bluuebunny/crossref_metadata_2025 huggingface dataset:
Lobster stomatogastric neurons in primary culture. I. Basic characteristics
Authors: Panchin Y. V. , Arshavsky Y. I. , Selverston A. , Cleland T. A.
Published: December 2017

1. A method for the isolation of stomatogastric neurons with neuropilar processes and an axon < or = 2 mm long is described. Isolated neurons adhered to an uncoated plastic surface and demonstrated neurite outgrowth for > or = 7-10 days in a simple medium (salt-adjusted Leibovitz-15). Neurite outgrowth started immediately after plating and was maximal during the first 2-3 days. The electrical activity of neurons and their responses to bath application of pilocarpine were studied between 2 and 10 days after plating. 2. Identified neurons [pyloric dilator (PD), pyloric (PY), and lateral pyloric (LP) neurons from the pyloric pattern generator as well as gastric mill (GM) and lateral posterior gastric (LPG) neurons from the gastric mill pattern generator], isolated with neuropilar processes and axons, behaved in general like corresponding neurons in the isolated stomatogastric ganglion (STG). PD neurons were tonically active or silent in culture; pilocarpine caused them to begin rhythmic activity, which at particular levels of imposed polarization was similar to the pyloric rhythm in vitro. PY and LP neurons were silent. Pilocarpine produced some rhythmicity in the PY neuron, whereas in LP neurons it decreased the firing threshold to depolarizing current and accentuated postinhibitory rebound. LPG neurons were tonically active. Pilocarpine depolarized the LPG neurons and accelerated their tonic activity; neuron hyperpolarization by current injection led to bursting pacemaker activity that was similar to the gastric rhythm in vitro. GM neurons were silent; pilocarpine did not cause them to generate rhythmic activity but did lower their thresholds to depolarizing current. Simultaneous recordings from the soma and axon under direct visual control demonstrated that the intrasomatic spikes (15-20 mV in amplitude) were attenuated action potentials generated in the axon. 3. Neurons isolated with short primary neurites, including those without any noticeable primary neurite (in contrast to neurons isolated with longer neuropilar processes and axons), never generated any kind of electrical activity immediately after extraction from the STG. After 2 days in culture, these "short-neurite" neurons became capable of generating different types of electrical activity (e.g., fast spikes with amplitudes of < or = 40-45 mV, plateau potentials, bursting potentials, etc.). The capability of isolated somata to generate electrical activity did not depend on whether or not the cell had adhered to the substrate and demonstrated neurite outgrowth.(ABSTRACT TRUNCATED AT 400 WORDS)
Modulation of identified stomatogastric ganglion neurons in primary cell culture
Authors: Turrigiano G. G. , Marder E.
Published: December 2017

1. We studied the properties of identified stomatogastric ganglion (STG) neurons grown in complete isolation in primary cell culture. 2. STG neurons isolated with a short piece of primary neurite adhered to the culture dishes and extended neurites. Outgrowth was apparent within several hours, and continued for < or = 5 days. 3. After 1 day in culture, most STG neurons were not capable of producing action potentials or oscillations. After 3-5 days in culture, most STG neurons regained the ability to fire action potentials, and some became endogenous bursters. Neurons in culture 3-5 days possessed many of the physiological properties of STG neurons in situ, including postinhibitory rebound, a hyperpolarization-activated depolarizing voltage sag, and the ability to burst in the presence of the potassium channel blocker tetraethyl-ammonium. 4. Identified cultured neurons responded appropriately to a variety of neuromodulators, including the monoamines dopamine and octopamine, the muscarinic agonist pilocarpine, and the peptide proctolin. These data suggest that the maintenance of receptor expression in fully differentiated STG neurons is not affected by isolation from all synaptic and modulatory influences. 5. In contrast to the other modulators tested, the effects of serotonin on cultured neurons differed from those reported in situ. Two cell types that are reported to be hyperpolarized by serotonin in situ, the lateral pyloric and pyloric neurons, were depolarized by serotonin in culture.
Motor cortical activity during drawing movements: population representation during sinusoid tracing
Authors: Schwartz A. B.
Published: December 2017

1. Monkeys were trained to trace sinusoids with their index fingers on a planar surface. During this task, both the direction and speed of movement varied continuously. Activity of individual units in the precentral gyrus contralateral to the moving arm was recorded as the task was performed. These cells responded to passive movement of the shoulder and/or elbow. The relation between discharge rate and movement direction for these individual cells could be described with a cosine tuning function. 2. Data recorded as the sinusoid was traced were divided into 100 bins as each cell was studied during the experiment. In each bin, the activity of a particular cell was represented by a vector. The vector ("cell vector") pointed in the direction of finger movement that corresponded to the highest rate of neuronal discharge. This direction, referred to as the preferred direction, corresponded to the peak of the cosine tuning function. The direction of the vector was constant between bins, but the magnitude of this cell's vector was a function of the instantaneous discharge rate. 3. This cell vector is a hypothetical contribution of a single cell to the population response comprised of 554 similarly derived vectors from different cells. The population response was represented as the vector that resulted from forming the sum of the vector contributions from the individual cells. A separate calculation was made for each bin, resulting in 100 population vectors for each sinusoid. 4. Within a given time series of population vectors, their lengths and directions varied in a consistent relation to the tangential velocity of the drawing movement.(ABSTRACT TRUNCATED AT 250 WORDS)
Representation of the urinary bladder in the lateral thalamus of the cat
Authors: Bruggemann J. , Vahle-Hinz C. , Kniffki K. D.
Published: December 2017

1. In alpha-chloralose-anesthetized cats the region surrounding the ventral posterolateral nucleus (VPL) of the thalamus was investigated to locate foci with input from the urinary bladder stimulated by application of intravesical pressure. The locations of the recording sites were verified in Nissl-stained histological sections with reference to electrolytic lesions. 2. Of the 23 visceroceptive thalamic neurons identified, 4 (17%) were located in the periphery of the VPL (VPLp) and 19 (83%) in the lateral and dorsal aspects of the posterior complex (POl and POd, respectively) adjoining VPLp. 3. The neurons responded to noxious intensities of intravesical pressure in the range of 50-100 mmHg. Excitatory responses were elicited in 8 (35%) neurons, "inhibitory" responses in 13 (57%) neurons, and 2 (9%) neurons responded with an increase and a decrease of their discharge to subsequent stimuli. 4. Of the 22 visceroceptive thalamic neurons tested for this parameter, 73% had low-threshold cutaneous receptive fields (RFs). These were located in the region of the lower back, the hip, the thigh, and the proximal tail (12 PO neurons), or covered the entire postcranial contralateral part of the body (3 PO neurons). For only one of the VPLp neurons, a somatic RF was found and this was located on the distal tail. The neurons responded to tap stimuli applied at a low repetition rate. None of the 11 neurons tested with noxious pinching of the skin was activated by this kind of stimulus. 5. It is concluded that the cat's lateral thalamic region, around but not within VPL proper, contains neurons that play a role in the processing of information about noxious events in the urinary bladder. A comparison with results from experiments in the monkey indicates differences in the organization of the visceroceptive systems between both species, regarding the thalamic localization of visceroceptive neurons, the occurrence of convergent low-threshold somatic RFs, and the association of excitatory and inhibitory effects of urinary bladder stimulation with the location of somatic RFs.
Fixation cells in monkey superior colliculus. II. Reversible activation and deactivation
Authors: Munoz D. P. , Wurtz R. H.
Published: December 2017

1. We tested the hypothesis that a subset of neurons, which we have referred to as fixation cells, located within the rostral pole of the monkey superior colliculus (SC) controls the generation of saccadic eye movements. We altered the activity of these neurons with either electrical stimulation or GABAergic drugs. 2. An increase in the activity of fixation cells in the rostral SC, induced by a train of low-frequency electrical stimulation, delayed the initiation of saccades. With bilateral stimulation the monkey was able to make saccades only after stimulation ceased. 3. Pulses of stimulation delivered during the saccade produced an interruption of the saccade in midflight. The latency to the onset of this perturbation was as short as 12 ms. 4. Injection of the gamma-aminobutyric acid (GABA) antagonist bicuculline into the rostral pole of the SC, which decreases normal GABA inhibition and increases cell activity, increased the latency of saccades to both visual and remembered targets. 5. Injection of the GABA agonist muscimol into the rostral SC, which increases normal GABA inhibition and decreases activity, reduced the latency for saccades to visual targets. The monkey also had difficulty maintaining visual fixation and suppressing unwanted saccades. 6. After muscimol injections, monkeys frequently made very short-latency saccades forming a peak in the saccade latency histogram at < 100 ms. These saccades are similar to express saccades made by normal monkeys. This finding suggests that the fixation cells in the rostral SC are critical for controlling the frequency of express saccades. 7. These results support the hypothesis that fixation cells in the rostral SC inhibit the generation of saccadic eye movements and that they form part of a system of oculomotor control, that of visual fixation.
Activity-dependent depression of mechanosensory discharge in Aplysia
Authors: Clatworthy A. L. , Walters E. T.
Published: December 2017

1. Inhibition of action potential discharge in Aplysia mechanosensory neurons after noxious stimulation has not been described previously. The present studies investigated depressive effects of prolonged noxious stimulation and repetitive intracellular activation on the number and latency of action potentials evoked by test stimuli applied to the tail or the nerve innervating the tail. Action potential discharge was monitored in the somata of mechanonociceptors in the pleural ganglia. 2. Repeated brief pinches delivered at 5-s intervals to a sensory neuron's receptive field on the tail initially caused intense activation (10-25 spikes recorded in the soma) followed by a progressive decrease or "wind-down" of spike number during subsequent pinches. 3. Repeated application to the tail of noxious shock that caused intense activation of sensory neurons (10-22 spikes during the initial shock) produced progressive wind-down of discharge similar to that produced by repeated tail pinch. However, sensory neurons that showed lower activation (1-9 spikes) to the same shock displayed wind-up of discharge during the 10 shocks. These results suggested that prolonged, intense activation depresses subsequent action potential discharge. 4. Changes in the time required for spikes evoked in the tail to reach the central soma were used as an indicator of changes in the excitability and/or conduction velocity of peripheral branches. Repeated pinch within a sensory neuron's receptive field caused an increase in the latency of discharge elicited by test shocks within the receptive field that lasted > or = 10 min. Repetitive intracellular stimulation of the sensory neuron soma caused a similar increase in latency. 5. Repetitive soma activation decreased the number of spikes evoked 10 s later by a test shock in the sensory neuron's receptive field, indicating that spike activity depresses the initiation and/or conduction of spikes in peripheral branches. Surprisingly, repeated pinch to the receptive field caused no significant change in the number of spikes evoked by the same test shock. This difference suggests that tail pinch produces concomitant facilitatory effects that oppose the depressive effects of intense spike activity. 6. Depressive effects of repeated pinch and repetitive soma activation were expressed in the axon between the receptive field and the CNS. Spikes evoked by brief test shocks delivered to the nerve containing the axon of the recorded sensory neuron showed a transient increase in latency (perhaps due to a decrease in conduction velocity) after either procedure. Repeated pinch, but not repetitive soma activation, also caused an increase in spike threshold in the nerve.(ABSTRACT TRUNCATED AT 400 WORDS)
Detection of magnetic evoked fields associated with synchronous population activities in the transverse CA1 slice of the guinea pig
Authors: Kyuhou S. , Okada Y. C.
Published: December 2017

1. Magnetic evoked fields (MEFs) associated with synchronous population activities in the transverse CA1 of guinea pig (approximately 1.2 mm3) were characterized with a high-resolution superconducting magnetic field detector. 2. Electrical stimulations of the stratum radiatum with a pair of bipolar electrodes produced synchronous population spikes in the field potential and a strong MEF (as much as 3.5 picoteslas 3 mm above tissue) in the presence of 0.05 mM picrotoxin. The MEF's spatial pattern and direction indicated currents in pyramidal cells as its source. Bath application of kynurenic acid extinguished most of the signals, indicating a strong contribution of post-synaptic currents to the field. The kynurenic acid-insensitive component was abolished by tetrodotoxin, indicating the remaining component was neuronal in origin as well. 3. It may be possible to refine our technique to study the genesis of MEG signals--i.e., the relationship between evoked fields and the underlying neuronal currents--in a mammalian CNS structure, since the electrophysiology of the hippocampus is well understood.
Receptive-field maps of correlated discharge between pairs of neurons in the cat's visual cortex
Authors: Ghose G. M. , Ohzawa I. , Freeman R. D.
Published: December 2017

1. To investigate the functional significance of temporally correlated discharge between nearby cells in the visual cortex, we obtained receptive-field maps of correlated discharge for 68 cell pairs in kittens and cats. Discharge from cell pairs was measured by a single extracellular electrode. A reverse correlation procedure was used to relate neural discharge to particular stimuli within a random sequence of briefly flashed bright and dark bars. Bicellular receptive fields (BRFs) were mapped by applying reverse correlation to approximately synchronous discharge from two cells. Unicellular receptive fields (URFs) were simultaneously mapped by separately applying reverse correlation to the discharge of each cell. 2. The receptive fields of the two neurons within each pair were initially studied by varying the orientation and spatial frequency of drifting sinusoidal gratings. After these tests a random sequence of appropriately oriented bars was used to evoke discharge suitable for reverse correlation analysis. For most cell pairs, the temporal pattern or strength of correlated discharge produced by such stimulation is different from that observed with stimulation by sinusoidal gratings. This indicates that visually evoked correlated discharge between nearby cells is stimulus dependent. 3. BRFs were classified according to their pattern of spatial sensitivity into three groups that roughly correspond to the single-cell receptive-field types of the lateral geniculate nucleus (LGN; center-surround) and visual cortex (simple and complex). These classifications were compared with the receptive-field types of the single cells within each pair. LGN-type and simple-type BRFs were only seen for pairs in which at least one of the cells was simple. Conversely, complex-type BRFs were only seen for pairs in which at least one of the cells was complex. 4. Because the reverse correlation procedure can be used to characterize the spatiotemporal receptive-field structure of simple cells, we were able to compare both the spatial and temporal properties associated with the URFs and BRFs of simple cell pairs. The spatiotemporal structure of the BRF of a simple-cell pair can largely be predicted on the basis of the two URFs. Although this prediction suggests the possibility that BRFs are stimulus artifacts, a shuffle procedure, in which multiple repetitions of random sequences were presented, verifies the neural origin of BRFs. BRFs emerge from specific neural pathways and are not simply a consequence of unicellular response preferences. 5. Five measures were derived from the reverse correlation analysis of simple-cell receptive fields: width, duration, optimal spatial and temporal frequency, and optimal velocity.(ABSTRACT TRUNCATED AT 400 WORDS)
Comparative transduction mechanisms of hair cells in the bullfrog utriculus. I. Responses to intracellular current
Authors: Baird R. A.
Published: December 2017

1. Hair cells in whole-mount in vitro preparations of the utricular macula of the bullfrog (Rana catesbeiana) were selected according to their macular location and hair bundle morphology. The voltage responses of selected hair cells to intracellular current steps and sinusoids in the frequency range of 0.5-200 Hz were studied with conventional intracellular recordings. 2. The utricular macula is divided into medial and lateral parts by the striola, a 75- to 100-microns zone that runs for nearly the entire length of the sensory macula near its lateral border. The striola is distinguished from flanking extrastriolar regions by the elevated height of its apical surface and the wider spacing of its hair cells. A line dividing hair cells of opposing polarities, located near the lateral border of the striola, separates it into medial and lateral parts. On average, the striola consists of five to seven medial and two to three lateral rows of hair cells. 3. Utricular hair cells were classified into four types on the basis of hair bundle morphology. Type B cells, the predominant hair cell type in the utricular macula, are small cells with short sterocilia and kinocilia 2-6 times as long as their longest stereocilia. These hair cells were found throughout the extrastriola and, more rarely, in the striolar region. Three other hair cell types were restricted to the striolar region. Type C cells, found primarily in the outer striolar rows, resemble enlarged versions of Type B hair cells. Type F cells have kinocilia approximately equal in length to their longest stereocilia and are restricted to the middle striolar rows. Type E cells, found only in the innermost striolar rows, have short kinocilia with prominent kinociliary bulbs. 4. The resting potential of 99 hair cells was -58.0 +/- 7.6 (SD) mV and did not vary significantly for hair cells in differing macular locations or with differing hair bundle morphology. The RN of hair cells, measured from the voltage response to current steps, varied from 200 to > 2,000 M omega and was not well correlated with cell size. On average, Type B cells had the highest RN, followed by Type F, Type E, and Type C cells. When normalized to their surface area, the membrane resistance of hair cells ranged from < 1,000 to > 10,000 k omega.cm2. The input capacitance of hair cells ranged from < 3 to > 15 pA, corresponding on average to a membrane capacitance of 0.8 +/- 0.2 pA/cm2.(ABSTRACT TRUNCATED AT 400 WORDS)
Positron emission tomographic analysis of cerebral structures activated specifically by repetitive noxious heat stimuli
Authors: Casey K. L. , Minoshima S. , Berger K. L. , Koeppe R. A. , Morrow T. J. , Frey K. A.
Published: December 2017

1. To identify the forebrain and brain stem structures that are active during the perception of acute heat pain in humans, we performed H2 15O positron emission tomographic (PET) analyses of cerebral blood flow (CBF) on nine normal volunteers while they received repetitive noxious (50 degrees C) and innocuous (40 degrees C) 5 s heat pulses to the forearm (average resting temperature of 31.8 degrees C). Each subject rated the subjective intensity of each stimulation series according to a magnitude estimation procedure in which 0 = no heat sensation, 7 = barely painful, and 10 = barely tolerable. 2. Three scans were performed at each temperature. Mean CBF images were created for each experimental condition and oriented onto standardized stereotaxic coordinates. Subtraction images were created between conditions for each subject and averaged across subjects. Volumes of interest (VOI) were chosen, based on a priori hypotheses and the results of previously published PET studies. In addition, a separate statistical summation analysis of individual voxels was performed. Statistical thresholds were established with corrections for multiple comparisons. 3. Significant CBF increases to 50 degrees C stimuli were found in the contralateral thalamus, cingulate cortex, S2 and S1 cortex, and insula. The ipsilateral S2 cortex and thalamus, and the medial dorsal midbrain and cerebellar vermis also showed significant CBF increases. All subjects rated the 50 degrees C stimuli as painful (average subjective rating = 8.9 +/- 0.9 SD) and the 40 degrees C stimuli as warm, but not painful (average subjective rating = 2.1 +/- 1.0).(ABSTRACT TRUNCATED AT 250 WORDS)
Differential effects of muscimol microinjection into dorsal and ventral aspects of the premotor cortex of monkeys
Authors: Kurata K. , Hoffman D. S.
Published: December 2017

1. A gamma aminobutyric acid (GABAA) receptor agonist, muscimol (Sigma, 5 micrograms/microliters solution), and a GABAB receptor agonist and antagonist, baclofen and phaclofen, respectively, were injected (1.0 microliter) into the dorsal and ventral aspects of the premotor cortex (PM) of two Japanese monkeys (Macaca fuscata), while they were performing a motor task that required wrist flexion or extension to a target. The correct movement was instructed by either 1) a conditional color cue [green or red light emitting diodes (LED)] equidistant from the targets or 2) a directional cue toward extension or flexion (right or left LED). When the green or right LED was illuminated, extension was to be performed. When the red or left LED was illuminated, flexion was required. The movement was triggered by a visual stimulus either simultaneously with the instruction stimulus or after a variable delay. 2. Before drug injection, single-unit recordings were made to select injection sites 1) in the dorsal aspect of the PM (PMd) around the superior precentral sulcus where typical set-related activity was frequently recorded and 2) in the ventral aspect of the PM (PMv) immediately caudal to the genu of the arcuate sulcus where movement-related neurons were densely located. 3. Behavioral deficits were observed primarily at the time muscimol, but not baclofen or phaclofen, was injected. Furthermore, muscimol effects were short-lasting: deficits were most frequently observed during the 10-min injection period but seldom after completion of injection. 4. When muscimol was injected into the PMd, there was an increase in the number of direction errors primarily when the conditional cues were presented. The initiated movements were similar in amplitude and velocity to the preinjection behavior. In contrast, when muscimol was injected into the PMv, many of the initiated movements showed smaller amplitudes and slower velocities, but few direction errors were made. 5. These results suggest that the PMd and PMv play differential roles in motor control: the PMd is more important than PMv in conditional motor behavior and plays a role in the preparation for forthcoming movements. In contrast, the PMv is more specialized for a role in the execution of visually guided movements.
Physiological properties of anatomically identified axo-axonic cells in the rat hippocampus
Authors: Buhl E. H. , Han Z. S. , Lorinczi Z. , Stezhka V. V. , Karnup S. V. , Somogyi P.
Published: December 2017

1. The properties of a well-defined type of GABAergic local circuit neuron, the axo-axonic cell (n = 17), were investigated in rat hippocampal slice preparations. During intracellular recording we injected axo-axonic cells with biocytin and subsequently identified them with correlated light and electron microscopy. Employing an immunogold-silver intensification technique we showed that one of the physiologically characterized cells was immunoreactive for gamma-aminobutyric acid (GABA). 2. Axo-axonic cells were encountered in the dentate gyrus (n = 5) as well as subfields CA3 (n = 2) and CA1 (n = 10). They generally had smooth, beaded dendrites that extended throughout all hippocampal layers. Their axons ramified densely in the cell body layers and in the subjacent stratum oriens or hilus, respectively. Tested with electron microscopy, labeled terminals (n = 53) established synapses exclusively with the axon initial segment of principal cells in strata oriens and pyramidale and rarely in lower radiatum. Within a 400-microns slice a single CA1 axo-axonic cell was estimated to be in synaptic contact with 686 pyramidal cells. 3. Axo-axonic cells (n = 14) had a mean resting membrane potential of -65.1 mV, an average input resistance of 73.9 M omega, and a mean time constant of 7.7 ms. Action potentials were of short duration (389-microseconds width at half-amplitude) and had a mean amplitude of 64.1 mV. 4. Nine of 10 tested cells showed a varying degree of spike frequency adaptation in response to depolarizing current injection. Current-evoked action potentials were usually curtailed by a deep (10.2 mV) short-latency afterhyperpolarization (AHP) with a mean duration of 28.1 ms. 5. Cells with strong spike frequency accommodation (n = 5) had a characteristic firing pattern with numerous spike doublets. These appeared to be triggered by an underlying depolarizing afterpotential. In the same cells, prolonged bursts of action potentials were followed by a prominent long-duration AHP with a mean time constant of 1.15 s. 6. Axo-axonic cells responded to the stimulation of afferent pathways with short-latency excitatory postsynaptic potentials (EPSPs) or at higher stimulation intensity with up to three action potentials. Axo-axonic cells in the dentate gyrus could be activated by stimulating the CA3 area as well as the perforant path, whereas in the CA1 area responses were elicited after shocks to the perforant path, Schaffer collaterals, and the stratum oriens-alveus border. 7. In the CA1 area the EPSP amplitude increased in response to membrane hyperpolarization.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of chronic spinalization on ankle extensor motoneurons. I. Composite monosynaptic Ia EPSPs in four motoneuron pools
Authors: Hochman S. , McCrea D. A.
Published: December 2017

1. We examined the effects of 6-wk chronic spinalization at the L1-L2 level on composite monosynaptic Ia excitatory postsynaptic potentials (EPSPs) recorded in medial gastrocnemius (MG), lateral gastrocnemius (LG), soleus (SOL), and plantaris (PL) motoneurons. Amplitudes, rise times, and half-widths of composite monosynaptic Ia EPSPs evoked by low-strength electrical stimulation of peripheral nerves were measured in barbiturate-anesthetized cats and compared between unlesioned and chronic spinal preparations. 2. The mean amplitude of homonymous composite Ia EPSPs evoked by 1.2 times threshold (1.2T) stimulation and recorded in all four ankle extensor motoneuron pools increased 26% in chronic spinal animals compared with unlesioned controls. There was also an increased incidence of large-amplitude, short-rise time EPSPs. When the same data were separated according to individual motoneuron species, homonymous EPSP amplitudes in MG motoneurons were found to be unchanged. EPSPs recorded in LG motoneurons and evoked by stimulation of the combined LG and SOL nerve were increased by 46%. Mean EPSP amplitudes recorded in both SOL and PL motoneurons were larger after spinalization but statistical significance was only achieved when values from SOL and PL were combined to produce a larger sample size. 3. In LG motoneurons from chronic spinal animals, all EPSPs evoked by 1.2T stimulation of the LGS nerve were > or = 0.5 mV in amplitude. In unlesioned preparations, one fourth of the LG cells had EPSPs that were < or = 0.2 mV. 4. The mean amplitude of heteronymous EPSPs evoked by 2T stimulation of LGS and MG nerves and recorded in MG and LG motoneurons, respectively, doubled in size after chronic spinalization. Because homonymous EPSP amplitudes were unchanged in MG motoneurons, synaptic mechanisms and not passive membrane properties are likely responsible for increased heteronymous EPSP amplitudes in MG. 5. The mean 10-90% rise time of homonymous composite Ia EPSPs in pooled data from all motoneurons decreased 21% in 6-wk chronic spinal animals. Unlike EPSP amplitude, significant rise time decreases were found in all four motoneuron pools. Compared with the other motoneuron species, the mean homonymous rise time recorded in MG motoneurons was shortest and decreased the least in chronic spinal animals. Rise times of heteronymous Ia EPSPs in MG and LG motoneurons also decreased. The maximum rate of rise of homonymous EPSPs increased in all four motoneuron species. 6. The mean half-widths of Ia composite EPSPs decreased in 6-wk spinalized preparations in all motoneuron species.(ABSTRACT TRUNCATED AT 400 WORDS)
Ascorbic acid, but not glutathione, is taken up by brain slices and preserves cell morphology
Authors: Rice M. E. , Perez-Pinzon M. A. , Lee E. J.
Published: December 2017

1. We have determined the ascorbic acid (ascorbate) and glutathione (GSH) content of cortical and hippocampal slices from rat brain after prolonged (6h) incubation and have correlated these levels with the histological quality of the slices. Ascorbate and GSH levels in control and sliced tissue were determined by high performance liquid chromatography (HPLC) with electrochemical detection. Cell morphology of incubated slices was compared with that of intact tissue in cresyl violet stained tissue sections. 2. Roughly 70% of tissue ascorbate and GSH was lost from slices during incubation in vitro. Normal in vivo levels of ascorbate (2-3 mumol g-1 tissue wet weight) could be maintained by including 200-400 microM ascorbate (typical extracellular concentration) in the incubation media. By contrast, the loss of GSH could not be prevented by incubation with GSH. 3. The morphology of cells in hippocampal slices incubated under conditions that maintained ascorbate content and compartmentalization were similar to those of intact tissue. Ascorbate protected pyramidal cells in CA1 and CA3 regions of the hippocampus from the degeneration that was seen in slices incubated in ascorbate-free media. 4. These data suggest that loss of endogenous antioxidants may be a major factor in neuronal loss in vitro and support the notion that ascorbate is an endogenous neuroprotective agent.
Broad-tuned chromatic inputs to color-selective neurons in the monkey visual cortex
Authors: Sato H. , Katsuyama N. , Tamura H. , Hata Y. , Tsumoto T.
Published: December 2017

1. Input mechanisms of 21 color-selective cells in cytochrome oxidase-rich blobs in layer II/III of the anesthetized and paralyzed monkey primary visual cortex were studied by an iontophoretic administration of the GABAergic receptor antagonist bicuculline methiodide (BMI). 2. Color-selective blob cells become responsive to originally nonresponsive colors of stimuli or brightness contrast stimuli during removal of intracortical inhibition. 3. The magnitudes of the cells' responses to color stimuli during BMI administration were larger than the expected value of response calculated from the previously reported color tuning of color-selective geniculate cells and emission spectra of color stimulus. 4. These results suggest that color-selective blob cells receive a convergence of different types of chromatic inputs and that intracortical inhibition confers selectivity for a given color on them.
Frequency organization of delay-sensitive neurons in the auditory cortex of the FM bat, Myotis lucifugus
Authors: Paschal W. G. , Wong D.
Published: December 2017

1. The little brown bat, Myotis lucifugus, employs biosonar pulses containing broadband frequency -modulated (FM) sounds of only one harmonic during the initial phases of echolocation. Neurons throughout the auditory cortex exhibit delay-dependent facilitation to artificial pulses and echoes at particular echo delays. Extracellular unit recordings of these delay-sensitive neurons determined the essential frequency components in the sound pair and their relative timing for evoking maximum facilitation. 2. The entire 60-kHz sweep of both the simulated pulse and echo were divided into four equal spectral quarters (Ist, IInd, IIIrd, and IVth), each linearly sweeping 15 kHz downward in 1 ms, to determine the spectral parts essential for maximal facilitation. Maximal facilitation was evoked equally by pulse-echo pairs in which the sound components consisted of either the entire 60-kHz FM sweeps or only the essential quarters. Most neurons required the IVth quarter of the pulse and the echo for delay sensitivity. This is consistent with the hypothesis that the essential quarters swept excitatory frequencies just above inhibitory frequencies. 3. The spectral and temporal contributions to delay sensitivity were examined independently. The spectral content for each spectral quarter of echo was varied in echo delay, and the sound-pair responses were compared. Maximal facilitation in individual delay-sensitive neurons required both a specific part of the echo spectrum and a specific echo delay. 4. The FM sweeps of the essential pulse and echo quarters were further narrowed to their minimum bandwidth, and the essential pulse frequencies (EPFs) and essential echo frequencies (EEFs) were determined. Both the EPFs and EEFs averaged approximately 8 kHz in FM bandwidth and represented different spectral parts of the echolocation pulse emitted by this FM bat. All neurons showed delay sensitivity to search stimuli in which pulse-echo stimuli consisted of 15-kHz FM pairs. 5. Delay sensitivity in virtually all neurons required pulse and echo components whose essential frequencies differed. However, some spectral overlap was found between the pulse and echo in 39% of these neurons. The majority of neurons (81%) required a pulse and echo in which their mean frequencies differed by>or = 16 kHz. This includes neurons with pulse and echo overlapping spectrally and those with sound components showing no overlap but separated by a relatively small frequency range. 6. The facilitative frequency-tuning curves of individual neurons were measured with their essential pulse and echo frequencies.(ABSTRACT TRUNCATED AT 400 WORDS)
OFF response transformations in the whisker/barrel system
Authors: Kyriazi H. T. , Carvell G. E. , Simons D. J.
Published: December 2017

1. Previous studies have demonstrated marked differences in the relative sizes of ON and OFF responses of neurons in the whisker/barrel system. In particular, OFF responses are unexpectedly large in thalamic neurons. Extracellular unit recordings were used to examine whether varying the time between stimulus onset and offset differently affects OFF responses of neurons in the trigeminal ganglion, ventrobasal thalamus, and somatosensory cortical layer IV. Controlled whisker stimuli were used to deflect individual vibrissal hairs in different directions. We hypothesized that, in part because of the gradual waning of central inhibition evoked by stimulus onset, OFF responses of thalamic and cortical neurons but not trigeminal ganglion cells would increase in size with longer duration stimuli, with relative changes being greatest in the cortex. 2. OFF response magnitudes for thalamic and cortical neuronal populations increased as the stimulus duration was increased from 200 to 1,400 ms. Increases were greater at nonoptimal deflection angles. Similarly, individual cells having smaller OFF responses for the duration-short stimulus tended to display proportionately greater increases when the stimulus was lengthened. OFF responses of trigeminal ganglion cells were largely unaffected by stimulus duration. 3. Barrel neurons were subclassified as regular-spike units (RSUs) or fast-spike units (FSUs) on the basis of the time course of their action potentials. ON and OFF responses were smaller in the former and, when the stimulus was lengthened, percentage increases in their OFF responses were greater than those in FSUs. Results illustrate nonlinear transformations of the thalamic input signal by RSUs, which are presumed to be excitatory barrel neurons, and extend previous findings of response similarities between thalamocortical units (TCUs) and FSUs, the latter of which are thought to be inhibitory. 4. The time course of OFF response suppression in cortical neurons suggests that stimulus onset evokes central inhibition having two components, a potent one lasting several tens of milliseconds and a weaker one lasting many hundreds of milliseconds. Background activity levels in cortex and thalamus were diminished for> or = 1,800 ms after whisker movement. 5. For TCUs, 200-ms stimuli were less likely than 1,400-ms stimuli to elicit an OFF response, but when responses occurred they consisted of a greater number of spikes timed closer together. By contrast, the 200-ms stimulus OFF responses of the RSUs and FSUs displayed longer interspike intervals than did their 1400-ms responses, with no change in the number of spikes per response.(ABSTRACT TRUNCATED AT 400 WORDS)
Cerebellar control of postural scaling and central set in stance
Authors: Horak F. B. , Diener H. C.
Published: December 2017

1. The effects of cerebellar deficits in humans on scaling the magnitude of automatic postural responses based on sensory feedback and on predictive central set was investigated. Electromyographic (EMG) and surface reactive torques were compared in patients with anterior lobe cerebellar disorders and in normal healthy adults exposed to blocks of four velocities and five amplitudes of surface translations during stance. Correlations between the earliest postural responses (integrated EMG and initial rate of change of torque) and translation velocity provided a measure of postural magnitude scaling using sensory information from the current displacement. Correlations of responses with translation amplitude provided a measure of scaling dependent on predictive central set based on sequential experience with previous like displacements because the earliest postural responses occurred before completion of the displacements and because scaling to displacement amplitude disappeared when amplitudes were randomized in normal subjects. 2. Responses of cerebellar patients to forward body sway induced by backward surface displacements were hypermetric, that is, surface-reactive torque responses were two to three times larger than normal with longer muscle bursts resulting in overshooting of initial posture. Despite this postural hypermetria, the absolute and relative latencies of agonist muscle bursts at the ankle, knee, and hip were normal in cerebellar patients. 3. Although they were hypermetric, the earliest postural responses of cerebellar patients were scaled normally to platform displacement velocities using somatosensory feedback. Cerebellar patients, however, were unable to scale initial postural response magnitude to expected displacement amplitudes based on prior experience using central set. Randomization of displacement amplitudes eliminated the set effect of amplitude on initial responses in normal subjects, but responses to randomized and blocked trials were not different in cerebellar patients. 4. Cerebellar patients compensated for hypermetric responses and lack of anticipatory scaling of earliest gastrocnemius activity by scaling large, reciprocally activated tibialis and quadriceps antagonist activity with the displacement velocity and amplitude. Correlations between these antagonist EMG integrals and displacement amplitudes were preserved when amplitudes were randomized, suggesting that feedback-dependent and not set-dependent mechanisms were responsible for scaling of antagonists by cerebellar patients. Antagonist compensation for initial hypermetric responses also could be induced in normals when they overresponded to unexpectedly small amplitudes of surface displacements. 5. The major effects of anterior lobe cerebellar damage on human postural responses involves impairment of response magnitude based on predictive central set and not on use of velocity feedback or on the temporal synergic organization of multijoint postural coordination.(ABSTRACT TRUNCATED AT 400 WORDS)
The primate subthalamic nucleus. I. Functional properties in intact animals
Authors: Wichmann T. , Bergman H. , DeLong M. R.
Published: December 2017

1. The present study tests several key aspects of the current model of the intrinsic circuitry of the basal ganglia, in particular the degree to which basal ganglia-thalamocortical circuits are functionally segregated at the level of the subthalamic nucleus (STN). To this end the responses of STN cells to somatosensory examination (n = 301 cells), the polarity and latencies of neuronal responses to passive and active movements (n = 223 cells), responses to microstimulation (n = 1589 sites), and cross-correlation functions of pairs of neighboring neurons (n = 72 pairs) were studied in STNs of three African green monkeys. 2. The activity of 55% of cells examined in STN was briskly modulated in response to passive movements of individual contralateral body parts. Of these, 86% responded to passive joint rotation of muscle palpation, but in some cases (25% of responding cells) responses were also elicited by light touch. In 91% of the responding cells responses were elicited by manipulations around a single joint only. 3. The caudoventral sector in STN was largely devoid of cells with responses to somatosensory stimulation. Within the rostrodorsal zone a lateral region containing neurons that responded to arm movements and a more medial region with neurons responding to leg movement were found. Cells responding to orofacial movements were located more dorsally and rostrally. Neurons with similar responses to active and passive movements of the limbs tended to be clustered within “arm” and “leg” zones. 4. Of identified arm cells in STN (n = 80), 36% responded to the application of torque pulses to the elbow (43 responses overall). Forty-eight percent of these cells responded to both extension and flexion torques. Ninety-three percent of the responses were initial increases in discharge, which characteristically occurred earlier and were shorter than initial decreases. Fifty-three percent of the responses were biphasic or multiphasic. 5. During active step tracking movements 40% of STN arm cells (n = 53 cells) responded with significant changes in activity. Thirty-six percent of these cells showed responses with both extension and flexion movements. Of the responses, 90% were increases in discharge. Only 14% of all responses were biphasic or multiphasic. Responses tended to occur around the time of movement onset (average latency 2 ms after movement onset). 6. Microstimulation (bipolar pulses, 40 microA, 200–500 ms train duration, 400 Hz) of the core of STN itself did not appear to produce movement.4+ synchronized activity in only 11% of pairs.(ABSTRACT TRUNCATED AT 400 WORDS)
Pre- and postsynaptic components of nicotinic long-term potentiation in the superior cervical ganglion of the cat
Authors: Morales M. A. , Bachoo M. , Collier B. , Polosa C.
Published: December 2017

1. In anesthetized, atropine-treated cats we measured the acetylcholine (ACh) release into the venous effluent of the superior cervical ganglion (SCG) and the nictitating membrane (NM) contraction evoked by a 2-Hz, 20-s test train to the ipsilateral cervical sympathetic trunk (CST). We also measured NM contraction produced by injection of ACh (50 micrograms) or 1,1-dimethyl-4-phenylpiperazinium (DMPP, 5 micrograms) into the arterial supply of the ipsilateral SCG. 2. After a 10- to 30-s, 40-Hz conditioning train to CST these responses were all potentiated. The potentiation of the NM response evoked by the test train or by the exogenous agonists was long lasting (90% decay in 64 +/- 10 min, mean +/- SE, for the train-evoked response; 42 +/- 9 min for the response to injected ACh; 61 +/- 18 min for the response to injected DMPP), whereas the potentiation of the ACh release lasted only for 9 min. 3. On the assumption that ACh and DMPP injected into the ganglionic arterial supply acted postsynaptically, these data suggest that the main mechanism of the long-term potentiation (LTP) of nicotinic transmission in SCG is an increase in postsynaptic responsiveness. Because the response to KCl (250 micrograms) injected into the ganglionic arterial supply was not potentiated after the conditioning train, a posttrain increase in excitability of the postsynaptic membrane is not likely to be the cause of the postsynaptic increased responsiveness to ACh and DMPP.(ABSTRACT TRUNCATED AT 250 WORDS)
Electronic structure of motoneurons in spinal cord slice cultures: a comparison of compartmental and equivalent cylinder models
Authors: Ulrich D. , Quadroni R. , Luscher H. R.
Published: December 2017

1. Voltage-clamp, current-clamp, and morphological data were obtained from visually identified motoneurons in organotypic cocultures of rat embryonic spinal cord, dorsal root ganglia, and skeletal muscle. The cells were injected with Biocytin during whole-cell patch-clamp recordings and stained with horseradish peroxidase. 2. The somata and dendritic trees of the cells were reconstructed with a semiautomatic reconstruction system. The motoneurons had a common multipolar shape. An elliptic soma gave rise to 3-9 stem dendrites with a mean diameter of 2.5 +/- 0.9 (SD) micron terminating in 24 +/- 7 dendritic endings. The mean total dendritic path length was 3,306 +/- 1,075 microns. The mean total membrane surface area was 15,594 +/- 10,404 microns 2 with a dendritic to somatic membrane surface area ratio of 3.4 +/- 1.4 (n = 7 cells). 3. The ratio between the sum of the diameters of the two daughter branches and the diameter of the parental branch each raised to the 3/2 power at all branch points was 1.3 +/- 0.28 (n = 8 cells). The dendritic trees of the cells tapered continuously from the soma to the distal ends. The mean normalized dendritic trunk parameter of all cells was 0.62 +/- 0.22. 4. The motoneurons had a mean input resistance RN of 498 +/- 374 M delta, a mean membrane time constant (tau m) of 22 +/- 4.6 ms, and a mean dendritic dominance (rho) of 2.7 +/- 0.86 (n = 5 cells). The mean electronic length (L) calculated from tau m and the slowest voltage-clamp time constant (tau VC1) was 0.7 +/- 0.04 (n = 7 cells). 5. The specific membrane capacitance (Cm) estimated from the charge of the capacitive current during a voltage step and the total membrane surface area was 1.08 +/- 0.3 microF/cm2 (n = 6 cells). 6. Compartmental computer models were constructed of individual cells. Experimental and simulated voltage transients were matched with Cm = 1 microF/cm2, a uniform membrane resistivity (Rm) = tau m/Cm and a cytosolic resistivity (Ri) of 308 +/- 39 omega.cm (n = 3 cells). 7. The mean electrotonic length of the dendritic paths was 0.83 +/- 0.2 (n = 5 cells). The mean input resistance at the dendritic terminals (RT) was 1,413 +/- 260 M omega. Synaptic conductances were applied at all distal dendritic compartments of the model cells. The resulting synaptic currents were calculated at the input site and at the soma. The mean transient current attenuation ratio was 4.7 +/- 1.7 under idealized voltage-clamp conditions.(ABSTRACT TRUNCATED AT 400 WORDS)