Role of entorhinal cortical plasticity in spatial and contextual memory

It is well accepted that the hippocampus (HIP) is important for spatial and contextual memories, however, it is not clear if the entorhinal cortex (EC), the main input/output structure for the hippocampus, is also necessary for memory storage. Damage to the EC in humans results in memory deficits. However, animal studies report conflicting results on whether the EC is necessary for spatial and contextual memory. Memory consolidation requires gene expression and protein synthesis, mediated by signaling cascades and transcription factors. Extracellular-signal regulated kinase (ERK) cascade activity is necessary for long-term memory in several tasks, including those that test spatial and contextual memory. In this work, we explore the role of ERK-mediated plasticity in the EC on spatial and contextual memory. ^ To evaluate this role, post-training infusions of reversible pharmacological inhibitors specific for the ERK cascade that do not affect normal neuronal activity were targeted directly to the EC of awake, behaving animals. This technique provides spatial and temporal control over the inhibition of the ERK cascade without affecting performance during training or testing. Using the Morris water maze to study spatial memory, we found that ERK inhibition in the EC resulted in long-term memory deficits consistent with a loss of spatial strategy information. When animals were allowed to learn and consolidate a spatial strategy for solving the task prior to training and ERK inhibition, the deficit was alleviated. To study contextual memory, we trained animals in a cued fear-conditioning task and saw an increase in the activation of ERK in the EC 90 minutes following training. ERK inhibition in the EC over this time point, but not at an earlier time point, resulted in increased freezing to the context, but not to the tone, during a 48-hour retention test. In addition, animals froze maximally at the time the shock was given during training; similar to naïve animals receiving additional training, suggesting that ERK-mediated plasticity in the EC normally suppresses the temporal nature of the freezing response. These findings demonstrate that plasticity in the EC is necessary for both spatial and contextual memory, specifically in the retention of behavioral strategies. ^

Exploring parents' memories of their child's death related sensory experiences as a dimension of grieving

Little is known about how dying children and their parents experience death. Dying children have reported death related sensory experiences (DRSEs), defined as seeing or hearing someone or something not visible or audible to others, associated with dying. Although parents report that they and the dying child benefit from these experiences, healthcare providers often unknowingly dismiss them. The aims of this phenomenological inquiry were to describe children's DRSEs and their meaning from the parents' perspectives. Four fathers and six mothers of African American, Caucasian, or Hispanic ethnicity, all Christian, ranging in age from 35 to 59 years, whose child died 23 to 52 months prior and was treated at a children's cancer center, were interviewed in the home or hospital setting of their choice. Children's ages at the time of their death ranged from 4 to 13 years. A modification of van Kaarn's phenomenological method of analysis was used to analyze data. Themes emerging from the data for the first aim were: perceiving someone or something from a spiritual realm others could not, expressing awareness tempered by parental reactions, and embracing transcendence. Themes emerging from the data for the second aim were: spiritual beings prepared child; child revealed reality, preparing parents; and child transcended wholly, easing parents' grief. Post-interview surveys revealed that parents found participating in this study a "very positive" or "positive" experience, particularly being able to tell the story of their child. Children's DRSEs have clinical implications for all who provide care near the end of life. Informing parents of DRSEs, cautioning that not all dying children express them, may help parents to anticipate this phenomenon, which may decrease anxiety when their child expresses them, increasing the opportunity for open dialogue between parent and child about dying and death, and decrease regrets associated with being unreceptive to their child's expressions of death awareness. Validating a child's DRSE can have profound effects on bereaved parents. Examining DRSEs from the child's perspective and the influence of informing parents of DRSEs on the dying experience of the child and the parental grieving process are recommended. ^

El uso de la poesía en la tradición oral moderna

En todos los pueblos el origen de la creación, al interior de las distintas religiones y dentro del universo entero, se manifiesta por la palabra, a la que se considera la fuerza genérica, de origen divino, fundadora y productora de todas las cosas tanto materiales como espirituales. La voz se equipara a la emisión de un soplo milagroso. Nombrar es un acto de creación; crear y nombrar, entonces, se convierten en sinónimos: "en el principio era el Verbo y el Verbo era Dios". Sobre esas antiguas creencias se generaron mitos, se conformaron relatos legendarios y nacieron fórmulas de comunicación. Las culturas indígenas conservan hermosas leyendas entregadas por la tradición oral; recuerdo de ideales épocas y "tiempo de los sueños": la edad de la poesía. Poesía que transmite historia y mitos; cantos que permiten investigar y mantener la inteligencia activa: la permanencia de la memoria genética

El uso de la poesía en la tradición oral moderna

En todos los pueblos el origen de la creación, al interior de las distintas religiones y dentro del universo entero, se manifiesta por la palabra, a la que se considera la fuerza genérica, de origen divino, fundadora y productora de todas las cosas tanto materiales como espirituales. La voz se equipara a la emisión de un soplo milagroso. Nombrar es un acto de creación; crear y nombrar, entonces, se convierten en sinónimos: "en el principio era el Verbo y el Verbo era Dios". Sobre esas antiguas creencias se generaron mitos, se conformaron relatos legendarios y nacieron fórmulas de comunicación. Las culturas indígenas conservan hermosas leyendas entregadas por la tradición oral; recuerdo de ideales épocas y "tiempo de los sueños": la edad de la poesía. Poesía que transmite historia y mitos; cantos que permiten investigar y mantener la inteligencia activa: la permanencia de la memoria genética

El uso de la poesía en la tradición oral moderna

En todos los pueblos el origen de la creación, al interior de las distintas religiones y dentro del universo entero, se manifiesta por la palabra, a la que se considera la fuerza genérica, de origen divino, fundadora y productora de todas las cosas tanto materiales como espirituales. La voz se equipara a la emisión de un soplo milagroso. Nombrar es un acto de creación; crear y nombrar, entonces, se convierten en sinónimos: "en el principio era el Verbo y el Verbo era Dios". Sobre esas antiguas creencias se generaron mitos, se conformaron relatos legendarios y nacieron fórmulas de comunicación. Las culturas indígenas conservan hermosas leyendas entregadas por la tradición oral; recuerdo de ideales épocas y "tiempo de los sueños": la edad de la poesía. Poesía que transmite historia y mitos; cantos que permiten investigar y mantener la inteligencia activa: la permanencia de la memoria genética

Decoding urban landscapes through the analysis of place names and imaginaries at a local scale.

Toponomastics is increasingly interested in the subjective role of place names in quotidian life. In the frame of Urban Geography, the interest in this matter is currently growing, as the recently change in modes of habitation has urged our discipline to find new ways of exploring the cities. In this context, the study of how name's significance is connected to a urban society constitutes a very interesting approach. We believe in the importance of place names as tools for decoding urban areas and societies at a local-scale. This consideration has been frequently taken into account in the analysis of exonyms, although in their case they are not exempt of political and practical implications that prevail over the tool function. The study of toponomastic processes helps us understanding how the city works, by analyzing the liaison between urban landscape, imaginaries and toponyms which is reflected in the scarcity of some names, in the biased creation of new toponyms and in the pressure exercised over every place name by tourists, residents and local government for changing, maintaining or eliminating them. Our study-case, Toledo, is one of the oldest cities in Spain, full of myths, stories and histories that can only be understood combined with processes of internal evolution of the city linked to the arrival of new residents and the more and more notorious change of its historical landscape. At a local scale, we are willing to decode the information which is contained in its toponyms about its landscape and its society.

Mesh traversal and sorting for efficient memory usage in scientific codes

Applications that operate on meshes are very popular in High Performance Computing (HPC) environments. In the past, many techniques have been developed in order to optimize the memory accesses for these datasets. Different loop transformations and domain decompositions are com- monly used for structured meshes. However, unstructured grids are more challenging. The memory accesses, based on the mesh connectivity, do not map well to the usual lin- ear memory model. This work presents a method to improve the memory performance which is suitable for HPC codes that operate on meshes. We develop a method to adjust the sequence in which the data are used inside the algorithm, by means of traversing and sorting the mesh. This sorted mesh can be transferred sequentially to the lower memory levels and allows for minimum data transfer requirements. The method also reduces the lower memory requirements dra- matically: up to 63% of the L1 cache misses are removed in a traditional cache system. We have obtained speedups of up to 2.58 on memory operations as measured in a general- purpose CPU. An improvement is also observed with se- quential access memories, where we have observed reduc- tions of up to 99% in the required low-level memory size.

Explointing FPGA block memories for protected cryptographic implementations

Modern Field Programmable Gate Arrays (FPGAs) are power packed with features to facilitate designers. Availability of features like huge block memory (BRAM), Digital Signal Processing (DSP) cores, embedded CPU makes the design strategy of FPGAs quite different from ASICs. FPGA are also widely used in security-critical application where protection against known attacks is of prime importance. We focus ourselves on physical attacks which target physical implementations. To design countermeasures against such attacks, the strategy for FPGA designers should also be different from that in ASIC. The available features should be exploited to design compact and strong countermeasures. In this paper, we propose methods to exploit the BRAMs in FPGAs for designing compact countermeasures. BRAM can be used to optimize intrinsic countermeasures like masking and dual-rail logic, which otherwise have significant overhead (at least 2X). The optimizations are applied on a real AES-128 co-processor and tested for area overhead and resistance on Xilinx Virtex-5 chips. The presented masking countermeasure has an overhead of only 16% when applied on AES. Moreover Dual-rail Precharge Logic (DPL) countermeasure has been optimized to pack the whole sequential part in the BRAM, hence enhancing the security. Proper robustness evaluations are conducted to analyze the optimization for area and security.

Star dust memories, or how to detect allergen traces in powder foods

Allergies and food intolerances are at the forefront of institutional interest (European Regulation No 1169/2011) for their impact on consumer health. Allergies to peanuts and other nuts and gluten intolerance, makes production processes involving mixtures of powders a great concern for the industry, given the need to indicate the existence of traces of any of them. The food industry requires non-destructive and non-invasive methods of quantification that meet sensitivity requirements but also specificity levels. Optical methods such as NIR spectrophotometry or hyper-spectral image are currently some of the technologies that show potential success. This is the context of this paper that evaluates how to use NIR spectroscopy (900-1600nm) to detect traces of 15 different kinds of nuts and 20 other flours.

Long-term potentiation and dual-component quantal signaling in the dentate gyrus

Long-term potentiation (LTP) of excitatory transmission is an important candidate cellular mechanism for the storage of memories in the mammalian brain. The subcellular phenomena that underlie the persistent increase in synaptic strength, however, are incompletely understood. A potentially powerful method to detect a presynaptic increase in glutamate release is to examine the effect of LTP induction on the rate at which the use-dependent blocker MK-801 attenuates successive N-methyl-d-aspartic acid (NMDA) receptor-mediated synaptic signals. This method, however, has given apparently contradictory results when applied in hippocampal CA1. The inconsistency could be explained if NMDA receptors were opened by glutamate not only released from local presynaptic terminals, but also diffusing from synapses on neighboring cells where LTP was not induced. Here we examine the effect of pairing-induced LTP on the MK-801 blocking rate in two afferent inputs to dentate granule cells. LTP in the medial perforant path is associated with a significant increase in the MK-801 blocking rate, implying a presynaptic increase in glutamate release probability. An enhanced MK-801 blocking rate is not seen, however, in the lateral perforant path. This result still could be compatible with a presynaptic contribution to LTP in the lateral perforant path if intersynaptic cross-talk occurred. In support of this hypothesis, we show that NMDA receptors consistently sense more quanta of glutamate than do α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors. In the medial perforant path, in contrast, there is no significant difference in the number of quanta mediated by the two receptors. These results support a presynaptic contribution to LTP and imply that differences in intersynaptic cross-talk can complicate the interpretation of experiments designed to detect changes in transmitter release.

Increased discrimination of “false memories” in autism spectrum disorder

Individuals with autism spectrum disorder (ASD) have impaired ability to use context, which may manifest as alterations of relatedness within the semantic network. However, impairment in context use may be more difficult to detect in high-functioning adults with ASD. To test context use in this population, we examined the influence of context on memory by using the “false memory” test. In the false memory task, lists of words were presented to high-functioning subjects with ASD and matched controls. Each list consists of words highly related to an index word not on the list. Subjects are then given a recognition test. Positive responses to the index words represent false memories. We found that individuals with ASD are able to discriminate false memory items from true items significantly better than are control subjects. Memory in patients with ASD may be more accurate than in normal individuals under certain conditions. These results also suggest that semantic representations comprise a less distributed network in high-functioning adults with ASD. Furthermore, these results may be related to the unusually high memory capacities found in some individuals with ASD. Research directed at defining the range of tasks performed superiorly by high-functioning individuals with ASD will be important for optimal vocational rehabilitation.

Memory systems in the brain and localization of a memory

It is now clear that there are a number of different forms or aspects of learning and memory that involve different brain systems. Broadly, memory phenomena have been categorized as explicit or implicit. Thus, explicit memories for experience involve the hippocampus–medial temporal lobe system and implicit basic associative learning and memory involves the cerebellum, amygdala, and other systems. Under normal conditions, however, many of these brain–memory systems are engaged to some degree in learning situations. But each of these brain systems is learning something different about the situation. The cerebellum is necessary for classical conditioning of discrete behavioral responses (eyeblink, limb flexion) under all conditions; however, in the “trace” procedure where a period of no stimuli intervenes between the conditioned stimulus and the unconditioned stimulus the hippocampus plays a critical role. Trace conditioning appears to provide a simple model of explicit memory where analysis of brain substrates is feasible. Analysis of the role of the cerebellum in basic delay conditioning (stimuli overlap) indicates that the memories are formed and stored in the cerebellum. The phenomenon of cerebellar long-term depression is considered as a putative mechanism of memory storage.

Illusory memories: A cognitive neuroscience analysis

Memory illusions and distortions have long been of interest to psychology researchers studying memory, but neuropsychologists and neuroscientists have paid relatively little attention to them. This article attempts to lay the foundation for a cognitive neuroscience analysis of memory illusions and distortions by reviewing relevant evidence from a patient with a right frontal lobe lesion, patients with amnesia produced by damage to the medial temporal lobes, normal aging, and healthy young volunteers studied with functional neuroimaging techniques. Particular attention is paid to the contrasting roles of prefrontal cortex and medial temporal lobe structures in accurate and illusory remembering. Converging evidence suggests that the study of illusory memories can provide a useful tool for delineating the brain processes and systems involved in constructive aspects of remembering.

Recruitment and replacement of hippocampal neurons in young and adult chickadees: an addition to the theory of hippocampal learning.

We used [3H]thymidine to document the birth of neurons and their recruitment into the hippocampal complex (HC) of juvenile (4.5 months old) and adult blackcapped chickadees (Parus atricapillus) living in their natural surroundings. Birds received a single dose of [3H]thymidine in August and were recaptured and killed 6 weeks later, in early October. All brains were stained with Cresyl violet, a Nissl stain. The boundaries of the HC were defined by reference to the ventricular wall, the brain surface, or differences in neuronal packing density. The HC of juveniles was as large as or larger than that of adults and packing density of HC neurons was 31% higher in juveniles than in adults. Almost all of the 3H-labeled HC neurons were found in a 350-m-wide layer of tissue adjacent to the lateral ventricle. Within this layer the fraction of 3H-labeled neurons was 50% higher in juveniles than in adults. We conclude that the HC of juvenile chickadees recruits more neurons and has more neurons than that of adults. We speculate that juveniles encounter greater environmental novelty than adults and that the greater number of HC neurons found in juveniles allows them to learn more than adults. At a more general level, we suggest that (i) long-term learning alters HC neurons irreversibly; (ii) sustained hippocampal learning requires the periodic replacement of HC neurons; (iii) memories coded by hippocampal neurons are transferred elsewhere before the neurons are replaced.

Face encoding and recognition in the human brain.

A dissociation between human neural systems that participate in the encoding and later recognition of new memories for faces was demonstrated by measuring memory task-related changes in regional cerebral blood flow with positron emission tomography. There was almost no overlap between the brain structures associated with these memory functions. A region in the right hippocampus and adjacent cortex was activated during memory encoding but not during recognition. The most striking finding in neocortex was the lateralization of prefrontal participation. Encoding activated left prefrontal cortex, whereas recognition activated right prefrontal cortex. These results indicate that the hippocampus and adjacent cortex participate in memory function primarily at the time of new memory encoding. Moreover, face recognition is not mediated simply by recapitulation of operations performed at the time of encoding but, rather, involves anatomically dissociable operations.