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Applied to the nasal mucosa in low concentrations, nicotine vapor evokes odorous sensations (mediated by the olfactory system) whereas at higher concentrations nicotine vapor additionally produces burning and stinging sensations in the nose (mediated by the trigeminal system). The objective of this study was to determine whether intranasal stimulation with suprathreshold concentrations of S(-)-nicotine vapor causes brain activation in olfactory cortical areas or if trigeminal cortical areas are also activated. Individual olfactory detection thresholds for S(-)-nicotine were determined in 19 healthy occasional smokers using a computer-controlled air-dilution olfactometer. Functional magnetic resonance images were acquired using a 1.5T MR scanner with applications of nicotine in concentrations at or just above the individual"s olfactory detection threshold. Subjects reliably perceived the stimuli as being odorous. Accordingly, activation of brain areas known to be involved in processing of olfactory stimuli was identified. Although most of the subjects never or only rarely observed a burning or painful sensation in the nose, brain areas associated with the processing of painful stimuli were activated in all subjects. This indicates that the olfactory and trigeminal systems are activated during perception of nicotine and it is not possible to completely separate olfactory from trigeminal effects by lowering the concentration of the applied nicotine. In conclusion, even at low concentrations that do not consistently lead to painful sensations, intranasally applied nicotine activates both the olfactory and the trigeminal system.
Values are assumed to be relatively stable during adulthood. Yet, little research has examined value stability and change, and there are no studies on the structure of value change. On the basis of S. H. Schwartz's (1992) value theory, the authors propose that the structure of intraindividual value change mirrors the circumplexlike structure of values so that conflicting values change in opposite directions and compatible values change in the same direction. Four longitudinal studies, varying in life contexts, time gaps, populations, countries, languages, and value measures, supported the proposed structure of intraindividual value change. An increase in the importance of any one value is accompanied by slight increases in the importance of compatible values and by decreases in the importance of conflicting values. Thus, intraindividual changes in values are not chaotic, but occur in a way that maintains Schwartz's value structure. Furthermore, the greater the extent of life-changing events, the greater the value change found, whereas age was only a marginal negative predictor of value change when life events were taken into account. Implications for the structure of personality change are discussed.
Depressive Störungen
(2009)
There is ample evidence that the early initiation of alcohol use is a risk factor for the development of later alcohol-related problems. The purpose of the current study was to examine whether this association can be explained by indicators of a common underlying susceptibility or whether age at drinking onset may be considered as an independent predictor of later drinking behavior, suggesting a potential causal relationship. Participants were drawn from a prospective cohort study of the long-term outcomes of early risk factors followed up from birth onwards. Structured interviews were administered to 304 participants to assess age at first drink and current drinking behavior. Data on risk factors, including early family adversity, parental alcohol use, childhood psychopathology and stressful life events, were repeatedly collected during childhood using standardized parent interviews. In addition, information on genotype was considered. Results confirmed previous work demonstrating that hazardous alcohol consumption is related to early-adolescent drinking onset. A younger age of first drink was significantly predicted by 5-HTTLPR genotype and the degree of preceding externalizing symptoms, and both factors were related to increased consumption or harmful alcohol use at age 19. However, even after controlling for these potential explanatory factors, earlier age at drinking onset remained a strong predictor of heavy alcohol consumption in young adulthood. The present longitudinal study adds to the current literature indicating that the early onset - adult hazardous drinking association cannot solely be attributed to shared genetic and psychopathologic risk factors as examined in this study.
Achievement motive imagery in German schoolbooks : a pilot study testing McClelland's hypothesis
(2009)
McClelland [McClelland, D.C. (1961). The achieving society. Princeton, NJ: Van Nostrand] observed that the amount of achievement imagery in children's books predicted the economic development of societies. He argued that achievement imagery is an indicator of a motivational climate, and when children grow up in a society that emphasizes the striving for achievement, they will be more economically productive later on. We tested McClelland's hypothesis by coding school textbooks for achievement imagery from two German federal states (Baden-Wurttemberg and Bremen) with pronounced differences in economic and educational conditions. As expected, the schoolbooks from the state with the more advantageous conditions contained more achievement imagery.
This prospective longitudinal study of a representative community sample of children and adolescents (N = 269) examined the long-term course and predictive power of psychiatric symptoms in childhood/adolescence for diagnostic outcome (ICD-10) 18 years later at adult age. At both cross-sectional assessments, baseline (1980-1984) and the 18-year follow-up (2001-2004), psychiatric symptoms were assessed using the 'Standardized Psychiatric Interview' (Goldberg et al. in Br J Prev Soc Med 24:18-23, 1970). At follow-up, study participants were reassessed with the standardized M-CIDI (Wittchen and Pfister in Manual und Durchfuhrungsbeschreibung des DIA-X-M-CIDI, Swets and Zeitlinger, Frankfurt, 1997) interview. The participation rate at 18-year follow-up was 82% of those alive. The frequency of clinically relevant depressive symptoms and symptoms of anxiety or phobia was considerably higher when the participants were younger (baseline assessment at childhood, adolescent age) as compared to their scores in adult age. Increased levels of somatic symptoms, fatigue, irritability, sleep disturbances, depression, anxiety and worry as well as phobic symptoms in childhood/adolescence were related to a higher risk of suffering from a psychiatric disorder in adulthood. Depressive symptoms predicted both mood disorders and substance use disorders in adulthood. Phobias predicted later anxiety disorders. These data spanning almost two decades add significant information to the existing literature on the course of mental disorders in the community during the transition from adolescence to adulthood.
The present study aimed to clarify the functional role of genes in the dopamine and serotonin systems by examining whether polymorphisms in these genes are related to adolescent externalizing behavior either alone or in interaction with each other. Participants were selected from an ongoing prospective study of the outcome of early risk factors. At age 15 years, 298 adolescents (144 males, 154 females) completed the Youth Self Report, 296 primary caregivers the Child Behavior Checklist and 253 teachers the Teacher Report Form. DNA was genotyped for the DRD4 exon III VNTR and the 5-HTTLPR polymorphisms. Results revealed that individuals with the DRD4 7r allele reported significantly more externalizing behavior than carriers of other variants. In addition, a significant interaction emerged, indicating that adolescents carrying two copies of the 5-HTTLPR short allele and the DRD4 7r variant scored highest on aggressive and/or delinquent behavior compared to other genotypes. This result suggests an effect of 5-HTTLPR on externalizing behavior in the presence of DRD4 7r but no effect in its absence.
Two experiments are presented that test the predictions of two associative learning models of Artificial Grammar Learning. The two models are the simple recurrent network (SRN) and the competitive chunking (CC) model. The two experiments investigate acquisition of different types of knowledge in this task: knowledge of frequency and novelty of stimulus fragments (Experiment 1) and knowledge of letter positions, of small fragments, and of large fragments up to entire strings (Experiment 2). The results show that participants acquired all types of knowledge. Simulation studies demonstrate that the CC model explains the acquisition of all types of fragment knowledge but fails to account for the acquisition of positional knowledge. The SRN model, by contrast, accounts for the entire pattern of results found in the two experiments.
Compared with visual and auditory imagery, little is known about olfactory imagery. There is evidence that respiration may be altered by both olfactory perception and olfactory imagery. In order to investigate this relationship, breathing parameters (respiratory minute volume, respiratory amplitude, and breathing rate) in human subjects during olfactory perception and olfactory imagery were investigated. Fifty-six subjects having normal olfactory function were tested. Nasal respiration was measured using a respiratory pressure sensor. Using an experimental block design, we alternately presented odors or asked the subjects to imagine a given smell. Four different pleasant odors were used: banana, rose, coffee, and lemon odor. We detected a significant increase in respiratory minute volume between olfactory perception and the baseline condition as well as between olfactory imagery and baseline condition. Additionally we found significant differences in the respiratory amplitude between imagery and baseline condition and between odor and imagery condition. Differences in the breathing rate between olfactory perception, olfactory imagery, and baseline were not statistically significant. We conclude from our results that olfactory perception and olfactory imagery both have effects on the human respiratory profile and that these effects are based on a common underlying mechanism.
There is growing evidence from the international literature that nonconsensual sexual interactions are widespread among adolescents and young adults. Following a brief review of this literature, two studies are reported that examined the prevalence and predictors of sexual aggression and sexual victimization among young people in Germany. In addition to the traditional focus on male perpetrators and female victims, evidence is presented on women's sexual aggression towards men and men's sexual victimization by women. Variables increasing the risk of sexual aggression and vulnerability for victimization include both biographical factors (e. g., childhood abuse) and situational variables (e. g., ambiguous communication of sexual intentions). Special consideration is given to the representation of risk factors in the "sexual scripts" for consensual sexual interactions that serve as guidelines for sexual behavior. The paper concludes with a brief discussion of the implications of the findings for prevention efforts.
The study reports a group-randomized trial of a theatre-based intervention to prevent sexual abuse targeting first and second grade primary school children in Germany. A sample of 148 first and second graders saw a live performance of a play designed to promote skills in dealing with abuse-prone interactions with adults, watched a recording of the play on DVD or were assigned to a no intervention control group. Both the live performance and the DVD groups showed significant increases in the target variables (distinguishing good/bad touch and secrets, getting help, rejecting unwanted touch) from baseline to post-intervention and a follow-up after 2 weeks, while the control group did not show changes. The live performance and DVD groups participated in a further follow-up 30 weeks post-intervention, which showed sustained effects of the intervention. The findings indicate that with appropriately culture-sensitive measures, Sexual abuse prevention programmes can have Sustainable effects with young primary school children.
Vorgestellt wird ein Instrument zur Erhebung muetterlicher Steuerungsstrategien in der Essenssituation (ISS), fuer deren Erfassung bislang kein deutschsprachiges, ueberprueftes Instrument vorliegt. Dazu wurde an 163 Muettern mit Vorschulkindern ein auf Grundlage bereits existierender englischsprachiger Instrumente (CFQ, CFSQ) sowie Fokusinterviews mit Experten und Muettern entstandener Itempool ueberprueft. Die Studie berichtet ueber die faktoren- und itemanalytischen Ergebnisse, nach denen sich 21 Items als trennscharf und verstaendlich erwiesen. Eine explorative Faktorenanalyse ergab sechs Faktoren, die zusammen 68% der Varianz aufklaerten. Sie umfassen aktive Strategien, wie Restriktion, Draengen und Belohnung, aber auch passive Steuerung durch Vorbild, Monitoring und die Staerkung der Eigenverantwortung des Kindes. Analysen zu Unterschieden im Steuerungsverhalten der Mutter bestaetigten die Faehigkeit des Instrumentes zur Differenzierung zwischen Muettern mit verschiedenem soziooekonomischen Status und Kindern unterschiedlichen Gewichts.
Background: Research concerning child's food intake have considered various influencing factors, for example parental feeding strategies, demographic and weight factors. At this time, however, there are few findings that explore these factors simultaneously. Accordingly, the aim of this study was to test a structural equation model regarding the associations between maternal feeding strategies and child's food intake. Methods: 556 mothers and their children between 1 and 10 years of age participated in this cross-sectional study. Besides socio-demographic and weight data, the mothers were asked about their feeding strategies as well as their child's food intake. Results: The well-fitting model explained 73% of the variance in the child's consumption of healthy and 34% of unhealthy food. In addition to the effect of the mother's social status and the child's age, a rewarding and modeling feeding behavior significantly influenced the child's food intake. Conclusion: The results highlight the relevance of maternal feeding behavior on the child's food intake. In terms of preventing eating- or weight-related problems, the findings indicate the usefulness of training parents in explicit modeling behavior and avoiding food as a reward.
Research on voluntary action has focused on the question of how we represent our behavior on a motor and cognitive level. However, the question of how we represent voluntary not acting has been completely neglected. The aim of the present study was to investigate the cognitive and motor representation of intentionally not acting. By using an action-effect binding approach, we demonstrate similarities of action and nonaction. In particular, our results reveal that voluntary nonactions can be bound to an effect tone. This finding suggests that effect binding is not restricted to an association between a motor representation and a successive effect (action-effect binding) but can also occur for an intended nonaction and its effect (nonaction-effect binding). Moreover, we demonstrate that nonactions have to be initiated voluntarily in order to elicit nonaction-effect binding.
No age differences in complex memory search : older adults search as efficiently as younger adults
(2009)
In 2 experiments, the authors investigated age differences in memory search under 4 conditions: forward search, backward search, random search, and fixed irregular search. Both search slopes and serial position curves were investigated. Mixing conditions led to smaller age differences than blocking conditions, suggesting that younger adults have an advantage over older adults when strategies can be applied to memory scanning. All age differences in scanning rates, however, disappeared when age differences in a magnitude-judgment control task were controlled for, showing that age differences in memory scanning tasks are not because of the scanning process per se, but because of attention, sensorimotor speed, and decision processes. In both experiments, the serial position curves of older adults echoed those of younger adults closely, demonstrating that younger and older adults use the same scanning processes.
Previous research examining gene-environment interaction (G x E) with regard to vulnerability to depression and anxiety has yielded conflicting results. The present study was designed to further investigate G x F between 5-HTTLPR and exposure to environmental adversity, using different phenotypic and genotypic characterizations as well as different types of adversity within a prospective study design. Data were available from an ongoing epidemiological cohort Study following the outcome of early risk factors from birth to adulthood. At age 19 yr, 309 participants (142 males, 167 females) were characterized on measures of depression and anxiety through interview and questionnaire (DSM-IV diagnosis, Beck Depression Inventory, Harm Avoidance). Environmental adversity was assessed at birth (family adversity), and at age 19 yr (stressful life events). Bi- and tri-allelic 5-HTTLPR genotypes were obtained from genomic DNA. Results indicated that depression and anxiety in 19-yr-olds were strongly associated with both family adversity and stressful life events. Individuals with the LL genotype of 5-HTTLPR who were exposed to high family adversity displayed significantly higher rates of depressive or anxiety disorders and had more depressive symptoms than those without either condition. This G x E replicates recent findings from an epidemiological cohort study of adolescents but is in contrast to many previous reports suggesting an interaction with the S allele. No evidence for G x E was obtained with regard to current stressful life events and trait anxiety. One possible source for the conflicting findings might be attributed to heterogeneity in depression phenotypes and environmental adversity.
Background: Evidence from animal studies supports a role for serotonin transporter gene promoter polymorphism (5-HTTLPR) gene-environment interaction (G X E) in the development of excessive alcohol intake. Few studies in humans have been conducted on this topic, yielding inconsistent results. The present study aims to further explore G x E between 5-HTTLPR and exposure to psychosocial adversity on alcohol consumption in a high-risk community sample of young adults. Methods: Data were collected as part of the Mannheim Study of Children at Risk, an ongoing epidemiological cohort study following the outcome of early risk factors from birth into young adulthood. At age 19 years, 309 participants (142 male participants, 167 female participants) were genotyped for the biallelic and triallelic 5-HTTLPR and were administered a 45-day alcohol timeline follow-back interview, providing measures of the total number of drinks and the number of binge drinking days. Psychosocial adversity was assessed at birth (family adversity) and at age 19 (negative life events). Results: In contrast to various previous reports, a significant G x E emerged, indicating that, when exposed to high psychosocial adversity, individuals with the LL genotype of 5-HTTLPR exhibited more hazardous drinking than those carrying the S allele or those without exposure to adversity. This effect, which was confined to male participants, held both for different classifications of 5-HTTLPR and different types of adversity. Conclusions: One explanation for the discrepant results might be heterogeneity in alcohol phenotypes. While the L allele relates more strongly to early-onset alcoholism, the S allele may be linked more closely to alcohol use associated with anxiety and depression.
Multiple regression analyses in artificial-grammar learning : the importance of control groups
(2009)
In artificial-grammar learning, it is crucial to ensure that above-chance performance in the test stage is due to learning in the training stage but not due to judgemental biases. Here we argue that multiple regression analysis call be successfully combined with the use of control groups to assess whether participants were able to transfer knowledge acquired during training where making judgements about test stimuli. We compared the regression weights of judgements in a transfer condition (training and test strings were constructed by the same grammar but with different letters) with those in a control condition. Predictors were identical in both conditions-judgements of control participants were treated as if they were based oil knowledge gained in a standard training stage. The results of this experiment as well as reanalyses of a former study support the usefulness of our approach.
On the relationship between interoceptive awareness and the attentional processing of visual stimuli
(2009)
Mental processes related to visceral activity have gained growing interest during the last few years. The following study is the first to investigate possible interactions between interoceptive awareness and measures of attentional performance. We tested the hypothesis whether interoceptive awareness is positively related to indices of selective and divided attentional performances. Using a heartbeat perception task, 29 healthy female participants were separated into two groups scoring either high or low in an interoceptive awareness task. Attentional performance was assessed by several tests including the 'd2 test of attention' and subtests from the 'TAP: Test Battery for Attentional Performance'. We observed a significantly better performance in selective and divided attention for participants with high interoceptive awareness. Our data suggests that interoceptive awareness is related to a better performance especially in tasks assessing selective and divided attention. We conclude 1) that perception of bodily states might be a crucial determinant for the processing of external, visual stimuli, 2) that the ability to perceive internal signals might be an indicator of self-focused attention, and 3) that bodily signals may use, at least in part, similar processing resources as signals from the attention system.
We compared individual-participant and jackknife-based methods for scoring the onset latencies of event-related potential (ERP) components using a diffusion process as a model for an ERP. We studied "ramp-like" components in which the true ERP increases or decreases monotonically, except for noise. If the growth rates of such components vary across participants, the jackknife-based measure can easily have only 10%-20% as much error variance as the traditional method, and this advantage is magnified with more participants. We also studied boolean AND-shaped or "bump-like" components. Jackknifing generally yielded smaller error variances with these components too, especially when the component's peak amplitude varied across participants, but less so if the component's peak latency varied. These results help illuminate the reasons for the superiority of jackknife-based onset latency measures over traditional measures in recent simulations.
Exposure to violent video games and aggression in German adolescents : a longitudinal analysis
(2009)
The relationship between exposure to violent electronic games and aggressive cognitions and behavior was examined in a longitudinal study. A total of 295 German adolescents completed the measures of violent video game usage, endorsement of aggressive norms, hostile attribution bias, and physical as well as indirect/relational aggression cross- sectionally, and a subsample of N = 143 was measured again 30 months later. Cross-sectional results at T1 showed a direct relationship between violent game usage and aggressive norms, and an indirect link to hostile attribution bias through aggressive norms. In combination, exposure to game violence, normative beliefs, and hostile attribution bias predicted physical and indirect/relational aggression. Longitudinal analyses using path analysis showed that violence exposure at T1 predicted physical (but not indirect/relational) aggression 30 months later, whereas aggression at T1 was unrelated to later video game use. Exposure to violent games at T1 influenced physical (but not indirect/relational) aggression at T2 via an increase of aggressive norms and hostile attribution bias. The findings are discussed in relation to social-cognitive explanations of long-term effects of media violence on aggression.
In this article, we revisit the mindless reading paradigm from the perspective of computational modeling. In the standard version of the paradigm, participants read sentences in both their normal version as well as the transformed (or mindless) version where each letter is replaced with a z. z-String scanning shares the oculomotor requirements with reading but none of the higher-level lexical and semantic processes. Here we use the z-string scanning task to validate the SWIFT model of saccade generation [Engbert, R., Nuthmann, A., Richter, E., & Kliegl, R. (2005). SWIFT: A dynamical model of saccade generation during reading. Psychological Review, 112(4), 777-813] as an example for an advanced theory of eye-movement control in reading. We test the central assumption of spatially distributed processing across an attentional gradient proposed by the SWIFT model. Key experimental results like prolonged average fixation durations in z-string scanning compared to normal reading and the existence of a string-length effect on fixation durations and probabilities were reproduced by the model, which lends support to the model's assumptions on visual processing. Moreover, simulation results for patterns of regressive saccades in z-string scanning confirm SWIFT's concept of activation field dynamics for the selection of saccade targets.
Binocular eye movements of normal adult readers were examined as they read single sentences. Analyses of horizontal and vertical fixation disparities indicated that the most prevalent type of disparate fixation is crossed (i.e., the left eye is located further to the right than the right eye) while the left eye frequently fixates somewhat above the right eye. The Gaussian distribution of the binocular fixation point peaked 2.6 cm in front of the plane of text, reflecting the prevalence of horizontally crossed fixations. Fixation disparity accumulates during the course of successive saccades and fixations within a line of text, but only to an extent that does not compromise single binocular vision. In reading, the version and vergence system interact in a way that is qualitatively similar to what has been observed in simple nonreading tasks. Finally, results presented here render it unlikely that vergence movements in reading aim at realigning the eyes at a given saccade target word.
The article presents a mathematical model of short-term recognition based on dual-process models and the three- component theory of working memory [Oberauer, K. (2002). Access to information in working memory: Exploring the focus of attention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28, 411-421]. Familiarity arises from activated representations in long-term memory, ignoring their relations; recollection retrieves bindings in the capacity- limited component of working memory. In three experiments participants encoded two short lists of nonwords for immediate recognition, one of which was then cued as irrelevant. Probes from the irrelevant list were rejected more slowly than new probes; this was also found with probes recombining letters of irrelevant nonwords, suggesting that familiarity arises from individual letters independent of their relations. When asked to accept probes whose letters were all in the relevant list, regardless of their conjunction, participants accepted probes preserving the original conjunctions faster than recombinations, showing that recollection accessed feature bindings automatically. The model fit the data best when familiarity depended only on matching letters, whereas recollection used binding information.
The article reports an experiment testing whether the Hebb repetition effectthe gradual improvement of immediate serial recall when the same list is repeated several timesdepends on overt recall of the repeated lists. Previous reports which suggest that recall is critical confound the recall manipulation with retention interval. The present experiment orthogonally varies retention interval (0 or 9 s) and whether the list is to be recalled after the retention interval. Hebb repetition learning is assessed in a final test phase. A repetition effect was obtained in all four experimental conditions; it was larger for recalled than non-recalled lists, whereas retention interval had no effect. The results show that encoding is sufficient to generate cumulative long-term learning, which is strengthened by recall. Rehearsal, if it takes place in the retention interval at all, does not have the same effect on long-term learning as overt recall.
Three experiments investigated proactive interference and proactive facilitation in a memory-updating paradigm. Participants remembered several letters or spatial patterns, distinguished by their spatial positions, and updated them by new stimuli up to 20 times per trial. Self-paced updating times were shorter when an item previously remembered and then replaced reappeared in the same location than when it reappeared in a different location. This effect demonstrates residual memory for no-longer-relevant bindings of items to locations. The effect increased with the number of items to be remembered. With one exception, updating times did not increase, and recall of final values did not decrease, over successive updating steps, thus providing little evidence for proactive interference building up cumulatively.
In a high-risk community sample, we examined the role of regulative temperament and emotionality as well as the extent of gender specificity in the development of externalizing problems. 151 boys and 157 girls born at differing degrees of obstetric and psychosocial risk were followed from birth into adolescence. In infancy and childhood, NYLS- derived temperamental characteristics were assessed by a highly structured parent interview and standardized behavioral observations. At age 15 years, externalizing problems were measured by the Child Behavior Checklist. As revealed by multiple linear regression and logistic regression, low regulative abilities predicted adolescent behavioral and attentional problems over and above obstetric and psychosocial risks. Gender specificity was found in the strength of the association rather than in the kind with a stronger long-term prediction from infant and toddler temperament in girls. Compared to regulative abilities, temperament factors describing aspects of mood and fear/withdrawal versus approach tendencies played a minor role in the development of externalizing problems. Findings are discussed in terms of gender-specific risk factors and possible differential developmental trajectories to subtypes of disruptive behavior.
BACKGROUND: Feedback from the body is assumed to be altered in depression. Nevertheless, empirical studies investigating this assumed relationship remain sparse. This study aimed to examine interrelations between the ability to perceive heartbeats accurately (interoceptive awareness), depressive symptoms, and anxiety in healthy participants. METHODS: A well-validated heartbeat perception task to measure interoceptive awareness together with two questionnaires indexing anxiety and depression were administered to 119 participants. RESULTS: As main results we observed a negative correlation between heartbeat perception and depression. Only when focussing on high anxiety levels this negative correlation coefficient between depression and interoception remained significant. CONCLUSIONS: Our results highlight the possible relationship between depressive symptoms and interoceptive awareness and may have further implications for theoretical models of anxiety disorders and their treatment. Further research is required to examine the potential consequences of altering interoceptive awareness in healthy subjects in relation to depression and anxiety.
Contrary to common wisdom, fixations are a dynamically rich behavior, composed of continual, miniature eye movements, of which microsaccades are the most salient component. Over the last few years, interest in these small movements has risen dramatically, driven by both neurophysiological and psychophysical results and by advances in techniques, analysis, and modeling of eye movements. The field has a long history but a significant portion of the earlier work has gone missing in the current literature, in part, as a result of the collapse of the field in the 1980s that followed a series of discouraging results. The present review compiles 60 years of work demonstrating the unique contribution of microsaccades to visual and oculomotor function. Specifically, the review covers the contribution of microsaccades to (1) the control of fixation position, (2) the reduction of perceptual fading and the continuity of perception, (3) the generation of synchronized visual transients, (4) visual acuity, (5) scanning of small spatial regions, (6) shifts of spatial attention, (7) resolving perceptual ambiguities in the face of multistable perception, as well as several other functions. The accumulated evidence demonstrates that microsaccades serve both perceptual and oculomotor goals and although in some cases their contribution is neither necessary nor unique, microsaccades are a malleable tool conveniently employed by the visual system.
The method of twin surrogates has been introduced to test for phase synchronization of complex systems in the case of passive experiments. In this paper we derive new analytical expressions for the number of twins depending on the size of the neighborhood, as well as on the length of the trajectory. This allows us to determine the optimal parameters for the generation of twin surrogates. Furthermore, we determine the quality of the twin surrogates with respect to several linear and nonlinear statistics depending on the parameters of the method. In the second part of the paper we perform a hypothesis test for phase synchronization in the case of experimental data from fixational eye movements. These miniature eye movements have been shown to play a central role in neural information processing underlying the perception of static visual scenes. The high number of data sets (21 subjects and 30 trials per person) allows us to compare the generated twin surrogates with the "natural" surrogates that correspond to the different trials. We show that the generated twin surrogates reproduce very well all linear and nonlinear characteristics of the underlying experimental system. The synchronization analysis of fixational eye movements by means of twin surrogates reveals that the synchronization between the left and right eye is significant, indicating that either the centers in the brain stem generating fixational eye movements are closely linked, or, alternatively that there is only one center controlling both eyes.
Motivation
(2009)
Recent evidence suggests that heterogeneity in the age at onset could explain the inconsistent findings of association studies relating the dopamine transporter (DAT1) gene with alcohol and nicotine consumption. The aim of this study was to examine interactions between two DAT1 polymorphisms and different initiation ages with regard to alcohol and tobacco consumption levels and dependence. Two hundred and ninety-one young adults (135 males, 156 females) participating in the Mannheim Study of Children at Risk were genotyped for the 40-bp variable number of tandem repeats (VNTR) and rs27072 polymorphisms of DAT1. Age at initiation was assessed at age 15 and 19 years. Information about current alcohol and tobacco consumption was obtained at age 19 years using self-report measures and structured interviews. Results suggest that age at onset of intensive consumption moderated the association of the DAT1 gene with early adult substance use and dependence, revealing a DAT1 effect only among individuals homozygous for the 10r allele of the 40-bp VNTR who had started daily smoking or being intoxicated early in life. Equally, carriers of the T allele of the rs27072 polymorphism reporting an early age at first intoxication showed higher current alcohol consumption at age 19 years. In contrast, no interaction between rs27072 and the age at first cigarette with regard to later smoking was observed. These findings provide evidence that the DAT1 gene interacts with an early heavy or regular drug exposure of the maturing adolescent brain to predict substance (ab)use in young adulthood. Further studies are required to confirm these findings.
Es werden Befunde aus einer prospektiven Laengsschnittstudie praesentiert, in der 321 Probanden im Alter von 8, 13, 18 und 25 Jahren untersucht werden konnten; ihre Dunkelfelddelinquenz wurde mit 18 und 25 Jahren erfasst. Wir suchten nach Assoziationen zur Delinquenzentwicklung und erwarteten Unterschiede zwischen auf das Jugendalter beschraenkter gegenueber ins fruehe Erwachsenenalter fortgesetzter sowie spaet, d.h. nach dem Alter von 18 Jahren, beginnender Delinquenz. Wir fanden gemeinsame Risikofaktoren und fuer die drei Verlaufstypen spezifische Risikokonstellationen, die eher im Jugendalter als in der Kindheit identifiziert wurden. Widrige familiaere Bedingungen, Entwicklungsverzoegerungen und psychische Stoerungen scheinen mit Delinquenz als eher persistentem Verhalten assoziiert.