动态构形:关于时间进程和处理序列的脑磁图证据
Form-from-motion: MEG evidence for time course and processing sequence.
作者信息
Schoenfeld M A, Woldorff M, Düzel E, Scheich H, Heinze H-J, Mangun G R
机构信息
Otto von Guericke University, Magdeburg, Germany.
出版信息
J Cogn Neurosci. 2003 Feb 15;15(2):157-72. doi: 10.1162/089892903321208105.
The neural mechanisms and role of attention in the processing of visual form defined by luminance or motion cues were studied using magnetoencephalography. Subjects viewed bilateral stimuli composed of moving random dots and were instructed to covertly attend to either left or right hemifield stimuli in order to detect designated target stimuli that required a response. To generate form-from-motion (FFMo) stimuli, a subset of the dots could begin to move coherently to create the appearance of a simple form (e.g., square). In other blocks, to generate form-from-luminance (FFLu) stimuli that served as a control, a gray stimulus was presented superimposed on the randomly moving dots. Neuromagnetic responses were observed to both the FFLu and FFMo stimuli and localized to multiple visual cortical stages of analysis. Early activity in low-level visual cortical areas (striate/early extrastriate) did not differ for FFLu versus FFMo stimuli, nor as a function of spatial attention. Longer latency responses elicited by the FFLu stimuli were localized to the ventral-lateral occipital cortex (LO) and the inferior temporal cortex (IT). The FFMo stimuli also generated activity in the LO and IT, but only after first eliciting activity in the lateral occipital cortical region corresponding to MT/V5, resulting in a 50-60 msec delay in activity. All of these late responses (MT/V5, LO, and IT) were significantly modulated by spatial attention, being greatly attenuated for ignored FFLu and FFMo stimuli. These findings argue that processing of form in IT that is defined by motion requires a serial processing of information, first in the motion analysis pathway from V1 to MT/V5 and thereafter via the form analysis stream in the ventral visual pathway to IT.
利用脑磁图研究了注意力在由亮度或运动线索定义的视觉形式处理中的神经机制和作用。受试者观看由移动随机点组成的双侧刺激,并被指示 covertly 关注左或右半视野刺激,以检测需要做出反应的指定目标刺激。为了生成运动形成形式(FFMo)刺激,一部分点可以开始连贯移动以创建简单形式(例如正方形)的外观。在其他组块中,为了生成作为对照的亮度形成形式(FFLu)刺激,在随机移动的点上叠加呈现灰色刺激。观察到对FFLu和FFMo刺激的神经磁反应,并定位到多个视觉皮层分析阶段。低水平视觉皮层区域(纹状/早期纹外)的早期活动在FFLu与FFMo刺激之间没有差异,也不是空间注意力的函数。FFLu刺激引发的较长潜伏期反应定位在腹侧枕叶皮层(LO)和颞下皮层(IT)。FFMo刺激也在LO和IT中产生活动,但仅在首先在对应于MT/V5的枕叶外侧皮层区域引发活动之后,导致活动延迟50-60毫秒。所有这些晚期反应(MT/V5、LO和IT)都受到空间注意力的显著调节,对于被忽略的FFLu和FFMo刺激大大减弱。这些发现表明,由运动定义的IT中形式的处理需要信息的串行处理,首先在从V1到MT/V5的运动分析通路中,然后通过腹侧视觉通路中的形式分析流到IT。