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Background
It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current experiment, 4 T fMRI was employed to evaluate whether it is possible to detect white matter activation. We used an interhemispheric transfer task modelled after neurological studies of callosal disconnection. It was hypothesized that white matter activation could be detected using fMRI. 相似文献2.
Bellotti R Cafagna F Circella M De Cataldo G De Marzo CN Giglietto N Spinelli P Golden RL Stephens SA Stochaj SJ Webber WR De Pascale MP Morselli A Picozza P Ormes JF Streitmatter RE Massimo Brancaccio F Papini P Piccardi P Spillantini P Basini G Bongiorno F Ricci M Brunetti MT Codino A Grimani C Menichelli M Salvatori I 《Physical review D: Particles and fields》1996,53(1):35-43
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Electrode-supported hydrogels were conferred with the biospecificity of enzymes during the process of electropolymerization
to give rise to a class of bioactive, stimuli-responsive co-joined interpenetrating networks of inherently conductive polymers
and highly hydrated hydrogels. Glucose responsive biotransducers were prepared by potentiostatic electropolymerization [750 mV
vs. Ag/AgCl (3 M KCl)] of pyrrole at Poly(hydoxyethyl methacrylate)-based hydrogel-coated Pt micro-electrodes (Φ = 100 μm) from aqueous solutions of pyrrole and glucose oxidase (GOx; 0.4 M pyrrole, 1.0 mg/ml GOx) to 1.0 and 10.0 mC/cm2. Polypyrrole was them over-oxidized by cyclic voltammetry (0–1.2 V vs. Ag/AgCl, 40 cycles in PBKCl, pH = 7.0). Biotransducers
were stored at 4 °C in PBKCl for up to 18 days. Amperometric dose–response at 0.4 V vs. Ag/AgCl followed by Lineweaver–Burk
analysis produced enzyme kinetic parameters as a function of electropolymerization charge density and storage time. Apparent
Michaelis constant (K
Mapp) increased from 18.6–152.0 mM (1.0 mC/cm2) and from 2.7–6.1 mM (10.0 mC/cm2). Biotransducer sensitivity increased to 21.2 nA/mM after 18 days and to 12.8 pA/mM after 10 days for the 1.0 and 10.0 mC/cm2 membranes, respectively. Maximum current, I
max, also increased over time to 2.7 nA (1.0 mC/cm2) and to 170 pA (10.0 mC/cm2). Electropolymerization of polypyrrole is shown to be an effective means for imparting bioactivity to a hydrogel-coated microelectrode.
GOx was shown to be stabilized and to increase activity over time within the electroconductive hydrogel. 相似文献
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