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C Thinus-Blanc

Publications and source records attributed to C Thinus-Blanc.

30 records · Page 2Linked to original sources
PubMed1991

The effects of reversible inactivations of the hippocampus on exploratory activity and spatial memory.

This study was aimed at testing the effects of a reversible inactivation of the ventral hippocampus on behavior in response to a change, following a period of habituation with a hippocampus that functions normally. A new dishabituation paradigm was used, which allowed the testing of visuospatial memory. A salient stimulus was placed under the glass floor of the apparatus during initial exploration and was removed during the test session. The time spent above the zone where the stimulus was initially located indicated the rats' reaction to the change. Unlike the control rats who reacted to the removal of the salient stimulus by reexploring its previous location, lidocaine-injected subjects did not display any similar searching behavior. Experiment 2 examined the hypothesis that landmarks located under the floor could help hippocampus-inactivated animals to accurately react to the change. Two objects were located either close to the stimulus or some distance away from it. Even when the objects were closely associated to the stimulus, the same failure to react to the removal of the stimulus was found in lidocaine-injected rats. However, these animals displayed a higher activity level measured by the time spent on a "neutral" zone. This behavioral pattern suggests a specific localization deficit. The method of reversible inactivation appears to be a promising approach to the study of the time course of memory process with short-term experimental paradigms such as those used in the present study.

Animals↗
PubMed1991

The effects of superior colliculus lesions in hamsters: feature detection versus spatial localization.

This study was aimed at further documenting the effects of collicular lesions in exploratory activity in the hamster. Following habituation to a set of four objects placed in an open field, collicular and sham-operated hamsters were confronted to a change in the initial situation in which one object was replaced by a new one in a familiar location or in a new location, or a familiar object was moved to a new location, or was left in the same location (control condition). Hamsters sustaining lesions of the superior colliculus and sham-operated hamsters were found to habituate at the same rate. The surgical treatment modified the reactions to the spatial change. Intact hamsters reacted selectively to the new object, whatever its location. In contrast, collicular animals did not react to the familiar object when it was in a new location. Nevertheless, they were able to detect the new object when it replaced a familiar object at the same location. However, when the new object was at a new location, there was only a tendency in collicular hamsters to react to this change. When no change was made in the initial situation, no change in exploratory activity was observed in either group. These results, together with others, suggest that the rodent's superior colliculus is not directly involved in object discrimination, but plays a crucial role in the attentional components of spatial behavior.

Animals↗
PubMed1990

The effects of superior colliculus lesions on reactions to novelty in the hamster.

The aim of this experiment was to examine reactions to novelty of hamsters with large bilateral collicular lesions in an open field containing large conspicuous objects. A video-actographic system was used to quantify the contacts with the objects, the speed of the displacements and the angular head movements. Due to different evolutions of the scores in each group, most of the differences were found at the end of the experiment. Collicular animals, unlike controls, make contacts with the objects but do not habituate, which suggests that these contacts are not investigatory but fortuitous. This possibility is supported by the fact that collicular animals display hyperactive locomotion with stereotyped patterns by the end of the experiment. It is proposed that the depth of lesions and the salience of the stimulus are two modulating factors of the reaction to novelty in collicular animals.

Animals↗
PubMed1981

Volume discrimination learning in golden hamsters: effects of the structure of complex rearing cages.

Golden hamsters (Mesocricetus auratus) were reared from birth to adulthood in a spatially diversified situation (EG); their performances were compared with those of other hamsters housed in standard laboratory cages (SG). The task was to discriminate between 2 cubic volumes of different sizes followed by various test situations designed to define the respective parts played by the 3 spatial dimensions during perception. The results show that surfaces of volumes were mainly taken into account by EG subjects whereas width, alone, was used by the SG animals.

Animals↗
PubMed1978

Volume discrimination in golden hamsters.

To 8 subjects (golden hamsters, Mesocricetus auratus), having learned to discriminate between two cubic volumes of very different size, test-situations were presented to determine if the three spatial dimensions were taken into account during learning. The results show that width is the most used dimension.

Animals↗
PubMedDate not supplied

The associative parietal cortex and spatial processing in rodents.

It is widely acknowledged that the hippocampal formation has a central function in rodents' spatial memory and navigation. However, recent work has shown that other structures participate in specific spatial processing. That is so for the associative parietal cortex (APC). Although this neocortical region is far less developed in rodents than in humans and non-human primates, APC damage in rodents induces deficits which affect both egocentrically and allocentrically organized spatial behaviours. On the basis of behavioural (following parietal lesions) and neuroanatomical data, we propose that the APC could be at the interface between the level of perception of the physical world (egocentrically organized) and that of representations or maps (allocentrically organized) of this world. Reciprocally, the APC could also be involved in the transformation, in the opposite direction, of computations made on the basis of representations into motor actions necessary for the efficient execution of oriented behaviours within the physical world.

Animals↗