The Brain and Mind Institute, London, Ontario, Canada;
J Neurophysiol. 2014 Jan;111(2):415-33. doi: 10.1152/jn.00398.2013. Epub 2013 Oct 23.
Inactivation permits direct assessment of the functional contribution of a given brain area to behavior. Previous inactivation studies of the frontal eye field (FEF) have either used large permanent ablations or reversible pharmacological techniques that only inactivate a small volume of tissue. Here we evaluated the impact of large, yet reversible, FEF inactivation on visually guided, delayed, and memory-guided saccades, using cryoloops implanted in the arcuate sulcus. While FEF inactivation produced the expected triad of contralateral saccadic deficits (increased reaction time, decreased accuracy and peak velocity) and performance errors (neglect or misdirected saccades), we also found consistent increases in reaction times of ipsiversive saccades in all three tasks. In addition, FEF inactivation did not increase the proportion of premature saccades to ipsilateral targets, as was predicted on the basis of pharmacological studies. Consistent with previous studies, greater deficits accompanied saccades toward extinguished visual cues. Our results attest to the functional contribution of the FEF to saccades in both directions. We speculate that the comparative effects of different inactivation techniques relate to the volume of inactivated tissue within the FEF. Larger inactivation volumes may reveal the functional contribution of more sparsely distributed neurons within the FEF, such as those related to ipsiversive saccades. Furthermore, while focal FEF inactivation may disinhibit the mirroring site in the other FEF, larger inactivation volumes may induce broad disinhibition in the other FEF that paradoxically prolongs oculomotor processing via increased competitive interactions.
失活允许直接评估特定脑区对行为的功能贡献。先前对额眼区（FEF）的失活研究要么使用了永久性大消融，要么使用了仅能使一小部分组织失活的可逆药理学技术。在这里，我们使用植入弓状沟的冷冻环评估了对视觉引导、延迟和记忆引导扫视的大但可逆的 FEF 失活的影响。虽然 FEF 失活产生了预期的三组对侧扫视缺陷（反应时间增加、准确性降低和峰值速度降低）和性能错误（忽视或扫视错误），但我们还发现所有三个任务中同侧扫视的反应时间都持续增加。此外，与基于药理学研究的预测相反，FEF 失活并没有增加对同侧目标的过早扫视的比例。与先前的研究一致，朝向熄灭的视觉线索的扫视伴随着更大的缺陷。我们的结果证明了 FEF 对两个方向扫视的功能贡献。我们推测，不同失活技术的比较效果与 FEF 内失活组织的体积有关。更大的失活体积可能会揭示 FEF 内分布更稀疏的神经元的功能贡献，例如与同侧扫视相关的神经元。此外，虽然焦点 FEF 失活可能会使对侧 FEF 中的镜像部位去抑制，但更大的失活体积可能会导致对侧 FEF 中的广泛去抑制，这通过增加竞争相互作用而延长眼球运动处理，从而产生矛盾的效果。
