Push-pull perfusion of pentylenetetrazol in the brain stem of 'encéphale isolé' cats

Nine 'encéphale isolé' cats had 'push-pull' perfusions of pentylenetetrazol (PTZ) in various loci of the brain stem, while the EEG from the right and left motor cortices, EMG from neck muscles, ocular movements and clinical changes were recorded. Perfusions in the rostral MRF induced bilateral rhythmic paroxysmal EEG discharges and myoclonic twitching of neck and head, more prominent in the muscles contralateral to the perfused side. PTZ in the caudal MRF induced tonic-clonic paroxysmal EEG discharges and EMG seizures, similar to those seen when PTZ is injected systemically. Perfusion in the PRF induced EEG spindle bursts, muscular hypotonia and myosis. When perfusion in the MRF inducing rhythmic paroxysmal EEG discharges and myoclonic twitching was followed by perfusion in the PRF, the EEG discharges were not modified, but the myoclonic movements were abolished. Perfusions outside the MRF and PRF did not produce obvious changes other than tonic gaze deviation to the contralateral side or nystagmus. The results suggest that PTZ has a differential effect in various structures of the CNS, producing primary generalized convulsive seizures when acting directly on the MRF.

[Limbico-reticular relations during formation of various motivation responses in rabbits subjected to ethanol administration]

Chronic experiments on rabbits with electrodes implanted into different limbic-midbrain structures were made to study the effects of a single intravenous injection of ethanol (0.5 g/kg) on the background EEG during formation of food motivation and avoidance behavior from the criterion of the power of the main EEG rhythms. Intravenous injection of ethanol resulted in an increase in the power of beta-, alpha- and theta-rhythms in the frontal cortex, and in that of alpha- and theta-rhythms in the occipital area of the neocortex. New patterns of the powers of the main EEG rhythms recorded in animals exposed to ethanol during electric stimulation of the lateral and ventromedial hypothalamus, evoking food motivation and avoidance behavior, as well as during electrical stimulation of the dorsal hippocamp and mesencephalic reticular formation that correlate with changes in the functions of the study limbic-mesencephalic structures attest to profound ethanol-induced abnormalities of the central mechanisms of food motivation and avoidance behavior.

Painful sensation induced by a thermal cutaneous stimulus

This review emphasizes how little we know about pain induced by a thermal stimulus. The study of the intensity of pain evoked by heat is relatively exhaustive: the influence of various local, stimulus-dependent or general factors upon threshold values has been well studied, as has the relation between pain and stimulus intensities. On the contrary, few studies have used very cold stimuli, since highly efficient stimulators allowing accurate control of the stimulus parameters have been obtainable only recently. Only the influence of stimulation area and stimulation rate on cold pain thresholds have been studied. Moreover, old results obtained on pain quality cannot be used since the conditions of stimulation were not specified or not controlled accurately. It is only known that stimulus duration and stimulation area are determinant for thermal pain quality. There is still much work to be done in this field. All the more so as this type of study is absolutely necessary for the understanding of pain mechanisms--it describes what must be explained by the function of the nervous system. We have seen that at the periphery the intensity of heat pain is coded by the response of polymodal nociceptors, mechanothermal nociceptors, thermal nociceptors and possibly by the paradoxical discharge of cold receptors. If the stimulus is lower than 45 degrees C the activity of certain heat receptors comes into play. Although we lack information which would allow confirmation of this as a fact it seems likely that the activity of polymodal nociceptors, cold mechanothermal nociceptors and possibly certain cold receptors sensitive to very low temperatures code cold pain. These nociceptive impulses carried by A delta and C fibers reach the dorsal horn of the spinal cord through the dorsal roots. They are notably at the origin of the activation of the neurons in Rexed's layers I, V and VIII which are to a large extent at the origin of the spinothalamic and spinoreticulothalamic tracks [21,115,168] moving in the anterolateral quadrant of the spinal cord. At supraspinal level, the thermal information reappears in the reticular formation; there it appears to be solely relative to the pain threshold and not to the intensity of a supraliminary stimulus [55]. In the posterior group of nuclei [134] and the ventroposterolateral nucleus of the thalamus [103], on the contrary, the activity of the neurons reflects the intensity of the stimulation. It has been proved that the neurons of the ventroposterolateral nucleus project onto the SI cortex [103].(ABSTRACT TRUNCATED AT 400 WORDS)

The one-and-a-half syndrome--a unilateral disorder of the pontine tegmentum: a study of 20 cases and review of the literature

The one-and-a-half syndrome is a clinical disorder of extraocular movements characterized by a conjugate horizontal gaze palsy in one direction plus an internuclear ophthalmoplegia in the other. The syndrome is usually due to a single unilateral lesion of the paramedian pontine reticular formation or the abducens nucleus on one side (causing the conjugate gaze palsy), with interruption of internuclear fibers of the ipsilateral medial longitudinal fasciculus after it has crossed the midline from its site of origin in the contralateral abducens nucleus (causing failure of adduction of the ipsilateral eye). Twenty cases are reported; 14 had multiple sclerosis.

Contingent negative variation and psychopathology: frontal-central distribution, and association with performance measures

Central and frontal contingent negative variation (CNV) were studied in psychiatric patients - schizophrenics, nonschizophrenic psychotics, schizotypics, and neurotics (according to DSM III) - and in a normal control group. The early CNV components and postimperative negativity were significantly different in schizophrenic and in nonschizophrenic psychotics, in contrast with their scores on some attentional performance tests. Only the central CNV was significantly correlated with severity of diagnosis, but multivariate analyses indicated the importance of frontal CNV and postimperative negativity in this respect. Topographical characteristics of the CNV also seem indicative of severity of psychiatric disturbance. These results are integrated in a composite index for further study. The general trend showed a moderately high degree of shared variance of central CNV components and performance measures, but not in regard to the other CNV measures, with variation found across diagnostic groups. No significant associations were found between CNV measures and affective and social functioning, and with Eysenck's personality dimensions.

[Nature of "congestive" stimulation in emotional stress as a basis of cardiovascular disorders]

The role of the limbicoreticular structures of the brain in the mechanism of cardiovascular reactions to the electric stimulation of the emotiogenic zones of the ventromedial hypothalamus has been described in the paper. It is shown that during emotional reactions the sensitivity of certain neurons of the reticular formation of medulla oblongata to chemical stimulants and of the hypothalamus to neuromediators is changed. The importance of certain oligopeptides (angiotensin II, bradykinin, renin, and delta-sheep-producing peptide) in the genesis of cardiovascular disorders observed in the stimulation of the emotiogenic zones of the ventromedial hypothalamus has been elucidated.

Analgesia produced by microinjection of L-glutamate into the rostral ventromedial bulbar nuclei of the rat and its inhibition by intrathecal alpha-adrenergic blocking agents

Definite and dose-dependent analgesia followed microinjection of L-glutamate into the nucleus reticularis paragigantocellularis (NRPG) of rats. This analgesic effect was inhibited by lumbar intrathecal pretreatment with phenoxybenzamine and phentolamine but not by propranolol, methysergide or naloxone. Microinjection of L-glutamate into the nucleus raphe magnus (NRM) also produced an analgesic effect which was reduced by intrathecal pretreatment with methysergide but not by phentolamine. These findings provide direct evidence that the NRPG and NRM function separately in descending pain-suppression systems of the spinal cord.

Analysis of characteristic eye movement abnormalities in internuclear ophthalmoplegia

Quantitative electro-oculographic recording techniques were used to analyze four characteristic eye movement abnormalities in 21 patients with internuclear ophthalmoplegia (INO). The frequency of each of the abnormalities was determined to suggest a pattern that is the most sensitive in detecting the syndrome of INO. Slowing of the adducting saccade was the most frequently found abnormality, being present in all patients. The other characteristic eye movement disorders were found less frequently: dissociated nystagmus at 30 degrees of eccentric gaze, dysmetria of the abducting eye, and limitation of adduction. The most sensitive pattern for detecting an INO seems to be slowing of the adducting saccade combined with either dissociated nystagmus or dysmetria of the abducting eye. Limitation of adduction was seen much less frequently.

Observations on the connectivity of the parvicellular reticular formation with respect to a vomiting center

The intrinsic and extrinsic connections of the parvicellular reticular formation (PCRF) that have been demonstrated by fiber degeneration studies and studied by more recently introduced horseradish peroxidase retrograde cell labeling are reviewed in an attempt to delimit the connectivity of the region in the PCRF where electrical stimulation produced emesis. Evidence is presented that certain specific functional subdivisions in PCRF such as the salivatory nuclei and the cells which give rise to the vestibular efferent projections can be delimited. An attempt is made to differentiate the sources of brain stem afferent connections with the nucleus of the tractus solitarius, the vagal nucleus and the nucleus ambiguus complex. The literature bearing on the histochemistry of the brain stem is reviewed in a search for clues to possible unique histo- or immunochemical cytological subdivisions in the parvicellular reticular formation.

The physiology of pain: a review

Pain is a complex physiological phenomenon that begins with the stimulation of free nerve endings in peripheral tissues and culminates in the perception of a physical and psychological state. The pain experience may be facilitated or inhibited through the action of several neurologic circuits which utilize several neurotransmitters. Therapeutic analgesia is achieved either through interference with pain-facilitating mechanisms or enhancement of pain-inhibiting mechanisms; practical applications are reviewed.

A 1983 neuropharmacologic perspective of space sickness

Space sickness is generally considered a variant of motion sickness although not fully proved as such. Understanding space sickness requires objective and quantitative characterization of the disorder. Vomiting is a quantifiable physiological event performed by the respiratory muscles which generate the pressures that evacuate the gut. Vomiting from all causes is coordinated by the vomiting center in the medulla oblongata. The emetic chemoreceptor trigger zone (CTZ) in the area postrema is thought to be an indispensable element in the afferent pathway of motion sickness. About 30 potential neurotransmitters exist in the vomiting control mechanism which includes at least eight chemical transmission steps through the reflex pathway of motion sickness. Individual synaptic transmitters do not likely mediate specific functions, but particular combinations of those transmitters might well serve distinct functions. Adaptation to the cause of space sickness probably results from readjustment of a cerebellar circuit or of a humoral factor acting on the CTZ, rather than from stimulus-receptor desensitization. Space sickness must, for purposes of investigation, be treated as a unique disorder engendered by weightlessness until proved equivalent to any emetic syndrome that occurs on earth.

Vertical glaze paralysis and the rostral interstitial nucleus of the medial longitudinal fasciculus

The rostral interstitial nucleus of the medial longitudinal fasciculus in known to participate in the generation of fast vertical eye movements in the monkey. A cell group homologous to this nucleus has been identified in the human brain. In man the nucleus lies dorsomedial to the anterior pole of the red nucleus, rostral to the interstitial nucleus of Cajal, and lateral to the nucleus of Darkschewitsch. Reconstructions of lesions in patients with different types of vertical gaze paralysis show that destruction of the rostral interstitial nucleus of the MLF bilaterally leads to an impairment of fast vertical eye movements. We propose that the nucleus participates in the production of vertical saccades and quick phases of nystagmus in man. Preservation of its integrity is not necessary for the production of vestibular compensatory eye movements in the vertical plane.

Subcortical correlates of the auditory brain stem potentials in man: bipolar EEG and multiple unit activity and electrical stimulation

Bipolar EEG and multiple unit activity (MUA) responses related to the vertex auditory brain stem potentials (ABSP) were studied in different subcortical loci in parkinsonian and epileptic patients with implanted electrodes used as an electrophysiological procedure for surgical treatment. In addition, the subjective responses of patients to the electrical stimulation of these subcortical loci were studied for their possible auditory sensations. (1) Two types of bipolar EEG responses to monoaural stimulation were recorded from a limited number of subcortical loci: type A responses were formed by two consecutive components of opposite polarity peaking at 5.2 and 8.5 msec post-stimulus in 3 different loci contra- and ipsilateral to the stimulated ear: mesencephalic reticular formation (MRF), medial geniculate (MG) and lateral geniculate (LG) nuclei thalami. The polarity of the first component was everted while the second component was inverted between MRF and MG. Type B responses were formed by one component mainly peaking at 15.5 msec post-stimulus with no polarity reversal in either side within the ventral portion of the hippocampus bilaterally (CnA). (2) MUA responses were recorded only within the basal portion of MG bilaterally. Contralateral MUA responses consisted of 3 consecutive activation bursts peaking at 5.5, 7.2 and 9.0 msec post-stimulus and correlated in latency with waves IV-V, VI and VII of ABSP respectively. Ipsilateral MUA responses consisted of two consecutive activation bursts peaking at 14.0 and 16.0 msec post-stimulus and correlating with SN following ABSP. (3) Threshold electrical stimulation of the MG elicited subjective auditory responses referred to the contralateral ear.

[Informational significance of the dynamics of slow electrical processes in craniocerebral injuries]

CNS injuries in brain contusions of a moderate and severe gravity leave lasting EEG traces that can be revealed on examining the patients in the state of sleep and drowsiness, and manifest in the form of pathological oscillations of the slow electrical processes in the second and decasecond intervals. These oscillations have an amplitude of 0.2 to 1.0 mV and more. In the course of brain function normalization the amplitude of the oscillations gradually decreases down to 0.05-0.15 mV. The pathological oscillations of the slow electrical processes in brain contusions are often more demonstrative than EEG changes.

A model integrating risk variables involved in the development of the schizophrenia spectrum

A theoretical model of the etiology of schizophrenia, the schizophrenia spectrum, and normal development is proposed. This model is based upon replicated research. A selected review of the literature on the etiology of schizophrenia indicated that schizophrenia may be a developmental disorder of the quality of attachment interacting with the development of the reticulothalamocortical system, beginning in the earliest months of life. A genotype, phenocopy, and stress are specified, based upon replicated research results. We hypothesize that schizophrenia results from a continuing malforming transaction, beginning at birth, between a temperament genotype of a sensitive, easily aroused to high peaks of arousal baby and an environmental stress of an unempathic/insensitive, physically rejecting, noncontingent mother. This results in a classical conditioning paradigm wherein people become an aversive stimulus for an anxiously/avoidant attached infant. This anxious/avoidant response may have permanent biochemical and structural effects. It is also hypothesized that the same genotype interacting with an empathic, sensitive, physically affectionate, contingent mother may also account for artistically or musically creative superphrenics.

Effect of midbrain and pontine tegmental lesions on the maximal electroshock seizure pattern in rats

A bilaterally induced mechanical lesion of the midbrain was highly effective in abolishing the hindlimb extensor (HLE) component of the maximal electroshock seizures (MES) in rats. Although these lesions produced damage to a variety of midbrain structures, correlations between different lesion placements and effects in the MES test provided evidence that damage to superior cerebellar peduncle (PCS) and/or reticular formation (RF) was responsible for inhibition of hindlimb extension. Moreover, discretely placed electrolytic lesions disrupting either the PCS or the RF were found to abolish the hindlimb extensor component of the MES test. These findings are consistent with the work of other investigators showing that total cerebellectomy abolishes the HLE component of MES and suggest that activity in the cerebellum and the midbrain reticular formation plays a major role in regulating the tonic phase of electroshock induced seizures.