Task requirements influence sensory integration during grasping in humans

The sensorimotor transformations necessary for generating appropriate motor commands depend on both current and previously acquired sensory information. To investigate the relative impact (or weighting) of visual and haptic information about object size during grasping movements, we let normal subjects perform a task in which, unbeknownst to the subjects, the object seen (visual object) and the object grasped (haptic object) were never the same physically. When the haptic object abruptly became larger or smaller than the visual object, subjects in the following trials automatically adapted their maximum grip aperture when reaching for the object. This adaptation was not dependent on conscious processes. We analyzed how visual and haptic information were weighted during the course of sensorimotor adaptation. The adaptation process was quicker and relied more on haptic information when the haptic objects increased in size than when they decreased in size. As such, sensory weighting seemed to be molded to avoid prehension error. We conclude from these results that the impact of a specific source of sensory information on the sensorimotor transformation is regulated to satisfy task requirements.     

Short and long-term motor skill learning in an accelerated rotarod training paradigm

Rodent models of motor skill learning include skilled forelimb reaching and acrobatic locomotor paradigms. This study characterizes motor skill learning in the accelerated rotarod task. Thirty Long-Evans rats (300-400 g) were trained on an accelerated rotarod (1cm/s(2)) over eight consecutive sessions (=days, 20 trials each). Improvement in rotarod velocities mastered before falling off the rod was observed within and between sessions (plateau after five sessions). Intrasession improvement was incompletely retained at the beginning of the next day's session. Over several training sessions, intrasession improvement diminished, suggesting a ceiling effect. After 1 week of pause, the rotarod skill was retained. Locomotor exercise in a running wheel for 30 min before the first rotarod session did not affect intrasession improvement. Running-wheel exposure for 6 days did not diminish the rate of rotarod skill learning (steepness of the learning curve) but improved overall performance (upward shift of curve). Video analysis of gait on the rotarod showed that rats developed a motor strategy by modifying their gait patterns during training. The data demonstrate that rotarod improvement is not the result of enhanced general locomotor ability or fitness, which are trained in the running wheel, but requires a change in the motor strategy to master the task. Accelerated rotarod training can be regarded a valid paradigm for motor skill learning over short (intrasession, minutes) and long time frames (intersession, days).     

The clinical efficacy and safety of galantamine in the treatment of Alzheimer's disease

Alzheimer's disease is a progressive, neurodegenerative condition characterized by deficits in cognition, inability to perform activities of daily living, and alterations in behavior. Galantamine hydrobromide is the newest acetylcholinesterase inhibitor (AChEI) approved in the United States for the treatment of mild-to-moderate AD. The safety and efficacy of galantamine has been demonstrated in multiple randomized, Phase III trials of >2,600 patients with mild-to-moderate AD. Studies have found that galantamine improved or maintained performance in all domains of AD (cognition, function, behavior, and caregiver burden) in the short term and slowed the decline in performance or maintained baseline performance through 12 months. The dual mechanism of action may make galantamine a reasonable treatment option for both newly diagnosed patients and patients who have not benefitted from or have poorly tolerated current therapy.     

Mild hypoxia disrupts recollection,not familiarity

Yonelinas et al. (2002) found that hypoxic patients exhibited deficits in recollection that left familiarity relatively unaffected. In contrast, Manns, Hopkins, Reed, Kitchener, and Squire (2003) studied a group of hypoxic patients who suffered severe and equivalent deficits in recollection and familiarity. We reexamine those studies and argue that the discrepancy in results is likely due to differences in the hypoxic groups that were tested (i.e., differences in amnestic severity, subject sampling methods, and patient etiology). Yonelinas et al. examined memory in 56 cardiac arrest patients who suffered a brief hypoxic event, whereas Manns et al. examined a group of severely amnesic patients that consisted of 2 cardiac arrest patients, 2 heroin overdose patients, 1 carbon monoxide poisoning patient, and 2 patients with unknown etiologies. We also consider an alternative explanation proposed by Wixted and Squire (2004), who argued that the two patient groups suffered similar deficits, but that statistical or methodological artifacts distorted the results of each of Yonelinas et al.'s experiments. A consideration of those results, however, indicates that such an explanation does not account for the existing data. All of the existing evidence indicates that recollection, but not familiarity, is disrupted in mild hypoxic patients. In more severe cases of hypoxia, or those with more complex etiologies such as heroin overdose, more profound deficits may be observed.     

Raters who pursue different goals give different ratings

J. N. Cleveland and K. R. Murphy (1992) suggested that phenomena such as rater errors and interrater disagreements could be understood in terms of differences in the goals pursued by various raters. We measured 19 rating goals of students at the beginning of a semester, grouped them into scales, and correlated these with teacher evaluations collected at the end of the semester. We found significant multiple correlations, both within classes and in an analysis of the pooled sample (adjusting for instructor mean differences, incremental R2 =.08). Measures of rating goals obtained after raters had observed a significant proportion of ratee performance accounted for variance (incremental R2 =.07) not accounted for by measures of goals obtained at the beginning of the semester.     

A model of childhood perceived peer harassment: analyses of the Canadian National Longitudinal Survey of Children and Youth Data

The authors developed a model of childhood perceived peer harassment, using several personality, peer, and familial characteristics of victims, and tested it with children 10 to 11 years old (N = 3,434) drawn from the Canadian National Survey of Children and Youth, which is a stratified random sample of 22,831 households in Canada. A 3-step analytic procedure with 3 separate subsamples of the children was used to explore psychosocial correlates of peer harassment. Results from the latent variable path analysis (comparative fit index = .90) showed that victims are likely to feel anxious and disliked by their peers. Their parents reported using high levels of control and low levels of warmth with their children and reported high levels of depression and marital conflict themselves. These results are discussed from a social-cognitive perspective.     

Immediate spatial distortions of pointing movements induced by visual landmarks

We tested the influence of two horizontally aligned visual landmarks on pointing movements to memorized targets, to investigate whether the visuomotor system can make use of an egocentric representation unaffected by visual context. The endpoints of pointing movements were systematically distorted toward the nearest visual landmark, indicating that spatial representations included both target and nontarget information. These distortions were not due to the presence of the landmarks during the movement but, rather, to their presence in the encoding phase. Qualitatively similar distortions were present even with the shortest possible retention phase, when the target was extinguished at movement onset. Finally, we found the same pattern of distortion when participants were forced to remember the target within an allocentric frame of reference. We argue that even early memory representations for pointing movements are influenced by visual information in the surrounding visual field.     

Co-reference and reasoning

Memory &; Cognition - Co-reference occurs when two or more noun phrases refer to the same individual, as in the following inferential problem: Mark is kneeling by the fire or he is looking at...