Poncet Marlene, Batziou Paraskevi, Chakravarthi Ramakrishna
Department of Psychology, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, United Kingdom.
School of Psychology, University of Aberdeen, King's College, Aberdeen, AB24 3FX, United Kingdom.
Cereb Cortex. 2025 Aug 1;35(8). doi: 10.1093/cercor/bhaf212.
Object categorization is essential to navigate everyday life. It is ultra-rapid, can be completed by purely feedforward mechanisms, and is therefore thought to rely on neural representations that are robust. But how do these representations adapt when category boundaries change (eg buying fruit versus buying apples)? We tested this by asking participants to categorize images at different levels of abstraction while measuring their scalp electrical activity (EEG) with high temporal resolution. Participants categorized images either at the superordinate (animal/non-animal) or at the basic (bird/non-bird) level. We compared classification accuracy and representational similarity of EEG signals between birds, non-bird animals, and vehicles to determine if neural representations are modified according to categorical requirements. We found that neural representations of birds and non-bird animals were indistinguishable in the superordinate task but were separable in the basic task from ~250 ms. On the other hand, the separability of neural representations between non-bird animals and vehicles did not differ by task. These findings suggest that top-down influences modulate categorical representations as needed, but only if discrimination is difficult. We conclude that neural representations of categories are adaptively altered to suit the current task requirements.
物体分类对于日常生活导航至关重要。它速度极快，可以通过纯粹的前馈机制完成，因此被认为依赖于稳健的神经表征。但是当类别边界发生变化时（例如购买水果与购买苹果），这些表征是如何适应的呢？我们通过要求参与者在不同抽象层次上对图像进行分类，同时以高时间分辨率测量他们的头皮电活动（脑电图）来测试这一点。参与者在上级（动物/非动物）或基本（鸟类/非鸟类）层次上对图像进行分类。我们比较了鸟类、非鸟类动物和车辆之间脑电图信号的分类准确率和表征相似性，以确定神经表征是否根据分类要求进行了修改。我们发现，在上级任务中，鸟类和非鸟类动物的神经表征无法区分，但在基本任务中，从约250毫秒开始就可以区分。另一方面，非鸟类动物和车辆之间神经表征的可分离性在不同任务中没有差异。这些发现表明，自上而下的影响会根据需要调节分类表征，但前提是辨别困难。我们得出结论，类别的神经表征会适应性地改变以适应当前的任务要求。
