Biomedical subjects

M F Montaron

Publications and source records attributed to M F Montaron.

26 records · Page 2Linked to original sources

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.

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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.

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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.

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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.

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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.

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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↗

PubMedDate not supplied

[Relationship between attention and mu rhythms in the cat and the monkey (author's transl)].

Recording from the cat and monkey parietal cortex reveals the existence of three categories of spontaneous rhythmic activities, with different frequencies, that have the same reactivity and localization as the mu rhythm in man. Each of these rhythms corresponds to a different level of attention and can be preferentially determined through placing the subject in a given situation. The fastest rhythms are observed when the subject displays an attentive behaviour toward a significant target, while those of intermediate frequency are seen during a period of expectancy (like watching a mouse-hole). The slowest rhythms occur when the subject does not show interest to its surrounding. A hypothesis is proposed that mu rhythms are involved in the neurophysiological mechanisms of attention.

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PubMedDate not supplied

PSA-NCAM: an important regulator of hippocampal plasticity.

The Neural Cell Adhesion Molecule (NCAM) serves as a temporally and spatially regulated modulator of a variety of cell-cell interactions. This review summarizes recent results of studies aimed at understanding its regulation of expression and biological function, thereby focussing on its polysialylated isoforms (PSA-NCAM). The detailed analysis of the expression of PSA and NCAM in the hippocampal mossy fiber system and the morphological consequences of PSA-NCAM deficiency in mice support the notion that the levels of expression of NCAM are important not only for the regulation and maintenance of structural changes, such as migration, axonal growth and fasciculation, but also for activity-induced plasticity. There is evidence that PSA-NCAM can specifically contribute to a presynaptic form of plasticity, namely long-term potentiation at hippocampal mossy fiber synapses. This is consistent with previous observations that NCAM-deficient mice show deficits in spatial learning and exploratory behavior. Furthermore, our data points to an important role of the hypothalamic-pituitary-adrenal axis, which is the principle adaptive response of the organism to environmental challenges, in the control of PSA-NCAM expression in the hippocampal formation. In particular, we evidence an inhibitory influence of corticosterone on PSA-NCAM expression.

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