Psychophysics: Is subliminal learning really passive?
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[Analgesic effect of high-frequency and acupuncture-like transcutaneous electric stimulation of nerve fibers in spinal osteochondrosis].
Epicutaneous electrostimulation of nerve fibers was used in 192 patients with the neurologic manifestations of spinal osteochondritis in order to alleviate the pain syndrome. Two stimulation regimens were used: a high-frequency one (rectangular impulses of current with an 0.1-0.2 msec duration and a 70 Hz frequency and the intensity being subliminal for a motor response) and "acupuncture-like" a series consisting of seven impulses of the same duration and frequency with the repetition of three series in one second, the intensity of the irritant being over the motor response threshold). The occurrence of prolonged analgesia was shown to be approximately equal with both regimens and to depend significantly on the duration of the pain syndrome and the presence of the symptoms of the loss of spinal root function. There were several cases when after one of the regimens had failed, the pain was controlled by the alternative method of stimulation.
Adult↗
LEAKAGE OF TRANSMITTERS IN SALIVARY GLANDS.
Salivary secretion evoked by sympathetic stimulation or by injection of guanethidine, adrenaline or synephrine is slightly reduced by parasympathetic antagonists in doses which abolish the secretory responses to stimulation of the parasympathetic nerve. Similarly, an adrenaline antagonist caused a small diminution of the salivary flow elicited by parasympathetic stimulation or by injection of methacholine chloride. Secretion caused by pilocarpine could be accelerated by physostigmine. We conclude that transmitter leaks in subliminal concentrations, as far as secretion is concerned, from the sympathetic and parasympathetic postganglionic nerve endings.
Acetylcholine↗
[Study of the mechanism of an atrial pause using endocavitary recording of the sinus node potential in man].
The aim of this clinical study was to determine the electrophysiological mechanism of spontaneous atrial standstill, defined as a sudden lengthening of the trial cycle to over 10 p. 100 of its basal value, by recording the sinus node potential by endocavitary electrocardiological techniques. Satisfactory recordings of the sinus potential were obtained for the study of 65 atrial pauses recorded in 31 patients (18 without sinus node dysfunction and 13 with sinus node disease). It was shown that atrial pauses, shorter than two basal atrial cycles correspond to a moderate slowing of the sinus rhythm and to a sometimes very significant lengthening of the sinoatrial conduction time when sinus rhythm resumed. Pauses longer than two basal atrial cycles were always due to sinoatrial block which sometimes occured in patients with clearly individualised sinus activity, and sometimes with a slow continuous sinus activity. The sinus period did not change during these long pauses and sinoatrial conduction was normal when sinus rhythm resumed. The increased duration of the sinus potential, a constant finding during these pauses, is related to an intrasinusal conduction defect. This suggest that the primum movens of sinoatrial block is intrasinusal block which prevents rapid recruitment of a sufficient number of elemental sinus potentials so that the resultant potential becomes subliminal and therefore incapable of passing the sinoatrial junction. Short-lasting atrial pauses with a normal response to extrastimulus or atrial stimulation and characterised electrophysiologically by an increased sinoatrial conduction time without block of the sinus potential may be opposed to long atrial pauses with the pathological response of sinus node dysfunction characterised electrophysiologically by block of the sinus impulse. In practice the ability to induce a long pause by atrial stimulation (sinoatrial block) revealing latent disease of intrasinusal or sinoatrial conduction, may constitute an essential physiological sign of sinus node dysfunction.
Electrocardiography↗
Role of ions in generation of taste nerve responses to electrical tongue stimulation in rats.
The role of ions in the generation of taste nerve responses to electric currents was studied by examining integrated responses and single fiber discharges of the chorda tympani nerve to chemical and electrical stimulations of the tongue in rats. Integrated chorda tympani responses to anodal currents were suppressed after cessation of the blood flow to the tongue and on application of FeCl3 to the tongue surface. These findings indicate that electric currents do not stimulate the nerve directly but activate taste cells to evoke neural discharges. Magnitude of the integrated response to anodal current decreased with a decrease in concentration and with an increase in flow rate of the bathing solution applied over the tongue during electrical stimulation. All the chorda tympani fibers responsive to a certain electrolyte responded to anodal or cathodal current in the presence of the same electrolyte at its subliminal concentration in the flow chamber. However, there were a few fibers which did not respond to a few electrolytes, but responded to currents in the presence of either one of the electrolytes even at their much lower concentrations. Across-fiber correlations between the responses to chemical stimuli and anodal currents in the presence of the chemical solutions in the flow chamber indicated that responsiveness to anodal current was not always dependent on species of cation in the bathing solution. From these findings, we assume that the response to electric current is due to the effect of electrophoretically carried ions on not only specific but also non-specific receptor mechanisms for the ions.
Action Potentials↗
Immediate and long-term plasticity in human somatosensory thalamus and its involvement in phantom limbs.
This paper describes studies on plasticity that the author undertook with Patrick Wall in the mid '70s, and then reviews recent related studies in humans carried out in the author's laboratory. The human studies have shown that thalamic neurons frequently have subliminal receptive fields (RFs) and immediately following a reversible block of afferent activity from the RF some neurons develop increased sensitivity to tactile stimulation at sites outside their normal RF. Also described and discussed are novel findings in patients that had a limb amputated. The results suggested an expansion of the representation of the proximal limb into the thalamic region that used to represent the amputated part. Furthermore, in those patients that had a phantom limb, microstimulation in this region induced sensations perceived as originating on the phantom.
Anesthetics, Local↗
Crossing inputs of the superior laryngeal nerve afferents to medullary swallowing-related neurons in the cat.
To understand the neural mechanism for generation of synchronous activity on both sides during swallowing, we examined the convergence of inputs from the bilateral superior laryngeal nerves (SLNs) in the urethane-anesthetized cat medulla and we also examined the changes in swallowing outputs after a longitudinal brain-stem split in decerebrate cats. Twenty-six (31%) of 84 swallowing-related neurons (SRNs) that were oligosynaptically activated by ipsilateral SLN stimulation and recorded mostly in the reticular formation received contralateral inputs, which were confirmed by orthodromic spike responses (n = 16) or were detected as subliminal facilitatory or inhibitory inputs (n = 10) using conditioning-test stimuli. The rate of convergence of inputs from bilateral SLNs in these SRNs was significantly higher than that (4%) in the SRNs that were regarded as sensory-relay neurons in the nucleus tractus solitarius (NTS). The SRNs receiving signals from the contralateral SLN were located diffusely from the NTS and the adjacent reticular formation to the nucleus ambiguus (NA) and the reticular formation dorso-medial to the NA. A midsagittal split from 3 mm caudal to 6 mm rostral to the obex could change symmetrical swallowing to unilateral swallowing. Thus the crossing projections to the contralateral SRNs appear to contribute to symmetrical swallowing.
Afferent Pathways↗
Biologic significance of constitutive and subliminal growth factor production by bone marrow stroma.
The "stromal" or adherent cells of long-term murine Dexter explant bone marrow cultures provide the best in vitro model of the bone marrow microenvironment. Colony-stimulating factor-1 (CSF-1) is produced constitutively by these cells and is easily detected, but most investigators have not found constitutive production of the other hemolymphopoietic cytokines. We have previously reported the detection of granulocyte-macrophage-CSF (GM-CSF) in murine stromal cultures and its induction by the lectin Pokeweed mitogen. The present studies analyzing stromal cytokine messenger RNA (mRNA) production by standard Northern blot analysis show constitutive production of mRNAs for CSF-1, GM-CSF, granulocyte-CSF (G-CSF), c-kit ligand (KL), and interleukin-6 (IL-6), but not IL-3, IL-4, or IL-5 by 3-week irradiated or nonirradiated murine Dexter stromal cells. Exposure of stromal cells to Pokeweed mitogen or IL-1 16 hours before RNA harvest induces the messages for GM-CSF, G-CSF, KL, and IL-6, but not IL-3, IL-4, IL-5, or CSF-1. Polymerase chain reaction amplification of cDNA made with reverse transcriptase from stromal RNA using two separate sets of IL-3-specific primers shows the presence of IL-3 message in irradiated stromal cells, which is only detectable with this more sensitive technique. The factor-dependent cell lines FDC-P1 and 32D are supported by the stromal cells without the addition of exogenous growth factors, demonstrating a cytokine activity in these cultures that is inhibited by the addition of anti-IL-3 or anti-GM-CSF antibodies. These data indicate that murine Dexter stromal cells constitutively produce CSF-1, GM-CSF, G-CSF, IL-6, KL, and IL-3. This growth factor production could explain the support of granulocyte, macrophage, and megakaryocyte production and stem cell maintenance in Dexter-type long-term murine bone marrow cultures.
Animals↗
Abnormal central integration of a dual somatosensory input in dystonia. Evidence for sensory overflow.
Several observations suggest impaired central sensory integration in dystonia. We studied median and ulnar nerve somatosensory evoked potentials (SEPs) in 10 patients who had dystonia involving at least one upper limb (six had generalized, two had segmental and two had focal dystonia) and in 10 normal subjects. We compared the amplitude of spinal N13, brainstem P14, parietal N20 and P27 and frontal N30 SEPs obtained by stimulating the median and ulnar nerves simultaneously (MU), the amplitude value being obtained from the arithmetic sum of the SEPs elicited by stimulating the same nerves separately (M + U). Throughout the somatosensory system, the MU : (M + U) ratio indicates the interaction between afferent inputs from the two peripheral nerves. No significant difference was found between SEP amplitudes and latencies for individually stimulated median and ulnar nerves in dystonic patients and normal subjects, but recordings in patients yielded a significantly higher percentage ratio [MU : (M + U)x100] for spinal N13 brainstem P14 and cortical N20, P27 and N30 components. The SEP ratio of central components obtained in response to stimulation of the digital nerves of the third and fifth fingers was also higher in patients than in controls but the difference did not reach a significant level. The possible contribution of subliminal activation was ruled out by recording the ratio of SEPs in six normal subjects during voluntary contraction. This voluntary contraction did not change the ratio of SEP suppression. These findings suggest that the inhibitory integration of afferent inputs, mainly proprioceptive inputs, coming from adjacent body parts is abnormal in dystonia. This inefficient integration, which is probably due to altered surrounding inhibition, could give rise to an abnormal motor output and might therefore contribute to the motor impairment present in dystonia.
Adult↗
Effect of subliminally perceived stimulus differences or of superliminally perceived order differences.
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Discrimination, Psychological↗
Stem cell factor induction of in vitro murine hematopoietic colony formation by "subliminal" cytokine combinations: the role of "anchor factors".
The high levels of hematopoietic growth factors required for in vitro and in vivo activity raise questions as to their role in normal hematopoietic maintenance. We hypothesize that the use of combinations of cytokines to stimulate hematopoietic progenitors might allow individual factors to exert their influence at lower, more physiologically relevant concentrations. Growth factor combinations were assessed by their ability to stimulate both total colonies and high proliferative potential colony-forming cells (HPP-CFC), an early murine hematopoietic progenitor, in double-layer agar cultures. Very-low-level combinations of colony-stimulating factor (CSF)-1, granulocyte CSF (G-CSF), granulocyte-macrophage CSF (GM-CSF), interleukin (IL)-1 alpha, and IL-3 had little or no clonogenic capacity. Plateau levels of rr stem cell factor (rrSCF), a c-kit ligand, used alone also had negligible clonogenic capacity, but when combined with the low-level combination of the other five factors produced total colony and HPP-CFC growth approaching that produced by all factors at plateau levels. Delayed addition experiments suggest that this effect may represent sequential activity of SCF and the other factors. We propose a model of the normal hematopoietic microenvironment in which SCF at locally high concentration on the stromal cell surface "anchors" the hematopoietic stem cell's response to multiple other cytokines at physiologically relevant levels.
Animals↗
Cross-correlation analysis of geniculostriate neuronal relationships in cats.
The organization of geniculate inputs to a cat's visual cortical cell was studied by a cross-correlation technique. Simultaneous extracellular recordings were made in the lateral geniculate nucleus and in the striate cortex, and neuronal connectivity between a geniculate cell and a striate cell was examined by cross-correlograms of their impulse discharges under photic stimuli. Of 243 pairs of geniculate and striate cells with overlapping receptive fields, 82 showed positive correlations with short (0.9-2.7 ms) delay times. The delays in 65 of the 82 pairs were short enough to infer that the geniculate cell exerted monosynaptic excitatory action on the striate cell. Monosynaptic excitations were found in all types of striate cells. Those in cells with exclusively an on area or an off area (E-on/off cells) or in simple cells originated mostly from X geniculate cells; those in special-complex cells originated exclusively from Y geniculate cells; and those in standard-complex cells arose from both X and Y geniculate cells. The convergence number from geniculate cells to an E-on/off or simple striate cell was estimated as more than 10, since about 1/10 of the discharges from an E-on/off or simple cell in response to a moving stimulus was correlated with discharges from a geniculate cell. A larger convergence number (more than 30) was obtained for complex cells. Convergence from 2 to 5 geniculate cells was actually demonstrated in 17 of the 32 striate cells, each of which was tested in pair with 3-14 geniculate cells. The converging inputs thus observed included both X and Y geniculate cells in one E-on, one simple, and three standard-complex cells. They included both on-center and off-center geniculate cells in one simple, one special-complex, and five standard-complex cells. Under stimulation with a stationary light slit, the center fields but not the surround fields of geniculate cells were found to contribute to the receptive fields of the simple striate cells. However, the surround fields of geniculate cells contributed to the subliminal response areas flanking the central areas of E-on/off cells. The center fields of the geniculate cells also contributed to the central areas of the E-on/off cells. These observations suggest different models for simple cells and E-on/off cells as regards the organization of their geniculate inputs; simple cells may receive inputs from both on-center and off-center geniculate cells, but E-on/off cells receive inputs only from one or the other of them.
Animals↗
Enhancing GABAergic transmission reverses the aversive state in rats induced by electrical stimulation of the periaqueductal grey region.
In a proposed rat model for anxiety (electrical stimulation of the periaqueductal grey region), progabide (a GABA agonist) and diazepam both increased the latency to escape to a safe compartment and also the current needed to induce the escape response (escape threshold). Furthermore, the effects of progabide and diazepam were greater than additive in their actions on the escape response as when given together in normally subliminal doses, the combination exerted a marked anti-aversive effect. These actions of the drugs alone or in combination could not be explained by non-specific motor effects. Blockade of GABA receptors by bicuculline greatly reduced or abolished the action of progabide and diazepam (single administration). Sodium valproate, which indirectly augments GABAergic transmission, also increased the escape latency and escape threshold whereas, in contrast, diphenylhydantoin accentuated the aversive effects of stimulation of the periaqueductal grey. Haloperidol increased the escape latency and threshold but not other signs of distress following central stimulation (vocalization, jumping) which were effectively blocked by progabide and diazepam. The action of haloperidol was completely explicable by an interference with motor mechanisms. These results are interpreted as an indication that GABA agonists have an anti-aversive action in this proposed rat model for anxiety and, furthermore, that GABA receptors at least partially mediate the actions of benzodiazepines in this model.
Animals↗
Cyclic time course of motor excitability modulation during the observation of a cyclic hand movement.
The observation of a sinusoidal flexion-extension of the wrist was utilized to determine the continuous time course and phase relation between observed movement and its effects on the observer's motor pathways. While observing movements performed by others, the observers' cortical motor areas and spinal circuits were activated, reflecting the specific temporal and muscular pattern of the actual movement (motor resonance). H-reflexes and motor-evoked potentials (MEPs) were elicited, respectively, by electrical stimulation of the median nerve and magnetic stimulation of the appropriate cortical area, in the right forearm muscle Flexor Carpi Radialis (FCR) of subjects who were observing a 1-Hz cyclic oscillation of the right prone hand executed by a different person. Observation elicited a parallel cyclic excitability modulation of the observer's H-reflex and MEP responses with identical period as the observed movement. Modulation was phase advanced, as is muscle activation with respect to the real movement. The same results were obtained when the observed hand oscillation was executed with different frequency (1.6 Hz) and when the hands of mover and observer were supine. No motor resonance was elicited by observing the oscillation of a metal platform. The excitability modulation of MEPs simultaneously monitored in both antagonists of the observer's forearm (FCR and Extensor Carpi Radialis, ECR) was in almost perfect phase opposition, reflecting their natural reciprocal activation during the execution of a hand oscillation. These findings suggest that during observation, motor pathways are modulated subliminally reproducing with high temporal fidelity the motor commands needed to execute the observed movement.
Adult↗
Differential proliferative responses of B cells from BALB/c and autoimmune NZB mice to B-cell growth factor(s).
Highly purified B cells from NZB mice have altered responses to various stimuli which require additional costimulatory signals supplied by factors present in EL-4 supernatants when compared to age-matched control nonautoimmune strains. Both crude preparations of EL-4 supernatants as well as partially purified BSF-p1 induced peak proliferation in B cells from normal strains of mice only in the presence of another stimulatory signal, anti-mu. In contrast, B cells from autoimmune-prone NZB mice proliferated in response to B-cell growth factors, with an age-dependent variation. Splenic B cells from 16- to 22-week-old NZB mice, an age where pronounced autoimmune disease is not observed, demonstrated a near maximum proliferative response with B-cell growth factors alone. While normal B cells responded maximally to BSF-p1 in the presence of anti-mu, B cells from young adult NZB mice (16-22 weeks of age) were not further stimulated to proliferate upon the addition of anti-mu. Such NZB B cells appeared to lack the requirement for a stimulation signal delivered by anti-mu in order to respond to B-cell growth factors. These results suggested that NZB cells were partially activated in vivo in the preautoimmune state so that subliminal triggers lead to full activation.
Animals↗
The effect of transcranial magnetic stimulation on the soleus H reflex during human walking.
1. The effect of transcranial magnetic stimulation (TMS) on the soleus H reflex was investigated in the stance phase of walking in seventeen human subjects. For comparison, measurements were also made during quiet standing, matched tonic plantar flexion and matched dynamic plantar flexion. 2. During walking and dynamic plantar flexion subliminal (0.95 times threshold for a motor response in the soleus muscle) TMS evoked a large short-latency facilitation (onset at conditioning-test interval: -5 to -1 ms) of the H reflex followed by a later (onset at conditioning-test interval: 3-16 ms) long-lasting inhibition. In contrast, during standing and tonic plantar flexion the short-latency facilitation was either absent or small and the late inhibition was replaced by a long-lasting facilitation. 3. When grading the intensity of TMS it was found that the short-latency facilitation had a lower threshold during walking than during standing and tonic plantar flexion. Regardless of the stimulus intensity the late facilitation was never seen during walking and dynamic plantar flexion and the late inhibition was not seen, except for one subject, during standing and tonic plantar flexion. 4. A similar difference in the threshold of the short-latency facilitation between walking and standing was not observed when the magnetic stimulation was replaced by transcranial electrical stimulation. 5. The lower threshold of the short-latency facilitation evoked by magnetic but not electrical transcranial stimulation during walking compared with standing suggests that cortical cells with direct motoneuronal connections increase their excitability in relation to human walking. The significance of the differences in the late facilitatory and inhibitory effects during the different tasks is unclear.
Cerebral Cortex↗
Plasticity of dorsal horn cell receptive fields after peripheral nerve regeneration.
1. The tibial and sural nerves were transected and repaired in nine adult cats. The receptive field (RF) properties of dorsal horn neurons were examined at three different intervals (5-6, 9, or 12 mo) after axotomy. The properties examined included RF location, area, and modality convergence. In some cases, discrete areas of the cell's RF were stimulated electrically while the evoked cord dorsum potentials (CDPs) and any intracellularly recorded responses were simultaneously recorded. 2. At the shortest interval following reinnervation, the somatotopic organization in the affected areas of the dorsal horn was lost. Dorsal horn cells that received input primarily from regenerated fibers had large, low-threshold excitatory RFs that contained much of the reinnervated skin. Those cells with RFs restricted to a fraction of the reinnervated skin had significant components of their RFs on the foot dorsum supplied by intact fibers (i.e., superficial peroneal nerve). 3. At longer intervals the somatotopic organization remained scrambled. Dorsal horn cell low-threshold RFs were significantly reduced in size. Many cells exhibited large areas of excitatory subliminal fringe and concise inhibitory RFs. In addition, those cells that responded to peripheral stimuli across a wide range of stimulus intensities (wide-dynamic-range cells) also exhibited plasticity in the relative sizes of their low- and high-threshold RFs. 4. At the shortest recovery time, focal electrical stimulation of the skin within the RF of an impaled cell and simultaneous recordings of the evoked CDPs and postsynaptic potentials revealed that at numerous locations within the initial large RFs, single fibers or small groups of fibers could be electrically activated that were not connected to the dorsal horn cell. At the longer recovery times there was a much higher incidence of connectivity. 5. These results suggest that mechanisms affecting both synaptic efficacy of afferent fiber connections and/or the establishment of afferent-driven inhibitory inputs may effect the reshaping of dorsal horn cell RFs after reinnervation. These results are discussed in relation to their potential contribution to previously observed cortical plasticity and functional recovery following similar lesions.
Animals↗
The carotid chemoreceptor input to the respiratory neurones of the nucleus of tractus solitarus.
1. An investigation has been made into the connexions between the carotid body chemoreceptors and the dorsal respiratory neurones of the cat's medulla.2. In confirmation of previous work these neurones were found to be all inspiratory in firing pattern and to fall into two categories, Ralpha (forty-four units) which fire only with the central inspiratory rhythm and Rbeta (thirty-two neurones) that are also excited by lung inflation. Both categories were shown to be excited by stimuli delivered to the carotid bodies during inspiration but, with a single exception, not during expiration.3. When Rbeta neurones were made to fire tonically in expiration by maintained lung inflation, chemoreceptor activation inhibited this discharge in 7/11 cases, the remainder being unaffected.4. Iontophoretically applied DL-homocysteic acid or glutamate made both Ralpha and Rbeta neurones fire tonically in expiration. Chemoreceptor stimulation during expiration inhibited this activity in all neurones tested (nine Ralpha and three Rbeta cells).5. Using the measurement of the antidromic latency to spinal stimulation as an index of membrane potential, evidence was obtained that any subthreshold influence of the chemoreceptors on dorsal respiratory neurones during expiration was inhibitory (9/18 cases).6. It is concluded that chemoreceptors do not even subliminally excite dorsal inspiratory neurones during expiration; such influence as they have then is inhibitory. Possible reasons for this difference in chemoreceptor influence during inspiration and expiration are discussed. It is suggested that chemoreceptor excitation reaches them only as part of an enhanced central inspiratory drive from an as yet unknown source.
Action Potentials↗