Saccadic shortening and cerebral hemodynamics during neck flexion and vibrational stimulation on neck extensor muscles

抄録

  We investigated the effects of voluntary neck flexion (NF) and vibrational stimulation (VS) to the neck extensor muscles on saccadic reaction time (SRT) and the changes in cerebral oxygenated hemoglobin concentration (oxy-Hb). Oxy-Hb was measured from frontal area to observe attentional modulation, sensory-motor area for sensory-motor activity of neck extensor muscles, and occipital area for visual processing. Subjects were 13 young healthy adults, who performed reflexive-visually guided saccades for 2 min in three conditions; sitting in rest neck (RN) position, NF position, and VS to the neck extensor muscles. SRT was shorter in NF and VS than RN. In NF, SRT was the shortest for the first 10 s, and oxy-Hb showed the greatest initial increase in all areas, especially in occipital area by that time. After the initial increase, oxy-Hb decreased and from 1 min again started to gradually increase in all areas. Under VS, oxy-Hb showed a significant decrease in all areas, especially for the first 30 s, without initial increase. By the second minute oxy-Hb returned towards the base-line, with similar changing pattern as in NF, especially in the frontal area. These results could suggest that SRT shortening by NF and VS are regulated by different mechanisms.