Changes in cognitive characteristics according to 3 intensity changes by 8 vibration frequencies (STROBE)

In this study, we attempted to observe changes in cognitive characteristics according to 3 intensity changes (Level 1: 0.25 gravity, Level 2: 0.38 gravity, Level 3: 1.3 gravity) at 8 vibration frequencies (10, 50, 100, 150, 200, 225, 250, 300 Hz). The subjects were twelve male (22.1 ± 0.6 years old) and twelve female (21.5 ± 0.8 years old) healthy, right-handed adults with normal cognitive abilities. An experimental trial consisted of a stimulation phase (0.1 sec) in which a vibration stimulus was presented and a rest phase (6 sec) in which no vibration stimulus was presented. A selected stimulus was presented on the first knuckle of the right index finger 5 times (trials). Cognitive characteristics scores according to changes in intensity at each frequency were sampled using a subjective assessment sheet consisting of eighteen items (“ticklish,” “shivery,” “push,” “convex,” “thick,” “numb,” “slow,” “fast,” “shallow,” “strike,” “weak,” “strong,” “dense,” “blunt,” “heavy,” “light,” “stab”, “no stimulus”). To identify the cognitive characteristics according to intensity changes by frequency, the 3 intensities were designated as variables, and a curve estimation regression analysis was performed. At 10 Hz, cognitive characteristics of ’blunt’ increased with the intensity, and ’weak’ decreased. In 100 and 225 Hz, increase or decrease in intensity led to opposite cognitive characteristics (‘weak-strong’ in 100 and 225 Hz, ‘light-heavy’ in 225 Hz). In 100 and 225 Hz, as the intensity increased, expressions on the sense of surface such as ’blunt’ were superior, and the shape of an object (thick) and dynamics (push) differed with the change in intensity. In addition, in 225 Hz, decrease in intensity led to increase in cognitive characteristics such as ’light’ and 'shallow. ’Fast’ was unique in that it only appeared as the intensity increased at 300 Hz.