Repeating with the right hemisphere: reduced interactions between phonological and lexical-semantic systems in crossed aphasia?

Knowledge on the patterns of repetition amongst individuals who develop language deficits in association with right hemisphere lesions (crossed aphasia) is very limited. Available data indicate that repetition in some crossed aphasics experiencing phonological processing deficits is not heavily influenced by lexical-semantic variables (lexicality, imageability, and frequency) as is regularly reported in phonologically-impaired cases with left hemisphere damage. Moreover, in view of the fact that crossed aphasia is rare, information on the role of right cortical areas and white matter tracts underpinning language repetition deficits is scarce. In this study, repetition performance was assessed in two patients with crossed conduction aphasia and striatal/capsular vascular lesions encompassing the right arcuate fasciculus (AF) and inferior frontal-occipital fasciculus (IFOF), the temporal stem and the white matter underneath the supramarginal gyrus. Both patients showed lexicality effects repeating better words than non-words, but manipulation of other lexical-semantic variables exerted less influence on repetition performance. Imageability and frequency effects, production of meaning-based paraphrases during sentence repetition, or better performance on repeating novel sentences than overlearned clichés were hardly ever observed in these two patients. In one patient, diffusion tensor imaging disclosed damage to the right long direct segment of the AF and IFOF with relative sparing of the anterior indirect and posterior segments of the AF, together with fully developed left perisylvian white matter pathways. These findings suggest that striatal/capsular lesions extending into the right AF and IFOF in some individuals with right hemisphere language dominance are associated with atypical repetition patterns which might reflect reduced interactions between phonological and lexical-semantic processes.

Dynamic changes in brain functional connectivity during concurrent dual-task performance.

This study investigated the spatial, spectral, temporal and functional proprieties of functional brain connections involved in the concurrent execution of unrelated visual perception and working memory tasks. Electroencephalography data was analysed using a novel data-driven approach assessing source coherence at the whole-brain level. Three connections in the beta-band (18-24 Hz) and one in the gamma-band (30-40 Hz) were modulated by dual-task performance. Beta-coherence increased within two dorsofrontal-occipital connections in dual-task conditions compared to the single-task condition, with the highest coherence seen during low working memory load trials. In contrast, beta-coherence in a prefrontal-occipital functional connection and gamma-coherence in an inferior frontal-occipitoparietal connection was not affected by the addition of the second task and only showed elevated coherence under high working memory load. Analysis of coherence as a function of time suggested that the dorsofrontal-occipital beta-connections were relevant to working memory maintenance, while the prefrontal-occipital beta-connection and the inferior frontal-occipitoparietal gamma-connection were involved in top-down control of concurrent visual processing. The fact that increased coherence in the gamma-connection, from low to high working memory load, was negatively correlated with faster reaction time on the perception task supports this interpretation. Together, these results demonstrate that dual-task demands trigger non-linear changes in functional interactions between frontal-executive and occipitoparietal-perceptual cortices.

Performance in a complex task and breathing under odor exposure.

We investigated the influences of odor exposure on performance and on breathing measures. The task was composed of tracking, short-term memory, and peripheral reaction parts. During rest or while performing the task, 12 participants were exposed to 4 different odors in 2 intensities. The higher intensity of the malodors induced a short-term decrement in mean inspiration flow (Vi/Ti) after stimulus onset and impaired performance in the short-term memory task, as compared with control trials; no effect was found for the positively judged odors. The study suggests that a distractor as simple as a bad smell may pull a person off task, however briefly, and may result in a detriment to performance. Actual or potential applications of this research involve designing or securing tasks in such a way that a brief withdrawal of attention does not have fatal consequences.

Lien entre l'activité pariéto-occipitale enregistrée pendant une tâche de mémoire à court terme visuelle et les habiletés mathématiques : une étude en magnétoencéphalographie

La mémoire à court terme visuelle (MCTv) est un système qui permet le maintien temporaire de l’information visuelle en mémoire. La capacité en mémoire à court terme se définit par le nombre d’items qu’un individu peut maintenir en mémoire sur une courte période de temps et est limitée à environ quatre items. Il a été démontré que la capacité en MCTv et les habiletés mathématiques sont étroitement liées. La MCTv est utile dans beaucoup de composantes liées aux mathématiques, comme la résolution de problèmes, la visualisation mentale et l’arithmétique. En outre, la MCTv et le raisonnement mathématique font appel à des régions similaires du cerveau, notamment dans le cortex pariétal. Le sillon intrapariétal (SIP) semble être particulièrement important, autant dans la réalisation de tâches liées à la MCTv qu’aux habiletés mathématiques. Nous avons créé une tâche de MCTv que 15 participants adultes en santé ont réalisée pendant que nous enregistrions leur activité cérébrale à l’aide de la magnétoencéphalographie (MEG). Nous nous sommes intéressés principalement à la composante SPCM. Une évaluation neuropsychologique a également été administrée aux participants. Nous souhaitions tester l’hypothèse selon laquelle l’activité cérébrale aux capteurs pariéto-occipitaux pendant la tâche de MCTv en MEG sera liée à la performance en mathématiques. Les résultats indiquent que l’amplitude de l’activité pariéto-occipitale pendant la tâche de MCTv permet de prédire les habiletés mathématiques ainsi que la performance dans une tâche de raisonnement perceptif. Ces résultats permettent de confirmer le lien existant entre les habiletés mathématiques et le fonctionnement sous-jacent à la MCTv.

Desempenho em consciência fonológica, memória operacional, leitura e escrita na dislexia familial

Background: familial dyslexia. Aim: to characterize and compare the phonological awareness, working memory, reading and writing abilities of individuals whose family members are also affected. Method: in this study 10 familial nuclei of natural family relationship of individuals with dyslexia were analyzed. Families of natural individuals living in the west region of the state of São Paulo were selected. Inclusion criteria were: to be a native speaker of the Brazilian Portuguese language, to have 8 years of age or more, to present positive familial history for learning disabilities, That is, to present at least one relative with difficulties in learning. Exclusion criteria were: to present any neurological disorder genetically caused or not, in any of the family members, such as dystonia, extra pyramidal diseases, mental disorder, epilepsy, attention deficit and hyperactivity disorder (ADHA); psychiatric symptoms or conditions; or any other pertinent conditions that could cause errors in the diagnosis. As for the diagnosis of developmental dyslexia, information about the familial history of the adolescents and children was gathered with the parents, so that a detailed pedigree could be delineated. Neurological, psychological, speech-language, and school performance evaluations were made with the individuals and their families. Results: the results of this study suggest that the dyslexic individuals and their respective relatives, also with dyslexia, presented lower performances than the control group in terms of rapid automatic naming, reading, writing and phonological awareness. Conclusion: deficits in phonological awareness, working memory, reading and writing seem to have genetic susceptibility that possibly determine, when in interaction with the environment, the manifestation of dyslexia.

Avaliação da memória operacional fonológica e impulsividade de usuários de drogas atendidos em um Centro de Atenção Integrada à Saúde Mental

OBJETIVO: avaliar a memória operacional fonológica e relacionar com a impulsividade de pacientes em tratamento no Centro de Atenção Integrada à Saúde Mental. MÉTODO: 29 usuários: 21 do gênero masculino e 8 do feminino, usuários de substâncias psicoativas, com 37,9±10,5 anos de idade e 10,59±3,53 anos de escolaridade; e 30 voluntários: 19 do gênero masculino e 11 do feminino, com 32,4±11,9 anos de idade e 11,07±3,29 anos de escolaridade, sem histórico psiquiátrico ou de dependência química foram convocados à avaliação de: 1) memória operacional para palavras e pseudo-palavras; 2) impulsividade em seus fatores de segunda ordem (impulsividade atencional, motora e de não planejamento). RESULTADOS: o desempenho dos usuários de substâncias psicoativas na avaliação da memória em comparação ao grupo controle foi pior tanto no span auditivo de palavras e pseudo-palavras como também no número total de recordação de palavras e pseudo-palavras. Na avaliação da impulsividade, os usuários apresentaram escores elevados em contraposição aos sujeitos controle em todos os subtipos de impulsividade, inclusive no total. Na análise de correlação dos dados não foram encontradas relações entre os escores de impulsividade e memória. CONCLUSÃO: : este padrão de respostas indica comprometimento da memória operacional fonológica provavelmente independente do alto nível de impulsividade apresentado pelos usuários de drogas. Estas análises contribuem para propor estratégias de tratamento direcionadas às alterações detectadas.

Relação entre a porcentagem de consoantes corretas e a memória operacional fonológica na alteração específica de linguagem

OBJETIVO: Verificar se há influência da idade no desempenho fonológico e na memória operacional e se há correlação entre o desempenho em prova de memória operacional fonológica e o índice de gravidade da alteração fonológica em crianças com alteração específica de linguagem. MÉTODOS: Participaram deste estudo 30 sujeitos com diagnóstico de alteração específica de linguagem, com idades entre 4 e 6 anos. Foram coletados dos prontuários dados referentes ao desempenho nas provas de memória operacional fonológica e fonologia (utilizando o índice de Porcentagem de Consoantes Corretas - Revisado). Análises estatísticas pertinentes foram realizadas. RESULTADOS: Não houve influência da idade para a fonologia e para a memória operacional, mas houve correlação positiva na comparação do desempenho na prova de memória operacional fonológica com ambas as tarefas da prova de fonologia. CONCLUSÃO: A idade não favorece o aprimoramento das habilidades fonológicas e de memória operacional fonológica. Porém, há correlação positiva entre a memória operacional fonológica e o índice de gravidade da alteração fonológica, o que significa que quanto melhor a produção de fala, melhor o desempenho da memória operacional fonológica.

Habilidades de processamento fonológico e de escrita em crianças com distúrbio específico de linguagem: um estudo comparativo com a normalidade

Introdução: Crianças com distúrbio específico de linguagem (DEL) são propensas a apresentar dificuldade no processo de alfabetização devido às múltiplas alterações de linguagem que possuem. Este estudo comparou e caracterizou o desempenho de crianças com DEL e em desenvolvimento típico de linguagem em atividades de aliteração, rima, memória de curto prazo fonológica, ditado de palavras e de pseudopalavras. A principal hipótese do estudo era de que o grupo DEL apresentaria desempenho inferior do que o grupo em desenvolvimento típico em todas as habilidades estudadas. Método: Participaram do estudo 12 crianças com DEL (GP) e 48 em desenvolvimento típico (GC) com idade entre 7 anos e 9 anos e 11 meses. Todos os sujeitos cursavam o 2º ou 3º ano do ensino fundamental I e apresentavam audição e rendimento intelectual não-verbal preservados. Para a seleção dos grupos foram utilizadas medidas de vocabulário receptivo, fonologia e nível socioeconômico. Já as medidas experimentais avaliadas foram testes padronizados de aliteração, rima, memória de curto prazo fonológica e a aplicação de um ditado de palavras e de pseudopalavras elaborados para esta pesquisa. Resultados: ambos os grupos apresentaram pior desempenho em tarefas de rima do que de aliteração e o GP apresentou desempenho inferior em ambas as tarefas quando comparado ao GC. A análise dos distratores nas atividades de aliteração e rima apontou que em tarefas de aliteração, o GP cometeu mais erros de tipologia semântico enquanto na prova de rima foram mais erros de tipologia fonológico. O GP obteve desempenho inferior ao GC nas avaliações da memória de curto prazo fonológica, ditado de palavras e de pseudopalavras. O GP evidenciou maior dificuldade no ditado de pseudopalavras no que no de palavras e o GC não apresentou diferença significativa no desempenho dos ditados. No ditado de palavras, o GP cometeu mais erros na palavra toda enquanto no ditado de pseudopalavras ocorreram mais erros na palavra toda e na sílaba final. Na comparação do desempenho dos grupos de acordo com a escolaridade, notou-se que os sujeitos do GC do 2º e 3º ano não evidenciaram diferença significativa em seu desempenho nas tarefas, enquanto os sujeitos do GP do 3º ano apresentaram melhor desempenho do que os do 2º ano em todas as medidas experimentais, com exceção da memória de curto prazo fonológica. Conclusões: o GP apresentou dificuldade em tarefas de processamento fonológico e de escrita que foram realizadas com relativa facilidade pelo GC. Os sujeitos com DEL evidenciaram uma análise mais global dos estímulos apresentados nas tarefas de consciência fonológica, o que os fez desprezar aspectos segmentais importantes. A dificuldade em abordar as informações de modo analítico, somado a alterações linguísticas e do processamento fonológico, levou o GP a apresentar maior taxa de erros nas tarefas de ditado. Apesar das alterações apontadas, os sujeitos do GP do 3º ano obtiveram melhor desempenho do que os do 2º ano em todas as habilidades com exceção da memória de curto prazo fonológica, que é sua marca clínica. Estes dados reforçam a necessidade do diagnóstico e intervenção precoces para esta população, onde as habilidades abordadas neste estudo devem ser incluídas no processo terapêutico

Human brain regions required for the dividing and switching of attention between two features of a single object

This combined PET and ERP study was designed to identify the brain regions activated in switching and divided attention between different features of a single object using matched sensory stimuli and motor response. The ERP data have previously been reported in this journal [64]. We now present the corresponding PET data. We identified partially overlapping neural networks with paradigms requiring the switching or dividing of attention between the elements of complex visual stimuli. Regions of activation were found in the prefrontal and temporal cortices and cerebellum. Each task resulted in different prefrontal cortical regions of activation lending support to the functional subspecialisation of the prefrontal and temporal cortices being based on the cognitive operations required rather than the stimuli themselves. (C) 2003 Elsevier Science B.V. All rights reserved.

Differential role of entorhinal and hippocampal nerve growth factor in short- and long-term memory modulation

We studied the effects of infusion of nerve growth factor (NGF) into the hippocampus and entorhinal cortex of male Wistar rats (250-300 g, N = 11-13 per group) on inhibitory avoidance retention. In order to evaluate the modulation of entorhinal and hippocampal NGF in short- and long-term memory, animals were implanted with cannulae in the CA1 area of the dorsal hippocampus or entorhinal cortex and trained in one-trial step-down inhibitory avoidance (foot shock, 0.4 mA). Retention tests were carried out 1.5 h or 24 h after training to measure short- and long-term memory, respectively. Immediately after training, rats received 5 µl NGF (0.05, 0.5 or 5.0 ng) or saline per side into the CA1 area and entorhinal cortex. The correct position of the cannulae was confirmed by histological analysis. The highest dose of NGF (5.0 ng) into the hippocampus blocked short-term memory (P < 0.05), whereas the doses of 0.5 (P < 0.05) and 5.0 ng (P < 0.01) NGF enhanced long-term memory. NGF administration into the entorhinal cortex improved long-term memory at the dose of 5.0 ng (P < 0.05) and did not alter short-term memory. Taken as a whole, our results suggest a differential modulation by entorhinal and hippocampal NGF of short- and long-term memory.

Errors in nonword repetition: bridging short- and long-term memory

According to the working memory model, the phonological loop is the component of working memory specialized in processing and manipulating limited amounts of speech-based information. The Children's Test of Nonword Repetition (CNRep) is a suitable measure of phonological short-term memory for English-speaking children, which was validated by the Brazilian Children's Test of Pseudoword Repetition (BCPR) as a Portuguese-language version. The objectives of the present study were: i) to investigate developmental aspects of the phonological memory processing by error analysis in the nonword repetition task, and ii) to examine phoneme (substitution, omission and addition) and order (migration) errors made in the BCPR by 180 normal Brazilian children of both sexes aged 4-10, from preschool to 4th grade. The dominant error was substitution [F(3,525) = 180.47; P < 0.0001]. The performance was age-related [F(4,175) = 14.53; P < 0.0001]. The length effect, i.e., more errors in long than in short items, was observed [F(3,519) = 108.36; P < 0.0001]. In 5-syllable pseudowords, errors occurred mainly in the middle of the stimuli, before the syllabic stress [F(4,16) = 6.03; P = 0.003]; substitutions appeared more at the end of the stimuli, after the stress [F(12,48) = 2.27; P = 0.02]. In conclusion, the BCPR error analysis supports the idea that phonological loop capacity is relatively constant during development, although school learning increases the efficiency of this system. Moreover, there are indications that long-term memory contributes to holding memory trace. The findings were discussed in terms of distinctiveness, clustering and redintegration hypotheses.

Errors in nonword repetition: bridging short- and long-term memory

According to the working memory model, the phonological loop is the component of working memory specialized in processing and manipulating limited amounts of speech-based information. The Children's Test of Nonword Repetition (CNRep) is a suitable measure of phonological short-term memory for English-speaking children, which was validated by the Brazilian Children's Test of Pseudoword Repetition (BCPR) as a Portuguese-language version. The objectives of the present study were: i) to investigate developmental aspects of the phonological memory processing by error analysis in the nonword repetition task, and ii) to examine phoneme (substitution, omission and addition) and order (migration) errors made in the BCPR by 180 normal Brazilian children of both sexes aged 4-10, from preschool to 4th grade. The dominant error was substitution [F(3,525) = 180.47; P < 0.0001]. The performance was age-related [F(4,175) = 14.53; P < 0.0001]. The length effect, i.e., more errors in long than in short items, was observed [F(3,519) = 108.36; P < 0.0001]. In 5-syllable pseudowords, errors occurred mainly in the middle of the stimuli, before the syllabic stress [F(4,16) = 6.03; P = 0.003]; substitutions appeared more at the end of the stimuli, after the stress [F(12,48) = 2.27; P = 0.02]. In conclusion, the BCPR error analysis supports the idea that phonological loop capacity is relatively constant during development, although school learning increases the efficiency of this system. Moreover, there are indications that long-term memory contributes to holding memory trace. The findings were discussed in terms of distinctiveness, clustering and redintegration hypotheses.

Astrocyte-neuron lactate transport is required for long-term memory formation.

We report that, in the rat hippocampus, learning leads to a significant increase in extracellular lactate levels that derive from glycogen, an energy reserve selectively localized in astrocytes. Astrocytic glycogen breakdown and lactate release are essential for long-term but not short-term memory formation, and for the maintenance of long-term potentiation (LTP) of synaptic strength elicited in vivo. Disrupting the expression of the astrocytic lactate transporters monocarboxylate transporter 4 (MCT4) or MCT1 causes amnesia, which, like LTP impairment, is rescued by L-lactate but not equicaloric glucose. Disrupting the expression of the neuronal lactate transporter MCT2 also leads to amnesia that is unaffected by either L-lactate or glucose, suggesting that lactate import into neurons is necessary for long-term memory. Glycogenolysis and astrocytic lactate transporters are also critical for the induction of molecular changes required for memory formation, including the induction of phospho-CREB, Arc, and phospho-cofilin. We conclude that astrocyte-neuron lactate transport is required for long-term memory formation.

Rolipram, a type IV-specific phosphodiesterase inhibitor, facilitates the establishment of long-lasting long-term potentiation and improves memory

In an attempt to improve behavioral memory, we devised a strategy to amplify the signal-to-noise ratio of the cAMP pathway, which plays a central role in hippocampal synaptic plasticity and behavioral memory. Multiple high-frequency trains of electrical stimulation induce long-lasting long-term potentiation, a form of synaptic strengthening in hippocampus that is greater in both magnitude and persistence than the short-lasting long-term potentiation generated by a single tetanic train. Studies using pharmacological inhibitors and genetic manipulations have shown that this difference in response depends on the activity of cAMP-dependent protein kinase A. Genetic studies have also indicated that protein kinase A and one of its target transcription factors, cAMP response element binding protein, are important in memory in vivo. These findings suggested that amplification of signals through the cAMP pathway might lower the threshold for generating long-lasting long-term potentiation and increase behavioral memory. We therefore examined the biochemical, physiological, and behavioral effects in mice of partial inhibition of a hippocampal cAMP phosphodiesterase. Concentrations of a type IV-specific phosphodiesterase inhibitor, rolipram, which had no significant effect on basal cAMP concentration, increased the cAMP response of hippocampal slices to stimulation with forskolin and induced persistent long-term potentiation in CA1 after a single tetanic train. In both young and aged mice, rolipram treatment before training increased long- but not short-term retention in freezing to context, a hippocampus-dependent memory task.

Pre and post-natal exposure to ambient level of air pollution impairs memory of rats: the role of oxidative stress

The aims of this study were to evaluate whether air pollution during pre-natal and post-natal phases change habituation and short-term discriminative memories and if oxidants are involved in this process. As secondary objectives, it was to evaluate if the change of filtered to nonfiltered environment could protect the cortex of rats against oxidative stress as well as to modify the behavior of these animals. Wistar, male rats were divided into four groups (n = 12/group): pre and post-natal exposure until adulthood to filtered air (FA); pre-natal period to nonfiltered air (NFA-FA); until (21st post-natal day) and post-natal to filtered air until adulthood (PND21); prenatal to filtered air until PND21 and post-natal to nonfiltered air until adulthood (FA-NFA); pre and post-natal to nonfiltered air (NFA). After 150 days of air pollution exposure, animals were tested in the spontaneous object recognition test to evaluate short-term discriminative and habituation memories. Rats were euthanized; blood was collected for metal determination; cortex dissected for oxidative stress evaluation. There was a significant increase in malondialdehyde (MDA) levels in the NFA group when compared to other groups (FA: 1.730 +/- 0.217; NFA-FA: 1.101 +/- 0.217; FA-NFA: 1.014 +/- 0.300; NFA: 5.978 +/- 1.920 nmol MDA/mg total proteins; p = 0.007). NFA group presented a significant decrease in short-term discriminative (FA: 0.603 +/- 0.106; NFA-FA: 0.669 +/- 0.0666; FA-NFA: 0.374 +/- 0.178; NFA: -0.00631 +/- 0.106 sec; p = 0.006) and an improvement in habituation memories when compared to other groups. Therefore, exposure to air pollution during both those periods impairs short-term discriminative memory and cortical oxidative stress may mediate this process.