Time-series variations in cerebral blood flow. * P < 0.05 by Student’s t test compared with pre-stimulus (average for 30 s) ◇ P < 0.01 by Student’s t test compared with pre-stimulus (average for 30 s). CBF rose significantly immediately after touching the metal (a, b). Significant decreases in CBF were continuously seen between 10 s and 80 s with the fabric (c, d). For the natural pothos stimulus, there was a slight but significant reduction in CBF in the first half of the stimulus for the right frontal lobe and in the latter half of the stimulus (e, f) for the left frontal lobe. However, there was no significant difference in the stimulus of artificial pothos (g, h).