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Biomedical subjects

C Thinus-Blanc

Publications and source records attributed to C Thinus-Blanc.

At least 19 recordsLinked to original sources
PubMed1998

Spatial firing of hippocampal place cells in blind rats.

The rat hippocampus contains cells that are characterized by location-specific firing. Previous work has shown that the angular position of hippocampal place cell firing fields is accurately controlled by the position of visual cues, suggesting that vision plays a important role in triggering place cell activity. However, a role for other types of information has also been suggested because place cell activity can be recorded while animals are moving in the darkness. In this study, we asked whether place fields can get established in rats that have never seen their environment. We studied place cell activity in early blind rats and found that these rats had place cells very similar to those recorded from sighted rats. This result suggests that early vision is not necessary for normal firing of hippocampal place cells. Dynamic, motion-related information in conjunction with stimulus recognition seems to be sufficient.

Animals↗
PubMed1997

Representation of space in blind persons: vision as a spatial sense?

Some researchers of studies of the incidence of early visual experience on spatial abilities have demonstrated profound spatial deficits in early blind participants, whereas others have not found evidence of deleterious effects of early visual deprivation. The aims of this article are to (a) consider the theoretical background of these studies, (b) take stock of the divergent data, and (c) propose new means of investigation. The authors examine the reasons why vision plays a critical role in spatial cognition. They review the literature data. They also review the factors that could account for the discrepant data and the effects of lack of early visual experience on brain functioning. They propose that the study of strategies is a valuable option to obtain insight into early blind persons' spatial impairment.

Blindness↗
PubMed1997

Early-blind subjects' spatial representation of manipulatory space: exploratory strategies and reaction to change.

The present study was aimed at analysing the effects of a lack of visual experience in human subjects on the detection and identification of a spatial change brought about to a configuration of objects displayed in manipulatory space. Exploratory patterns and performance levels were recorded. Learning effects were observed in different types of change and condition of presentation only in the early-blind and blindfolded sighted groups, but not in the late-blind group. Early blindness affected both exploratory patterns and performance levels. In addition, significant correlations were found between performance level and the use of systematic patterns of exploration. These data are discussed in relation with the importance of early vision during the development of spatial cognition.

Adolescent↗
PubMed1996

Early visual experience affects memorization and spatial representation of proprioceptive targets.

Five subjects who had been blind from an early age and five age-matched blindfolded sighted subjects were engaged in a spatial memory task. Locations to be memorized were presented on a sagittal plane by passive positioning of the left index finger. A go signal for matching the target location with the right index finger was provided 0 or 8 s after left hand positioning. Constant errors in amplitude and direction of movement and pointing distribution observed after the longer delay differed across groups. Pointing variability was higher in the blindfolded sighted group. In addition, the main axis of pointing distributions obtained in the blindfolded sighted group were aligned with the target array for the 8 s but not the 0 s delay. By contrast, the main axis tended to be aligned with movement direction for blind subjects for both delays. These results suggest that memorizing a proprioceptively defined target may involve distinct spatial representations according to delay and to early visual experience.

Adult↗
PubMed1996

The differences shown by C57BL/6 and DBA/2 inbred mice in detecting spatial novelty are subserved by a different hippocampal and parietal cortex interplay.

Inbred C57BL/6 (C57) and DBA/2 (DBA) mice with hippocampus, posterior parietal cortex or sham lesions were placed in an open-field containing five objects and their reactivity to the displacement (spatial novelty) or the substitution (object novelty) of some of these objects was examined. C57 mice reacted to spatial novelty by exploring more the displaced than the non-displaced objects while DBA mice did not show any consistent reaction. In the highly reactive C57 strain, the peak of exploratory responses directed towards the displaced objects was completely abolished by hippocampal and posterior parietal cortex lesions. In the non-reactive DBA strain, hippocampal lesions induced an aspecific decreased interest towards the two categories of objects while posterior parietal cortex lesions did not produce any behavioral modification. The high reactivity of C57 mice to spatial change appears to be subserved by the conjunctive participation of the hippocampus and the posterior parietal cortex. Conversely, the deficit shown by DBA mice in that situation seems to be related to: (i) a poorly functional hippocampus; and (ii) the non-involvement of the posterior parietal cortes. The present data suggest that the participation of the posterior parietal cortes to the detection of spatial novelty may depend on the degree of functionality of the hippocampus.

Animals↗
PubMed1996

Effects of parietal cortex lesions on spatial problem solving in the rat.

The Maier 3-table task was used to examine spatial representations in rats with lesions of the parietal cortex. Some animals had anteriorly placed lesions, some posteriorly placed in cortical areas, sometimes regarded as 'parietal' in earlier studies. After 5 days of familiarization, animals were given 18 days of testing on the standard Maier task. Both parietal groups were initially impaired, but reached the same level of performance as controls by the end of the test period. Learning occurred both within and between sessions for the anterior group, but only between sessions for the posterior group. There was no major functional differentiation apparent on this task between the two 'parietal' areas. Rate of exploration increased in both parietal groups across test sessions as task performance improved. It is argued that the change in exploratory activity across sessions in parietal groups may reflect the adoption of a compensatory strategy which improved performance, but that improvement could also have been due to neural changes, as structures, such as the frontal cortex or hippocampus, assume some functions normally mediated by the parietal area.

Animals↗
PubMed1996

Early-blind subjects' spatial abilities in the locomotor space: exploratory strategies and reaction-to-change performance.

The present study was aimed at analysing the effect of the lack of visual experience in the human subject in detecting the rearrangement of objects after a free exploration in the locomotor space. Exploratory patterns and performance levels were recorded. Distance processing was affected by early blindness. The early-blind group's patterns of exploration differed significantly from those of the visually experienced groups. Significant correlations were found between the performance level and the use of systematic patterns of exploration but not with individual features. These data are discussed in the light of the importance of early vision on the development of spatial cognition.

Adolescent↗
PubMed1996

Effects of limitations on the use of some visual and kinaesthetic information in spatial mapping during exploration in the rat.

The purpose of this experiment was to study the effects of limiting visual and/or locomotor access to a part of the environment in the building up of a spatial representation of the whole space. During five sessions, rats were allowed to explore separately and successively the two halves (subspaces) of a circular open field containing four objects. During exploration of each half, continuous or discontinuous locomotor and/or visual access to the other half was provided by using opaque or transparent partitions, with or without doors. Once habituation was complete, the partition was removed for some subjects but remained for others. The locomotor and exploratory reactions to this removal were recorded. Whatever their locomotor experience (continuous or discontinuous), rats that had a discontinuous visual experience between the subspaces displayed a renewal of exploratory activity, whereas the rats that had received a continuous visual experience did not re-explore the objects. This result suggests that continuous visual access to the whole space is necessary for the construction of an overall representation. Furthermore, continuous locomotor activity does not seem to compensate for the discontinuity of visual information.

Animals↗
PubMed1995

Nicotinic and muscarinic receptors in the rat prefrontal cortex: differential roles in working memory, response selection and effortful processing.

The aim of the present study was to evaluate the effects of cholinergic receptor blockade in the rat prefrontal cortex on cognitive processes. The nicotinic antagonists neuronal bungarotoxin and dihydro-beta-erythroidine and the muscarinic antagonist scopolamine were injected into the prelimbic area of the prefrontal cortex. Their behavioural effects were assessed in a T-maze to test reference memory (visual discrimination task) and working memory in delayed matching (MTS) and non-matching to sample (NMTS) tasks. Neuronal bungarotoxin produced a significant decrease in working memory performance in the MTS task but not in the NMTS task. In contrast, scopolamine impaired working memory in both MTS and NMTS tasks. Reference memory was not altered by any of the cholinergic antagonists. These results demonstrate a differential role of nicotinic and muscarinic receptors in the rat prefrontal cortex. Nicotinic transmission appears to be important in delayed response tasks requiring effortful processing for response selection, while the muscarinic system is involved in general working memory processes.

Acetylcholine↗
PubMed1994

Place cells in the ventral hippocampus of rats.

Many cells recorded from the dorsal hippocampus of freely moving rats are intensely active only when the rat's head is in a particular part of its environment. For this reason, such units are called 'place cells'. We have investigated whether place cells are also found in the ventral hippocampus. Recordings were made from ventral hippocampal units while rats chased food pellets in a cylindrical arena. The rat's position was simultaneously recorded by tracking a light on the rat's head. Our data show the existence of cells in the ventral hippocampus whose positional firing patterns and electrophysiological properties are very similar to those of dorsal hippocampal place cells.

Action Potentials↗
PubMed1994

Working memory, response selection, and effortful processing in rats with medial prefrontal lesions.

This study examined the effects of lesions of the prelimbic area of the rat prefrontal cortex on acquisition and retention of nonmatching (NMTS) and matching-to-sample (MTS) tasks. Both tasks involved a reference and a working memory component, but only working memory was impaired by the lesions. A comparison of the 2 tasks revealed quantitatively similar deficits in postoperatively trained rats. In preoperatively trained rats, however, the deficits were more important in the MTS task than in the NMTS task. In addition, an effect of interference between successive trials was observed in the NMTS task but not in the MTS task. Perseverative tendencies were observed in the MTS task only. These results suggest that prefrontal lesions induce working memory deficits as a result of poor temporal encoding and increased susceptibility to interference and impair effortful processing, such as that engaged in response selection mechanisms.

Animals↗
PubMed1993

A rapid test of rodents' vision using a modified open field apparatus.

Rats' responses to visual change in the environment were recorded in open field arenas in which a part or all of the visual environment could be altered without changing nonvisual features. Rats responded to a change in the appearance of one quadrant of a field by selectively reexploring the changed quadrant, and to a change in the whole environment by generally increasing their locomotor activity. The latter effect was equally large whether the change was from a patterned to a blank environment, or vice-versa. The present paradigms provide a rapid means of testing animals' vision.

Animals↗
PubMed1992

Exploratory activity and response to a spatial change in rats with hippocampal or posterior parietal cortical lesions.

Rats with bilateral lesions of posterior parietal cortex (PPC: Krieg's Area 7) or dorsal hippocampus (HIP) were compared with controls for their response to environmental change. In the first experiment, following subjects' exploration of a relatively homogeneous open-field environment, a stimulus-rat was introduced at a particular location beneath the glass floor. All groups selectively explored the location of the stimulus-rat, but only the control and PPC groups displayed habituation. On removal of the stimulus-rat, only the control group selectively re-explored the place where the stimulus-rat had been. A second experiment, similar to the first, used additional prominent visual cues beneath the floor. When the cues were spatially separate from the location of the stimulus-rat (Dissociated object condition), the same results were obtained as in the first experiment. When the additional cues were positioned close to the stimulus-rat location (Associated object condition), habituation occurred in all groups including the hippocampal group, and again the removal of the stimulus-rat resulted in a selective re-exploration of its former location in the control group only. However, a selective preference for staying at the stimulus-rat's previous location was found in PPC animals as in controls. Hippocampal rats failed to investigate the location of the missing stimulus in all conditions. The results confirm the role played by the hippocampus in spatial memory and suggest that the posterior parietal cortex is involved in the cognitive-demanding aspects of spatial encoding, particularly in environments that are poorly visually differentiated.

Animals↗
PubMed1992

Visually guided locomotion, distractibility, and the missing-stimulus effect in hooded rats with unilateral or bilateral lesions of parietal cortex.

When hooded rats with bilateral lesions of Krieg's area 7 (parietal cortex) were trained to locomote toward visual targets in a runway, they ran less accurately than did controls, although unilaterals ran accurately. When flashing lights were presented unexpectedly during their run, bilateral parietals were less disrupted than were controls, but they failed to show total neglect. Unilateral paritals turned toward distracters on either side but turned preferentially toward distracters contralateral to the intact hemisphere, particularly when distracters occurred bilaterally and simultaneously. Effects due to the omission of expected distracters were similar in parietals and controls. Rat parietal cortex is not essential for the redirection of attention to stimuli notable for their unexpected presence or absence, but parietal cortex may resolve interhemispheric competition. The results suggest a homology between parietal cortex in rat and primate.

Animals↗
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↗