Information capacity of the Hopfield model

The information capacity of general forms of memory is formalized. The number of bits of information that can be stored in the Hopfield model of associative memory is estimated. It is found that the asymptotic information capacity of a Hopfield network of N neurons is of the order N^3b. The number of arbitrary state vectors that can be made stable in a Hopfield network of N neurons is proved to be bounded above by N

Neural mechanisms of reactivation-induced updating that enhance and distort memory

We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tour. During scanning, participants were shown target photographs to reactivate memories from the museum tour followed by a novel lure photograph from an alternate tour. Later, participants were presented with target and lure photographs and asked to determine whether the photographs showed a stop they visited during the tour. We used a subsequent memory analysis to examine neural recruitment during reactivation that was associated with later true and false memories. We predicted that the quality of reactivation, as determined by online ratings of subjective recollection, would increase subsequent true memories but also facilitate incorporation of the lure photograph, thereby increasing subsequent false memories. The fMRI results revealed that the quality of reactivation modulated subsequent true and false memories via recruitment of left posterior parahippocampal, bilateral retrosplenial, and bilateral posterior inferior parietal cortices. However, the timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not. These data reveal the neural mechanisms recruited during memory reactivation that modify how memories will be subsequently retrieved, supporting the flexible and dynamic aspects of memory

Notion, objectifs, possibilités

Après avoir défini la notion de politique de salaires, l'auteur tente d'en expliquer les objectifs et d'identifier les moyens à employer pour la rendre efficace. Mais, en fait, on parle beaucoup de politique de salaires mais que fait-on concrètement à ce sujet 

Linkage kinematics sketchpad

During the design and creation of linkage-type mechanisms, visualization of linkage motion is extremely important. However, there does not appear to be a commercially available computer package for accomplishing visualization interactively. Most linkage design packages allow animation of linkage motion only after tedious part description (and debug) using cryptic input codes. The main thrust of this work has been the development of a prototype interactive graphics (CAD) system aimed at visualizing the motion and mobility of linkage-type mechanisms. The program is called the Linkage Kinematics Sketchpad (LKSP). It is a 2-D color graphics program which allows the user to describe a limited set of linkages (limited by a simplified kinematics analysis procedure) and interactively drive the linkage through its inherent motion cycle (or parts thereof) to visualize mobility . First, a theoretical investigation of previous work in motion analysis and display of animation is presented. This is followed by a description of the LKSP program and an evaluation of the software by this author and others more familiar with linkage design. The system design appears to be adequate, and the software is correct with linkage motions as required. As a result of this work the usefulness of this approach has been determined, and a reasonable methodology has been established. Also, problem areas have been defined, and potentially fruitful areas for future work have been identified. LKSP offers a unique approach to planar linkage design with the most desirable features being the interactive user-computer interface, the ability to create linkages with ease, and the ability to observe linkage motion and potential interference. The most commonly cited shortcoming was the limited set of linkage components which LKSP can handle. Also, there were some aspects of the motion animation which were improved as a result of the user evaluations. Suggestions for future extensions include more user control over the motion animation and more precise input of linkage dimensions