Predictable and self-initiated visual motion is judged to be slower than computer generated motion

Self-initiated action effects are often perceived as less intense than identical but externally generated stimuli. It is thought that forward models within the sensorimotor system pre-activate cortical representations of predicted action effects, reducing perceptual sensitivity and attenuating neural responses. As self-agency and predictability are seldom manipulated simultaneously in behavioral experiments, it is unclear if self-other differences depend on predictable action effect contingencies, or if both self- and externally generated stimuli are modulated similarly by predictability. We factorially combined variation in (1) predictability of action effects, (2) spatial congruence, and (3) performance by the self or computer to dissociate these influences on a visual discrimination task. Participants performed 2AFC speed judgments. Self-initiated motion was judged to be slower than computer-initiated motion when action effect contingencies were predictable, while spatial congruence influenced speed judgments only when action effect contingencies were unpredictable. Results are discussed in relation to current theories of sensory attenuation.     

Taking credit for success: The phenomenology of control in a goal-directed task

We studied how people determine when they are in control of objects. In a computer task, participants moved a virtual boat towards a goal using a joystick to investigate how subjective control is shaped by (1) correspondence between motor actions and the visual consequences of those actions, and (2) attainment of higher-level goals. In Experiment 1, random discrepancies from joystick input (noise) decreased judgments of control (JoCs), but discrepancies that brought the boat closer to the goal and increased success (the autopilot) increased JoCs. In Experiment 2, participants raced to the goal against a computer-controlled rival boat while varying levels of noise interfered with each boat. Participants reached the goal more often and rated their own control higher when the computer rival had good control. Subjective control over moving objects depends partly on consistency between motor actions and their effects, but is also modulated by perceived success and competition.     

Co-occurring disorders: a possible key to visual perceptual deficits in children with developmental coordination disorder?

A study was conducted to examine how visual perceptual functioning in children with DCD may be influenced by co-occurring learning problems such as reading disabilities (RD) and/or attention deficit hyperactivity disorder (ADHD). Participants included seven groups of children: 27 children with DCD only, 11 with ADHD only, 14 with RD only, 63 with DCD and at least one other disorder (i.e., DCD + ADHD, DCD + RD, DCD + ADHD + RD), and 73 typically developing controls. Visual perceptual skills were assessed using the Test of Visual Perceptual Skills (TVPS) and the Rey Osterreith Complex Figure (ROCF; copy and delayed recall). Children with DCD and at least one other disorder were found to have impairments on the TVPS compared to children with DCD only, ADHD only, and typically developing controls, particularly on subtests assessing visual memory. On the ROCF, children with DCD and at least one other disorder scored significantly lower than children with ADHD only or RD only. Children with DCD plus one other disorder were then subdivided into three groups: DCD + ADHD, DCD + RD, and DCD + ADHD + RD and compared to children with DCD only, ADHD only, and RD only. Results indicated that children with DCD + ADHD + RD had significant impairments on the TVPS compared to children with DCD only and children with ADHD only. On the ROCF, children with DCD + ADHD + RD scored significantly lower than all of the groups, except the DCD+RD group. These findings suggest that DCD on its own is not associated with visual perceptual problems; rather, it is the presence of co-occurring disorders that is a possible key to visual perceptual deficits in children with DCD. The number of co-occurring disorders present with DCD is associated with the severity of the visual perceptual dysfunction. Deficits in visual memory skills appear to be a specific area of difficulty for children with DCD and co-occurring RD and/or ADHD.     

Activities of daily living in children with developmental coordination disorder: dressing, personal hygiene, and eating skills

In order to understand how age, culture, and problems in motor coordination impact the performance of activities of daily living, we used focus groups and in-depth interviews with Australian and Canadian parents to examine activities of daily living of younger (5-7 years of age) and older (8-9 years of age) children with and without DCD. By comparison with their typically developing age group, children with DCD had more difficulty with dressing, personal hygiene, and eating skills. Difficulties with postural control and fine-motor skills were reported to contribute to poorer performance of activities of daily living. As expected, competence in the performance of activities of daily living improved in the older children with and without DCD and there were few differences in the performance of daily living tasks between typical children in Australia and Canada. Overall, the motor difficulties of children with DCD had a significant impact on performance of a wide range of daily activities.     

Characteristics of adolescents charged with homicide: Review of 72 cases

The present study examined a comparatively large sample of 72 adolescents charged with murder who were referred for pretrial evaluation in the State of Michigan over a 9-year period. Subjects are compared with a control group of 35 adolescents charged with nonviolent larceny offenses. Information regarding the adolescents' demographic and social background, and the circumstances of the offense, are presented. Recognition of the diverse motives and circumstances of adolescent homicide may help to explain discrepant characterizations of them presented in the literature.     

Neuropsychological outcome following unilateral stereotactic pallidotomy in intractable Parkinson's disease

Neuropsychological functioning was examined at baseline and 2- to 3-month follow-up in 40 subjects with advanced Parkinson's disease (PD) who underwent unilateral posteroventral pallidotomy. Most subjects demonstrated improved verbal learning, visual memory, confrontation naming, and figural fluency at follow-up. Right pallidotomy was associated with decreased cognitive flexibility and increased verbal fluency, whereas Left pallidotomy uniquely resulted in a decline in verbal fluency. Significant motor improvement was demonstrated in both groups. Pallidotomy appears to be an effective treatment for advanced PD, providing a significant improvement in motor functioning, while resulting in few deleterious neurocognitive changes in most cases.