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BACKGROUND: Type 1 diabetes (T1D) places an extraordinary burden on individuals and their families, as well as on the healthcare system. Despite recent advances in glucose sensors and insulin pump technology, only a minority of patients meet their glucose targets and face the risk of both acute and long-term complications, some of which are life-threatening. The JAK-STAT pathway is critical for the immune-mediated pancreatic beta cell destruction in T1D. Our pre-clinical data show that inhibitors of JAK1/JAK2 prevent diabetes and reverse newly diagnosed diabetes in the T1D non-obese diabetic mouse model. The goal of this study is to determine if the JAK1/JAK2 inhibitor baricitinib impairs type 1 diabetes autoimmunity and preserves beta cell function. METHODS: This will be as a multicentre, two-arm, double-blind, placebo-controlled randomized trial in individuals aged 10-30 years with recent-onset T1D. Eighty-three participants will be randomized in a 2:1 ratio within 100 days of diagnosis to receive either baricitinib 4mg/day or placebo for 48 weeks and then monitored for a further 48 weeks after stopping study drug. The primary outcome is the plasma C-peptide 2h area under the curve following ingestion of a mixed meal. Secondary outcomes include HbA1c, insulin dose, continuous glucose profile and adverse events. Mechanistic assessments will characterize general and diabetes-specific immune responses. DISCUSSION: This study will determine if baricitinib slows the progressive, immune-mediated loss of beta cell function that occurs after clinical presentation of T1D. Preservation of beta cell function would be expected to improve glucose control and prevent diabetes complications, and justify additional trials of baricitinib combined with other therapies and of its use in at-risk populations to prevent T1D. TRIAL REGISTRATION: ANZCTR ACTRN12620000239965 . Registered on 26 February 2020. CLINICALTRIALS: gov NCT04774224. Registered on 01 March 2021.
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Diabetes Mellitus Tipo 1 , Animales , Azetidinas , Péptido C , Ensayos Clínicos Fase II como Asunto , Diabetes Mellitus Tipo 1/diagnóstico , Diabetes Mellitus Tipo 1/tratamiento farmacológico , Método Doble Ciego , Glucosa/uso terapéutico , Humanos , Quinasas Janus/uso terapéutico , Ratones , Estudios Multicéntricos como Asunto , Purinas , Pirazoles , Ensayos Clínicos Controlados Aleatorios como Asunto , Factores de Transcripción STAT/uso terapéutico , Transducción de Señal , Sulfonamidas , Resultado del TratamientoRESUMEN
The soybean tubB1 gene is expressed primarily in the germinating seedling and is strongly down regulated in response to light in the upper hypocotyl. Previous studies demonstrate that the 1 kb 5'-flanking region of this gene is sufficient for its appropriate expression in etiolated seedlings. Transient expression studies demonstrated that the presence of the tubB1 3'-flanking sequence element decreased reporter gene expression as compared to the nopaline synthase (NOS) 3'-flanking sequence element. In this study we investigated the ability of the 3' flanking region to influence the expression of a beta-glucuronidase (GUS) reporter gene in transgenic tobacco and Arabidopsis. The presence of the tubB1 3'-flanking sequence element in chimera constructs reduced reporter gene expression specifically in the hypocotyl and petioles of light-grown, transgenic seedlings. Additionally, site-directed mutagenesis of the two TATA sequences in the 1 kb tubB1 5'-flanking sequence element (TATA box A in the -122 to -117 bp region and TATA box B in the -35 to -30 region) showed that both elements are functional and additive in controlling tubB1 gene expression in seedling tissues. While transcription from TATA box A was predominant regardless of lighting conditions, the relative usage of TATA box B increased in the dark. We conclude that both TATA box sequences are utilized to direct expression of the tubB1 gene to the cotyledons, hypocotyl and root tip of germinating seedlings that are regions of cell expansion and that the 3'-flanking sequence element down-regulates expression in the hypocotyl in response to light. Thus, it is plausible that the tubB1 protein may play an important role in cell expansion in seedling development requiring its regulated expression by light.
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Genes de Plantas , Glycine max/genética , TATA Box , Tubulina (Proteína)/genética , Arabidopsis/genética , Expresión Génica/efectos de la radiación , Genes Reporteros , Glucuronidasa/genética , Luz , Plantas/genética , Plantas/efectos de la radiación , Plantas Modificadas Genéticamente , Nicotiana/genéticaRESUMEN
Can auditory signals influence the processing of visual information? The present study examined the effects of simple auditory signals (clicks and noise bursts) whose onset was simultaneous with that of the visual target, but which provided no information about the target. It was found that such a signal enhances performance in the visual task: the accessory sound reduced response times for target identification with no cost to accuracy. The spatial location of the sound (whether central to the display or at the target location) did not modify this facilitation. Furthermore, the same pattern of facilitation was evident whether the observer fixated centrally or moved their eyes to the target. The results were not altered by changes in the contrast (and therefore visibility) of the visual stimulus or by the perceived utility of the spatial location of the sound. We speculate that the auditory signal may promote attentional 'disengagement' and that, as a result, observers are able to process the visual target sooner when sound accompanies the display relative to when visual information is presented alone.
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Percepción Auditiva/fisiología , Movimientos Oculares/fisiología , Percepción Visual/fisiología , Adolescente , Adulto , Análisis de Varianza , Atención/fisiología , Sensibilidad de Contraste/fisiología , Discriminación en Psicología/fisiología , Humanos , Iluminación , Tiempo de Reacción/fisiología , Localización de Sonidos/fisiologíaRESUMEN
OBJECTIVES: Significantly increased risk for developing cardiovascular disease in post-menopausal women is linked with the fall of oestrogen. Although supraphysiological levels of oestrogen may inhibit oxygen free radical mediated low-density lipoprotein (LDL) oxidation, the effect of physiological level of oestrogen on LDL oxidation is unknown. METHODS: The present study compared oxidizability of LDL in healthy pre- and post-menopausal women by using a commonly employed copper ion-dependent method. RESULTS: Pre-menopausal women (n=20, mean age 27) had significantly higher serum oestradiol level (576+/-109 pmol/l) in comparison to post-menopausal women (n=23, mean age 51, oestradiol 64+/-18 pmol/l, P<0.001). The oxidation of LDL in two groups was not different by measuring either the lag phase of conjugated dienes formation (54+/-12 vs. 55+/-14 min, P0.05) or the generation of thiobarbituric acid reactive substances over 4 h of oxidation. The major lipid soluble antioxidant in LDL, vitamin E (determined as alpha-tocopherol) is similar in two groups (2.34+/-0.48 vs. 2.40+/-0. 56 nmol/mg LDL, pre- and post-menopausal subjects, respectively, P0. 05). Linear regression analysis found a weak but significant correlation between LDL vitamin E level and oxidizability of LDL in both groups but did not show effect of serum oestradiol levels. CONCLUSION: The results suggest that physiological levels of oestrogen may not be able to affect in vitro LDL oxidation.
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Estradiol/sangre , Lipoproteínas LDL/sangre , Lipoproteínas LDL/metabolismo , Menopausia/metabolismo , Adulto , Antioxidantes/análisis , Enfermedades Cardiovasculares/prevención & control , Estudios de Casos y Controles , Femenino , Humanos , Modelos Lineales , Persona de Mediana Edad , Oxidación-Reducción , Vitamina E/análisis , Salud de la MujerRESUMEN
Maize (Zea mays L.) callus cultures cannot use mannose as a sole carbohydrate source, but can utilize fructose for that purpose. Phosphomannose isomerase (PMI) can convert mannose to fructose. Transgenic maize plants were obtained by selecting polyethylene glycol (PEG)-mediated transformed protoplasts on mannose (20 g/l) containing medium. Transgenic calluses and plants carrying the PMI structural gene, manA, were able to convert mannose to fructose. The PEG-mediated protoplast transformation frequency was 0.06%. Stable transformation was confirmed by PCR, PMI activity, germination tests, and by histochemical staining with 5-bromo-4-chloro-3-indolyl-ß-D-glucuronide (X-Gluc). Stable integration of the transgenes into the maize genome was demonstrated in T1 and T2 plants. Results indicate that the mannose selection system can be used for maize PEG-mediated protoplast transformation.
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AIMS: The use of oestrogen containing hormone replacement therapy (HRT) is related to a significantly reduced atherosclerotic cardiovascular risk in postmenopausal women. Oestrogen is thought to be antioxidant and may inhibit low-density lipoprotein (LDL) oxidation in vitro. We investigated the effect of combined oestrogen and progestogen HRT on LDL oxidation in postmenopausal women. METHODS: Eighteen healthy women were given oestrogen/progestogen, and the susceptibility of LDL to oxidation was measured as the level of autoantibody to oxidative modified LDL and the production of conjugated dienes during copper-dependent oxidation after 3 and 6 months HRT. The levels of vitamin E, the major antioxidant in LDL, were also measured. RESULTS: After HRT, the anti-oxidatively modified LDL antibody level remained unchanged [1.58+/-0.16, 0.10 (-0.10, 0.26), and 0.08 (-0.09, 0.19), mean+/-s.d. at baseline, and mean change with 95% confidence intervals for differences at 3 and 6 months, respectively, P>0.05] as did the production of conjugated dienes when determined as lag phase [51.2+/-7.5, -0.3 (-3.9, 3.3), and 1.5 (-3.4, 6.4) min, P>0.05]. The LDL vitamin E content, measured as alpha-tocopherol, was also not altered [2.34+/-0.54, -0.07 (-0.27, 0.13), and -0.07 (-0.33, 0.16) nmol mg(-1) LDL, P>0.05] by treatment. CONCLUSIONS: Combined oestrogen and progestogen therapy for 6 months in postmenopausal women does not protect LDL against oxidation.
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Terapia de Reemplazo de Estrógeno , Estrógenos/uso terapéutico , Lipoproteínas LDL/efectos de los fármacos , Posmenopausia/efectos de los fármacos , Progestinas/uso terapéutico , Colesterol/sangre , Quimioterapia Combinada , Estrógenos/administración & dosificación , Estrógenos/sangre , Femenino , Humanos , Lipoproteína(a)/sangre , Lipoproteína(a)/efectos de los fármacos , Lipoproteínas HDL/sangre , Lipoproteínas HDL/efectos de los fármacos , Lipoproteínas LDL/sangre , Lipoproteínas LDL/metabolismo , Persona de Mediana Edad , Oxidación-Reducción/efectos de los fármacos , Posmenopausia/sangre , Progestinas/administración & dosificación , Resultado del Tratamiento , Vitamina E/sangreRESUMEN
A divided visual field (DVF) procedure was used to investigate the scalp distribution of the event-related potential (ERP) repetition effect. ERPs were recorded from 27 scalp sites whilst subjects (n = 20) discriminated between words and non-words presented to either the left (LVF) or the right (RVF) visual field. A proportion of the words were repeated on the trial immediately following their first presentation. In two within-field repetition conditions the two encounters with a word occurred in the same visual field (LVF or RVF). In two across-field repetition conditions, the two encounters with a word occurred in different visual fields. For both words and non-words, task performance was better for RVF presentations than for LVF presentations. In each repetition condition there was a positive-going shift in the ERP elicited by repeated words compared to that elicited by words on their first presentation. This ERP repetition effect was equivalent in magnitude and lateralised to the right hemisphere to an equivalent degree in all four repetition conditions. It is suggested that the ERP effects largely reflect the processing of visual form thought to occur predominately in the right hemisphere.
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Dominancia Cerebral/fisiología , Electroencefalografía , Lectura , Conducta Verbal/fisiología , Campos Visuales/fisiología , Adolescente , Adulto , Mapeo Encefálico , Potenciales Evocados Visuales/fisiología , Femenino , Humanos , Masculino , Tiempo de Reacción/fisiología , Procesamiento de Señales Asistido por ComputadorRESUMEN
OBJECTIVES: Vitamin E (alpha-tocopherol) is the most important dietary antioxidant found in lipids and cell membranes and its intake is inversely related to the incidence of atherosclerotic cardiovascular disease. Oestrogen-containing oral contraceptives may decrease plasma vitamin E level in young women. We investigated if oestrogen-containing hormone replacement therapy (HRT) may have the same effect on vitamin E status in postmenopausal women METHODS: Eighteen healthy postmenopausal women took a combination of oestrogen/progestogen (Harmogen Provera) therapy and another ten acted as a control group. Blood samples were taken at baseline and repeated after 3 and 6 months in both groups. Vitamin E in plasma, red cells and isolated low-density lipoprotein (LDL) was measured as alpha-tocopherol by high-performance liquid chromatography. RESULTS: Vitamin E status showed no change in either group after 3 and 6 months in comparison to its baseline value. CONCLUSION: Combined oestrogen/progestogen HRT for 6 months in healthy postmenopausal women did not alter vitamin E. status in vivo.
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Terapia de Reemplazo de Estrógeno , Posmenopausia/sangre , Vitamina E/sangre , Antioxidantes/metabolismo , Arteriosclerosis/etiología , Membrana Celular/metabolismo , Cromatografía Líquida de Alta Presión , Anticonceptivos Orales/efectos adversos , Eritrocitos/metabolismo , Congéneres del Estradiol/uso terapéutico , Estrógenos Conjugados (USP)/uso terapéutico , Estrona/análogos & derivados , Estrona/uso terapéutico , Femenino , Estudios de Seguimiento , Humanos , Incidencia , Lípidos/sangre , Lipoproteínas LDL/sangre , Acetato de Medroxiprogesterona/uso terapéutico , Persona de Mediana Edad , Congéneres de la Progesterona/uso terapéuticoRESUMEN
Neural activity associated with overcoming retroactive interference in episodic memory was investigated with event-related brain potentials (ERPs). ERPs were recorded during a combined recognition/associative recall memory test in which subjects were required to identify previous studied words and recall their study associates. A retroactive interference condition (A-B, A-C, A-?) was compared with two control conditions A-B, C-D, A-? and A-B, A-B, A-?). No ERP effect specific to the interference condition was identified. ERPs to all three classes of old word differed however from those to new words. These differences involved two effects, one with a left parietal maximum that has been described before, and a left frontal effect of earlier onset which has not been reported previously. This latter effect may indicate a role for the left prefrontal cortex in associative retrieval.
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Potenciales Evocados/fisiología , Memoria/fisiología , Adulto , Electroencefalografía , Femenino , Humanos , Masculino , Corteza Prefrontal/fisiologíaRESUMEN
Event-related potentials (ERPs) were recorded from 13 scalp sites while subjects attempted to recall studied words using word-stems. If recall failed, stems were to be completed with the first suitable word to come to mind. To distinguish between correct completions accompanied and unaccompanied by explicit memory, subjects were required to make an overt recognition ("old/new") judgement for each completion. Semantically studied words were associated with higher levels of recall and recognition than were words subjected to non-semantic study. The sole ERP effect was a sustained positive shift in ERPs evoked by stems attracting correct completions that were correctly judged to be old. The shift was anteriorly distributed, and onset was around 300 ms post stimulus. It is interpreted as a reflection of processes either contributing to, or contingent upon, explicit memory retrieval.
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Potenciales Evocados/fisiología , Memoria/fisiología , Recuerdo Mental/fisiología , Adolescente , Adulto , Señales (Psicología) , Femenino , Humanos , Masculino , SemánticaRESUMEN
Event-related potentials (ERPs) were recorded from 13 scalp sites during the performance of an associative recall task. At study, subjects were presented with a series of word pairs and were required to incorporate the two members of each pair into a sentence. At test, the first members of each pair were presented intermixed with an equal number of unstudied items. Subjects were required to discriminate between new and studied (old) words and, for each word judged old, to attempt to recall the word with which it had been associated at study. Compared to the ERPs elicited by new words, the ERPs elicited by words correctly judged to be old and for which the associate was correctly recalled showed a sustained, positive-going shift (the "parietal old/new effect"). This effect was strongly lateralised to the left hemisphere and was maximal at temporo-parietal electrodes. The effect was absent in ERPs elicited by words that were correctly judged to be old, but for which the studied associate could not be recalled. The findings are taken as support for the idea that the parietal old/new effect reflects neural activity associated with the recollection of specific past episodes, and hence that the effect may index retrieval operations supported by the medial temporal lobe memory system.
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Potenciales Evocados/fisiología , Memoria/fisiología , Recuerdo Mental/fisiología , Vías Nerviosas/fisiología , Adulto , Femenino , Humanos , Masculino , Análisis y Desempeño de TareasRESUMEN
Three experiments investigated the electrophysiological consequences of repetition (e.g., scandal-scandal, buple-buple) and formal (e.g., scan-scandal, bup-buple) priming using words and nonwords. In each experiment, repetition and formal priming resulted in positive-going shifts in the event-related potential (ERP) that onset at approximately 200 ms poststimulus and were initially of similar magnitude. Subsequently, the repetition effect became larger than the formal priming effect. Although the word and nonword formal priming effects and the nonword repetition effects were greatest over midline and right hemisphere sites, the word repetition effects were greatest over the midline. It is suggested that the positive-going shift seen in the repetition and formal priming conditions was a modulation of the well-documented N400 component of the ERP. The topographic differences between the priming effects may have reflected differences in the nature of the representations to which cognitive operations are applied rather than differences in the nature of the operations themselves.
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Cognición/fisiología , Lenguaje , Adulto , Electroencefalografía , Electrofisiología , Potenciales Evocados/fisiología , Femenino , Humanos , MasculinoRESUMEN
In experiment 1, event-related potentials (ERPs) were recorded from 13 scalp sites while subjects viewed a series of line drawings of novel objects. Most of the drawings were of objects that were structurally possible, while the remainder were of structurally impossible objects; the task was to respond to each presentation of an impossible object. Approximately one third of the possible objects were repetitions of the immediately preceding drawing. Compared to the ERPs elicited by first presentations, the ERPs elicited by repetitions were more negative-going. This negative repetition effect comprised two temporally and topographically distinct components. In experiment 2, subjects monitored drawings of unstructured patterns, so as to detect occasional 'targets' containing a pair of parallel lines. Repetitions of 'non-target' patterns elicited ERPs which were largely indistinguishable from those elicited by first presentations. Thus, the negative repetition effects found in experiment 1 are not merely a consequence of repeating visual patterns in a demanding discrimination task. Possible reasons why novel objects should elicit ERP repetition effects opposite in polarity to those observed in tasks employing verbal or meaningful pictorial stimuli are discussed.
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Potenciales Evocados/fisiología , Percepción de Forma/fisiología , Análisis de Varianza , Femenino , Humanos , Masculino , Estimulación Luminosa , Análisis y Desempeño de Tareas , Factores de TiempoRESUMEN
In two recognition memory tests subjects made initial old/new judgements and subsequently judged whether 'old' words had been presented auditorily or visually at study. Test words were presented visually in Experiment 1 and auditorily in Experiment 2. ERPs evoked at test by words correctly judged 'old' were separated according to whether they were correctly or incorrectly assigned to their study modality. In both experiments, ERPs to correctly assigned words were more positive than those evoked by words correctly judged to be new. This ERP old/new effect was absent for words incorrectly assigned to study modality in Experiment 1, and was observed over a restricted latency range in Experiment 2. The findings are consistent with the hypothesis that the old/new effect is associated with recognition memory based on recollection of the study episode, rather than familiarity.
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Cognición/fisiología , Electroencefalografía , Potenciales Evocados Auditivos/fisiología , Potenciales Evocados Visuales/fisiología , Memoria/fisiología , Estimulación Acústica , Adolescente , Adulto , Toma de Decisiones , Electrooculografía , Femenino , Humanos , Masculino , Estimulación Luminosa , Desempeño Psicomotor/fisiología , Tiempo de Reacción/fisiologíaRESUMEN
A recognition memory test was conducted in which low and high frequency words were initially presented in one of two different study tasks. A word was defined as recollected if, at test, it was both confidently judged 'old', and confidently assigned to its correct study context. Low frequency words were more accurately recognised than high frequency items, and were also more likely to be assigned to their correct study context. The results are consistent with the view that low frequency words are better recognised because they are more likely to be recollected, rather than because they engender higher levels of relative familiarity. Event-related potentials (ERPs) evoked at test by correctly classified new words were contrasted with those evoked by old, recollected words. The ERPs to low frequency words exhibited large and reliable 'old/new' effects, in that from approx. 300 msec post-stimulus, waveforms were more positive-going for old than for new items. These effects were markedly smaller, and indeed non-significant, in the ERPs evoked by high frequency items. The results show that the interaction between word frequency and old/new differences in ERPs does not arise because of a confound between frequency and the probability of recollection. Together with other findings, they suggest that recollection is better conceived of as a graded, rather than as an all-or-none phenomenon.
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Cognición/fisiología , Electroencefalografía , Potenciales Evocados Auditivos/fisiología , Memoria/fisiología , Adulto , Electrooculografía , Femenino , Humanos , MasculinoRESUMEN
Abstract The effects on event-related potentials (ERPs) of within- and across-modality repetition of words and nonwords were investigated. In Experiment 1, subjects detected occasional animal names embedded in a series of words. AU items were equally likely to be presented auditorily or visually. Some words were repetitions, either within- or across-modality, of words presented six items previously. Visual-visual repetition evoked a sustained positive shift, which onset around 250 msec and comprised two topographically and temporally distinct components. Auditory-visual repetition modulated only the later of these two components. For auditory EMS, within- and across-modality repetition evoked effects with similar onset latencies. The within-modality effect was initially the larger, but only at posterior sites. In Experiment 2, critical items were auditory and visual nonwords, and target items were auditory words and visual pseudohomophones. Visual-visual nonword repetition effects onset around 450 msec, and demonstrated a more anterior scalp distribution than those evoked by auditory-visual repetition. Visual-auditory repetition evoked only a small, late-onsetting effect, whereas auditory-auditory repetition evoked an effect that, at parietal sites only, was almost equivalent to that from the analogous condition of Experiment 1. These findings indicate that, as indexed by ERF's, repetition effects both within- and across-modality are influenced by lexical status. Possible parallels with the effects of word and nonword repetition on behavioral variables are discussed.
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In four experiments, event-related brain potentials (ERPs) were evoked by visually presented word pairs in a task requiring responses to occasional target pairs. In Experiments 1 and 2, some pairs comprised items that had been presented previously. These repeated pairs consisted of words that had been paired together when first presented (same context condition) or words that had first been presented on consecutive trials (different context condition). ERP repetition effects were equivalent in the two conditions. In Experiment 3, same-context repeats were contrasted with a condition in which a repeated word was paired with a new word. Only the same-context pairs evoked a repetition effect. Experiment 4 showed that repetition effects to different- and same-context repeats remained equivalent when first presentations of the members of different-context pairs were separated by six intervening trials. We conclude that the ERP repetition effect shows little sensitivity to local context.
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Nivel de Alerta/fisiología , Atención/fisiología , Potenciales Evocados Visuales/fisiología , Recuerdo Mental/fisiología , Aprendizaje por Asociación de Pares/fisiología , Adulto , Mapeo Encefálico , Corteza Cerebral/fisiología , Femenino , Humanos , Masculino , Tiempo de Reacción/fisiología , SemánticaRESUMEN
Event-related potentials (ERPs) were recorded while subjects viewed visually presented words, some of which occurred twice. Each trial consisted of two colored letter strings, the requirement being to attend to and make a word/nonword discrimination for one of the strings. Attention was manipulated by color in Experiment 1, and color and a precue were used in Experiment 2. As in previous ERP studies of word repetition, a positive offset to repeated words developed when both first and second presentations were the focus of attention. In Experiment 2, ERPs showed evidence of positive-going repetition effects in all conditions in which at least one of the two presentations of the repeated word was attended. In the visual modality, the positive-going ERP repetition effect occurs only when at least one of the two presentations of a repeated item is the object of attention, which suggests that one or more of the processes reflected by the effect is capacity limited.
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Atención/fisiología , Electroencefalografía , Potenciales Evocados Visuales/fisiología , Reconocimiento Visual de Modelos/fisiología , Lectura , Adulto , Nivel de Alerta/fisiología , Corteza Cerebral/fisiología , Femenino , Humanos , Masculino , Psicofisiología , Tiempo de Reacción/fisiología , SemánticaRESUMEN
Event-related potentials (ERPs) were recorded in a three stimulus oddball task from 16 patients who had sustained a severe closed head injury at least 6 months before testing, and from 16 control subjects. The stimuli comprised a random sequence of frequent non-target tones (P = 0.70), rare target tones (P = 0.15), and rare novel sounds (P = 0.15). The task requirement was to respond promptly to each target tone. From a latency of 200 msec onwards, the ERPs evoked by frequent non-targets were substantially more negative-going in the head-injured than in the control group. When this difference in the ERPs to the frequent tones was taken into account, there was no evidence to suggest that either the latency or the amplitude of the target-evoked N2 and P3b components differed between the groups. The novel stimuli evoked a prominent P3a component. The amplitude and scalp distribution of this component differed little between the groups, but its peak latency was reliably longer in the head-injured subjects. The findings in respect of the N2 and P3b components suggest that impairments in early processing of task-relevant stimuli are not an invariant feature of closed head injury. The findings regarding P3a suggest that, in the majority of patients, head injury has only a limited effect on the neural systems underlying involuntary shifts of attention.
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Lesiones Encefálicas/fisiopatología , Potenciales Evocados Auditivos/fisiología , Estimulación Acústica , Adulto , Análisis de Varianza , Electroencefalografía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Psicometría , Tiempo de Reacción/fisiología , Análisis y Desempeño de TareasRESUMEN
ERPs were recorded during 5 blocks of a continuous recognition memory task. In each block words were shown twice, separated by an average of 6 intervening items, and the task was to respond discriminatively on the basis of whether each word was appearing in that block for the first (first presentations) or the second (second presentations) time. In blocks 2-5, half of the words had also been shown in the immediately preceding block, and half were new to the experiment. Subjects were slower and less accurate at identifying first presentations of words that had appeared in the preceding block, as compared to first presentations of entirely new words. In the latency ranges of the N400 and late positive components, ERPs to words that had previously been presented were more positive-going than were ERPs to new words. These 'across-block' ERP repetition effects were qualitatively very similar to, and additive with, those evoked by words repeated within a block. These findings suggest that the effects of word repetition on ERPs are not dependent on an invariant mapping between repetition and response and are not a consequence of facilitated decision/response processing for repeated items.