Beheer van duinbossen : verslag veldwerkplaats - duin en kust, PWN Waterleidingbedrijf Noord-Holland, Castricum, 4 juni 2010

De variatie in bostypen wordt in het jonge duinlandschap vooral bepaald door twee belangrijke factoren: water en kalk, zo vertelt Patrick Hommel (Alterra). Natte bossen die permanent onder invloed staan van het grondwater (broekbossen) zijn altijd erg zeldzaam geweest in de duinstreek. Vochtige bossen die in het winterhalfjaar regelmatig onder water lopen, waren vroeger - vooral in het middenduin - veel algemener. Het waren lage bossen (of hoge struwelen!) met veel zachte berk in de boomlaag en een zeer soortenrijke kruidlaag met veelal een hoog aandeel van watermunt. Door verdroging en de daarop volgende verzuring zijn deze bossen sterk van karakter veranderd en de oorspronkelijke soortenrijkdom krijg je waarschijnlijk ook niet meer teru

Sharing tasks or sharing actions? Evidence from the joint Simon task.

In a joint Simon task, a pair of co-acting individuals divide labors of performing a choice-reaction task in such a way that each actor responds to one type of stimuli and ignores the other type that is assigned to the co-actor. It has been suggested that the actors share the mental representation of the joint task and perform the co-actor’s trials as if they were their own. However, it remains unclear exactly which aspects of co-actor’s task-set the actors share in the joint Simon task. The present study addressed this issue by manipulating the proportions of compatible and incompatible trials for one actor (inducer actor) and observing its influences on the performance of the other actor (diagnostic actor) for whom there were always an equal proportion of compatible and incompatible trials. The design of the present study disentangled the effect of trial proportion from the confounding effect of compatibility on the preceding trial. The results showed that the trial proportions for the inducer actor had strong influences on the inducer actor’s own performance, but it had little influence on the diagnostic actor’s performance. Thus, the diagnostic actor did not represent aspects of the inducer actor’s task-set beyond stimuli and responses of the inducer actor. We propose a new account of the effect of preceding compatibility on the joint Simon effect.Action Contro

Threat But Not Arousal Narrows Attention: Evidence from Pupil Dilation and Saccade Control

It has been shown that negative affect causes attentional narrowing. According to Easterbrook’s (1959) influential hypothesis this effect is driven by the withdrawal motivation inherent to negative emotions and might be related to increases in arousal. We investigated whether valence-unspecific increases in physiological arousal, as measured by pupil dilation, could account for attentional narrowing effects in a cognitive control task. Following the presentation of a negative, positive, or neutral picture, participants performed a saccade task with a pro-saccade versus an anti-saccade instruction. The reaction time difference between pro- and anti-saccades was used to index attentional selectivity, and while pupil diameter was used as an index of physiological arousal. Pupil dilation was observed for both negative and positive pictures, which indicates increased physiological arousal. However, increased attentional selectivity was only observed following negative pictures. Our data show that motivational intensity effects on attentional narrowing can occur independently of physiological arousal effects

Genetic Modulation of Training and Transfer in Older Adults: BDNF Val66Met Polymorphism is Associated with Wider Useful Field of View

Western society has an increasing proportion of older adults. Increasing age is associated with a general decrease in the control over task-relevant mental processes. In the present study we investigated the possibility that successful transfer of game-based cognitive improvements to untrained tasks in elderly people is modulated by preexisting neuro-developmental factors as genetic variability related to levels of the brain-derived neurotrophic factor (BDNF), an important neuromodulator underlying cognitive processes. We trained participants, genotyped for the BDNF Val66Met polymorphism, on cognitive tasks developed to improve dynamic attention. Pre-training (baseline) and post-training measures of attentional processes (divided and selective attention) were acquired by means of the useful field of view task. As expected, Val/Val homozygous individuals showed larger beneficial transfer effects than Met/-carriers. Our findings support the idea that genetic predisposition modulates transfer effects

Context-induced contrast and assimilation effects in explicit and implicit measures of agency

Virtual-hand-illusion studies often use explicit and implicit measures of body ownership but no agreed-on implicit measure of agency exists. We investigated whether the Intentional Binding (IB) effect could serve as such a measure. A pilot study confirmed that current consistency increases both perceived agency and IB. In three experiments, current consistency was 50% but the previously experienced consistency was either 100% or 0%. When previous and present consistency experience were separated by a short break, both explicit judgments and IB showed a contrast effect. Eliminating the break reversed the effect in explicit agency but not in IB; and making the transition between previous and present consistency smoother replicated the effect for explicit agency but reversed the pattern for IB. Our findings suggest that explicit agency and IB rely on different sources of information, presumably including cross-sensory correlations, predictions of expected action-effects, and comparisons between present and previous consistency experiences.Action Contro

The roles of consistency and exclusivity in perceiving body ownership and agency

Previous rubber/virtual hand illusion studies have established important constraints for the illusion that an artificial effector becomes part of one’s own body (perceived ownership), and that its actions are being caused by oneself (perceived agency). We can take these observed constraints to establish two of three Wegner’s (Trends Cogn Sci 7:65–69; Wegner, Trends in Cognitive Sciences 7:65–69, 2003) criteria for the perception of personal agency: priority and consistency, but not Wegner’s third criterion—exclusivity. In this study we tested with virtual hand illusion, whether exclusivity (participant is certain who was controlling the virtual effector) can also be established. We manipulated two factors: exclusivity and consistency. Our results show that on both ownership and agency judgments, consistency and exclusivity produced main effects, and the two effects interacted in an underadditive fashion. Taken together, these findings provide support for our suggestion to extend Wegner’s agency theory to explain perceived body ownership, which in turn provides an integrative framework for interpreting constraints on ownership and agency illusions.Action Contro

Representational precision in visual cortex reveals outcome encoding and reward modulation during action preparation

According to ideomotor theory, goal-directed action involves the active perceptual anticipation of actions and their associated effects. We used multivariate analysis of fMRI data to test if preparation of an action promotes precision in the perceptual representation of the action. In addition, we tested how reward magnitude modulates this effect. Finally, we examined how expectation and uncertainty impact neural precision in the motor cortex. In line with our predictions, preparation of a hand or face action increased the precision of neural activation patterns in the extrastriate body area (EBA) and fusiform face area (FFA), respectively. The size of this effect of anticipation predicted individuals\u27 efficiency at performing the prepared action. In addition, increasing reward magnitude increased the precision of perceptual representations in both EBA and FFA although this effect was limited to the group of participants that learned to associate face actions with high reward. Surprisingly, examination of representations in the hand motor cortex and face motor cortex yielded effects in the opposite direction. Our findings demonstrate that the precision of representations in visual and motor areas provides an important neural signature of the sensorimotor representations involved in goal-directed action

Lipopolysaccharide-Activated Canine Platelets Upregulate High Mobility Group Box-1 via Toll-Like Receptor 4

High mobility group box-1 (HMGB1) and the toll-like receptor 4 (TLR4) axis is a key mediator of inflammation. Platelet-derived high mobility group box-1 (HMGB1) may also play a critical role in sepsis-mediated thrombosis resulting in complications like disseminated intravascular coagulation and multiple organ failure. While elevated levels of HMGB1 have been documented in humans and dogs with systemic inflammatory response syndrome and sepsis, a better understanding of how platelet agonists and lipopolysaccharide (LPS) mediate platelet HMGB1 expression would open doors to novel therapies for sepsis-mediated thrombosis. Herein, we sought to determine if canine platelets express HMGB1 in the presence or absence of LPS and agonists (ADP or thrombin) and if surface expression of HMGB1 is dependent on platelet TLR4. Canine platelets were unstimulated (resting) or activated with thrombin or adenosine diphosphate (ADP) in the presence or absence of Escherichia coli LPS prior to flow cytometric and western blot analyses for HMGB1 expression. We also treated canine platelets with or without TLR4 function blocking antibody or its isotype control. We discovered that while thrombin upregulated both surface and cellular HMGB1 expression, LPS-mediated activation in the presence of ADP priming led to upregulation of surface HMGB1 expression. This expression was found to be most prominent in platelets that had undergone alpha-granule secretion. Inhibition of TLR4 attenuated LPS-induced HMGB1 expression indicating that exteriorization of HMGB1 may be dependent on the non-genomic pathway of platelet TLR4. Our findings indicate that upregulation of platelet-derived HMGB1 occurs as a result of thrombin or TLR4-mediated activation in dogs. Future studies should explore the translational implication of platelet-derived HMGB1 as novel therapeutic targets in humans and dogs with sepsis