Comparisons of rats' choice behavior among three different radial-maze tasks

The present study compared rats' behavioral changes on three tasks on the radial-arm maze. In the free-choice task (0Fo/8Fr; no forced choice/eight free choices), rats performed efficiently with the simple response pattern of sequential adjacent-arm choices. In the two forced-choice tasks (3Fo/5Fr and 5Fo/3Fr), rats performed as efficiently as 0Fo/8Fr but showed no particular response patterns. The frequency of arm investigation was the highest in 5Fo/3Fr, and was higher in 3Fo/5Fr than in 0Fo/8Fr. The probability of correct rejection, avoiding re-entry to visited arms after investigation, was also higher in 3Fo/5Fr and 5Fo/3Fr than in 0Fo/8Fr. These results suggest that the rats could adjust their behavior to the task demands.     

杏仁复合体损毁对大鼠空间认知能力的影响

杏仁复合体损毁大鼠Ｍｏｒｒｉｓ迷宫作业学习成绩显著低于控制组,记忆成绩较显著低于控制组。其搜索目标时主要采用与控制组的图式策略相异的趋向式策略。策略差异提示：杏仁复合体参与大鼠空间认知的辅助加工。     

Sex differences and estropausal phase effects on water maze performance in aged rats

An age-related decline in memory has been reported in male rats; however, there are few studies that have addressed these changes in aged female rats. In young female rats, hormonal cycles influence behavior. By the age of 22 months most female rats have not had regular hormonal cycles for at least 9 months. In the current study we examined how the hormonal status (persistent estrus and pseudo-pregnant) of the aged (22-24 months) female rat (Long Evans) influenced performance on a spatial version of the Morris water maze and compared this to aged male rats. Aged females in persistent estrus showed better performance on the water maze than both aged females that were pseudopregnant and aged males. Thus, postestropausal hormonal status may influence the course of aging in females.     

The canine sand maze: an appetitive spatial memory paradigm sensitive to age-related change in dogs

Aged dogs exhibit a spectrum of cognitive abilities including a syndrome similar to Alzheimer's disease. A major impediment to research so far has been the lack of a quick and accurate test of visuospatial memory appropriate for community-based animals. We therefore report on the development and validation of the Canine Sand Maze. A 4.5-m-diameter circular pool was filled with a sand and powdered food reward mix to a depth of 10 cm. Dogs were given 4 habituation and 16 learning trials which alternated a food reward being half (control trials) or fully-buried (acquisition trials) in a fixed location. After a 90-min break, a probe trial was conducted. Cognitively normal, aged (> 8 years, n = 11) and young (1-4 years, n = 11), breed-matched dogs were compared. After correction for differences in control trials, average probe times were 2.97 and 10.81 s for young and aged dogs, respectively. In the probe trial, both groups spent significantly more time in the target quadrant but there was a trend for young dogs to cross a 1 m(2) annulus zone around the buried reward more frequently (2.6 times) than aged dogs (1.5 times). Test-retest reliability in a subset of young dogs (n = 5) was high. On the basis of these findings, the Canine Sand Maze is presented as a quick, sensitive and nonaversive tool for assessing spatial learning and reference memory in dogs.     

自适应背景焦点显示技术在遥操作中的应用

遥操作界面中可视信息的有效呈现是提高操作绩效的重要途径。本研究提出自适应背景焦点显示技术原型,构建新型遥操作显示平台,并通过比较不同显示条件下遥操作绩效,考察其应用有效性及特点。结果显示：1）相比其他显示（单一纠正信息、单一指导信息、恒定背景信息和无背景信息）,自适应背景焦点显示可有效提高操作绩效;2）在降低主观负荷方面,单一纠正信息显示显著优于其他显示。本研究结果为遥操作显示界面的优化提供了新思路。     

Force Control Is Greater in the Upper Compared With the Lower Extremity

The authors investigated whether force control is similar between the upper and lower limbs and between contractions that involve 1 or 2 joints. Six volunteers (27.5 ± 11.2 years of age) attempted to produce consistent discrete rapid force responses of 30, 60, and 90 N by using 6 different body postures, 3 with the upper and 3 with the lower limb. One of the postures for each limb involved 2 joints. The standard deviation of peak force and impulse (aggregate of the force-time curve) was significantly greater (?25%) for the lower limb than for the upper limb (p < .01). Contractions that involved 1 or 2 joints within a limb had similar variability. Therefore, the upper limb might have better control of force than the lower limb because of its extensive use in fine motor tasks in daily activities.     

Interplay of Biomechanical Constraints and Kinematic Strategies in Selecting Arm Postures

In this study, the authors examined the interplay between biomechanics and control strategies in the resolution of excess degrees of freedom at the joint level. Seven participants made aimed arm movements from 30 starting points and several starting postures to targets. Final arm postures for movements to a target exhibited substantial joint angle variation. Through regression modeling and by comparing observed final arm postures with biomechanically plausible postures, the authors identified 3 kinematic strategies: (a) Maintain deviations from the average angle at the starting point to the joint's final posture; (b) make torso rotations that are a fixed proportion of shoulder rotations; and (c) adopt a characteristic combination of 4 wrist-positioning approaches. The results demonstrated that kinematic strategies can account for substantial variance in final arm postures, if one takes into account 2 types of individual differences—those that arise inevitably from biomechanical constraints and those that reflect choices in movement strategy.     

Effect of Age and Gender in the Control of Elbow Flexion Movements

In previous studies of rapid elbow movements in young healthy men, characteristic task-dependent changes in the patterns of muscle activation when movement speed or distance was varied have been reported. In the present study, the authors investigated whether age or gender is associated with changes in the patterns of muscle activity previously reported in young men. Arm movements of 10 healthy older and 10 healthy younger participants (5 men and 5 women in each group) were studied. Surface electromyograms (EMGs) from agonist (biceps) and antagonist (triceps) muscles, kinematic and kinetic parameters, as well as anthropometric and strength measures were recorded. All 4 groups of participants showed similar task- (distance or speed) dependent changes in biphasic EMG activity. Similar modulation of the initial rate of rise of the EMG, integrated agonist and antagonist EMG activity, as well as their relative timing were observed in all 4 groups. Those results suggest that older individuals of both genders retain the control strategies for elbow movements used by young individuals. Despite the qualitative similarities in the patterns of muscle activation, the men moved more quickly than the women, and younger participants moved more quickly than older participants. Those performance differences could not be explained in terms of differences in body size and strength alone.     

Effects of Varying Load Conditions on the Organization of Postural Adjustments during Voluntary Arm Flexion

One purpose of the experiments reported here was to further clarify the effect of varying loads on postural adjustments. Another was to reevaluate whether or not the timing of electromyographic (EMG) activity in the postural muscle is preprogrammed. To accomplish these goals, we compared the effect of the presence or absence of prior knowledge of a load on the timing of EMG activity in the postural muscle (biceps femoris [BF]) with that in the focal muscle (anterior deltoid [AD]). Although the sequence of EMG activation was similar under conditions with and without a load, the timing of postural EMG activities (BFi, ipsilateral BF; BFc, contralateral BF) in associated postural adjustments was dependent on the force of arm movement, and the latencies of postural EMG activities (BFi—BFc) were dependent on the speed of arm movement. This indicates that EMG changes in the upper (focal muscle) and lower limbs (postural muscle) were triggered by different motor programs. Moreover, similar EMG activities were observed in postural muscles when the subject had advance knowledge of the presence or the absence of a load. Thus, this suggests that BFi may be centrally preprogrammed (anticipatory regulation) and BFc may be feedback regulated. Furthermore, environmental information may be a critical source of influence on those postural responses.     

How do Motor Systems Deal with the Problems of Controlling Three-Dimensional Rotations?

Rotations are fundamental to motor control, not only for orienting to stimuli but also in the joint articulations that underlie translational movements. Studying three-dimensional (3-D) rotations of the simplest joint system, the eye, has provided general insights into the neural control of movement. First, in selecting one 3-D eye orientation for each two-dimensional (2-D) gaze direction, the oculomotor system generates a behavior called Listing's law that constrains eye position to a 2-D plane, Listing's plane. This selection is made internally by an inverse kinematic transformation called the Listing's law operator. Second, the oculomotor system incorporates the inherent multiplicative relationship between rotational velocity and position to generate the 3-D movement and position commands required by Listing's law. Finally, the coordinate systems for these commands appear to align with Listing's plane rather than with anatomic structures. Recent investigations have revealed similar behavioral constraints in the orientations of the head and arm, suggesting that the neural mechanisms for Listing's law may have analogues in many motor systems.