Guo Zhouyi

Dissociated brain organization for two-digit addition and subtraction: An fMRI investigation

The present study compared the patterns of brain activation elicited by two-digit addition and subtraction problems. Thirty-two Chinese undergraduates of the same educational background and of similar age were asked to assess whether arithmetic operations were true or false during functional magnetic resonance imaging. Results showed that both complex addition and subtraction were supported by the broad neural system that involved regions within the inferior parietal lobule, the precuneus, and the inferior occipital gyrus, as well as some subcortical structures. Nevertheless, complex problems involving addition elicited more activation mainly in the bilateral medial frontal gyrus, whereas problems involving subtraction had more activation in the precentral gyrus and the thalamus in the right hemisphere, as well as the inferior parietal lobule in the left hemisphere. This pattern of dissociated activation suggests that partially separate neuronal networks might support these different operations. It also suggests that complex addition has a greater reliance on the fronto-parietal cortical circuit and subtraction on the parieto-subcortical circuit.

Second-harmonic generation as a DNA malignancy indicator of prostate glandular epithelial cells

This paper first demonstrates second-harmonic generation (SHG) in the intact cell nucleus, which acts as an optical indicator of DNA malignancy in prostate glandular epithelial cells. Within a scanning region of 2.7 μm×2.7 μm in cell nuclei, SHG signals produced from benign prostatic hyperplasia (BPH) and prostate carcinoma (PC) tissues (mouse model C57BL/6) have been investigated. Statistical analyses (t test) of a total of 405 measurements (204 nuclei from BPH and 201 nuclei from PC) show that SHG signals from BPH and PC have a distinct difference (p < 0.05), suggesting a potential optical method of revealing very early malignancy in prostate glandular epithelial cells based upon induced biochemical and/or biophysical modifications in DNA.

Effect of Distribution Pattern of Molecular Dipoles on Microscopic Second-Harmonic Generation

We set up a model for dealing with the second-harmonic generation (SHG) from molecular dipoles in a line alignment pattern rather than a planar distribution under a microscope. Because of this model, it is possible to perform a flexibly quantitative investigation of SHG from collagen fibres at a molecular level. The line alignment pattern induces more significant modifications in both the angular dipole distribution structure A(θ,) and the second-harmonic power structure Θy(θ,), compared to a planar distribution. Also, the line alignment angle t has strong effect on A(θ,) and Θy(θ,), resulting in an irregular SHG angular power distribution. That is to say, it is unnecessary for SHG emission to present two well-defined off-axis lobes. The total SHG power shows two symmetrical peaks at angles of t = 50° and t = 130° while a drop at t = 90°. The weakest SHG signals can be measured at t = 0° and t = 180°.