bluuebunny/crossref_metadata_2025 huggingface dataset:
Modality specificity of neuronal responses within the cat's insula
Authors: Hicks T. P. , Benedek G. , Thurlow G. A.
Published: December 2017

1. Electrophysiological recordings of single-unit responses, multiunit responses, and electrically evoked field potentials have been made using carbon fiber-containing micropipettes in cats anesthetized with barbiturate and immobilized with gallamine triethiodide. Recording sites sampled cortical regions throughout the insula, including zones more ventrally situated and more rostral and caudal than those described in the preceding, companion paper. One-hundred eleven cells in total were tested with a battery of different types of stimuli. 2. Stimuli were divided into two classes, according to either the intensity of the stimulus or its form. These are called physiological forms, or levels of stimulation, and nonphysiological forms or levels. The nonphysiological forms of stimuli for visual, somatosensory, and auditory modalities consisted of (for visual stimuli): 1) electrical stimulation of the optic nerve or 2) bright flashes light at 100% contrast; for somatosensory, electrical stimulation of the radial nerve by implanted cuff electrodes; and for auditory, stimulation with bursts of white noise generated at high intensities (80-100 dB) or with a loud click stimulus. Physiologically relevant levels of stimuli for these same modalities were: moving bars of light projected onto a tangent screen in front of the animal (visual); light cutaneous deformation, hair displacement, and light pressure delivered to various regions on the surface of the cat's body with hand-held probes, or delivered manually (somatosensory); and white noise generated at low intensities (ca. 40 dB) (auditory). 3. Cells situated in dorsal insular regions responded to visual stimuli when levels of sensory activation were employed using natural means, within normal, physiologically relevant limits. Responses to auditory or somatosensory stimulation were observed in this region only when very intense forms of "natural" stimulation, or when electrical stimulation (nonphysiologically relevant levels of stimulation) was delivered. In this latter case, the same cells in several instances could be made to appear polymodally responsive. With cells situated in ventral insular regions, some polymodal responses to physiologically relevant levels of stimulation were noted, although it was considerably more common to obtain unimodal responses. Nonphysiological levels of activation yielded evidence for a polymodal convergence onto the greater proportion of cells recorded. 4. Field potential recordings with microelectrodes revealed widely overlapping representations of all modalities in both dorsal and ventral regions of the insula, irrespective of the sensitivity displayed by the local neuronal r
Intrinsic organization of the rat cutaneus trunci motor nucleus
Authors: Theriault E. , Diamond J.
Published: December 2017

1. We have investigated how the organization of the cutaneus trunci muscle (CTM) motor nucleus might correspond to the pattern of its physiological activation (see accompanying report, 61) by using HRP to label retrogradely the motoneurons supplying different anatomically and physiologically defined muscle compartments. The CTM motoneuron pool was found to be comprised of a tightly packed column of ventrolaterally located cells extending from caudal C6 to rostral T1 and to contain 1,183 cells per side; this unusually large number of motoneurons is consistent with the precisely localized reflex behavior exhibited by the muscle. 2. Each of three major motor nerves that functionally divide the CTM into three major longitudinal muscle fields (dorsal, lateral, ventral) was found to derive from a distinct subcolumn of motoneurons, which extends for the full rostrocaudal length of the parent CTM motor nucleus, such that the dorsal motor nerves derive from a medially located subcolumn, the lateral motor nerves from a centrally located subcolumn, and the ventral motor nerves from a subcolumn of motoneurons that sits most laterally in the CTM motor nucleus. 3. Localized injections of HRP into different rostrocaudal regions of the muscle revealed a further subdivision of the CTM motor nucleus: motoneurons located rostrally in the motoneuron pool supplied the rostral regions of the muscle, whereas more caudally located motoneurons in the pool supplied progressively more caudal sites in the muscle. 4. These results reveal the existence of both a mediolateral and a rostrocaudal subdivision of the motor nucleus; thus this intrinsic spatial organization of motoneurons relates the CTM motor nucleus topographically to the body coordinates of its target, the muscle. The possible relation of these findings to the expression of local sign in the CTM reflex, and how the underlying circuitry could develop appropriately, is discussed.
Gustatory responsiveness of fibers in the hamster glossopharyngeal nerve
Authors: Hanamori T. , Miller I. J. , Smith D. V.
Published: December 2017

1. Mammalian taste receptors are distributed within separate subpopulations, innervated by branches of cranial nerves VII, IX, and X. Most gustatory electrophysiology has focused on input from the fungiform papillae on the anterior portion of the tongue, carried by the chorda tympani branch of the VIIth nerve. However, only a small percentage of the taste buds are located in the fungiform papillae (approximately 18% in the hamster). There have been no studies on the hamster's IXth nerve, which innervates greater than 50% of its taste buds, and most other studies of IXth nerve function have employed only whole-nerve recording. 2. Action potentials were recorded from 83 individual fibers in the IXth nerve of the hamster. Stimuli were five concentrations each of sucrose, NaCl, HCl, and quinine hydrochloride (QHCl), all presented to every fiber at 37 degrees C. Responses were quantified as the number of impulses in 10 s minus the preceding 10 s of spontaneous activity. 3. Across these concentration series, HCl and QHCl were by far the most excitatory stimuli, with mean responses across all cells three to four times greater than those evoked by sucrose or NaCl. The order of effectiveness of the stimuli was H greater than Q much greater than N greater than S. 4. Of the 83 fibers, 56 were stimulated via the foliate papillae and 27 via the single vallate papilla. No fibers responded to both of these fields. There were generally no differences in the sensitivity of these two subpopulations of taste buds, except that QHCl was more effective when applied to the foliates. 5. A "total" response measure was derived by summing the excitatory responses to each stimulus across the entire concentration series. The fibers were then classified according to the best total response, resulting in 52 HCl-, 19 QHCl-, 8 sucrose- and 4 NaCl-best cells. Considering the slope of the concentration-response functions as a criterion for classification produced very similar results. The fiber classification varied somewhat with concentration, with more fibers categorized as HCl- and QHCl-best at the higher concentration levels. 6. Breadth of responsiveness was measured using the equation developed by Smith and Travers. At the concentrations used to examine hamster chorda tympani fibers, IXth nerve fibers were not very responsive and were quite narrowly tuned to the four taste qualities. At higher concentrations the fibers became more broadly responsive across the four stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)
Effect of catecholamine-receptor antagonists on feeding-related neuronal activity in the central amygdaloid nucleus of the monkey: a microiontophoretic study
Authors: Jiang L. H. , Oomura Y.
Published: December 2017

1. Neuronal activity in the central amygdaloid nucleus (ACE) was recorded during a visually guided bar-press feeding task, and the modulatory effects of catecholaminergic blockers were investigated. 2. The feeding task had the following four phases: 1) a cue light to signal the start of bar press, 2) bar press, 3) a short cue tone followed by food delivery, and 4) ingestion reward. Of 278 cells observed, 176 (63%) increased or decreased their discharge rates in one or more phases of the feeding task. Of these, 60 (34%) responded to the cue light, 81 (46%) to the bar press, 66 (37%) to the cue tone, and 176 (100%) during the reward period. In the ingestion reward phase, firing of 128 (73%) increased and firing of 48 (27%) decreased. The reward-related response depended on the nature of food. In the trials with aversion food, some neurons increased firing (n = 6), whereas others showed opposite firing changes (n = 10). 3. The decreased firing rate during the reward period was greatly attenuated in the no-reward tasks (n = 29) and was blocked by electrophoretic application of a beta-adrenoceptive antagonist [sotalol (SOT), n = 26]. Noradrenaline (NA) application mimicked the inhibitory effect on the reward-related activity during extinction trial (n = 4). These results suggest that the decreased firing rate observed during the reward period was modulated by beta-adrenoreceptors. 4. Of 32 neurons tested, the activity of 8 (25%) and 14 (44%) were enhanced by the cue light or bar press, respectively. These effects were attenuated by electrophoretic application of a dopamine (DA) antagonist [spiperone (SPP)] but not by SOT. This indicates that dopaminergic inputs may be related to recognition of visual signals and to motor initiation during the monkey feeding paradigm.
Connectivity pattern of the cercal-to-giant interneuron system of the American cockroach
Authors: Daley D. L. , Camhi J. M.
Published: December 2017

1. The pattern of connectivity between identified cercal afferents and the three largest giant interneurons (GIs 1, 2, and 3) of the American cockroach was investigated by intracellular methods. These three GIs all have different directional response sensitivities and appear to be especially important in initiating the short latency escape behavior of the American cockroach. 2. One of the interneurons, GI 1 responds to wind from all four quadrants of space about the animal. However, it clearly shows a greater ipsilateral versus contralateral (relative to the GI's axon within the nerve cord) wind sensitivity. In contrast, the directional sensitivity of GI 2 is more nearly bilaterally symmetrical. Both of these interneurons receive excitatory synaptic input from the sensory cells of the nine most prominent columns (a, d, g, f, h, i, k, l, and m) of filiform hairs of the ipsilateral cercus. 3. The nine ipsilateral inputs all made roughly equivalent strength excitatory connections with GI 1. The connectivity pattern to GI 2 was the same as that to GI 1 except that the connection strength for two of the nine columns, h and i, was substantially stronger to GI 2 than to GI 1. The remaining seven sensory columns all make equivalent strength connection with GI 2. 4. Only select columns of contralateral sensory cells made synaptic connection with GIs 1 and 2. All detectable connections produced subthreshold depolarizations. 5. The response curve of GI 3 is more sharply restricted in space than that of either GI 1 or 2 and this interneuron only responds to wind stimuli originating from in front of the animal. GI 3 received excitatory synaptic input only from ipsilateral columns d, f, g, i, and k, all of which have their best excitatory directions well within the boundaries of the response curve of GI 3. Columns a and l with best excitatory directions near the edges of the response curve of GI 3 made no detectable connection. The remaining two columns (h and m) with best excitatory directions well outside the boundaries of the response curve of GI 3 provided inhibitory input. 6. GI 3 received synaptic input from contralateral columns d, f, g, h, i, k, and m.(ABSTRACT TRUNCATED AT 400 WORDS)
Spread of synchronous firing in longitudinal slices from the CA3 region of the hippocampus
Authors: Miles R. , Traub R. D. , Wong R. K.
Published: December 2017

1. Mechanisms underlying the propagation of synchronous epileptiform activity in disinhibited hippocampal slices were examined in experimental and computer simulation studies. 2. Experiments were performed with longitudinal slices of the CA3 region. Synchronous firing was initiated by stimulating stratum radiatum fibers in the presence of picrotoxin. It propagated smoothly and without decrement at velocities close to 0.15 m/s over distances up to 10 mm. 3. In elevated extracellular calcium, neuronal firing threshold was increased and synchronous burst firing did not spread. Monophasic excitatory postsynaptic potentials (EPSPs) were recorded in cells at limited distances from a stimulus in the presence of 10 mM Ca and picrotoxin. Axonal conduction velocity, estimated from EPSP latencies, was several times faster than the spread of synchronous firing. 4. EPSPs recorded in 5-7 mM Ca and picrotoxin could consist of two components. The properties of the first component were similar to those of synaptic events recorded in 10 mM Ca. The second component was of longer latency and unlike the first component was suppressed in responses to paired stimuli at interval 50-300 ms. Recordings from cells at different distances from a stimulus suggested that the second component spread further and more slowly than the first component. 5. In computer simulations the CA3 region was represented by a spatially distributed network of 9,000 excitatory neurons and 900 inhibitory cells. Individual cells and synapses had properties based on experimental data. The effects of varying synaptic strength and connectivity on the spread of activity in the model was examined. 6. When synaptic inhibition was functional in simulations, firing was restricted to a single action potential in model cells close to the stimulus, as in experiments. Synchronous burst firing spread throughout the neuronal array when fast synaptic inhibition was absent. The velocity of propagation was slower than conduction in simulated axons when synaptic contacts made by excitatory cells were spatially limited. Propagation velocity increased with increases in the spatial extent of excitatory connectivity. 7. Increasing the threshold of neurons in a region of the model network reduced the speed at which synchronous firing spread. In experiments focal application of gamma-aminobutyric acid (GABA) elevated neuronal firing threshold and slowed the propagation of synchrony in a local region. 8. As the strength of synaptic inhibition was gradually reduced, neuronal activity spread further and faster through the simulated neuronal network.(ABSTRACT TRUNCATED AT 400 WORDS)
Dissection of the neuron network in the catfish inner retina. II. Interactions between ganglion cells
Authors: Sakai H. M. , Naka K.
Published: December 2017

1. To characterize signal interactions between ganglion cells, extrinsic current, either sinusoidally or white-noise modulated, was injected into a ganglion cell and the resulting extracellular spike discharges were recorded from a neighboring ganglion cell. 2. Current injected into an ON-ganglion (GA) cell modulated the spike discharges of a neighboring ON-ganglion cell (GA). Similarly, a current injected into an OFF-ganglion (GB) cell modulated the spike discharges of a neighboring OFF-ganglion (GB) cell. The signal transmission between ganglion cells of the same response polarity was fast and sign-noninverting. The transfer function was lowpass with a cutoff frequency of 30 Hz. The efficacy of the transmission was comparable to that from bipolar or amacrine to ganglion cells of the same polarity. 3. Current injected into an ON-ganglion (GA) cell modulated the spike discharges of a neighboring OFF-ganglion (GB) cell; the signal transmission was slow and sign-noninverting. Correspondingly, current injected into an OFF-ganglion (GB) cell modulated the spike discharges of a neighboring ON-ganglion (GA) cell; transmission was slow and sign-inverting. 4. A brief electrical stimulation of the optic nerve activated a single antidromic ganglion cell spike at threshold. With suprathreshold stimulation, multiple spikes appeared, which probably were activated orthodromically. Changes in membrane potential of ganglion and amacrine cells induced by optic nerve stimulation usually lasted 50-80 ms, with an initial depolarization followed by hyperpolarization. We interpret such long-lasting responses to be mediated by reciprocal circuits that include amacrine, bipolar, and ganglion cells. 5. Together with the observations made by Sakai and Naka, we conclude that virtually almost all amacrine, bipolar, and ganglion cells are functionally interconnected; direct and fast connections are established among ON-cells and similarly among OFF-cells, and complex, indirect connections are established between ON- and OFF-cells.
Acute effects of spinal transection on EPSPs produced by single homonymous Ia-fibers in soleus alpha-motoneurons in the cat
Authors: Cope T. C. , Hickman K. R. , Botterman B. R.
Published: December 2017

1. Excitatory postsynaptic potentials (EPSPs) generated in soleus motoneurons by single homonymous Ia-fibers were measured using intracellular recording and the spike-triggered averaging technique. Two groups of barbiturate-anesthetized adult cats were studied: one with the spinal cord intact and the other with the spinal cord severed at thoracic segment 13 (T13) several hours prior to recording. 2. In cord-transected cats, single homonymous Ia-fibers produced EPSPs in soleus motoneurons that were, on average, larger and faster rising relative to normal, as they are for those produced in medial gastrocnemius (MG) motoneurons (8, 12, 13, 40). Specifically, mean EPSP amplitude and rise time were, respectively, 261 +/- 22 microV and 0.65 +/- 0.05 ms for the transected group vs. 160 +/- 21 microV and 0.96 +/- 0.08 ms for the intact group. The group means for each parameter were significantly different (P less than 0.005). 3. The group difference in EPSP amplitude was largely due to a decrease in number of small EPSPs in the transected group (11% less than 100 microV compared with the normal 41%) and not due to the occurrence of unusually large ones. Ratios of the largest to smallest amplitude EPSPs produced in the same motoneuron were similarly distributed for intact and transected groups, implying that the effect of transection on EPSP size was uniform across different Ia-fiber synapses made with the same motoneuron. Mean EPSP amplitude for each transected cat (n = 5) was larger than normal, but in some cases the increase took greater than 10 h to express itself. 4. The normal tendency for EPSP rise time to decline on average with amplitude was absent in the transected group, wherein rise time was reduced to similar average values in all amplitude categories. This suggests that the decrease in rise time occurred independently of the increase in amplitude. In contrast, EPSP half-width, which tended tow ward lower than normal values [5.63 +/- 0.36 (SE) ms vs. 6.51 +/- 0.44 ms; P greater than 0.10], decreased in proportion with rise time as evidenced by the preservation of the normal relation between those parameters in transected cats. Normalizing EPSPs by motoneuron time constant (tau) reduced the group differences in rise time and half-width, suggesting that a fall in tau contributes to the abbreviation of EPSP time course. 5. The condition of the spinal cord best accounted for differences in synaptic strength between groups.(ABSTRACT TRUNCATED AT 400 WORDS)
Periodicity coding in the inferior colliculus of the cat. II. Topographical organization
Authors: Schreiner C. E. , Langner G.
Published: December 2017

1. The topographical distributions of single-unit and multiple-unit responses to amplitude-modulated tones--and to other relevant parameters of simple tonal stimuli--were defined across the main frequency representational gradient and within narrow frequency ranges represented in "frequency band laminae" in the principal midbrain auditory nucleus, the central nucleus of the inferior colliculus (ICC), in adult, barbiturate-anesthetized cats. 2. Responses to amplitude-modulated tones with the carrier set at the characteristic frequency (CF) of recorded neurons were obtained at many ICC locations in each experiment. The best modulation frequency (BMF) of neurons was defined at each site as that modulation frequency producing the highest neural discharge rate. Encountered BMFs ranged from approximately 10 to 1,000 Hz. A significant range of BMFs were recorded for neurons with any given characteristic frequency. BMF ranges varied as a systematic function of CF and of ICC recording depth. 3. Recorded BMFs were distributed topographically within functionally defined ICC frequency band laminae. Highest BMFs were found clustered in an ICC sector roughly between the middle and lateral third of its frequency band laminae. Progressively lower BMFs were recorded with increasing distance across the laminae in any direction away from the highest-BMF cluster. That is, "iso-BMF contours" were arrayed concentrically around the highest-BMF region. 4. Within frequency band laminae centered at approximately 3 and 12 kHz, quality factors (Q10 dBS) of frequency tuning curves were found to be between 0.8 and 8. Q10 dB values were distributed topographically within given frequency band laminae. Responses with narrow tuning curves (high Q10 dB values) were clustered in the middle third of the mediolateral extent of laminae; sharpness of tuning declined systematically away from this focus of highest Q10 dB values. The center of this distribution did not coincide with the center of the BMF distribution within the same lamina. 5. For neurons at greater than 90% of the ICC loci studied in these experiments, onset latencies to CF tones defined approximately 60 dB above response threshold fell within a range between 5 and 18 ms. Across a given frequency band lamina, onset latencies varied systematically, with longest response latencies recorded medially, and progressively shorter latencies recorded progressively more laterally. 6. Binaural interaction types were systematically distributed within frequency-band laminae. A cluster of excitatory-excitatory (EE) was seen, covering approximately one-third of the mapped area.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of the acoustic striae in hearing: contribution of dorsal and intermediate striae to detection of noises and tones
Authors: Masterton R. B. , Granger E. M.
Published: December 2017

1. Behavioral thresholds were obtained from cats, first with only their right ear and right dorsal, intermediate, and ventral acoustic striae (DAS, IAS, and VAS, respectively) intact, and then again with only their right ventral acoustic stria intact. 2. Using usual definitions of "threshold" the loss of the dorsal and intermediate acoustic striae results in no measurable deficit in the detection of noises or tones on a silent background. 3. In sharp contrast, even partial damage of the ventral acoustic stria (i.e., trapezoid body section) results in marked deficits in sound detection. 4. Therefore, the ventral acoustic stria is both necessary and sufficient to maintain normal acoustical sensitivity. 5. However, loss of the dorsal and intermediate striae seems to result in a degradation of reliability in the detection of suprathreshold sounds--perhaps akin to a deficit in listening.
Combination-sensitive neurons in the ventroanterior area of the auditory cortex of the mustached bat
Authors: Tsuzuki K. , Suga N.
Published: December 2017

1. Because the ventroanterior (VA) area is one of the target areas of the FM-FM area in the auditory cortex of the mustached bat, Pteronotus parnellii parnellii, response properties of combination-sensitive neurons in this area were studied with constant-frequency (CF) tones, frequency-modulated (FM) sounds, and sounds similar to the bat's biosonar signal (pulse), which consisted of long CF components (CF1-4) and short FM components (FM1-4). CF1-4 and FM1-4 are the components in the four harmonics (H1-4) of the pulse. 2. Combination-sensitive neurons are clustered in a small area immediately anteroventral to the Doppler-shifted CF processing (DSCF) area and posteroventral to the anterior division of the primary auditory cortex. Because this cluster in the VA area is small, it was difficult to record a sufficient number of combination-sensitive neurons to explore the functional organization of the cluster, but it was found that the response properties of these VA neurons were unique. 3. Combination-sensitive neurons in the VA area are tuned to particular combinations of signal elements similar to the first and second harmonics of the pulse and/or echo. Unlike neurons in the FM-FM, dorsal fringe (DF), and CF/CF areas, no neurons in the VA area are tuned to the signal elements in the first and third or fourth harmonics. 4. The great majority of combination-sensitive neurons in the VA area can not be easily classified into either FM-FM or CF/CF neurons, because they show facilitative responses to combinations of CF1/CF2, FM1-FM2, and FM1-CF2. Therefore, they are called H1-H2 neurons. In the FM-FM and CF/CF areas, all the neurons could be easily classified as FM-FM or CF/CF. This uniqueness of H1-H2 neurons is related to the fact that their best frequencies for facilitation are predominantly between 61.0 and 62.0 kHz, i.e., within the frequency range of stabilized Doppler-shifted echo CF2. 5. In addition to 27 H1-H2 neurons, 7 FM1-FM2 neurons were also recorded in the VA area. The best delays of these H1-H2 and FM1-FM2 neurons measured with FM1-FM2 pairs are between 1 and 10 ms. Unlike neurons in the FM-FM and DF areas, their delay-tuning curves are very broad, even if their best delays are short, and extend beyond zero delay to several millisecond "negative" delays of the FM2 from the FM1, i.e., several millisecond delays of the FM1 from the FM2.(ABSTRACT TRUNCATED AT 400 WORDS)
Electrical properties and innervation of fibers in the orbital layer of rat extraocular muscles
Authors: Jacoby J. , Chiarandini D. J. , Stefani E.
Published: December 2017

1. The inferior rectus muscle of rat, one of the extraocular muscles, contains two populations of multiply innervated fibers (MIFs): orbital MIFs, located in the orbital layer of the muscle and global MIFs, found in the global layer. The electrical properties and the responses to nerve stimulation of orbital MIFs were studied with single intracellular electrodes and compared with those of twitch fibers of the orbital layer, MIFs of the global layer, and tonic fibers of the frog. 2. About 90% of the orbital MIFs did not produce overshooting action potentials. In these fibers the characteristics and time course of the responses to nerve stimulation varied along the length of the fibers. Within 2 mm of the end-plate band of the muscle, the responses consisted of several small end-plate potentials (EPPs) and a nonovershooting spike. Distal to 2 mm, the responses in most fibers consisted of large and small EPPs with no spiking response. Some fibers produced very small spikes surmounted on large EPPs. 3. Overshooting action potentials were observed in approximately 10% of the orbital MIFs recorded between the end-plate band and 2 mm distal. The presence or absence of action potentials was not related to the magnitude of the resting potential of the fibers. 4. The threshold of nerve stimulated responses in orbital MIFs was the same as that in orbital twitch fibers. A large number of orbital MIFs had latencies equal to those for the orbital twitch fibers recorded at the same distance from the end-plate band, but the average latency was greater in the MIFs. The latency of orbital MIFs was about one-half of that for the MIFs of the global layer. The values for the effective resistance and membrane time constant of orbital MIFs fell between those for orbital twitch fibers on the one hand, and global MIFs and frog tonic fibers on the other. 5. In order to compare electrical properties with innervation patterns, fibers identified electrophysiologically as orbital MIFs were injected with the fluorescent dye Lucifer yellow and then traced in Epon-embedded, serial transverse sections. In addition to numerous superficial endings distributed along the fibers, a single "en plaque" ending was also found in the end-plate band that resembled the end plates of the adjacent orbital twitch fibers. 6. From these results we conclude that the electrical activity of orbital MIFs varies along the length of the fibers.(ABSTRACT TRUNCATED AT 400 WORDS)
Kinetic analysis of acetylcholine-induced current in isolated frog sympathetic ganglion cells
Authors: Akaike N. , Tokutomi N. , Kijima H.
Published: December 2017

1. Kinetic properties of activation and inactivation phases of the ACh-gated nicotinic current were investigated in isolated frog sympathetic ganglion cells using "concentration-clamp" technique under voltage-clamp conditions. This technique combines internal perfusion with a rapid change of the external solution within a few milliseconds. 2. The dose-response curve for the peak current induced by ACh showed a sigmoidal increase, in which the apparent dissociation constant Kd and Hill coefficient were 2.6 x 10(-5) M and 2.0, respectively. 3. The current-voltage relationship of ACh-induced currents were linear at potentials more negative than the reversal potential (EACh) of -5.5 +/- 1.3 mV (mean +/- SE) but showed a slight inward rectification at positive potentials over +20 mV. Since this current could be generated predominantly by an increase of Na+ and K+ conductances, the value of EACh was close to the theoretical potential, -1.3 mV, for the total amount of both Na+ and K+ or Cs+ in the extracellular and intracellular solutions. 4. There was no difference between the dose-response curves of ACh- and nicotine-induced currents. The ACh-induced current was suppressed in a competitive manner by the nicotinic antagonists, d-tubocurarine and hexamethonium, but muscarine did not induce any response, indicating that the ACh-gated current might be mediated by the nicotinic ACh receptor-ionophore complex. 5. There was a latent period of the order of milliseconds in the ACh receptor activation phase before attaining exponential increase of activation process.(ABSTRACT TRUNCATED AT 250 WORDS)
Inositol trisphosphate and activators of protein kinase C modulate membrane currents in tail motor neurons of Aplysia
Authors: Sawada M. , Cleary L. J. , Byrne J. H.
Published: December 2017

1. We have investigated how activation of the inositol lipid second messenger pathway may contribute to modulation of membrane currents in tail motor neurons of Aplysia. Specifically, we examined the effects of injected inositol 1,4,5-trisphosphate (IP3) and analogues of diacylglycerol (DAG), both of which are products of the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2). 2. Injection of IP3 produced an outward current associated with an apparent increase in membrane conductance. Ion substitution experiments, the sensitivity of the response to low concentrations of TEA and its attenuation by intracellular injections of EGTA suggest that the current produced by injection of IP3 is a calcium-activated K+ current (IK,Ca). 3. The response to IP3 was mimicked by intracellular injection of Ca2+. Injection of Ca2+ produced an outward current that was associated with an apparent increase in input conductance of the membrane. The same manipulations that affected the response to IP3 (see above) also affected the response to injections of Ca2+. 4. Injections of activators of protein kinase C (PKC) produced a relatively slow inward current. The inward current has not been fully analyzed, but it does not appear to be due to the actions of any single conventional ion channel. 5. Activators of PKC attenuated responses to subsequent injections of IP3 indicating that one component of PIP2 hydrolysis can attenuate the other. 6. The results suggest that hydrolysis of inositol phospholipids is a mechanism for regulation of membrane properties in tail motor neurons of Aplysia.
Mnemonic coding of visual space in the monkey's dorsolateral prefrontal cortex
Authors: Funahashi S. , Bruce C. J. , Goldman-Rakic P. S.
Published: December 2017

1. An oculomotor delayed-response task was used to examine the spatial memory functions of neurons in primate prefrontal cortex. Monkeys were trained to fixate a central spot during a brief presentation (0.5 s) of a peripheral cue and throughout a subsequent delay period (1-6 s), and then, upon the extinction of the fixation target, to make a saccadic eye movement to where the cue had been presented. Cues were usually presented in one of eight different locations separated by 45 degrees. This task thus requires monkeys to direct their gaze to the location of a remembered visual cue, controls the retinal coordinates of the visual cues, controls the monkey's oculomotor behavior during the delay period, and also allows precise measurement of the timing and direction of the relevant behavioral responses. 2. Recordings were obtained from 288 neurons in the prefrontal cortex within and surrounding the principal sulcus (PS) while monkeys performed this task. An additional 31 neurons in the frontal eye fields (FEF) region within and near the anterior bank of the arcuate sulcus were also studied. 3. Of the 288 PS neurons, 170 exhibited task-related activity during at least one phase of this task and, of these, 87 showed significant excitation or inhibition of activity during the delay period relative to activity during the intertrial interval. 4. Delay period activity was classified as directional for 79% of these 87 neurons in that significant responses only occurred following cues located over a certain range of visual field directions and were weak or absent for other cue directions. The remaining 21% were omnidirectional, i.e., showed comparable delay period activity for all visual field locations tested. Directional preferences, or lack thereof, were maintained across different delay intervals (1-6 s). 5. For 50 of the 87 PS neurons, activity during the delay period was significantly elevated above the neuron's spontaneous rate for at least one cue location; for the remaining 37 neurons only inhibitory delay period activity was seen. Nearly all (92%) neurons with excitatory delay period activity were directional and few (8%) were omnidirectional. Most (62%) neurons with purely inhibitory delay period activity were directional, but a substantial minority (38%) was omnidirectional. 6. Fifteen of the neurons with excitatory directional delay period activity also had significant inhibitory delay period activity for other cue directions. These inhibitory responses were usually strongest for, or centered about, cue directions roughly opposite those optimal for excitatory responses.(ABSTRACT TRUNCATED AT 400 WORDS)
Variance analysis of excitatory postsynaptic potentials in cat spinal motoneurons during posttetanic potentiation
Authors: Clamann H. P. , Mathis J. , Luscher H. R.
Published: December 2017

1. Fluctuations in the peak amplitudes of composite excitatory postsynaptic potentials (EPSPs) in cat spinal motoneurons were analyzed during posttetanic potentiation (PTP). Each of a series of identical tetanic stimulus trains delivered to a muscle nerve was followed by 45 test stimuli applied at 2-s intervals. The mean peak amplitude and mean peak variance were calculated for EPSPs evoked by all those stimuli following a tetanus with the same time interval. It was assumed that the variance arises primarily from the probabilistic all-or-none behavior of single synaptic boutons and background noise due to spontaneous synaptic activity and thermal noise in the recording system. The variance was corrected for the contribution from additive Gaussian background noise. 2. If it is assumed that individual synaptic boutons behave independently, corrected mean peak variance and mean peak amplitude are related by a parabolic function. The expected parabolic relationship was seen in 9 of 31 cases studied, and the parameters of the best parabolic fit to the data allowed estimation of some synaptic properties. From these parameters, the mean amplitude of the unit EPSP (v) was estimated to be 102.1 +/- 57.4 (SD) microV. An average of 3.7 boutons comprised each Ia-motoneuron contact system. 3. On average, only 27% of all synaptic boutons given off by the stimulated Ia fibers to one motoneuron were active and releasing transmitter during unpotentiated reflex transmission. The remaining 73% of the synapse population was intermittently silent. The population of boutons which took part in synaptic transmission could be divided into two subpopulations, one with a release probability P = 1 and a second with a mean release probability P = 0.13 +/- 0.086. 4. We conclude that synaptic boutons connecting Ia afferents to motoneurons exist in two populations, one having a high and one a low probability of transmitter release. Transmitter release is quantal, resulting in a unit EPSP of approximately 100 microV measured at the motoneuron soma.
Acute effects of spinal transection on EPSPs produced by single homonymous Ia-fibers in soleus α-motoneurons in the cat
Authors: Cope T. C. , Hickman K. R. , Botterman B. R.
Published: December 2017

Pages 1678-1694: T. C. Cope, K. R. Hickman, and B. R. Botterman, “Acute effects of spinal transection on EPSPs produced by single homonymous Ia-fibers in soleus agr-motoneurons in the cat.” Page 1692, right column, acknowledgments, the following paragraph should be inserted: Present address of T. C. Cope: Dept. of Physiology and Biophysics, Mail Stop 409, Hahnemann University, Broad and Vine Sts., Philadelphia, PA 19102.

Page 1684, Fig. 3, should appear as follows:

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Anatomic and physiological correlates in bullfrog vestibular nerve
Authors: Honrubia V. , Hoffman L. F. , Sitko S. , Schwartz I. R.
Published: December 2017

1. The correlations between anatomic and physiological characteristics of primary afferent neurons innervating the anterior semicircular canal in the bullfrog were investigated. These characteristics were examined separately in large groups of neurons, and the direct correlations between them were established in a subset of neurons by means of intraaxonal recording and labeling. 2. Anatomic features of the anterior canalicular nerve that were related with fiber diameter were studied. This nerve was composed of an average of 1,142 fibers (standard deviation of 171 in 5 samples), of which 42% were less than 2 microns in diameter and 8% were greater than 7 microns. The nerve branched into 6 clearly defined bundles, whose fiber diameter-dependent composition could be determined in 5 samples. In the 2 center bundles, 32% of the fibers had diameters greater than 7 microns. In contrast, these thick fibers comprised only 4% of the fiber population in the 2 lateralmost bundles, in which 44% of the fibers had diameters less than 2 microns. The projections of labeled afferent fibers were traced into the neuroepithelium, and it was demonstrated that all thick fibers, even those of the lateral bundles, turned toward more central regions of the crista. Consequently, in the bullfrog, there is a clear predominance of thick afferent fibers innervating the anterior crista's central region and thin fibers in the peripheral region. 3. The dendritic morphology of the broad classes of afferent fibers (i.e., thick and thin) was elucidated. Individually labeled thick afferents possessed dendrites forming short, thick, clawlike extensions to contact a few hair cells. The thinnest afferents were labeled through extracellular horseradish peroxidase (HRP) injections. In contrast to the thick fibers, thin afferents were characterized by an unbranched trajectory with serially located bouton-like structures that were apposed to successive hair cells. 4. The characteristics of spontaneous firing and the responses to rotational stimuli were determined for 138 anterior canalicular neurons. Spontaneous firing rates ranged from 0 to 95 spikes.s-1. The coefficient of variation (CV) of spontaneous firing ranged from 0.12 to 2.5. Response gains to high- (0.5 and 0.4 Hz) and medium- (0.05 Hz) frequency sinusoidal acceleration stimuli were positively correlated with CV (P less than 0.001) for neurons with a CV value less than or equal to 0.5. The gain of neurons characterized by more irregular spontaneous firing (CV values greater than 0.5) was uncorrelated with CV.(ABSTRACT TRUNCATED AT 400 WORDS)
Horizontal spread of synchronized activity in neocortex and its control by GABA-mediated inhibition
Authors: Chagnac-Amitai Y. , Connors B. W.
Published: December 2017

1. Suppression of GABAA receptor-mediated inhibition disrupts the neural activity of neocortex and can lead to synchronized discharges that mimic those of partial epilepsy. We have studied the role of GABAA-mediated inhibition in controlling the synchronization and horizontal (tangential) spread of cortical activity. 2. Slices of rat SmI were maintained in vitro and focally stimulated in layer VI while recording with a horizontal array of extracellular electrodes. Inhibition was slightly suppressed by adding low concentrations of the GABAA antagonists bicuculline or bicuculline methiodide to the bathing medium. Under control conditions neural activity was narrowly confined to a vertical strip of cortex. The horizontal spread of activity expanded about twofold in the presence of antagonist concentrations (less than or equal to 0.5 microM) that were expected to suppress GABAA function by no more than 10-20%. 3. At antagonist concentrations between 0.4 and 1.0 microM, evoked epileptiform activity appeared. These threshold-dose epileptiform events showed wide variations in size and duration (even at the same recording site), very variable distances of horizontal propagation, specific sites of propagation failure, reversals of propagation direction, and directional asymmetries in their probability of propagation. This contrasts with activity observed previously (Ref. 9) in high bicuculline concentrations (greater than or equal to 10 microM): large, stereotyped events that propagate reliably without decrement or reflection. 4. Intracellular recordings were obtained from pyramidal neurons in layers II/III in the presence of less than or equal to 1 microM bicuculline. Inhibitory postsynaptic potentials (IPSPs) were observed during both primary evoked responses and propagating epileptiform events and were often comparable in size and duration to those in untreated cortex. Epileptiform field potentials were always correlated with synaptic activity in single cells, but the pattern and type of PSPs varied with the form of the field potentials. Large amplitude epileptiform events coincided with an overwhelming inhibition of upper layer neurons. 5. We conclude that 1) the horizontal spread of normal cortical activity is strongly constrained by GABAA-mediated IPSPs, 2) a relatively small reduction in the efficacy of inhibition leads to a large increase in the spread of excitation, 3) initiation and propagation of synchronized epileptiform activity can occur even in the presence of robust cortical inhibition, and 4) the character of epileptiform activity is strongly affected by the influences of inhibition.
Dynamics of neuronal firing correlation: modulation of "effective connectivity"
Authors: Aertsen A. M. , Gerstein G. L. , Habib M. K. , Palm G.
Published: December 2017

1. We reexamine the possibilities for analyzing and interpreting the time course of correlation in spike trains simultaneously and separably recorded from two neurons. 2. We develop procedures to quantify and properly normalize the classical joint peristimulus time scatter diagram. These allow separation of the "raw" correlation into components caused by direct stimulus modulations of the single-neuron firing rates and those caused by various types of interaction between the two neurons. 3. A newly developed significance test ("surprise") is applied to evaluate such inferences. 4. Application of the new procedures to simulated spike trains allowed the recovery of the known circuitry. In particular, it proved possible to recover fast stimulus-locked modulations of "effective connectivity," even if they were masked by strong direct stimulus modulations of individual firing rates. These procedures thus present a clearly superior alternative to the commonly used "shift predictor." 5. Adopting a model-based approach, we generalize the classical measures for quantifying a direct interneuronal connection ("efficacy" and "contribution") to include possible stimulus-locked time variations. 6. Application of the new procedures to real spike trains from several different preparations showed that fast stimulus-locked modulations of "effective connectivity" also occur for real neurons.
Response properties of single units in the lateral terminal nucleus of the accessory optic system in the behaving primate
Authors: Mustari M. J. , Fuchs A. F.
Published: December 2017

1. To determine the potential role of the primate accessory optic system (AOS) in optokinetic and smooth-pursuit eye movements, we recorded the activity of 110 single units in a subdivision of the AOS, the lateral terminal nucleus (LTN), in five alert rhesus macaques. All monkeys were trained to fixate a stationary target spot during visual testing and to track a small spot moving in a variety of visual environments. 2. LTN units formed a continuum of types ranging from purely visual to purely oculomotor. Visual units (50%) responded best for large-field (70 x 50 degrees), moving visual stimuli and had no response associated with smooth-pursuit eye movement; some responded during smooth pursuit in the dark, but the response disappeared if the target was briefly extinguished, indicating that their smooth-pursuit-related response reflected activation of a parafoveal receptive field. Eye movement and visual units (36%) responded both for large, moving visual stimuli and during smooth-pursuit eye movements made in the dark. Eye movement units (14%) discharged during smooth-pursuit or other eye movements but showed no evidence of visual sensitivity. 3. Essentially all (98%) LTN units were direction selective, responding preferentially during vertical background and/or smooth-pursuit movement. The vast majority (88%) preferred upward background and/or eye movement. During periodic movement of the large-field visual background while the animal fixated, their firing rates were modulated above and below rather high resting rates. Although LTN units typically responded best to movement of large-field stimuli, some also responded well to small moving stimuli (0.25 degrees diam). 4. LTN units could be separated into two populations according to their dependence on visual stimulus velocity. For periodic triangle wave stimuli, both types had velocity thresholds less than 3 degrees/s. As stimulus velocity increased above threshold, the activity of one type reached peak firing rates over a very narrow velocity range and remained nearly at peak firing for velocities from approximately 4-80 degrees/s. The firing rates of the other type exhibited velocity tuning in which the firing rate peaked at an average preferred velocity of 13 degrees/s and decreased for higher velocities. 5. A close examination of firing rates to sinusoidal background stimuli revealed that both unit types exhibited unusual behaviors at the extremes of stimulus velocity.(ABSTRACT TRUNCATED AT 400 WORDS)