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Results for “memory differentiation”

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At least 1,117 records · Page 62Linked to original sources
PubMed2005

Differential components of sentence comprehension: beyond single word reading and memory.

A number of studies have used functional neuroimaging to examine the neural mechanisms of sentence comprehension; however, few fMRI studies have examined activation patterns associated with sentence comprehension after accounting for activation attributable to single-word-level tasks important for sentence comprehension. To investigate the patterns of activation associated with sentence comprehension after controlling for single word reading and maintaining single words in memory, 20 unimpaired adult readers completed a block design paradigm which included sentence comprehension, single word reading, and short-term memory (for words) tasks. Results indicated that, regardless of the aspect of sentence comprehension being controlled for, activation was observed in bilateral temporal lobes (left > right) as well as bilateral occipital lobes and middle frontal gyri. Additional findings showed that bilateral superior parietal lobe activation was greatest for short-term memory for words, while left anterior inferior frontal gyri activation (centered around Brodmann's area 47) was greatest for single word reading. Results suggest that temporal cortex (left > right) is a core region important for sentence comprehension beyond the short-term memory and semantic requirements inherent in processing sentences.

Adult↗
PubMed2006

Differential effects of haloperidol, clozapine and olanzapine on learning and memory functions in mice.

Many schizophrenic patients exhibit impairments in neurocognitive functions. Typical antipsychotic drugs such as haloperidol, have limited or even detrimental influence on cognitive functions. In contrast, atypical antipsychotic drugs, such as clozapine and olanzapine, may improve memory function in schizophrenics. However, only a few studies have been conducted to directly compare the effects of olanzapine, clozapine and haloperidol on memory functions in animal models. Thus, their effects on this issue were investigated in the present studies by using one-way step-through passive avoidance task and Morris water maze as models of learning and memory. The results showed that olanzapine did not affect acquisition, consolidation or retrieval process in step-through test. Moreover, it improved spatial learning function in mice in Morris water maze task. Clozapine and haloperidol appeared to impair acquisition process and consolidation process, respectively, in step-through test. Both drugs impaired spatial learning function in mice in Morris water maze task. The results suggested a positive implication for the clinical medication of olanzapine in schizophrenic treatment.

Animals↗
PubMed1983

Left hemispheric advantage for a visuopatial-dichaptic matching task.

Twenty right handed, female subjects performed a visuospatial-dichaptic matching task which required them to view a single shape for a brief period of time while palpating two shapes, one in each hand. There was an identification and reaction time advantage for right hand responses, which allowed the inference of a left hemispheric advantage for this particular matching task. These results are discussed in reference to factors that may modify the typical right hemispheric superiority for the processing of spatial information, i.e., motor feedback, concurrent memory load, and the differential use of spatial cues.

Discrimination Learning↗
PubMedDate not supplied

Cognitive and brain imaging measures of Alzheimer's disease.

Diagnosis of Alzheimer's disease (AD) during life relies upon clinical and neurobehavioral symptoms but is presumptive without microscopic verification of neuropathology. Studies in this review observed considerable heterogeneity in AD symptoms and did not agree on how to detect the earliest symptoms. Problems exist in diagnosis. Differences in symptoms and diagnosis result from how AD is defined neurobehaviorally and on the model used for description. The studies reviewed have been considered under three basic models: A severity (staging) model; a heterogeneity (subtyping) model; and an information processing model. Differences in model intent have resulted in differences in disease description. Brain imaging measures have not invalidated models but add the neural substrate needed to examine correlation of measures within each model.

Aged↗
PubMed2003

The Seiji memorial lecture: the melanosome: an ideal model to study cellular differentiation.

Melanosomes provide an intriguing model for study at many levels. In part this is due to their unique structure and function, but also in part to their involvement in pigmentary diseases and as a model to study basic cellular mechanisms of organelle biogenesis. Recent studies have elucidated the full proteome of the melanosome and the metabolic and molecular lesions involved in a number of pigmentary diseases have been resolved. This paper summarizes recent advances in the field in these areas.

Animals↗
PubMed1992

Improving recall by recoding interfering material at the time of retrieval.

Our experiments demonstrate that interference of an interpolated list of items with recall of an original list can be substantially reduced by forming Ss just before testing how to reorganize and simplify the interpolated material. In Experiments 1 and 2, Ss better recalled an initial serial list of letters when informed at testing that an interpolated list spelled a certain phrase backward. Similarly, in Experiments 3 and 4, Ss better recalled an initial list of cities when told that the interpolated cities were also names of former U.S. presidents. Control experiments rule out several simple explanations. In contrast to an editing hypothesis, the postorganizing clue helped recall even when problems of list differentiation were minimized. Current memory models appear unable to explain this benefit of a postlearning clue that enables Ss to segregate the interpolated material from the to-be-remembered material.

Adult↗
PubMed1986

Differential effects of posterior septal lesions on dispositional and representational memory.

A distinction between two classes of memory has been made in terms of the sensory availability of cues at the time of making discriminations which are influenced by past experience. Three tasks objectively defining this distinction were learned in a T-maze by three groups of rats: a delayed nonmatching-to-sample (DNMTS) which depends on representational memory; a simple sensory discrimination (SD) which depends on dispositional memory; and a more difficult discrimination, which also depends on dispositional memory, called the simultaneous conditional discrimination (SCD). The DNMTS and SD tasks were acquired quickly; the SCD task took many more trials. Posterior septal lesions impaired DNMTS performance but had no effect on retention of either the conditional discrimination (SCD) or the simple sensory discrimination (SD) tasks which depend on dispositional memory. The present study provides further evidence that dispositional and representational memory systems have at least partially distinct anatomical substrates in the brain and that it is the representational and not the conditional aspects of the DNMTS task that are impaired by the septal lesions.

Animals↗
PubMed2001

General transcription factors bind promoters repressed by Polycomb group proteins.

To maintain cell identity during development and differentiation, mechanisms of cellular memory have evolved that preserve transcription patterns in an epigenetic manner. The proteins of the Polycomb group (PcG) are part of such a mechanism, maintaining gene silencing. They act as repressive multiprotein complexes that may render target genes inaccessible to the transcriptional machinery, inhibit chromatin remodelling, influence chromosome domain topology and recruit histone deacetylases (HDACs). PcG proteins have also been found to bind to core promoter regions, but the mechanism by which they regulate transcription remains unknown. To address this, we used formaldehyde-crosslinked chromatin immunoprecipitation (X-ChIP) to map TATA-binding protein (TBP), transcription initiation factor IIB (TFIIB) and IIF (TFIIF), and dHDAC1 (RPD3) across several Drosophila promoter regions. Here we show that binding of PcG proteins to repressed promoters does not exclude general transcription factors (GTFs) and that depletion of PcG proteins by double-stranded RNA interference leads to de-repression of developmentally regulated genes. We further show that PcG proteins interact in vitro with GTFs. We suggest that PcG complexes maintain silencing by inhibiting GTF-mediated activation of transcription.

Amino Acid Sequence↗
PubMed2006

CD8+ recent thymic emigrants home to and efficiently repopulate the small intestine epithelium.

Prevailing knowledge dictates that naive alphabeta T cells require activation in lymphoid tissues before differentiating into effector or memory T cells capable of trafficking to nonlymphoid tissues. Here we demonstrate that CD8(+) recent thymic emigrants (RTEs) migrated directly into the small intestine. CCR9, CCL25 and alpha(4)beta(7) integrin were required for gut entry of CD8(+) RTEs. After T cell receptor stimulation, intestinal CD8(+) RTEs proliferated and acquired a surface phenotype resembling that of intraepithelial lymphocytes. CD8(+) RTEs efficiently populated the gut of lymphotoxin-alpha-deficient mice, which lack lymphoid organs. These studies challenge the present understanding of naive alphabeta T cell trafficking and suggest that RTEs may be involved in maintaining a diverse immune repertoire at mucosal surfaces.

Animals↗
PubMed2002

Molecular and flow cytometric characterization of the CD4 and CD8 T-cell repertoire in patients with myelodysplastic syndrome.

We studied 18 patients with myelodysplastic syndrome (MDS), measuring clonality and T-cell receptor Vbeta (TCRBV) expression of CD4 and CD8 T cells by polymerase chain reaction and by flow cytometric analysis of TCRBV families. The CD4 and CD8 T-cell repertoire in most MDS patients is characterized by an abnormal TCRBV-restricted expansion of T cells in CD4 and CD8 cells, and increased expression of the CD8 effector marker CD57 of multiple TCRBV in CD8 cells. Clonality analysis of CD4 and CD8 cells showed that seven of 10 patients analysed had a major clone in the CD8 cells but not in CD4 cells. Furthermore, in one patient we found that both the CD57- and CD57+ fraction contained the clone (which was absent from the TCRBV-negative fraction). These data suggest that, in MDS, multiple T-cell expansions can be found in both helper and cytotoxic T cells, and that, in the CD8 cells, T cells functionally differentiate in vivo from memory to effector T cells. Together, these data support the hypothesis of the involvement of T cells in the pathogenesis of MDS.

Adult↗
PubMed2001

A bridge between neuroscience and oncology: prostate cancer genesis. A 'negative' consequence of learning?

Prostate cancer has become the most commonly diagnosed cancer in men over recent years. The initiating mechanism for tumorigenesis within the prostate remains an unknown. The observation, that the cancer incidence in patients with chronic neurological disabilities is significantly lower than in the normal population lead to the hypothesis, that changed processing due to a barrage of aberrant sensory information within a healthy CNS can trigger events within the prostate cell, that cause malignant transformation. There is a broad overlap of cellular mechanism of gene expression, that lead to either long term potentiation, learning and memory storage or deregulated differentiation and malignant transformation.

Cell Transformation, Neoplastic↗
PubMed2002

Cost-effective recognition and diagnosis of dementia.

Alzheimer's disease (AD) has the potential to become the most overwhelming public health concern of this century due to increasing life expectancy and growth in the aging population. As a result, primary care physicians and neurologists will be seeing a greater number of elderly patients in their practice and will subsequently be expected to both identify and initiate treatment in those individuals who may display signs of dementia and related neurologic conditions. There is good evidence that AD is underrecognized or undercoded in primary care settings. Underrecognition is an important problem in this population because early treatment and counseling have been shown to provide benefits to both patients and caregivers. As their patient population ages, physicians need to learn to recognize the early symptoms of AD and make a diagnosis in order to provide cost-effective therapies.

Aged↗