bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative studies of single-cell properties in monkey striate cortex. IV. Corticotectal cells
Authors: Finlay B. L. , Schiller P. H. , Volman S. F.
Published: December 2017

1. The receptive-field properties of corticotectal cells in the monkey's striate cortex were studied using stationary and moving stimuli. These cells were identified by antidromic activation from the superior colliculus. 2. Corticotectal cells form a relatively homogeneous group. They are found primarily in layers 5 and 6. These cells can usually be classified as CX-type cells but show broader orientation tuning, larger receptive fields, higher spontaneous activity, and greater binocular activation than CX-type cells do in general. A third of the corticotectal cells were direction selective. 3. These results suggest that the cortical input to the superior colliculus is not directly responsible for the receptive-field properties of collicular cells. We propose that this input has a gating function in contributing to the control of the downflow of excitation from the superficial to the deep layers of the colliculus.
Quantitative studies of single-cell properties in monkey striate cortex. V. Multivariate statistical analyses and models
Authors: Schiller P. H. , Finlay B. L. , Volman S. F.
Published: December 2017

1. Several statistical analyses were performed on 205 S-type and CX-type cells which had been completely analyzed on 12 response variables: orientation tuning, end stopping, spontaneous activity, response variability, direction selectivity, contrast selectivity for flashed or moving stimuli, selectivity for interaction of contrast and direction of stimulus movement, spatial-frequency selectivity, spatial separation of subfields responding to light increment of light decrement, sustained/transient response to flash, receptive-field size, and ocular dominance. 2. Correlation of these variables showed that within any cell group, these response variables vary independently. 3. A multivariate discriminant analysis showed that orientation specificity, receptive-field size, interaction of direction and contrast specificity ocular dominance, and spontaneous activity, taken together can adequately assign cells into the S-type or CX-type subgroups. 4. Various models of visual cortex are examined in view of the findings reported here and in the previous papers of this series, which suggest that a) orientation and direction selectivities are produced by separate neural mechanisms, b) there may be hierarchy among simple (S type) cells, and c) complex (CX-type) cells appear to receive a prominent S-type cell input.
Responses and receptive-field organization of cones in perch retinas
Authors: Burkhardt D. A.
Published: December 2017

1. Cones in the retinas of two closely related species of perch, the walleye and sauger (S, vitreum vitreum and S. canadense), are remarkably large. This paper reports a first series of intracellular recordings obtained from 77 of these cones. 2. A small spot of light evokes a sustained hyperpolarizing response from perch cones which may exceed 10 mV in amplitude, is graded with stimulus intensity, and is markedly reduced when the spot is decentered. Most cones seem to be orange sensitive with peak sensitivity at about 600 nm. 3. Enlarging the stimulus diameter from 0.04 to 0.25 mm produces a modest increase in the hyperpolarizing response. However, larger stimuli which illuminate surrounding regions of the retina often evoke a delayed depolarizing potential which antagonizes the sustained phase of the cone's hyperpolarizing response to central illumination. 4. The outer diameter of the region of the antagonistic surround is at least 2.2 mm in extent. An annulus evokes a depolarizing response only if the central region of the receptive field is simultaneously activated. 5. The present results provide the first direct evidence that the receptive fields of cones in fish retinas have an antagonistic center-surround organization. Luminosity-type horizontal cells probably serve as the interneurons which mediate the depolarizing influence of the surround.
Mouse spinal cord in cell culture. II. Synaptic activity and circuit behavior
Authors: Ransom B. R. , Christian C. N. , Bullock P. N. , Nelson P. G.
Published: December 2017

1. Neurons in cell cultures of fetal mouse spinal cord (SC) and dorsal root ganglia (DRG) develop extensive synaptic interconnections. 2. No spontaneous synaptic activity was detectable in the presence of tetrodotoxin or an elevated magnsium ion concentration, but statistical analysis of evoked excitatory postsynaptic potentials (EPSPs) indicates that the quantal size was 200-250 muV, which was below the noise level of the recording system used. 3. In a sample of eight RDG-SC and seven SC-SC cell pairs linked by EPSPs, the quantal content of the SC-SC EPSPs was about 3.5-fold larger than for the DRG-SC EPSPs. 4. The extrapolated equilibrium potential for the SC-SC EPSP was about 20 mV positive. The IPSP reversed at a membrane potential of 60-80 mV negative. 5. Some examples of the types of synaptic circuits commonly encountered are given. Only one case of electrical coupling between neurons was found.
Properties and tectal projections of monkey retinal ganglion cells
Authors: Schiller Peter H. , Malpeli Joseph G.
Published: December 2017

Page 432: Peter H. Schiller and Joseph G. Malpeli, “Properties and tectal projections of monkey retinal ganglion cells.” The legend to the figure at the bottom of page 432 should read: fig. 3. A: orthodromic potential of single cell in retina. B: antidromic response of same cell. Two components of the response evident which show considerable variation with antidromic activation. The second component is absent in the fifth trace. Time marker represents 1 ms.
Response of cutaneous hair and field mechanoreceptors in cat to paired mechanical stimuli
Authors: Tuckett R. P.
Published: December 2017

1. While studying hair- and field-receptor responses to paired mechanical pulses, I observed that in approximately half the receptors the recovery of excitability following generation of an impulse took the form of a damped oscillation. 2. Oscillations could be modified or eliminated by changing the conditions of stimulation: 1) there were no oscillations with an electrical conditioning stimulus; 2) oscillations occurred only when both mechanical pulses were delivered to the surface of the skin, not when the conditioning pulse was given to a hair shaft, and only when both pulses affected the same part of the receptive field; 3) oscillation was reduced by increasing the duration of the pulses; 4) oscillation was enhanced by increasing the distance between the stimulator and the nerve terminal; and 5) maxima on the recovery curve became minima and vice versa when the direction of the conditioning pulse was changed. 3. It was concluded that recovery curve oscillations were due not to the type of hair or field receptor being stimulated, but to the conditions of stimulation. The timing of the oscillations was a function of the duration of the mechanical pulse. Furthermore, interaction was additive when the interval between stimuli was an even multiple of the pulse width. This resulted in a minimal point on the recovery curve. At odd multiples of the pulse width, the converse resulted. The evidence suggests that waves, set up in the skin by the paired mechanical pulses, interact and cause the recovery curve oscillations. Such waves could be set up by a variety of stimuli that contact the skin naturally.
Cat hindlimb tactile dermatomes determined with single-unit recordings
Authors: Brown P. B. , Koerber H. R.
Published: December 2017

1. Single-unit recording from dorsal root ganglia was used to determine the dermatomes of L4-S2 segments in the cat. Dermatomes for low-threshold myelinated mechanoreceptor afferents are smaller than those reported in earlier studies of whole-root dermatomes. There are also sufficient discrepancies among earlier studies and with the present data to merit reexamination of hindlimb whole-root dermatomes. 2. Receptive-field size varies directly with distance from toes. Length/width ratio is essentially constant for different parts of the hindlimb. 3. Estimates of innervation density verify the long-standing assumption that innervation density is greater for foot and toes than for proximal hindlimb, at least for low-threshold cutaneous myelinated afferents.
Stimulus-response relations and stability of mechanoreceptor and motor neurons mediating defensive gill-withdrawal reflex in Aplysia
Authors: Byrne J. H. , Castellucci V. F. , Carew T. J. , Kandel E. R.
Published: December 2017

1. A weak or moderate-intensity tactile stimulus delivered to the siphon skin of Aplysia californica elicits a defensive reflex withdrawal of the gill and siphon into the mantle cavity. The reflex undergoes both short- and long-term habituation and sensitization and has, therefore, been used as a model system to examine various forms of learning. In this paper we describe studies of the response properties of the sensory and motor neurons of the reflex during repeated stimulation at rates that produce habituation. 2. The sensory neurons are slowly adapting mechanoreceptor cells whose frequency of discharge is a monotonic function of controlled-force punctate stimuli delivered to the skin. The majority of the stimulus-response relations could best be described by exponential functions. 3. We examined the stability of the sensory neuron responses in two ways; with punctate stimuli of varying intensity and with water jets of varying intensity. 4. With repeated punctate stimulation at rates which produce habituation in the intact animal the mechanoreceptor discharge showed no decrement. This stability was observed over a 10-fold range of intensities. 5. Weak or moderate intensity water-jet stimuli to the skin also gave stable responses but stronger stimuli caused the mechanoreceptor response to fatigue. 6. We examined the stability of the motor responses by using intracellular depolarizing current pulses to produce repetitive bursts of action potentials in gill motor neurons while monitoring the gill contractions with a strain gauge, photocell, or videotape recorder. The photocell and strain gauge were alternatively used in the same experiment. Gill contractions monitored with the photocell were stable, whereas those monitored by the strain gauge showed decrement. An independent measure of gill contraction, videotape recording, confirmed the results obtained with the photocell and showed that the gill contractions following repeated intracellular depolarization of the motor neurons were stable.
Functional and anatomical consequences of neonatal visual cortical damage in superior colliculus of the golden hamster
Authors: Rhoades R. W. , Chalupa L. M.
Published: December 2017

1. In normal hamsters the visual cortex sends a retinotopically organized projection to the ipsilateral superior colliculus. 2. Acute or chronic unilateral ablations of visual cortex in adult animals decrease the incidence of directionally selective cells encountered in the superficial laminae of the ipsilateral colliculus, but not in the deeper layers (those ventral to the stratum opticum). 3. Unilateral ablations of visual cortex in infant hamsters induce an aberrant crossed projection to the contralateral superior colliculus, confirming the finding of Mustari and Lund (58) in the rat. Horseradish peroxidase (HRP) experiments demonstrated that the cells whose axons comprise the normal as well as the anomalous projection are pyramidal neurons in layer V of cortex. 4. In adult hamsters that underwent early brain damage, about 13% of the cells in the colliculus could be activated by stimulation of the contralateral visual cortex. Only 1 unit (of the 159 cells tested) could be driven by similar stimulation in normal adult hamsters. This indicates that the anomalous crossed projection forms functional synapses in the contralateral tectum. 5. No cells (of the 113 tested) could be activated from the contralateral cortex in hamsters that sustained chronic ablations of visual cortex in adulthood; thus indicating that there is some limited time period during development when unilateral ablations of visual cortex induce an anomalous corticotectal pathway. 6. The visual response properties of superior collicular neurons in the neonatally brain-damaged animals were compared to those of normal hamsters, as well as to those with acute or chronic ablations of visual cortex sustained in adulthood. 7. There was no indication that the anomalous projection contributes to the organization of normal visual response properties in the superior colliculus of the neonatally brain-damaged animals. In fact, the incidence of directionally selective cells in these hamsters was found to be significantly lower than that of normals in both the superficial and deep laminae of the colliculus. 8. We conclude that while unilateral damage of visual cortex in the hamster induces an anomalous corticotectal projection that makes functional synapses, this aberrant input does not compensate for missing, normal corticotectal pathway in the organization of superior collicular response properties.
Lateral cervical nucleus in the cat: functional organization and characteristics
Authors: Craig A. D. , Tapper D. N.
Published: December 2017

1. The lateral cervical nucleus (LCN) was investigated with extracellular recordings in the anesthetized cat. A total of 556 LCN units were characterized; the locations of most of these were histologically verified. Half of these had receptive fields on the rostral third of the ipsilateral body surface including the face; 14% had fields on the thorax or abdomen, 33% had fields on the hindlimb or tail, and about 3% had receptive fields larger than one limb. 2. The LCN was observed to be somatotopically organized in experiments using angled microelectrode penetrations. Hindlimb units were dorsolateral, forelimb units ventromedial, and face units most medial within the LCN. In regions where LCN cells were present only in the medial portion of the dorsolateral funiculus, they were all forelimb units. 3. A special subpopulation (17%) of cells were clustered most ventromedially in the LCN. These units had large or disjoint receptive fields, and/or responded to deep, visceral, or noxious stimulation. A third of these did not project in the medial lemniscus (ML); many were synaptically activated by stimulation of the ML. Those that did project in the ML had significantly longer latencies than all other LCN units. It is suggested that this subpopulation contains local LCN interneurons. 4. The specific mechanoreceptor inputs were identified for each of 121 projecting LCN units. Receptor inputs were uniform across each receptive field; that is, each unit that responded to a given receptor type was observed to respond to receptors of that type throughout its receptive field. Input from large-fiber-diameter, velocity-sensitive mechanoreceptors was predominant. The absence of input from slowly adapting type I and II receptors and from joint receptors was confirmed. A significant number of units (17.3%) could be driven by only one receptor type. The LCN sample profile agrees closely with the receptor representation in the hindlimb portion of the spinocervical tract. It is concluded that these data that anatomic specification of convergence occurs in the LCN with respect to receptor connectivity, and that this specification originates in lamina IV of the dorsal horn. 5. Stimulation of the dorsal column nuclei synaptically excited 23% of the LCN units tested. In two cases it was possible to demonstrate, by collision, that this occurred via collaterals of spinocervical tract axons. It is concluded that some spinocervical axons have collaterals terminating in the rostral parts of the dorsal column nuclei.
Adaptation in catfish retina
Authors: Naka K. I. , Chan R. Y. , Yasui S.
Published: December 2017

1. We define absolute sensitivity as (voltage/illuminance) and incremental sensitivity as the peak-to-peak amplitude of the first-order (Wiener) kernels. 2. Incremental sensitivity of the horizontal cells is the local slopes of the Michaelis-Menten equation and that of more proximal neurons is the Fechner slope. In a log-log plot, the former has a slope of -2, whereas the latter a slope of -1, as predicted by Williams and Gale (39). 3. During a moderate to strong steady illumination, absolute sensitivity decreases but incremental sensitivity increases. The reverse occurs during dark adaptation. 4. The presence of a steady illumination did not prevent signal transmission from horizontal to ganglion cells. 5. From these results we conclude that: adaptation in the catfish retina includes two components: a) a lateral shift of the voltage-intensity curve along the intensity axis, and b) changes in the time course of light-evoked response. We argue that the latter phenomenon is related to the presumed horizontal cell-to-receptor cell negative feedback.
Biophysical mechanisms contributing to inking behavior in Aplysia
Authors: Byrne J. H. , Shapiro E. , Dieringer N. , Koester J.
Published: December 2017

1. The release of ink from the ink gland of Aplysia californica in response to noxious stimuli is mediated by three electrically coupled motor neurons, L14A, L14B, L14C, whose cell bodies are located in the abdominal ganglion. The initial synaptic input to the ink motor neurons is relatively ineffective in firing the cells. As a result, a pause of 1--3 s often occurs before the cells attain their maximum firing frequency and cause the release of ink. Using current and voltage-clamp techniques we have analyzed the mechanisms underlying the firing pattern of these cells. 2. The presence of a fast transient K+ current appears to play an important role in mediating the firing pattern of the ink motor neurons. Their high resting potential (-75 mV) ensures that the steady-state level of inactivation of the conductance channels for the fast K+ current will normally be low. Thus a train of EPSPs or a depolarizing current pulse can activate this current maximally, thereby reducing the initial effectiveness of the excitatory input. 3. In addition to the fast transient K+ current, four other currents were identified: 1) a fast transient tetrodotoxin-sensitive inward current, presumed to be carried by Na+; 2) a slower tetrodotoxin-insensitive inward current, presumed to be carried by Ca2+; 3) a slow transient outward tetraethylammonium- (TEA) sensitive current; and 4) a very slow TEA-insensitive outward current. 4. A decreased conductance EPSP, which turns on over a several-second period, contributes to a late acceleration of spike discharge in the L14 cells. 5. The results suggest that a unique combination of biophysical properties of the L14 cells and the features of the synaptic input cause them to act as a low-pass filter in the reflex pathway for inking.Their high resting potential, which ensures minimal inactivation of the fast transient K+ current channel, makes these cells preferentially responsive to strong and long-lasting stimuli. The delayed recruitment of a decreased conductance EPSP augments the tendency of the L14 cells to fire in an accelerating burst pattern.
Guidance of regrowing sensory axons after cutaneous nerve lesions in the cat
Authors: Horch K.
Published: December 2017

1. Individual type I sensory neurons in cutaneous nerves typically innervate two to four type I cutaneous mechanoreceptors (Haarscheiben). The extent to which these neurons replicate the original innervation patterns of the type I receptors after peripheral nerve regeneration and the means by which these neurons are guided back to their old receptor sites during regeneration were studied in cats using neurophysiological techniques. 2. By recording activity of type I neurons in small cutaneous nerves and isolated dorsal rootlets, it was possible to map the distribution of these neurons in the skin. Maps made before nerve lesion were compared to maps made after recovery from nerve crush and transection. 3. Fibers regenerating after nerve crush return to their old receptor sites, probably by following their old Schwann tubes in the distal stump of the nerve, and replicate the original receptor innervation pattern. Essentially all the type I fibers successfully regenerate in this case. 4. In contrast, after nerve transection the regenerating fibers do not restore the original innervation pattern, although they do preferentially return to other old type I receptor sites. About 60% of the type I fibers reinnervate the skin after transection. 5. These observations provide a basis for the difference in functional recovery seen after crush and transection lesions of peripheral nerves.
Loss of inhibitory synaptic input to cricket sensory interneurons as a consequence of partial deafferentation
Authors: Levine R. B. , Murphey R. K.
Published: December 2017

1. In a companion paper (5) we suggested that the enhanced ability of excitatory pathways to drive deafferented interneurons in crickets could be attributed to a reduction in the effectiveness of remaining inhibitory pathways impinging on these neurons. 2. In order to test this idea more directly, we examined a sensory interneuron in the cricket known as sensory interneuron 10-3 (SI 10-3). We first demonstrated that SI 10-3 was more sensitive to remaining excitatory inputs after partial deafferentation. 3. We then tested the ability of inhibitory inputs to suppress a train of current-evoked action potentials. Brief (100 ms) depolarizing current pulses were injected into the soma of SI 10-3 and the number of action potentials counted. Next, an identical depolarizing pulse was injected into the interneuron coincident with activation of the inhibitory pathway by a tone (75 dB at 450 Hz). Activation of the inhibition decreased the number of current-evoked action potentials. In order to quantify this effect, current-tone pairs were presented at four current intensities. Over the range of current intensities used, the relationship between current intensity and number of action potentials (AP/I curve), elicited with or without tones, was linear (Fig. 7A). 4. In control preparations, tones always lowered the calculated slope of the observed curve and its y intercept. In treated specimens inhibiting tones decreased the slope of the AP/I curve less than in control specimens. Based on this evidence, we concluded that the inhibitory pathway had been disrupted by partial deafferentation. This releases the giant neuron from inhibition, allowing it to respond more strongly to remaining excitatory inputs.
Analysis of ionic conductance mechanisms in motor cells mediating inking behavior in Aplysia californica
Authors: Byrne J. H.
Published: December 2017

1. The release of ink in response to a noxious stimulus is a relatively stereotyped behavior produced by strong and long-lasting stimuli. The purpose of this series of papers is to determine the quantitative extent to which the known voltage- and time-dependent ionic conductance mechanisms and synaptic influences can account for the ink gland motor neurons' firing pattern and, thus, the features of the behavior. 2. Four voltage- and time-dependent ionic currents have been analyzed. These include a fast transiet Na+-mediated inward current, a slower Ca2+-mediated inward current, a fast transient K+-mediated outward current, and a slower delayed outward current also mediated by K+ ions. 3. The current-voltage (I-V) relationships, equilibrium potentials, and steady-state activation and inactivation characteristics appear qualitatively similar to comparable currents observed in other gastropod neurons. 4. The recovery from inactivation of the delayed outward current has two time constants, one comparable to the inactivation time constant and the other more than an order of magnitude larger. The fast transient K+ current also appears to have a similar slow recovery from inactivation. 5. The synaptic current contributing to the firing pattern of the ink motor cells is a complex function of time. Initially, the synaptic conductance is high and the equilibrium potential near 0 mV. But, with time there is a gradual decrease in synaptic conductance and shift in the equilibrium potential to more depolarized levels.
Simple-spike activity of cerebellar Purkinje cells related to visually guided wrist tracking movement in the monkey
Authors: Mano N. , Yamamoto K.
Published: December 2017

1. Three rhesus monkeys were trained to perform a rapid (greater than 100 degrees/s) and a slow (less than 100 degrees/s) wrist movement guided by a visual cue. While the monkey performed wrist flexion or extension from a neutral position, Purkinje cell (P-cell) discharges were recorded from intermediate and lateral parts of lobules IV--VI of the cerebellum. 2. By the visually guided movement, we could control the direction of the wrist movement; the holding position at three different angles of the wrist joint: neutral, about 30 degrees flexed, and extended; and the velocity in four ranges: a) 10--30, b) 30--100, c) 100--300, and d) 300-650 degrees/s. 3. From 92 P-cells that significantly increased or decreased the discharge rate of simple spikes with task performance, we selected 45 P-cells ("response-locked" cells) as related to the wrist movement by statistical analyses of temporal correlation of P-cell activities to wrist movement. The direction of the frequency modulation (increase or decrease) was in a nonreciprocal fashion with oppositely directed wrist movements (flexion or extension) in 90% of the response-locked P-cells. The maintained frequencies at three holding positions did not significantly differ. 4. Nineteen P-cells changed their spike frequencies temporally locked to both rapid and slow wrist movements. By the discharge pattern in relation to the rapid and slow movements, these cells were classified into two groups. Discharge pattern in group I P-cells (n = 5) conformed very well to that of velocity, and a linear correlation between the instantaneous increase of the discharge rate and velocity was observed in analyses of individual trials. Group II cells showed increase (n = 9) or decrease (n = 5) of firing rate (20--50 spikes/s) larger than group I cells (less than 10 spikes/s) as long as the wrist was moving, even with very slow velocity (less than 30 degrees/s. The correlations between the increase of the discharge rate and the velocity in individual trials were less clear in group II than in group I cells. 5. The present study suggests the importance of the cerebellar cortex in controlling the slow limb movement as well as the rapid movement. The selected P-cells in this study also suggested that the velocity or some dynamic aspect related to the velocity of limb movement is the major information among the dissociated motion parameters coded by the simple-spike frequencies of the P-cells in the cerebellar hemisphere. Whether the latter suggestion represents an essential characteristic of all limb movement-related P-cells or reflects only a feature of a special subgroup among the movement-related cells should be clarified in future experiments.
Ionic basis of presynaptic inhibitory potentials at crayfish claw opener
Authors: Fuchs P. A. , Getting P. A.
Published: December 2017

1. Intracellular recordings from the claw opener excitor axon of the crayfish, Procambarus clarkii, were obtained near the terminal arborizations of the axon on the surface of the opener muscle. Rest potential in the excitor axon averaged --80 mV over 20 cells. Action-potential amplitude and duration averaged 100 mV and 2 ms, respectively. 2. A single action potential in the opener inhibitor axon produces a hyperpolarizing synaptic potential (average amplitude 0.3 mV) in the excitor axon. The apparent reversal potential of this inhibitory synaptic potential is approximately 5 mV more negative than rest in control saline. No excitor axons were observed to have depolarizing synaptic potentials at rest. 3. A decrease in external chloride concentration from 240 to 24 mM causes the apparent reversal potential to depolarize an average of 12 mV, with no change in rest potential. In low-chloride saline, the synaptic potential evoked by stimulation of the inhibitor axon becomes depolarizing. 4. An increase in external potassium concentration from 5 to 10 mM causes the apparent reversal potential to depolarize by 16 mV; however, rest potential depolarizes by 10 mV. Low external potassium has the opposite effects, causing both rest potential and the apparent reversal potential to hyperpolarize. 5. Presynaptic inhibition at the Procambarus claw opener neuromuscular junction appears to be mediated by a hyperpolarizing synaptic potential. The results of these experiments suggest that chloride serves as the charge for the presynaptic potential. The evidence for a direct involvement of potassium as a charge carrier is equivocal due to Donnan equilibrium effects involving Cl.
On- versus off-responses of raccoon glabrous skin rapidly adapting cutaneous mechanoreceptors
Authors: Pubols B. H.
Published: December 2017

1. The on- and off-responses of 50 raccoon median nerve fibers associated with rapidly adapting cutaneous mechanoreceptors in glabrous skin were examined under experimental conditions designed to allow comparable opportunities for on- and off-responses to occur. Trapezoidal stimuli were utilized, providing for equal stimulus indentation and retraction velocities and equal static displacement times and intertrial intervals. Principal findings were as follows: 2. At stimulus levels well above displacement and velocity thresholds for on-responses, 80% of units yielded a more vigorous on-response than off-response (as measured by the total number of ramp impulses); in 6%, the reverse was true; while in the remaining 14%, the off-discharge was absent. 3. On and off displacement thresholds were approximately equal (on median, 43 micron; off median, 42 micron). However, on velocity thresholds were significantly lower than off velocity thresholds (on median, 1.0 micron/ms; off median, 3.8 micron/ms). 4. Exponents (b) of power functions relating discharge rate to ramp velocity (frequency = a x velocityb) were consistently greater for on-responses than for off-responses, but intercept constants (a) were consistently greater for off-responses than for on-responses. 5. Previous findings that mammalian rapidly adapting (RA) mechanoreceptors possess a “linear directionality” generally favoring on-responses were confirmed. 6. Results are discussed in relation to the role of viscoelastic properties of RA mechanoreceptors and neighboring skin. It is suggested that, when considerations is also given to the mechanical properties of surrounding tissues, the Loewenstein and Skalak (18) analysis of the mode of operation of Pacinian corpuscles might also apply, at least qualitatively, to the simple dermal (rapidly adapting) corpuscle of raccoon glabrous skin.
Physiological and histochemical characteristics of motor units in cat tibialis anterior and extensor digitorum longus muscles
Authors: Dum R. P. , Kennedy T. T.
Published: December 2017

1. Intracellular recording and stimulation techniques were used to study the normal motor-unit population of tibialis anterior (TA) and extensor digitorum longus (EDL) muscles in the cat. Histochemical staining of the whole muscle and glycogen depletion of single motor units were performed. These results may be compared to those of their extensor antagonist, medial gastrocnemius (MG), as reported in studies by Burke and co-workers (7, 11, 13). 2. On the basis of two physiological properties, “sag” and fatigue resistance, the motor units in both TA and EDL could be classified into the same categories (types FF, F(int), FR, and S) as in MG (11). In contrast to MG, TA and EDL had nearly twice as many type-FR motor units and only half as many type-S motor units. 3. Glycogen depletion of representative single motor units of types FF and FR suggests a close correspondence between the physiological classification and a unique histochemical profile. No type-S units were depleted. 4. On the basis of histochemical staining, the muscle fibers in TA were presumed to belong to type-FF, -FR, or -S motor units. TA had a higher proportion of type-FR and a lower proportion of type-S muscle fibers than are found in MG. A striking feature was the variation in the proportion of each fiber type in different regions of TA. The anterolateral portion had mostly types FF and FR, while the posteriomedial portion had more types FR and S. 5. The twitch time to peak (TwTP) of isometric motor-unit contractions was generally quite fast with none having TwTP greater than 55 ms. The mean TwTP (not in EDL) and the mean tetanic tension of each motor-unit type were significantly different from each other. Most of the motor units exhibited significant postetanic potentiation of twitch tension and a corresponding lengthening of half-relaxation time and to a lesser degree, twitch contraction time. 6. There was a significant relationship between the inverse of motoneuronal input resistance and either tetanic tension or twitch contraction time. These relationships were not apparent when axonal conduction velocity rather than input resistance was used as an index of motoneuron size. The mean input resistances of the three major motor-unit types were significantly different while the mean conduction velocities of types FF and FR were nearly identical. A weak positive correlation was observed between the TwTP and the afterhyperpolarization of TA and EDL motoneurons. 7. In general, the mechanical characteristics and intrinsic motoneuronal properties of TA and EDL appear to parallel the organization of their extensor antagonist, MG, with some important quantitative differences that may reflect their different functional roles.
Sensory discrimination: decision process
Authors: Johnson K. O.
Published: December 2017

1. This paper and a following paper deal with problems, such as the following, that arise in experimental studies of the neural mechanisms underlying sensory discrimination: What measures of neural activity are relevant in such a study? How can sample data from the responses of single neurons be combined to represent the information relayed by a population of neurons? How can neural data be compared with results from psychophysical studies? What assumptions are implicit in any such comparison? What are the implications of assumptions that neurons respond independently or that they have homogeneous response properties? How can neural codes be assessed in a systematic way? Can psychophysical and neurophysiological observations be combined to infer mechanisms or relationships in the processes underlying discrimination? All of these questions require some theoretical framework before they can be answered. These papers set out such a framework, they deal with most of those questions, and they provide practicable formulas for relating sample data from neurophysiological experiments to behavioral measures derived from psychophysical experiments. 2. The processes that intervene between a relatively peripheral array of neural activity and a subject's decision in a discrimination task are split into two sections: a) the ascending sensory processes that provide the final patterns of neural activity on which discrimination is based, and b) a process that yields decisions of the type required by the experimental design used in the psychophysical study. The approach is to develop a theory of the decision process in this paper, and then to expand it to incorporate the ascending processes in the following paper. 3. The decision theory deals with a class of experimental designs in which a subject is required to make a decision about two stimuli S1 and S2 (e.g., S1 is larger than S2, S2 is the same as S1, S2 was the modified stimulus, and so on). A mathematical representation for experimental designs of this type is developed. 4. The decision process is analyzed in two forms: a) a multivariate form in which the discrimination decision results directly from multidimensional neural representation of the two stimuli, and b) a vivariate form in which the final representation of each stimulus is a unidimensional variable. Conditions required for equivalence of these formulations are examined. 5. The theory includes as explicit variables a) the experimental design, b) the subject's discrimination strategy, c) bias, d) memory variance, e) bias variance, f) variance in the final neural representations of the stimuli, and g) their functional dependence on the stimuli that they represent. 6. Formulas are developed for the expected values of commonly used psychophysical measures such as the classical psychometric function, receiver operating characteristic (ROC) functions, discriminatory separation index (d'), and the difference limen. 7. Optimum discrimination behavior is analyzed.
Corrigenda for Glycogen-depletion method of intrafusal distribution of γ-axons that increase sensitivity of spindle secondary endings
Authors: Jami Léna , Lan-Couton Dominique , Petit Julien
Published: December 2017

Page 16: Léna Jami, Dominique Lan-Couton, and Julien Petit. The title of the article should read: “A study with the glycogen-depletion method of intrafusal distribution of ggr-axons that increase sensitivity of spindle secondary endings.”
Amplitude of responses to perturbation in primate sensorimotor cortex as a function of task
Authors: Wolpaw J. R.
Published: December 2017

1. Monkeys learned to maintain hand position against a range of background forces. Short-latency responses to passive wrist extension or flexion were recorded from units in areas 4, 3, 1, and 2. Response amplitude was studied as a function of background force direction (extension or flexion). 2. For 40% of the precentral and postcentral responses, response amplitude depended on constant force direction. For these dependent responses, amplitude with background force in one direction averaged 2.8 times amplitude with background force in the opposite direction. 3. Units for which background activity varied with constant force direction were designated task related. Dependent responses from area 4 task-related units were usually larger when background activity was greater and when background force direction matched the direction of the passive movement. 4. Dependent responses from area 4 task-related units occurred significantly later than nondependent responses from the same units. 5. Since most area 4 task-related activity was explicable as a result of peripheral input via the same oligosynaptic path mediating area 4 responses to passive movements (32), the present findings imply that area 4-task-related activity may result in large part from centrally mediated change in the access of short-latency peripheral input to area 4 units. 6. The dependence of responses from non-task-related area 4 units and from non-task-related and task-related postcentral units showed no dominant correlation with background activity or with background force direction. Their dependence appeared to require no explanation other than a change in peripheral input with change in background force direction.
Segmental giant: evidence for a driver neuron interposed between command and motor neurons in the crayfish escape system
Authors: Roberts A. , Krasne F. B. , Hagiwara G. , Wine J. J. , Kramer A. P.
Published: December 2017

1. The giant command neurons for tailflip escape behavior in crayfish have been thought to excite the nongiant fast flexor (tailflip producing) motor neurons (FFs) via monosynaptic connections. We show here that excitation of FFs instead occurs via a bilateral pair of segmental giant neurons (SGs) interposed between the command axons and FFs in each segment. 2. Anatomically, the SGs appear to make numerous contacts with ipsilateral command axons and FFs and fewer contacts contralaterally. In contrast, the command axons have only sparse direct connections to the FFs. An SG has an axon in the ipsilateral first ganglionic root and may be a modified swimmeret motor neuron. 3. Each SG is depolarized well beyond threshold by the firing of an ipsilateral command axon and is depolarized to near threshold by the firing of a contralateral command axon. The synapses between command axons and SGs are electrical and probably rectifying. 4. Each FF is excited to a level near firing threshold by the SG ipsilateral to its axon and is excited weakly by the contralateral SG. The synapses between SGs and FFs are electrical and nonrectifying. 5. Variations in excitatory postsynaptic potentials (EPSPs) recorded in FFs during prolonged, high-frequency firing of the command axons can be accounted for by refractoriness of SG spikes, as opposed to refractoriness of dendritic branch spikes as had previously been delivered. 6. These findings illustrate the limitations of conventional tests for monosynapticity. 7. The functional significance of having driver neurons interposed between command neurons and motor neurons is discussed.
Branching pattern and properties of vertical- and horizontal-related excitatory vestibuloocular neurons in the cat
Authors: Uchino Y. , Hirai N. , Suzuki S.
Published: December 2017

1. The axonal trajectories of excitatory vestibuloocular neurons and their synaptic contacts with extraocular motoneurons were studied by means of spike-triggered signal averaging and microstimulation techniques. A majority of the excitatory neurons related to the vertical semicircular canals were located in the border of the descending and medial nuclei and the rostral half of the descending nucleus. 2. Individual vestibuloocular neurons activated by stimulation of the ampullary nerve of the anterior semicircular canal excited motoneurons within both the contralateral inferior oblique and contralateral superior rectus motoneuron pools. 3. Individual vestibuloocular neurons receiving input from the ampullary nerve of the posterior semicircular canal excited motoneurons in both the contralateral trochlear nucleus and contralateral inferior rectus motoneuron pools. The branching pattern of single vestibuloocular neurons activated by the anterior and posterior canals probably underlies conjugate eye movement during vertical head rotation. 4. Time to peak and shape indices of unitary excitatory postsynaptic potentials (EPSPs) suggested that the location of the synaptic contact of vestibuloocular neurons was on the soma or proximal dendrites of the target extraocular motoneurons. 5. In contrast, we did not find conclusive evidence that single vestibuloocular neurons receiving input from the horizontal semicircular canal give off axon collaterals to motoneurons innervating both the contralateral lateral rectus and the ipsilateral medial rectus muscles. Projection of horizontal vestibuloocular neurons to motoneurons supplying individual muscles might be useful for convergence during horizontal head movement.
Avian vestibuloocular reflex: adaptive plasticity and developmental changes
Authors: Wallman J. , Velez J. , Weinstein B. , Green A. E.
Published: December 2017

1. This study demonstrates plasticity of the vestibuloocular reflex (VOR) in chickens and compares it to that of other species and to that of newly hatched chicks. Adaptive changes in the VOR were induced by subjecting the animals to combinations of visual and vestibular stimuli that simulated the effect of the VOR being either too low in gain or reversed in phase. 2. The VOR of chickens resembles that of mammals, but the curve of phase lead versus frequency seems shifted toward higher frequencies. The VOR of newly hatched chicks has extremely low gain (less than 0.1). 3. In both the older and newly hatched animals, the VOR gain increased substantially after 2 h in an environment in which the imposed en bloc rotations produced increased retinal image slip in the normal directions. Similarly, 2 h of reversed retinal image slip produced decreased VOR gain and, in some cases, reversal fo the phase of the VOR. The gain changes were largest at the "training" frequency. The phase changes were in the direction of increased phase lead. Changes in the gains of the optokinetic responses and of the combination of VOR and optokinetic responses were also seen, especially in the newly hatched animals. 4. The newly hatched birds showed the largest VOR changes in the increased-gain situation, whereas the older birds showed the largest changes in the reversed-phase situation, as assessed by the changes in the average retinal slip velocity experienced. These results may well not be a consequence of differences in age, per se, but of differences in average retinal slip experienced in the two experimental situations at the start of the trial because of the lower VOR gain of the newly hatched animals. There seems to be no dramatic difference in VOR plasticity between newly hatched and older birds. 5. Our results with reversed visual motion are substantially different from those obtained in similar studies on rabbits, suggesting that these two species use different error signals to control the adaptive adjustment of the VOR.
Retinal processing of intrinsic ad extrinsic noise
Authors: Levine M. W.
Published: December 2017

1. Recordings were made from single ganglion cells in the isolated retinas of goldfish. Statistics of the maintained discharge were computed for steady-state firing in the dark, in the presence of a steady-adapting light confined essentially to the center of the receptive field, and in the presence of the same adapting light modulated by Gaussian white noise. 2. Steady adapting lights effected a significant initial change in firing rate and affected sensitivities to test probes. After a new minutes, however, the rate returned to a moderate level. There was no consistent relationship between firing in the dark and illuminated conditions, nor was there a consistent relationship between the values of the coefficient of variation of firing in the dark and in light, although some individual cells showed changes in these properties when illuminated. 3. There was no consistent change in the organization of the firing in dark and in steady light. Neither the normalized autocovariances nor the serial correlograms, indicators of short-term order, were significantly affected by light. Similarly, plots of the standard deviation of rate versus sample duration, an indicator of long-term structure, were not altered by illumination. The intrinsic noise thus appears unaffected by retinal illumination. 4. Gaussian modulation of an adapting light (extrinsic noise) increased the coefficient of variation; it also dramatically increased mean firing rate. This effect was observed in both red-on and red-off cells; it indicates a nonlinearity that is present even in the spatially linear X-like neurons. 5. Gaussian modulation of an adapting light made the short-duration values of the normalized autocovariances slightly more positive. Similarly, modulation made the first two or three coefficients of the serial correlogram more positive; this indicates low pass filtering of the extrinsic noise. 6. Gaussian modulation of an adapting light had no effect on the plots of standard deviation of rate versus sample duration other than simple translation due to increased variability. Since the form of these plots in the absence of modulation implies high-pass filtering of the intrinsic noise, the extrinsic noise must also be processed by the same (or a similar) high-pass filter. 7. A model is proposed in which extrinsic signals are band pass filtered by a low-pass and a high-pass filter in cascade. The intrinsic variability evident in the maintained discharge is apparently injected between the two filters. Alternative possibilities are discussed.