Drawing improves memory in patients with hippocampal damage.

The hippocampus plays a critical role in the formation of declarative memories, and hippocampal damage leads to significant impairments in new memory formation. Drawing can serve as a form of multi-modal encoding that improves declarative memory performance relative to other multimodal encoding strategies such as writing. We examined whether, and to what extent, patients with hippocampal damage could benefit from the mnemonic strategy of drawing. Three patients with focal hippocampal damage, and one patient with both hippocampal and cortical lesions, in addition to 22 age-, sex-, and education-matched controls, were shown a list of words one at a time during encoding and instructed to either draw a picture or repeatedly write each word for 40 s. Following a brief filled delay, free recall and recognition memory for words from both encoding trial types were assessed. Controls showed enhanced recall and recognition memory for words drawn versus those that were written, an effect that was even more pronounced in patients with focal hippocampal damage. By contrast, the patient with both hippocampal and cortical lesions showed no drawing-mediated boost in either recall or recognition memory. These findings demonstrate that drawing is an effective encoding strategy, likely accruing from the engagement of extra-hippocampal processes including the integration of cortical-based motor, visual, and semantic processing, enabling more elaborative encoding.

Accuracy of silicone impressions and stone models using two laboratory scanners: a 3D evaluation.

PURPOSE: To evaluate the in vitro accuracy of impressions obtained with two silicone and corresponding stone models using two laboratory scanners. MATERIAL AND METHODS: A master model with synthetic resin teeth with two single-unit crown preparations was created and scanned using a 12-MP scanner. Five conventional impressions of the physical model were prepared with different silicone impression systems (Zhermack and Coltene) using the double-mix technique and poured with gypsum. The impressions and stone models obtained were scanned by two extraoral scanning systems (Identica T500 Medit and S600 ARTI Zirkonzahn). All best-fit superimpositions of the teeth areas were conducted between the master model and the scans of the impressions and models obtained with the two scanners. A P < .05 significance level was considered. RESULTS: The Identica T500 Medit scanner showed an accuracy of 102.34 (89.67, 115.01) µm for Coltene silicone and 79.51 (67.82, 91.21) µm for Zhermack silicone, while the S600 ARTI Zirkonzhan scanner presented 110.79 (98.24, 123.33) µm and 91.91 (81.29, 102.54) µm, respectively, with significant differences between scanners for Zhermack silicone (P = .008) and for the corresponding stone models (P = .002). Zhermack silicone presented overall discrepancies lower than Coltene silicone, with statistically significant differences in both scanners analyzed (P < .001; P = .017). However, the discrepancies found were within clinically acceptable values. With the Zirkonzahn scanner, discrepancies found in the Zhermack impressions were lower than in the corresponding stone models (P < .001). CONCLUSION: The direct digitalization of silicone impressions by laboratory scanners presented comparable results to conventional techniques with stone models.

Implementation of immobilization accessories for positioning of small animals for radiation therapy / Implementação de acessórios de imobilização para o posicionamento de pequenos animais para a radioterapia

Radiation therapy is a modality that is presenting great advances in veterinary medicine worldwide. In Brazil, this therapeutic option is underachieved. The success of this method depends on several factors, including the use of appropriate accessories for protection and immobilization of patients. For the immobilization of small animals during treatment, in addition to sedation and anesthesia, immobilizing accessories, similar to those used in human radiotherapy, are used. This study aimed to present proposals for immobilizing accessories adapted to the positioning of small animals in order to be used in radiotherapy planning. In order to achieve results, accessories were made and tested in a living animal simulating a radiotherapy planning, which proved to be favorable to use in positioning small animals undergoing radiotherapy and for implementation processes.(AU)

A radioterapia é uma modalidade que tem apresentando grandes avanços dentro da medicina veterinária pelo mundo. No Brasil, essa opção terapêutica é pouco realizada. O sucesso dessa modalidade depende de vários fatores, entre eles, o uso de acessórios adequados para a proteção e imobilização dos pacientes. Para a imobilização dos pequenos animais durante o tratamento, além da sedação e da anestesia, são utilizados acessórios imobilizadores semelhantes aos usados na radioterapia humana. Devido a isso, este trabalho teve como objetivo de apresentar propostas de acessórios de imobilização adaptados ao posicionamento de pequenos animais para o uso nos planejamentos radioterápicos. Para a sua realização, foram confeccionados acessórios e testados em um animal vivo simulando um planejamento radioterápico, os quais mostraram ser favoráveis ao uso nos posicionamento de pequenos animais submetidos à radioterapia e para sua implementação.(AU)

A synthetic co-crystal prepared by cooperative single-crystal-to-single-crystal solid-state Diels-Alder reaction.

A single-crystal-to-single-crystal solid-state reaction involving the 2 : 1 charge-transfer complex of 9-bromoanthracene and bis(N-cyclobutylimino)-1,4-dithiin leads to a synthetic co-crystal composed of the Diels-Alder cycloadduct and unreacted 9-bromoanthracene molecules. Analysis of close contacts in the product crystal and DFT energy calculations indicate an ordered arrangement of product and unreacted molecules due to cooperative effects during the reaction.

Duddingtonia flagrans no controle de nematoides gastrintestinais de equinos em fases de vida livre / Control of free living gastrointestinal nematodes of horses using Duddingtonia flagrans

O objetivo deste estudo foi avaliar a atividade predatória do fungo Duddingtonia flagrans contra larvas infectantes (L3) de nematoides gastrintestinais na pastagem e no bolo fecal de equinos, em um período de 21 dias. O delineamento experimental foi inteiramente ao acaso, com três grupos tratados (G1, G2 e G3) e um controle (C), com oito animais/grupo. Os tratados receberam 1,5x105; 3x105 e 6x105 clamidósporos de D. flagrans/kg-1peso vivo animal, G1, G2 e G3, respectivamente, durante 21 dias, com administração a cada três dias. Foram delimitadas 36 áreas de 1m2 cada, equivalendo a repetições em triplicata para cada grupo. As fezes foram coletadas dos animais nos dias 0 (D0), 15 (D15) e 30 (D30 = sete dias após a última administração dos tratamentos) e depositadas nessas áreas de pastagem. O número de larvas presentes nos bolos fecais e na pastagem foi avaliado após 14 e 21 dias de cada etapa de deposição. A avaliação da atividade predatória de D. flagrans na pastagem e nos bolos fecais demonstrou que a redução do número de L3 nos bolos fecais foi acompanhada pelo aumento da variável na pastagem. Não se constatou diferença significativa entre os grupos avaliados em decorrência da temperatura média registrada durante o período. As avaliações realizadas em um curto período podem ser insuficientes para a avaliação do efeito do fungo.(AU)

The aim of this study was to evaluate the predatory activity of the fungus Duddingtonia flagrans against infective larvae (L3 ) of gastrointestinal nematodes of horses in the pasture and dung patch during a period of 21 days. The experimental design was completely randomized, with three groups treated (G1, G2 and G3) and a control (C), with eight animals/group. The treated animals received G1: 1.5x105; G2: 3x105 and G3: 6x105 chlamydospores of D. flagrans/kg body weight during 21 days. The experiment ran in the environment using 36 areas of 1 m2 delimited on pasture, where stool samples were distributed for each group, in triplicates. Feces were collected from the animals at days 0 (D0), 15 (D15) and 30 (D30) and deposited on the pasture areas. After 14 and 21 days of each deposition step , the number of L 3 present in dung and pasture was evaluated. The number of L3 in the dung was accompanied by increase of the same variable in the pasture. The evaluation recorded in a short period may be insufficient to evaluate fungus development.(AU)

Middle-Aged Diabetic Females and Males Present Distinct Susceptibility to Alzheimer Disease-like Pathology.

Type 2 diabetes (T2D) is a highly concerning public health problem of the twenty-first century. Currently, it is estimated that T2D affects 422 million people worldwide with a rapidly increasing prevalence. During the past two decades, T2D has been widely shown to have a major impact in the brain. This, together with the cognitive decline and increased risk for dementia upon T2D, may arise from the complex interaction between normal brain aging and central insulin signaling dysfunction. Among the several features shared between T2D and some neurodegenerative disorders (e.g., Alzheimer disease (AD)), the impairment of insulin signaling may be a key link. However, these may also involve changes in sex hormones' function and metabolism, ultimately contributing to the different susceptibilities between females and males to some pathologies. For example, female sex has been pointed as a risk factor for AD, particularly after menopause. However, less is known on the underlying molecular mechanisms or even if these changes start during middle-age (perimenopause). From the above, we hypothesized that sex differentially affects hormone-mediated intracellular signaling pathways in T2D brain, ultimately modulating the risk for neurodegenerative conditions. We aimed to evaluate sex-associated alterations in estrogen/insulin-like growth factor-1 (IGF-1)/insulin-related signaling, oxidative stress markers, and AD-like hallmarks in middle-aged control and T2D rat brain cortices. We used brain cortices homogenates obtained from middle-aged (8-month-old) control Wistar and non-obese, spontaneously T2D Goto-Kakizaki (GK) male and female rats. Peripheral characterization of the animal models was done by standard biochemical analyses of blood, plasma, or serum. Steroid sex hormones, oxidative stress markers, and AD-like hallmarks were given by specific ELISA kits and colorimetric techniques, whereas the levels of intracellular signaling proteins were determined by Western blotting. Albeit the high levels of plasma estradiol and progesterone observed in middle-aged control females suggested that they were still under their reproductive phase, some gonadal dysfunction might be already occurring in T2D ones, hence, anticipating their menopause. Moreover, the higher blood and lower brain cholesterol levels in female rats suggested that its dysfunctional uptake into the brain cortex may also hamper peripheral estrogen uptake and/or its local brain steroidogenic metabolism. Despite the massive drop in IGF-1 levels in females' brains, particularly upon T2D, they might have developed some compensatory mechanisms towards the maintenance of estrogen, IGF-1, and insulin receptors function and of the subsequent Akt- and ERK1/2-mediated signaling. These may ultimately delay the deleterious AD-like brain changes (including oxidative damage to lipids and DNA, amyloidogenic processing of amyloid precursor protein and increased tau protein phosphorylation) associated with T2D and/or age (reproductive senescence) in female rats. By demonstrating that differential sex steroid hormone profiles/action may play a pivotal role in brain over T2D progression, the present study reinforces the need to establish sex-specific preventive and/or therapeutic approaches and an appropriate time window for the efficient treatment against T2D and AD.

The functions of TRPA1 and TRPV1: moving away from sensory nerves.

The transient receptor potential vanilloid 1 and ankyrin 1 (TRPV1 and TRPA1, respectively) channels are members of the TRP superfamily of structurally related, non-selective cation channels. It is rapidly becoming clear that the functions of TRPV1 and TRPA1 interlink with each other to a considerable extent. This is especially clear in relation to pain and neurogenic inflammation where TRPV1 is coexpressed on the vast majority of TRPA1-expressing sensory nerves and both integrate a variety of noxious stimuli. The more recent discovery that both TRPV1 and TRPA1 are expressed on a multitude of non-neuronal sites has led to a plethora of research into possible functions of these receptors. Non-neuronal cells on which TRPV1 and TRPA1 are expressed vary from vascular smooth muscle to keratinocytes and endothelium. This review will discuss the expression, functionality and roles of these non-neuronal TRP channels away from sensory nerves to demonstrate the diverse nature of TRPV1 and TRPA1 in addition to a direct role in pain and neurogenic inflammation.

SPECT/CT lymphoscintigraphy of heterotopic cardiac grafts reveals novel sites of lymphatic drainage and T cell priming.

The normal function of lymphatic vessels is to facilitate the trafficking of antigen presenting cells to draining lymph nodes where they evoke an immune response. Donor lymphatic vessels are not connected to that of recipients' during organ transplantation. The pathophysiology of this disruption has received little attention. Murine heterotopic cardiac transplantation has been used extensively in transplantation research. Following vascularized organ transplantation, the main site of allosensitization is thought to be in the spleen of the recipient as a result of migration of donor passenger leukocytes via blood. Here, using Single Photon Emission Computed Tomography/Computerized Tomography (SPECT/CT) lymphoscintigraphy, we studied the pattern of lymphatic flow from mouse heterotopic abdominal cardiac grafts and identified mediastinal lymph nodes as the draining nodes for the donor graft. Staining with HY tetramer after transplantation of HY mismatched heart grafts and ELISPOT following allogeneic grafts to detect donor specific T cells revealed them as important sites for allosensitization. Our data indicates that mediastinal lymph nodes play a crucial role in the alloimmune response in this model, and should be used for ex vivo and adoptive transfer studies after transplantation in addition to the spleen.

Potency ranking of valproic acid analogues as to inhibition of cardiac differentiation of embryonic stem cells in comparison to their in vivo embryotoxicity.

The embryonic stem cell test (EST) is one of the more promising and extensively studied tests in the field of developmental toxicology. We evaluated the effect of a series of structurally related valproic acid analogues on cardiomyocyte differentiation in the EST. The goal of the present study was to determine the applicability of the EST by potency ranking within this chemical class. Cardiomyocyte differentiation was evaluated by morphological scoring as well as by gene expression analysis of cardiac markers using RT-PCR. All VPA analogues tested inhibited cardiomyocyte differentiation, with the exception of (±)-2-ethyl-4-methyl pentanoic acid, which correlates to their known in vivo developmental toxicity. Effects were also evident on gene expression of cardiomyocyte differentiation-regulated genes, such as MHC and Nkx2.5. Overall, the present results indicate that the assay can be a valuable screening tool in potency ranking of structurally related compounds.

2-{[(4-Methylphenyl)sulfonyl]amino}phenyl 4-methylbenzenesulfonate.

The title compound, C(20)H(19)NO(5)S(2), crystallizes as an almost 2:1 mixture of two molecular orientations (described as Orient-A and Orient-B). The consequences of these two orientations is the formation of three types of N-H...O hydrogen-bonded dimers in which the (Orient-A + Orient-A) dimers are likely to be the most stable, while the mixed (Orient-A + Orient-B) dimers are more frequent. Extra interactions in the form of C-H...O and C-H...pi interactions act to further stabilize these dimers and probably allow the less energetically favourable (Orient-A + Orient-B) and (Orient-B + Orient-B) hydrogen-bonded dimers to exist by preventing their conversion to (Orient-A + Orient-A)-only hydrogen-bonded dimers during the crystal-growth process.

1-Benzyl-3,3-dichloro-1H-indol-2(3H)-one.

The title compound, C(15)H(11)Cl(2)NO, was synthesized from N-benzyl isatin. The compound crystallizes as stacks of molecules running down the c axis. Molecules within each of these stacks interact with each other through pi-pi and C-H...pi interactions, and interact with neighbouring stacks through C-H...O interactions.

Cutaneous T-cell lymphoma with HTLV-I infection: clinical overlap with adult T-cell leukemia/lymphoma.

Adult T-cell leukemia/lymphoma (ATLL) is a malignant proliferation of mature helper T lymphocytes,(1) and is caused by human T-lymphotropic virus type I (HTLV-I);(2) an HTLV-I infection endemic in the Caribbean, south-western Japan, South America and Africa.(3,4) Seroepidemiological studies suggest that it is also endemic in Brazil.(5) Although carriers of HTLV-I show polyclonal integration of virus in T lymphocytes, only patients with ATLL of various subtypes show monoclonal integration of HTLV-I in tumor cells.(6,7) Cutaneous T-cell lymphomas (CTCL) are a group of primary cutaneous lymphoproliferative diseases(8) with unknown etiology.(9) The two most common presentations of CTCL are mycosis fungoides (MF) and Sézary syndrome (SS).(10-13) However, both CTCL categories can easily resemble ATLL. Therefore, in HTLV-I endemic areas, differentiation between ATLL and CTCL must be performed, as they have different prognoses and treatment approaches.(14).

Comparing language lateralization determined by dichotic listening and fMRI activation in frontal and temporal lobes in children with epilepsy.

We investigated the relationship between ear advantage scores on the Fused Dichotic Words Test (FDWT), and laterality of activation in fMRI using a verb generation paradigm in fourteen children with epilepsy. The magnitude of the laterality index (LI), based on spatial extent and magnitude of activation in classical language areas (BA 44/45, 21/22, 39) differed significantly for patients classified with unilateral left, compared to bilateral, language representation based on FDWT scores. Concordance with fMRI was higher for those classified with unilateral left, than bilateral language representation on the FDWT. Of note, asymmetry in temporal lobe, rather than frontal lobe, activation was more strongly related to the LI from the dichotic listening test. This study shows that the FDWT can provide a quick and valid estimate of lateralization in pre-surgical candidates, which can be readily adopted for other clinical or research purposes when an estimate of language dominance is desired.

Photodimerization of the alpha'-polymorph of ortho-ethoxy-trans-cinnamic acid in the solid state. I. Monitoring the reaction at 293 K.

Structural changes that occur during the [2 + 2] photodimerization of the metastable alpha'-polymorph of ortho-ethoxy-trans-cinnamic acid at 293 K are presented here. Crystals of the alpha'-polymorph were first stabilized by exposing the alpha-polymorph to UV light for a short period of time at 343 K. The photodimerization reaction was then carried out at 293 K and observed in situ by single-crystal X-ray diffraction. The alpha'-polymorph contains three molecules in the asymmetric unit, labelled A, B and C, which are arranged to form two potential reaction sites. The intermolecular distance between the C=C bonds of molecules A and B (making up the AB site) is 3.6 A, and these were observed to undergo photodimerization at 293 K. The corresponding distance between centrosymmetrically related C=C bonds in the CC site (made up of C molecules) is 4.6 A, and these remain unreacted even after 60 h irradiation at 293 K. The crystal of the final product, which corresponds to a 66.7% conversion (only two out of three molecules in the asymmetric unit take part in the photodimerization reaction at 293 K), contains an ordered arrangement of the photodimer and unreacted monomer. The crystal retains many structural features of the original monomer crystal, including carboxylic acid hydrogen bonds and C-H.O interactions. Single-crystal X-ray diffraction was used to monitor changes in the unit-cell parameters, reacting molecules and molecular conformations as the reaction progressed. The conformation of the photodimer obtained from the solid-state reaction differs from that of the photodimer obtained by recrystallization from solution.

Efeito do ultra-som terapêutico em tendinite experimental de eqüinos: estudo clínico, ultra-sonográfico e histopatológico de dois protocolos / Clinic, ultrasonographic and histopatological studies of two protocols of ultrasonic therapy on experimental tendonitis in horses

Avaliaram-se dois protocolos de ultra-som no tratamento de lesöes do tendäo flexor digital superficial (TFDS). Foram estudados 18 eqüinos, nos quais foi injetada uma soluçäo de colagenase a 0,25 por cento no TFDS esquerdo, à altura do terço médio da regiäo metacarpiana. Os eqüinos foram divididos em: grupo A - tratado por ultra-som (UST) na freqüência de 3 MHz e intensidade de 1W/cm², no modo contínuo, por seis minutos; grupo B - tratado na mesma freqüência, intensidade e tempo, no modo pulsado; e grupo C - controle. Os tratamentos foram iniciados 48h após a induçäo da lesäo, totalizando oito sessöes. Os eqüinos foram estudados por 40 dias, avaliando-se o quadro clínico e a regressäo dos sintomas. Por meio de exames ultra-sonográficos semanais avaliaram-se a área transversal e a ecogenicidade da lesäo para estabelecimento do índice de severidade (IS). A lesäo resultou em aumento médio de 1,5cm na circunferência da regiäo metacarpiana, resposta à pressäo digital de leve a moderada e grau de claudicaçäo de 1 a 3. A regressäo dos sintomas ocorreu, em média, nove dias no grupo A, 12 dias no grupo B e 21 dias no grupo C. O percentual de regressäo no IS aos 40 dias foi de 42,5, 57,7 e 34,1, respectivamente. A avaliaçäo histológica mostrou neovascularizaçäo pronunciada e maior atividade fibroblástica nos grupos tratados (A e B) comparados ao grupo-controle. Estes resultados sugerem que o UST é efetivo na reduçäo dos sintomas clínicos da tendinite

Chromium(VI) interaction with plant and animal mitochondrial bioenergetics: a comparative study.

The mechanism of Cr(VI)-induced toxicity in plants and animals has been assessed for mitochondrial bioenergetics and membrane damage in turnip root and rat liver mitochondria. By using succinate as the respiratory substrate, ADP/O and respiratory control ratio (RCR) were depressed as a function of Cr(VI) concentration. State 3 and uncoupled respiration were also depressed by Cr(VI). Rat mitochondria revealed a higher sensitivity to Cr(VI), as compared to turnip mitochondria. Rat mitochondrial state 4 respiration rate triplicated in contrast to negligible stimulation of turnip state 4 respiration. Chromium(VI) inhibited the activity of the NADH-ubiquinone oxidoreductase (complex I) from rat liver mitochondria and succinate-dehydrogenases (complex II) from plant and animal mitochondria. In rat liver mitochondria, complex I was more sensitive to Cr(VI) than complex II. The activity of cytochrome c oxidase (complex IV) was not sensitive to Cr(VI). Unique for plant mitochondria, exogenous NADH uncoupled respiration was unaffected by Cr(VI), indicating that the NADH dehydrogenase of the outer leaflet of the plant inner membrane, in addition to complexes III and IV, were insensitive to Cr(VI). The ATPase activity (complex V) was stimulated in rat liver mitochondria, but inhibited in turnip root mitochondria. In both, turnip and rat mitochondria, Cr(VI) depressed mitochondrial succinate-dependent transmembrane potential (Deltapsi) and phosphorylation efficiency, but it neither affected mitochondrial membrane permeabilization to protons (H+) nor induced membrane lipid peroxidation. However, Cr(VI) induced mitochondrial membrane permeabilization to K+, an effect that was more pronounced in turnip root than in rat liver mitochondria. In conclusion, Cr(VI)-induced perturbations of mitochondrial bioenergetics compromises energy-dependent biochemical processes and, therefore, may contribute to the basal mechanism underlying its toxic effects in plant and animal cells.

Effects of NADH and H(2)O(2) on chromate-induced human erythrocytes hemoglobin oxidation and peroxidation.

The effects of NADH and H(2)O(2) on chromate-induced human erythrocyte hemoglobin oxidation and peroxidation were studied. It was observed that NADH decreases the levels of chromate-induced human erythrocyte hemoglobin oxidation and peroxidation. H(2)O(2) decreases the levels of chromate-induced hemoglobin oxidation, but increases the levels of chromate-induced peroxidation. The ability of H(2)O(2) to decrease the levels of chromate-induced hemoglobin oxidation is higher than that observed for NADH. Furthermore, H(2)O(2) increases the inhibitory effect of NADH on chromate-induced hemoglobin oxidation, but decreases the NADH effect on chromate-induced peroxidation. The meaning of these results is discussed in terms of involvement of reactive chromium(V) species and reactive oxygen species in the mechanism by which chromate induces its effects in human erythrocytes.

Post-transplant lymphoproliferative disorders (PTLD) after renal transplantation: management and evolution of seven cases among 1002 renal transplants in São Paulo, Brazil.

We reported seven cases (0.7%) of PTLD among 1002 renal transplants performed at Renal Transplant Service from Hospital São Paulo-Universidade Federal de São Paulo/Escola Paulista de Medicina, São Paulo, Brazil, between 1976 and 1997. There were three male and four female patients with median age of 37 year-old. According to Ann Arbor staging system there were four localized extra-nodal intermediate-grade NHL, one disseminated low-grade NHL and two polyclonal lymphoid hyperplasia. Four patients received cadaveric, two received related and one received unrelated renal transplant. PTLD occurred after a median latency period of 36 months (ranging from 5 to 84 months). In situ hybridization for EBER1 was performed in five patients and molecular evidence of EBV was found in 3 cases (two DLCL and one lymphoplasmocytoid lymphoma). All patients were treated with immunosuppression withdrawal, four patients received anthracyclin-based chemotherapy for control of localized or systemic clonal disease and three were treated with resection of primary PTLD. Four of seven patients (57%) are in complete remission 11, 20, 25 and 79 months after PTLD onset. One patient lost follow-up and two patients died due to lymphoma relapse, respectively 4 and 10 months after completion of treatment. In conclusion, our experience with this small group of patients showed that: 1) immunosuppression withdrawal is not necessarily associated with loss of renal transplant and can be used as the only treatment for polyclonal PTLD; 2) chemotherapy can simultaneously lead to clonal PTLD remission and periodic immunosuppression, avoiding graft rejection after immunosuppression withdrawal.

Divided attention and memory: evidence of substantial interference effects at retrieval and encoding.

In 5 divided attention (DA) experiments, students (24 in each experiment) performed visual distracting tasks (e.g., recognition of words, word and digit monitoring) while either simultaneously encoding an auditory word list or engaging in oral free recall of the target word list. DA during retrieval, using either of the word-based distracting tasks, produced relatively larger interference effects than the digit-monitoring task. DA during encoding produced uniformly large interference effects, regardless of the type of distracting task. Results suggest that when attention is divided at retrieval, interference is created only when the memory and concurrent task compete for access to word-specific representational systems; no such specificity is necessary to create interference at encoding. During encoding, memory and concurrent tasks compete primarily for general resources, whereas during retrieval, they compete primarily for representational systems.