Differences between Staphylococcus aureus lineages isolated from ovine and caprine mastitis but not between isolates from clinical or subclinical mastitis.

Staphylococcus aureus is an important mastitis pathogen, causing both clinical mastitis (CM) and subclinical mastitis (SCM) in small ruminants. In general, CM has a low incidence in sheep and goats but can be very severe and costly. In contrast, subclinical mastitis (SCM) is common but is associated with less cost. For both sheep and goats, S. aureus is the main cause of CM and is associated with SCM cases with a high SCC. Recently, specific lineages of S. aureus have been identified that are associated with CM rather than SCM in dairy cows. It is unknown whether specific S. aureus lineages are associated with CM in goats and sheep. The aim of this study was to compare the clonal complex (CC), staphylococcal protein A (spa) type, leukocidin lukM-lukF' presence, and potential to produce LukMF' in vitro between CM and SCM S. aureus mastitis isolates obtained from sheep and goats. Differences between isolates from different host species were also compared. Ovine (CM, n = 12; SCM, n = 29) and caprine (CM, n = 14; SCM, n = 30) isolates were obtained from 8 sheep flocks and 8 goat herds in the Netherlands. Overall, the isolates belonged to CC133 (85%), CC398 (7%), CC425 (5%), and CC45 (2%). Seventeen spa types were found, including 6 novel types; the predominant types were t2678 (34%), t544 (18%), and t3583 (18%). Although CC133 was dominant among both sheep and goat isolates, spa type CC133/t2678 was associated with ovine isolates, whereas CC133/t544 and CC133/t3583 were found mostly in goats. The presence of lukM-lukF' among the S. aureus isolates was high (87%), especially in CC133 (96%) and CC425 (100%), but the genes were absent in CC45 and CC398. In vitro-cultured lukM-lukF'-positive isolates produced LukM (71 out of 74 positive isolates tested) in the range of 0.4 to 5.0 µg/mL. Interestingly, the goat-associated lineages CC133/t544 and CC133/t3583 produced more LukM in vitro than the sheep-associated CC133/t2678. We found no difference in LukMF' production potential between CM and SCM isolates. In sheep as well as in goats, no association was found between genotype and CM or SCM, demonstrating that the same lineages of S. aureus are responsible for both CM and SCM. These results suggest that subclinically infected animals in a herd or flock likely act as the reservoir of S. aureus causing CM. This highlights the importance of early identification and control of SCM and suggests that controlling SCM within a herd is an effective intervention to prevent CM in small ruminants.

Nimbus: a design-driven analyses suite for amplicon-based NGS data.

Motivation: PCR-based DNA enrichment followed by massively parallel sequencing is a straightforward and cost effective method to sequence genes up to high depth. The full potential of amplicon-based sequencing assays is currently not achieved as analysis methods do not take into account the source amplicons of the detected variants. Tracking the source amplicons has the potential to identify systematic biases, enhance variant calling and improve the designs of future assays. Results: We present Nimbus, a software suite for the analysis of amplicon-based sequencing data. Nimbus includes tools for data pre-processing, alignment, single nucleotide polymorphism (SNP), insertion and deletion calling, quality control and visualization. Nimbus can detect SNPs in its alignment seeds and reduces alignment issues by the usage of decoy amplicons. Tracking the amplicons throughout analysis allows easy and fast design optimization by amplicon performance comparison. It enables detection of probable false positive variants present in a single amplicon from real variants present in multiple amplicons and provides multiple sample visualization. Nimbus was tested using HaloPlex Exome datasets and outperforms other callers for low-frequency variants. The variants called by Nimbus were highly concordant between twin samples and SNP-arrays. The Nimbus suite provides an end-to-end solution for variant calling, design optimization and visualization of amplicon-derived next-generation sequencing datasets. Availability and implementation: https://github.com/erasmus-center-for-biomics/Nimbus. Supplementary information: Supplementary data are available at Bioinformatics online.

A rare missense variant in RCL1 segregates with depression in extended families.

Depression is the most prevalent psychiatric disorder with a complex and elusive etiology that is moderately heritable. Identification of genes would greatly facilitate the elucidation of the biological mechanisms underlying depression, however, its complex etiology has proved to be a major bottleneck in the identification of its genetic risk factors, especially in genome-wide association-like studies. In this study, we exploit the properties of a genetic isolate and its family-based structure to explore whether relatively rare exonic variants influence the burden of depressive symptoms in families. Using a multistep approach involving linkage and haplotype analyses followed by exome sequencing in the Erasmus Rucphen Family (ERF) study, we identified a rare (minor allele frequency (MAF)=1%) missense c.1114C>T mutation (rs115482041) in the RCL1 gene segregating with depression across multiple generations. Rs115482041 showed significant association with depressive symptoms (N=2393, ßT-allele=2.33, P-value=1 × 10-4) and explained 2.9% of the estimated genetic variance of depressive symptoms (22%) in ERF. Despite being twice as rare (MAF<0.5%), c.1114C>T showed similar effect and significant association with depressive symptoms in samples from the independent population-based Rotterdam study (N=1604, ßT-allele=3.60, P-value=3 × 10-2). A comparison of RCL1 expression in human and mouse brain revealed a striking co-localization of RCL1 with the layer 1 interlaminar subclass of astrocytes found exclusively in higher-order primates. Our findings identify RCL1 as a novel candidate gene for depression and offer insights into mechanisms through which RCL1 may be relevant for depression.

NARWHAL, a primary analysis pipeline for NGS data.

UNLABELLED: The NARWHAL software pipeline has been developed to automate the primary analysis of Illumina sequencing data. This pipeline combines a new and flexible de-multiplexing tool with open-source aligners and automated quality assessment. The entire pipeline can be run using only one simple sample-sheet for diverse sequencing applications. NARWHAL creates a sample-oriented data structure and outperforms existing tools in speed. AVAILABILITY: https://trac.nbic.nl/narwhal/.

4-1BB-mediated expansion affords superior detection of in vivo primed effector memory CD8+ T cells from melanoma sentinel lymph nodes.

We have been studying the re-activation of tumor-associated antigen (TAA)-specific CD8(+) T cells in sentinel lymph nodes (SLN) of melanoma patients upon intradermal administration of the CpG-B oligodeoxynucleotide PF-3512676. To facilitate functional testing of T cells from small SLN samples, high-efficiency polyclonal T cell expansion is required. In this study, SLN cells were expanded via classic methodologies with plate- or bead-bound anti-CD3/CD28 antibodies and with the K562/CD32/4-1BBL artificial APC system (K32/4-1BBL aAPC) and analyzed for responsiveness to common recall or TAA-derived peptides. K32/4-1BBL-expanded T cell populations contained significantly more effector/memory CD8(+) T cells. Moreover, recall and melanoma antigen-specific CD8(+) T cells were more frequently detected in K32/4-1BBL-expanded samples as compared with anti-CD3/CD28-expanded samples. We conclude that K32/4-1BBL aAPC are superior to anti-CD3/CD28 antibodies for the expansion of in vivo-primed specific CD8(+) T cells and that their use facilitates the sensitive monitoring of functional anti-tumor T cell immunity in SLN.

End-joining long nucleic acid polymers.

Many experiments involving nucleic acids require the hybridization and ligation of multiple DNA or RNA molecules to form a compound molecule. When one of the constituents is single stranded, however, the efficiency of ligation can be very low and requires significant individually tailored optimization. Also, when the molecules involved are very long (>10 kb), the reaction efficiency typically reduces dramatically. Here, we present a simple procedure to efficiently and specifically end-join two different nucleic acids using the well-known biotin-streptavidin linkage. We introduce a two-step approach, in which we initially bind only one molecule to streptavidin (STV). The second molecule is added only after complete removal of the unbound STV. This primarily forms heterodimers and nearly completely suppresses formation of unwanted homodimers. We demonstrate that the joining efficiency is 50 +/- 25% and is insensitive to molecule length (up to at least 20 kb). Furthermore, our method eliminates the requirement for specific complementary overhangs and can therefore be applied to both DNA and RNA. Demonstrated examples of the method include the efficient end-joining of DNA to single-stranded and double-stranded RNA, and the joining of two double-stranded RNA molecules. End-joining of long nucleic acids using this procedure may find applications in bionanotechnology and in single-molecule experiments.

[Relation between neuroticism and low educational level and the risk of post-traumatic stress disorder in women after miscarriage or stillbirth]. / Verband tussen neuroticisme en laag opleidingsniveau en de kans op posttraumatische stressstoornis bij vrouwen na een miskraam of doodgeboorte.

OBJECTIVE: To determine whether neuroticism and educational level are predictive variables for post-traumatic stress disorder (PTSD) in women following an unsuccessful pregnancy. DESIGN: Prospective. METHOD: In the period June-September 1999, via advertisements in national newspapers, pregnant women with a gestation period shorter than 12 weeks were asked to participate in a study into their perception of the pregnancy. After they had agreed to participate they were given the 'Eysenck personality questionnaire' (EPQ) for neuroticism and other questionnaires, including a scale to determine their highest attained level. Every other month during the pregnancy and one month after the expected date of birth the participants were given brief questionnaires about the pregnancy, in which they were also asked to report miscarriage or stillbirth if such had occurred. Participants in whom the pregnancy had in fact ended unsuccessfully were contacted by telephone and asked to participate in a follow-up study with the 'Post-traumatic symptom scale' (PSS), among others. RESULTS: Of the 1339 women studied, 126 (9%) experienced an unsuccessful pregnancy; 8 of these dropped out of the study (response rate: 94%); one had not indicated her educational level. The remaining 117 women filled out the PSS after about one month. The average age was 31 years (SD: 4). The average duration of gestation at the moment of loss was 12 weeks (SD: 6; range 5-40). The average EPQ-score was 7.3 (SD: 4.6) and the average PSS-score was 18.1 (SD: 9.1). On the basis of the DSM IV, 31 women (26%) fulfilled the criteria for PTSS and 86 women did not. The average PSS-score was 28.2 (SD: 7.0) for the group with PTSS and 14.7 (SD: 6.7) for the group without PTSS. Logistic regression analysis revealed that a later diagnosis of PTSS was significantly associated with a higher score for neuroticism (RR = 4.49; p = 0.004; 95% CI: 1.60-12.60), a lower educational level (RR = 0.65; p = 0.009; 95% CI: 0.48-0.90) and a longer duration of gestation (RR = 2.48; p = 0.001; 95% CI: 1.45-4.25). CONCLUSION: In patients with a high educational level and a low score for neuroticism the risk of developing PTSS was negligible, while with a low educational level and a high score for neuroticism the estimated risk was about 70%. Care and guidance should be concentrated primarily on this group.

Red blood cell and plasma phospholipid arachidonic and docosahexaenoic acid levels at birth and cognitive development at 4 years of age.

OBJECTIVE: The long-chain polyunsaturated fatty acids (LCPUFAs) docosahexaenoic acid (DHA) and arachidonic acid (AA) have biophysical properties that may mediate behavioral outcome, especially cognitive development. This study examined the relationship between the LCPUFA-status at birth and cognitive development at 4 years of age. METHODS: Cognitive development of 128 full-term neonates, whose umbilical venous plasma and/or red blood cell phospholipid DHA and AA levels were known, was assessed at 4 years of age. Pearson correlation coefficients were calculated between cognitive development and DHA, AA, maternal intelligence, birth weight, duration of breast-feeding and paternal educational attainment. Multiple linear regressions were employed with cognitive development as the dependent variable and whereby the above-mentioned covariables were entered in step one while each of the four LCPUFAs was entered in step two. RESULTS: In bivariate analysis, maternal intelligence, birth weight, maternal smoking habits during pregnancy, paternal education and duration of breast-feeding showed significant correlations with cognitive development (p<0.01). The association of cognitive development with DHA and AA measured zero in bivariate analysis (plasma levels: r=0.03 and r=-0.03, respectively; erythrocyte levels: r=0.01 and r=0.05) and in multiple regression analysis (plasma DHA r=0.01, p=0.88; plasma AA r=0.02, p=0.80; erythrocyte DHA r=-0.01, p=0.95) except for erythrocyte AA (r=0.15, p=0.09). CONCLUSION: No evidence was found for an association of the DHA or AA-status at birth with cognitive development at 4 years of age.

The urge to smoke depends on the expectation of smoking.

AIMS: An earlier study (Dols et al. 2000) suggested that cue-induced urge to smoke depends on the expectation of smoking. The present study tried to replicate the findings under stringently controlled conditions. DESIGN: A 2 (context) x 2 (cues) x 6 (trial) within-subject design. Each smoker entered two different contexts; one context predicted the future occurrence of smoking (i.e. one puff of a cigarette) and one context predicted the non-occurrence of smoking. In each context smokers were exposed to smoking cues (i.e. cigarettes and lighter) or not. SETTING: Laboratory at Maastricht University. PARTICIPANTS: Thirty-two daily smokers, smoking at least five cigarettes a day for at least 2 years. MEASUREMENTS: Participants reported their urge to smoke in each context in the presence and absence of smoking cues using a computerized visual analogue scale (VAS). FINDINGS: The results revealed that the urge to smoke was higher in a context in which smoking was expected relative to a context in which it was not expected. As in the previous study the urge-inducing effect of smoking cues was larger in the smoking context than in the non-smoking context. Moreover, smoking cues did not have a significant effect in the non-smoking context. CONCLUSIONS: It was shown that smoking cues elicit craving due mainly to a generated expectation of the occurrence of smoking and less due to salience or long history of associative learning. Theoretical and practical implications of the results are discussed.

Emotion- and intrusion-based reasoning in Vietnam veterans with and without chronic posttraumatic stress disorder.

Patients suffering from anxiety disorders other than posttraumatic stress disorder (PTSD) interpret anxiety responses themselves as evidence that threat is impending: "if anxiety, then threat" (Arntz, Rauner, & van den Hout, 1995, Behaviour Research and Therapy, 33, 917-925). This "emotion-based reasoning" (ER) may render a disorder self-perpetuating. Analogous to ER, danger might also be inferred from the presence of intrusions: "intrusion-based reasoning" (IR). The aims of this study were to test whether ER and IR are involved in chronic PTSD. Vietnam combat veterans with or without PTSD or other anxiety disorders rated perceived danger of brief scenarios in which information about objective danger (danger vs safety) and response (anxiety/intrusions vs non-distressing emotion) was systematically varied. Two series were administered: ER-scenarios were non-specific for PTSD and IR-scenarios were specific for PTSD. Relative to control participants, PTSD patients engaged in both ER and IR: whereas veterans without PTSD inferred the danger of scenarios from objective stimulus information, veterans with PTSD also inferred danger from the presence of anxiety or intrusions. Further analyses showed that these effects were largely mediated by perceived uncontrollability.

Two-dimensional imaging of electronic wavefunctions in carbon nanotubes.

The drive towards the development of molecular electronics is placing increasing demands on the level of control that must be exerted on the electronic structure of materials. Proposed device architectures ultimately rely on tuning the interactions between individual electronic states, which amounts to controlling the detailed spatial structure of the electronic wavefunctions in the constituent molecules. Few experimental tools are available to probe this spatial structure directly, and the shapes of molecular wavefunctions are usually only known from theoretical investigations. Here we present scanning tunnelling spectroscopy measurements of the two-dimensional structure of individual wavefunctions in metallic single-walled carbon nanotubes; these measurements reveal spatial patterns that can be directly understood from the electronic structure of a single graphite sheet, and which represent an elegant illustration of Bloch's theorem at the level of individual wavefunctions. We also observe energy-dependent interference patterns in the wavefunctions and exploit these to directly measure the linear electronic dispersion relation of the metallic single-walled carbon nanotube.

Autobiographical memories become less vivid and emotional after eye movements.

OBJECTIVES: To test (1) whether eye movements during retrieval of emotional memories are followed by less vividness and less emotionality of future recollections, (2) whether this effect, if present, is stronger than the effects of a control activity (finger tapping), (3) whether the alleged effects of tapping and eye movements are stronger than a no-movement, control condition (mere imagery), (4) whether reductions in vividness and emotionality after eye movements (and finger tapping) are specific to negative memories or also occur in the case of positive memories. METHOD: Sixty healthy volunteers recalled either positive or negative memories and scored the vividness and emotionality of the recollections. Next, memories were recalled whilst the participant was performing rapid eye movements, finger tapping, or not performing a dual task. Then participants were asked to recall the event again and to rate its vividness and emotionality. RESULTS: Compared to finger tapping and the no-dual-task condition, recollections after eye movements made future recollections less vivid. After eye movements, but not after the other interventions, negative memories became less negative, and positive memories became less positive. CONCLUSION: The findings show that eye movements not only reduce vividness and emotionality of memories during the eye moving, but also affect future recollections, during which no eye movements are made. Some theoretical explanations are discussed. As to clinical implications, it is suggested that if there is a role for eye-movement-based treatments, it is very limited.

Pain catastrophizing predicts pain intensity, disability, and psychological distress independent of the level of physical impairment.

OBJECTIVE: The aim of the current study was to examine the relation between catastrophizing and pain intensity, pain-related disability, and psychological distress in a group of patients with chronic pain, controlling for the level of physical impairment. Furthermore, it was examined whether these relations are the same for three subgroups of chronic pain patients: those with chronic low back pain, those with chronic musculoskeletal pain other than low back pain, and those with miscellaneous chronic pain complaints, low back pain and musculoskeletal pain excluded. DESIGN: Correlational, cross-sectional. PATIENTS AND SETTING: Participants in this study were 211 consecutive referrals presenting to a university hospital pain management and research center, all of whom had a chronic pain problem. RESULTS: Overall, chronic pain patients who catastrophize reported more pain intensity, felt more disabled by their pain problem, and experienced more psychological distress. Regression analyses revealed that catastrophizing was a potent predictor of pain intensity, disability, and psychological distress, even when controlled for physical impairment. No fundamental differences between the three subgroups were found in this respect. Finally, it was demonstrated that there was no relation between physical impairment and catastrophizing. CONCLUSIONS: It was concluded that for different subgroups of chronic pain patients, catastrophizing plays a crucial role in the chronic pain experience, significantly contributing to the variance of pain intensity, pain-related disability, and psychological distress. These relations are not confounded by the level of physical impairment. Some clinical implications of the results are discussed. Finally, the authors concluded that these results support the validity of a cognitive-behavioral conceptualization of chronic pain-related disability.

Posttraumatic stress disorder after pregnancy loss.

This prospective longitudinal study investigated the prevalence of posttraumatic stress disorder (PTSD) in response to pregnancy loss. About 1,370 women were recruited in the early stages of pregnancy and 113 of them had a subsequent pregnancy loss. One and four months after pregnancy loss, they were assessed for PTSD with the Posttraumatic Symptom Scale. Depression was also assessed. The majority had an early loss, i.e., within 20 weeks. At one month, the prevalence of PTSD was 25%, and the symptom-severity was similar to other traumatized populations. Women with PTSD had increased risk of depression: 34% of PTSD cases and 5% of non-cases reported depression. At four months, 7% met the criteria for PTSD, of which half were chronic. In contrast, rates for depression had not declined. The results indicate that pregnancy loss is potentially traumatic, putting women at risk of developing PTSD. In most cases, the disorder is immediate and persists for several months.

A reaction time paradigm to assess (implicit) complaint-specific dysfunctional beliefs.

We investigated whether an implicit association test (IAT) can be used to assess dysfunctional beliefs in the realm of psychopathology. As a first exploration we therefore constructed a IAT that was designed to differentiate between high and low social anxious individuals. Social situation and neutral words were the targets (e.g. date vs hall), and positive and negative outcomes (e.g. compliment vs rejection) the associated attributes. High social anxious women (N=32) showed the predicted deterioration of task performance if the required responses switched from compatible to incompatible with the idea that social situations are related to negative outcomes and vice versa, whereas the opposite was true for low anxious women (N=32). Thus a modified IAT seems a useful and highly flexible tool to implicitly assess complaint-specific dysfunctional associations and may be a valuable addition to the usual (explicit) self-report measures of patients' beliefs.

On becoming neutral: effects of experimental neutralizing reconsidered.

Behaviour Research and Therapy 34 (1996) 889-898 found that writing out a negative thought produced anxiety and an urge to neutralize the thought, that instructing participants to neutralize the thought reduced anxiety/neutralization urge in the short run (i.e. within 2 min), but that in the control group 20 min without instruction was attended by the same reduction in anxiety/urge to neutralize ("natural decay"). The observations were made with pariticipants who scored high on "thought action fusion" and the experiment was set up as exerimental model of obsessions. We repeated the study with participants that were not selected on thought action fusion. All the findings reported by Behaviour Research and Therapy 34 (1996) 889-898 were replicated. Correlational analysis indicated that the strength of the effect was not related to scores on scales measuring "thought action fusion". Behaviour Research and Therapy 34 (1996) 889-898 did not assess whether non-neutralizing was followed by immediate reductions in distress. We did assess this and found that the larger part of the immediate reduction of distress after neutralization also occurs when no neutralization instruction is given. The effects of neutralization instructions in the present type of experiment are considerably less powerful than suggested earlier.

Does failure hurt? The effects of failure feedback on pain report, pain tolerance and pain avoidance.

In this study an experiment was conducted to examine whether failure experiences have an effect on pain report, pain tolerance and pain avoidance. Furthermore, it was investigated if negative affectivity (NA) affected the impact of failure feedback on pain report, either as a mediator, in the case of negative state affect, or as a moderator when NA as a personality trait was considered. Fifty-four healthy female volunteers were included and randomly assigned to one of three conditions: (1) failure feedback; (2) success feedback; (3) neutral control task. After the manipulation, subjects were given a cold pressor task in order to obtain pain measures. Regarding the effects of failure feedback on pain report, it was found that, in comparison with success feedback, failure feedback led to increased pain report. With regard to pain tolerance, pain was tolerated for longer when preceded by success feedback than when preceded by failure feedback. Differences between failure and control conditions did not reach significance. With regard to pain avoidance, no differences between the conditions were found. The hypothesized mediating role of negative state affect was not found. Though in the hypothesized direction, no significant effect was found for NA-trait moderating the influence of failure on pain. The discussion focuses on a number of research questions that remain to be answered, and the clinical relevance of the effects of failure and success experiences on pain report and pain tolerance.

Counterconditioning in the treatment of spider phobia: effects on disgust, fear and valence.

From the perspective that disgust is a core feature of spider phobia, we investigated whether the treatment efficacy could be improved by adding a counterconditioning procedure. Women with a clinically diagnosed spider phobia (N = 34) were randomly assigned to the regular one-session exposure condition (EXP) or to the exposure with counterconditioning condition (CC). In the CC-condition tasty food-items were used during the regular exposure exercises and the participants' favourite music was played. Both treatment conditions appeared very effective in reducing avoidance behaviour and self-reported fear of spiders, strongly attenuated the disgusting properties of spiders and altered the affective evaluations in a positive direction. CC was not more effective in altering the affective valence of spiders than EXP and was not superior with respect to the long term treatment efficacy at 1 year follow up. Apparently, regular exposure treatment is already quite effective in altering the affective-evaluative component of spider phobia and it remains to be seen whether it is possible to further improve treatment outcome by means of procedures which are specifically designed to reduce the spiders' negative affective valence.

Conscious and preconscious selective attention to social threat: different neuroendocrine response patterns.

This study was designed to investigate the relationship between selective attention to social threat and neuroendocrine activity. Selective attention to social threat was measured using a supraliminal (unmasked) and a subliminal (masked) version of a pictorial emotional Stroop task, comparing color-naming latencies of neutral and angry faces. Neuroendocrine activity was assessed as (pre-task to post-task) increases in salivary cortisol and testosterone. Forty subjects were randomly assigned to the unmasked or masked version of the task. Analyses for the unmasked task revealed that post-task cortisol levels were significantly increased in subjects showing selective attention to angry faces. Results for the masked task indicated that post-task cortisol and testosterone levels were significantly increased in subjects showing preconscious selective attention to angry faces. The difference in neuroendocrine activity between tasks is suggested to depend on cortical (i.e. prefrontal) control in the unmasked task. Thus, psychological affective regulatory processes were involved in the unmasked task, whereas the neuroendocrine response patterns in the masked task indicates a biologically prepared mechanism.

Masked fear words produce increased SCRs: an anomaly for Ohman's theory of pre-attentive processing in anxiety.

A. Ohman and J.J.F. Soares (1994) demonstrated that masked presentation of phobic pictures produces increased skin conductance responses (SCRs) in phobic subjects. A. Ohman (1993) explained this phenomenon in terms of a hypothetical "feature detector" that identifies physical characteristics of stimuli and activates the arousal system without involving significance evaluation or consciousness. By exposing spider phobics to spider words, general threat words, and neutral words instead of pictures, this explanation was tested. Words were presented both masked and unmasked while electrodermal activity was measured. Under unmasked conditions, SCRs were largest for spider words followed by general threat words, then neutral words. When masked, the difference between spider words and general threat words disappeared but SCRs remained significantly smaller for neutral words. It is concluded that activation of the arousal system by masked threat cues does not necessarily depend on their perceptual characteristics.