Machado Liana, Rafal Robert D
Psychology Department, University of Otago, PO Box 56, Dunedin, New Zealand.
Exp Brain Res. 2004 May;156(1):55-63. doi: 10.1007/s00221-003-1765-1. Epub 2003 Dec 18.
Fourteen patients with a chronic, unilateral lesion restricted to the frontal lobe (twelve involving the frontal eye field (FEF)), nine patients with a chronic, unilateral lesion restricted to posterior association cortex (eight involving the intraparietal sulcus (IPS)), and twelve neurologically normal control subjects were studied in an anti-saccade task. A combination of manipulating cuing and fixation offset enabled us to examine the effects of chronic oculomotor lesions on both saccade preparation and voluntary control over ocular fixation. Patients with lesions of the FEF made more errors (reflexive glances) toward contralesional targets, whereas patients with IPS lesions made fewer errors toward contralesional targets. Patients with IPS lesions had increased latencies to initiate saccades away from contralesional targets. For FEF patients, the presence of a fixation point inhibited the initiation of contralesionally directed saccades less than those directed ipsilesionally. Saccade preparation in response to a cue did not reduce the inhibitory effect of a fixation point on initiating anti-saccades directed either ipsilesionally or contralesionally for either patient group. We conclude that chronic IPS lesions result in a reduced contralesional visual grasp reflex (VGR) and delayed utilization of visual signals in the contralesional field for planning voluntary eye movements. In contrast, patients with chronic FEF lesions are impaired in inhibiting the VGR toward contralesional signals, and manifest an asymmetry in the balance between fixation and saccade activity. Moreover, voluntary control of fixation is compromised after chronic damage to either frontal or parietal oculomotor cortex.
在一项反扫视任务中，对14例患有局限于额叶的慢性单侧病变患者（其中12例累及额叶眼区（FEF））、9例患有局限于后联合皮质的慢性单侧病变患者（其中8例累及顶内沟（IPS））以及12名神经功能正常的对照受试者进行了研究。通过操纵提示和注视偏移的组合，我们能够研究慢性眼球运动病变对扫视准备和对眼球注视的自主控制的影响。FEF病变患者向对侧目标出现更多错误（反射性扫视），而IPS病变患者向对侧目标出现的错误较少。IPS病变患者从对侧目标发起扫视的潜伏期延长。对于FEF患者，固定点的存在对对侧方向扫视启动的抑制作用小于同侧方向扫视。对于两组患者，提示引发的扫视准备均未降低固定点对同侧或对侧方向发起反扫视的抑制作用。我们得出结论，慢性IPS病变导致对侧视觉抓取反射（VGR）减弱，以及在对侧视野中用于计划自主眼球运动的视觉信号利用延迟。相比之下，慢性FEF病变患者在抑制对对侧信号的VGR方面受损，并且在注视和扫视活动之间的平衡中表现出不对称性。此外，额叶或顶叶眼球运动皮质慢性损伤后，对注视的自主控制受到损害。
