Object processing for action across childhood

Human adults process and select the opportunities for action in their environment rapidly, efficiently, and effortlessly. While several studies have revealed substantial improvements in object recognition skills, motor abilities, and control over the motor system during late childhood, surprisingly little is known about how object processing for action develops during this period. This study addresses this issue by investigating how the ability to ignore actions potentiated by a familiar utensil develops between ages 6 and 10 years. It is the first study to demonstrate that (1) the mechanisms that transform a graspable visual stimulus into an object‐appropriate motor response are in place by the sixth year of life and (2) graspable features of an object can facilitate and interfere with manual responses in an adult‐like manner by this age. The results suggest that there may be distinct developmental trajectories for the ability to ignore motor responses triggered by visual affordances and the stimulus response compatibility effects typically assessed with Simon tasks.     

Dynamics of Pushing

A standing individual can use several strategies for modulating pushing force magnitude. Using a static model, researchers have shown that the efficacy of those strategies varies considerably. In the present article, the authors propose a human motor control dynamic model for analyzing transients that occur when an individual is asked to modulate force magnitude. According to the model, the impedances of both the upper and the lower limbs influence the time course of force variations and foot placement has a profound effect on pushing force dynamics. With a feet-together posture, the center of pressure has a limited range of motion and changes in force may be preceded by initial changes in the opposite direction; that is, to decrease force, an individual must first increase force. When the feet are placed apart, individuals can move the center of pressure over a much larger range, thereby modulating pushing force magnitude, without reversing behavior, over a larger range of force magnitudes. Therefore, the best way to control pushing force at the hand may be by using the foot.     

Religious Orders Study: Overview and Change in Cognitive and Motor Speed

The Religious Orders Study is a longitudinal, clinical-pathologic study of aging and Alzheimer’s disease in older Catholic nuns, priests, and brothers. In the first section of the paper, we describe the overall design and methods of the Religious Orders Study and summarize published findings. In the second section, we present new longitudinal analyses of change in summary measures of motor, perceptual, and verbal speed in 800 Religious Orders Study participants examined annually for a mean of approximately 5 years. In each domain, speed declined about 2% per year. There were wide individual differences, however, and rates of slowing in each domain were only moderately intercorrelated and were predicted by different factors. The results suggest age-related slowing is more person-specific and domain-specific than previously supposed.     

Imagery and the processing of visuo-spatial representations: A symposium

Abstract

Four cross-language primed lexical decision experiments were carried out to test models of cross-language priming. The first experiment varied the proportion of related pairs, but this manipulation did not affect the size of the priming effects. In Experiments 2 and 3, the subjects were asked to respond at a specific fast rate. This resulted in significant priming within languages, but priming in the cross-language conditions disappeared. The subjects in Experiment 4 were also asked to respond at a specific fast rate, but the stimuli in this experiment were translation equivalents. Cross-language priming occurred with the translations under the same conditions where it had disappeared with primary associates. These results suggest that cross-language priming between primary associates is due to a post-lexical meaning-integration process which the subjects can detach from the normal reading sequence if it slows their responses in relation to goal response rate.     

The influence of spatial pattern on visual short-term memory for contrast

Several psychophysical studies of visual short-term memory (VSTM) have shown high-fidelity storage capacity for many properties of visual stimuli. On judgments of the spatial frequency of gratings, for example, discrimination performance does not decrease significantly, even for memory intervals of up to 30 s. For other properties, such as stimulus orientation and contrast, however, such “perfect storage” behavior is not found, although the reasons for this difference remain unresolved. Here, we report two experiments in which we investigated the nature of the representation of stimulus contrast in VSTM using spatially complex, two-dimensional random-noise stimuli. We addressed whether information about contrast per se is retained during the memory interval by using a test stimulus with the same spatial structure but either the same or the opposite local contrast polarity, with respect to the comparison (i.e., remembered) stimulus. We found that discrimination thresholds got steadily worse with increasing duration of the memory interval. Furthermore, performance was better when the test and comparison stimuli had the same local contrast polarity than when they were contrast-reversed. Finally, when a noise mask was introduced during the memory interval, its disruptive effect was maximal when the spatial configuration of its constituent elements was uncorrelated with those of the comparison and test stimuli. These results suggest that VSTM for contrast is closely tied to the spatial configuration of stimuli and is not transformed into a more abstract representation.     

Enriched housing reverses age-associated impairment of cognitive functions and tPA-dependent maturation of BDNF

Although tissue type plasminogen activator (tPA) and brain derived neurotrophic factor (BDNF) have been extensively described to influence brain outcomes in a number of disorders, their roles during physiological aging are poorly investigated. In the present study, we investigated whether maintenance of mice in different environmental conditions could influence age-associated changes in hippocampal tPA expression and BDNF maturation in relation with modifications of their cognitive performances. Our data indicate that maintenance in enriched housing led to a reversal of age-associated decrease in expression of hippocampal tPA. A subsequent increase in the level of mature BDNF and an improvement in emotional and spatial memories were observed. Taken together, these data suggest that the tPA–BDNF axis could play a critical role in the control of cognitive functions influenced both by the age and housing conditions.     

The influence of number of syllables on word skipping during reading

In an eye-tracking experiment, participants read sentences containing a monosyllabic (e.g., grain) or a disyllabic (e.g., cargo) five-letter word. Monosyllabic target words were skipped more often than disyllabic target words, indicating that syllabic structure was extracted from the parafovea early enough to influence the decision of saccade target selection. Fixation times on the target word when it was fixated did not show an influence of number of syllables, demonstrating that number of syllables differentially impacts skipping rates and fixation durations during reading. [corrected]