Sommer M A, Tehovnik E J
Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139, USA.
Exp Brain Res. 1999 Feb;124(4):429-46. doi: 10.1007/s002210050639.
Neural recording and electrical stimulation results suggest that the dorsomedial frontal cortex (DMFC) of macaque is involved in oculomotor behavior. We reversibly inactivated the DMFC using lidocaine and examined how saccadic eye movements and fixations were affected. The inactivation methods and monkeys were the same as those used in a previous study of the frontal eye field (FEF), another frontal oculomotor region. In the first stage of the present study, monkeys performed tasks that required the generation of single saccades and fixations. During 15 DMFC inactivations, we found only mild, infrequent deficits. This contrasts with our prior finding that FEF inactivation causes severe, reliable deficits in performance of these tasks. In the second stage of the study, we investigated whether DMFC inactivation affected behavior when a monkey was required to make more than one saccade and fixation. We used a double-step task: two targets were flashed in rapid succession and the monkey had to make two saccades to foveate the target locations. In each of five experiments, DMFC inactivation caused a moderate, significant deficit. Both ipsi- and contraversive saccades were disrupted. In two experiments, the first saccades were made to the wrong place and had increased latencies. In one experiment, first saccades were unaffected, but second saccades were made to the wrong place and had increased latencies. In the remaining two experiments, specific reasons for the deficit were not detected. Saline infusions into DMFC had no effect. Inactivation of FEF caused a larger double-step deficit than did inactivation of DMFC. The FEF inactivation impaired contraversive first or second saccades of the sequence. In conclusion, our results suggest that the DMFC makes an important contribution to generating sequential saccades and fixations but not single saccades and fixations. Compared with the FEF, the DMFC has a weaker, less directional, more task-dependent oculomotor influence.
神经记录和电刺激结果表明，猕猴的背内侧前额叶皮质（DMFC）参与眼动行为。我们使用利多卡因可逆性地使DMFC失活，并研究扫视眼动和注视是如何受到影响的。失活方法和猴子与先前对另一个额叶眼动区域——额叶眼区（FEF）的研究中所使用的相同。在本研究的第一阶段，猴子执行需要产生单个扫视和注视的任务。在15次DMFC失活过程中，我们仅发现了轻微、不常见的缺陷。这与我们之前的发现形成对比，即FEF失活会导致这些任务的执行出现严重、可靠的缺陷。在研究的第二阶段，我们调查了当要求猴子进行不止一次扫视和注视时，DMFC失活是否会影响行为。我们使用了一个双步任务：两个目标快速连续闪烁，猴子必须进行两次扫视以注视目标位置。在五个实验中的每一个实验中，DMFC失活都导致了中度、显著的缺陷。同侧和对侧扫视均受到干扰。在两个实验中，首次扫视到了错误的位置且潜伏期延长。在一个实验中，首次扫视未受影响，但第二次扫视到了错误的位置且潜伏期延长。在其余两个实验中，未检测到缺陷的具体原因。向DMFC注入生理盐水没有效果。与DMFC失活相比，FEF失活导致的双步缺陷更大。FEF失活损害了序列中对侧的首次或第二次扫视。总之，我们的结果表明，DMFC对产生连续的扫视和注视有重要贡献，但对单个扫视和注视没有贡献。与FEF相比，DMFC对眼动的影响较弱、方向性较小且更依赖任务。
