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R Campan

Publications and source records attributed to R Campan.

6 recordsLinked to original sources
PubMed1997

Tactic components in orientation.

In the first half of this century, taxes were considered the best models for working out the rules of stimulus-response systems. The interest for tactic behaviours suddenly disappeared in the mid-1960s, out of reasons specified in the present review. However, results of several recent studies reviewed in the present article suggest that tactic behaviours constitute, from an ontogenetic as well as phylogenetic point of view, a first step towards more complex oriented behaviours that have received much attention in recent years. The aim of this chapter is to update the implications of tactic responses in complex oriented behaviours. We argue that taxes are basic in the process of acquiring most, if not all of these behaviours, and that they often constitute the first steps in the ontogeny of orientation. Taxes are determined by a flexible balance between genetic and epigenetic factors. Their main function is to assist the ecological adaptation of the animal to the constraints of its environment. Finally, we plead for a revival of the studies of taxes in the light of a theory on the development of behaviour, based upon self-organization of autonomous living systems.

Animals↗
PubMed1997

Visual localization within single geometric planes of a space habitat.

BACKGROUND: The present study investigated how human subjects capture and restore visual information within a line representation drawing the three-dimensional configuration of a space module. METHODS: Nine subjects were asked to perform a visual localization task within this geometric model. The task consisted of localizing a light point appearing during 3 s in 40 different spatial positions and for 8 tilt angles of the model in the following random order: 0 degree, 45 degrees, 180 degrees, 225 degrees, 90 degrees, 315 degrees, 135 degrees, and 270 degrees. RESULTS: Results showed symmetric variations of the point-localizing errors about 180 degrees of tilt angle (vertical orientation) and a decrease of the errors when the points occurred in the distal, then in the median and in the proximal planes (virtual depth). The performance also varied according to the virtual ceiling, floor, right, left and back planes. The results have been discussed using a three-dimensional space representation based on a conservative mode of spatial information up to 90 degrees of tilt (horizontal orientation), and on a transformation mode beyond 90 degrees of tilt. CONCLUSION: We conclude that the visual localization in single geometric planes is orientation-dependent.

Computer Graphics↗
PubMed1996

Dynamic MRI in the congenital agenesis of the neural pituitary stalk syndrome: the role of the vascular pituitary stalk in predicting residual anterior pituitary function.

OBJECTIVE: Magnetic resonance imaging (MRI) without contrast medium is unable to give detailed information on the hypothalamic-pituitary structures. MRI using gadopentetate dimeglumine (Gd-DTPA), and dynamic MRI, were performed in patients with hypopituitarism previously diagnosed as having anterior pituitary hypoplasia, ectopic posterior pituitary and unidentified pituitary stalk (1) to determine whether Gd-DTPA improves the delineation of hypothalamic-pituitary structures; (2) to verify whether, if so, such improvement can be correlated with residual pituitary function in patients subjected to long-term follow-up; and (3) to identify the hypothalamic-pituitary vascular network in such cases. PATIENTS: Eighteen patients (13 males, 5 females) aged 10-26.4 years with unidentified pituitary stalk at first MRI study were evaluated. Eight had isolated GH deficiency (IGHD), and 10 had multiple pituitary hormone defect (MPHD) with the progression to complete anterior pituitary deficits seen by the age of 15 years in 8 patients (1 had GH and FSH-LH deficiency and 1 had GH, TSH and FSH-LH deficiency). RESULTS: The MRI revealed a very thin pituitary stalk in 7 patients (38.8%), 6 with IGHD (75%) and 1 (10%) with MPHD (GH and FSH-LH deficiency), after Gd-DTPA administration. Reassessment of anterior pituitary function showed that the thyroid, adrenal and gonadal functions were intact in the 6 patients with IGHD and pituitary stalk identified by Gd-DTPA as well as in one IGHD patient with no evidence of pituitary stalk. In one 10-year-old with IGHD at the time of presentation (6 years) and no pituitary stalk seen after Gd-DTPA, subclinical hypothalamic hypothyroidism and suspected hypogonadotropic hypogonadism were documented. Partial ACTH deficiency was recorded in the patient with TSH and FSH-LH deficiency with no pituitary stalk. After Gd-DTPA, patients with absent pituitary stalk had a risk of developing MPHD 27 times greater than had those with an identified pituitary stalk (relative risk = 27, 95% confidence interval 1.9-368.4, Fisher's exact test P = 0.009). Dynamic MR images obtained every 4.6 s revealed rapid enhancement of hypothalamic-pituitary structures and allowed the determination of the times to initial enhancement of ectopic posterior pituitary and hypoplastic anterior pituitary which ranged between 9.2 and 18.4 s, and that of complete anterior pituitary (32.2-41.4 s). The time to maximum enhancement of anterior pituitary was significantly longer than in controls (35.5 +/- 3.8 s vs 25.2 +/- 1.6 s, P < 0.0001). CONCLUSIONS: MRI with Gd-DTPA proved more sensitive in identifying the vascular component of pituitary stalk and added new information about the partial preservation of hypothalamo-hypophyseal portal vessels. The vascular pituitary stalk is easily recognized after Gd-DTPA in most IGHD patients, but exceptionally in MPHD; this sheds light on the possible normal course of affected patients. The neural component of the pituitary stalk is lacking regardless of whether patients have IGHD or MPHD, indicating that the term congenital agenesis of the neural pituitary stalk is more appropriate than pituitary stalk interruption. The times to enhancement of ectopic posterior pituitary and residual anterior pituitary obtained by the fast-framing MRI technique disclose dynamic changes in regional blood supply which appear direct, arterial and mainly independent of the portal system.

Adolescent↗
PubMed1989

Astronaut behavior in an orbital flight situation: preliminary ethological observations.

Following the ethological approach, astronaut behavior is divided into "observable" motor acts which make possible its quantitative description. Frame-by-frame analysis of current videotape recordings shows that the behavioral adaptation to weightlessness is achieved through various processes. Among these are new motor acts and stereotyped movements (successive movements of head, eye, arm, and hand), reversal and reorganization of the sequence of the motor acts to form new patterns (head and eye movements upward or downward), construction of a particular cognitive image of the astronaut's own world (more compensatory regulations than anticipatory processes), and the relationship between postures and orientations according to the proximate visual environment. Furthermore, the present analysis confirms physiological data showing a redistribution of activity between flexor and extensor muscles, and a differential adaptation of vestibulo-ocular reflexes. Thus, this approach suggests new physiological experiments and enables the prediction of behavioral changes occurring during adaptation in microgravity.

Humans↗