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Biomedical subjects

F Velasco

Publications and source records attributed to F Velasco.

At least 145 records · Page 8Linked to original sources
PubMed1980

Specific and non-specific multiple unit activities during pentylenetetrazol seizures. I. Animals with 'encéphale isolé'.

The present report describes the sequence of activation and deactivation of multiple unit activities (MUA) in the brain stem reticular formation and pyramidal tract, in relation to the clinical seizure and electroencephalographic and electromyographic tonic-clonic discharges induced by pentylenetetrazol (PTZ), in cats immobilized by high spinal transection ('encéphale isolé'). Threshold doses of PTZ (20 mg/kg i.v.) produced the following events: (1) Significant increase in mesencephalic and pontine MUA, anticipating 2 (+/- 1) sec the clinical and electromyographic seizures and 5 (+/- 2) sec the onset of EEG and pyramidal tract tonic-clonic discharges. (2) A further increase in mesencephalic and pontine reticular MUA and electromyogram MUA at the onset of EEG and pyramidal tract tonic-clonic discharges. (3) Significant decrease of EEG spike activity and pyramidal tract MUA to levels below the control period 16 (+/- 8) sec later, while mesencephalic and pontine MUA and electromyogram remained very high. Results suggest that (i) PTZ-induced seizures start in the brain stem reticular formation and propagate to muscles by at least two different pathways: a pyramidal and an extrapyramidal pathway; (ii) that inhibition of seizure activity may start at the cortical level.

Action Potentials↗
PubMed1980

Plasma prolactin increase following electric stimulation of the amygdala in humans.

Plasma levels of PRL, GH, FSH, LH, and TSH were studied at various intervals after electric stimulation of the amygdala, in 5 patients in whom electrodes had been chronically implanted in the course of their evaluation for surgical treatment of uncontrollable, temporal lobe seizures. Electric stimulation, but not sham stimulation, elicited in all cases a significant rise in plasma PRL. Plasma GH rose only in 1 patient and TSH in another. No significant changes in plasma FSH or LH were detected. It is suggested that a fine control mechanism of the hypothalamic hypophyseal final common pathway for the control of PRL secretion, may be mediated either by the ventral amygdalohypothalamic pathway or via the stria terminalis.

Adolescent↗
PubMed1979

A peculiar rhythmic EEG activity from ventrobasal thalamus during paradoxical sleep in man.

A peculiar 3/sec rhythmic EEG activity (named Vc rhythm) was consistently found at the ventrobasal thalamus (nucleus ventrocaudalis) during paradoxical sleep of patients with implanted electrodes used as an electrophysiological procedure for identification of the thalamic targets for the surgical treatment of tremor and rigidity. The Vc rhythm was formed by high voltage, sharp biphasic positive negative potentials which were absent during wakefulness, rare and isolated during slow wave sleep, increased in number and organized in trains during paradoxical sleep and blocked during arousal. Significant changes in number of Vc waves were found when patients shifted through these wakefulness-sleep states. Integrated EMG multiple unit activity also showed significant changes during these wakefulness-sleep shifts, which were parallel although inverse to those showed by Vc waves. A significant negative correlation (r = -0.7126) between number of Vc waves and EMG units was found. In contrast, Vc waves showed no correlation with other electrophysiological indicators of thalamic excitability (multiple unit activity and early evoked potentials) and sleep (scalp EEG frequency and ocular movements).

Electric Stimulation↗
PubMed1979

Wakefulness-sleep modulation of thalamic multiple unit activity and EEG in man.

Quantitative changes in the number of EEG waves and MUA neuronal spikes of various thalamic nuclear groups were studied during steady and transitional wakefulness-sleep states in a group of patients with implanted electrodes, used as an electrophysiological procedure for the surgical treatment of unilateral tremor and rigidity. Thalamic nuclei included ventroposterolateral (VPL), ventrolateral (VL) and centromedian (CM). Steady states included initial wakefulness (W1), slow wave sleep (SWS) I, II, IV and IIL, paradoxical sleep phasic (PSP) and tonic (PST) and final wakefulness (W2). Transitional states included transition from SWS to PSP (transition) and from sleep to W2 (arousal). (1) There was a significant correlation in EEG and MUA between different thalamic nuclei simultaneously recorded in the same patient during different steady-states. (2) Thalamic MUA significantly decreased from W to SWS, increased from SWS to PS and SWS to W2, while thalamic EEG significantly decreased from W to SWS, increased from SWS to W2 but was not significantly modified from SWS to PS, consecutive steady-state shifts. (3) Thalamic MUA significantly decreased while EEG remained unchanged from PSP to PST consecutive steady-state shifts. (4) Both thalamic MUA and EEG significantly decreased from SWS II to IIL while they were not systematically modified from W1 to W2 indirect steady-state shifts. (5) Thalamic MUA significantly increased 1 sec before transition and arousal while EEG increased 5 sec after arousal and did not change during transition.

Adult↗
PubMed1979

A reticulothalamic system mediating proprioceptive attention and tremor in man.

This report descirbes the electrophysiological characteristics of thalamic and subthalamic targets used to control tremor. In these targets exploratory electrodes recorded one or more of the following events. Electrical stimulation produced enhancement of tremor or other complex motor responses. Somatic evoked potentials (SEPs) induced by proprioceptive stimulation showed only late components, the amplitudes of which changed in various attentive situations. Multiunit activity showed spontaneous 3- to 6-Hz rhythmic bursts. And a lesion produced neglect of contralateral extremities and an ipsilateral decrease of scalp-recorded SEP late components. In contrast, in the areas located immediately posterior and dorsal, electrical stimulation produced contralateral paresthesias. Early components of SEPs could be recorded, as were rhythmic bursts of multiunit activity after the occurrence of peripheral tremor. Lesions produced sensory deficits in the contralateral extremities and ipsilateral blocking of all components of scalp SEPs. The latter areas are identified as the lemniscal system, but the former seem to be extralemniscal. Their electrophysiological characteristics suggest that they are probably involved in the process of selective attention and motor control.

Attention↗
PubMed1976

Specific and nonspecific multiple unit activities during the onset of pentylenetetrazol seizures. II. Acute lesions interrupting nonspecific system connections.

Nonspecific cortical, thalamic, mesencephalic, and pontine multiple unit activities (MUA) and changes in EEG and MUS of the sciatic nerve after threshold pentylenetetrazol activation were studied in three groups of animals in which neuronal connections were interrupted at three different levels of the central nervous system: spinal, mesencephalic, and prethalamic. Maximal increments of nonspecific MUA and maximal increments and maximal decrements of sciatic MUA after pentylenetetrazol from each group of lesioned animals were statistically compared with tose observed in intact animals. 1. Pentylenetetrazol threshold for producing cortical tonic-clonic EEG discharges was increased in animals with nesencephaic and prethalamic lesions but was not modified in animals with spinal transection. 2. Cortical MUA maximal increment was significantly decreased in mesencephalic and prethalamic lesioned animals, whereas thalamic MUA maximal increment was significantly decreased in mesencephalic and significantly increased in prethalamic lesioned animals. Pontine MUA maximal increment was significantly increased in spinal, mesencephalic, and prethalamic lesioned animals, and mesencephalic M-A maximal increment was not significantly modified in either prethalamic lesioned or in spinal transected animals. 3. Sciatic MUA maximal increment and maximal decrement were significatly decreased in spinal transected animals, whereas only maximal increment was significantly decreased in mesencephalic and only maximal decrement was significantly decreased in prethalamic lesioned animals. These results based on lesion experiments permit us to infer than under normal cinditions the development of generalized seizures induced by threshold pentylenetetrazol injection is highly dependent upon the neuronal interactions between nonspecific structures at different levels of the central nervous system. The possible nature of these neuronal interactions in the intact animals is discussed.

Animals↗
PubMed1976

Improvement of intractable idiopathic epilepsy with chlormadinone acetate. A case report.

A 10-year-old boy with idiopathic epilepsy refractory to treatment from age 4 and with clinical signs of hyperandrogenism was treated with chlormadinone acetate (24 mg/day) during two alternate periods of 3 months. The administration of chlormadinone was associated with a marked clinical and electroencephalographic improvement as well as a concomitant decrease in the levels of plasma testosterone and delta4 androstenedione. No changes in plasma gonadotropins were observed. Placebo had no effect neither in seizures nor in the concentration of hormones in the plasma. Since chlormadinone acetate is not a very potent gonadotropin inhibitor in males, it is suggested that the clinical and electroencephalographic improvement associated with the use of this compound, might be the consequence of a decrease in the plasma levels of androgens, mainly testosterone.

Androstenedione↗
PubMed1976

[Identification and lesion of prelemniscal radiation in the surgical treatment of tremor].

In a group of 40 patients operated on for the relief of tremor using stereotaxic techniques, the radiological location and electrophysiological characteristics of the optimum target were studied. The optimum target was defined as the place where the minimal lesion produced by the insertion of a 1.5 mm diameter electrode produced immediate cessation of tremor in the contralateral extremities. It was found that the optimum target is located in the subthalamus. Within this area electrical stimulation did not elicit sensory of pyramidal responses, but increased the amplitude of tremor. The study of somatic evoked potentials produced by stimulation of contralateral median nerve confirmed that the area does not correspond to a specific sensory system (medial lemniscus). By recording multiple unit activity a spontaneous 5 cycle per second rhythmic pattern, similar to that described for the VL thalamic nucleus, was occasionally seen. Finally, through an IBM 1130 computer the radiological location of those electrodes in the target area was approximated to a line, representing a vector whose orientation in space could be compared with that of different anatomical structures, and corresponded to the prelemniscal radiation. We concluded that the target area herein described is part of a reticulothalamic system that conveys tremogrogenic impulses to the pyramidal system and from here to the periphery.

Computers↗
PubMed1976

Alumina cream-induced focal motor epilepsy in cats. Part 3. Ultrastructure of the epileptogenic focus.

In this study the ultrastructure of motor cortex adjacent to alumina cream (AC) deposits was studied during the latent, convulsive and remission stages of an experimental model of epilepsy in cats. Findings were compared with those observed in sham-operated animals. Where AC was injected, amorphous material surrounded by macrophages containing phagocytic vacuoles was observed. At the edge of these areas, neither fibrous capsule, nor other inflammatory elements were seen. Changes in size and number of fibrous astrocytic processes and morphological signs of progressive degeneration of neuronal elements at the perilesional cortex were found through the latent, convulsive and remission stages. These findings support the idea that presence of clinical and EEG seizures in AC lesioned animals is independent of scar formation and other inflammatory elements. On the other hand, the significance of increased astrocytic processes and progressive degeneration signs of the perilesional cortex in the physiopathogenesis of convulsive activity requires further investigation. (Arch. Invest. Méd. (Méx) 7:157, 1976).

Aluminum↗
PubMed1975

Somatic evoked response components and recovery functions in subjects with mu and alpha rhythms.

Subjects with prominent rolandic mu and alpha rhythms showed similar late somatic evoked response (SER) components but different SER recovery functions. A late P5x component was present when SER were superimposed on mu and alpha rhythms spontaneously recorded from the rolandic region of inattentive individuals. Since P5x was not present in other inattentive subjects unless SER were superimposed on a rhythmic rolandic activity evoked by an attentive situation, it seems reasonable to assume that the P5x component is partially due to spontaneous or evoked rolandic EEG rhythmicity. In addition, single propioceptive stimuli produced blocking of mu rhythm and a flat recovery function of the P5a component. In contrast, similar stimuli produced an enhancement of alpha rhythm and a periodic amplitude modulation curve of the P5a component. These results suggest that the P5a component is mediated by the same neurophysiological mechanisms which block or modulate the spontaneous rolandic EEG rhythms.

Adolescent↗
PubMed1975

Differential effect of thalamic and subthalamic lesions on early and late components of the somatic evoked potentials in man.

The effect of thalamic (Vo), subthalamic (Raprl) and combined (Vo-Raprl) unilateral lesions on early and late components of the somatic evoked potentials (SEPs) was investigated in a group of 16 cases operated on for the treatment of contralateral dyskinetic movements. In these cases, SEPs were independently produced by stimulation of the left and right median nerves and recorded at the corresponding somatosensory scalp regions. In addition, EEG frequencies and reaction time (RT) were independently and bilaterally determined. These tests were performed before and after operation and changes in SEP, EEG and RT were quantitatively evaluated in relation to both ipsilateral preoperative and contralateral postoperative controls. 1. All cases with either thalamic or combined lesions involving Vo nucleus showed an ipsilateral reduction in amplitude of late SEP components and EEG frequency and a contralateral increase RT. A peculiar form of "inattention" to the contralateral hand was also found. Quantitative evaluation of the total group showed significant amplitude reduction in late SEP components in relation to both ipsilateral preoperative and contralateral postoperative controls. Changes in EEG and RT were only significant in relation to their preoperative ipsilateral controls. 2. Two cases with subthalamic lesions and quick postoperative recovery showed no apparent change in SEP, EEG and RT. Three cases with similar lesions and slow postoperative recovery showed bilateral decrease in amplitude of late SEP components, EEG frequency and increase in RT. Clinical inattention to contralateral hand was also found in all these cases. Quantitative evaluation of the total group showed no significant changes in these parameters in relation to preoperative controls. 3. None of these lesions produced changes in early SEP components or somatosensory deficits at the contralateral hand.

Attention↗
PubMed1975

Differential effect of task relevance on early and late components of cortical and subcortical somatic evoked potentials in man.

The effect of "task relevance" on early and late components of cortical and subcortical somatic evoked potentials (SEPs) was studied in a group of Parkinsonian patients operated on under local anesthesia for treatment of prominent unilateral tremor. 1. SEPs produced by median nerve stimulation were found at contralateral cortical (ss), thalamic (vcpci, vcai), lemniscal (Lm), postilemniscal (PoLm), prelemniscal (Raprl) and reticular (Ttc) regions. No SEPs were found in other contiguous thalamic (M,Pf, ce) and subthalamic (Q) regions. 2. Subcortical early SEP components consisted of two monophasic positive potentials distributed within a circumscribed thalamo-lemniscal region where electrical stimulation elicited consistent sensory responses circumscribed to contralateral hand and face. In contrast, subcortical late SEP components consisted of monophasic or polyphasic, positive or negative potentials distributed in a widespread, thalamic, lemniscal, prelemniscal and reticular region where elecrical stimulation elecited sensory or motor responses of various types. Subcortical early and late SEP components appeared together in lemniscal, thalamic and cortical regions but they wers separated at postlemniscal (only early) and prelemniscal and reticular ones (only late). 3. Significant amplitude changes in cortical and subcortical late SEP componets were found concomitant to variations in "task relevance": they decreased when patients shifted from novelty to habituation, they increased when patients shifted from habituation to attention and they decreased when patients shifted from attention to distraction. In contrast, no significant ampiltude changes in cortical and subcortical early components were found when patients shifted through these various "task relevance" conditions.

Adult↗