Vincent Bloch

Analyse des effets d'un apprentissage et de son niveau d'acquisition sur le sommeil paradoxal consécutif

Abstract EEG and EMG recordings were taken at the same time each day over a 3-h period, and the duration of paradoxical and slow wave sleep noted for each day. After several days, experimental groups underwent two-way shuttlebox avoidance conditioning prior to the daily recording session. Trials were either crowded (70 trials in a single session) or distributed (one 15-trial session each day); in the latter condition, the learning sessions were continued for each rat until asymptote performance was reached. Control groups were tested for the effects of shock and tone stimulation. The control rats showed no significant change in PS duration at any time during the experiment. In the experimental groups there was, by contrast, a significant increase in PS and, in the distributed condition, this increase was related to the degree of learning achieved, but on the fourth day, when performance reached the asymptote PS duration returned to the reference level. The increased duration of PS in the experimental groups was due to an increase in the number of PS phases, the average duration of each phase not showing any change. It should be added that the increases were found only in the first half-hour of sleep; the effect would thus appear to be immediate and short-lasting.

Duration of paradoxical sleep necessary for the acquisition of conditioned avoidance in the rat.

Abstract In a previous work we have shown, in the rat, that an increase of the duration of paradoxical sleep (PS) occurs after each conditioning session of different tasks, without any alteration of the duration of slow wave sleep. Furthermore, our findings suggested that the increase phenomenon shows a short latency and a short duration. This experiment was designed for the purpose of studying the useful duration of the increase of paradoxical sleep following an avoidance conditioning in the rat. we have observed that a period of 90 min free sleep immediately consecutive to each conditioning session (15 trials) is sufficient for good retention to occur. Whereas, a period of 30 min free sleep during which we do not observe PS increase, does not allow conditioning to be established; 60 min of free sleep, with PS increase, only slightly disturbs the learning curve. Therefore, the time period, immediately consecutive to conditioning, during which the integrity of sleep is necessary, is, in our experimental conditions, between 60 and 90 min. Throughout the course of this period, the duration of PS is augmented during the initial days of conditioning.

Improvement of learning by mesencephalic reticular stimulation during postlearning paradoxical sleep

Evidences have been given which suggest that a newly formed memory trace is processed during paradoxical sleep (PS) following learning. The present experiments were aimed at testing the hypothesis that during postlearning PS the new memory trace is in a similar state as immediately after acquisition. For this purpose, a mild electrical stimulation of the mesencephalic reticular formation (MRF)--known to enhance retention performance when delivered just after learning--was administered during postlearning PS phases. Wistar rats were trained to run in a six-unit spatial discrimination maze for food reward. After each daily trial, extradural cortical electrodes (ECoG) activity was monitored polygraphically for 4 h. Half of the animals received nonawakening MRF stimulations during the first six phases of PS. Control rats received no stimulation. The learning results showed a marked improvement in performance, in terms of error number reduction, in the stimulated group. Results of a second experiment confirmed the facilitative effect of MRF stimulations given during postlearning PS. Moreover, they emphasized the specific role of PS, by showing that the same stimulations were ineffective when delivered, at the same time intervals after training, during six periods of waking or six periods of slow-wave sleep. These results lend support to the idea of a reactivation of the new memory trace during PS. They suggest that dynamic processes, similar to those immediately following acquisition or exposure to a reactivating treatment (i.e., a reminder), take place during postlearning PS.

On the Centennial of the Discovery of Electrodermal Activity

First, I wish to thank the organizers, and I feel honoured to have been asked to introduce this meeting. I do not deserve this honour because I was somewhat a turncoat to your field when I left electodermal research more than twenty five years ago. But I have been a member of your club for a very long time and I still feel at home in the electrodermal family.

Égalisation des conditions et formes du racisme à La Havane pendant la période spéciale. Une lecture du roman Las Bestias, de Ronaldo Menéndez

Les Cubains percoivent en general les expressions, prejuges, fantasmes et comportements racistes dont ils sont impregnes comme un phenomene culturel, qui participe d’une relation affective avec l’Autre, ancree dans les temps longs de l’histoire de l’ile. Ce « racisme culturel » est pourtant pris dans la dynamique d’egalisation des conditions qui decoule depuis le debut de la « periode speciale » de la precarisation du quotidien, de la criminalisation des comportements et de l’effondrement des reperes moraux. L’objet de cet article est de proposer une phenomenologie de ce « racisme culturel », d’abord a partir d’une description ethnographique, et ensuite a travers une lecture du roman Las Bestias de Ronaldo Menendez.