The neural basis of visual-spatial attention: A combined TMS/ERP investigation

在任何清醒的时刻，我们的感觉器官都会接收到大量关于外部事件的信息。然而，人类的大脑只处理这些信息的一小部分，使其成为有意识的意识。我们经常用“注意力”来描述这种感觉信息的选择。我们意识到我们决定关注的那些刺激，但当我们的注意力被转移到其他地方时，就不会注意到其他刺激。大脑是如何选择和处理那些我们决定关注的刺激，以及其他目前未被关注的信息的命运是什么？最近的神经科学研究发现，当观察者将注意力引导到感觉环境的特定区域时，大脑的额叶和顶叶区域就会被激活。有人认为，这些大脑区域在信息选择中起着重要作用。我们现在也知道，注意力的转移会导致大脑中分析视觉信息部分的活动发生变化。我们不知道的是这些注意力的不同方面是如何联系在一起的。人们通常认为，大脑额叶和顶叶区域的活动代表？注意力控制信号？这告诉视觉大脑区域哪些刺激是当前相关的，这样这些刺激就可以被优先处理。我们将通过在观察者执行注意力任务时对额叶和顶叶的注意力控制区域应用经颅磁刺激（TMS）来研究这一点，同时记录大脑其他部分（如视觉皮层）的脑电图活动。经颅磁刺激通过产生一个？虚拟病变?。我们想知道这是怎么回事？虚拟病变?当经颅磁刺激应用于注意力控制区域时，会损害大脑选择和处理视觉事件的能力。我们期望发现，经颅磁刺激会破坏对特定视觉刺激的关注能力，从而导致脑电图对这些刺激的不同反应模式。这种经颅磁刺激引起的注意力中断可能类似于在许多中风后神经系统患者中观察到的注意力缺陷。这些注意力缺陷通常是非常致残的，但很难恢复。我们希望我们的研究将有助于为这些患者受影响的大脑机制提供新的见解，以便将来开发新的干预措施。

At any waking moment, our sensory organs receive a large amount of information about external events. However, the human brain only processes a small fraction of this information to a stage where it becomes accessible to conscious awareness. We often describe this selection of sensory information by referring to ?attention?: We are aware of those stimuli that we decide to attend to, but fail to notice other stimuli when our attention is directed elsewhere. How does the brain select and process those stimuli that we decide to attend to, and what is the fate of other, currently unattended information? Recent neuroscientific research has uncovered brain regions in the frontal and parietal lobes that are activated when observers direct their attention to specific regions of their sensory environment. It has been suggested that these brain regions play an important part in the selection of information. We now also know that shifts of attention result in activity changes in parts of the brain that analyse visual information. What we do not know is how these different aspects of attention are related. It is often assumed that activity in frontal and parietal brain regions represents ?attentional control signals? that inform visual brain regions which stimuli are currently relevant, so that these stimuli can be preferentially processed. We will investigate this by applying transcranial magnetic stimulation (TMS) to attentional control areas in the frontal and parietal lobe while observers are performing an attentional task, and simultaneously record EEG activity from other parts of the brain (such as the visual cortex). TMS briefly disrupts the operation of specific brain areas by creating a ?virtual lesion?. We want to find out how such ?virtual lesions? induced when TMS is applied to attentional control regions can impair the ability of the brain to select and process visual events. We expect to find that TMS disrupts the ability to attend to specific visual stimuli, and that this leads to different patterns of EEG responses to these stimuli. Such disruptions of attention by TMS may be similar to the attentional deficits that are observed in many neurological patients after stroke. These attentional impairments are often very disabling, but are hard to rehabilitate. We hope that our research will help to provide new insights into the brain mechanisms that are affected in these patients, so that new interventions may be developed in the future.