The role of transcranial magnetic stimulation in understanding attention-related networks in single subjects.

Attention is a cognitive mechanism that has been studied through several methodological viewpoints, including animal models, MRI in stroke patients, and fMRI in healthy subjects. Activation-based fMRI research has also pointed to specific networks that activate during attention tasks. Most recently, network neuroscience has been used to study the functional connectivity of large-scale networks for attention to reveal how strongly correlated networks are to each other when engaged in specific behaviors. While neuroimaging has revealed important information about the neural correlates of attention, it is crucial to better understand how these processes are organized and executed in the brain in single subjects to guide theories and treatments for attention. Noninvasive brain stimulation is an effective tool to causally manipulate neural activity to detect the causal roles of circuits in behavior. We describe how combining transcranial magnetic stimulation (TMS) with modern precision network analysis in single-subject neuroimaging could test the roles of regions, circuits, and networks in regulating attention as a pathway to improve treatment effect magnitudes and specificity.

Seasonal variations in plasma phosphorus levels of transhumant sheep in Kordofan, Sudan.

Plasma phosphorus levels were evaluated for one hundred adult breeding ewes from transhumant producer flocks during the late rainy season (September 1984/1985), the mid-dry season (February 1985) and the late-dry season (May 1985). The percentage of non-pregnant/non-lactating ewes critically deficient in phosphorus increased from 9% in the rainy season to 56% in the late-dry season. In September 35% of pregnant ewes were critically deficient in phosphorus. During peak lactation (February) 87% of lactating ewes were critically deficient in phosphorus and 84% remained critically deficient until the start of the rainy season approximately 20 weeks postlambing. The low phosphorus content of grazing rations, which varied from 0.18% in the rainy season to 0.09% in the dry season, and low forage availability, which was especially acute during the late-dry season, appeared to be the most important factors limiting phosphorus intake.

Twins with Alzheimer's disease.

Twins of identical appearance were both affected by Alzheimer's senile dementia. In one, dementia began in her late 60s. She died at age 74. In the other, onset was at age 83. She died of ovarian carcinoma at age 85. The histopathologic findings of Alzheimer's disease were confirmed in both twin sisters.

Studies in aging of the brain: IV. Familial Alzheimer disease: Relation to transmissible dementia, aneuploidy, and microtubular defects.

Alzheimer disease was transmitted in a pattern consistent with an autosomal dominant trait in three families. This brings to 50 the number of such families reported. In one of our families, one patient had histologically confirmed Alzheimer disease, whereas her sister had proved spongiform encephalopathy. Other data suggest a link between familial Alzheimer disease and transmissible dementia. Alzheimer disease is associated with abnormal neurofibrillary structures, Down syndrome, and abnormal numbers of chromosomes in lymphocytes (aneuploidy). These observations are consistent with a disorder in the physiology of tubular-filamentous structures involving different cell types.

Increased aneuploidy in Alzheimer disease.

The purpose of this study was to determine if cytogenetic changes are present in Alzheimer disease, one of the presenile dementias. The chromosomes of three groups of people were studied: 1) sporadic cases of Alzheimer disease (eight cases), 2) familial cases of Alzheimer disease with affected individuals in at least two generations of their families (five cases), and 3) currently unaffected siblings of the affected individuals in these families (nine cases). One hundred cells per individual were examined using GTG banding to allow chromosome identification. A statistically significant increase in aneuploidy was found in five of eight patients in group 1 (P less than 0.05) and in each of five patients in group 2 (P less than 0.001) when compared with the rate of aneuploidy in age- and sex-matched controls. In addition, two individuals in group 3 exhibited a significant increase in aneuploidy over the control group, raising the possibility that finding increased aneuploidy may allow one to anticipate the clinical expression of the disease state.

Precautions in familial transmissible dementia: including familial Alzheimer's disease.

Recent studies suggest that some cases of familial Alzheimer's disease may be associated with a transmissible dementia. Animal experiments show that presymptomatic carriers of "slow virus" agents can transmit disease. Because of these findings, we have extended the precautions previously delineated to include those at risk of acquiring transmissible dementia, specifically, to the descendants of those affected with familial Alzheimer's disease or familial Creutzfeldt-Jakob's disease. Blood donation from such persons may pose a danger, because transmissible spongioform encephalopathy has been passed from animal to animal by blood serum and by the WBC layer of frozen whole blood.