Backgrounds: The digit symbol substitution test (DSST) is a clinically useful and widely accepted tool for the detection of various psychiatric disorders. Investigating neural activity during the DSST is useful when considering the relationship between the poor performance on the DSST and neurocognitive deficits. However, obtaining reliable functional imaging of the neural mechanisms associated with this test is challenging due to motion artifacts. Aims: To circumvent this problem, we examined frontal lobe activity during the DSST using multichannel near-infrared spectroscopy, a noninvasive functional imaging technique that does not interfere with the DSST procedure. Methods: Twenty-five healthy volunteers were enrolled in this study. Changes in the concentration of oxygenated hemoglobin (oxyHb) during the DSST were determined bilaterally in 52 measurement points (channels) on the frontal area. Results: We found significant increases in oxyHb in more than 70% of the channels, with the intensity of the increase being more pronounced in the left hemisphere. Several channels showed significant positive correlations between changes in oxyHb and DSST performance. Some of the channels with a significant increase in oxyHb during the DSST did not show a correlation with the DSST performance. Conclusions: Our findings indicate that the DSST could prove useful as a frontal lobe stimulating task. Further examinations of DSST/near-infrared spectroscopy analyses of neural mechanisms in patients with psychiatric and neurological diseases are necessary to assess its effectiveness in clinical practice for the evaluation of neuropsychopathology.

The present research investigated activities in the prefrontal cortex while performing the Rorschach inkblot method (RIM) using functional near-infrared spectroscopy. Participants who had no history of mental illness or external head injury were presented with three International RIM Cards (I, IV, V) for 30 s each and asked to identify what they looked like. In addition, a picture task was conducted, in which simple pictures were used as visual stimuli and participants were asked to say what they were. Results showed significant increase of oxyhemoglobin over time with nearly all measurement channels on the RIM task. The volume changes in oxyhemoglobin during both the middle and late segments of the RIM task were more significant than those of the picture task in almost all channels with the exception of no significant difference in the middle with a few right lateral channels. With regard to deoxyhemoglobin, on the RIM task, a significant decrease was observed with nearly all channels, but only in some of the task segments. These results are then discussed in regards to the function of the prefrontal cortex.Key words: Rorschach inkblot method, prefrontal cortex, functional near-infrared spectroscopy, projective method, functional imaging technique for brain activity.

In this paper, the stress intensity factors (SIFs) of two edge cracks which emanate asymmetrically from a center U-shaped notch in a finite plate under tension were computed by the body force method. The crack which is governed by the elastic notch stress field was treated as a short crack; the crack which is not almost influenced by the notch stress field was treated as a long crack. The cracks were divided into the short and long ones, and the SIFs were each investigated with respect to tendency. Then, it was found that the SIFs become nearly equal when both cracks are larger than 0.5ρ and smaller than (0.5W − t) even if the cracks are asymmetric, where ρ is a notch root radius, t is a notch depth and W is a half plate width. Moreover, the approximate calculations of the SIFs were performed by using the simple formulae for evaluating the SIFs of the eccentric crack in the finite plate and the short symmetric edge cracks emanating from the elliptical hole in the infinite plate. Then, the accuracy of the approximate calculations was examined by comparing with the solutions by the body force method.

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