Taylor Paul C J, Rushworth Matthew F S, Nobre Anna C
Department of Experimental Psychology, University of Oxford, United Kingdom.
J Neurophysiol. 2008 Sep;100(3):1397-406. doi: 10.1152/jn.90241.2008. Epub 2008 Jul 2.
To investigate how we orient our spatial attention, previous studies have recorded neural activity while participants are instructed where to attend. Here we contrast this classical instructed attention condition with a novel condition in which the focus of voluntary attention is not specified by the experimenter but rather is freely chosen by the participant. Central cues prompted fixating participants either to choose which of two peripheral spatial locations to covertly attend or formed an instruction. Either type of cueing initiated selective attention demonstrated behaviorally by enhanced performance at a visual detection task in comparison to a separate divided attention condition. We used functional magnetic resonance imaging to measure which areas were more active during choice than instruction. Choosing where to attend activated a large cluster of medial frontal cortical regions similar to those that have been previously implicated in the free selection of overt action. We then addressed a potential confound in contrasting choice with instruction: participants may remember their behavior more when choosing. In a separate block, and interleaved with choice trials, "memory" trials were introduced in which participants were instructed to remember where they had attended on the previous trial. The presupplementary eye fields and lateral frontal eye fields were specialized for choice-guided attentional orienting over and above any memory confound. This evidence suggests a common mechanism may underlie free selection, whether for covert attention or overt saccades.
为了研究我们如何定向空间注意力，以往的研究在参与者被指示注意位置时记录神经活动。在这里，我们将这种经典的指示性注意力条件与一种新的条件进行对比，在新条件下，自愿注意力的焦点不是由实验者指定的，而是由参与者自由选择的。中央线索促使注视的参与者要么选择两个周边空间位置中的哪一个进行隐蔽注意，要么形成一个指示。与单独的分散注意力条件相比，这两种类型的线索提示都引发了选择性注意力，在视觉检测任务中表现增强即行为上得到证明。我们使用功能磁共振成像来测量在选择过程中哪些区域比指示过程中更活跃。选择注意位置激活了一大群内侧额叶皮质区域，类似于先前与明显动作的自由选择有关的区域。然后，我们解决了在将选择与指示进行对比时的一个潜在混淆因素：参与者在选择时可能会更清楚地记住自己的行为。在一个单独的组块中，并与选择试验交错进行，引入了“记忆”试验，其中指示参与者记住他们在前一次试验中注意的位置。补充眼区和外侧额叶眼区专门用于在任何记忆混淆之上的选择引导的注意力定向。这一证据表明，无论是隐蔽注意力还是明显扫视，自由选择可能都有一个共同的机制。
