Combining Nonlinear Biometric and Psychometric Models of Cognitive Abilities

It is well-established that genetic factors account for large proportions of individual differences in multiple cognitive abilities. It is also well-established that individual differences in performance on many different cognitive ability measures are strongly correlated. Recent empirical investigations, however, have suggested two interesting qualifications to these well-established findings: Genetic variance in cognitive abilities is higher in richer home environments (gene-by-environment interaction), and common variance in different cognitive abilities is lower at higher levels of overall ability (nonlinear factor structure). Although they have been investigated independently, these two phenomena may interact, because richer environments are routinely associated with higher ability levels. Using simulation we demonstrate how un-modeled nonlinear factor structure can obscure interpretation of gene-by-environment interaction. We then reanalyze data from the National Collaborative Perinatal Project, previously used by Turkheimer et al. (2003; Psychol Science), with a two-step method to model both phenomena.

Randomizing visual feedback in manual aiming: reminiscence of the previous trial condition and prior knowledge of feedback availability

A trial-by-trial analysis was used to systematically examine the influence of switching visual conditions on visual feedback utilization for a manual aiming movement. In experiment one, vision was randomly manipulated from trial to trial with no more than four consecutive trials in the same visual condition. In experiment two, participants were provided with certainty of visual feedback availability prior to every trial. Results of both studies revealed that movement endpoint variability was most associated with visual feedback availability on the previous trial. Furthermore, correlation analyses comparing movement trajectory at 25, 50 and 75% with movement end (i.e. 100%) revealed that the efficiency of online corrections also depends on the availability of visual feedback on the previous trial. These results suggest that the accuracy of an aiming movement is highly dependent on processing of offline visual information from the preceding trial. This study was supported by a grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) awarded to Luc Tremblay.

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Straight ahead acts as a reference for visuomotor adaptation

One can adapt movement planning to compensate for a mismatch between vision and action. Previous research with prismatic lenses has shown this adaptation to be accompanied with a shift in the evaluation of one’s body midline, suggesting an important role of this reference for successful adaptation. This interpretation leads to the prediction that rotation adaptation could be more difficult to learn for some directions than others. Specifically, we hypothesized that targets seen to the right of the body midline but for which a rotation imposes a movement to its left would generate a conflict leading to a bias in movement planning. As expected, we observed different movement planning biases across movement directions. The same pattern of biases was observed in a second experiment in which the starting position was translated 15 cm to the right of the participants’ midline. This indicates that the “straight ahead” direction, not one’s midline, serves as an important reference for movement planning during rotation adaptation.

Misperceiving the speed-accuracy tradeoff: imagined movements and perceptual decisions

Research has suggested that prospective motor decisions are consistent with actual motor action. In a study that we recently published (Young et al. in Exp Brain Res 185:681–688, 2008), however, participants demonstrated a preference for closer targets that was inconsistent with the predictions of Fitts’s law. With a pair of experiments, the present paper investigates the underlying basis of this non-optimal behaviour. Participants showed a similar deviation from Fitts’s law when imagining movements—believing that movement duration increased with distance within the same index of difficulty. Participants did not behave similarly, however, in a perceptual version of the decision task. These results suggest that imagined movements and motor decisions are linked, as well as demonstrating one situation in which both show a similar deviation from the patterns of actual movement duration.

Computational Modeling and Real-Time Control of Patient-Specific Laser Treatment of Cancer

An adaptive feedback control system is presented which employs a computational model of bioheat transfer in living tissue to guide, in real-time, laser treatments of prostate cancer monitored by magnetic resonance thermal imaging. The system is built on what can be referred to as cyberinfrastructure—a complex structure of high-speed network, large-scale parallel computing devices, laser optics, imaging, visualizations, inverse-analysis algorithms, mesh generation, and control systems that guide laser therapy to optimally control the ablation of cancerous tissue. The computational system has been successfully tested on in vivo, canine prostate. Over the course of an 18 min laser-induced thermal therapy performed at M.D. Anderson Cancer Center (MDACC) in Houston, Texas, the computational models were calibrated to intra-operative real-time thermal imaging treatment data and the calibrated models controlled the bioheat transfer to within 5 °C of the predetermined treatment plan. The computational arena is in Austin, Texas and managed at the Institute for Computational Engineering and Sciences (ICES). The system is designed to control the bioheat transfer remotely while simultaneously providing real-time remote visualization of the on-going treatment. Post-operative histology of the canine prostate reveal that the damage region was within the targeted 1.2 cm diameter treatment objective.

Physician challenges in communicating bad news

Communicating bad news is never easy and for physicians these interactions may be a significant source of stress. To examine the characteristics that make delivering of bad news stressful, two studies were conducted. In the first study, 37 physicians generated 192 responses describing the characteristics that influence how difficult it is to break bad news. After sorting the responses in terms of common themes, six categories were identified: Physician, Patient, Institutional, Illness, Relationship, and Mishap. In Study 2, 115 physicians rated the degree of stress associated with each factor. Using principle component and reliability analyses, empirical support was found for six categories. A higher-order factor analysis suggested the existence of one over-arching factor. Items in the Mishap category were rated on average as the most stressful. Stress scores were largely unrelated to years in practice, experience delivering bad news or training.

Physical inactivity and cognitive functioning: results from bed rest studies

In addition to multiple health benefits, participation in physical activity can enhance cognitive functioning. Less clear is how reducing physical activity levels affects cognition, an issue potentially addressed by bed rest studies having included cognitive tests. Detailed and reviewed here are 17 such studies, featuring 251 subjects, bed rest for 7–70 days, and tests of cognition ranging from reaction time to executive functions. The reported effects of bed rest on cognitive performance vary considerably, from a generally expected worsening to an improvement. Practice effects could be implicated in the performance improvements, and reports of worsening are often of limited interpretability or the results were not replicated. Any cognitive effects of bed rest thus remain to be established. Detrimental effects could influence the in-progress plans for human spaceflights to Mars (simulated by bed rest), and have implications for medical conditions promoting inactivity and lifestyles that are largely sedentary.

3D-patient-specific geometry of the muscles involved in knee motion from selected MRI images

Patient-specific muscle geometry is not only an interesting clinical tool to evaluate different pathologies and treatments, but also provides an essential input data to more realistic musculoskeletal models. The protocol set up in our study provided the 3D-patient-specific geometry of the 13 main muscles involved in the knee joint motion from a few selected magnetic resonance images (MRIs). The contours of the muscles were identified on five to seven MRI axial slices. A parametric-specific object was then constructed for each muscle and deformed to fit those contours. The 13 muscles were obtained within 1 h, with less than 5% volume error and 5 mm point-surface error (2RMS). From this geometry, muscle volumes and volumic fractions of asymptomatic and anterior cruciate ligament deficient subjects could easily be computed and compared to previous studies. This protocol provides an interesting precision/time trade-off to obtain patient-specific muscular geometry.

Shared-Environmental Contributions to High Cognitive Ability

Using a combined sample of adolescent twins, biological siblings, and adoptive siblings, we estimated and compared the differential shared-environmentality for high cognitive ability and the shared-environmental variance for the full range of ability during adolescence. Estimates obtained via multiple methods were in the neighborhood of 0.20, and suggest a modest effect of the shared environment on both high and full-range ability. We then examined the association of ability with three measures of the family environment in a subsample of adoptive siblings: parental occupational status, parental education, and disruptive life events. Only parental education showed significant (albeit modest) association with ability in both the biological and adoptive samples. We discuss these results in terms of the need for cognitive-development research to combine genetically sensitive designs and modern statistical methods with broad, thorough environmental measurement.

Goal-related planning constraints in bimanual grasping and placing of objects

Our primary objective was to examine the possible interplay of the end-state comfort effect and bimanual temporal and spatial coupling constraints in a grasp-to-place task. Unimanual and bimanual grasping and placing tasks were employed with manipulations on initial comfort (by use of potentially interfering obstacles) and target goals (using various demands on end goal object orientations). Confirming previous temporal findings, incongruent bimanual tasks were considerably slower in initiation time and movement time than congruent ones, reflecting costs in conceptualizing, planning, and completion of the task. With respect to spatial constraints, when the same goal was present for both hands there was strong evidence of the influence of both end-state comfort and bimanual constraints. This was often not the case when the task demands differed for the two hands, although the primary task goals were still attained. We suggest that the implementation of constraints is not based on a strict hierarchy; rather, certain constraints become dominant depending on the task and situation.

Genetic and Environmental Mediation Between Measures of Personality and Family Environment in Twins Reared Together

In this study we analyzed the etiology of the relationship between personality traits and retrospectively recalled family environment. The data of 226 identical and 168 fraternal twin pairs reared together from the Jena twin study of social attitudes were available. Personality traits were measured using the self- and peer report versions of the German NEO-personality inventory-revised. A German version of Blocks Environmental Questionnaire was applied to measure two broad dimensions of the family environment retrospectively: support and organization. We could replicate earlier findings that retrospective reports of these family environment dimensions were in part genetically influenced. A total of 66% of the genetic variance in support and 24% in organization could be accounted for by heritable variance in self-rated personality. That was replicated by using peer reports of personality, 41% explained genetic variance in support and 17% in organization. Environmental mediations were negligible. This indicates that the relationship between personality and retrospectively recalled family environment is largely genetically mediated.

Perception of affordances for standing on an inclined surface depends on height of center of mass

We investigated whether perception of affordances for standing on an inclined surface depended on the height of center of mass of the perceiver-actor. Participants adjusted the angle of inclination of a surface until they felt that it was just barely possible for them to stand on that surface. They performed this task while wearing a backpack apparatus to which masses were attached in one of three configurations—high-mass, low-mass, and no-mass. Moreover, participants performed this task by viewing the inclined surface or by probing it with a hand-held rod (while blindfolded). Perception of affordances for standing on the inclined surface reflected the changes in center of mass brought on by the weighted backpack apparatus (the perceptual boundary occurred at a smaller angle of inclination in the high-mass condition than in the low-mass condition and in the no-mass condition). Moreover, perception of this affordance reflected such changes both when the surface was viewed and when the surface was probed with a hand-held rod (while blindfolded). The results highlight that perception of affordances is dynamic and task-dependent and suggest that the stimulation patterns that support perception of affordances are invariant and modality-independent.

Adaptations of lateral hand movements to early and late visual occlusion in catching

Recent studies suggested that the control of hand movements in catching involves continuous vision-based adjustments. More insight into these adjustments may be gained by examining the effects of occluding different parts of the ball trajectory. Here, we examined the effects of such occlusion on lateral hand movements when catching balls approaching from different directions, with the occlusion conditions presented in blocks or in randomized order. The analyses showed that late occlusion only had an effect during the blocked presentation, and early occlusion only during the randomized presentation. During the randomized presentation movement biases were more leftward if the preceding trial was an early occlusion trial. The effect of early occlusion during the randomized presentation suggests that the observed leftward movement bias relates to the rightward visual acceleration inherent to the ball trajectories used, while its absence during the blocked presentation seems to reflect trial-by-trial adaptations in the visuomotor gain, reminiscent of dynamic gain control in the smooth pursuit system. The movement biases during the late occlusion block were interpreted in terms of an incomplete motion extrapolation—a reduction of the velocity gain—caused by the fact that participants never saw the to-be-extrapolated part of the ball trajectory. These results underscore that continuous movement adjustments for catching do not only depend on visual information, but also on visuomotor adaptations based on non-visual information.

Saccadic inhibition underlies the remote distractor effect

The remote distractor effect is a robust finding whereby a saccade to a lateralised visual target is delayed by the simultaneous, or near simultaneous, onset of a distractor in the opposite hemifield. Saccadic inhibition is a more recently discovered phenomenon whereby a transient change to the scene during a visual task induces a depression in saccadic frequency beginning within 70 ms, and maximal around 90–100 ms. We assessed whether saccadic inhibition is responsible for the increase in saccadic latency induced by remote distractors. Participants performed a simple saccadic task in which the delay between target and distractor was varied between 0, 25, 50, 100 and 150 ms. Examination of the distributions of saccadic latencies showed that each distractor produced a discrete dip in saccadic frequency, time-locked to distractor onset, conforming closely to the character of saccadic inhibition. We conclude that saccadic inhibition underlies the remote distractor effect.

Application of Whole Mouse Embryo Culture System on Stem Cell Research

The normal development of mouse embryo in vivo could be maintained in vitro up to 72 h in the presence of rat serum which is continuously supplied with the appropriate concentration of O₂ and CO₂. There are several applications of the whole mouse embryo culture model for study of cellular dynamics in hematopoiesis and its interaction with vasculogenesis. In this protocol, we have described details of manipulation techniques in combination with the whole embryo culture and also some advance techniques applied to the mouse embryo such as intra-cardiac inoculation of acetylated low density lipoprotein for cell-specific labeling and engraftment of donor yolk-sac from different genotype/phenotype mouse embryo onto the yolk-sac of host mouse for study of the dynamic distribution of hematopoietic cell.

Crossmodal interaction in saccadic reaction time: separating multisensory from warning effects in the time window of integration model

In a focused attention task saccadic reaction time (SRT) to a visual target stimulus (LED) was measured with an auditory (white noise burst) or tactile (vibration applied to palm) non-target presented in ipsi- or contralateral position to the target. Crossmodal facilitation of SRT was observed under all configurations and stimulus onset asynchrony (SOA) values ranging from  −500 (non-target prior to target) to 0 ms, but the effect was larger for ipsi- than for contralateral presentation within an SOA range from  −200 ms to 0. The time-window-of-integration (TWIN) model (Colonius and Diederich in J Cogn Neurosci 16:1000, 2004) is extended here to separate the effect of a spatially unspecific warning effect of the non-target from a spatially specific and genuine multisensory integration effect.

High genetic diversity of Sappinia-like strains (Amoebozoa, Thecamoebidae) revealed by SSU rRNA investigations

Sappinia diploidea is known as a free-living amoeba of worldwide distribution and has also been reported as causative agent of a brain infection in an immunocompetent young man. In the current study, we were able to isolate eight strains of S. diploidea-like amoebae identified by light microscopy from different habitats. Cultures of all strains were established successfully for molecular characterization. The small subunit ribosomal RNA genes of all strains were sequenced and compared to one another, to the neotype of S. diploidea, and to strains of Sappinia pedata, the only other Sappinia species known to date, from GenBank by multiple sequence alignment and cluster analysis. Altogether, the phylogenetic position of the genus Sappinia within the Thecamoebidae was corroborated; however, it was shown that the genus splits into several well-separated clusters making the establishment of new species within this genus inevitable. Furthermore, two of the S. diploidea-like strains were actually more closely related to S. pedata than to S. diploidea, although the diagnostically relevant standing form which seems to be characteristic for S. pedata was not observed in either of the two strains. Claudia Wylezich and Julia Walochnik have contributed equally to this work.

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Response preparation changes during practice of an asynchronous bimanual movement

For synchronous bimanual movements, we have shown that a different amplitude can be prepared for each limb in advance and this preparation improves with practice (Maslovat et al. 2008). In the present study, we tested whether an asynchronous bimanual movement can also be prepared in advance and be improved with practice. Participants practiced (160 trials) a discrete bimanual movement in which the right arm led the left by 100 ms in response to an auditory “go” signal (either 80 dB control stimulus or 124 dB startle stimulus). The startle stimulus was used to gauge whether inter-limb timing could be pre-programed. During startle trials, the asynchronous bimanual movement was triggered at early latency suggesting the entire movement could be prepared in advance. However, the triggered movement had a shorter between-arm delay and a temporally compressed within-arm EMG pattern, results that we attribute to increased neural activation caused by the startling stimulus. However, as both startle and control trials improved over time, it does appear response preparation of interval timing can improve with practice.

Interaction of intensity and order regarding painful events

While stimulus intensity obviously affects degree of pain responding, presentation order effects of stimuli of different intensities on acute pain responses are under-researched. The present study examined the effects of manipulating presentation order of lower and higher pain stimulus intensity. Using 96 undergraduates, this investigation employed a 2 × 2 mixed research design, with pain stimulus sequence as a between-subjects variable and pain stimulus trial as a repeated measure. When the greater pain stimulus intensity was presented last, verbal report of pain was higher. Also, performance of a cognitive task was interrupted the least when the lower stimulus intensity was presented last. Heart rate, however, was highest when the greater stimulus intensity was presented first, and pain tolerance was greatest when the lower stimulus intensity was presented first. Results are discussed in relation to adaptation-level effects, and implications for pain experienced in clinical settings are suggested.