Ioannides Andreas A, Fenwick Peter Bc, Pitri Elina, Liu Lichan
Laboratory for Human Brain Dynamics, AAI Scientific Cultural Services Ltd, Nicosia, Cyprus.
Nonlinear Biomed Phys. 2010 Jun 3;4 Suppl 1(Suppl 1):S11. doi: 10.1186/1753-4631-4-S1-S11.
Identifying eye movement related areas in the frontal lobe has a long history, with microstimulation in monkeys producing the most clear-cut results. For humans, however, there is still no consensus about the location and the extent of the frontal eye field (FEF). There is also no simple non-invasive method for unambiguously defining the FEF in individual subjects, a prerequisite for clinical applications. Here we explore the use of magnetoencephalography (MEG) for the non-invasive identification and characterization of FEF activity in an individual subject.
We mapped human brain activity before, during and after saccades by applying tomographic analysis to MEG data. Statistical parametric maps and circular statistics produced plausible FEF loci, but no unambiguous definition for individual subjects. Here we first computed the spectral decomposition and correlation with electrooculogram (EOG) of the tomographic brain activations. For each of these two measures statistical comparisons were made between different saccades.
In this paper, we first review the frontal cortex activations identified in earlier animal and human studies and place the putative human FEFs in a well-defined anatomical framework. This framework is then used as reference for describing the results of new Fourier analysis of the tomographic solutions comparing active saccade tasks and their controls. The most consistent change in the dorsal frontal cortex was at the putative left FEF, for both saccades to the left and right. The asymmetric result is consistent with the 1-way callosal traffic theory. We also showed that the new correlation analysis had its most consistent change in the contralateral putative FEF. This result was obtained for EOG latencies before saccade onset with delays of a few hundreds of milliseconds (FEF activity leading the EOG) and only for visual cues signaling the execution of a saccade in a previously defined saccade direction.
The FEF definition derived from microstimulation describes only one of the areas in the dorsal lateral frontal lobe that act together to plan, prepare and execute a saccade. The definition and characterization of these areas in an individual subject can be obtained from non-invasive MEG measurements.
确定额叶中与眼动相关的区域已有很长历史，对猴子进行微刺激产生了最明确的结果。然而，对于人类而言，关于额叶眼区（FEF）的位置和范围仍未达成共识。也没有简单的非侵入性方法来明确界定个体受试者的FEF，而这是临床应用的一个先决条件。在此，我们探索使用脑磁图（MEG）对个体受试者的FEF活动进行非侵入性识别和特征描述。
我们通过对MEG数据应用断层分析来绘制扫视前、扫视期间和扫视后的人脑活动图。统计参数图和圆形统计得出了看似合理的FEF位点，但没有针对个体受试者的明确界定。在此，我们首先计算断层脑激活的频谱分解以及与眼电图（EOG）的相关性。针对这两种测量方法，在不同扫视之间进行了统计比较。
在本文中，我们首先回顾了早期动物和人类研究中确定的额叶皮质激活情况，并将假定的人类FEF置于一个明确的解剖学框架中。然后，该框架被用作参考，以描述比较主动扫视任务及其对照的断层解的新傅里叶分析结果。背侧额叶皮质中最一致的变化发生在假定的左侧FEF，无论是向左还是向右的扫视。这种不对称结果与单向胼胝体交通理论一致。我们还表明，新的相关性分析在对侧假定的FEF中具有最一致的变化。该结果是在扫视开始前的EOG潜伏期延迟几百毫秒时（FEF活动领先于EOG）获得的，并且仅针对指示在先前定义的扫视方向上执行扫视的视觉线索。
从微刺激得出的FEF定义仅描述了背外侧额叶中共同作用以计划、准备和执行扫视的区域之一。这些区域在个体受试者中的定义和特征描述可通过非侵入性MEG测量获得。
