Decoupling the cortical power spectrum reveals real-time representation of individual finger movements in humans.

During active movement the electric potentials measured from the surface of the motor cortex exhibit consistent modulation, revealing two distinguishable processes in the power spectrum. At frequencies <40 Hz, narrow-band power decreases occur with movement over widely distributed cortical areas, while at higher frequencies there are spatially more focal power increases. These high-frequency changes have commonly been assumed to reflect synchronous rhythms, analogous to lower-frequency phenomena, but it has recently been proposed that they reflect a broad-band spectral change across the entire spectrum, which could be obscured by synchronous rhythms at low frequencies. In 10 human subjects performing a finger movement task, we demonstrate that a principal component type of decomposition can naively separate low-frequency narrow-band rhythms from an asynchronous, broad-spectral, change at all frequencies between 5 and 200 Hz. This broad-spectral change exhibited spatially discrete representation for individual fingers and reproduced the temporal movement trajectories of different individual fingers.

Parathyroid hormone levels, calcium-channel blockers, and the dyslipidemia of nondiabetic hemodialysis patients.

BACKGROUND: Experimental studies have shown that increased levels of parathyroid hormone (PTH) in uremia may cause elevation of intracellular calcium, predisposing to insulin resistance and lipid metabolism abnormalities. Administration of calcium-channel blockers (CCBs) in these models protects against the development of lipid profile abnormalities. This study evaluates the combined effect of intact PTH (iPTH) levels and administration of CCB on the lipid profiles of nondiabetic hemodialysis patients. METHODS: One hundred and eight non-diabetic hemodialysis patients were studied for 6 months. The population was divided into four groups, according to iPTH levels and administration of CCB: (A) iPTH<70 pg/mL, administration of CCB (n=16), (B) iPTH>300 pg/mL without administration of CCB (n=43), (C) iPTH<70 pg/mL without CCB administration (n=19), and (D) iPTH>300 pg/mL with CCB administration (n=30). Serum concentrations of total cholesterol, high-density lipoprotein (HDL), triglycerides, and albumin were measured on a monthly basis. RESULTS: All results are shown as mean SE. Total cholesterol values (in mg/ dL) were for group (A) 186 +/- 4, for group (B) 205 +/- 3, for group (C) 200 +/- 3, and for group (D) 203 +/- 4 [p NS between (C) and (D), p<.05 for all other comparisons]. Triglycerides values (in mg/dL) were for group (A) 171 +/- 9, for group (B) 199 +/- 6, for group (C) 190 +/- 6, and for group (D) 191 +/- 9 (p NS for all comparisons). HDL values (in mg/dL) were for group (A) 43.8 +/- 1, for group (B) 35.8 +/- 1, for group (C) 38.3 +/- 0.7, and for group (D) 37.2 +/- 0.7 mg/dL [p NS between (C) and (D), p<.001 for all other comparisons]. Low-density lipoprotein values (in mg/dL) were for group (A) 107.6 +/- 4.4, for group (B) 149.3 +/- 2.5, for group (C) 131.2 +/- 2.9, and for group (D) 126.8 +/- 4.1 [p NS between (C) and (D), p<.001 for all other comparisons]. Atherogenic index values, calculated as [triglycerides/HDL] ratio, were for group (A) 4.6 +/- 0.04 , for group (B) 6.2 +/- 0.04, for group (C) 4.9 +/- 0.03, and for group (D) 5.9 +/- 0.03 [p NS between (C) and (D), p<.004 for all other comparisons]. CONCLUSION: In nondiabetic hemodialysis patients, lipid profile abnormalities often accompany high levels of iPTH. The decrease in iPTH and/or the administration of CCB are accompanied by significant improvements in the main lipid profiles, including the atherogenic index.