Vectorizing the spatial structure of high-harmonic radiation from gas.

Strong field laser physics has primarily been concerned with controlling beams in time while keeping their spatial profiles invariant. In the case of high harmonic generation, the harmonic beam is the result of the coherent superposition of atomic dipole emissions. Therefore, fundamental beams can be tailored in space, and their spatial characteristics will be imparted onto the harmonics. Here we produce high harmonics using a space-varying polarized fundamental laser beam, which we refer to as a vector beam. By exploiting the natural evolution of a vector beam as it propagates, we convert the fundamental beam into high harmonic radiation at its focus where the polarization is primarily linear. This evolution results in circularly polarized high harmonics in the far field. Such beams will be important for ultrafast probing of magnetic materials.

High resolution spectroscopy of six SOCl2 isotopologues from the microwave to the far-infrared.

Despite its potential role as an atmospheric pollutant, thionyl chloride, SOCl2, remains poorly characterized in the gas phase. In this study, the pure rotational and ro-vibrational spectra of six isotopologues of this molecule, all detected in natural abundance, have been extensively studied from the cm-wave band to the far-infrared region by means of three complementary techniques: chirped-pulse Fourier transform microwave spectroscopy, sub-millimeter-wave spectroscopy using frequency multiplier chain, and synchrotron-based far-infrared spectroscopy. Owing to the complex line pattern which results from two nuclei with non-zero spins, new, high-level quantum-chemical calculations of the hyperfine structure played a crucial role in the spectroscopic analysis. From the combined experimental and theoretical work, an accurate semi-experimental equilibrium structure (r(e)(SE)) of SOCl2 has been derived. With the present data, spectroscopy-based methods can now be applied with confidence to detect and monitor this species, either by remote sensing or in situ.

Enchytraeid abundance in Araucaria Mixed Forest determined by cold and hot wet extraction.

Enchytraeids are small oligochaetes found worldwide in soils with sufficient moisture and organic matter, but scarcely studied in the Southern hemisphere. This is the third study on enchytraeid abundance in Brazil using wet extraction and the first carried out in Araucaria Mixed Forest (subtropical region). The sampling and extraction were based on the standard method ISO 23611-3/2007 using an adapted split soil corer and wet extraction with and without heat to assess the abundance of enchytraeids in a forest fragment at Embrapa Forestry in Colombo, Paraná State. The samplings were performed in 3 occasions between September 2011 and April 2012. The average numbers estimated by each method varied from appr. 2.000-12.000 (cold) and 5.000-12.000 ind./ m2 (hot), respectively, with a maximum of 44.000 ind./ m2 in one of the samples, the highest value reported so far in Brazil. The hot extraction was more advantageous, given the speed and preservation of the specimens in vivo, allowing taxonomic identification. Advantages and disadvantages of wet extractions compared to handsorting and formol methods are also discussed. Guaranidrilus, Hemienchytraeus, Enchytraeus, Fridericia and Achaeta were the genera identified in the samples.

Enchytraeid abundance in Araucaria Mixed Forest determined by cold and hot wet extraction / Abundância de enquitreídeos na Floresta Ombrófila Mista determinada por extração úmida quente e fria

Abstract Enchytraeids are small oligochaetes found worldwide in soils with sufficient moisture and organic matter, but scarcely studied in the Southern hemisphere. This is the third study on enchytraeid abundance in Brazil using wet extraction and the first carried out in Araucaria Mixed Forest (subtropical region). The sampling and extraction were based on the standard method ISO 23611-3/2007 using an adapted split soil corer and wet extraction with and without heat to assess the abundance of enchytraeids in a forest fragment at Embrapa Forestry in Colombo, Paraná State. The samplings were performed in 3 occasions between September 2011 and April 2012. The average numbers estimated by each method varied from appr. 2.000-12.000 (cold) and 5.000-12.000 ind./ m2 (hot), respectively, with a maximum of 44.000 ind./ m2 in one of the samples, the highest value reported so far in Brazil. The hot extraction was more advantageous, given the speed and preservation of the specimens in vivo, allowing taxonomic identification. Advantages and disadvantages of wet extractions compared to handsorting and formol methods are also discussed. Guaranidrilus, Hemienchytraeus, Enchytraeus, Fridericia and Achaeta were the genera identified in the samples.

Resumo Os enquitreídeos são pequenos oligoquetas encontrados no mundo todo em solos com suficiente umidade e matéria orgânica, porém muito pouco estudados no hemisfério Sul. Este é o terceiro estudo sobre a abundância de enquitreídeos no Brasil utilizando o método de extração úmida e o primeiro realizado em Floresta Ombrófila Mista (região subtropical). A amostragem e extração foram baseadas no método padrão ISO 23611-3/2007, utilizando-se um trado desmontável adaptado e extração úmida com e sem aquecimento para acessar a abundância de enquitreídeo em um fragmento de floresta na Embrapa Florestas em Colombo, Paraná. As amostragens foram realizadas em três ocasiões entre setembro, 2011 e abril 2012. Os números médios estimados através de cada método variaram de 2.000-12.000 (frio) e 5.000-12.000 ind./ m2 (quente), respectivamente, e o máximo de 44.000 ind./ m2 em uma das amostras, o mais alto já relatado no Brasil. A extração quente foi a mais vantajosa, considerando a rapidez e preservação dos exemplares in vivo. As vantagens e desvantagens das extrações úmidas comparadas aos métodos de triagem manual e extração com formol foram discutidas. Os gêneros Guaranidrilus, Hemienchytraeus, Enchytraeus, Fridericia e Achaeta foram identificados nas amostras.

Enchytraeid abundance in Araucaria Mixed Forest determined by cold and hot wet extraction

Abstract Enchytraeids are small oligochaetes found worldwide in soils with sufficient moisture and organic matter, but scarcely studied in the Southern hemisphere. This is the third study on enchytraeid abundance in Brazil using wet extraction and the first carried out in Araucaria Mixed Forest (subtropical region). The sampling and extraction were based on the standard method ISO 23611-3/2007 using an adapted split soil corer and wet extraction with and without heat to assess the abundance of enchytraeids in a forest fragment at Embrapa Forestry in Colombo, Paraná State. The samplings were performed in 3 occasions between September 2011 and April 2012. The average numbers estimated by each method varied from appr. 2.000-12.000 (cold) and 5.000-12.000 ind./ m2 (hot), respectively, with a maximum of 44.000 ind./ m2 in one of the samples, the highest value reported so far in Brazil. The hot extraction was more advantageous, given the speed and preservation of the specimens in vivo, allowing taxonomic identification. Advantages and disadvantages of wet extractions compared to handsorting and formol methods are also discussed. Guaranidrilus, Hemienchytraeus, Enchytraeus, Fridericia and Achaeta were the genera identified in the samples.

Resumo Os enquitreídeos são pequenos oligoquetas encontrados no mundo todo em solos com suficiente umidade e matéria orgânica, porém muito pouco estudados no hemisfério Sul. Este é o terceiro estudo sobre a abundância de enquitreídeos no Brasil utilizando o método de extração úmida e o primeiro realizado em Floresta Ombrófila Mista (região subtropical). A amostragem e extração foram baseadas no método padrão ISO 23611-3/2007, utilizando-se um trado desmontável adaptado e extração úmida com e sem aquecimento para acessar a abundância de enquitreídeo em um fragmento de floresta na Embrapa Florestas em Colombo, Paraná. As amostragens foram realizadas em três ocasiões entre setembro, 2011 e abril 2012. Os números médios estimados através de cada método variaram de 2.000-12.000 (frio) e 5.000-12.000 ind./ m2 (quente), respectivamente, e o máximo de 44.000 ind./ m2 em uma das amostras, o mais alto já relatado no Brasil. A extração quente foi a mais vantajosa, considerando a rapidez e preservação dos exemplares in vivo. As vantagens e desvantagens das extrações úmidas comparadas aos métodos de triagem manual e extração com formol foram discutidas. Os gêneros Guaranidrilus, Hemienchytraeus, Enchytraeus, Fridericia e Achaeta foram identificados nas amostras.

Auditory oddball deficits in schizophrenia: an independent component analysis of the fMRI multisite function BIRN study.

Deficits in the connectivity between brain regions have been suggested to play a major role in the pathophysiology of schizophrenia. A functional magnetic resonance imaging (fMRI) analysis of schizophrenia was implemented using independent component analysis (ICA) to identify multiple temporally cohesive, spatially distributed regions of brain activity that represent functionally connected networks. We hypothesized that functional connectivity differences would be seen in auditory networks comprised of regions such as superior temporal gyrus as well as executive networks that consisted of frontal-parietal areas. Eight networks were found to be implicated in schizophrenia during the auditory oddball paradigm. These included a bilateral temporal network containing the superior and middle temporal gyrus; a default-mode network comprised of the posterior cingulate, precuneus, and middle frontal gyrus; and multiple dorsal lateral prefrontal cortex networks that constituted various levels of between-group differences. Highly task-related sensory networks were also found. These results indicate that patients with schizophrenia show functional connectivity differences in networks related to auditory processing, executive control, and baseline functional activity. Overall, these findings support the idea that the cognitive deficits associated with schizophrenia are widespread and that a functional connectivity approach can help elucidate the neural correlates of this disorder.

Working memory and DLPFC inefficiency in schizophrenia: the FBIRN study.

BACKGROUND: The Functional Imaging Biomedical Informatics Network is a consortium developing methods for multisite functional imaging studies. Both prefrontal hyper- or hypoactivity in chronic schizophrenia have been found in previous studies of working memory. METHODS: In this functional magnetic resonance imaging (fMRI) study of working memory, 128 subjects with chronic schizophrenia and 128 age- and gender-matched controls were recruited from 10 universities around the United States. Subjects performed the Sternberg Item Recognition Paradigm1,2 with memory loads of 1, 3, or 5 items. A region of interest analysis examined the mean BOLD signal change in an atlas-based demarcation of the dorsolateral prefrontal cortex (DLPFC), in both groups, during both the encoding and retrieval phases of the experiment over the various memory loads. RESULTS: Subjects with schizophrenia performed slightly but significantly worse than the healthy volunteers and showed a greater decrease in accuracy and increase in reaction time with increasing memory load. The mean BOLD signal in the DLPFC was significantly greater in the schizophrenic group than the healthy group, particularly in the intermediate load condition. A secondary analysis matched subjects for mean accuracy and found the same BOLD signal hyperresponse in schizophrenics. CONCLUSIONS: The increase in BOLD signal change from minimal to moderate memory loads was greater in the schizophrenic subjects than in controls. This effect remained when age, gender, run, hemisphere, and performance were considered, consistent with inefficient DLPFC function during working memory. These findings from a large multisite sample support the concept not of hyper- or hypofrontality in schizophrenia, but rather DLPFC inefficiency that may be manifested in either direction depending on task demands. This redirects the focus of research from direction of difference to neural mechanisms of inefficiency.

fMRI activity correlated with auditory hallucinations during performance of a working memory task: data from the FBIRN consortium study.

INTRODUCTION: Auditory hallucinations are a hallmark symptom of schizophrenia. The neural basis of auditory hallucinations was examined using data from a working memory task. Data were acquired within a multisite consortium and this unique dataset provided the opportunity to analyze data from a large number of subjects who had been tested on the same procedures across sites. We hypothesized that regions involved in verbal working memory and language processing would show activity that was associated with levels of hallucinations during a condition where subjects were rehearsing the stimuli. METHODS: Data from the Sternberg Item Recognition Paradigm, a working memory task, were acquired during functional magnetic resonance imaging procedures. The data were collected and preprocessed by the functional imaging biomedical informatics research network consortium. Schizophrenic subjects were split into nonhallucinating and hallucinating subgroups and activity during the probe condition (in which subjects rehearsed stimuli) was examined. Levels of activation from contrast images for the probe phase (collapsed over levels of memory load) of the working memory task were also correlated with levels of auditory hallucinations from the Scale for the Assessment of Positive Symptoms scores. RESULTS: Patients with auditory hallucinations (relative to nonhallucinating subjects) showed decreased activity during the probe condition in verbal working memory/language processing regions, including the superior temporal and inferior parietal regions. These regions also showed associations between activity and levels of hallucinations in a correlation analysis. DISCUSSION: The association between activation and hallucinations scores in the left hemisphere language/working memory regions replicates the findings of previous studies and provides converging evidence for the association between superior temporal abnormalities and auditory hallucinations.

The effects of total sleep deprivation on cerebral responses to cognitive performance.

We review the findings from a study utilizing functional magnetic resonance imaging (FMRI) to examine the effects of total sleep deprivation (TSD) on verbal learning, arithmetic, and divided attention. For verbal learning and divided attention, TSD was associated with increased activation in the bilateral prefrontal cortex and parietal lobes. Increased sleepiness after TSD and lower levels of memory impairment were correlated with increased activation in specific regions of the prefrontal cortex and parietal lobes, respectively. The arithmetic task led to significantly decreased activation in the bilateral prefrontal cortex and parietal lobes. Based on this and other data, we hypothesize an adaptive cerebral response during cognitive performance following TSD with the specific pattern of adaptation depending on the specific cognitive processes performed. We discuss the need to test the hypothesis in a variety of ways.

Sleep deprivation, EEG, and functional MRI in depression: preliminary results.

One night of total or partial sleep deprivation (SD) produces temporary remissions in 40-60% of patients with major depression. Two unmedicated patients with major depression and a matched control received quantitative perfusion MR images at baseline and after one night of partial SD (PSD). A reduction > or =30% in the 17-item Hamilton Depression Rating Scale (omitting sleep and weight loss items) defined antidepressant response. Theory, techniques, strengths and weaknesses of quantitative perfusion MRI are described in detail. At baseline, the responder exhibited elevated perfusion covering ventral anterior cingulate/medial frontal cortex; the control's maximal perfusion area was markedly smaller. The nonresponder's perfusion was lowest of all, particularly ventrally. PSD decreased perfusion over much of the responder's hyperperfused area but did not change the nonresponder's scan. These preliminary findings are consistent with previous SD studies using PET and SPECT.

Chemical pathology in brain white matter of recently detoxified alcoholics: a 1H magnetic resonance spectroscopy investigation of alcohol-associated frontal lobe injury.

BACKGROUND: Investigations have suggested that frontal lobe abnormalities are a prominent feature of the alcoholic brain, indicated by impaired neuropsychological performance on tests of frontal lobe function and by reduced frontal lobe volume in neuroimaging and neuropathological examinations. White matter compartment volume loss may underlie observed brain shrinkage and cognitive deficits associated with the frontal lobes, although the nature of this change has not been well-characterized. METHOD: To investigate the susceptibility of frontal lobe white matter to alcohol-associated metabolic change and to understand the nature of alcohol-related white matter injury, 1H magnetic resonance spectroscopy (MRS) was used to measure concentrations of metabolites in frontal white matter (FWM) and parietal white matter (PWM) of recently detoxified alcoholics (RDA) and nonalcoholic controls (CON). Concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), myo-inositol (Ins), and creatine plus phosphocreatine (Cr) were measured in 37 RDA (mean age, 40.4 years; mean length of abstinence, 27.9 days) and 15 CON (mean age, 38.0 years). RESULTS: Analysis of variance (ANOVA) revealed a group by region of interest interaction for concentrations of NAA. Simple effects analysis revealed a significant 14.7% reduction in FWM NAA, while NAA levels in PWM were similar in RDA and CON. In addition, RDA had an 11.8% increase (averaged across both regions of interest) in brain white matter Ins relative to CON. Reductions in FWM NAA were associated with a longer drinking history in the RDA group, but this result was not found when both age and drinking history were used to predict the level of FWM NAA. CONCLUSIONS: Alcohol-associated reductions in FWM NAA may be the result of neuronal loss or dysfunction in the metabolism of NAA. While alcohol-induced oxidative stress may cause global brain impairments in the metabolism and subsequent reduction of NAA, the frontal lobes are particularly rich in excitatory amino acid pathways, and axonal damage or destruction secondary to glutamate-mediated excitotoxicity during alcohol withdrawal may cause frontal lobe-specific reductions in NAA. Elevations in brain white matter Ins may reflect astrocyte proliferation as well as an osmotic response to cell shrinkage.

Increased cerebral response during a divided attention task following sleep deprivation.

We recently reported that the brain showed greater responsiveness to some cognitive demands following total sleep deprivation (TSD). Specifically, verbal learning led to increased cerebral activation following TSD while arithmetic resulted in decreased activation. Here we report data from a divided attention task that combined verbal learning and arithmetic. Thirteen normal control subjects performed the task while undergoing functional magnetic resonance imaging (FMRI) scans after a normal night of sleep and following 35 h TSD. Behaviourally, subjects showed only modest impairments following TSD. With respect to cerebral activation, the results showed (a) increased activation in the prefrontal cortex and parietal lobes, particularly in the right hemisphere, following TSD, (b) activation in left inferior frontal gyrus correlated with increased subjective sleepiness after TSD, and (c) activation in bilateral parietal lobes correlated with the extent of intact memory performance after TSD. Many of the brain regions showing a greater response after TSD compared with normal sleep are thought to be involved in control of attention. These data imply that the divided attention task required more attentional resources (specifically, performance monitoring and sustained attention) following TSD than after normal sleep. Other neuroimaging results may relate to the verbal learning and/or arithmetic demands of the task. This is the first study to examine divided attention performance after TSD with neuroimaging and supports our previous suggestion that the brain may be more plastic during cognitive performance following TSD than previously thought.

fMRI measurement of brain dysfunction in alcohol-dependent young women.

BACKGROUND: Studies of brain functioning in alcohol-dependent adults have produced varied results but generally suggest that alcohol affects brain functioning and that relatively short durations of heavy drinking may adversely affect women. It remains unclear when in the course of alcohol dependency and at which developmental stage these brain changes emerge. Our neuropsychological studies have indicated that drinking-related neurocognitive effects occur as early as adolescence (Brown et al., 2000; Tapert & Brown, 1999). This study seeks to characterize brain regions that subserve the affected neurocognitive functions. METHODS: Alcohol-dependent young women (n = 10) were recruited from a longitudinal study of alcohol- and drug-abusing youth, all of whom met criteria for alcohol dependence. Control participants (n = 10) had no history of alcohol or drug problems and were comparable with alcohol-dependent participants on age (18-25 years), family history of alcohol use disorders, and education. After a minimum of 72 hr of abstinence, functional magnetic resonance imaging, neuropsychological, alcohol/drug involvement, and mood data were collected. Participants performed spatial working memory and vigilance tasks during functional magnetic resonance imaging acquisition to probe brain response. RESULTS: Alcohol-dependent women demonstrated significantly less blood oxygen level-dependent response than controls during the spatial working memory task in the right superior and inferior parietal, right middle frontal, right postcentral, and left superior frontal cortex, after controlling for the baseline vigilance response. CONCLUSIONS: Working memory produces a larger neuronal response in some cortical regions than vigilance. Alcohol-dependent women showed less differential response to working memory than controls in frontal and parietal regions, especially in the right hemisphere. Heavy, chronic drinking appears to produce adverse neural effects that are detectable by functional magnetic resonance imaging.

Prefrontal, parietal, and temporal cortex networks underlie decision-making in the presence of uncertainty.

Decision-making in the presence of uncertainty, i.e., selecting a sequence of responses in an uncertain environment according to a self-generated plan of action, is a complex activity that involves both cognitive and noncognitive processes. Using functional magnetic resonance imaging, the neural substrates of decision-making in the presence of uncertainty are examined. Normal control subjects show a significant activation of a frontoparietal and limbic neural system during a two-choice prediction task relative to a two-choice response task. The most prevalent response strategy during the two-choice prediction task was "win-stay/lose-shift," where subjects will repeat the previous response if it successfully predicted the stimulus and switch to the alternative response otherwise. Increased frequency of responses that are consistent with this strategy is associated with activation in the superior temporal gyrus. In comparison, increased frequency of response inconsistent with win-stay/lose-shift is associated with parietal cortex activation. These results support the hypothesis that subjects use a frontoparietal neural system to establish a contingency based decision-making strategy even in the presence of random reinforcement.

Altered brain response to verbal learning following sleep deprivation.

The effects of sleep deprivation on the neural substrates of cognition are poorly understood. Here we used functional magnetic resonance imaging to measure the effects of 35 hours of sleep deprivation on cerebral activation during verbal learning in normal young volunteers. On the basis of a previous hypothesis, we predicted that the prefrontal cortex (PFC) would be less responsive to cognitive demands following sleep deprivation. Contrary to our expectations, however, the PFC was more responsive after one night of sleep deprivation than after normal sleep. Increased subjective sleepiness in sleep-deprived subjects correlated significantly with activation of the PFC. The temporal lobe was activated after normal sleep but not after sleep deprivation; in contrast, the parietal lobes were not activated after normal sleep but were activated after sleep deprivation. Although sleep deprivation significantly impaired free recall compared with the rested state, better free recall in sleep-deprived subjects was associated with greater parietal lobe activation. These findings show that there are dynamic, compensatory changes in cerebral activation during verbal learning after sleep deprivation and implicate the PFC and parietal lobes in this compensation.

Executive functions and P300 latency in elderly depressed patients and control subjects.

The authors asked whether impaired executive functioning and long P300 latency are related dysfunctions and whether they are associated with geriatric depression. A group of 25 elderly depressed patients without dementia and 20 control subjects were assessed on tasks of fluency, initiation and perseveration, the Stroop task, the Wisconsin Card Sorting Test (WCST) perseverative error score, and P300 latency. The groups' performance differed significantly on these tasks and in P300 latency. Longer latency was associated with poorer performance in both groups on all measures except WCST perseverative errors. Regardless of patients' depression status, increased P300 latency predicts poorer performance on executive function tasks requiring speeded performance.

Lexical priming on Neely's (1977) paradigm in Parkinson's disease: where do we stand?

In two published studies, we used a variant of Neely's (1977) lexical decision paradigm to study shifts of attention and automatic lexical activation in nondemented individuals with Parkinson's disease (McDonald, Brown, & Gorell, 1996; Spicer, Brown, & Gorell, 1994). Arnott and Chenery (in press) noticed differences between Neely's results and the results we observed in our control group that raise questions about some of the conclusions presented in the McDonald et al. (1996) and Spicer et al. (1994) papers. Even when considering the important differences between Neely's (1977) results and those in our control groups, we argue that our results support the conclusions of normal automatic semantic activation and deficient set-shifting in Parkinson's disease. We also introduce the notion of generalized priming to account for some of the priming effects observed in our studies.

Occupational exposure to manganese, copper, lead, iron, mercury and zinc and the risk of Parkinson's disease.

A population-based case-control study was conducted in the Henry Ford Health System (HFHS) in metropolitan Detroit to assess occupational exposures to manganese, copper, lead, iron, mercury and zinc as risk factors for Parkinson's disease (PD). Non-demented men and women 50 years of age who were receiving primary medical care at HFHS were recruited, and concurrently enrolled cases (n = 144) and controls (n = 464) were frequency-matched for sex, race and age (+/- 5 years). A risk factor questionnaire, administered by trained interviewers, inquired about every job held by each subject for 6 months from age 18 onward, including a detailed assessment of actual job tasks, tools and environment. An experienced industrial hygienist, blinded to subjects' case-control status, used these data to rate every job as exposed or not exposed to one or more of the metals of interest. Adjusting for sex, race, age and smoking status, 20 years of occupational exposure to any metal was not associated with PD. However, more than 20 years exposure to manganese (Odds Ratio [OR] = 10.61, 95% Confidence Interval [CI] = 1.06, 105.83) or copper (OR = 2.49, 95% CI = 1.06,5.89) was associated with PD. Occupational exposure for > 20 years to combinations of lead-copper (OR = 5.24, 95% CI = 1.59, 17.21), lead-iron (OR = 2.83, 95% CI = 1.07,7.50), and iron-copper (OR = 3.69, 95% CI = 1.40,9.71) was also associated with the disease. No association of occupational exposure to iron, mercury or zinc with PD was found. A lack of statistical power precluded analyses of metal combinations for those with a low prevalence of exposure (i.e., manganese, mercury and zinc). Our findings suggest that chronic occupational exposure to manganese or copper, individually, or to dual combinations of lead, iron and copper, is associated with PD.

Brain activation and pupil response during covert performance of the Stroop Color Word task.

Patterns of brain activation associated with covert performance of the Stroop Color-Word task were studied in young, healthy, adult volunteers using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). Comparisons of the incongruous Stroop condition were made with both color naming and word reading baselines. Areas of the left and right anterior cingulate, the right precuneus, and the left pars opercularis displayed larger BOLD signal responses during the incongruous Stroop condition than during baseline conditions. Activation of BOLD signals in these areas was highly repeatable. In a second experiment, pupil diameter was used to assess cognitive load in 7 individuals studied during overt and covert performance of both Stroop and color naming conditions. Cognitive load was similar in overt and covert response conditions. Results from the BOLD study indicate that brain regions participating in selective visual attention and in the selection of motor programs involved in speech were activated more by the Stroop task than by the baseline tasks. The neural substrate involved in the resolution of the perceptual and motor conflicts elicited by the Stroop Color-Word task does not appear to be a single brain region. Rather, a network of brain regions is implicated, with separate regions within this system supporting distinct functions.

CLK-1 controls respiration, behavior and aging in the nematode Caenorhabditis elegans.

Mutations in the clk-1 gene of the nematode Caenorhabditis elegans result in an average slowing of a variety of developmental and physiological processes, including the cell cycle, embryogenesis, post-embryonic growth, rhythmic behaviors and aging. In yeast, a CLK-1 homologue is absolutely required for ubiquinone biosynthesis and thus respiration. Here we show that CLK-1 is fully active when fused to green fluorescent protein and is found in the mitochondria of all somatic cells. The activity of mutant mitochondria, however, is only very slightly impaired, as measured in vivo by a dye-uptake assay, and in vitro by the activity of succinate cytochrome c reductase. Overexpression of CLK-1 activity in wild-type worms can increase mitochondrial activity, accelerate behavioral rates during aging and shorten life span, indicating that clk-1 regulates and controls these processes. These observations also provide strong genetic evidence that mitochondria are causally involved in aging. Furthermore, the reduced respiration of the long-lived clk-1 mutants suggests that longevity is promoted by the age-dependent decrease in mitochondrial function that is observed in most species.