tailieunhanh - Neuro-Ophthalmology - part 7

Eye dấu vết chuyển động cho đối tượng bình thường được liên kết với các đối saccade bắt đầu. Ngang (a-c) và dọc (d-f) saccades được hiển thị một cách riêng biệt như vị trí mắt (a, d,), vận tốc mắt (b, e), và vị trí nắp (c, f). Saccade thời gian được tăng lên, cao điểm vận tốc giảm cho cả hai chiều ngang (a, b,) và theo chiều dọc | Fig. 2. Eye movement traces for one normal subject are aligned with resped to saccade begin. Horizontal a-c and vertical d-f saccades are displayed separately as eye position a d eye velocity b e and lid position c f . Saccade duration is increased and peak velocity decreased for both horizontal a b and vertical d e saccades in the blink condition solid line in contrast to the control condition dotted line . The shift of the dotted lines f indicates the accompanying lid movement with vertical eye movements modified after Rambold et al. 42 with permission. 73-75 . Ibotenic acid injections in the OPN region of the monkey decrease saccadic peak velocity and increase saccade duration without changing saccade amplitude 76 . Blinks decrease OPN discharge even without eye movements 77-79 the discharge during saccades in medium-lead burst neurons of the PPRF 80 and in saccade-related long-lead burst neurons in the intermediate layer of the SC is decreased 29 . Accordingly the inhibitory effect of blinks on the OPNs might Helmchen Rambold 116 Fig. 3. The vergence eye movements are shown separately for the convergence a b and divergence c d components of the vergence position a c and the relative lid position b d . Eye movements during the blink condition black solid traces are compared with those during the no blink condition dotted trace . All traces are aligned to vergence onset. For better illustration the onset of two phases of the vergence components is indicated by vertical dotted lines. In phase 1 a convergence-divergence movement is found in the convergence a and in the divergence c paradigms. Note that vergence duration exceeds blink duration modified after Rambold et al. 2002 42 with permission. explain the outlined behavioral effects. Further evidence comes from a saccadic brainstem model that incorporates rebound inhibition firing of the medium-lead burst neurons 81 . Blinks and Vergence Eye Movements Vergence may be divided into two subsystems a transient and a