Neural pathways mediating vaginal function: the vagus nerves and spinal cord oxytocin

The initial observations, made in our laboratory with Knut Larsson, of the ability of vaginocervical stimulation (VCS) to block withdrawal responses to foot pinch in rats has led to findings of multiple behavioral, autonomic, and neuroendocrine effects of this potent stimulus in rats and also in women. It has led to an understanding of: (1) the neuroanatomical and neurochemical basis of a novel and potent pain-blocking mechanism; (2) likely neuroanatomical pathways mediating both the Ferguson reflex and a specific autonomic response - the pupil-dilating effect of VCS; (3) a role for oxytocin as a putative central nervous system neurotransmitter that stimulates autonomic sympathetic preganglionic neurons within the spinal cord; and (4) a novel pathway that can convey sensory activity from the cervix, adequate to induce orgasm, via the vagus nerves. This latter pathway bypasses the spinal cord and projects directly to the medulla oblongata, and thus can convey genital afferent activity despite complete spinal cord injury at any level.     

Selective unilateral autonomic activation: implications for psychiatry

Research advances have led to three methods for selectively activating one half of the autonomic nervous system in humans. The first method is an ancient yogic technique called unilateral forced nostril breathing (UFNB) that employs forced breathing through only one nostril while closing off the other. The second method works by stimulation of an autonomic reflex point on the fifth intercostal space near the axilla. The most recent method employs unilateral vagus nerve stimulation (VNS) via the mid-inferior cervical branch and requires surgical implantation of a wire and pacemaker. UFNB is non-invasive and seems to selectively activate the ipsilateral branch of the sympathetic nervous system with a possible compensation effect leading to contralateral VNS. UFNB and VNS have been employed to treat psychiatric disorders. While UFNB has been studied for its potential effects on the endogenous ultradian rhythms of the autonomic and central nervous system, and their tightly coupled correlates, VNS has yet to be studied in this regard. This article reviews these three methods and discusses their similarities, putative mechanisms, their studied effects on the endogenous autonomic nervous system and central nervous system rhythms, and their implications for the treatment of psychiatric disorders.     

An Analysis of the Bilateral Transfer of Conditioning in Dogs,in Terms of the Frequency,Amplitude, and Latency of the Responses

Twenty volunteer male college students were exposed to motion picture films which reliably elicit symptoms of motion sickness. Those Ss with relatively higher apparent sympathetic nervous system dominance showed significantly smaller autonomic reactions to the film. It was concluded that increased sympathetic tone tended to reduce autonomic reactions to motion sickness stimuli. It was suggested that the sympathetic nervous system symptoms that usually occur in motion sickness are actually defensive reactions rather than symptoms of nausea.     

Psychopharmacology and conditional reflexes

Drugs may be used in several ways to investigate their role in behavior. (1) The placebo effect is usually connected with the relation of the person to the drug. (2) Using the drug as an unconditional stimulus, its action may help to analyze the role of peripheral vs. central stimuli in the formation of conditional reflexes; our work has shown that the effect of drugs which act solely at the peripheral nerve endings without the involvement of the central nervous system cannot become conditioned. (3) The action of drugs on the conditional reflex (CR) compared with their action on the unconditional reflex (UR) explains some of their behavioral effects. (4) Schizokinesis is often prominent in the action of drugs. Although a drug may increase the level of the heart rate, for example, it can, on the other hand, diminish the reactivity shown in the CR. Meprobamate and mescaline affect differently the cardiac and the motor components of the CR, illustrating a schizokinesis. (5) The type of individual is an important factor in the action of drugs; the same drug may have opposite effects on different individuals. This leads to the conclusion that a drug should fit the individual as well as the disease. (6) Autokinesis is often seen in drug action. Therefore a single dose of some drugs, such as acetylcholine, epinephrine or LSD, may permanently change the relationships between excitation and inhibition, in the direction of improvement or deterioration (positive or negative autokinesis).     

Phase-dependent reflex modulation in tibialis anterior during passive viewing of walking

It is well established that reflexes are highly adaptive, as they depend both on our intention and on the active state of the muscles. Reflex gains change dynamically during actions such as walking and running, with the gain of cutaneous reflexes being increased at the end of the stance phase but decreased at the end of the swing phase in the tibialis anterior (TA) muscle. Reflex gains can even change during the mere observation of an action. The mechanisms and functions of such modulations are unclear. It has been suggested that the changed reflex gains prevent the actual performance of actions that we see. However, the modulation of reflexes in response to seeing an action has never been reproduced for the active execution of such actions. In the present study, medium-latency cutaneous reflexes from the TA muscle, of which the activity and reflexes during walking are well known, were measured in human subjects. The results show that the gain changes of the medium-latency responses of the TA are the same as during active walking. We conclude that reflexes do not represent an inhibitory mechanism that prevents motor output during action observation. Instead, our findings provide evidence that even the peripheral spinal motor system is actively involved in the motor resonance processes, without evoking any measurable motor responses.     

Conditioning of successive adaptive responses to the initial effects of drugs

Data in the literature indicate that conditioned responses (CRs) generated by repeated pairing of conditional stimulus (CS) with administration of a neurotropic drug may resemble its unconditional effects or they may be opposite in direction; furthermore, the CRs may change as such pairings are continued. In explanation, it is hypothesized that as in conditioning of physiological reflexes, a CS repeatedly paired with administration of a neurotropic drug eventually comes to activate central“processing” events that are evoked by the“stimulus” properties of the drug,i.e., the effects of the drug at receptor sites inside or outside the pia mater which lie in the afferent arms of“reflex” neural circuits; or, the CS comes to activate central processing events that are evoked by centripetal feedback responses to the effects of the drug at receptor sites in the processing or efferent arms of reflex neural circuits. Depending on the receptor site action of the drug, the conditioned autonomic and/or neuromuscular responses that are observed may be in the same direction as, or opposite in direction to the unconditioned effects of the drug. With continued pairings of CS and drug, the unconditioned processing events evoked by the stimulus properties of the drug, and hence the CRs also, change in consequence of compensatory (sometimes“overshooting”) biochemical alterations proximal to the receptor site of action of the drug, induced by negative or positive neuronal feedback mechanisms. These concepts are utilized in a theory of opiate addiction and relapse.     

Temporal integration of acoustic and cutaneous stimuli shown in the blink reflex

Temporal integration of pairs of brief blink-eliciting acoustic and cutaneous stimuli was investigated to determine if there was integration of stimuli from different modalities. Reflexes elicited by a tone burst or by a brief electrical shock to the supraorbital nerve followed by a second tone burst or shock at short stimulus onset asynchronies (SOAs) were larger and faster than control reflexes elicited by a single stimulus identical to the lead stimulus of the stimulus pairs. Reflex amplitude was augmented at longer SOAs where there was no effect on latency. Temporal integration was evident for all stimulus pairs, showing that it is due, at least in part, to processes that occur outside specific sensory pathways. Heterogeneous stimulus pairs produced greater reflex enhancement than did homogeneous stimulus pairs. This finding was examined further in Experiment 2, which showed that reflex enhancement with pairs of acoustic pulses was unaffected by the frequency of the second stimulus, suggesting that sensory masking was not acting to suppress reflex expression with acoustic pulse pairs. Integration of reflexogenic acoustic stimuli shown in the blink reflex is restricted to shorter intervals than is integration of acoustic stimuli shown by psychophysical procedures, suggesting that the two methods reflect different aspects of stimulus processing. Integration of reflexogenic stimuli may result from summation of activity associated more directly with reflex expression than with perceptual awareness.     

Stretch reflexes in the human masticatory muscles: a brief review and a new functional role

Stretch reflexes play a vital role in fine-tuning movements and in automatically maintaining posture. This article briefly reviews the operation of the stretch reflex in the human masticatory system. The conventional approach of stretching muscles in an open-loop manner has yielded much valuable information on the operation of this reflex. In particular, it has revealed that stretching the jaw-closing muscles evokes a reflex response with two major components. The short-latency reflex is favoured when stretches are brisk, but slower stretches evoke an additional long-latency component. In the hand muscles, the long-latency response is transcortical: in the masticatory muscles, it is not. In addition to its role in servo-control of muscle length during chewing, the stretch reflex in the jaw-closing muscles maintains the vertical position of the mandible during vigorous head movements such as those that occur during running, jumping, hopping and other vigorous whole-body movements in which the head moves briskly up and down. This is an interesting model system in which to investigate stretch reflexes with natural stimuli under unrestrained, physiological conditions.     

Higher reflexes

The term reflex is used in a broad sense. Reflexes having a drive component are denoted as higher. Four types of higher reflexes are distinguished: avoidance, escape approach and consummately. Each of these reflexes has a different drive component. The result of the reflex is a removal of the corresponding drive. For this purpose three different strategies are used. Complex higher reflexes are usually programmed and occur frequently in a chain form. A given function of an organism is performed by a system of reflexes controlled by one or more drives.     

Retention of a classically conditioned reflex response in spinal cat

Retention of classically conditioned flexion reflex facilitation was examined in unanesthetized, decerebrate, acute spinal cats. Flexion reflex facilitation, recorded from the tibialis anterior muscle, was obtained by pairing saphenous nerve stimulation (the conditioned stimulus) with superficial peroneal nerve stimulation (the unconditioned stimulus). The flexion reflex declined in control animals receiving the same number of nerve stimuli over the same time span, but in an explicitly unpaired sequence. To investigate retention, conditioned stimuli were presented at 5-min intervals following acquisition for a 2 1/2-h period. During this time a significant difference between conditioning and control groups was maintained even to the last trial, with no indication that the difference was subsiding over time. The results support the possibility that a classical conditioning paradigm applied to the spinal cord can induce alterations in spinal reflexes of long duration. Furthermore, the results appear to rule out post-tetanic potentiation as a mechanism producing the observed long-term effects.     

Psychophysiological mechanisms involved in the affective regulation and food restriction of women at risk of suffering from bulimia nervosa

The aim of the study was to explore the effect of visualizing food images under different mood states and food restriction conditions on the emotional modulation of two defense reflexes (startle reflex and cardiac defense). 72 women at risk of suffering from bulimia nervosa were assigned to two groups: 1) a group under induced positive, neutral, or negative mood state and, 2) a 6-hour-food-deprived group or a non-deprived group. Second-by-second heart rate and electromyogram activity from the orbiculari oculi region were recorded after the auditory stimulus. The results showed that, while viewing food images, non-deprived women under negative mood state potentiated the cardiac defense response and the startle motor reflex. Results are discussed in the context of emotional eating theories and Peter Lang's motivational priming model.     

Development of selective attention in young infants: Enhancement and attenuation of startle reflex by attention

This study examined the effect of level of attention engagement on the modification of the blink reflex in young infants. Infants at 8, 14, 20, or 26 weeks of age were presented with interesting visual or auditory stimuli. At delays defined by changes in heart rate known to be associated with sustained attention or attention disengagement, blink reflexes were elicited by visual or auditory blink reflex stimuli. Blink amplitude varied according to the level of attention, and the match between the foreground and blink reflex stimulus. If the infant was attending to the foreground stimulus, a blink reflex stimulus in the same modality resulted in enhanced blink reflex magnitude. A blink reflex stimulus in the other modality resulted in an attenuated blink reflex magnitude. If attention was not engaged with the foreground stimulus, this modulation of the blink reflex did not occur. This ‘selective modality effect’ showed an increasing tendency to occur between 8 and 26 weeks of age. These results show that selective attention to modalities increases over this age range.     

Sympathetic nervous system and pain: a clinical reappraisal

The target article discusses various aspects of the relationship between the sympathetic system and pain. To this end, the patients under study are divided into three groups. In the first group, called "reflex sympathetic dystrophy" (RSD), the syndrome can be characterized by a triad of autonomic, motor, and sensory symptoms, which occur in a distally generalized distribution. The pain is typically felt deeply and diffusely, has an orthostatic component, and is suppressed by the ischemia test. Under those circumstances, the pain is likely to respond to sympatholytic interventions. In a second group, called "sympathetically maintained pain" (SMP) syndrome, the principal symptoms are spontaneous pain, which is felt superficially and has no orthostatic component, and allodynia. These symptoms, typically confined to the zone of a lesioned nerve, may also be relieved by sympathetic blocks. Since the characteristics of the pain differ between RSD and SMP, the underlying kind of sympathetic-sensory coupling may also vary between these cases. A very small third group of patients exhibits symptoms of both RSD and SMP. The dependence or independence of pain on sympathetic function reported in most published studies seems to be questionable because the degree of technical success of the block remains uncertain. Therefore, pain should not be reported as sympathetic function independent until the criteria for a complete sympathetic block have been established and satisfied.     

The smoke reflex in rabbits an example of autonomic control of cardiorespiratory function

This study was undertaken to elucidate aspects of autonomic behavior as reflected in the “smoke reflex” in rabbits. Allowing smoke to envelop the nostrils of a rabbit resulted in prompt apnea, bradycardia, diminution of peripheral pulse and elevation of systemic blood pressure. Atropine and vagotomy, or both, mitigated the bradycardia, but the combined effect of propranolol and vagotomy was required to abolish bradycardia. Phenoxybenzamine (dibenzyline) alone blocked only the peripheral vasoconstriction and pressor response. The combination of vagotomy, propranolol and phenoxybenzamine blocked all manifestations of the reflex with the exception of apnea. A classical concept holds that responses of the autonomie nervous system must be either distinctly adrenergic (sympathetic) or cholinergic (parasympathetic), and that visceral regulation is achieved by an antagonism between the two. This study introduces contrary evidence and demonstrates that in certain adaptive behavior there is a patterned response that includes activation of discrete elements of both cholinergic and adrenergic divisions, as well as inhibition of one component of the latter.     

Odogenic change of blood coagulation in humans.

The blood coagulation time as an integral sign of human homeostasis is revealed to be influenced by conscious or unconscious olfactory stimuli through autonomic mechanisms. The hemostasis of subjects with predominance of sympathetic activity is more sensitive to the olfactory stimuli than that of subjects with vagal prevalence. The effects of the olfactory stimuli upon hemostasis in humans support the viewpoint that simultaneous information and physico-chemical processes act together in parallel to play and important role in life activities of human organism (Simonov, 1981; Sudakov, 1995). Emotions, therefore, are essential in the transfer of information from the environment (Anokhin, 1966; Miltner et al., 1994). It is not excluded that even very weak stimuli which are subthreshold for conscious perception might be informational for the organism as those engaging emotional response.     

The Moro reaction: More than a reflex,a ritualized behavior of nonverbal communication

ObjectiveTo propose a phylogenetic significance to the Moro reflex which remains unexplained since its publication in 1918 because both hands are free at the end of the gesture.MethodAmong the 75 videos of healthy term newborns we have filmed in a research project on antenatal education to parenthood, we describe a sequence that clearly showed the successive movements of the Moro reflex and we report the occurrence of this reflex in the videos that were recorded from Time 0 of birth defined as the moment that lies between the birth of the thorax and the pelvis of the infant.ResultsThe selected sequence showed the following succession of the newborn’s actions: quick extension-adduction of both arms, the orientation of the body, head and eyes towards a human person, and full extension-abduction of both arms with spreading of the fingers, crying and a distressed face. There were 13 Moro reflexes between 2 and 14 s from Time 0 of birth. We found a significant association between the occurrence of the Moro reflex and the placement of the newborn at birth in supine position on the mother’s abdomen (p = 0.002).DiscussionThe quick extension-adduction of both arms which started the sequence may be considered as a startle reflex controlled by the neural fear system and the arm extension-adduction which followed as a Moro reflex. The characteristics of all Moro reflexes were those of ritualization: amplitude, duration, stereotype of the gestures. This evolutionary process turns a physiological behavior, grasping in this case, to a non-verbal communicative behavior whose meaning is a request to be picked up in the arms. The gestures associated with the Moro reflex: crying and orientation of the body, head, and eyes towards a human person, are gestures of intention to communicate which support our hypothesis. The neural mechanism of the Moro reaction probably involves both the fear and the separation-distress systems.ConclusionThis paper proposes for the first time a phylogenetic significance to the Moro reflex: a ritualized behavior of nonverbal communication. Professionals should avoid stimulating the newborns’ fear system by unnecessarily triggering Moro reflexes. Antenatal education should teach parents to respond to the Moro reflexes of their newborn infant by picking her up in their arms with mother talk.     

Odogenic change of blood coagulation in humans

The blood coagulation time as an integral sign of human homeostasis is revealed to be influenced by conscious or unconscious olfactory stimuli through autonomic mechanisms. The hemostasis of subjects with predominance of sympathetic activity is more sensitive to the olfactory stimuli than that of subjects with vagal prevalence. The effects of the olfactory stimuli upon hemostasis in humans support the viewpoint that simultaneous information and physico-chemical processes act together in parallel to play and important role in life activities of human organism (Simonov, 1981; Sudakov, 1995). Emotions, therefore, are essential in the transfer of information from the environment (Anokhin, 1966; Miltner et al., 1994). It is not excluded that even very weak stimuli which are subthreshold for conscious perception might be informational for the organism as those engaging emotional response.     

Measurement of muscle reflex time in radicular disorders of the lumbosacral region]

The results of studies performed by the authors show that time measurements of proprioceptive muscular reflexes (triceps surae and tibialis posterior reflexes) may be considered a valuable addition to methods of topical diagnosis of radicular disturbances in the lumbosacral region. The reflexes were tested in twenty normal subjects. There were found an intraindividual constancy of the respective reflex time with a maximum deviation of 2 ms as well as a lateral variability up to 1.3 ms. Radicular compressions resulted in an increase in reflex time by 2 to 66 ms or failure of the reflex potential to be recorded. The pathological cases were compared with clinical and neurological studies, positive myelographies using radiopaque substances, and results of surgical operations. Compared with the results of surgical operations, changes in reflex time indicated damage to the reflex arc in ninety percent of the cases.     

Complex form of instrumental behavior of dogs

A complex form of higher nervous activity, conditional reflex transswitching or switching, was elaborated in four dogs under conditions of unrestrained movements, freedom of reinforcement choice (food or water), place of reinforcement determined by situation factors as well as independent switching on of conditional stimuli. It was shown that motivated goal-directed behavior of the animals was determined by activation of forward and backward connections. The chains of instrumental conditioned reflexes forming in the final analysis the complex behavior are developed according to the “trialand-error” principle. In the instrumental conditioned reflexes there are two constantly coexisting types of mutually complementing conditioned connections of the signal with reinforcement—direct and indirect. In experiments with unrestrained conditions of animals and independent regulation of the experiment, one of the frequently encountered physiological mechanisms of generalization appears to be efferent and afferent generalization.     

Heart rate—QT relationships during baroreceptor stimulation with diminished autonomic influence on the ventricles

The shortening of the QT interval of the electrocardiogram coincident with acceleration of heart rate and vice versa has been accepted for many years as evidence that the action potential duration and hence QT are necessarily dependant on heart rate. Exceptions to this rule have been attributed to the intervention of counteracting autonomic effects. In order to test this assumption, 26 conscious dogs divided into three groups were tested during baroreceptor stimulation by a bolus injection of phenylephrine. Seventeen dogs had been used in earlier studies in which they had undergone an experimental anterior myocardial infarction with apparent full recovery. A group of those dogs underwent beta-adrenergic blockade by intravenous atenolol 30 min prior to the baroreceptor activation. To test the intactness of the baroreceptor responses in the previously infarcted dogs, a third group of nine dogs that had had no prior myocardial infarction was included. All dogs were adapted to the laboratory environment and were not sedated during experiments. Simultaneous recordings of RR, QT interval, and phasic arterial pressure were made in all dogs before and during baroreceptor stimulation. In the normal group, and the previously infarcted group that received no atenolol, baroreceptor stimulation elicited a small (8/msec), but significant prolongation of the QT associated with a nearly 50% reduction in heart rate. The QT interval of the atenolol-treated dogs, although significantly more prolonged before stimulation, remained unchanged during the reflex. The data indicate that withdrawal of ventricular sympathetic tone may prolong the QT interval, thereby confirming the role of sympathetic innervation in the control of QT. This inference was strengthened by the complete absence of change of QT after atenolol block and the absence of any detectable influence of vagal activity on ventricular repolarization during the reflex. Therefore, in what appeared to be the absence of evidence of autonomic influence, no inverse relationship between heart rate and QT was observed.