Biomedical subjects

A Rougeul

Publications and source records attributed to A Rougeul.

At least 19 recordsLinked to original sources

PubMed1994

Relationship between posterior thalamic nucleus unit activity and parietal cortical rhythms (beta) in the waking cat.

Cat behavioural states of attentive fixation on a target are associated with episodes of electrocortical rhythms at 40 Hz ("beta rhythms") in the parietal cortex. Previous field potential studies indicate that the nucleus posterior pars medialis of the thalamus displays this particular rhythmic activity. We investigated single units of the nucleus posterior pars medialis and its surrounding nuclei to assess their participation in the cortical beta rhythms. Only a small proportion of thalamic cells underwent changes in their firing pattern during beta episodes. "Beta-related cells" were localized in the nucleus posterior pars medialis or its immediate vicinity; no such beta-related cells were found in other regions of the lateral thalamus. Some beta-related cells showed a one-spike to one-wave relationship ("homorhythmicity"), while others displayed a prolonged decrease or a suppression of their firing throughout each beta episode ("pause cells"). For comparison, neurons in the same thalamic area were also recorded during sleep episodes with slow waves and spindles: there was no correlation between spindles and cell firing. Thus, the nucleus posterior pars medialis thalamic nucleus contains cells whose firing is correlated with the beta rhythms. No such correlation was found with sleep spindles.

Animals↗

PubMed1993

Effects of locus coeruleus lesions on vigilance and attentive behaviour in cat.

Previous data have suggested that in the cat, expectancy behaviour (waiting for a target to appear) and associated electrocortical, focal, synchronized activity ('mu' rhythms) are modulated by a noradrenergic system possibly originating from the locus coeruleus (LC). To test the latter hypothesis, we have examined the behavioural and ECoG changes induced after bilateral LC lesions. Our results demonstrated that destruction of the anterior 3/4th of the LC (A6 noradrenergic cell group) resulted in a considerable increase of mu rhythms and expectancy behaviour, without episodes of drowsiness that normally occur. Destruction of the posterior fourth of LC (A4 noradrenergic group) only increased the duration of slow sleep. Extending the A6 lesion to include the dorsal ascending noradrenergic bundle also increased the expectancy behaviour and mu rhythms. Finally, when the nucleus subcoeruleus was also involved, the duration of slow sleep and the frequency of paradoxical sleep episodes increased. These findings indicate that the LC exerts an inhibitory effect on structures involved in the induction and persistence of expectancy behaviour with accompanying mu rhythms.

Animals↗

PubMed1993

Alpha rhythm in the cat thalamus.

In cats, electrocortical rhythms at about 10 Hz displaying common characteristics with the human alpha rhythm [1] were recorded from the part of the visual cortex that includes the anterior half of areas 17 (on the cortical convexity), of area 18 and of their common limit, representing the projection of the lower contralateral visual quadrant and that of the lower vertical meridian. It is shown here that activities highly correlated with these rhythms and at the same frequency, were recorded from the anterior half of the laminar dorsal lateral geniculate body (mediodorsal part of layer A), and also from a limited area medial to this nucleus. The cat thalamocortical alpha system thus appears to concern only the projection of the lower quadrants, probably excluding the area centralis itself.

Alpha Rhythm↗

PubMed1992

Effects of mediodorsalis thalamic nucleus lesions on vigilance and attentive behaviour in cats.

In this study performed on 10 cats we analysed the effects of limited lesions of nucleus medialis dorsalis of the thalamus (MD) on behaviour and on some specific electrocorticographic (ECoG) patterns, known from previous works to accompany various states of waking attentiveness. The animals were tested during 90 min in three distinct behavioural situations; a neutral one (NS) where they simply explored their environment and then usually went to sleep; a second one (FA) where they could watch a mouse (but not catch it), which favoured 'focussed' attentiveness accompanied by the development of rhythmic ECoG activities in the anterior frontoparietal cortex ('beta rhythms' at 40 Hz); a third one (EX) with a hidden mouse whose appearance the cat was waiting for ('expectancy') which rather than favouring the development of beta rhythms elicited the appearance of another rhythmic activity dominating in somatic area SI, 'mu rhythms' at 14 Hz. The duration of each waking behaviour and its ECoG concomitant as well as that of slow wave and of paradoxical sleep were compared in each cat before and after lesion. Our results showed that MD lesions situated in the posterior part of the nucleus tended to increase the time occupied by focussed attentive behaviour and the accompanying beta rhythms. On the other hand, anteriorly located MD lesions elicited a concomitant reduction of both manifestations, behavioural and electrocortical. No such contrasting effects could be systematically noticed for the durations of expectancy, of slow sleep and of paradoxical sleep. These findings were discussed considering previous data showing that at least two systems project upon MD, that play distinct--in a way even antagonistic--roles in focussed attention upon a target. Both originate from the ventral tegmental mesencephalic area; one reaches MD through the ventral striatum (nucleus accumbens), the other one through the amygdala. The MD nucleus thus receiving contrasting information may participate in a final adjustment of the attentive state of the animal to its environment.

Animals↗

PubMed1992

A 10 Hz "alpha-like" rhythm in the visual cortex of the waking cat.

Rhythms at about 10 Hz were recorded from the primary visual cortex of the cat (anterior part of area 18), with characteristics close to those of the alpha rhythm in man: frequency band (7-14 Hz), localization and reactivity to visual stimulation. Coherence analysis of this activity with the "mu" rhythms on the somatosensory cortex showed that although both types develop in the same overall behavioural situations (quiet waking and/or expectancy of an event to occur), they are independent.

Alpha Rhythm↗

PubMed1992

Nucleus reticularis thalami participates in sleep spindles, not in beta rhythms concomitant with attention in cat.

In the awake cat, characteristic electrocortical synchronized oscillations (beta rhythms) can develop on the parietal cortex in specific behavioural situations such as during attentive fixation of a target. These activities differ from other synchronized rhythms which accompany slow sleep ("spindles") and are more widespread. It is shown here through single unit recording from the thalamic nucleus reticularis (RET), that the latter structure participates in spindles (as already postulated by other authors), but not in the beta rhythms which seem to depend on a more restricted thalamic focus in the posterior thalamic nucleus. These data thus support the idea that RET plays a role in slow-wave sleep but not in the cognitive operations involved in focussing attention.

Animals↗

PubMed1991

Noradrenaline-like terminals in the cat nucleus ventralis posterior of the thalamus.

Noradrenaline-like immunoreactivity in the cat nucleus ventralis posterior of the thalamus was investigated using an indirect immunocytochemical technique. Specific antinoradrenaline antibodies, raised in rabbits, were used. It was first verified that these antibodies recognize noradrenaline cells bodies of the locus coeruleus and their ascending axons in the ascending noradrenergic tract. In the nucleus ventralis posterior itself, noradrenaline-like fibers were observed. They were either randomly distributed or grouped around nonlabeled cell bodies. These neurons were generally oblong and measured 60-80 microns. With electron microscopy, preliminary results showed immunoreactive fibers in close apposition to unlabeled cell bodies or dendrites. The precise nature of these profiles was sometimes difficult to ascertain, since experiments were done in presence of detergent. In some cases symmetric synapses might be observed between immunoreactive axon terminals and unlabeled dendrites. The specificity of the reaction is discussed in the light of several control experiments.

Animals↗

PubMed1990

Action of tianeptine on focalization of attention in cat.

Tianeptine, an antidepressant substance devoid of sedative action, was investigated for its effects on focalization of attention in cats, using combined behavioural and electrocorticographic (ECoG) observations. The ECoG index was the presence of 40 Hz frontoparietal rhythmic cortical activities, developing while the animal displayed a behaviour suggesting focused attention. Cats were observed in two conditions: a "neutral" one, with no specific target, and another one, "of focused attention" where a live mouse placed in a transparent box was present in the recording room, each test lasting for 90 min. After treatment the animals displayed increased attention even in the neutral situation, where the cat, instead of sleeping like during control sessions, payed sustained attention to its environment. Conversely, at corresponding doses, amitriptyline, another antidepressant drug chosen as a reference, induced uninterrupted slow sleep even in the situation of focused attention.

Amitriptyline↗

PubMed1989

Effect of DSP4, a neurotoxic agent, on attentive behaviour and related electrocortical activity in cat.

Six behaving cats were administered N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4) (i.p. 10 mg/kg), a neurotoxic agent known to destroy noradrenergic endings in the CNS. They were placed, both before (control) and after treatment in 3 different situations, each time for 90 min: (1) a 'neutral' one (N) with no significant stimuli; (2) another one eliciting focused attention (F); (3) a third one, creating a situation of 'expectancy of an event to occur' (E), with the animal usually displaying a posture of quiet waking. Simultaneously, the electrocorticogram (ECoG) was recorded from the sensorimotor and parietal cortex through implanted electrodes. We already knew and were able to confirm that the normal animals (i.e. before treatment) displayed distinct behavioural patterns depending on the situation and distinct accompanying parietofrontal ECoG activities, with a dominance of drowsiness and sleep during N, that of a 36-Hz 'beta' rhythms in condition F, and of 14-Hz 'mu' rhythms in condition E. It was shown that the prevailing attitude of the animals after treatment was now, in all 3 situations, that of 'quiet waking and/or expectancy-like watching', with a large if not exclusive dominance of only one ECoG pattern, namely mu. These changes were considered as due to a release of the mu system from a noradrenergic modulatory blockade, in accordance with some of our previous data. An immunohistochemical study with anti-tyrosine hydroxylase antibody was also performed; it confirmed that after DSP4 treatment there were substantial alterations in the immunoreactivity of locus coeruleus cells, the structure which is likely to be involved in this NAergic control of the mu rhythms and of its concomitant behaviour.

Animals↗

PubMed1989

[Regulation pathways of expectancy behavior in the cat: histologic study].

In the behaving cat, motion expectancy of an event to occur (for a prey to appear) is accompanied by the development of 14 Hz electrocortical mu rhythms in the hand subarea of cortical somatic area SI. Our first aim here was to identify subcortical sites projecting to this cortical mu focus, using localised retrograde HRP marking. The only site thus labelled was the thalamic zone well known to project to the cortical mu area, and to act as a generator for the mu rhythms (ventral posterior nucleus, VP); no other deep structure could be identified, that could have been considered as a putative zone for control of cortical mu. We then injected minute amounts of HRP into the thalamic mu zone; labelled neurones were located (apart from those expected in the relays of the somatic pathway) in locus coeruleus (bilaterally) and ipsilaterally in the thalamic nuclei anteroventralis and laterodorsalis. In brief then, it seems that the regulation of the VP-SI mu channel (that we could previously demonstrate), by other deep structures is exerted upon the thalamic side.

Animals↗

PubMed1988

[DSP 4, a neurotoxic agent that destroys noradrenergic endings, selectively increases "expectancy" in the cat].

Cats were treated with DSP 4, a neurotoxic agent known to destroy central noradrenergic endings. A significant increase was subsequently noticed in the amount of time spent by the treated animals in an attitude of "expectancy", i.e. of motionless waiting for an "event to occur". They even developed this attitude when no such real situation existed. Concomitantly, an increase was noticed in the power of the 14 Hz electrocortical rhythms recorded over the somatic sensory cortex. These patterns, designated as "mu" rhythms, had previously been shown to characterize this particular type of attentive state. The present data tends to confirm our previous hypothesis, that immobile expectancy and its accompanying electrocortical pattern are under a noradrenergic inhibitory control.

Animals↗

PubMed1987

Anatomical localization of cortical beta rhythms in cat.

Beta electrocorticographic rhythms (40 Hz) develop during motionless focused attention in two distinct cortical foci in cats. A cytoarchitectonic study was performed to determine the precise location of these foci. Electrode tips recording beta rhythms were found: (i) in motor areas 4 gamma and 6a beta, in a band extending from the postcruciate cortex to the walls of the presylvian sulcus, crossing the frontal pole (anterior beta focus); (ii) in the posterior parietal associative area 5a, along the divisions of the ansate sulcus, extending to the mesial aspect of the hemispheres (posterior beta focus). The two foci are separated by areas 3, 2 and 1, where beta rhythms were never recorded. The fact that both these areas, containing giant pyramidal cells, develop a specific type of activity during immobility may have a functional meaning: area 5 may be involved in the cat as it is in the monkey in the control of motor behaviour.

Animals↗

PubMed1987

[Unit activity of neurons of the posterior ventral nucleus of the thalamus for various waking stages in the normal cat].

Using the electrocortical activity in the sensorimotor cortex as an index, three distinct levels of motionless waking can be identified in the cat, all three different from active waking and from slow sleep (attentive waking, quiet waking and drowsiness). It has now been shown that spontaneous and evoked single unit activities in n. ventralis posterior of the thalamus undergo significant changes when passing from one level of waking into another one.

Animals↗

PubMed1986

Compulsive attentive behavior after lesion of the ventral striatum in the cat: a behavioral and electrophysiological study.

Bilateral lesions of the nucleus accumbens in cat elicited the following changes: preservation in tests requiring focused attention, with difficulty to shift to other targets; paucity of movements, animals displaying moderate hypokinesia and loss of reaction to changes in the environment. These symptoms were accompanied by a significant increase in the amount of beta rhythms, an activity that has been shown to be concomitant with the development of focused attentive behavior. The observed behavioral and electrocortical modifications are opposite those that have been previously obtained in the same species after lesions of the ventral tegmental area.

Animals↗

PubMed1986

[Cytoarchitectonic localization of foci of electrocortical activity accompanying focused attention in cats].

Beta electrocorticographic rhythms (30-45 Hz) develop during focused immobile attention within two distinct foci in cats. A multiple electrode exploration was performed, followed by post-mortem histological analysis, to determine the precise localization of these foci. Electrode tips recording beta rhythms in the waking attentive cat were located: in motor areas (Brodmann's areas 4 and 6), in a band extending from the postcruciate cortex to the walls of the presylvian sulcus, crossing the frontal pole (anterior beta focus); in the posterior parietal associative area 5a, along the divisions of the ansate sulcus (posterior beta focus). The two foci are separated by somatic areas 3, 2 and 1, where beta rhythms were never recorded. The location of the posterior focus may suggest that area 5 is, in the cat as it is in the monkey, involved in motor control.

Animals↗

PubMed1984

[Unit activity in the ventral tegmental area and the state of focused attention in the normal awake cat].

Our previous studies had indicated that electrocortical "beta" rhythms (37 Hz) that develop in the fronto-parietal area in waking, immobile and highly attentive cats, are under the control of a dopaminergic system originating from the ventral tegmental area (VTA). A single unit study has now shown that 9% of VTA cells displayed a sustained increased of their firing rate during each beta episode. These data indicate that VTA cells exert a "gate control" on the rhythmic thalamo-cortical beta system.

Animals↗

PubMed1983

Thalamic rhythms in cat during quiet wakefulness and immobility.

In this study we tried to get some more information on the cortical 'mu' rhythms in normal cat and their thalamic pacemaker. Mu (14 c/sec) activity develops when the animal is motionless, in a state of 'quiet waking.' It is distinct from other sensorimotor rhythms, with distinct cortical distributions, distinct frequencies and appearing under different behavioural and environmental conditions. The cortical mu focus was shown to be centred within a restricted part of area SI, in the forepaw and wrist projection field. The related thalamic focus was localized in a small zone of the VP nucleus that also corresponded to the hand and wrist projection area. A coherence study confirmed the close relationship between the two foci, thalamic and cortical. After unilateral electrolytic destruction of the thalamic area, a small mu activity persisted, on the ipsilateral cortex, originating from the opposite side. After bilateral lesion of the VP foci, no mu activity could ever be recorded on either side, while the other sensorimotor rhythms were left intact.

Animals↗

PubMed1983

[Localized frontoparietal beta rhythms and focused attention in animals].

In normal cats and monkeys, fronto-parietal beta rhythms (averages: 36 and 18 c/sec, respectively) were considered as a sign of focused attention, since they appeared during several different situations having in common that the subject's attention was drawn by a signal or an object of the environment. These regular rhythmic activities, often with a high amplitude, are localized within two small cortical foci. At least one set of beta rhythms corresponds to the end station of a thalamocortical system originating in the posterior group (POm), and are controlled by a dopaminergic system the somas of which are situated in the ventral mesencephalic tegmentum (area A10). Eight percent of the VMT cells, studied with micropipettes in normal awake cats, suddenly increased their spontaneous activity 1 sec before the beginning of the rhythmic volleys. Considering the analogy between these rhythms and the human frontal beta rhythms, it is suggested that these data may contribute to the study of attention in man, whether in a healthy state or suffering from mental disease.

Animals↗