The development of goal-directed reaching in infants: hand trajectory formation and joint torque control

Nine young infants were followed longitudinally from 4 to 15 months of age. We recorded early spontaneous movements and reaching movements to a stationary target. Time-position data of the hand (endpoint), shoulder, and elbow were collected using an optoelectronic measurement system (ELITE). We analyzed the endpoint kinematics and the intersegmental dynamics of the shoulder and elbow joint to investigate how changes in proximal torque control determined the development of hand trajectory formation. Two developmental phases of hand trajectory formation were identified: a first phase of rapid improvements between 16 and 24 weeks of age, the time of reaching onset for all infants. During that time period the number of movement units per reach and movement time decreased dramatically. In a second phase (28–64 weeks), a period of fine-tuning of the sensorimotor system, we saw slower, more gradual changes in the endpoint kinematics. The analysis of the underlying intersegmental joint torques revealed the following results: first, the range of muscular and motiondependent torques (relative to body weight) did not change significantly with age. That is, early reaching was not confined by limitations in producing task-adequate levels of muscular torque. Second, improvements in the endpoint kinematics were not accomplished by minimizing amplitude of muscle and reactive torques. Third, the relative timing of muscular and motion-dependent torque peaks showed a systematic development toward an adult timing profile with increasing age. In conclusion, the development toward invariant characteristics of the hand trajectory is mirrored by concurrent changes in the control of joint forces. The acquisition of stable patterns of intersegmental coordination is not achieved by simply regulating force amplitude, but more so by modulating the correct timing of joint force production and by the system's use of reactive forces. Our findings support the view that development of reaching is a process of unsupervised learning with no external or innate teacher prescribing the desired kinematics or kinetics of the movement.     

Operant Conditioning of Heart Rate: Somatic Correlates

The relationships between heart rate (HR) and several parameters of somatic activity were evaluated in human subjects when shuck avoidance was made contingent on either increases or decreases in HR. In order to depict any influence of the contingency specific 10 HR, somatic activity was controlled to varying degrees by instructions and the use of non-contingent control groups. When increases in HR were reinforced, the contingency we found to influence somatic activity but an effect specific to HR was also observed. When decreases in HR were reinforced, there was no evidence that HR were influenced independently of somatic activity. The result are discussed with respect to several current issues.     

老年学习记忆减退大鼠齿状回突触的定量研究

据老年大鼠在Ｍｏｒｒｉｓ水迷宫中的行为表现，将其分为老年学习记忆减退和学习记忆正常两部分，采用透射电镜观察、拍片，对齿状回中分子层触的数量和大小进行体视学定量分析。     

Mutations in raised Drosophila melanogaster affect experience-dependent aspects of sexual behavior in both sexes

Many aspects of the reproductive behavior of Drosophila melanogaster are modified dramatically by experience and age. Males' courtship of immature males and fertilized females decreases over time. Females' receptivity to copulation, and the behaviors that females perform and elicit, are affected by their age and sexual experience. We show that mutations in a raised stock affect all of these age- and experience-dependent aspects of male and female sexual behavior. Experience has no effect on raised males' courtship of immature males and has opposite effects on raised and wild-type males' courtship of fertilized females. In comparison to controls, raised females become sexually mature at an earlier age, and sexually mature raised virgin females copulate more quickly. Following mating, raised females elicit more courtship and remate faster and more frequently than control females.     

A selective modulation of the olfactory bulb electrical activity in relation to the learning of palatability in hungry and satiated rats

We attempted to determine whether a neutral odor which had become palatable as a result of learning had also acquired the property of activating the mitral cells of the olfactory bulb of hungry rats to the same extent as the odor of their usual nutriment. Male Wistar rats have been accustomed for various times to eat, during a single daily meal, exclusively a synthetic diet, either flavoured or not with eucalyptol. The mitral cell multiunit electrical activity was recorded in chronically implanted hungry and satiated animals. It was shown that: (1) in the rats having received the flavoured diet for one month when grown up, eucalyptol behaved as a nonalimentary odor towards mitral cells; (2) in the rats having received the flavoured diet (already given to the mothers) from weaning to the test period, eucalyptol behaved as a food odor at the mitral cell level, but amyl acetate, a control odor, did not activate mitral cells in hungry animals; (3) the odor of the diet with or without eucalyptol activated mitral cells at first in hungry rats, and this property was reinforced, for either diet, by its consumption beginning early and maintained continuously. It was concluded that palatability is dynamically related to the animal's previous experience, and that its modifications induce various degrees of mitral activation in hungry rats. This property allowed an electrophysiological measure of odor palatability to be proposed. The results are discussed in relation to the behavioral and neurophysiological maturation of animals.     

Open-field behavior, habituation and passive avoidance learning: Effect of ACTH and hydrocortisone on Normal and adrenalectomized rats

Exploratory behavior (GMA) and habituation rate (IH) were studied in an open-field situation in normal and adrenalectomized rats. Following this procedure the rats were subjected to passive avoidance learning (PA). Wide-spreading individual differences were observed in the exploratory behavior and the tendency of habituation of normal rats. As compared to the normal values, either the adrenalectomy which was performed 24 hr, 7 days and 28 days prior to the experiments or the ACTH and hydrocortisone treatment failed to modify the GMA and the IH significantly. An improvement of PA was found in the normal rats following ACTH and hydrocortisone treatment. In the adrenalectomized animals the hydrocortisone proved to be effective, whereas ACTH did not influence PA. No correlation was found between GMA, IH versus PA values and the influence of ACTH and hydrocortisone administration on these parameters. It is concluded that the direction of PA is unpredictable on the basis of the open-field test performed on R-Amsterdam strain of rats, and the effect of ACTH on passive avoidance learning is mediated through the adrenal glands.     

Effects of combined entorhinal cortex-hippocampal lesions on locomotor behavior, spontaneous alternation and spatial maze learning in the rat

Male Sprague-Dawley rats with combined lesions to the dorsal and lateral aspects of the entorhinal cortex in one hemisphere and of the contralateral dorsolateral hippocampal formation were compared with both operated and unoperated controls on three different behaviors, monitored across a 53 day postoperative period. The rats with the combined entorhinal cortex-hippocampal lesions (EH) showed transient hyperactivity in the open field, transient reduction in spontaneous alternation levels in an unbaited T-maze and persistent deficits in learning spatial maze problems. The results of the present experiment are discussed in comparison with those from experiments on rats with bilateral hippocampal lesions and those from experiments on rats with bilateral entorhinal cortex lesions. Although some similarities among these findings suggest that these two brain regions probably function in a coordinated fashion with respect to these behaviors, differences in the various syndromes are also discussed.     

Hypothermic Machine Preservation in Liver Transplantation Revisited: Concepts and Criteria in the New Millennium

To overcome the present shortage of liver donors by expansion of the existing donor pool and possibly lengthening of the storage time, hypothermic machine perfusion of the liver as a dynamic preservation method is revisited. The three most important aspects are defined to be the type of preservation solution, the characteristics of perfusion dynamics, and the oxygen supply. Reviewing hypothermic liver machine perfusion experiments, the University of Wisconsin machine preservation solution is the solution most used. It is also found that nothing conclusive can be said about the optimal perfusion characteristics, since either perfusion pressure or perfusion flow is reported. The best estimation is perfusion of the liver in a physiological manner, i.e. pulsatile arterial perfusion and continuous portal venous perfusion. The applied pressures could be chosen to be somewhat lower than physiological pressures to prevent possible endothelial cell damage. Oxygen supply is necessary to achieve optimal preservation of the liver. The minimal amount of partial oxygen pressure required is inversely related to the normalized flow. Incorporating these features in a system based on existing standard surgical and organ sharing procedures and which is able to work stand-alone for 24 h, weighing less than 23 kg, could successfully implement this technique into every day clinical practise.     

Differentiating molecular etiologies of Angelman syndrome through facial phenotyping using deep learning

Angelman syndrome (AS) is caused by several genetic mechanisms that impair the expression of maternally‐inherited UBE3A through deletions, paternal uniparental disomy (UPD), UBE3A pathogenic variants, or imprinting defects. Current methods of differentiating the etiology require molecular testing, which is sometimes difficult to obtain. Recently, computer‐based facial analysis systems have been used to assist in identifying genetic conditions based on facial phenotypes. We sought to understand if the facial‐recognition system DeepGestalt could find differences in phenotype between molecular subtypes of AS. Images and molecular data on 261 individuals with AS ranging from 10 months through 32 years were analyzed by DeepGestalt in a cross‐validation model with receiver operating characteristic (ROC) curves generated. The area under the curve (AUC) of the ROC for each molecular subtype was compared and ranked from least to greatest differentiable phenotype. We determined that DeepGestalt demonstrated a high degree of discrimination between the deletion subtype and UPD or imprinting defects, and a lower degree of discrimination with the UBE3A pathogenic variants subtype. Our findings suggest that DeepGestalt can recognize subclinical differences in phenotype based on etiology and may provide decision support for testing.