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191.
Neuronal changes in normal human aging and Alzheimer's disease 总被引:8,自引:0,他引:8
This article discusses age-related changes in brain weight, total number of cortical neurons, cortical dendrites, spine, and synapse density. The conclusion is that the present outlook is less grim than it was 30 years ago. Age-related reduction appears to be specific to brain region and cortical layer rather than a general feature. In addition, we describe a different pattern of changes that occur in Alzheimer's disease patients. This review concludes that the association cortices in particular are affected in aging and Alzheimer's disease and that the primary visual and somatosensory cortices are relatively spared. 相似文献
192.
The primary purpose of the study was to identify event-based prospective-memory tasks that provide sensitive and reliable tools for assessing effects of normal aging in prospective-memory performance. Four prospective-memory tasks were selected from the literature or were newly developed, with the tasks differing on various dimensions that, for theoretical reasons or based on previous evidence, might determine task sensitivity to age effects on prospective-memory performance: perceptual saliency of prospective target events, frequency of occurrence of prospective target events, complexity of prospective-memory instructions, and provision of feedback after prospective-memory errors. Two of the four tasks yielded large and robust age effects on prospective-memory performance. Correlational analyses suggested that these age effects on prospective-memory performance were mediated, at least in part, by a reduced ability of older adults to maintain prospective intentions in a highly activated state and not by age effects on basic mental speed alone. 相似文献
193.
A limitation of a simple linear mass-spring model in describing goal directed movements is that it generates rather slow movements when the parameters are kept within a realistic range. Does this imply that the control of fast movements cannot be approximated by a linear system? In servo-control theory, it has been proposed that an optimal controller should control movement velocity in addition to position. Instead of explicitly controlling the velocity, we propose to modify a simple linear mass-spring model. We replaced the damping relative to the environment (absolute damping) with damping with respect to the velocity of the equilibrium point (relative damping). This gives the limb a tendency to move as fast as the equilibrium point. We show that such extremely simple models can generate rapid single-joint movements. The resulting maximal movement velocities were almost equal to those of the equilibrium point, which provides a simple mechanism for the control of movement speed. We further show that peculiar experimental results, such as an 'N-shaped' equilibrium trajectory and the difficulties to measure damping in dynamic conditions, may result from fitting a model with absolute damping where one with relative damping would be more appropriate. Finally, we show that the model with relative damping can be used to model subtle differences between multi-joint interceptions. The model with relative damping fits the data much better than a version of the model with absolute damping. 相似文献
194.
Gender is a dimension of face recognition 总被引:1,自引:0,他引:1
Baudouin JY Tiberghien G 《Journal of experimental psychology. Learning, memory, and cognition》2002,28(2):362-365
In an experiment, the authors investigated the impact of gender categorization on face recognition. Participants were familiarized with composite androgynous faces labeled with either a woman's first name (Mary) or a man's first name (John). The results indicated that participants more quickly eliminated faces of the opposite gender than faces of the same gender than the face they were looking for. This gender effect did not result from greater similarity between faces of the same gender. Rather, early gender categorization of a face during face recognition appears to speed up the comparison process between the perceptual input and the facial representation. Implications for face recognition models are discussed. 相似文献
195.
The topic of amodal completion has often been investigated by using partly occluded shapes that are regular. In research that has typically been done with displays such as these regular shapes, it has been shown that global aspects of a shape can determine completion. To see how robust these global influences in the completion process are, we investigated quasi-regular shapes, ie shapes with a certain overall regularity but not based on metrical identities. First, in experiment 1 participants had to complete quasi-regular shapes in a drawing task. Then, in experiment 2 the primed-matching paradigm was used. Results from both experiments provided evidence for global completions. In experiment 3 we found that multiple global completions can be primed, which, as a control experiment showed, cannot be explained by some inability of the visual system to see the difference between the different completions. These data support the notion that global influences on visual occlusion are apparent even when the partly occluded stimulus is outside the domain of regular shapes. Implications for a global approach are provided. 相似文献
196.
Jean Claude Rouchy 《Group》2002,26(3):205-217
Research into the cultural foundations of psychic structure must take place simultaneously at the individual, group, and psychosocial level of analysis. Identity, as both an individual and a collective phenomenon, and the primacy of the group dimension become manifest in the imaginary space created by groups, in Bion's protomental system. Cultural incorporates function like somatic processes and establish the synchrony of all cultural interactions. Individuation would thus emerge from the shared common base, which in turn is related to the individual's internalization of his group of belonging. A distinction is drawn between primary groups of belonging, which are extensions of family structure and supply the group's cultural identity, and secondary belonging groups, which are instituted by the society. The relationship between transcultural experiences, aiming at achieving unity, and intercultural experiences, which recognize limits and differences, is a source of tension for the individual and the group. Examples are given of the function of excitation screens within instituted groups and of the cultural dimension of the analytic setting. 相似文献
197.
Hysterectomy (the surgical removal of the uterus) precipitates the end of menstrual cycles in premenopausal women. In this article I explore whether that premature termination of menstrual function negatively affects women's subjective gender identities. Using the grounded theory research approach, I conducted in-depth interviews with 40 diverse respondents who had undergone premenopausal hysterectomy. These women generally acknowledged that, since the time of menarche, they had closely associated menstruation with their gender identities. However, despite some regrets, respondents' primary reaction was almost unanimous relief that they had ceased menstruating. This finding must be viewed in the context of overwhelming and uncontrollable menstrual pain and bleeding that many respondents had previously experienced. Contrary to expressing remorse that they no longer identified with normal women, who menstruate, most respondents sought to disassociate themselves from the normalized suffering that they perceived is endured by all menstruating women. 相似文献
198.
199.
van de Grind W 《Consciousness and cognition》2002,11(2):241-64; discussion 308-13
The conclusions drawn by Benjamin Libet from his work with colleagues on the timing of somatosensorial conscious experiences has met with a lot of praise and criticism. In this issue we find three examples of the latter. Here I attempt to place the divide between the two opponent camps in a broader perspective by analyzing the question of the relation between physical timing, neural timing, and experiential (mental) timing. The nervous system does a sophisticated job of recombining and recoding messages from the sensorial surfaces and if these processes are slighted in a theory, it might become necessary to postulate weird operations, including subjective back-referral. Neuroscientifically inspired theories are of necessity still based on guesses, extrapolations, and philosophically dubious manners of speech. They often assume some neural correlate of consciousness (NCC) as a part of the nervous system that transforms neural activity in reportable experiences. The majority of neuroscientists appear to assume that the NCC can compare and bind activity patterns only if they arrive simultaneously at the NCC. This leads to a search for synchrony or to theories in terms of the compensation of differences in neural delays (latencies). This is the main dimension of the Libet discussion. Examples from vision research, such as "temporal-binding-by-synchrony" and the "flash-lag" effect, are then used to illustrate these reasoning patterns in more detail. Alternatively one could assume symbolic representations of time and space (symbolic "tags") that are not coded in their own dimension (not time in time and space in space). Unless such tags are multiplexed with the quality message (tickle, color, or motion), one gets a binding problem for tags. One of the hidden aspects of the discussion between Libet and opponents appears to be the following. Is the NCC smarter than the rest of the nervous system, so that it can solve the problems of local sign (e.g., "where is the event"?) and timing (e.g., "when did it occur?" and "how long did it last?") on its own, or are these pieces of information coded symbolically early on in the system? A supersmart NCC appears to be the assumption of Libet's camp (which includes Descartes, but also mystics). The wish to distribute the smartness evenly across all stages of processing in the nervous system (smart recodings) appears to motivate the opponents. I argue that there are reasons to side with the latter group. 相似文献
200.