Study on the role of common weeds in survival of Verticillium dahliae the causal agent of cotton wilt disease.

This study was carried out to investigate the roles of common weeds in the survival of Verticillium dahliae and the incidence of cotton wilt disease in Moghan and Neishabour area of Iran during 2003-2005 cropping seasons. The design of the experiment was Randomized Complete Blocks (RCB) with ten treatments (No. of weeds) and four replications (No. of cotton fields). Populations of V. dahliae in the roots of weeds and their surrounding soil was determined every year and were compared in different treatments. The cotton wilt disease index was also evaluated in different fields in each experimental site. Results indicated that the fungal population was variable depending on weed species, experimental site and the year of study. In general, Pigweed (Amaranthus retroflexus), Nightshde (Solanum nigrum), Spiny cockleburr (Xanthium spinosum) and common purslane (Portulaca oleraceea) showed the highest fungal populations in their roots and surrounding soil. Disease index in Moghan cotton fields in different years varied and were higher than Neishabour fields.

Organization of receptive language-specific cortex before and after left temporal lobectomy.

OBJECTIVE: To examine brain activation associated with receptive language in patients with left temporal lobe epilepsy (TLE) before and after an anterior temporal lobectomy using magnetoencephalography (MEG), and to evaluate which patients were most likely to show a change in the lateralization and localization of the mechanisms supporting receptive language and if such changes were associated with neuropsychological function. METHODS: Twelve patients with left TLE underwent preoperative Wada testing, and pre- and postoperative neuropsychological testing and MEG language mapping. The anatomic location of receptive language-related activity sources observed with MEG was determined by coregistering MEG data with structural MRI scans. Language laterality indices were calculated based on the number of reproducible activity sources in each hemisphere. The proximity of language-specific activity sources to Wernicke's area was also examined. RESULTS: Although the small sample size precluded formal statistical analyses, patients with atypical (bilateral) hemispheric dominance preoperatively were more likely than patients with typical (left-hemisphere) dominance to show evidence of increased right hemisphere participation in language functions after surgery. Patients with left hemispheric dominance preoperatively were more likely to show intrahemispheric changes involving a slight inferior shift of the putative location of Wernicke's area. Patients with bilateral representation tended to perform worse on neuropsychological test measures obtained both pre- and postoperatively. CONCLUSION: Interhemispheric functional reorganization of language-specific areas may occur in patients undergoing left anterior temporal lobectomy. Intrahemispheric reorganization may take place even when the resection does not directly impinge upon Wernicke's area.

Spatio-temporal cortical dynamics of phonemic and semantic fluency.

Hemodynamic brain imaging and lesion studies have suggested differential involvement of expressive language-related cortical regions based on the phonemic versus semantic characteristics of verbal cues. The aims of this study were: 1) to elucidate the relative timing of the activity of inferior frontal and anterior insular versus motor and supplementary motor cortex during a fluency task and 2) to assess potential differences in the location or timing of activity in anterior and posterior language areas based on letter versus category cues. Using magnetic source imaging (MSI), we found significantly earlier onset latencies and a greater number of activity sources in motor and supplementary motor compared with inferior frontal and anterior insular regions. We also observed greater left versus right hemispheric asymmetry of activation for letter compared with category cues. This study provides new insights into cortico-cortical interactions during expressive language tasks.

Reorganization of language-specific cortex in patients with lesions or mesial temporal epilepsy.

OBJECTIVE: To examine brain activation profiles for receptive language function, using magnetoencephalography (MEG), in patients with left hemisphere space-occupying lesions and patients with left temporal lobe epilepsy due to mesial temporal sclerosis (MTS) and to evaluate whether cross- and intrahemispheric plasticity for language varied as a function of lesion type or location. METHODS: Twenty-one patients with MTS and 23 lesional patients underwent preoperative language mapping while performing a word recognition task. The anatomic location of late activity sources was determined by co-registering MEG coordinates onto structural MRI scans. A language laterality index was calculated based on the number of activity sources in each hemisphere. The location of language-specific activity was examined in relation to its proximity or overlap with Wernicke's area. RESULTS: A higher incidence of atypical language lateralization was noted among patients with MTS than lesional patients (43 vs 13%). The majority of MTS patients with early seizure onset (before age 5) showed atypical language lateralization. In contrast, the precise location of receptive language-specific cortex within the dominant hemisphere was found to be atypical (outside of Wernicke's area) in 30% of lesional patients and only 14% of MTS patients. CONCLUSIONS: There is an increased probability of a partial or total displacement of key components of the brain mechanism responsible for receptive language function to the nondominant hemisphere in mesial temporal sclerosis patients. Early onset of seizures is strongly associated with atypical language lateralization. Lesions in the dominant hemisphere tend to result in an intrahemispheric reorganization of linguistic function.

Spatio-temporal brain activation profiles associated with line bisection judgments and double simultaneous visual stimulation.

We used magnetic source imaging (MSI) to investigate the spatio-temporal patterns of brain activity associated with line bisection judgments and double simultaneous visual stimulation in 14 healthy adults. Consistent with lesion and hemodynamic neuroimaging studies, we found the greatest number of activity sources in right inferior parietal cortex. These sources were most prominent, on average, between 200 and 300 ms after the onset of single (left, right, or center) target stimuli. A greater number of significant activity sources were found in right inferior parietal, occipital, and prefrontal cortices during bilateral compared with unilateral stimulus presentation. Based on these observations, we suggest that a more parsimonious physiological explanation of visual extinction than the hemispheric rivalry account may be the additional neuronal excitation required in right occipital and parietal cortices for accurate bilateral visual perception.

Does magnetoencephalography add to scalp video-EEG as a diagnostic tool in epilepsy surgery?

OBJECTIVE: The authors evaluated the sensitivity and selectivity of interictal magnetoencephalography (MEG) versus prolonged ictal and interictal scalp video-electroencephalography (V-EEG) in order to identify patient groups that would benefit from preoperative MEG testing. METHODS: The authors evaluated 113 consecutive patients with medically refractory epilepsy who underwent surgery. The epileptogenic region predicted by interictal and ictal V-EEG and MEG was defined in relation to the resected area as perfectly overlapping with the resected area, partially overlapping, or nonoverlapping. RESULTS: The sensitivity of a 30-minute interictal MEG study for detecting clinically significant epileptiform activity was 79.2%. Using MEG, we were able to localize the resected region in a greater proportion of patients (72.3%) than with noninvasive V-EEG (40%). MEG contributed to the localization of the resected region in 58.8% of the patients with a nonlocalizing V-EEG study and 72.8% of the patients for whom V-EEG only partially identified the resected zone. Overall, MEG and V-EEG results were equivalent in 32.3% of the cases, and additional localization information was obtained using MEG in 40% of the patients. CONCLUSION: MEG is most useful for presurgical planning in patients who have either partially or nonlocalizing V-EEG results.