A new view on visuomotor channels: the case of the disappearing dynamics

A considerable body of kinematic data supports the proposal that independent visuomotor channels are involved in the control of the transport and grip components of reach and grasp. These channels are seen as having separate perceptual inputs, outputs and internal processing and are thought by some to correspond to independent neuroanatomical pathways. The idea that different groups of muscles and biomechanical structures can be controlled independently is attractive, but this kinematically-inspired hypothesis fails to take into account the complexity of the dynamic relationships and their interactions within the neuromusculoskeletal system. Inertial, viscous, centrifugal, coriolis, gravitational and reflex cross couplings exist between efferent drives to muscles and resulting body movements. Rotation at even a single joint generates a complex set of dynamic reaction forces and requires coordinated activation of many muscles throughout the body to maintain posture and balance. In this theoretical paper we present a new view of independent visuomotor channels in the form of an adaptive neural controller that can compensate for the above interactions and decouple the relationships between efferent drives to muscles and resulting body movements. At the same time, the neural controller renders all the dynamics (linear and nonlinear), other than time delays, of the neuromusculoskeletal system, unobservable in the visuomotor relationships. Using the geometry of nonlinear dynamical systems we show that, providing certain constraints on the structure of time delays within the system are satisfied, there exists a neural controller that can render all the dynamics of the neuromusculoskeletal system (except for time delays) unobservable in the responses. The controller simultaneously decouples all the interactive dynamics so that each of the m independent inputs controls one and only one degree of freedom of the response. This means that each degree of freedom in a multi-joint response can be controlled by an independent component of the visual input, a behaviour that has long been observed in visual tracking experiments. The controller effectively establishes m independent visuomotor channels. However, rather than reflecting separate neuroanatomical pathways, the independent channels result from a neural controller with convergent and divergent connections to compensate for the interactive nonlinear dynamics within the neuromusculoskeletal system. This new view of visuomotor channels has implications for neural control processes involved in the acquisition and adaptability of skilled perceptual-motor behaviour in general, as well as for the design of robotic controllers.     

Intergenerational transmission of prejudice, sex role stereotyping, and intolerance

The attitudes of 111 ninth and eleventh graders and both of their biological parents were independently assessed for prejudice against people with HIV/ AIDS, homosexuals, Blacks, and fat people, as well as for male and female sex role stereotyping. This study corrected for two shortcomings in previous research: neglecting to assess both parents and assessing only a single domain of prejudice. We addressed the intergenerational transmission of prejudice and stereotyping using three competing models: same-sex, parent equivalent, and differential effects. Using multiple regressions in which parents' scores were entered separately, along with control variables, different maternal and paternal influences were detected. Mothers were the primary influence for prejudice regarding HIV/AIDS, fatness, and race, and fathers were the primary influence for male and female stereotyping and prejudice against homosexuals, supporting the differential effects model. We also established that prejudice and stereotyping in specific domains reflected a more general proclivity to be intolerant. In contrast to prejudice and stereotyping in specific domains, fathers and mothers about equally shaped the adolescents' intolerance, supporting the parent equivalent model.     

Building a Pink Dinosaur: the Effects of Gendered Construction Toys on Girls’ and Boys’ Play

Play with building toys such as LEGO® sets promotes spatial learning in children. The present study examined the effects of the color of the bricks (either pink or blue) and the femininity/masculinity of the object built on boys’ and girls’ play with LEGO® sets. Children (n = 116, M _age  = 7.27 range = 5–10) were given the opportunity to build with LEGO® brick sets, both instructed and free play tasks. For the instructed task, the type of object (feminine: cat; masculine: dinosaur) and color of the bricks (pink, blue) were counterbalanced across participants. Their play was coded for accuracy of following the instructions and time to complete the task. In the free play task, brick color (pink, blue) was counterbalanced across participants, and structures were coded for femininity/masculinity and the number of bricks used. Overall, children took longer to build a feminine object with blue bricks than with pink bricks. In the free-play task, boys built more masculine objects than girls did, regardless of the color of bricks they were given. Results showed that boys completed the LEGO® tasks faster than did girls, controlling for interest in and experience with LEGO® play. These findings suggest that toy color and type can impact how children interact and play with toys.     

Perceived stress in prodromal Huntington disease

This study examines perceived stress and its relationship to depressive symptoms, life changes and functional capacity in a large sample of individuals who are positive for the Huntington disease (HD) gene expansion but not yet diagnosed. Participants were classified by estimated proximity to HD diagnosis (far, mid, near) and compared with a non-gene-expanded comparison group. Persons in the mid group had the highest stress scores. A significant interaction between age and time since HD genetic testing was also found. Secondary analyses using data from a different data collection point and including a diagnosed group showed the highest stress scores in the diagnosed group. Possible explanations and implications are discussed.     

Change and Stability in Active and Passive Social Influence Dynamics during Natural Drinking Events: A Longitudinal Measurement-Burst Study

We examined the link between social norms and active social influences occurring during natural social drinking contexts. Across 4 yearly measurement-bursts, college students (N = 523) reported daily for 30-day periods on drinking norms, drinking offers, how many drinks they accepted, and personal drinking levels during social drinking events. In contexts where drinking norms were higher, students were more likely to both receive and comply with drinking offers. These acute social influences were highly stable throughout college, but affected men and women differently across time: Women received more drinking offers than men, especially at the beginning of college and when norms were higher, but men complied with more drinking offers per occasion. These effects were not attributable to between-person differences in social drinking motives or drinking levels, nor to within-person patterns of situation-selection. The present work suggests that context-specific drinking norms catalyze active social influence attempts, and further promote compliance drinking.     

Attention and social functioning in children with malformations of cortical development and stroke

Attention and social functioning and their interrelationships have not been routinely examined in children with early brain insult (EBI). This study aimed to describe attention and social functioning in children with two types of EBI: malformations of cortical development (MCD) and stroke. Children diagnosed with MCD (n = 14, 6 males) or stroke (n = 14, 8 males) aged 8 to 14 years (M = 12 years 11 months) completed neuropsychological assessments to examine attention processes. Primary caregivers completed a questionnaire to assess executive components of children's attention and teachers completed a questionnaire to measure children's social functioning. Brain scans (MRI or CT) were coded by a pediatric neuroradiologist. Higher rates of impairments in attention and social function were found in children with EBI compared with normative expectations. Children with MCD experienced more global and clinically significant levels of impairment than children with stroke; though impairments were present in both groups. A strong association between executive components of attention and social function was observed. In addition, complex attention processes were associated with social function. The findings emphasize the reciprocity between attention, behavior and social outcomes, and the vulnerability of social function following EBI.     

Participation and Attrition in a Coping Skills Intervention for Adolescent Girls with Inflammatory Bowel Disease

The current study examined factors associated with adolescent and parent participation in a coping skills intervention for adolescent girls with inflammatory bowel disease (IBD) and examined factors associated with attrition related to intermittent missing data. Thirty-one adolescent girls with IBD and their parents enrolled in the intervention. Psychosocial and disease factors related to participation in the 6-week web component of the coping skills intervention were examined as were baseline group differences between those who provided post-treatment data and those who did not. Adolescents experiencing more difficulties related to their disease and psychosocial functioning participated less in the web component of the treatment intervention. Families who attrited had higher baseline levels of parental catastrophic thoughts, parenting stress, and adolescent depression. Families experiencing greater levels of psychological and disease-related difficulties may be at risk for low participation and eventual dropout from pediatric IBD psychological treatment interventions.     

Memory in motion: Movement dynamics reveal memory strength

Recognition memory is typically examined as a discrete end-state, describable by static variables, such as accuracy, response time, and confidence. In the present study, we combined real-time mouse-tracking with subsequent, overt confidence estimates to examine the dynamic nature of memory decisions. By examining participants' streaming x-, y- mouse coordinates during recognition decisions, we observed that movement trajectories revealed underlying response confidence. More confident decisions were associated with shorter decision times and more linear response trajectories. Less confident decisions were made slowly, with increased trajectory curvature. Statistical indices of curvature and decision times, including area-under-the-curve and time to maximum deviation, suggested that memory strength relates to response dynamics. Whether participants were correct or incorrect, old responses showed a stronger correspondence between mouse trajectories and confidence, relative to new responses. We suggest that people subjectively experience a correspondence between feelings of memory and feelings of confidence; that subjective experience reveals itself in real-time decision processes, as suggested by sequential sampling models of recognition decisions.