
Authors: Eskandar E. N. , Optican L. M. , Richmond B. J.
Published: December 2017

1. In the companion paper we reported on the activity of neurons in the inferior temporal (IT) cortex during a sequential pattern matching task. In this task a sample stimulus was followed by a test stimulus that was either a match or a nonmatch. Many of the neurons encoded information about the patterns of both current and previous stimuli in the temporal modulation of their responses. 2. A simple information processing model of visual memory can be formed with just four steps: 1) encode the current stimulus; 2) recall the code of a remembered stimulus; 3) compare the two codes; 4) and decide whether they are similar or different. The analysis presented in the first paper suggested that some IT neurons were performing the comparison step of visual memory. 3. We propose that IT neurons participate in the comparison of temporal waveforms related to vision and memory by multiplying them together. This product could form the basis of a crosscorrelation-based comparison. 4. We tested our hypothesis by fitting a simple multiplicative model to data from IT neurons. The model generated waveforms in separate memory and visual channels. The waveforms arising from the two channels were then multiplied on a point by point basis to yield the output waveform. The model was fitted to the actual neuronal data by a gradient descent method to find the best fit waveforms that also had the lowest total energy. 5. The multiplicative model fit the neuronal responses quite well. The multiplicative model made consistently better predictions of the actual response waveforms than did an additive model. Furthermore, the fit was better when the actual relationship between the responses and the sample and test stimuli were preserved than when that relationship was randomized. 6. We infer from the superior fit of the multiplicative model that IT neurons are multiplying temporally modulated waveforms arising from separate visual and memory systems in the comparison step of visual memory.
Endogenous nitric oxide required for an integrative respiratory function in the cat brain
Authors: Ling L. , Karius D. R. , Fiscus R. R. , Speck D. F.
Published: December 2017

1. The involvement of nitric oxide (NO) in the respiratory function of the pons was examined by microinjecting NO synthase-related drugs into discrete regions of the pontine respiratory group (PRG) in decerebrate and decerebellate cats. 2. Microinjection of N omega-nitro-L-arginine (L-NNA, inhibitor of NO synthase), but not D-NNA (the inactive enantiomer), significantly prolonged the duration of inspiration in all 10 cats when lung inflation was withheld. 3. The prolongation of inspiration produced by L-NNA was partially reversed in three cats by microinjections of L-arginine (NO synthase substrate) at the same sites. 4. We conclude that endogenous production of NO from L-arginine in the PRG region is involved in the normal function of the pontine pneumotaxic mechanism. These findings provide the first conclusive evidence that endogenous NO formation is involved in the mechanisms associated with respiratory rhythm generation.
Membrane currents evoked by afferent fiber stimulation in rat piriform cortex. II. Analysis with a system model
Authors: Ketchum K. L. , Haberly L. B.
Published: December 2017

1. The detailed visualization of membrane currents over time and depth provided by current source-density (CSD) analysis was used as the basis for development of a system model that reproduces the response of piriform cortex to afferent fiber stimulation. This model has allowed the testing and substantial revision of previous hypotheses concerning the sequence of neuronal events underlying this response, has enabled net membrane currents visualized by CSD analysis to be separated into active and passive components, and has generated predictions for important axonal and synaptic parameters as well as for the behavior of piriform cortex as a system. 2. The model was developed in three steps. Activity in excitatory fiber systems was first represented with continuous distributions. The “population conductances” due to the activation of excitatory fiber systems were then computed from the distribution of action-potential arrival times and the conductance waveform for excitatory synapses. Finally, these temporally dispersed excitatory conductances and locally mediated inhibitory conductances were introduced at appropriate locations on a compartmentalized cable that simulated the passive response of the pyramidal cell population. 3. After the simulation of membrane currents at one site, all parameters in the model were fixed so that it could be used to predict the variation in the time course of membrane currents at additional recording sites; comparison with the results of CSD analysis at these sites provided the primary validation of the model. Additional validation included the simulation of membrane potentials derived by intracellular recording, including the effects of manipulating somatic potential with current injection. 4. Several conclusions have emerged from the mathematical description of activity in fiber systems. Propagation of activity in both afferent and association (corticocortical) fiber systems is “dispersive” as a result of a wide spectrum of axon conduction velocities. The characteristically different time courses of afferent and association fiber-mediated responses are largely determined by the focal, shock-evoked origin of the volley in afferent fibers as opposed to the spatially distributed disynaptic origin of activity in association fibers. Conduction velocity distributions for afferent and association fiber systems are skewed and can be approximated with lognormal distributions. 5. General solutions, which relate an arbitrary conduction velocity distribution to arrival time and spatial distributions of action potentials, were used to generate specific solutions describing the effects of dispersive propagation.(ABSTRACT TRUNCATED AT 400 WORDS)