Latent class analysis of attention and white matter correlation in children with attention-deficit/hyperactivity disorder

This study aimed to explore attentional patterns among children with inattentive attention-deficit/hyperactivity disorder (ADHD-I) and children with typical development (TD), using a latent class analysis (LCA). Patterns of brain connectivity were also explored. The sample comprised 29 ADHD-I and 29 TD matched children. An LCA was conducted to reclassify subjects according to their attentional performance, considering cognitive measures of attention and behavioral symptoms, regardless of group of origin. The new clusters were then compared in respect to brain white matter measurements (extracted from diffusion tensor imaging). Participants were rearranged in 2 new latent classes, according to their performance in an attention task and the results of behavioral scales, resulting in groups with more homogeneous attentional profiles. A comparison of the 2 new classes using the white matter measurements revealed increased fractional anisotropy in the left inferior fronto-occipital fasciculus and left inferior longitudinal fasciculus for the class composed by participants with a higher risk of attentional problems. The findings indicated that it was possible to observe variability regarding neuropsychological profile, accompanied by underpinning neurobiological differences, even among individuals with the same disorder subtype - inattentive ADHD. This specific data-driven clustering analysis may help to enhance understanding of the pathophysiology of the disorder's phenotypes.

Relationship among Apis mellifera L. stings, swarming and climate conditions in the city of Rio Claro, SP, Brazil

The presence of bees (Apis mellifera L.) in urban areas has increased in recent years due to environmental disturbances caused by humans. Bee migration to cities may provoke serious accidents, since some people present allergic reactions to their venoms. In Rio Claro city, São Paulo state, Brazil, the number of calls to the fire brigade for removal of bee swarms, and the number admissions in local hospitals due to bee stings were investigated during 2002 and 2003, and a correlation between these data and the average temperature, rainfall and relative humidity was found. The study period was divided into three phases according to the number of times that the fire brigade was called to remove swarms (263 times): January to July 2002 - 51 calls (19.39 percent); August 2002 to July 2003 - 140 calls (53.23 percent); and August to December 2003 - 72 calls (27.38 percent). A significant correlation among the number of calls, the local temperature and rainfall was detected. The number of accidents was not associated with environmental variables. Based on the current results, public activities for prevention of bee attacks may be developed to avoid unwanted contact between humans and these insects, and/or provide the appropriate management of the colonies.

Cognitive performance of young and elderly subjects on the free word recall memory test: effect of presentation order on recall order

The influence of aging on memory has been extensively studied, but the importance of short-term memory and recall sequence has not. The objective of the current study was to examine the recall order of words presented on lists and to determine if age affects recall sequence. Physically and psychologically healthy male subjects were divided into two groups according to age, i.e., 23 young subjects (20 to 30 years) and 50 elderly subjects (60 to 70 years) submitted to the Wechsler Adult Intelligence Scale-Revised and the free word recall test. The order of word presentation significantly affected the 3rd and 4th words recalled (P < 0.01; F = 14.6). In addition, there was interaction between the presentation order and the type of list presented (P < 0.05; F = 9.7). Also, both groups recalled the last words presented from each list (words 13-15) significantly more times 3rd and 4th than words presented in all remaining positions (P < 0.01). The order of word presentation also significantly affected the 5th and 6th words recalled (P = 0.05; F = 7.5) and there was a significant interaction between the order of presentation and the type of list presented (P < 0.01; F = 20.8). The more developed the cognitive functions, resulting mainly from formal education, the greater the cognitive reserve, helping to minimize the effects of aging on the long-term memory (episodic declarative).

Ant communities (Hymenoptera: Formicidae) in an urban ecosystem near the Atlantic Rainforest

The relationships between an urban ecosystem located near the Atlantic Rainforest in southeastern Brazil and ant communities were studied with the objective of quantifying the ant richness and abundance in the household environment and its surroundings. Eighty residences were sampled, where 58 species and 28 genera pertaining to 7 sub-families were found to be present. Inside the residences, the species richness was found to be lower (26), although the abundance was greater (10,670), with the wash area and kitchen being the locales that contributed with the greatest number of hits. The opposite was true in the areas outside the residences, where 54 species and 3,747 ants were observed. Inside houses, the species known as Tramp ants were found, in the following order of importance: Solenopsis -saevissima, Tapinoma melanocephalum, Linepithema humile, Paratrechina fulva, Wasmannia -auropunctata, P. -longicornis, Pheidole megacephala, Monomorium pharaonis and M. floricola. Externally, mainly in the yards and gardens, species such as Octostruma rugifera, Heteroponera dolo, Hypoponera sp.1 and sp.6, Gnamptogenys sp. 4, G. striatula, Odontomachus meinerti, Pachycondyla constricta and P. striata were found. In general, a greater number of species and lower abundance of individuals were observed in the neighborhoods nearer the mountains than in those closer to the urban center.

A relação entre um ecossistema urbano localizado próximo à Mata Atlântica na região sudeste do Brasil e as comunidades de formigas foi estudada com o objetivo de quantificar a riqueza e a abundância de formigas no interior e no entorno das residências. Oitenta casas foram amostradas, tendo sido encontradas 58 espécies e 28 gêneros pertencentes a 7 subfamílias. No interior das residências foi encontrada uma baixa riqueza de espécies (26) e um alto número de indivíduos (10.670), sendo a área de serviço e a cozinha os locais que mais contribuíram para esse resultado. Já no entorno das residências foram encontradas 54 espécies e 3.747 indivíduos. No interior das casas, as espécies conhecidas como 'Tramp - ants" foram encontradas na seguinte ordem de importância: Solenopsis -saevissima, Tapinoma -melanocephalum, Linepithema humile, Paratrechina fulva, Wasmannia auropunctata, P. longicornis, Pheidole -megacephala, Monomorium pharaonis e M. floricola. Externamente, principalmente no jardim e quintal, foram encontradas espécies como: Octostruma rugifera, Heteroponera dolo, Hypoponera sp.1 e sp.6, Gnamptogenys sp.4, G. -striatula, Odontomachus meinerti, Pachycondyla constricta e P. striata. Em geral, o maior número de espécies e baixa abundância de indivíduos foram observados em bairros próximos às áreas de mata.

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.

Low variation in ribosomal DNA and internal transcribed spacers of the symbiotic fungi of leaf-cutting ants (Attini: Formicidae)

Leaf-cutting ants of the genera Atta and Acromyrmex (tribe Attini) are symbiotic with basidiomycete fungi of the genus Leucoagaricus (tribe Leucocoprineae), which they cultivate on vegetable matter inside their nests. We determined the variation of the 28S, 18S, and 5.8S ribosomal DNA (rDNA) gene loci and the rapidly evolving internal transcribed spacers 1 and 2 (ITS1 and ITS2) of 15 sympatric and allopatric fungi associated with colonies of 11 species of leafcutter ants living up to 2,600 km apart in Brazil. We found that the fungal rDNA and ITS sequences from different species of ants were identical (or nearly identical) to each other, whereas 10 GenBank Leucoagaricus species showed higher ITS variation. Our findings suggest that Atta and Acromyrmex leafcutters living in geographic sites that are very distant from each other cultivate a single fungal species made up of closely related lineages of Leucoagaricus gongylophorus. We discuss the strikingly high similarity in the ITS1 and ITS2 regions of the Atta and Acromyrmex symbiotic L. gongylophorus studied by us, in contrast to the lower similarity displayed by their non-symbiotic counterparts. We suggest that the similarity of our L. gongylophorus isolates is an indication of the recent association of the fungus with these ants, and propose that both the intense lateral transmission of fungal material within leafcutter nests and the selection of more adapted fungal strains are involved in the homogenization of the symbiotic fungal stock.

Validation of the Brazilian Children's Test of Pseudoword Repetition in Portuguese speakers aged 4 to 10 years

The phonological loop is a component of the working memory system specifically involved in the processing and manipulation of limited amounts of information of a sound-based phonological nature. Phonological memory can be assessed by the Children's Test of Nonword Repetition (CNRep) in English speakers but not in Portuguese speakers due to phonotactic differences between the two languages. The objectives of the present study were: 1) to develop the Brazilian Children's Test of Pseudoword Repetition (BCPR), a Portuguese version of the CNRep, and 2) to validate the BCPR by correlation with the Auditory Digit Span Test from the Stanford-Binet Intelligence Scale. The BCPR and Digit Span were assessed in 182 children aged 4-10 years, 84 from Minas Gerais State (42 from a rural region) and 98 from the city of Säo Paulo. There are subject age and word length effects causing repetition accuracy to decline as a function of the number of syllables of the pseudowords. Correlations between BCPR and Digit Span forward (r = 0.50; P <= 0.01) and backward (r = 0.43; P <= 0.01) were found, and partial correlation indicated that higher BCPR scores were associated with higher Digit Span scores. BCPR appears to depend more on schooling, while Digit Span was more related to development. The results demonstrate that the BCPR is a reliable measure of phonological working memory, similar to the CNRep.

Sistema para análise simultânea de quatro potenciais evocados visuais multicanais utilizando equipamento comercial e processamento off-line / A system for the simultaneous analysis of four multichannel visual evoked potentials using a commercial equipment and off line processing

Numa proposta de pesquisa para estudar os correlatos eletrofisiológicos de processamento semântico de palavras apresentadas visualmente pretendia-se captar (e processar) quatro potenciais evocados cerebrais de algumas derivações num mesmo experimento, utilizando um equipamento comercial usado em centros hospitalares. Para viabilizar tal pesquisa, foi criado um protocolo especial, em que duas respostas visuais evocadas seqüencialmente, com uma latência de 4,15 s, eram adquiridas em uma mesma janela de aquisição. Como a taxa de amostragem resultante no equipamento foi adequada para a aplicação (100 Hz), foi possível realizar o experimento no próprio centro hospitalar, utilizando um equipamento com o qual os pesquisadores da área biomédica estavam bem familiarizados. Um problema adicional surgiu no tocante a artefatos por movimentação ocular. Este foi sanado graças à possibilidade de serem arquivadas todas as respostas individuais, e não somente a média coerente. Um algoritmo simples realizou a detecção de artefatos de forma eficiente. As soluções encontradas possibilitaram a realização da pesquisa proposta, sendo que essas mesmas soluções poderão permitir trabalhos em outros centos que se deparem com uma problemática semelhante à descrita.

The brain decade in debate: I. Neurobiology of learning and memory

This article is a transcription of an electronic symposium in which some active researchers were invited by the Brazilian Society for Neuroscience and Behavior (SBNeC) to discuss the last decade's advances in neurobiology of learning and memory. The way different parts of the brain are recruited during the storage of different kinds of memory (e.g., short-term vs long-term memory, declarative vs procedural memory) and even the property of these divisions were discussed. It was pointed out that the brain does not really store memories, but stores traces of information that are later used to create memories, not always expressing a completely veridical picture of the past experienced reality. To perform this process different parts of the brain act as important nodes of the neural network that encode, store and retrieve the information that will be used to create memories. Some of the brain regions are recognizably active during the activation of short-term working memory (e.g., prefrontal cortex), or the storage of information retrieved as long-term explicit memories (e.g., hippocampus and related cortical areas) or the modulation of the storage of memories related to emotional events (e.g., amygdala). This does not mean that there is a separate neural structure completely supporting the storage of each kind of memory but means that these memories critically depend on the functioning of these neural structures. The current view is that there is no sense in talking about hippocampus-based or amygdala-based memory since this implies that there is a one-to-one correspondence. The present question to be solved is how systems interact in memory. The pertinence of attributing a critical role to cellular processes like synaptic tagging and protein kinase A activation to explain the memory storage processes at the cellular level was also discussed

Anterograde effects of a single electroconvulsive shock on inhibitory avoidance and on cued fear conditioning

A single electroconvulsive shock (ECS) or a sham ECS was administered to male 3-4-month-old Wistar rats 1,2, and 4 h before training in an inhibitory avoidance test and in cued classical fear conditioning (measured by means of freezing time in a new environment). ECS impaired inhibitory avoidance at all times and, at 1 or 2 h before training, reduced freezing time before and after re-presentation of the ECS. These results are interpreted as a transient conditioned simulus (CS)-induced anxiolytic or analgesic effect lasting about 2 h after a single treatment, in addition to the known amnesic effect of the stimulus. This suggests that the effect of anterograde learning impairement is demonstrated unequivocally only when the analgesic/anxiolytic effect is over (about 4 h after ECS administration) and that this impairment of learning is selective, affecting inhibitory avoidance but not classical fear conditioning to a discrete stimulus.

Rats do react to stimulus omission

1. The great majority of data supporting the hypothesis of a systemcapable of compararing current sensorial imputs with and internal representation of the environment comes from studies about exploratory activity to new stimuli or to manipulation of features of a familiar stimulus. On the other hand, these data could also be explained simply by arousal constructs. In this context, demonstrations of exploratory behavior to the absence of a previously presented stimulus (i.e., stimulus omission) would provide stronger support for the idea of a comparator. 2. To test the reaction of rats to the absence of a stimulus, rats were submitted to 7 exploratory trials in an open-field. In the 1st trial there were only two patterns on the apparatus wall. In trials 2-6 a stimulus was presented in a designated area of the field. Finally, in the 7th trial this stimulus was omitted. Results showed that the animals reacted to the stimulus omission by spending more time in the stimulus presentation place during the 7th trial than 1) in the 1st trial (also without stimulus), 2) in the 6th trial (last trial with a stimulus present), and 3) in 3 neutral sectors of the same size as the stimulus presentation place, during the 7th trial. 3. These data indicated thath rats do react to the absence of a familiar stimulus and provide strong support for the existence of a Comparator System since the rats responded to "something that wasn't there anymore", a response that could only be due to a reaction triggered by a mismatch between internal representation of the environment and its present state

Ethanol decreases choice accuracy in a radial maze delayed test

1. The effect of acute ethanol on memory was studied in an eight-arm radial maze by interposing a 15-s or 1-h delay between the rat's fourth and fifth arma choices. 2. Ethanol (1.0g/Kg) was injected intraperitoneally 5 min prior to the firsrt set of 4-arm choices, therefore being presrnt since the acquisition of the trial-unique event. 3. The results showed 1) a decrease in choice accuracu only in the final 4 arm choices after the 1-h delay, and 2) that errors consisted of re-entries into arms chosen before the delay was imposed. The data further support the contention that ethanol impairs retention of working memory