Missing data in alcohol clinical trials: a comparison of methods

BACKGROUND

The rate of participant attrition in alcohol clinical trials is often substantial and can cause significant issues with regard to the handling of missing data in statistical analyses of treatment effects. It is common for researchers to assume that missing data is indicative of participant relapse, and under that assumption, many researchers have relied on setting all missing values to the worst-case scenario for the outcome (e.g., missing = heavy drinking). This sort of single-imputation method has been criticized for producing biased results in other areas of clinical research, but has not been evaluated within the context of alcohol clinical trials, and many alcohol researchers continue to use the missing = heavy drinking assumption.

METHODS

Data from the COMBINE study, a multisite randomized clinical trial, were used to generate simulated situations of missing data under a variety of conditions and assumptions. We manipulated the sample size (n = 200, 500, and 1,000) and dropout rate (5, 10, 25, 30%) under 3 missing data assumptions (missing completely at random, missing at random, and missing not at random). We then examined the association between receiving naltrexone and heavy drinking during the first 10 weeks following treatment using 5 methods for treating missing data (complete case analysis [CCA], last observation carried forward [LOCF], missing = heavy drinking, multiple imputation [MI], and full information maximum likelihood [FIML]).

RESULTS

CCA, LOCF, and missing = heavy drinking produced the most biased naltrexone effect estimates and standard errors under conditions that are likely to exist in randomized clinical trials. MI and FIML produced the least biased naltrexone effect estimates and standard errors.

CONCLUSIONS

Assuming that missing = heavy drinking produces biased results of the treatment effect and should not be used to evaluate treatment effects in alcohol clinical trials.

Response-effect compatibility defines the natural scrolling direction

OBJECTIVE

We evaluated alternative scrolling methods on non-touch screen computer operating systems by comparing human performance in different scrolling conditions.

BACKGROUND

The scrolling directions on current operating systems are discrepant. Few researchers have investigated how scrolling method influences users performance. The response-effect (R-E) compatibility principle can be used as a theoretical guide.

METHOD

Experiments 1 and 2 involved two successive tasks (scrolling and target content judgment) to simulate how people scroll to acquire and use off-screen information. Performance in R-E compatible and incompatible conditions was compared. Experiment 3 involved a location judgment task to test the influence of target location. Experiments 4 and 5 included a scrolling effect following the location judgment task to test the sufficient role of the scrolling effect.

RESULTS

Overall, responses were facilitated when the response direction was compatible with the forthcoming display-content movement direction (an R-E compatibility effect), when the scrolling effect was task relevant or task irrelevant. A spatial stimulus-response (S-R) compatibility effect attributable to target location was also found. When the scrolling effect was present, there were both R-E and S-R components; the R-E effect was the larger of the two.

CONCLUSION

Scrolling in the direction of content movement yielded the best performance, and the scrolling effect was the main source of the R-E compatibility effect.

APPLICATION

These findings suggest that (a) the R-E compatibility principle may be used as a general design guideline for scrolling and (b) a consistent scrolling method should be available on various operating systems.

Poverty's latent effect on adiposity during childhood: evidence from a Québec birth cohort

BACKGROUND

Childhood poverty heightens the risk of obesity in adulthood, but the age at which this risk appears is unclear. We analysed the association between poverty trajectories with body mass index (BMI) Z-scores or the risk of being overweight or obese across four ages (6 years, 8 years, 10 years and 12 years) in childhood.

METHODS

Data were from the 1998-2010 'Quebec Longitudinal Study of Child Development' cohort (n=698). Poverty was defined using Statistics Canada's thresholds, and trajectories were characterised with a Latent Class Growth Analysis. Multivariable linear and logistic regression models adjusted for sex, whether the mother was an immigrant, maternal education and birth weight.

RESULTS

Four income trajectories were identified: a reference group (stable non-poor), and 3 higher exposure categories (increasing likelihood of poverty, decreasing likelihood of poverty or stable poor). Compared with children from stable non-poor households, children from stable poor households had BMI Z-scores that were 0.39 and 0.43 larger than children from stable non-poor households at age 10 years and 12 years, respectively (p<0.05). Compared with children from stable non-poor households, children from stable poor households were 2.22, 2.34, and 3.04 times more likely to be overweight or obese at age 8 years, 10 years and 12 years, respectively (p<0.05).

CONCLUSION

A latency period for the detrimental effects of child poverty on the risk of overweight or obesity was detected. Whether the effects continue to widen with increasing duration of exposure to poverty as the children age should be investigated.

Bridges self-management program for people with stroke in the community: A feasibility randomized controlled trial

BACKGROUND

Enabling self-management behaviors is considered important in order to develop coping strategies and confidence for managing life with a long-term condition. However, there is limited research into stroke-specific self-management interventions.

AIM

The aim of this randomized controlled trial was to evaluate the feasibility of delivering the Bridges stroke self-management program in addition to usual stroke rehabilitation compared with usual rehabilitation only.

METHODS

Participants recruited from the referrals to a community stroke team were randomly allocated to the Bridges stroke self-management program, receiving either one session of up to one-hour per week over a six-week period in addition to usual stroke rehabilitation, or usual rehabilitation only. Feasibility was measured using a range of methods to determine recruitment and retention; adherence to the program; suitability and variability of outcome measures used; application and fidelity of the program; and acceptability of the program to patients, carers and professionals.

RESULTS

Twenty-five people were recruited to the study over a 13-month period. Eight out of the 12 participants in the Bridges stroke self-management program received all six sessions; there was one withdrawal from the study. There were changes in outcomes between the two groups. Participants who received the Bridges stroke self-management program appeared to have a greater change in self-efficacy, functional activity, social integration and quality of life over the six-week intervention period and showed less decline in mood and quality of life at the three-month follow-up. Professionals found the program acceptable to use in practice, and feedback from participants was broadly positive.

CONCLUSIONS

The findings from this study appear promising, but questions remain regarding the feasibility of delivering the Bridges stroke self-management program in addition to usual rehabilitation. The dose response of receiving the program cannot be ruled out, and the next stage of research should explore the feasibility of an integrated program. Exploration of the reasons behind relatively low recruitment and of the sensitivity of outcome measures to detect a change are also required. Additional investigation of intervention fidelity is required to monitor if the program is being delivered as intended.

To create or to recall? Neural mechanisms underlying the generation of creative new ideas

This fMRI study investigated brain activation during creative idea generation using a novel approach allowing spontaneous self-paced generation and expression of ideas. Specifically, we addressed the fundamental question of what brain processes are relevant for the generation of genuinely new creative ideas, in contrast to the mere recollection of old ideas from memory. In general, creative idea generation (i.e., divergent thinking) was associated with extended activations in the left prefrontal cortex and the right medial temporal lobe, and with deactivation of the right temporoparietal junction. The generation of new ideas, as opposed to the retrieval of old ideas, was associated with stronger activation in the left inferior parietal cortex which is known to be involved in mental simulation, imagining, and future thought. Moreover, brain activation in the orbital part of the inferior frontal gyrus was found to increase as a function of the creativity (i.e., originality and appropriateness) of ideas pointing to the role of executive processes for overcoming dominant but uncreative responses. We conclude that the process of idea generation can be generally understood as a state of focused internally-directed attention involving controlled semantic retrieval. Moreover, left inferior parietal cortex and left prefrontal regions may subserve the flexible integration of previous knowledge for the construction of new and creative ideas.

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Functional imaging was performed during spontaneous self-paced idea generation.

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Overt responses were recorded and evaluated for novelty and creativity.

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Brain activation of newly created and recalled ideas was compared.

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The generation of new ideas involved stronger activation of the left IPC.

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Creativity of ideas was related to activation of the left IFG.

Evolutionary relevance facilitates visual information processing

Visual search of the environment is a fundamental human behavior that perceptual load affects powerfully. Previously investigated means for overcoming the inhibitions of high perceptual load, however, generalize poorly to real-world human behavior. We hypothesized that humans would process evolutionarily relevant stimuli more efficiently than evolutionarily novel stimuli, and evolutionary relevance would mitigate the repercussions of high perceptual load during visual search. Animacy is a significant component to evolutionary relevance of visual stimuli because perceiving animate entities is time-sensitive in ways that pose significant evolutionary consequences. Participants completing a visual search task located evolutionarily relevant and animate objects fastest and with the least impact of high perceptual load. Evolutionarily novel and inanimate objects were located slowest and with the highest impact of perceptual load. Evolutionary relevance may importantly affect everyday visual information processing.

The ex-Gaussian distribution of reaction times in adolescents with attention-deficit/hyperactivity disorder

We investigated the three parameters (mu, sigma, tau) of ex-Gaussian distribution of RT derived from the Conners' continuous performance test (CCPT) and examined the moderating effects of the energetic factors (the inter-stimulus intervals (ISIs) and Blocks) among these three parameters, especially tau, an index describing the positive skew of RT distribution. We assessed 195 adolescents with DSM-IV ADHD, and 90 typically developing (TD) adolescents, aged 10-16. Participants and their parents received psychiatric interviews to confirm the diagnosis of ADHD and other psychiatric disorders. Participants also received intelligence (WISC-III) and CCPT assessments. We found that participants with ADHD had a smaller mu, and larger tau. As the ISI/Block increased, the magnitude of group difference in tau increased. Among the three ex-Gaussian parameters, tau was positively associated with omission errors, and mu was negatively associated with commission errors. The moderating effects of ISIs and Blocks on tau parameters suggested that the ex-Gaussian parameters could offer more information about the attention state in vigilance task, especially in ADHD.

Risk factors of significant pain syndrome 90 days after minor thoracic injury: trajectory analysis

OBJECTIVES

The objective was to identify the risk factors of clinically significant pain at 90 days in patients with minor thoracic injury (MTI) discharged from the emergency department (ED).

METHODS

A prospective, multicenter, cohort study was conducted in four Canadian EDs from November 2006 to November 2010. All consecutive patients aged 16 years or older with MTI were eligible at discharge from EDs. They underwent standardized clinical and radiologic evaluations at 1 and 2 weeks, followed by standardized telephone interviews at 30 and 90 days. A pain trajectory model characterized groups of patients with different pain evolutions and ascertained specific risk factors in each group through multivariate analysis.

RESULTS

In this cohort of 1,132 patients, 734 were eligible for study inclusion. The authors identified a pain trajectory that characterized 18.2% of the study population experiencing clinically significant pain (>3 of 10) at 90 days after a MTI. Multivariate modeling found two or more rib fractures, smoking, and initial oxygen saturation below 95% to be predictors of this group of patients.

CONCLUSIONS

To the authors' knowledge, this is the first prospective study of trajectory modeling to detect risk factors associated with significant pain at 90 days after MTI. These factors may help in planning specific treatment strategies and should be validated in another prospective cohort.

Self-Induced Attentional Blink

Satisfaction of search (which we refer to as subsequent search misses)—a decrease in accuracy at detecting a second target after a first target has been found in a visual search—underlies real-world search errors (e.g., tumors may be missed in an X-ray if another tumor already has been found), but little is known about this phenomenon’s cognitive underpinnings. In the present study, we examined subsequent search misses in terms of another, more extensively studied phenomenon: the attentional blink, a decrease in accuracy when a second target appears 200 to 500 ms after a first target is detected in a temporal stream. Participants searched for T-shaped targets among L-shaped distractors in a spatial visual search, and despite large methodological differences between self-paced spatial visual searches and attentional blink tasks, an attentional-blink-like effect accounted for subsequent-search-miss errors. This finding provides evidence that accuracy is negatively affected shortly after a first target is fixated in a self-paced, self-guided visual search.

Home and health in people ageing with Parkinson's disease: study protocol for a prospective longitudinal cohort survey study

BACKGROUND

With an increased life expectancy for the general population as well as for those ageing with chronic diseases, there are major challenges to the affected individuals and their families, but also to health care and societal planning. Most important, an increasing proportion of older people remain living in their ordinary homes despite health decline and disability. However, little is known about the home and health situation of people ageing with Parkinson's disease (PD), and older people are often excluded from PD-research.

METHODS/DESIGN

The overall aim of the present project is to generate knowledge on home and health dynamics in people with PD, with an explicit attention to PD-specific symptomatology. We will concentrate on aspects of home and health captured by state-of-the-art methodology from gerontology as well as PD-research, health science and rehabilitation. This study protocol describes a longitudinal cohort survey study that includes a baseline data collection and a 3-year follow-up. Both data collection waves include self-administered questionnaires, structured interviews, clinical assessments and observations during home visits effectuated by research staff with project-specific training. In order to arrive at a follow-up sample of N=160, 250 participants identified by PD specialist nurses are being recruited from three hospitals in southern Sweden. With no lower or upper age limit, only those diagnosed with PD since at least one year were included. The exclusion criteria were: difficulties in understanding or speaking Swedish and/or cognitive difficulties/other reasons making the individual unable to give informed consent or to take part in the majority of the data collection. The data collection targets environmental factors such as assistive devices, social support, physical environmental barriers, accessibility problems and perceived aspects of home. A broad variety of instruments tap PD-specific problems (e.g. freezing of gait, fear of falling) and health-related issues such as general self-efficacy, body functions, activities and participation.

DISCUSSION

This project will produce knowledge to the benefit of the development of health care and societal planning that targets people ageing with PD, ultimately promoting activity and participation and an increase of the number of healthy life years for this sub-group of the population.

Exogenous orienting of crossmodal attention in 3-D space: support for a depth-aware crossmodal attentional system

The aim of the present study was to investigate exogenous crossmodal orienting of attention in three-dimensional (3-D) space. Most studies in which the orienting of attention has been examined in 3-D space concerned either exogenous intramodal or endogenous crossmodal attention. Evidence for exogenous crossmodal orienting of attention in depth is lacking. Endogenous and exogenous attention are behaviorally different, suggesting that they are two different mechanisms. We used the orthogonal spatial-cueing paradigm and presented auditory exogenous cues at one of four possible locations in near or far space before the onset of a visual target. Cues could be presented at the same (valid) or at a different (invalid) depth from the target (radial validity), and on the same (valid) or on a different (invalid) side (horizontal validity), whereas we blocked the depth at which visual targets were presented. Next to an overall validity effect (valid RTs < invalid RTs) in horizontal space, we observed an interaction between the horizontal and radial validity of the cue: The horizontal validity effect was present only when the cue and the target were presented at the same depth. No horizontal validity effect was observed when the cue and the target were presented at different depths. These results suggest that exogenous crossmodal attention is "depth-aware," and they are discussed in the context of the supramodal hypothesis of attention.

Neither separate nor equivalent: relationships between feature representations within bound objects

Evidence suggests that binding, or encoding a feature with respect to other features in time and space, can convey cognitive advantages. However, evidence across many kinds of stimuli and paradigms presents a mixed picture, alternatively showing cognitive costs or cognitive advantages associated with maintaining bound representations. We examined memory for colored letters drawn from similar and distinct color sets under circumstances that encouraged or discouraged the maintenance of color-letter binding. Our results confirmed previous change recognition research showing feature recognition improvement under explicit instructions to maintain binding. Color memory improved during binding, showing a reduced detrimental effect of feature similarity on retrieval, particularly when the letter served as the retrieval cue for a letter-color object. We found that feature recognition improved when two conditions were met: 1) relationships between features were to-be-remembered, and 2) the feature conjunction was relevant at test. Our results further suggest that this feature advantage arises because the encoded relationship between the features facilitates retrieval, not because features and objects are represented simultaneously in separate buffers.

Avoiding the problem state bottleneck by strategic use of the environment

We investigated whether environmental support can be used to circumvent the problem state bottleneck in human multitasking. Previously, it was shown that people can only maintain a single chunk of information in their problem state resource, the central part of working memory. Consequently, when the problem state resource was required by multiple tasks concurrently, performance decreased. This phenomenon was termed the problem state bottleneck. To investigate whether the environment can be used to circumvent this bottleneck, we conducted an experiment with two main conditions. In the No-Support condition we replicated an earlier experiment that indicated the existence of the problem state bottleneck. In the Support condition we presented external cues, reducing the load on the problem state resource. To support the results of the experiment we present a computational cognitive model. The experiment and model indicated that the problem state bottleneck can be avoided by using external cues. However, subjects only used external cues when this led to faster behavior. These results were interpreted in the light of the Soft Constraints Hypothesis, which states that humans always follow the fastest strategy possible, as opposed to the most accurate strategy.

Rapid visuomotor processing of phobic images in spider- and snake-fearful participants

This study investigates enhanced visuomotor processing of phobic compared to fear-relevant and neutral stimuli. We used a response priming design to measure rapid, automatic motor activation by natural images (spiders, snakes, mushrooms, and flowers) in spider-fearful, snake-fearful, and control participants. We found strong priming effects in all tasks and conditions; however, results showed marked differences between groups. Most importantly, in the group of spider-fearful individuals, spider pictures had a strong and specific influence on even the fastest motor responses: Phobic primes entailed the largest priming effects, and phobic targets accelerated responses, both effects indicating speeded response activation by phobic images. In snake-fearful participants, this processing enhancement for phobic material was less pronounced and extended to both snake and spider images. We conclude that spider phobia leads to enhanced processing capacity for phobic images. We argue that this is enabled by long-term perceptual learning processes.

Longitudinal trajectories of suicidal ideation and subsequent suicide attempts among adolescent inpatients

A period of particularly high risk for suicide attempts among adolescent inpatients is within 12 months after discharge. However, little is known about longitudinal trajectories of suicidal ideation in this high-risk group and how these relate to posthospitalization suicide attempts and rehospitalizations. Our objectives were to identify these trajectories and examine their relationships with posthospitalization psychiatric crises. We also examined predictors of trajectory group membership. Participants (N = 376; ages 13-17; 72% female) were assessed at hospitalization and 3, 6, and 12 months later. Trajectory groups, and their predictors, were identified with latent class growth modeling. We used logistic regression to examine associations between trajectory groups and likelihood of suicide attempts and rehospitalization, controlling for attempt history. Three trajectory groups were identified: (a) subclinical ideators (31.6%), (b) elevated ideators with rapidly declining ideation (57.4%), and (c) chronically elevated ideators (10.9%). Adolescents in the chronically elevated ideation group had 2.29, confidence interval (CI) [1.08, 4.85], p = .03, and 4.15, CI [1.65, 10.44], p < .01, greater odds of attempting suicide and 3.23, CI [1.37, 7.69], p = .01, and 11.20, CI [4.33, 29.01], p < .001, greater odds of rehospitalization relative to rapidly declining and subclinical groups, respectively. Higher baseline hopelessness was associated with persisting suicidal ideation. Results suggest that suicidal ideation severity at hospitalization may not be an adequate marker for subsequent suicidal crises. It is important to identify adolescents vulnerable to persisting suicidal ideation, as they are at highest risk of psychiatric crises. Addressing hopelessness may facilitate faster declines in ideation after hospitalization. Results also highlight a need for consistent monitoring of these adolescents' suicidal ideation after discharge.

Learning to Tie Well with Others

A shoe-tying paradigm was developed to examine mode effects and motor learning functions when people are asked to handle a familiar object (e.g., tying a shoe) using an unfamiliar coordination mode (e.g., tying a shoe with another person). Dyads first tied a shoe apparatus using their own two hands (“bimanual”) for 10 trials and then tied the shoe as a dyad, each person using one hand (“intermanual”) for 20 trials. Finally, participants tied the shoe bimanually for another 10 trials. Previous research has indicated that intermanual is faster than bimanual, but those experiments examined novel tasks performed by novices. For this familiar task, results revealed that participants were significantly slower in the intermanual mode compared to either set of bimanual trials, and participants were significantly faster in the second set of bimanual trials than the first. Unlike mode effects for novel tasks with novice participants, the intermanual mode was slowest, though intermanual performance may have enhanced subsequent bimanual performance. Previous research on motor learning suggests an exponential function describes acquisition of a novel skill, whereas a power law describes persistent motor learning. Analyses revealed that dyads exhibited a power law function over both the first set of bimanual trials and the intermanual trials. That finding suggests that participants were not learning a new coordination skill in the intermanual mode but may have transferred persistent, bimanual shoe-tying skill to the novel mode. Theoretical and practical implications of acquisition of a novel coordination mode for a familiar task are described.

Providing conversation partners views of the driving scene mitigates cell phone-related distraction

Cognitively demanding cell phone conversations impair driving performance. In some situations, conversations with a passenger are less disruptive than cell phone conversations, in theory because of heightened situational awareness. Here, drivers completed challenging freeway drives in a high-fidelity simulator while conversing with a partner. The pairs engaged in naturalistic conversations in three different conditions: remotely on a hands-free phone, as a passenger in the vehicle, and in a videophone condition where the hands-free phone experience was enhanced by a live video the driving scene and the driver’s face. This condition was designed to increase the conversation partner’s awareness of the driving situation to a level similar to that of an in-vehicle passenger, to test our hypothesis that this cognizance leads to less distracted driving. We compared these conversation conditions to a driving-alone condition. Drivers were involved in more collisions with merging vehicles in the phone condition compared to drive-alone, passenger or videophone conditions, and crucially there was no difference in collisions between the passenger and videophone conditions. Providing remote conversation partner information about the driver and driving scene reduces the detrimental effect of cell phone conversations, possibly by increasing shared situational awareness.

Contribution of the Japan International Cooperation Agency health-related projects to health system strengthening

Background

The Japan International Cooperation Agency (JICA) has focused its attention on appraising health development assistance projects and redirecting efforts towards health system strengthening. This study aimed to describe the type of project and targets of interest, and assess the contribution of JICA health-related projects to strengthening health systems worldwide.

Methods

We collected a web-based Project Design Matrix (PDM) of 105 JICA projects implemented between January 2005 and December 2009. We developed an analytical matrix based on the World Health Organization (WHO) health system framework to examine the PDM data and thereby assess the projects’ contributions to health system strengthening.

Results

The majority of JICA projects had prioritized workforce development, and improvements in governance and service delivery. Conversely, there was little assistance for finance or medical product development. The vast majority (87.6%) of JICA projects addressed public health issues, for example programs to improve maternal and child health, and the prevention and treatment of infectious diseases such as AIDS, tuberculosis and malaria. Nearly 90% of JICA technical healthcare assistance directly focused on improving governance as the most critical means of accomplishing its goals.

Conclusions

Our study confirmed that JICA projects met the goals of bilateral cooperation by developing workforce capacity and governance. Nevertheless, our findings suggest that JICA assistance could be used to support financial aspects of healthcare systems, which is an area of increasing concern. We also showed that the analytical matrix methodology is an effective means of examining the component of health system strengthening to which the activity and output of a project contributes. This may help policy makers and practitioners focus future projects on priority areas.

Stimulus-specific enhancement of fear extinction during slow-wave sleep

Sleep can strengthen memory for emotional information, but whether emotional memories can be specifically targeted and modified during sleep is unknown. In human subjects who underwent olfactory contextual fear conditioning, re-exposure to the odorant context in slow-wave sleep promoted stimulus-specific fear extinction, with parallel reductions of hippocampal activity and reorganization of amygdala ensemble patterns. Fear extinction may thus be selectively enhanced during sleep, even without re-exposure to the feared stimulus itself.

Trial-by-trial updating of an internal reference in discrimination tasks: evidence from effects of stimulus order and trial sequence

In psychophysics, participants are often asked to discriminate between a constant standard and a variable comparison. Previous studies have shown that discrimination performance is better when the comparison follows, rather than precedes, the standard. Prominent difference models of psychophysics and decision making cannot easily explain this order effect. However, a simple extension of this model class involving dynamical updating of an internal reference accounts for this order effect. In addition, this Internal Reference Model (IRM) predicts sequential response effects. We examined the predictions of IRM in two duration discrimination experiments. The obtained results are in agreement with the predictions of IRM, suggesting that participants update their internal reference on every trial. Additional simulations show that IRM also accounts for the negative sequential effects observed in single-stimulus paradigms.

E-readers are more effective than paper for some with dyslexia

E-readers are fast rivaling print as a dominant method for reading. Because they offer accessibility options that are impossible in print, they are potentially beneficial for those with impairments, such as dyslexia. Yet, little is known about how the use of these devices influences reading in those who struggle. Here, we observe reading comprehension and speed in 103 high school students with dyslexia. Reading on paper was compared with reading on a small handheld e-reader device, formatted to display few words per line. We found that use of the device significantly improved speed and comprehension, when compared with traditional presentations on paper for specific subsets of these individuals: Those who struggled most with phoneme decoding or efficient sight word reading read more rapidly using the device, and those with limited VA Spans gained in comprehension. Prior eye tracking studies demonstrated that short lines facilitate reading in dyslexia, suggesting that it is the use of short lines (and not the device per se) that leads to the observed benefits. We propose that these findings may be understood as a consequence of visual attention deficits, in some with dyslexia, that make it difficult to allocate attention to uncrowded text near fixation, as the gaze advances during reading. Short lines ameliorate this by guiding attention to the uncrowded span.

A test of the cognitive self-medication hypothesis of tobacco smoking in schizophrenia

BACKGROUND

Heavier tobacco smoking among people with schizophrenia (SCZ) has been suggested to reflect self-medication of cognitive deficits. The idea that cognitive-enhancing effects of nicotine are a primary motivator of tobacco consumption in SCZ and that abstinence would deprive SCZ of such beneficial effects might explain hesitation among providers to pursue smoking cessation in SCZ. This study tested predictions of the cognitive self-medication hypothesis.

METHODS

In three counterbalanced sessions, 17 SCZ and 17 healthy control subjects (HCS), all smokers, were tested under ad libitum smoking or 3.5 hours after abstaining and receiving a nicotine (14 mg/24 hours) or placebo patch.

RESULTS

Attention task performance was improved by transdermal nicotine relative to placebo, with intermediate performance by ad libitum smoking. These effects were of similar size in SCZ and HCS and did not reflect remediation of functions disproportionately impaired in SCZ. Although more SCZ reported that the need to concentrate influenced their smoking, this was not reflected by the actual behavior of these patients. Self-reported ability to concentrate changed with nicotine status in HCS but not SCZ, suggesting insensitivity of SCZ to nicotine-derived performance benefits. Nicotine plasma concentrations after ad libitum smoking were not associated with performance benefits but instead with the propensity to experience nicotine withdrawal upon abstinence. This association was seen selectively in SCZ, suggesting a possible reason for heavier smoking.

CONCLUSIONS

These findings suggest that subjective or objective attentional benefits are unlikely the primary driving force of tobacco consumption in SCZ and should not discourage providers from supporting quit attempts.

Developmental trajectories of romantic stages and associations with problem behaviours during adolescence

Normative romantic development is theorized to progress through a series of stages: affiliative activities, group-based dating, and romantic relationships. The objectives of this research were threefold: empirically examine this progression of romantic stages during adolescence, determine normative and atypical trajectories, and examine links with internalizing and externalizing symptoms. An eight-wave longitudinal study was conducted with 698 adolescents (53.6% female; M(age) = 11.8 years at start of study). A group-based trajectory approach was employed to identify prototypical trajectories of romantic development and a model with three distinct romantic trajectories (i.e., On-time, Early Starters and Late Bloomers) was identified. Both timing and sequencing of romantic activity differed among trajectory groups. Analysis of Variance (ANOVAs) identified associations between Early Starters and externalizing behaviours in early, middle and later adolescence. The findings support progression through theorized stages of romantic activity and highlight the problems that are linked to early-starting and non-sequenced romantic development.

The relationship between visual working memory and attention: retention of precise colour information in the absence of effects on perceptual selection

We examined the conditions under which a feature value in visual working memory (VWM) recruits visual attention to matching stimuli. Previous work has suggested that VWM supports two qualitatively different states of representation: an active state that interacts with perceptual selection and a passive (or accessory) state that does not. An alternative hypothesis is that VWM supports a single form of representation, with the precision of feature memory controlling whether or not the representation interacts with perceptual selection. The results of three experiments supported the dual-state hypothesis. We established conditions under which participants retained a relatively precise representation of a parcticular colour. If the colour was immediately task relevant, it reliably recruited attention to matching stimuli. However, if the colour was not immediately task relevant, it failed to interact with perceptual selection. Feature maintenance in VWM is not necessarily equivalent with feature-based attentional selection.

Behavioural coordination of dogs in a cooperative problem-solving task with a conspecific and a human partner

The process of domestication has arguably provided dogs (Canis familiaris) with decreased emotional reactivity (reduced fear and aggression) and increased socio-cognitive skills adaptive for living with humans. It has been suggested that dogs are uniquely equipped with abilities that have been identified as crucial in cooperative problem-solving, namely social tolerance and the ability to attend to other individuals’ behaviour. Accordingly, dogs might be hypothesised to perform well in tasks in which they have to work together with a human partner. Recently, researchers have found that dogs successfully solved a simple cooperative task with another dog. Due to the simplicity of the task, this study was, however, unable to provide clear evidence as to whether the dogs’ successful performance was based on the cognitive ability of behavioural coordination, namely the capacity to link task requirements to the necessity of adjusting one’s actions to the partner’s behaviour. Here, we tested dogs with the most commonly used cooperative task, appropriate to test behavioural coordination. In addition, we paired dogs with both a conspecific and a human partner. Although dogs had difficulties in inhibiting the necessary action when required to wait for their partner, they successfully attended to the two cues that predicted a successful outcome, namely their partner’s behaviour and the incremental movement of rewards towards themselves. This behavioural coordination was shown with both a conspecific and a human partner, in line with the recent findings suggesting that dogs exhibit highly developed socio-cognitive skills in interactions with both humans and other dogs.

Young adult weight trajectories through midlife by body mass category

OBJECTIVE

To estimate the expected weight gain through midlife for those in a given BMI category in young adulthood.

DESIGN AND METHODS

Group-based trajectory modeling and National Longitudinal Survey of Youth 1979 data from 1990 to 2008 were used to quantify weight trajectories through midlife for 10,038 young adult men and women stratified by BMI category. Logistic regression was used to assess the association of trajectory membership with obesity-related conditions (hypertension, diabetes, arthritis) in middle age.

RESULTS

Annual weight gain averaged 0.53 kg (1.17 lb) across the entire sample. However, there was considerable variation by and within BMI categories. More than 98% of men and 92% of women were on upward-sloping trajectories, generally moving into a higher BMI category by middle age. Those who experienced early and rapid weight gain during young adulthood were most likely to be on a steeper trajectory and had greater risks for obesity-related conditions.

CONCLUSION

This study points to the health and weight benefits of entering young adulthood with a normal BMI, but further reveals that this is no guarantee of maintaining a healthy weight through midlife. For those who are young adults today, weight maintenance is unlikely to occur without significant environmental or technical innovation.

Attention-modulated alpha-band oscillations protect against intrusion of irrelevant information

Combining high-density scalp EEG recordings with a sensitive analog measure of STM's fidelity, we characterized the temporal dynamics of intentional ignoring and related those dynamics to the intrusion of task-irrelevant information. On each trial of the task, two study Gabors were briefly presented in succession. A green or red disc preceding each Gabor signified whether that Gabor should be remembered or ignored, respectively. With cue-stimulus intervals of 300, 600, or 900 msec presented in separate sessions, we found that the onset of posterior, prestimulus alpha oscillations varied with the length of the interval. Although stimulus onset time was entirely predictable, the longer the cue-stimulus interval, the earlier the increase in prestimulus alpha power. However, the alpha-band modulation was not simply locked to the cue offset. The temporal envelopes of posterior alpha-band modulation were strikingly similar for both cued attending and cued ignoring and differed only in magnitude. This similarity suggests that cued attending includes suppression of task-irrelevant, spatial processing. Supporting the view that alpha-band oscillations represent inhibition, our graded measure of recall revealed that, when the stimulus to be ignored appears second in the sequence, peristimulus alpha power predicted the degree to which that irrelevant stimulus distorted subsequent recall of the stimulus that was to be remembered. These results demonstrate that timely deployment of attention-related alpha-band oscillations can aid STM by filtering out task-irrelevant information.

Neuropsychological, clinical and cognitive insight predictors of outcome in a first episode psychosis study

The outcome of first episode psychosis (FEP) is highly variable and difficult to predict. We studied prospectively the impact of poor insight and neuropsychological deficits on outcomes in a longitudinal cohort of 127 FEP patients. Participants were assessed on 5 domains of cognitive function and 2 domains of insight (clinical and cognitive). At 12 months, patients were assessed again for symptom severity and psychosocial function. Regression analyses revealed that cognitive insight (a measure of self-reflectiveness and self-certainty) was the best baseline predictor of overall psychopathology at 12 months whereas executive function performance at admission to the study indicated later severity of negative symptoms. Other neuropsychological and insight measures were poor predictors of psychosocial function at 1 year. The results suggest that specific neuropsychological and insight factors have separate predictive capacities indicating that they are distinct psychological processes in psychosis. Cognitive insight proved to be a useful prognostic indicator, and should be considered for future studies and as a potential focus for treatment.

Language can boost otherwise unseen objects into visual awareness

Linguistic labels (e.g., "chair") seem to activate visual properties of the objects to which they refer. Here we investigated whether language-based activation of visual representations can affect the ability to simply detect the presence of an object. We used continuous flash suppression to suppress visual awareness of familiar objects while they were continuously presented to one eye. Participants made simple detection decisions, indicating whether they saw any image. Hearing a verbal label before the simple detection task changed performance relative to an uninformative cue baseline. Valid labels improved performance relative to no-label baseline trials. Invalid labels decreased performance. Labels affected both sensitivity (d') and response times. In addition, we found that the effectiveness of labels varied predictably as a function of the match between the shape of the stimulus and the shape denoted by the label. Together, the findings suggest that facilitated detection of invisible objects due to language occurs at a perceptual rather than semantic locus. We hypothesize that when information associated with verbal labels matches stimulus-driven activity, language can provide a boost to perception, propelling an otherwise invisible image into awareness.

Slow angled-descent forepaw grasping (SLAG): an innate behavioral task for identification of individual experimental mice possessing functional vision

Background

There is significant interest in the generation of improved assays to clearly identify experimental mice possessing functional vision, a property that could qualify mice for inclusion in behavioral and neuroscience studies. Widely employed current methods rely on mouse responses to visual cues in assays of reflexes, depth perception, or cognitive memory. However, commonly assessed mouse reflexes can sometimes be ambiguous in their expression, while depth perception assays are sometimes confounded by variation in anxiety responses and exploratory conduct. Furthermore, in situations where experimental groups vary in their cognitive memory capacity, memory assays may not be ideal for assessing differences in vision.

Results

We have optimized a non-invasive behavioral assay that relies on an untrained, innate response to identify individual experimental mice possessing functional vision: slow angled-descent forepaw grasping (SLAG). First, we verified that SLAG performance depends on vision and not olfaction. Next, all members of an age-ranged cohort of 158 C57BL/6 mice (57 wild-type, 101 knockout, age range 44–241 days) were assessed for functional vision using the SLAG test without training or conditioning. Subjecting the population to a second innate behavioral test, Dark Chamber preference, corroborated that the functional vision assessment of SLAG was valid.

Conclusions

We propose that the SLAG assay is immediately useful to quickly and clearly identify experimental mice possessing functional vision. SLAG is based on a behavioral readout with a significant innate component with no requirement for training. This will facilitate the selection of mice of known sighted status in vision-dependent experiments that focus on other types of behavior, neuroscience, and/or cognitive memory.

Can monitoring in language comprehension in Autism Spectrum Disorder be modulated? Evidence from event-related potentials

The present study examined language comprehension in Autism Spectrum Disorder (ASD) in light of monitoring. It was studied whether individuals with ASD monitor their language perception, and whether monitoring during language perception could be modulated with instructions. We presented higher-level (semantic) linguistic violations and lower-level (orthographic) linguistic violations in a free reading condition and in an instructed condition, recording event-related potentials. For control participants, a monitoring response as tapped by the P600 effect was found to semantically and orthographically incorrect input in both conditions. For participants with ASD, however, a monitoring response to semantically implausible input, tapped by the P600, was found only in the instructed condition. For orthographic errors monitoring was observed both in the free reading and in the instructed condition. This suggests that people with ASD are less inclined than typical individuals to monitor their perception of higher-level linguistic input, but that this can be enhanced with instructions.

Shorter lines facilitate reading in those who struggle

People with dyslexia, who ordinarily struggle to read, sometimes remark that reading is easier when e-readers are used. Here, we used eye tracking to observe high school students with dyslexia as they read using these devices. Among the factors investigated, we found that reading using a small device resulted in substantial benefits, improving reading speeds by 27%, reducing the number of fixations by 11%, and importantly, reducing the number of regressive saccades by more than a factor of 2, with no cost to comprehension. Given that an expected trade-off between horizontal and vertical regression was not observed when line lengths were altered, we speculate that these effects occur because sluggish attention spreads perception to the left as the gaze shifts during reading. Short lines eliminate crowded text to the left, reducing regression. The effects of attention modulation by the hand, and of increased letter spacing to reduce crowding, were also found to modulate the oculomotor dynamics in reading, but whether these factors resulted in benefits or costs depended on characteristics, such as visual attention span, that varied within our sample.

The emergence of semantic meaning in the ventral temporal pathway

In the ventral visual pathway, early visual areas encode light patterns on the retina in terms of image properties, for example, edges and color, whereas higher areas encode visual information in terms of objects and categories. At what point does semantic knowledge, as instantiated in human language, emerge? We examined this question by studying whether semantic similarity in language relates to the brain's organization of object representations in inferior temporal cortex (ITC), an area of the brain at the crux of several proposals describing how the brain might represent conceptual knowledge. Semantic relationships among words can be viewed as a geometrical structure with some pairs of words close in their meaning (e.g., man and boy) and other pairs more distant (e.g., man and tomato). ITC's representation of objects similarly can be viewed as a complex structure with some pairs of stimuli evoking similar patterns of activation (e.g., man and boy) and other pairs evoking very different patterns (e.g., man and tomato). In this study, we examined whether the geometry of visual object representations in ITC bears a correspondence to the geometry of semantic relationships between word labels used to describe the objects. We compared ITC's representation to semantic structure, evaluated by explicit ratings of semantic similarity and by five computational measures of semantic similarity. We show that the representational geometry of ITC-but not of earlier visual areas (V1)-is reflected both in explicit behavioral ratings of semantic similarity and also in measures of semantic similarity derived from word usage patterns in natural language. Our findings show that patterns of brain activity in ITC not only reflect the organization of visual information into objects but also represent objects in a format compatible with conceptual thought and language.