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71.
Bays PM Flanagan JR Wolpert DM 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2005,163(3):400-405
Humans demonstrate motor learning when exposed to changes in the dynamics of movement or changes in the visuomotor map. However, when two opposing dynamic transformations are learned in succession, the memory of the first is overwritten by learning of the second; the same is true for two opposing visuomotor rotations. This retrograde interference is not seen for all combinations of transformations, however. When a dynamic transformation is learned subsequent to a visuomotor rotation, the presence or absence of interference appears to depend crucially on the structure of the dynamic task: a force-field dependent on the position of the hand produces interference, whereas an inertial load applied lateral to the hand does not. To explain these results, it has been hypothesized that two transformations can be learned without interference if they depend on two different kinematic parameters of movement (such as position and velocity of the hand). Here we demonstrate, contrary to this hypothesis, interference between a dynamic transformation that depends on the position of the hand and one that depends on its velocity. However, the interference was found to be incomplete, supporting the view that the ability to retain motor memories for different tasks depends on the degree to which their representations conflict in working memory. 相似文献
72.
A common approach to the analysis of gene expression data is to define clusters of genes that have similar expression. A critical step in cluster analysis is the determination of similarity between the expression levels of two genes. We introduce a neural network-based similarity index as a non-linear similarity index and compare the results with other proximity measures for Saccharomyces cerevisiae gene expression data. We show that the clusters obtained using Euclidean distance, correlation coefficients, and mutual information were not significantly different. The clusters formed with the neural network-based index were more in agreement with those defined by functional categories and common regulatory motifs. 相似文献
73.
In the conditioning procedure employed in this study, pigeons were trained to dip their bills into a container and then to peck either at a left or at a right key, depending on whether the container was full of distilled water or of a solution of the substance being tested. The discrimination thresholds found (from one bird each) were 2 g/l (0.034 M) for NaCl, 2 g/l (0.024 M) for NaHCO3, 1 g/l (0.013 M) for KCl, 0.5 g/l (0.005 M) for KHCO3. Following the same procedure, two birds were then faced with the choice between the solution of the known substance and of a novel one. A higher degree of discrimination was found between NaHCO3 and KHCO3 than between NaHCO3 and NaCl; in the latter case, choices appeared to be mostly based on the concentration of the two substances. 相似文献
74.
非言语型学习障碍儿童社会信息加工的特点 总被引:1,自引:0,他引:1
目的: 探讨非言语型学习障碍儿童社会信息加工特点.方法: 本研究为病例对照研究.根据确定学习障碍儿童的标准,先确定学习障碍儿童,然后对学习障碍儿童进行韦氏儿童智力测验,根据测验结果把学习障碍儿童进一步分为非言语型学习障碍组(23人)、言语型学习障碍组(28人),然后按1:1比例选取对照组(51人).设置儿童与同伴、成人相互作用的三类情景,每类情景又分为模糊和清晰两种情况,对三组儿童进行结构性访谈.结果: ①清晰权威情景下.非言语型学习障碍儿童的编码数显著低于对照组儿童[(2.35±1.15)vs.(3.25±1.27),P<0.01];对人物意图的判断,非言语型学习障碍儿童选择"恶意"的比率(65%)高于言语型学习障碍儿童(29%)(P<0.05);在工具效能感上,非言语型学习障碍儿童选择有效的比率(74%)高于言语型学习障碍儿童(36%)(P<0.05).②非言语型学习障儿童在每个情景故事下的总反应数都显著低于对照组儿童[模糊同伴加入情景:(1.17±0.49)vs.(1.09±0.86).P<0.01;清晰同伴加入情景:(1.09±0.28)vs.(1.69±0.96),P<0.01;模糊同伴激惹情景:(1.09±0.41)V8.(1.49±0.78),P<0.05;清晰同伴激惹情景:(1.17±0.49)vs.(1.65±0.95),P<0.05:模糊权威情景:(0.96±0.36)vs.(1.37±0.72),P<0.01;清晰权威情景:(1.00±0.30)vs.(1.37±0.59),P<0.01].结论: ①清晰权威情景下,非言语型学习障碍儿童编码精确性不如对照组儿童;对他人意图的判断非言语型学习障碍儿童比言语型学习障碍儿童倾向于敌意归因;非言语型学习障碍儿童比言语型学习障碍儿童工具效能感高.②在每个情景下,非言语型学习障碍儿童比对照组儿童生成策略少,反应不灵活. 相似文献
75.
Collins CJ Barnes GR 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2005,167(3):404-413
We investigated the ability to generate anticipatory smooth pursuit to sequences of constant velocity (ramp) stimuli of increasing
complexity. Previously, it was shown that repeated presentation of sequences composed of four ramps with two speeds in two
directions, evoked anticipatory smooth pursuit after only one or two presentations. Here, sequences of four or six ramps,
each having a choice of four speeds and either one or two directions (uni- or bi-directional) were examined. The components
of each sequence were presented as discrete ramps (duration: 400 ms; randomised velocity: 10–40°/s), each starting from the
centre with 1,200 ms periods of central fixation between ramps, allowing anticipatory activity to be segregated from prior
eye movement. Auditory warning cues occurred 600 ms prior to each target presentation. Anticipatory smooth eye velocity was
assessed by calculating eye velocity 50 ms after target onset (V
50), prior to the availability of visual feedback. Despite being required to re-fixate centre during inter-ramp gaps, subjects
could still generate anticipatory smooth pursuit with V
50 comparable to single speed control sequences, but with less accuracy. In the steady state V
50 was appropriately scaled in proportion to upcoming target velocity for each ramp component and thus truly predictive. Only
one to two repetitions were required to attain a steady-state for unidirectional sequences (four or six ramps), but three
or four repeats were required for bi-directional sequences. Results suggest working memory can be used to acquire multiple
levels of velocity information for prediction, but its use in rapid prediction is compromised when direction as well as speed
must be retained. 相似文献
76.
Neuromedin B (NMB) is a mammalian bombesin (BN)-like peptide that exerts its function via the neuromedin B receptor (NMB-R). The NMB/NMB-R system is involved in stress response, and therefore we examined behavioral properties in female mice lacking NMB-R using a restraint-induced stress paradigm. Thirty minutes of restraint in a wire mesh cage constituted a sufficient stress stimulus for mice as evidenced by elevated blood glucose concentrations in stressed wild-type and NMB-R-deficient mice. Using a one-trial passive avoidance test, stressed NMB-R-deficient mice exhibited a marked reduction in memory performance. NMB-R-deficient mice exhibited elevated spontaneous activity in a novel environment compared to non-stressed mutant mice after 30-min stress, and a similar difference was also observed between stressed/non-stressed wild-type mice. An elevated plus maze test showed that the stress stimulus had no effect on anxiety in either wild-type or NMB-R-deficient mice. Furthermore, pain response of wild-type and NMB-R-deficient mice induced by electric foot shock was not affected under either stressed or non-stressed conditions. These results indicate that impaired memory performance in stressed NMB-R-deficient mice is not a consequence of changes in spontaneous activity, anxiety, or pain response, and suggest that the NMB/NMB-R pathway may play a role in regulating the stress response via the neural system that controls learning and memory. 相似文献
77.
The pitch identification performance of absolute pitch possessors has previously been shown to depend on pitch range, key color, and timbre of presented tones. In the present study, the dependence of pitch identification performance on key color and timbre of musical tones was examined by analyzing hit rates, reaction times, and pupillary responses of absolute pitch possessors (n = 9) and nonpossessors (n = 12) during a pitch identification task. Results revealed a significant dependence of pitch identification hit rate but not reaction time on timbre and key color in both groups. Among absolute pitch possessors, peak dilation of the pupil was significantly dependent on key color whereas the effect of timbre was marginally significant. Peak dilation of the pupil differed significantly between absolute pitch possessors and nonpossessors. The observed effects point to the importance of learning factors in the acquisition of absolute pitch. 相似文献
78.
C.-F. Ekerot H. Jörntell M. Garwicz 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1995,106(3):365-376
The functional relation between receptive fields of climbing fibres projecting to the C1, C3 and Y zones and forelimb movements controlled by nucleus interpositus anterior via the rubrospinal tract were studied in cats decerebrated at the pre-collicular level. Microelectrode tracks were made through the caudal half of nucleus interpositus anterior. This part of the nucleus receives its cerebellar cortical projection from the forelimb areas of these three sagittal zones. The C3 zone has been demonstrated to consist of smaller functional units called microzones. Natural stimulation of the forelimb skin evoked positive field potentials in the nucleus. These potentials have previously been shown to be generated by climbing fibre-activated Purkinje cells and were mapped at each nuclear site, to establish the climbing fibre receptive fields of the afferent microzones. The forelimb movement evoked by microstimulation at the same site was then studied. The movements usually involved more than one limb segment. Shoulder retraction and elbow flexion were frequently evoked, whereas elbow extension was rare and shoulder protraction never observed. In total, movements at the shoulder and/or elbow occurred for 96% of the interpositus sites. At the wrist, flexion and extension movements caused by muscles with radial, central or ulnar insertions on the paw were all relatively common. Pure supination and pronation movements were also observed. Movements of the digits consisted mainly of dorsal flexion of central or ulnar digits. A comparison of climbing fibre receptive fields and associated movements for a total of 110 nuclear sites indicated a general specificity of the input-output relationship of this cerebellar control system. Several findings suggested that the movement evoked from a particular site would act to withdraw the area of the skin corresponding to the climbing fibre receptive field of the afferent microzones. For example, sites with receptive fields on the dorsum of the paw were frequently associated with palmar flexion at the wrist, whereas sites with receptive fields on the ventral side of the paw and forearm were associated with dorsiflexion at the wrist. Correspondingly, receptive fields on the lateral side of the forearm and paw were often associated with flexion at the elbow, whereas sites with receptive fields on the radial side of the forearm were associated with elbow extension. The proximal movements that were frequently observed also for distal receptive fields may serve to produce a general shortening of the limb to enhance efficiency of the withdrawal. It has previously been suggested that the cerebellar control of forelimb movements via the rubrospinal tract has a modular organisation. Each module would consist of a cell group in the nucleus interpositus anterior and its afferent microzones in the C1, C3 and Y zones, characterised by a homogenous set of climbing fibre receptive fields. The results of the present study support this organisational principle, and suggest that the efferent action of a module is to withdraw the receptive field from an external stimulus. Possible functional interpretations of the action of this system during explorative and reaching movements are discussed. 相似文献
79.
The present study was conducted to test Brener's calibration theory of visceral learning. It was hypothesized that training in discrimination of cephalic vasomotor responses would enhance acquisition of voluntary and biofeedback control of cephalic vasomotor response. Four groups were given discrimination training to detect either constriction, dilation, both constriction and dilation, or given false feedback. All groups were then given biofeedback training in constriction. All groups were assessed on discrimination accuracy, acquisition of biofeedback control of constriction, and voluntary control of dilation and constriction. The results indicated that discrimination of cephalic vasomotor responses can be learned and that this skill facilitates the acquisition of biofeedback and voluntary control of vasomotor responses. This facilitation occurs only if discrimination training is given for the specific response to be learned. The data suggest that discrimination of the relevant response is a necessary but not sufficient condition for acquisition of voluntary control in biofeedback learning. 相似文献
80.
Dr. Y. Fukuoka M. Noshiro H. Shindo H. Minamitani M. Ishikawa 《Medical & biological engineering & computing》1997,35(1):33-39
The nonlinearity included in the PCO
2 control system in humans is evaluated using the degree of nonlinearity based on a difference of residuals. An autoregressive
moving average (ARMA) model and neural networks (linear and nonlinear) are employed to model the system, and three types of
network (Jordan, Elman and fully interconnected) are compared. As the Jordan-type linear network cannot approximate respiratory
data accurately, the other two types and the ARMA model are used for the evaluation of the nonlinearity. The results of the
evaluation indicate that the linear assumption for the PCO
2 control system is invalid for three subjects out of seven. In particular, strong nonlinearity was observed for two subjects. 相似文献