words)Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that is widely used to stimulate the sensorimotor cortex, and yet the mechanism by which it influences the natural activity of cortical networks is still under debate. Here, we characterize the effects of anodal and cathodal tDCS on underlying neurons in active macaque sensorimotor cortex across a range of doses. We find changes in spike rates that are sensitive to both current intensity and polarity, behavioral state, and that are cell-type specific. At high currents, effects persist after the offset of stimulation, and the spatiotemporal activity associated with motor activity of the contralateral limb, measured by dynamics of neural ensembles, are altered. These data suggest that tDCS induces reproducible and noticeable changes in cortical neuron activity and support the theory that it affects brain activity through a combination of single neuron polarization and network interactions.
In connection with studies on benzanthrone (I) which are being pursued in this department both as crystal-(I) (II) structure and as molecular-orbital investigations, the cell dimensions and space groups of the 3-chloro-and 3-bromo-derivat£ves were determined in the hope of finding morphological relationships to the parent compound as well as of being able to use the heavy-atom .technique of structure analysis. Such relationships were not, however, recognized and as further study of the derivatives has had to be postponed it seems worth while to publish for these two compounds the crystallographic and optical results at present available; corresponding measurements on the parent compound are added for comparison. Similar information on l'-keto-9:10-cyclopenteno-1 : 2: 3: 4: 5: 6: 7: 8-octahyclrophenanthrene (II) has been in~lnrlAd_ The crystals, which were most successfully grown from solution in nitrobenzene, are rather hard for a compound having no obvious hydrogen or ionic bonds. They form yellowish needles elongated parallel to c, bounded by a{100} and r{120} and terminated by c{001} though often fractured.Refractive indices: 1.62 ~ c~ < 1-74 parallel to a, fl --1.79 parallel to c, 7 ~ 1.9 (estimated) parallel to b. 3-Chlorobenzanthrone, CITHgOCIMol.wt. =-264.54; m.p. = 182 ° C.; dcalc.= 1.46, dobs.= 1.49 g.cm. -a. Monoclinic, class 2/m: a = 14.40±0.02, b = 11.56±0.01, c = 7.27±0.01 A.; fl-93 ° 37'. Volume of unit cell = 1205 /~a. Absent spectra: {hkl} no general halvings; {h0l} absent when h+l odd, {0b0} absent when b odd. Space group P21/n uniquely determined. Molecules per unit cell: 4; molecular symmetry: none. Electrons per unit cell: F(000) = 544. Absorption coefficient for Cu K~ radiation -----27.5 cm. -1.The crystals were yellow laths tabular on a{100} and elongated parallel to c[001] with m{ll0} as prism faces. The best specimens were recrystallized from glacial acetic acid or nitrobenzene but there is a marked tendency to form twins.It was impossible to make a complete optical characterization of the crystals but the refractive index for vibrations parallel to c is 1.51 and that for vibrations parallel to b is approximately 1.8. 3-Bromobenzanthrone, C17HgOBrMol.wt. = 309.00; m.p. = 170 ° C.; dc~c. = 1.696, dobs.= 1.695 g.cm. {hid} absent when h-~l¢÷l odd, {h0l} absent when h or l odd, {0/c0} absent when k odd. Space group I2/a or Ic; since the latter requires only four asymmetric units per cell while the former requires eight (the number actually observed), I2/a seems the more likely. The colourless crystals are usually long needles of almost square section bounded by b{010} and c{001} and terminated by a{100}. Plates elongated parallel to a [100] are, however, alBo formed and Bhow marked ~leavage parallel to b{010}, thus breaking down into the acicular crystals.
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