[Chronic fatigue syndrome: A new disorder?] / Le syndrome de fatigue chronique : une nouvelle maladie ?

More than 30 years after its individualization, chronic fatigue syndrome (CFS) remains a debilitating condition for the patient and a confusing one to the physicians, both because of diagnostic difficulties and poorly codified management. Despite the numerous work carried out, its pathophysiology remains unclear, but a multifactorial origin is suggested with triggering (infections) and maintenance (psychological) factors as well as the persistence of inflammatory (low grade inflammation, microglial activation…), immunologic (decrease of NK cells, abnormal cytokine production, reactivity to a variety of allergens, role of estrogens…) and muscular (mitochondrial dysfunction and failure of bioenergetic performance) abnormalities at the origin of multiple dysfunctions (endocrine, neuromuscular, cardiovascular, digestive…). The complexity of the problem and the sometimes contradictory results of available studies performed so far are at the origin of different pathophysiological and diagnostic concepts. Based on a rigorous analysis of scientific data, the new American concept of Systemic Disease Exertion Intolerance proposed in 2015 simplifies the diagnostic approach and breaks with the past and terminologies (CFS and myalgic encephalomyelitis). It is still too early to distinguish a new disease, but this initiative is a strong signal to intensify the recognition and management of patients with CFS and stimulate research.

Responses to a novel food acquisition task in three species of lemurs.

In order to study learning and social processes in lemurs, a food acquisition task was presented to three groups: Lemur macaco, L. fulvus and L. catta. The lid of a box had to be pivoted horizontally in order to expose figs contained therein. Individuals in all three groups learned the task, but they showed only limited comprehension. In L. macaco, two adult females learned, with one female showing increasing aggressive monopolization of the new food-source. In L. fulvus, two adult males learned, and one of them increasingly prevented the other from approaching. In L. catta, the adult female frequently threatened away the most efficient opener - a young adult male. The simultaneous presentation of two boxes led to a more equal distribution of the figs. Social processes revealed in the test situation included female dominance in L. macaco and L. catta, and an intermale dominance relationship in L. fulvus. The experimental situation also highlighted the privileged position of the offspring of the dominant female in L. macaco, reduced competitiveness of females with very young infants in L. fulvus, and a general tolerance towards others in L. fulvus.

Social processes and innovative behaviour in changing groups of lemur fulvus.

A group of brown lemurs was presented with one or two baited food-boxes requiring a specific type of motor response in order to be opened. Subsequently, four groups containing different combinations of experienced individuals from the original group and naive individuals were tested. Solutions to the problem and access to the food were recorded and considered in relation to social factors. In the original group, two adult males learned to open the boxes, with one male increasingly preventing the other from approaching. In the second group, with the subordinate male and certain females removed, the dominant male tolerated successful performances by a juvenile female. Group 3 consisted of three passive female participants from the original group and a naive female; one of the three original females now became the sole box-opener. The introduction of the subordinate male from the original group into the all-female group led to a sharing of box-opening by this subject and the skilled female. In the final group, intense aggression toward the skilled female by a new, naive adult male resulted in two previously passive females succeeding on some occasions. In lemurs, at least some 'scroungers' appear able to learn to perform a new act when the social context permits.

Behavioral responses to own and other species' scent marks inLemur fulvus andLemur macaco.

Behavioral responses (duration and frequencies of sniffing, scent marking activity) were studied in one captive group each ofL. fulvus andL. macaco when confronted with their own and other species' scent marks. Both species showed less interest in neutral objects or objects carrying their own group's odor than odors from an unfamiliar group of the same species or from another lemur species. The persistence of scent marks was also investigated.L. fulvus scent appeared to possess greater longevity thanL. macaco scent. Olfactory long-term memory was analyzed inL. fulvus. The results showed that familiar rejected group members could be discriminated from an unfamiliar conspecific through odor cues 10 months after their eviction from the group.

Marking behaviour in two lemur species (L. fulvus and L. macaco): relation to social status, reproduction, aggression and environmental change.

The influence of social status, reproductive and agonistic contexts and environmental change on scent-marking and allomarking rates were studied in captive groups of Lemur fulvus and Lemur macaco. No evidence of female social dominance over males appeared in either species. In L. fulvus, intrasexual relationships were characterized by the dominance of one adult male over another and by the existence of female affiliative association ('central' vs. 'peripheral' females). In L. macaco, no intrasexual dominance relationships were apparent except for a brief ostracism of one female. In both species, (1) intrasexual differences in social status were related to differences in marking rates, (2) no direct relation appeared between marking rates and aggression or reproduction, (3) allomarking was not differentially directed towards specific individuals and (4) physical environmental factors clearly influenced scent-marking and allomarking rates. These results are discussed in relation to the possible functions of marking behaviour in intragroup relations.

[Reactions to mirror in three species of lemurs (Lemur fulvus, L. macaco, L. catta)]. / Les réactions au miroir chez trois espèces de lémuriens (Lemur fulvus, L. macaco, L. catta).

Reactions when confronted with their own reflection in a mirror were observed in three captive groups of lemurs: L. fulvus, L. macaco and L. catta. The ability of a mirror to induce social facilitation of drinking was also studied in one individual of each species. As previously observed in monkeys, the three groups of lemurs showed much more attention to the mirror than to a non-reflective surface, especially nasal contacts. Only L. fulvus showed habituation to the mirror with successive presentations. No social behaviours were directed towards the reflection, in contrast to descriptions of mirror-image reactions in monkeys, and the mirror did not produce an effect of social facilitation. The results suggest that the mirror elicits a diminished social reaction in lemurs compared to monkeys, perhaps due to the absence of relevant olfactory stimuli.