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Biomedical subjects

A Rougeul

Publications and source records attributed to A Rougeul.

At least 37 records · Page 2Linked to original sources
PubMed1982

Ventral mesencephalic tegmentum (VMT) controls electrocortical beta rhythms and associated attentive behaviour in the cat.

When a cat is immobile, very alert and displaying behaviour suggesting focused attention toward a target in its environment, beta rhythms (ca. 40 Hz) develop in the fronto-parietal cortical areas. After bilateral electrolytic lesions of the ventral mesencephalic tegmentum (VMT), these beta rhythms are suppressed (while other cortical activities, with other behavioural correlates, persist), and at the same time, attentive immobility is no longer observed: the same experimental situation as in the control now elicits locomotor hyperactivity. Arguments are produced, favouring the hypothesis that both behavioural immobility and the accompanying thalamocortical beta rhythms are controlled through one of the dopaminergic system that originate from the VMT and are distinct from the nigrostriatal one.

Animals↗
PubMed1982

Somatosensory rhythms in the awake cat: a single unit exploration of their thalamic concomitant in nucleus ventralis posterior and vicinity.

A microelectrode study was performed in n. ventralis posterior (VP) of the fully alert cat, to study the correlation between thalamic unit activity and the cortical synchronized 14 c/sec rhythms that develop in the somatic area I for forepaw and wrist projections, when the animal is in a state of "quiet waking". (i) Only a small proportion of VP cells underwent changes during the studied cortical rhythms. (ii) None of these cells were typical thalamo-cortical relay cells carrying tactile messages to the cortex. (iii) Cells altering their discharge were of two types, rhythmic (R) cells, discharging at the frequency of the cortical rhythms, and tonic (T) cells, displaying an overall, sustained change during the whole sequence of cortical 14 c/sec. (iv) Among R cells, some were long axon thalamo-cortical cells and others, likely to be interneurones. (v) Some T cells increased their firing rate during rhythmic trains, others came into silence during the same period. (vi) The thalamic circuitry responsible for this particular set of "quiet waking rhythms" is discussed.

Action Potentials↗
PubMed1981

Fast fronto-parietal rhythms during combined focused attentive behaviour and immobility in cat: cortical and thalamic localizations.

In the cat, fronto-parietal mu rhythms belonging to the 'high frequency range' (35-45 c/sec) develop as the animal becomes immobile in an attitude of focused attention. Two cortical foci were identified, one anterior in the precruciate area, the other posterior in the periansate cortex (posterior parietal area). A thalamic focus, in an area belonging to the medial portion of the posterior thalamic group, appears to be a pacemaker for the posterior cortical focus alone.

Animals↗
PubMed1980

[Parietal electrocortical rhythms in the cat: their relation to a behavior of focused attention and possible mesencephalic control through a dopaminergic pathway].

In the Cat, the development of an electrocortical rhythm at 40 Hz (fast "mu" rhythm) is observed in the parietal cortex whenever the subject immobilizes itself in an attitude of focused attention (e.g. when watching a mouse). This rhythm, as well as the accompanying behaviour, seems to be under the control of a dopaminergic mechanism originating from the ventral tegmental mesencephalic area (cellular dopaminergic group A 10).

Animals↗
PubMed1980

Comparative anxiolytic and hypnotic effects of 3 benzodiazepines on baboons.

The ECoG and behavioural effects of administering 3 benzodiazepines (diazepam, nitrazepam, lorazepam) were tested in baboons restrained in a chair, with arms fastened (a situation which is considered 'anxiogenic'). Considering our previous data with ECoG recording of focal rhythms from area somatic I, the 3 drugs were revealed as 'anxiolytic'. Differences were noticed with respect to their hypnotic effects: no sleep was elicited under diazepam; a considerable amount of slow sleep was observed with lorazepam; nitrazepam produced a succession of short waking/sleep cycles.

Animals↗
PubMed1979

Modification of spontaneous ECoG and behavior in cat by monoamine precursors.

The effects of increasing the brain monoamine content on the three types of localized rhythms identified in somatic area I ("mu-type rhythms") were studied in freely moving cats. Increases in brain monoamines (catecholamines and serotonin) were produced by injecting L-Dopa and 5-HTP, L-tyrosine, L-tryptophan and tryptamine were also tested. It is concluded that the two subsets of rhythms, one accompanying high levels of alertness and vigilance and the other appearing during quiet wakefulness, are related to the catecholaminergic systems, while those characterizing drowsiness seem to be controlled by a serotoninergic system. The latter, however, is distinct from that controlling slow sleep.

5-Hydroxytryptophan↗
PubMed1979

Effects of two neuroleptic drugs on focal somatoparietal rhythms in free awake cats.

In freely moving cats, systemic administration of Chlorpromazine (CPZ) and Haloperidol (HP), two neuroleptics which presumably block catecholamine receptors, leads to a suppression of the waking mu-type rhythms. There is a clear difference, however, in that CPZ leads to slow wave sleep while HP only induces sustained drowsiness. The difference in their action is tentatively explained by their differential effect on an enzyme that is not involved in the metabolism of biogenic amines, tryptophan pyrrolase. We suggest that it is through this pathway that CPZ might increase and HP might decrease brain tryptophan and thereby lead to opposite changes in brain 5-HT content.

Animals↗
PubMed1979

Fast somato-parietal rhythms during combined focal attention and immobility in baboon and squirrel monkey.

In the monkey (baboon or squirrel monkey) displaying a high level of vigilance, a particular type of spontaneous ECoG rhythm develops when the subject is motionless and fixes its attention on a visual target in its surroundings. This activity, whose frequency averages around 18 c/sec, is distributed over two restricted cortical foci, one over the SI hand area (Brodmann's fields 1 and 2) and the other over the posterior parietal cortex (area 5). These rhythms are blocked by the least body movement (but not by eye movements). In view of their location and reactivity, the rolandic portion of these rhythms belongs to the 'mu' type as described in man. The suggestion is made that this synchronized activity favours the maintenance of immobility as well as the fixation of attention on a non-somaesthetic target by temporarily blocking both somaesthetic (in area SI) and somatopraxic integration (in area 5).

Action Potentials↗
PubMed1978

Restraint in primate chair may cause unusual behaviour in baboons; electrocorticographic correlates and corrective effects of diazepam.

Whereas primates restrained in a chair may usually be considered 'normal', the behaviour of baboons in this position was considerably altered: their eyes were closed and they only slightly reacted to the approach of the experimenter (opening of the eyes), in contrast with their active behaviour when left free to move about in their cage. When the ECoG was recorded from certain cortical areas (particularly somatic area I), an unusual pattern developed during the restrained state: 'drowsiness rhythms', which typically appear in this area during transition from wakefulness to sleep, developed in long sustained sequences. Administration of diazepam, an anxiolytic drug, caused both the behaviour and the ECoG of the restrained animal to return to normal (i.e., attentive behaviour and ECoG characteristic of the true waking state). The prolonged drowsy-like ECoG and behaviour may therefore underline a reaction to the 'stress' conditions brought on by restraint.

Animals↗
PubMed1977

Selective modification of spontaneous ECoG rhythms of the cat somesthetic cortex by psychoactive drugs: behavioral correlates.

Three psychoactive drugs with known central effects were administered to the freely moving cat in order to study their action on spontaneous rhythmic activities recorded from the primary somesthetic cortex, which are analogous to the rolandic mu rhyhm in man. The ECoG patterns obtained are qualitatively identical to those of the normal subject, but their temporal organization is profoundly disturbed by the action of the drugs. The normal ECoG consists of three rhythmic systems with distinct frequencies and displays a considerable time variability. In contrast, psychoactive drugs induce a stabilized pattern with only one type (or at most two types) of rhythm prevailing for one or several hours, which never occurs under normal conditions. These ECoG rhythms underlie various behavioral states. Under d-amphetamine, correspondence remains excellent between behavior and ECoG; under Ditran, complete dissociation occurs; finally, LSD represents a borderline case in which ECoG and behavior are partially correlated and partially dissociated.

Animals↗