Recovery of Cognitive Performance from Sleep Debt: Do a Short Rest Pause and a Single Recovery Night Help?

We studied the recovery of multitask performance and sleepiness from acute partial sleep deprivation through rest pauses embedded in performance sessions and an 8 h recovery sleep opportunity the following night. Sixteen healthy men, aged 19–22 yrs, participated in normal sleep (two successive nights with 8 h sleep) and sleep debt (one 2 h night sleep followed by an 8 h sleep the following night) conditions. In both conditions, the participants performed four 70 min multitask sessions, with every other one containing a 10 min rest pause with light neck‐shoulder exercise. The multitask consisted of four simultaneously active subtasks, with the level of difficulty set in relation to each participant's ability. Physiological sleepiness was assessed with continuous electroencephalography/electro‐oculography recordings during the multitask sessions, and subjective sleepiness was self‐rated with the Karolinska Sleepiness Scale. Results showed that multitask performance and physiological and subjective sleepiness were impaired by the sleep debt (p>.001). The rest pause improved performance and subjective sleepiness for about 15 min, regardless of the amount of prior sleep (p>.01–.05). Following recovery sleep, all outcome measures showed marked improvement (p<.001), but they failed to reach the levels observed in the control condition (p<.001–.05). A correlation analysis showed the participants whose multitask performance deteriorated the most following the night of sleep loss tended to be the same persons whose performance was most impaired following the night of the recovery sleep (p<.001). Taken together, our results suggest that a short rest pause with light exercise is not an effective countermeasure in itself for sleep debt‐induced impairments when long‐term effects are sought. In addition, it seems that shift arrangements that lead to at least a moderate sleep debt should be followed by more than one recovery night to ensure full recovery. Persons whose cognitive performance is most affected by sleep debt are likely to require the most sleep to recover.     

Hidden Biodiversity in an Ecologically Important Freshwater Amphipod: Differences in Genetic Structure between Two Cryptic Species

Cryptic species, i.e. species that are morphologically hard to distinguish, have been detected repeatedly in various taxa and ecosystems. In order to evaluate the importance of this finding, we have to know in how far cryptic species differ in various aspects of their biology. The amphipod Gammarus fossarum is a key invertebrate in freshwater streams and contains several cryptic species. We examined the population genetic structure, genetic diversity and demographic history of two of them (type A and type B) using microsatellite markers and asked whether they show significant differences. We present results of population genetic analyses based on a total of 37 populations from the headwaters of two major European drainages, Rhine and Rhone. We found that, in both species, genetic diversity was geographically structured among and within drainages. For type A in the Rhine and type B in the Rhone, we detected significant patterns of isolation by distance. The increase of genetic differentiation with geographical distance, however, was much higher in type A than in type B. This result indicates substantial interspecific differences in population history and/or the extent of current gene flow between populations. In the Rhine, type B does not show evidence of isolation by distance, and population differentiation is relatively low across hundreds of kilometres. The majority of these populations also show signatures of recent bottlenecks. These patterns are consistent with a recent expansion of type B into the Rhine drainage. In summary, our results suggest considerable and previously unrecognized interspecific differences in the genetic structure of these cryptic keystone species.     

Asynchronicity of Facial Blood Perfusion in Migraine

Asymmetrical changes in blood perfusion and asynchronous blood supply to head tissues likely contribute to migraine pathophysiology. Imaging was widely used in order to understand hemodynamic variations in migraine. However, mapping of blood pulsations in the face of migraineurs has not been performed so far. We used the Blood Pulsation Imaging (BPI) technique, which was recently developed in our group, to establish whether 2D-imaging of blood pulsations parameters can reveal new biomarkers of migraine. BPI characteristics were measured in migraineurs during the attack-free interval and compared to healthy subjects with and without a family history of migraine. We found a novel phenomenon of transverse waves of facial blood perfusion in migraineurs in contrast to healthy subjects who showed synchronous blood delivery to both sides of the face. Moreover, the amplitude of blood pulsations was symmetrically distributed over the face of healthy subjects, but asymmetrically in migraineurs and subjects with a family history of migraine. In the migraine patients we found a remarkable correlation between the side of unilateral headache and the direction of the blood perfusion wave. Our data suggest that migraine is associated with lateralization of blood perfusion and asynchronous blood pulsations in the facial area, which could be due to essential dysfunction of the autonomic vascular control in the face. These findings may further enhance our understanding of migraine pathophysiology and suggest new easily available biomarkers of this pathology.     

Are Sick Individuals Weak Competitors? Competitive Ability of Snails Parasitized by a Gigantism-Inducing Trematode

Parasitized individuals are often expected to be poor competitors because they are weakened by infections. Many trematode species, however, although extensively exploiting their mollusc hosts, also induce gigantism (increased host size) by diverting host resources towards growth instead of reproduction. In such systems, alternatively to reduced competitive ability due to negative effects of parasitism on host performance, larger size could allow more efficient resource acquisition and thus increase the relative competitive ability of host individuals. We addressed this hypothesis by testing the effect of a trematode parasite Diplostomum pseudospathaceum on the competitive ability of its snail host Lymnaea stagnalis. We experimentally examined the growth of snails kept in pairs in relation to their infection status and intensity of resource competition (i.e. food availability). We found that parasitized snails grew faster and their reproduction was reduced compared to unparasitized individuals indicating parasite-induced gigantism. However, growth of the snails was faster when competing with parasitized individuals compared to unparasitized snails indicating reduced competitive ability due to parasitism. The latter effect, however, was relatively weak suggesting that the effects of the parasite on snail physiology may partly override each other in determining competitive ability.     

How does variation in the environment and individual cognition explain the existence of consistent behavioral differences?

According to recent studies on animal personalities, the level of behavioral plasticity, which can be viewed as the slope of the behavioral reaction norm, varies among individuals, populations, and species. Still, it is conceptually unclear how the interaction between environmental variation and variation in animal cognition affect the evolution of behavioral plasticity and expression of animal personalities. Here, we (1) use literature to review how environmental variation and individual variation in cognition explain population and individual level expression of behavioral plasticity and (2) draw together empirically yet nontested, conceptual framework to clarify how these factors affect the evolution and expression of individually consistent behavior in nature. The framework is based on simple principles: first, information acquisition requires cognition that is inherently costly to build and maintain. Second, individual differences in animal cognition affect the differences in behavioral flexibility, i.e. the variance around the mean of the behavioral reaction norm, which defines plasticity. Third, along the lines of the evolution of cognition, we predict that environments with moderate variation favor behavioral flexibility. This occurs since in those environments costs of cognition are covered by being able to recognize and use information effectively. Similarly, nonflexible, stereotypic behaviors may be favored in environments that are either invariable or highly variable, since in those environments cognition does not give any benefits to cover the costs or cognition is not able to keep up with environmental change, respectively. If behavioral plasticity develops in response to increasing environmental variability, plasticity should dominate in environments that are moderately variable, and expression of animal personalities and behavioral syndromes may differ between environments. We give suggestions how to test our hypothesis and propose improvements to current behavioral testing protocols in the field of animal personality.     

Genotypic and phenotypic variation in transmission traits of a complex life cycle parasite

Characterizing genetic variation in parasite transmission traits and its contribution to parasite vigor is essential for understanding the evolution of parasite life‐history traits. We measured genetic variation in output, activity, survival, and infection success of clonal transmission stages (cercaria larvae) of a complex life cycle parasite (Diplostomum pseudospathaceum). We further tested if variation in host nutritional stage had an effect on these traits by keeping hosts on limited or ad libitum diet. The traits we measured were highly variable among parasite genotypes indicating significant genetic variation in these life‐history traits. Traits were also phenotypically variable, for example, there was significant variation in the measured traits over time within each genotype. However, host nutritional stage had no effect on the parasite traits suggesting that a short‐term reduction in host resources was not limiting the cercarial output or performance. Overall, these results suggest significant interclonal and phenotypic variation in parasite transmission traits that are not affected by host nutritional status.     

An experimental heat wave changes immune defense and life history traits in a freshwater snail

The predicted increase in frequency and severity of heat waves due to climate change is expected to alter disease dynamics by reducing hosts' ability to resist infections. This could take place via two different mechanisms: (1) through general reduction in hosts' performance under harsh environmental conditions and/or (2) through altered resource allocation that reduces expression of defense traits in order to maintain other traits. We tested these alternative hypotheses by measuring the effect of an experimental heat wave (25 vs. 15°C) on the constitutive level of immune defense (hemocyte concentration, phenoloxidase [PO]‐like activity, antibacterial activity of hemolymph), and life history traits (growth and number of oviposited eggs) of the great pond snail Lymnaea stagnalis. We also manipulated the exposure time to high temperature (1, 3, 5, 7, 9, or 11 days). We found that if the exposure to high temperature lasted <1 week, immune function was not affected. However, when the exposure lasted longer than that, the level of snails' immune function (hemocyte concentration and PO‐like activity) was reduced. Snails' growth and reproduction increased within the first week of exposure to high temperature. However, longer exposures did not lead to a further increase in cumulative reproductive output. Our results show that short experimental heat waves do not alter immune function but lead to plastic responses that increase snails' growth and reproduction. Thus, although the relative expression of traits changes, short experimental heat waves do not impair snails' defenses. Negative effects on performance get pronounced when the heat waves are prolonged suggesting that high performance cannot be maintained over long time periods. This ultimately reduces the levels of defense traits.     

Zoledronic acid-induced IPP/ApppI production in vivo

Bisphosphonates are currently the most important class of anti-resorptive drugs used for the treatment of diseases involving excess bone resorption. Recently we discovered a new mechanism of action for bisphosphonates. Previously it has been shown that nitrogen-containing bisphosphonates (N-BPs) are not metabolized. However, our studies revealed that N-BPs induce formation of a novel pro-apoptotic ATP analog (ApppI), as a consequence of the inhibition of FPP synthase in the mevalonate pathway, and the subsequent accumulation of isopentenyl pyrophosphate (IPP) in vitro. The primary aim of the current study was to determine whether zoledronic acid (a N-BP) induces IPP/ApppI formation in vivo. Mass spectrometry was used to identify whether in vivo administration of zoledronic acid-induced IPP/ApppI production by mouse peritoneal macrophages or bone marrow cells. IPP/ApppI could be detected in extracts from peritoneal macrophages isolated from zoledronic acid-treated animals. Increasing IPP/ApppI accumulation was determined up to 7 days after drug injection, indicating prolonged FPP synthase inhibition by zoledronic acid. Importantly, this is the first report of in vivo production of ApppI, supporting the biological significance of this molecule.     

Evidence for multiple retroposition events and gene evolution in the ADP/ATP translocase gene family in Ranid frogs

Analysis of partial ADP/ATP Translocase gene (Aat) sequences from 11 species of Ranid frogs (Amphibia: Ranidae) identified multiple Aat gene copies. All frog species examined had at least one of the 2 Aat gene copies differing mainly by presence or absence of an approximately 85-bp intron sequence. The sequence data suggest that the gene variant with intron is the ancestral Aat form, whereas the other variants are retroposed copies. Surprisingly, a phylogenetic analysis suggests that multiple reptroposition events have taken place in the Ranid frogs. An analysis including sequences from Drosophila, zebra fish, Xenopus, mouse, and human indicated that all the frog Aat sequences form a monophyletic group with mammalian X-chromosomal Ant2 as a sister unit. Furthermore, the selection test suggested that different variants of the Aat gene appear to have evolved under different modes of evolution (viz., neutral, purifying, and positive selection), and the evolutionary history of different AAT variants appears to differ even among different species.