The neurodynamics underlying attentional control in set shifting tasks

In this work we address key phenomena observed with classical set shifting tasks as the “Wisconsin Card Sorting Test” or the “Stroop” task: Different types of errors and increased response times reflecting decreased attention. A component of major importance in these tasks is referred to as the “attentional control” thought to be implemented by the prefrontal cortex which acts primarily by an amplification of task relevant information. This mode of operation is illustrated by a neurodynamical model developed for a new kind of set shifting experiment: The Wisconsin-Delayed-Match-to-Sample task combines uninstructed shifts as investigated in Wisconsin-like tasks with a Delayed-Match-to-Sample paradigm. These newly developed WDMS experiments in conjunction with the neurodynamical simulations are able to explain the reason for decreased attention in set shifting experiments as well the different consequences of decreased attention in tasks requiring bivalent yes/no responses compared to tasks requiring multivalent responses. Electronic supplementary material  The online version of this article (doi: ) contains supplementary material, which is available to authorized users.

Polymorphism of canonical and noncanonical <Emphasis Type="Italic">gypsy</Emphasis> sequences in different species of <Emphasis Type="Italic">Drosophila </Emphasis><Emphasis Type="Italic">melanogaster</Emphasis> subgroup: possible evolutionary relations

Mobile genetic elements constitute a substantial part of eukaryotic genome and play an important role in its organization and functioning. Co-evolution of retrotransposons and their hosts resulted in the establishment of control systems employing mechanisms of RNA interference that seem to be impossible to evade. However, “active” copies of endogenous retrovirus gypsy escape cellular control in some cases, while its evolutionary elder “inactive” variants do not. To clarify the evolutionary relationship between “active” and “inactive” gypsy we combined two approaches: the analysis of gypsy sequences, isolated from G32 Drosophila melanogaster strain and from different Drosophila species of the melanogaster subgroup, as well as the study of databases, available on the Internet. No signs of “intermediate” (between “active” and “inactive”) gypsy form were found in GenBank, and four full-size G32 gypsy copies demonstrated a convergence that presumably involves gene conversion. No “active” gypsy were revealed among PCR generated gypsy ORF3 sequences from the various Drosophila species indicating that “active” gypsy appeared in some population of D. melanogaster and then started to spread out. Analysis of sequences flanking gypsy variants in G32 revealed their predominantly heterochromatic location. Discrepancy between the structure of actual gypsy sites in G32 and corresponding sequences in database might indicate significant inter-strain heterochromatin diversity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Recoupling and decoupling of nuclear spin interactions at high MAS frequencies: numerical design of CN<Stack><Subscript><Emphasis Type="Italic">n</Emphasis></Subscript><Superscript>ν</Superscript></Stack> symmetry-based RF pulse schemes

The CN _n ^ν class of RF pulse schemes, commonly employed for recoupling and decoupling of nuclear spin interactions in magic angle spinning solid state NMR studies of biological systems, involves the application of a basic “C” element corresponding to an RF cycle with unity propagator. In this study, the design of CN _n ^ν symmetry-based RF pulse sequences for achieving ¹³C–¹³C double-quantum dipolar recoupling and through bond scalar coupling mediated ¹³C–¹³C chemical shift correlation has been examined at high MAS frequencies employing broadband, constant-amplitude, phase-modulated basic “C” elements. The basic elements were implemented as a sandwich of a small number of short pulses of equal duration with each pulse characterised by an RF phase value. The phase-modulation profile of the “C” element was optimised numerically so as to generate efficient RF pulse sequences. The performances of the sequences were evaluated via numerical simulations and experimental measurements and are presented here. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

From view cells and place cells to cognitive map learning: processing stages of the hippocampal system

 The goal of this paper is to propose a model of the hippocampal system that reconciles the presence of neurons that look like “place cells” with the implication of the hippocampus (Hs) in other cognitive tasks (e.g., complex conditioning acquisition and memory tasks). In the proposed model, “place cells” or “view cells” are learned in the perirhinal and entorhinal cortex. The role of the Hs is not fundamentally dedicated to navigation or map building, the Hs is used to learn, store, and predict transitions between multimodal states. This transition prediction mechanism could be important for novelty detection but, above all, it is crucial to merge planning and sensory–motor functions in a single and coherent system. A neural architecture embedding this model has been successfully tested on an autonomous robot, during navigation and planning in an open environment. Received: 28 June 1999 / Accepted in revised form: 26 April 2001     

New target for rice lodging resistance and its effect in a typhoon

We demonstrated the new target for lodging resistance in rice (Oryza sativa L.) by the analysis of physiological function of a locus for lodging resistance in a typhoon (lrt5) with the near isogenic line under rice “Koshihikari” genetic background (tentatively named S1). The higher lodging resistance of S1 was observed during a typhoon in September 2004 (28 days after heading), when most other plants in “Koshihikari” became lodged. Visual observations showed that bending of the upper stems triggered lodging during the typhoon; the upper stem of “Koshihikari” buckled completely, whereas that of S1 remained straight. In addition to the strong rain and winds during the typhoon, the weight of the buckled upper plant parts increased the pressure on adjacent plants and caused a domino effect in “Koshihikari”. Young’s modulus, an indicator of the rigidity of the culm, was significantly higher in S1 than in “Koshihikari”. In the upper culm, the starch content in S1 was 4.8 times the value in “Koshihikari”, and senescence was delayed in the upper leaves of S1. These results suggest that the rigidity of the upper culm by the higher starch content (as a result of delayed senescence in the upper leaves) may be responsible for the higher lodging resistance during a typhoon in rice. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

“Chelatable iron pool”: inositol 1,2,3-trisphosphate fulfils the conditions required to be a safe cellular iron ligand

Mammalian cells contain a pool of iron that is not strongly bound to proteins, which can be detected with fluorescent chelating probes. The cellular ligands of this biologically important “chelatable”, “labile” or “transit” iron are not known. Proposed ligands are problematic, because they are saturated by magnesium under cellular conditions and/or because they are not “safe”, i.e. they allow iron to catalyse hydroxyl radical formation. Among small cellular molecules, certain inositol phosphates (InsPs) excel at complexing Fe³⁺ in such a “safe” manner in vitro. However, we previously calculated that the most abundant InsP, inositol hexakisphosphate, cannot interact with Fe³⁺ in the presence of cellular concentrations of Mg²⁺. In this work, we study the metal complexation behaviour of inositol 1,2,3-trisphosphate [Ins(1,2,3)P ₃], a cellular constituent of unknown function and the simplest InsP to display high-affinity, “safe”, iron complexation. We report thermodynamic constants for the interaction of Ins(1,2,3)P ₃ with Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Fe²⁺ and Fe³⁺. Our calculations indicate that Ins(1,2,3)P ₃ can be expected to complex all available Fe³⁺ in a quantitative, 1:1 reaction, both in cytosol/nucleus and in acidic compartments, in which an important labile iron subpool is thought to exist. In addition, we calculate that the fluorescent iron probe calcein would strip Fe³⁺ from Ins(1,2,3)P ₃ under cellular conditions, and hence labile iron detected using this probe may include iron bound to Ins(1,2,3)P ₃. Therefore Ins(1,2,3)P ₃ is the first viable proposal for a transit iron ligand. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Awake EEG Disregulation in Good Compared to Poor Sleepers

This study was designed to test a disregulation model of sleep deprivation by assessing the ability of good sleepers compared to poor sleepers to shift daytime EEG patterning to changing environmental demands. Ten good and ten poor sleepers were identified from a sample of 110 college students who completed the Pittsburgh Sleep Quality Inventory (PSQI). EEG and SCR were recorded during a five task assessment session, including: (1) pre-baseline, (2) eyes open at rest, (3) eyes closed at rest, (4) sensory attentiveness (listening to an audio book clip), and (5) cognitive effort (a higher level cognitive flexibility task). A significant Group × Task interaction, F (3, 16) = 4.81, p = . 01 was attained on the theta data. Specifically, for good sleepers, theta decreased from the “eyes open at rest” to the “sensory attentiveness” tasks, while poor sleepers showed the opposite pattern. This pattern of theta suppression was found in 70% of the good sleepers and only 20% of the poor sleepers. No between group differences were noted in the SCR data, supporting a brain disregulation model, rather than a general psychophysiological stress model. Partial funding for this research was provided by the office of Research, Grants, and Contracts at the University of Tennessee at Martin.     

Inventory, differentiation, and proportional diversity: a consistent terminology for quantifying species diversity

Almost half a century after Whittaker (Ecol Monogr 30:279–338, 1960) proposed his influential diversity concept, it is time for a critical reappraisal. Although the terms alpha, beta and gamma diversity introduced by Whittaker have become general textbook knowledge, the concept suffers from several drawbacks. First, alpha and gamma diversity share the same characteristics and are differentiated only by the scale at which they are applied. However, as scale is relative––depending on the organism(s) or ecosystems investigated––this is not a meaningful ecological criterion. Alpha and gamma diversity can instead be grouped together under the term “inventory diversity.” Out of the three levels proposed by Whittaker, beta diversity is the one which receives the most contradictory comments regarding its usefulness (“key concept” vs. “abstruse concept”). Obviously beta diversity means different things to different people. Apart from the large variety of methods used to investigate it, the main reason for this may be different underlying data characteristics. A literature review reveals that the multitude of measures used to assess beta diversity can be sorted into two conceptually different groups. The first group directly takes species distinction into account and compares the similarity of sites (similarity indices, slope of the distance decay relationship, length of the ordination axis, and sum of squares of a species matrix). The second group relates species richness (or other summary diversity measures) of two (or more) different scales to each other (additive and multiplicative partitioning). Due to that important distinction, we suggest that beta diversity should be split into two levels, “differentiation diversity” (first group) and “proportional diversity” (second group). Thus, we propose to use the terms “inventory diversity” for within-sample diversity, “differentiation diversity” for compositional similarity between samples, and “proportional diversity” for the comparison of inventory diversity across spatial and temporal scales. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Development of the rhopalial nervous system in <Emphasis Type="Italic">Aurelia</Emphasis> sp.1 (Cnidaria,Scyphozoa)

We examined the development of the nervous system in the rhopalium, a medusa-specific sensory structure, in Aurelia sp.1 (Cnidaria, Scyphozoa) using confocal microscopy. The rhopalial nervous system appears primarily ectodermal and contains neurons immunoreactive to antibodies against tyrosinated tubulin, taurine, GLWamide, and FMRFamide. The rhopalial nervous system develops in an ordered manner: the presumptive gravity-sensing organ, consisting of the lithocyst and the touch plate, differentiates first; the “marginal center,” which controls swimming activity, second; and finally, the ocelli, the presumptive photoreceptors. At least seven bilaterally arranged neuronal clusters consisting of sensory and ganglion cells and their neuronal processes became evident in the rhopalium during metamorphosis to the medusa stage. Our analysis provides an anatomical framework for future gene expression and experimental studies of development and functions of scyphozoan rhopalia. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Mating behavior of the rock catfish, Silurus lithophilus

The mating behavior of the rock catfish Silurus lithophilus (Siluriformes: Siluridae), a species endemic to the Lake Biwa system, was observed from May to July in 1989–1994 along the rocky shore of the lake's outlet, the Seta River. The mating behavior of S. lithophilus involved a certain behavioral sequence: “chasing,”“clinging,” and “enfolding” while “squeezing” by the male; and “circling” by the spawned pair. The mating behavior of this species was basically similar to that of S. biwaensis, but greatly different from that of S. asotus, which spawns in running water (in ditches). The mating behavior of S. lithophilus (and S. biwaensis) might have developed as an adaptation to lentic environments such as the shores of the large river or the lake. Received: October 25, 2000 / Revised: February 25, 2001 / Accepted: March 8, 2001     

Coexistence of congeneric spiny lobsters on coral reefs: differences in conspecific aggregation patterns and their potential antipredator benefits

Den sharing by conspecific spiny lobsters (aggregation) is modulated by chemical attraction but may confer several, not necessarily mutually exclusive, antipredator byproduct benefits: a “guide effect”, which only benefits the individual attracted to a sheltered conspecific; a “dilution effect”, which reduces per-capita risk of predation simply through aggregation; or active “group defense”. Each potential benefit has a different set of predictors (relationships between aggregation and conspecific or predator densities), but conflicting results could suggest the simultaneous operation of more than one benefit. These predictions were tested for coexisting Panulirus guttatus (a reef-obligate) and Panulirus argus (a temporary reef-dweller) using data collected during 11 surveys on fixed sites over a coral reef in Mexico. P. guttatus greatly outnumbered P. argus, but P. argus showed a greater tendency to aggregate. All three benefits of den sharing operated for the more social P. argus, with “group defense” being of the most benefit for larger individuals, and the “guide” and “dilution” effects for smaller individuals recently immigrating into the reef habitat and sharing dens with larger conspecifics. P. guttatus did not display “group defense” and its aggregations appeared to be modulated by the interplay between attraction and aggressive behaviors. This species relied more on solitary crypticity, especially at larger sizes, but appeared to benefit from a “guide effect” at high conspecific densities. In experimental tanks, each species tended to aggregate when tested separately, but when tested jointly, aggregation among P. guttatus was significantly reduced. The experimental results reflect the differential patterns of aggregation between the fore-reef, where P. guttatus dominated, and the back-reef, where coexistence of both species was greater.     

A novel locus for autosomal dominant “uncomplicated” hereditary spastic paraplegia maps to chromosome 8p21.1-q13.3

Hereditary spastic paraplegias (HSPs) are genetically and phenotypically heterogeneous. Both “uncomplicated” and “complicated” forms have been described, with autosomal dominant, autosomal recessive, and X-linked inheritance. Hitherto, ten autosomal dominant “uncomplicated” HSP (ADHSP) loci have been mapped. Here, we report linkage of ADHSP with markers of the 8p21.1-q13.3 chromosomal region in a large French family, including 29 examined at-risk individuals. The age at onset varied from 8 to 60 years with a mean of 31.6 ± 16.4 years. Multipoint and two-point LOD-score calculations as well as haplotype reconstruction in this region gave support to the location of this novel ADHSP locus (SPG37) in a 43.5 cM genetic interval flanked by loci D8S1839 and D8S1795. The region was shared by all definitely (n = 13), probably (n = 3) and possibly (n = 2) affected patients with a maximum LOD score of 4.20 at the D8S601 locus. Two candidate genes, encoding the kinesin family member 13B and neuregulin 1 (isoforms SMDF and GFF2), were screened for mutations, but no disease-causing alterations were identified. Interestingly, another region, on chromosome 10q22.3-23.31, was found to segregate in all affected patients (but not in probably or possibly affected subjects) and in a high proportion of healthy at risk individuals, suggesting that this locus might act as a modifier of the phenotype. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular identification of symbiotic dinoflagellates (Symbiodinium spp.) from Palythoa spp. (Anthozoa: Hexacorallia) in Japan

In Japan, zooxanthellate Palythoa tuberculosa Klunzinger and Palythoa mutuki Verrill (Anthozoa: Hexacorallia: Zoantharia) are found over a 1,000 + km latitudinal range, often in environments where most other zooxanthellate anthozoans are not found (i.e. tidal lagoon pools, around shallow water hydrothermal vents, subtropical rocky shorelines). Sequences of internal transcribed spacer of ribosomal DNA (ITS-rDNA) of the symbiotic dinoflagellate genus Symbiodinium (zooxanthellae) Freudenthal (Order Suessiales) from P. tuberculosa and P. mutuki from several locations in Japan (34°11′N–24°16′N) were analysed. Unexpectedly, despite the ability of the genus Palythoa to be flexible in association with different Symbiodinium subclades, most (35 of 36) Palythoa investigated here specifically associate with subclade C1 and closely related types. Symbiodinium subclade C1 has been characterized as a “generalist” in terms of the ability to associate with a range of hosts, but present results suggest that subclade C1 may also be a “generalist” in terms of being able to live in a variety of environments over a latitudinal range. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

The effects of external potassium and magnesium concentrations on the magnesium and potassium inflow rates and growth of micropropagated cherry rootstocks, “F.12/1” (Prunus avium L.) and “Colt” (Prunus avium L.) × Prunus pseudocerasus L.)

The effects (and interaction) of two solution concentrations of Mg (50, 500, μM) and two of K (250, 4250 μM) on the growth of micropropagated plants of “F. 12/1” and “Colt” were investigated using a flowing solution culture system. Magnesium inflow and growth of “Colt” and “F. 12/1” were inhibited to a similar extent by an increased concentration of K in the nutrient solution. However, the consequences of this inhibition were different. Reduced inflow of Mg in “F. 12/1” caused Mg deficiency symptoms at high and low concentrations of K, whereas this only occurred with a combination of high K concentration and low Mg concentration in “Colt”. The distribution of dry matter within the plant was significant in determining susceptibility to Mg deficiency. Since “F. 12/1” has a smaller root:shoot ratio than Colt it is unable to sustain the same concentration of Mg in leaves as “Colt” irrespective of external K concentration. The molar ratio of K:Mg in soil solutions should remain <8.5:1 in order to ensure maximum growth of “F. 12/1” and “Colt”. This revised version was published online in June 2006 with corrections to the Cover Date.     

Qualitative analysis of a model generating long potential waves in Ba-treated nerve cells—I. Reduced systems

This study is related to a model describing the behavior of barium-treatedAplysia neurons generating regular burst-plateau patterns. The model is represented by an autonomous dynamical system, defined inR ⁴ and depending on a small parameter. This paper is restricted to the qualitative study of three “reduced systems” deduced from the “complete system”. Part of the study is performed with the use of the qualitative theory of singular perturbations. The predicted behaviors are compared with experimental results.     

Motor pattern selection by combinatorial code of interneuronal pathways

We use a modeling approach to examine ideas derived from physiological network analyses, pertaining to the switch of a motor control network between two opposite control modes. We studied the femur–tibia joint control system of the insect leg, and its switch between resistance reflex in posture control and “active reaction” in walking, both elicited by the same sensory input. The femur–tibia network was modeled by fitting the responses of model neurons to those obtained in animals. The strengths of 16 interneuronal pathways that integrate sensory input were then assigned three different values and varied independently, generating a database of more than 43 million network variants. We demonstrate that the same neural network can produce the two different behaviors, depending on the combinatorial code of interneuronal pathways. That is, a switch between behaviors, such as standing to walking, can be brought about by altering the strengths of selected sensory integration pathways. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Salt tolerance in Lycopersicon spp. VII. Pleiotropic action of genes controlling earliness on fruit yield

 The change from vegetative to reproductive development (earliness) in Lycopersicon chesmannii line L2 was delayed for 20 weeks when compared to other Lycopersicon species under greenhouse conditions. The interspecific hybrid of L. chesmannii L2 and L. esculentum E9, a cherry tomato cultivar, also showed this delay in reproductive development. The distribution of this character in the F₂-derived population showed a bimodal shape, plants could be scored easily as “early” or “late” in two nutrient conditions (optimum and high salinity). A QTL with major effects on earliness was detected in salinity, which explained 35.6% of the phenotypic variation. The effect of this QTL greatly diminished under control conditions, indicating differences in the genetic control of earliness between treatments. ACC synthase or phytochrome B2 are the products of candidate genes for such a major QTL. Other QTLs with minor effects, and epistatic interactions, are also involved in earliness under both conditions. A “late” F₂ subpopulation yielded twice as much as an “early” F₂; conversely, “early” plants were taller than “late” plants, regardless of the treatment. QTL analysis, carried out in both subpopulations, showed that yield differences may be explained by chesmannii alleles showing negative additive effects at some QTLs only in the “early” subpopulation. The effect of population subdivision on QTL analysis was investigated by computer simulations to show sample-size or random effects; thus, important pleiotropic or regulatory effects of genes controlling earliness on yield that affect QTL analysis, have been reveiled. Therefore alleles controlling earliness in L. chesmannii have to be taken into account for a more efficient utilization of the genetic resources of this species. Received: 30 June 1998 / Accepted: 31 August 1998     

Phase change-related variations of dome shape in Eucalyptus urophylla × Eucalyptus grandis shoot apical meristems

Shoot apical meristem (SAM) domes derived from five different outdoor and in vitro sources of juvenile and mature Eucalyptus urophylla × Eucalyptus grandis akin genotypes were compared. Overall measurements of SAM dome height H and diameter D ranged from 2 to 35 μm and 20 to 80 μm, with significant differences according to the various physiological origins of plant material investigated. SAM domes from the mature trees “Mat” were taller than those from the rejuvenated ministock plants “Rej”; from the in vitro microcuttings “IVM” of the same clone and also from the in vitro juvenile seedlings “IVJ”, whereas outdoor seedlings “Juv” exhibited intermediate SAM dome height. SAM domes from the rejuvenated material “Rej”, from the in vitro mature “IVM” and juvenile “IVJ” origins were also narrower than those from the outdoor seedlings “Juv” and to lesser extent than those from the mature trees “Mat”. Overall, the mature source “Mat” displayed bigger and somehow sharper hemispherical domes than those from “Rej” and “Juv”, physiologically more juvenile, or those from the in vitro origins “IVM” and “IVJ” which looked flatter and smaller. SAM dome height, diameter D and H/D values varied also significantly according to the plastochron. More specifically, H, D, and H/D SAM differences between the five origins were not significant during the early plastochron phase corresponding to leaf initiation, to become more salient as leaf structures started to elongate and to differentiate. This was particularly obvious for mature tree “Mat” SAM dome shapes which showed at this stage much higher H/D values than the other SAM sources. A shape index S used for characterizing more accurately dome shape confirmed these trends. These observations provide additional arguments to the view that juvenility in trees becomes more and more time- and shoot-tip restricted as ageing increases in the course of time during the ontogenetical process and could be ultimately confined to the most organogenic phase of SAM, from which shoot characteristics derive.