Limits on perceptual capacity result in various phenomena of inattentional blindness. Here we propose a neurophysiological account attributing these perceptual capacity limits directly to limits on cerebral cellular metabolism. We hypothesized that overall cerebral energy supply remains constant, regardless of overall mental processing demands; therefore, an attention mechanism is required to regulate limited cellular metabolism levels in line with attended task demands. Increased perceptual load in a task (imposing a greater demand on neural computations) should thus result in increased metabolism underlying attended processing, and reduced metabolism mediating unattended processing. We tested this prediction measuring oxidation states of cytochrome c oxidase (oxCCO), an intracellular marker of cellular metabolism. Broadband near-infrared spectroscopy was used to record oxCCO levels from human visual cortex while participants (both sexes) performed a rapid sequential visual search task under either high perceptual load (complex feature-conjunction search) or low load (feature pop-out search). A task-irrelevant, peripheral checkerboard was presented on a random half of trials. Our findings showed that oxCCO levels in visual cortex regions responsive to the attended-task stimuli were increased in high versus low perceptual load, whereas oxCCO levels related to unattended processing were significantly reduced. A negative temporal correlation of these load effects further supported our metabolism trade-off account. These results demonstrate an attentional compensation mechanism that regulates cellular metabolism levels according to processing demands. Moreover, they provide novel evidence for the widely held stipulation that overall cerebral metabolism levels remain constant regardless of mental task demand and establish a neurophysiological account for capacity limits in perception.

SIGNIFICANCE STATEMENT We investigated whether capacity limits in perception can be explained by the effects of attention on the allocation of limited cellular metabolic energy for perceptual processing. We measured the oxidation state of cytochrome c oxidase, an intracellular measure of metabolism, in human visual cortex during task performance. The results showed increased levels of cellular metabolism associated with attended processing and reduced levels of metabolism underlying unattended processing when the task was more demanding. A temporal correlation between these effects supported an attention-directed metabolism trade-off. These findings support an account for inattentional blindness grounded in cellular biochemistry. They also provide novel evidence for the claim that cerebral processing is limited by a constant energy supply, which thus requires attentional regulation.

知觉能力的限制会导致各种注意力不集中的现象。在这里，我们提出了将这些知觉能力限制直接归因于脑细胞代谢限制的神经生理学解释。我们假设，不管整体的心理处理需求如何，整体的脑能量供应都保持不变。因此，需要一种注意机制来调节有限的细胞新陈代谢水平，以符合需要参加的任务要求。因此，任务中感性负载的增加（对神经计算的要求更高）应该导致参与处理的新陈代谢增加，并且介导无人参与的处理的新陈代谢减少。我们测试了预测细胞色素c氧化态的预测氧化酶（oxCCO），一种细胞代谢的细胞内标志物。宽带近红外光谱用于记录人类视觉皮层中的oxCCO水平，而参与者（男女）在高感知负荷（复杂特征结合搜索）或低负荷（特征弹出搜索）下执行快速顺序视觉搜索任务。在随机的一半试验中展示了与任务无关的外围棋盘格。我们的研究结果表明，在高知觉负载和低知觉负载下，视觉响应皮层区域中的oxCCO水平增加，而无人值守处理相关的oxCCO水平显着降低。这些负荷效应的负时间相关性进一步支持了我们的新陈代谢平衡帐户。这些结果证明了注意力补偿机制，其根据加工需求调节细胞代谢水平。而且，它们为广泛的规定提供了新的证据，即无论脑力需求如何，整体脑代谢水平保持恒定，并建立了感知能力极限的神经生理学解释。

意义声明我们研究了知觉能力极限是否可以通过注意力对有限的细胞代谢能分配给感知加工的影响来解释。我们测量了细胞色素c的氧化态氧化酶，一种细胞内新陈代谢的量度，在执行任务时在人的视觉皮层中。结果显示，当任务要求更高时，与参与的处理相关的细胞代谢水平升高，而无人参与的处理背后的代谢水平降低。这些效应之间的时间相关性支持了注意力导向的新陈代谢权衡。这些发现支持了基于细胞生物化学的无意识失明的解释。他们还为大脑加工受到恒定能量供应的限制提供了新的证据，因此需要注意调节。