Coordination among thigh muscles including the vastus intermedius and adductor magnus at different cycling intensities

Although many studies have been focused on muscle synergies in the lower limbs, synergies of the thigh muscles during cycling have not been investigated in detail. We examined synergies of the thigh muscles including the vastus intermedius (VI) and adductor magnus (AM) while cycling. Eight healthy men pedaled at 20%, 40%, 60%, 80% and 100% of maximal aerobic power output at a constant cadence of 60 rpm. Surface electromyography (EMG) recorded signals from the deep VI and the three superficial quadriceps femoris (QF) muscles, the two hamstrings and the AM. The root mean square of the EMG signal was averaged every 2° of crank rotation and normalized by the peak value for each muscle. We used factor analysis to assess normalized EMG recordings while cycling and to identify thigh muscle synergies. The VI, the superficial QF muscles and the AM dominated the first muscle synergy at all power output levels. The AM also formed a second synergy with the two hamstrings at all power output levels. These results suggest that the VI coordinates with the other QF and AM muscles, and that the AM coordinates with the QF and hamstring muscles while cycling.     

Models that allow us to perceive the world more accurately also allow us to remember past events more accurately via differentiation

Differentiation is a theory that originally emerged from the perception literature and proposes that with experience, the representation of stimuli becomes more distinct from or less similar to the representation of other stimuli. In recent years, the role of differentiation has played a critical role in models of memory. Differentiation mechanisms have been implemented in episodic memory models by assuming that information about new experiences with a stimulus in a particular context accumulates in a single memory trace and these updated memory traces become more distinct from the representations of other stimuli. A key implication of such models is that well encoded events are less confusable with other events. This prediction is particularly relevant for two important phenomena. One is the role of encoding strength on memory. The strength based mirror effect is the finding of higher hit rates and lower false alarm rates for a list composed of all strongly encoded items compared to a list composed of all weakly encoded items. The other is output interference, the finding that accuracy decreases across a series of test trials. Results from four experiments show a tight coupling between these two empirical phenomena such that strongly encoded target items are less prone to interference. By proposing a process model and evaluating the predictions of the model, we show how a single theoretical principle, differentiation, provides a unified explanation for these effects.     

Talking while looking: On the encapsulation of output system representations

The idea that the human mind can be divided into distinct (but interacting) functional modules is an important presupposition in many theories of cognition. While previous research on modularity predominantly studied input domains (e.g., vision) or central processes, the present study focused on cognitive representations of output domains. Specifically, we asked to what extent output domain representations are encapsulated (i.e., immune to influence from other domains, representing a key feature of modularity) by studying determinants of interference between simultaneous action demands (oculomotor and vocal responses). To examine the degree of encapsulation, we compared single- vs. dual-response performance triggered by single stimuli. Experiment 1 addressed the role of stimulus modality under dimensionally overlapping response requirements (stimuli and responses were spatial and compatible throughout). In Experiment 2, we manipulated the presence of dimensional overlap across responses. Substantial performance costs associated with dual-response (vs. single-response) demands were observed across response modalities, conditions, and experiments. Dimensional overlap combined with shared spatial codes across responses enabled response-code priming (i.e., beneficial crosstalk between output domains). Overall, the results are at odds with the idea of strong encapsulation of output system representations and show how processing content determines the extent of interdependency between output domains in cognition.     

工作记忆内容驱动完全无关刺激捕获注意

研究通过三个实验以检验工作记忆内容能否自动引导注意选择视场中与之匹配的任务完全无关刺激。实验一要求被试在工作记忆保持阶段完成一个视觉搜索任务，结果发现当搜索序列外的无关干扰刺激与工作记忆内容匹配时搜索绩效显著降低；实验二结果表明该干扰效应不能归因于自下而上的启动机制，因为对颜色刺激仅仅进行知觉辨认而没有工作记忆加工时并没有产生启动效应；实验三通过缩短搜索任务刺激的呈现时间以使得被试在完成搜索任务前没有足够时间眼跳至无关干扰刺激，结果发现了与实验一类似的干扰效应，说明在没有眼跳的情况下与工作记忆内容匹配的完全无关刺激可以捕获注意。这些结果表明保持在工作记忆中的信息表征可以自动引导注意选择视场中与之匹配的任务完全无关刺激，为基于工作记忆内容的注意捕获提供了新证据支持。     

Searching in the sand: Protracted video deficit in U.S. preschoolers' spatial recall using a continuous search space

Young children exhibit a video deficit for spatial recall, learning less from on-screen than in-person demonstrations. Some theoretical accounts emphasize memory constraints (e.g., insufficient retrieval cues, competition between memory representations). Such accounts imply memory representations are graded, yet video deficit studies measuring spatial recall operationalize memory retrieval as dichotomous (success or failure). The current study tested a graded-representation account using a spatial recall task with a continuous search space (i.e., sandbox) rather than discrete locations. With this more sensitive task, a protracted video deficit for spatial recall was found in children 4–5 years old (n = 51). This may be due to weaker memory representations in the screen condition, evidenced by higher variability and greater perseverative bias. In general, perseverative bias decreased with repeated trials. The discussion considers how the results support a graded-representation account, potentially explaining why children might exhibit a video deficit in some tasks but not others.

Research Highlights

• The task used a continuous search space (sandbox), making it more difficult and sensitive than spatial recall tasks used in prior video deficit research.
• Spatial recall among 4- and 5-year-old children was more variable after watching hiding events on screen via live video feed than through a window.
• Children's spatial recall from screens was more susceptible to proactive interference, evidenced by more perseverative bias in an A-not-B design.
• The results demonstrate memory representations blend experiences that accumulate over time and explain why the video deficit may be protracted for more difficult tasks.

     

The effect of learner-adapted practice schedule and task similarity on motivation and motor learning in older adults

The purpose of the present study was to investigate the effect of learner-adapted practice schedule and task similarity on intrinsic motivation and motor learning in older adults. For this purpose, 60 right-handed older adults were randomly divided into six groups of blocked-similar, learner-adapted-similar, random-similar, blocked-dissimilar, learner-adapted-dissimilar, and random-dissimilar. Sequential timing was used as the task, and the intrinsic motivation questionnaire was used for measuring individuals' motivation. The learner-adapted practice was included performing the task in a combination of blocked, serial, and random orders according to error number in each block. The results showed that the learner-adapted practice significantly outperformed than other practice schedules in motivation and motor learning measures in similar and dissimilar conditions. Also, the random schedule resulted in superior performance than the blocked schedule in similar and dissimilar conditions. These findings were discussed according to the challenge point framework.     

Reducing Proactive Interference in Motor Tasks

Abstract

Changing automatized movement patterns often leads to initial performance decrements caused by proactive interference. In this study, we scrutinized whether proactive interference could be reduced by inhibiting the to-be-changed movement pattern by means of a physical movement constraint and verbal inhibition instructions, and whether any of the two interventions may be superior. Skilled typists typed short texts as fast and accurately as possible on a regular QWERTZ keyboard. After baseline measures, a new rule prohibiting the use of the left index finger was introduced. Subsequently, participants took part in either a verbal instruction or an additional motor restriction intervention phase. Results revealed that the original rule change was successful in inducing proactive interference in skilled typists. Most importantly, the two interventions similarly reduced proactive interference both immediately following the rule change and after ten practice sessions. We conclude that reducing proactive interference by means of physical motor restrictions and verbal instructions may be equally effective.