Rademaker Rosanne L, Serences John T
Ernst Strüngmann Institute for Neuroscience in cooperation with the Max Planck Society, Frankfurt, Germany.
Department of Psychology, University of California San Diego, La Jolla, California, USA.
bioRxiv. 2024 Sep 16:2024.09.16.613302. doi: 10.1101/2024.09.16.613302.
People often remember visual information over brief delays while actively engaging with ongoing inputs from the surrounding visual environment. Depending on the situation, one might prioritize mnemonic contents (i.e., remembering details of a past event), or preferentially attend sensory inputs (i.e., minding traffic while crossing a street). Previous fMRI work has shown that early sensory regions can simultaneously represent both mnemonic and passively viewed sensory information. Here we test the limits of such simultaneity by manipulating attention towards sensory distractors during a working memory task performed by human subjects during fMRI scanning. Participants remembered the orientation of a target grating while a distractor grating was shown during the middle portion of the memory delay. Critically, there were several subtle changes in the contrast and the orientation of the distractor, and participants were cued to either ignore the distractor, detect a change in contrast, or detect a change in orientation. Despite sensory stimulation being matched in all three conditions, the fidelity of memory representations in early visual cortex was highest when the distractor was ignored, intermediate when participants attended distractor contrast, and lowest when participants attended the orientation of the distractor during the delay. In contrast, the fidelity of distractor representations was lowest when ignoring the distractor, intermediate when attending distractor-contrast, and highest when attending distractor-orientation. These data suggest a trade-off in early sensory representations when engaging top-down feedback to attend both seen and remembered features and may partially explain memory failures that occur when subjects are distracted by external events.
人们在与周围视觉环境的持续输入进行积极互动时，能够在短暂延迟后记住视觉信息。根据具体情况，人们可能会优先处理记忆内容（即记住过去事件的细节），或者优先关注感官输入（即过马路时留意交通情况）。先前的功能磁共振成像（fMRI）研究表明，早期感觉区域可以同时表征记忆信息和被动观察到的感官信息。在此，我们通过在fMRI扫描期间让人类受试者执行工作记忆任务时，操纵对感官干扰物的注意力，来测试这种同时性的限度。参与者在记忆延迟的中间部分看到干扰光栅时，记住目标光栅的方向。关键的是，干扰光栅的对比度和方向有几个细微的变化，并且提示参与者要么忽略干扰物，检测对比度的变化，要么检测方向的变化。尽管在所有三种情况下感官刺激都是匹配的，但当忽略干扰物时，早期视觉皮层中记忆表征的保真度最高，当参与者关注干扰物的对比度时居中，而当参与者在延迟期间关注干扰物的方向时最低。相反，当忽略干扰物时，干扰物表征的保真度最低，当关注干扰物对比度时居中，而当关注干扰物方向时最高。这些数据表明，在利用自上而下的反馈来关注所见和所记特征时，早期感觉表征存在权衡，这可能部分解释了受试者被外部事件分散注意力时出现的记忆失误。
