bluuebunny/crossref_metadata_2025 huggingface dataset:
Tactile detection of slip: surface microgeometry and peripheral neural codes
Authors: Srinivasan M. A. , Whitehouse J. M. , LaMotte R. H.
Published: December 2017

1. The role of the microgeometry of planar surfaces in the detection of sliding of the surfaces on human and monkey fingerpads was investigated. By the use of a servo-controlled tactile stimulator to press and stroke glass plates on passive fingerpads of human subjects, the ability of humans to discriminate the direction of skin stretch caused by friction and to detect the sliding motion (slip) of the plates with or without micrometer-sized surface features was determined. To identify the associated peripheral neural codes, evoked responses to the same stimuli were recorded from single, low-threshold mechanoreceptive afferent fibers innervating the fingerpads of anesthetized macaque monkeys. 2. Humans could not detect the slip of a smooth glass plate on the fingerpad. However, the direction of skin stretch was perceived based on the information conveyed by the slowly adapting afferents that respond differentially to the stretch directions. Whereas the direction of skin stretch signaled the direction of impending slip, the perception of relative motion between the plate and the finger required the existence of detectable surface features. 3. Barely detectable micrometer-sized protrusions on smooth surfaces led to the detection of slip of these surfaces, because of the exclusive activation of rapidly adapting fibers of either the Meissner (RA) or the Pacinian (PC) type to specific geometries of the microfeatures. The motion of a smooth plate with a very small single raised dot (4 microns high, 550 microns diam) caused the sequential activation of neighboring RAs along the dot path, thus providing a reliable spatiotemporal code. The stroking of the plate with a fine homogeneous texture composed of a matrix of dots (1 microns high, 50 microns diam, and spaced at 100 microns center-to-center) induced vibrations in the fingerpad that activated only the PCs and resulted in an intensive code. 4. The results show that surprisingly small features on smooth surfaces are detected by humans and lead to the detection of slip of these surfaces, with the geometry of the microfeatures governing the associated neural codes. When the surface features are of sizes greater than the response thresholds of all the receptors, redundant spatiotemporal and intensive information is available for the detection of slip.
Pharmacology of the myogenic heart of the pond snail Lymnaea stagnalis
Authors: Buckett K. J. , Dockray G. J. , Osborne N. N. , Benjamin P. R.
Published: December 2017

1. We have used pharmacologic, immunologic, and biochemical techniques to examine the role of neurochemicals in modulating the myogenic heart of the snail, Lymnaea. 2. 5-HT [high-pressure liquid chromatography (HPLC) and immunocytochemistry], dopamine (HPLC), FMRFamide-related peptides (radioimmunoassay and immunocytochemistry) and substance P-related peptides (immunocytochemistry) were shown to be localized within heart tissue. 3. The pharmacologic actions of these substances on the auricle from an isolated heart preparation were examined together with other putative modulators, acetylcholine (ACh), small cardioactive peptides A and B (SCPA and SCPB), [Arg]8vasotocin (AVT), and Lymnaea native FMRFamide-related peptides [Phe-Met-Arg-Phe-NH2 (FMRFamide), Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRFamide) and Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRFamide)]. 4. The response to each substance could be distinguished by different effect on beat rate, amplitude, and diastolic tonus, as well as by the duration of responses to standard 1-min applications. ACh was inhibitory at low concentrations (threshold less than 10(-10) M) but excitatory at high concentrations (10(-6) M). AVT was alone in producing no dose-dependent response. At high concentrations (10(-4) M), AVT caused a massive tonic contraction and cessation of auricle beat. All other substances examined were excitatory. 5. Antagonists to 5-HT (cinanserin), dopamine (ergonovine), and ACh (alpha-bungarotoxin) were identified. 6. ACh, 5-HT, dopamine, and FMRFamide-related peptides all acted on the auricle at low concentrations, and the rapid onset and short duration of their excitatory effects (ACh inhibitory at low concentrations) suggested that they may have roles as neurotransmitters. SCPA and SCPB were also potent (threshold less than 10(-10) M) but produced long-duration responses suggesting a modulatory or hormonal role.
Stiffness regulation by reflex action in the normal human hand
Authors: Carter R. R. , Crago P. E. , Keith M. W.
Published: December 2017

1. The torque and electromyographic (EMG) responses to stretch of the first dorsal interosseous muscle (externally imposed joint rotation) were recorded in five normal human subjects. The total measured stiffness was decomposed into three individual stiffness components; passive, intrinsic, and reflex. 2. The passive component was measured with the subject relaxed. Compared with the total response at the height of short latency reflex action, the passive component comprised 6-32% of the total stiffness recorded at an initial torque level of 20 N-cm [15-39% maximum voluntary contraction (MVC)]. The passive response also reflected a significant acceleration component during rapid joint rotation due primarily to digit inertia. 3. The intrinsic stiffness component, attributed to the mechanical properties of the active muscle fibers, was estimated by recording the response to joint rotation with the muscle activated in a distributed manner using a single intramuscular electrode. The dynamic stiffness (measured at the end of a ramp displacement) and the static stiffness (measured 1 s after onset of the displacement) both scaled in a straight-line manner with the initial torque level. This relationship held whether the initial torque level was varied by changes in recruitment or temporal summation. 4. The reflex component was calculated by subtracting the passive and the estimated intrinsic component from the total response. The timing of the EMG signal recorded during measurement of the total response and the fact that the estimated intrinsic component matched the total active response over the first 65–100 ms after displacement onset supported the case that this was the true reflex component. The peak of the reflex activity occurred 155-360 ms after displacement onset and, at this peak, accounted for 18–44% of the total stiffness (at an initial torque level of 20 N-cm). 5. Over the low to intermediate torque range employed, we observed that both intrinsic muscle stiffness and total stiffness increased with initial torque. Because total stiffness increased more rapidly than intrinsic stiffness, the difference between them (equal to reflex stiffness) also increased with initial torque. Furthermore, when the total active response trials (passive stiffness removed) were shifted vertically so that the initial torque levels matched, it was seen that reflex action did not reduce the stiffness range to less than the stiffness range encountered for the intrinsic response alone.(ABSTRACT TRUNCATED AT 400 WORDS)
Operational unit responsible for plane-specific control of eye movement by cerebellar flocculus in cat
Authors: Sato Y. , Kawasaki T.
Published: December 2017

1. Main findings in our previous studies are as follows: 1) there are three Purkinje cell zones running perpendicular to the long axis of the folia in the cat flocculus, 2) the caudal zone controls activity of the superior rectus (SR) and inferior oblique (IO) extraocular muscles via the y-group and oculomotor nucleus (OMN) neurons, and 3) the middle zone controls activity of the lateral (LR) and medial rectus (MR) muscles via the medial vestibular (MV) and abducens nucleus (ABN) neurons. In the present study, the neuronal pathways from the remaining rostral zone were investigated in the anesthetized cat. 2. Target neurons of rostral zone inhibition in the superior vestibular nucleus (SV) were identified by observing cessation of spontaneous discharges after rostral zone stimulation. Efferent projections were studied by the use of systematic microstimulation techniques. Unitary responses to stimulation of the eighth nerves were also investigated. 3. There are two types of the target neurons: 1) those, being located in the central and dorsal parts of the SV, project to the trochlear and oculomotor nuclei innervating superior oblique and inferior rectus muscles via the ipsilateral medial longitudinal fasciculus (MLF); and 2) those, being located along the dorsal border of the SV, project to the contralateral oculomotor nucleus innervating superior rectus and inferior oblique muscles via the extra-MLF route. 4. Both types receive monosynaptic anterior canal nerve input but not posterior canal nerve input. Some neurons receive polysynaptic excitatory input from the contralateral eighth nerve, although commissural inhibition was never observed. 5. From neuronal connections of the rostral and caudal zones and action of the extraocular muscles, it was expected that 1) activity changes of Purkinje cells in the rostral and/or caudal zones on one side resulted in conjugate eye movement in the plane of the anterior canal on the side of the activity changes, 2) cooperative increased activity on both sides resulted in conjugate downward eye movement, and 3) increased activity on one side and decreased activity on the other side resulted in conjugate rotatory eye movement. The rostral and caudal zones may be responsible for eye-movement control in the sagittal plane by cooperative activity changes on both sides and in the transverse plane by reciprocal activity changes on both sides. For eye-movement control in the anterior canal plane, Purkinje cell activity on one side would be sufficient to produce the required movement. In a functional sense, we call the rostral and caudal zones, the vertical-plane zones.(ABSTRACT TRUNCATED AT 400 WORDS)
Computer simulation of group Ia EPSPs using morphologically realistic models of cat alpha-motoneurons
Authors: Segev I. , Fleshman J. W. , Burke R. E.
Published: December 2017

1. Morphological and electrophysiological data on the electrotonic structure of six triceps surae alpha-motoneurons and on the number and location of 202 Group Ia synapses making contact with ankle extensor motoneurons, previously obtained in this laboratory, were used to construct computer models to examine the generation of composite monosynaptic Group Ia excitatory postsynaptic potentials (EPSPs). 2. A total of 300 active synapses, each generating conductance transients based on voltage-clamp data and having activation times temporally dispersed (range approximately 1.3 ms) according to the conduction velocity profile of Group Ia-afferents, were used to generate composite EPSPs. 3. The shape indexes (foot-to-peak rise times and half widths) of simulated EPSPs matched those of experimentally observed Ia EPSPs reasonably well, although the rise times were, on average, approximately 0.25 ms longer in the simulated EPSPs. This may indicate that the effective temporal dispersion of actual Group Ia monosynaptic EPSPs is less than that the temporal asynchrony used in the simulations. 4. The peak amplitudes of simulated composite EPSPs (6-14 mV), as well as EPSPs produced by single somatic synapses (80-300 microV), were comparable to those found in experimental data. 5. Simulated EPSPs in motoneuron models with two forms of nonuniform Rm distribution ("step" increase from low values of Rm on the soma to much higher but uniform values in the dendrites, versus gradual monotonic "sigmoidal" increases from soma to distal dendrites) were similar in shape and amplitude. This prevented choosing one or the other Rm model as more "correct." 6. Transmembrane voltages at synaptic sites in motoneuron dendrites during generation of composite Ia EPSPs had peak amplitudes less than twice those of the somatic EPSP. The amount of nonlinearity during EPSP production was assessed by making the delivery of synaptic current independent of the local transmembrane voltage. This non-linearity was modest (less than 10%) during composite EPSP generation, consistent with previous experimental evidence. 7. The local voltages produced in various parts of different dendrites during composite EPSP generation depended on the number and location of active synapses and on the electrotonic structure of the particular dendrite. The results show that dendrites that project in different directions away from the motoneuron soma could, in principle, exhibit different degrees of interaction between Ia and other synaptic inputs. 8. Although produced by the same number of active synapses, the simulated composite Ia EPSPs varied over a two-fold range of peak amplitude in relation to motor-unit type, cell input resistance, and cell size (total membrane area).(ABSTRACT TRUNCATED AT 400 WORDS)
Stimulus-response function studies of esophageal mechanosensitive nociceptors in sympathetic afferents of opossum
Authors: Sengupta J. N. , Saha J. K. , Goyal R. K.
Published: December 2017

1. Single-unit activity was recorded from afferent fibers in either the paravertebral sympathetic chain or the splanchnic nerves. Forty-three fibers that responded to distension of the smooth-muscle portion of esophagus were selected for further study. 2. Out of the 43 fibers, 27 (62%) had ongoing resting activity, and 16 (38%) were silent. The mean resting activity of these fibers was 0.28 +/- 0.06 imp/s (range, 0-2.6 imp/s). 3. Repeated distensions of the esophagus to a fixed pressure (80 mmHg) evoked spike discharge at a reproducible rate. There was no evidence of facilitation or inhibition of subsequent responses. The mean coefficient of variation (CV) was 0.17 +/- 0.05 imp/s (n = 5). 4. The stimulus-response function (SRF) to intraluminal graded distension was studied in 35 fibers. Thirty-three fibers showed linear increase in firing that did not saturate up to 120 mmHg. Two fibers reached maximal discharge rate at 60 mmHg. The mean discharge rate at 120 mmHg pressure was 14.87 +/- 1.52 imp/s. 5. Threshold pressure for activation of each fiber was calculated by a least-squares linear-regression plot of the SRF. The threshold pressure varied from 0 to 50 mmHg (mean, 16.21 +/- 2.86 mmHg). The distribution profile of the threshold values showed that there were two separate populations of mechanosensitive receptors: 1) wide-dynamic-range mechanonociceptors (WDR-MN) with mean threshold pressure of 2.89 +/- 0.75 mmHg (range, 0-7 mmHg; n = 22); and 2) high-threshold mechanonociceptors (HT-MN) with mean threshold of 33.26 +/- 2.52 mmHg (range, 19-50 mmHg; n = 13). 6. Discharge evoked by esophageal peristalsis was studied in five WDR-MN and five HT-MN units. Whereas all five WDR-MN units (threshold value, 2.6 +/- 0.96 mmHg) responded to peristalsis, none of the HT-MN units (threshold value, 31.2 +/- 4.01 mmHg) did so. The mean response to peristaltic contraction in WDR-MN units was 5.32 +/- 1.36 imp/s, which was 24.7% of the maximal response (21.53 +/- 1.92 imp/s; n = 5) at 120 mmHg. The duration of evoked response to peristaltic contraction was 10-12 s. 7. The activity profile of the units to 60-s balloon distension at near threshold and higher pressures showed three patterns: 1) rapid adaptation, 2) slow adaptation, and 3) slow adaptation with after discharge. The rapidly adapting fibers became slowly adapting with greater degrees of esophageal distension. The units that showed rapid or slow adaptation at low-distension pressure became indistinguishable from one another at high-distension pressure.(ABSTRACT TRUNCATED AT 400 WORDS)
Forcing of coupled nonlinear oscillators: studies of intersegmental coordination in the lamprey locomotor central pattern generator
Authors: Williams T. L. , Sigvardt K. A. , Kopell N. , Ermentrout G. B. , Remler M. P.
Published: December 2017

1. This paper reports the results of an investigation of the basic mechanisms underlying intersegmental coordination in lamprey locomotion, by the use of a combined mathematical and biological approach. 2. Mathematically, the lamprey central pattern generator (CPG) is described as a chain of coupled nonlinear oscillators; experimentally, entrainment of fictive locomotion by imposed movement has been investigated. Interpretation of the results in the context of the theory has allowed conclusions to be drawn about the nature of ascending and descending coupling in the lamprey spinal CPG. 3. Theory predicts and data show that 1) the greater the number of oscillators in the chain, the smaller is the entrainment frequency range and 2) it is possible to entrain both above and below the rest frequency at one end but only above or below at the other end. 4. In the context of the experimental results, the theory indicates the following: 1) ascending coupling sets the intersegmental phase lags, whereas descending coupling changes the frequency of the coupled oscillators; 2) there are differences in the ascending and descending coupling other than strength; and it also suggests that 3) coupling slows down the oscillators.
Muscarinic depression of synaptic transmission at the hippocampal mossy fiber synapse
Authors: Williams S. , Johnston D.
Published: December 2017

1. The action of muscarine was studied in the CA3 region of the rat hippocampal slice with single-electrode voltage-clamp techniques. 2. Bath application of 1 or 10 microM muscarine produced an increase in the input resistance of these cells and reduced the slow afterhyperpolarization (sAHP) response. Changes in input resistance were more pronounced around the resting potential of the cell (-50 to -60 mV), but in many cells an effect was also seen at -80 mV. These effects were absent when cesium chloride-containing microelectrodes were used. 3. At 1 microM, muscarine had little effect on synaptic transmission, causing a 0 +/- 7% (mean +/- SE, n = 19) change in excitatory postsynaptic potential (EPSP) and decreasing the excitatory postsynaptic current (EPSC) by 11 +/- 6% (n = 14); neither change was statistically significant. 4. In contrast, 10 microM muscarine produced a reliable depression of both the EPSP and EPSC. This effect was independent of the electrolyte used: with KCl the EPSP was depressed 23 +/- 4% (n = 5) and the EPSC 35 +/- 5% (n = 4); for CsCl the EPSP was depressed 23 +/- 10% (n = 7) and the EPSC 34 +/- 5% (n = 7). 5. Muscarine did not alter the reversal potential of the synaptic current but merely produced a decrease in slope conductance (37 +/- 5%, n = 6). 6. Muscarine did not significantly alter the shape of the EPSC waveform. This was assessed by comparing the 10-90% rise time and the half decay time of the current before and after muscarine.(ABSTRACT TRUNCATED AT 250 WORDS)
Cutaneous stimulation evokes long-lasting excitation of spinal interneurons in the turtle
Authors: Currie S. N. , Stein P. S.
Published: December 2017

1. We demonstrated multisecond increases in the excitability of the rostral-scratch reflex in the turtle by electrically stimulating the shell at sites within the rostral-scratch receptive field. To examine the cellular mechanisms for these multisecond increases in scratch excitability, we recorded from single cutaneous afferents and sensory interneurons that responded to stimulation of the shell within the rostral-scratch receptive field. A single segment of the midbody spinal cord (D4, the 4th postcervical segment) was isolated in situ by transecting the spinal cord at the segment's anterior and posterior borders. The isolated segment was left attached to its peripheral nerve that innervates part of the rostral-scratch receptive field. A microsuction electrode (4-5 microns ID) was used to record extracellularly from the descending axons of cutaneous afferents and interneurons in the spinal white matter at the posterior end of the D4 segment. 2. The turtle shell is innervated by slowly and rapidly adapting cutaneous afferents. All cutaneous afferents responded to a single electrical stimulus to the shell with a single action potential. Maintained mechanical stimulation applied to the receptive field of some slowly adapting afferents produced several seconds of afterdischarge at stimulus offset. We refer to the cutaneous afferent afterdischarge caused by mechanical stimulation of the shell as "peripheral afterdischarge." 3. Within the D4 spinal segment there were some interneurons that responded to a brief mechanical stimulus within their receptive fields on the shell with short afterdischarge and others that responded with long afterdischarge. Short-afterdischarge interneurons responded to a single electrical pulse to a site in their receptive fields either with a brief train of action potentials or with a single action potential. Long-afterdischarge interneurons responded to a single electrical shell stimulus with up to 30 s of afterdischarge. Long-afterdischarge interneurons also exhibited strong temporal summation in response to a pair of electrical shell stimuli delivered up to several seconds apart. Because all cutaneous afferents responded to an electrical shell stimulus with a single action potential, we conclude that electrically evoked afterdischarge in interneurons was produced by neural mechanisms in the spinal cord; we refer to this type of afterdischarge as "central afterdischarge." 4. These results demonstrate that neural mechanisms for long-lasting excitability changes in response to cutaneous stimulation reside in a single segment of the spinal cord. Cutaneous interneurons with long afterdischarge may serve as cellular loci for multise
Neuronal responsiveness in the ventrobasal thalamic complex of rats with an experimental peripheral mononeuropathy
Authors: Guilbaud G. , Benoist J. M. , Jazat F. , Gautron M.
Published: December 2017

1. Single-unit recordings were made, under moderate gaseous anesthesia (33% O2-66% N2O + 0.5/0.6% halothane), in the ventrobasal (VB) thalamic complex of rats (n = 42) with a mononeuropathy created 2-3 wk beforehand, by four loose ligatures around the common sciatic nerve. Before the recording session, three behavioral nociceptive tests to both mechanical and thermal stimuli revealed that these rats exhibited clear hyperalgesia (excessive reactions to noxious stimuli) and allodynia (nociceptive reactions to stimuli usually perceived as nonnoxious). 2. Neurons, characterized by their responses to manual mechanical stimuli, were classified into two groups: group 1 neurons exclusively driven by light tactile stimuli applied to the receptive field (RF), strictly contralateral to the recording site; and group 2 neurons, driven by sustained pinch applied to a large RF, often bilateral. 3. From the total population of neurons (n = 386), only those responding to stimuli applied to one posterior paw were studied; the proportion (35-40%) of these cells was comparable in each of the two VB: n = 93/262 and 44/124 in the VB contralateral (VBc) and ipsilateral (VBi) to the damaged nerve, respectively. The proportions of each functional group of neurons (group 1 or 2) were also similar on each side. 4. For all group 1 neurons the RFs size was comparable to that observed in normal rats. In the VBi the responses of these neurons presented the classical response pattern observed for VB neurons involved in touch transmission, as did the VBc group 1 neurons with RFs in the saphenous (Sa) territory. In sharp contrast, activities of VBc group 1 neurons with RFs in the sciatic (Sc) nerve territory exhibited several abnormalities: higher background activity, fading of the response with repetitive stimulation, and afterdischarges outlasting the applied stimulus. 5. As in normal rats, 52% of VB group 2 neurons exhibited bilateral symmetrical RFs. Their responses to mechanical stimuli were often greater for stimuli applied to the affected paw, and some of them could be activated by moderate pressure to this paw. Heat responses also illustrated the profound increased sensitivity of the lesioned side, and the activation threshold to thermal stimulation of these group 2 neurons was lowered by 4-6 degrees C compared to normal values. In addition, these neurons responded to immersion of the lesioned paw in a 10 degrees C water bath, a stimulus that was ineffective when applied to the opposite paw.(ABSTRACT TRUNCATED AT 250 WORDS)
Factors determining segmental reflex action in normal and decerebrate cats
Authors: Sinkjaer T. , Hoffer J. A.
Published: December 2017

1. In the companion paper the gain of the stretch reflex in the ankle extensor muscles of normal cats was shown to increase after decerebration. The objectives of this study were 1) to identify the origin of the increased reflex and 2) to evaluate the contribution from afferents other than ankle extensor muscle afferents to the short-latency reflex. 2. Six cats were trained to stand unaided on four pedestals. Three cats were also trained to control the force exerted with the left hindlimb. The left soleus (SOL) and lateral gastrocnemius (LG) electromyogram (EMG), length, force, and temperature were recorded by chronically implanted electrodes and transducers. Measurements were taken before and after decerebration at the premammillary level. After decerebration limb temperature was returned to its normal range by the use of radiant heat. 3. Reproducible ramp-and-hold stretches and releases of the ankle extensor muscles were produced by a servo-controlled motor that rotated the left rear pedestal about the ankle joint. The length of the ankle extensor muscles changed by 2-3 mm within 30-35 ms after the onset of a ramp perturbation. Reflex responses before and after decerebration were compared at matched background values of muscle length and force. 4. In both the SOL and LG muscles, a short-latency EMG burst appeared 8-12 ms after stretch onset and lasted approximately 20 ms. After decerebration the onset of the rectified and smoothed EMG burst remained unchanged, but its area was increased by 36-89%. 5. The lateral gastrocnemius-soleus (LG-S) electroneurogram (ENG) was chronically recorded in two cats with a nerve cuff recording electrode implanted on the LG-S nerve. LG-S ENG activity started to increase soon after stretch onset and remained high during the entire ramp phase. The stretch-evoked LG-S ENG burst started approximately 8 ms earlier than the short-latency SOL and LG EMG bursts. It was interpreted to reflect mainly an increase in the activity of Group Ia and Ib muscle afferents, caused by increases in both muscle length and muscle force during the stretch. After the cats were decerebrated, for matched postural conditions, the area of the stretch-evoked LG-S ENG burst was increased by 29-35%. Because the length and force changes sensed by the muscle receptors before and after decerebration were similar, this suggests that the sensitivity of muscle spindles was increased as a consequence of altered activity in fusimotor neurons after decerebration.(ABSTRACT TRUNCATED AT 400 WORDS)
Neural Mechanisms Underlying the Clasp-Knife Reflex in the Cat: II. Stretch-Sensitive Muscular-Free Nerve Endings.
Authors: Cleland C. L. , Hayward L. , Rymer W. Z.
Published: December 2017

C. L. Cleland, L. Hayward, and W. Z. Rymer, page 1319, the title of the article should read:,Neural Mechanisms Underlying the Clasp-Knife Reflex in the Cat. II. Stretch-Sensitive Muscular Free Nerve Endings.-The running head should read:,properties of muscular free nerve endings.-
Activity of identified wrist-related pallidal neurons during step and ramp wrist movements in the monkey
Authors: Hamada I. , DeLong M. R. , Mano N.
Published: December 2017

1. The activity of globus pallidus (GP) neurons (n = 1,117) was studied in two monkeys to reexamine the relation of neuronal activity to movement type (slow vs. fast) while they performed both a visually guided step and ramp wrist tracking task. To select neurons specifically related to wrist movements, we employed both a somatosensory examination of individual body parts and a statistical analysis of the strength of temporal coupling of neuronal discharges to active wrist movement. 2. Neuronal responses to somatosensory stimulation were studied in 1,000 high-frequency GP neurons, of which 686 exhibited clear responses to manipulation of body parts. Of the latter, 336 responded to passive manipulation of forelimb joints and 58 selectively to passive flexion or extension of the wrist. 3. In the external segment of GP (GPe), most neurons responding to passive wrist movement were found to be clustered in four to five adjacent, closely positioned (separated by 200 microns) tracks in single coronal planes. The clusters were irregular in shape with a maximal width of 800-1,000 microns. Separate clusters of neurons responsive to passive wrist movement were identified in planes 3 mm apart in one monkey and in planes 500 microns apart in the other. Multiple clusters of neurons were also found for neurons responsive to joints other than the wrist. These findings suggest a more discrete and complex representation of individual joints in the primate GP than previously conceived. 4. During the performance of the wrist flexion and extension task, 92 neurons showed clear and consistent changes in activity. For these neurons we measured, with a statistical method on a trial-by-trial basis, the strength of temporal coupling between the onset of active wrist movement and the onset of change in neuronal discharge rate. Fifteen neurons showed changes in activity time-locked to the onset of active wrist movement. 5. Twelve pallidal neurons were classified as “wrist-related” based on their movement-locked changes in discharge during task performance and their clear responses to passive wrist joint rotation on examination. All of these neurons exhibited statistically significant modulation of their discharge rate during both fast (peak velocity 97–205 degrees/s) and slow (peak velocity 20–62 degrees/s) wrist movements in the task. The amplitudes of modulation were larger during fast wrist movement than slow movement. These results suggest that the basal ganglia motor circuit plays a similar, rather than an exclusive, role in the control of slow and fast limb movements.
Intracellular measurements from a rapidly adapting sensory neuron
Authors: Basarsky T. A. , French A. S.
Published: December 2017

1. The femoral tactile spine of the cockroach contains a single sensory neuron with its cell body in the lumen of the spine. Step movements of the spine produce rapidly adapting bursts of action potentials that decay to 0 in 1 s. Previous work has shown that a large part of this adaptation occurs during action potential encoding. 2. Intracellular recordings from the tactile spine neuron were obtained by lowering a microelectrode through the spine lumen and penetrating the cell body. Injection of Lucifer yellow followed by fluorescence microscopy confirmed the morphology of the soma, with a diameter of 30 microns, and showed an axon of 9 microns leaving the spine and proceeding proximally along the femur. 3. Membrane-potential records were digitized and examined at high resolution during bursts of action potentials produced by depolarizing current pulses. No significant changes in action potential shape were detected during adaptation. However, the rate of depolarization between action potentials slowed dramatically during the burst. This slowing could be reduced and the burst substantially prolonged by chloramine-T (CT), an agent that reduces sodium channel inactivation in several preparations. 4. A 100 Hz sinusoidal current was superimposed on depolarizing current pulses to test for changes in membrane conductance during a burst of action potentials. No such changes were detected, indicating that rapid adaptation is not due to changes in membrane permeability.(ABSTRACT TRUNCATED AT 250 WORDS)
Microcircuitry related to the receptive field center of the on-beta ganglion cell
Authors: Cohen E. , Sterling P.
Published: December 2017

1. We have investigated the anatomic basis for the Gaussian-like receptive field center of the on-beta ("X") ganglion cell in the area centralis of cat retina. Three adjacent on-beta cells were reconstructed from electron micrographs of 279 serial sections cut vertically through a patch of retina at approximately 1 degree eccentricity. 2. All the bipolar synapses on these cells were identified, and about one-half of these were traced to type b1 bipolar cells, which formed a regular array in the plane of the retina. 3. On average, seven b1 cells contributed to a beta cell: bipolar axons near the middle of the beta dendritic field tended to give many contacts (12-33 contacts); axons near the edge of the field tended to give few contacts (3-4 contacts). 4. Each b1 cell collected from four to seven cones, and the mean number of cones converging through the b1 array to a beta cell was 30. 5. Assuming equal effectiveness for all b1----beta cell synapses, a spatial weighting function was derived from these results. The mean radius of this function at 1/e amplitude for three beta cells was 18.0 +/- 1.1 (SD) microns. This is considerably narrower than the corresponding measurements of the beta cell receptive field center (28 +/- 3 microns) at this eccentricity. 6. It is concluded, in agreement with previous work, that all cones encompassed by the beta cell's dendritic field and those slightly beyond it connect directly to the beta cell via the b1 bipolar cell array. However, the center of the beta cell receptive field is still broader by approximately 60%. This suggests that pooling of cone signals may occur at the level of the outer plexiform layer.
Role of excitatory amino acids in mediating burst discharge of red nucleus neurons in the in vitro turtle brain stem-cerebellum
Authors: Keifer J. , Houk J. C.
Published: December 2017

1. Bursts of discharge have been recorded in the red nucleus in several species and are thought to represent the expression of motor commands. A cerebellorubral circuit comprised of recurrent connections among the cerebellum, red nucleus, and reticular formation was postulated to function as a positive feedback loop that generates these motor commands and transmits them to the spinal cord via the rubrospinal pathway. We have used an in vitro preparation from the turtle that leaves the circuitry connecting the cerebellum, brain stem, and spinal cord intact to study the role of excitatory amino acid neurotransmitters and recurrent excitation in mediating the generation of burst discharges in the red nucleus. 2. Burst discharges were recorded extracellularly from single cells in the red nucleus in response to single pulse or brief train stimulation of the contralateral spinal cord or brief train stimuli applied to the ipsilateral cerebellar cortex. The firing characteristics and pharmacologic sensitivities of the bursts were independent of the type of stimulus used. The bursts had long durations ranging from 2 to 17 s and showed spike frequency adaptation. 3. Transection of the cerebellar peduncle, which eliminates inhibition impinging onto the cerebellorubral circuit, greatly enhanced the spontaneous activity and burst discharges recorded in the contralateral red nucleus. Furthermore, bath application of a solution containing elevated levels of calcium and magnesium blocked the expression of burst discharges even though synaptic activation of the neurons was not blocked. 4. The possibility that excitatory amino acid receptors mediate burst responses in the red nucleus was investigated in light of the antagonistic effects of elevated magnesium ions on bursting. Bath application of 100 microns DL-2-amino-5-phosphonovaleric acid (APV), a specific N-methyl-D-aspartate (NMDA) receptor antagonist; [10 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)], a specific non-NMDA receptor antagonist; or 100 microM, DL-2-amino-4-phosphonobutyric acid (AP4), an agonist of a fourth class of excitatory amino acid receptor, blocked burst activity in the red nucleus. With a multibarreled pipette for simultaneous ejection of drug and recording, iontophoresis of APV or CNQX into the red nucleus blocked bursting whereas AP4 failed to show a significant effect. These data suggest that red nucleus neurons have both NMDA and non-NMDA receptors. The site of action of the AP4-sensitive receptor appears to be elsewhere in the cerebellorubral circuit. 5. Iontophoretic application of excitatory amino acid receptor agonists NMDA and quisqualate (Q) induced excitation of red nucleus neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
Finger movement responses of cutaneous mechanoreceptors in the dorsal skin of the human hand
Authors: Edin B. B. , Abbs J. H.
Published: December 2017

1. The movement sensitivity of dorsal skin mechanoreceptors in the human hand was studied by the use of single afferent recording techniques. 2. Units were classified as slowly (SA) and fast adapting (FA) and further characterized by thresholds to vertical indentation and by receptive-field sizes. Whereas SA units were evenly distributed within the supply area of the superficial branch of the radial nerve. FA units were usually situated near joints. 3. The proportion of different receptor types (32% SAI, 32% SAII, 28% FAI, 8% FAII; n = 107) compared favorably with previous electrophysiological and anatomic data, arguing for minimal sampling bias. The majority of the skin mechanoreceptive units were SA, largely due to a relative scarcity of FAII [Pacinian corpuscles (PC)] units. 4. A large majority (92%) of the afferents responded to active hand or finger movements. Responses in all unit types were consistent with observed movement-induced deformations of their receptive fields. 5. FAI units responded bidirectionally, albeit usually with somewhat higher discharge frequencies for finger flexion, which in most cases were associated with skin stretch. FAI units showed meager responses to remote stimuli, typically responding to one or, at the most, two adjacent joints. 6. SA units typically showed simple directional responses to joint movements with an increased discharge during flexion and a reduced discharge during extension. Joint movement that influenced the skin within the receptive field of SA units elicited graded responses even if the field, as assessed by perpendicular indentations, was minute. This finding suggests that definition of cutaneous receptive fields by classical perpendicular indentations may be inappropriate for the receptors in the hairy, nonglabrous skin. 7. The interpretation of the data from these recordings suggests that cutaneous mechanoreceptors in the dorsal skin can provide the CNS with detailed kinematic information, at least for movements of the hand.
Characterization of the electroantennogram in Drosophila melanogaster and its use for identifying olfactory capture and transduction mutants
Authors: Alcorta E.
Published: December 2017

1. Amplitude as well as time course of the electroantennogram (EAG) in Drosophila has been used for describing electrical changes produced in the antenna in response to odorous stimulation. 2. Maximal amplitude of response appears to be directly correlated to stimulus concentration but, after achieving a maximum value, is independent of stimulation duration. 3. Rise time and fall time constants have been quantified for describing kinetics of response. The rise time constant decreases, but the fall time constant increases when increasing concentrations of odorant are supplied. 4. Variation among individuals for these EAG parameters is small enough to uncover even partial defects affecting the first sensory step. This fact combined with the possibility of obtaining mutants with defects in any intermediate process producing the electrical response makes the EAG of Drosophila a very useful tool for dissecting the components of the capture and transduction processes in the olfactory sense. 5. This kind of quantitative study of the EAG has been used in a new Drosophila mutant, od A, for localizing peripheral expression of the mutation. od A has been isolated as a behavioral mutant with an abnormally enhanced olfactory response to ethyl acetate. 6. The mutant's EAG in response to this odorant displays a normal amplitude but abnormal kinetics. Rise time as well as fall time show slower kinetics than normal, suggesting some defective step in the capture and transduction process.
Physiology and pharmacology of epileptiform activity induced by 4-aminopyridine in rat hippocampal slices
Authors: Perreault P. , Avoli M.
Published: December 2017

1. Conventional intracellular and extracellular recording techniques were used to investigate the physiology and pharmacology of epileptiform bursts induced by 4-aminopyridine (4-AP, 50 microM) in the CA3 area of rat hippocampal slices maintained in vitro. 2. 4-AP-induced epileptiform bursts, consisting of a 25-to 80-ms depolarizing shift of the neuronal membrane associated with three to six fast action potentials, occurred at the frequency of 0.61 +/- 0.29 (SD)/s. The bursts were generated synchronously by CA3 neurons and were triggered by giant excitatory postsynaptic potentials (EPSPs). A second type of spontaneous activity consisting of a slow depolarization also occurred but at a lower rate (0.04 +/- 0.2/s). 3. The effects of 4-AP on EPSPs and inhibitory postsynaptic potentials (IPSPs) evoked by mossy fiber stimulation were studied on neurons impaled with a mixture of K acetate and 2(triethyl-amino)-N-(2,6-dimethylphenyl) acetamide (QX-314)-filled microelectrodes. After the addition of 4-AP, the EPSP became potentiated and was followed by the appearance of a giant EPSP. This giant EPSP completely obscured the early IPSP recorded under control conditions and inverted at -32 +/- 3.9 mV (n = 4), suggesting that both inhibitory and excitatory conductances were involved in its generation. IPSPs evoked by Schaffer collateral stimulation increased in amplitude and duration after 4-AP application. 4. The spontaneous field bursts and the stimulus-induced giant EPSP induced by 4-AP were not affected by N-methyl-D-aspartate (NMDA) receptor antagonists 3-3 (2-carboxy piperazine-4-yl) propyl-1-phosphonate (CPP) and DL-2-amino-5-phosphonovalerate (APV) but were blocked by quisqualate/kainate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitroquinoxaline-2,3-dione (DNQX). CNQX also abolished the presence of small spontaneously occurring EPSPs, thereby disclosing the presence of bicuculline-sensitive (BMI, 20 microM) IPSPs. 5. Small, nonsynchronous EPSPs played an important role in the generation of 4-AP-induced epileptiform activity. 1) After the addition of 4-AP, small EPSPs appeared randomly on the baseline and then became clustered to produce a depolarizing envelope of irregular shape that progressively formed an epileptiform burst, 2) These small EPSPs were more numerous in the 100 ms period that preceded burst onset. 3) The frequency of occurrence of small EPSPs was positively correlated with the frequency of occurrence of synchronous bursts. 4) Small EPSPs and bursts were similarly decreased after the addition of different concentrations of CNQX (IC50 in both cases of approximately 1.2 microM).(ABSTRACT TRUNCATED AT 400 WORDS)
Differential distribution of excitatory amino acid receptors on embryonic rat spinal cord neurons in culture
Authors: Arancio O. , MacDermott A. B.
Published: December 2017

1. Excitatory amino acid (EAA) receptors mediate synaptic transmission in many areas of the vertebrate CNS. To map the distribution of the EAA receptors, three agonists selective for EAA receptor subtypes [kainate, quisqualate, and N-methyl-D-aspartate (NMDA)] were applied by pressure to the cell bodies and neurites of voltage-clamped, embryonic rat spinal cord neurons in culture. 2. Current loss along the neurite between the site of activation and the recording electrode at the soma was estimated independently of variations in receptor density by focal application of high [K+] solution. This estimate was used to compensate agonist-evoked responses for current loss due to leak. K(+)-evoked current amplitudes progressively decreased as applications were made at more distal positions along the neurite. 3. Response amplitudes to EAAs showed a monotonic decay, similar to that with high [K+] solution, in only a few of the cells tested with each agonist. The majority of neurons had areas of high agonist sensitivity along the neurites, implying a nonuniform density of receptors. Such regions sometimes occurred at the most proximal segment of the neurite. Most neurites had distal regions of agonist sensitivity that ranged from 40 to 300% higher than at the soma. 4. The relative distributions of the three EAA receptors were compared by applying two agonists to the same sites along neurites and observing variations in normalized response amplitudes. When comparing NMDA versus non-NMDA receptor distributions on the same neurite, approximately 40% of the cells had similar patterns to two agonists, and the remaining 60% had different patterns. When sensitivity to the two non-NMDA agonists kainate and quisqualate were compared, about one-half of the cells tested had different patterns of agonist sensitivity. 5. Areas of high sensitivity persisted after block of calcium channels by addition of La3+ to the bath solution and after prevention of evoked transmitter release by a low [Ca2+]/high [Mg2+] solution. 6. These results show that spinal cord neurons can have regions of high agonist sensitivity to NMDA, kainate, and quisqualate along their neurites and that the sensitivity to any one of the EAA receptor subtypes can be elevated independently of the others.
Area 18 corticotectal cells: response properties and identification of sustaining geniculate inputs
Authors: Weyand T. G. , Malpeli J. G. , Lee C.
Published: December 2017

1. We examined the response properties and geniculate inputs of 35 antidromically identified corticotectal (CT) cells within area 18 of the paralyzed, anesthetized cat. Twenty-three were either standard complex or hypercomplex, 11 were special complex, and 1 was simple. 2. The response properties of CT cells in area 18 were in general quite similar to those examined in a previous study of area 17 CT cells, including similar proportions of standard and special complex CT cells, virtually identical length-response functions, and similar orientation and direction tuning. 3. Area 18 CT cells are rapidly conducting. They are considerably faster than area 17 CT cells. 4. We investigated the composition of thalamic inputs to CT cells by reversibly inactivating a portion of layer A and/or the C layers of the dorsal lateral geniculate nucleus with injections of cobaltous chloride. Blocking layer A strongly attenuated the visual responsiveness of about half of the cells tested. Blocking the C layers alone generally had only moderate effects, but simultaneous blockade of layer A and the C layers demonstrated a substantial C-layer input to many cells. Unlike area 17 in which there is a strong correlation between CT cell class and dependence on layer A, no single receptive-field parameter nor set of parameters was correlated with dependence on layer A. However, cells least affected by simultaneous blockade of layer A and the C layers were special complex, suggesting that, as in area 17, area 18 special complex CT cells integrate more geniculate inputs than standard complex CT cells. 5. We propose that the similarities of response properties of area 17 and area 18 CT cells results from their participation in similar interlaminar columnar circuits and that differences in the patterns of geniculate control reflect differences in the global patterns of geniculate inputs to these two areas.