Electrical Neuroimaging Group Geneva, Switzerland.
Front Psychol. 2013 Nov 18;4:845. doi: 10.3389/fpsyg.2013.00845. eCollection 2013.
The retina is one of the best known quantum detectors with rods able to reliably respond to single photons. However, estimates on the number of photons eliciting conscious perception, based on signal detection theory, are systematically above these values after discounting by retinal losses. One possibility is that there is a trade-off between the limited motor resources available to living systems and the excellent reliability of the visual photoreceptors. On this view, the limits to sensory thresholds are not set by the individual reliability of the receptors within each sensory modality (as often assumed) but rather by the limited central processing and motor resources available to process the constant inflow of sensory information. To investigate this issue, we reproduced the classical experiment from Hetch aimed to determine the sensory threshold in human vision. We combined a careful physical control of the stimulus parameters with high temporal/spatial resolution recordings of EEG signals and behavioral variables over a relatively large sample of subjects (12). Contrarily to the idea that the limits to visual sensitivity are fully set by the statistical fluctuations in photon absorption on retinal photoreceptors we observed that the state of ongoing neural oscillations before any photon impinges the retina helps to determine if the responses of photoreceptors have access to central conscious processing. Our results suggest that motivational and attentional off-retinal mechanisms play a major role in reducing the QE efficiency of the human visual system when compared to the efficiency of isolated retinal photoreceptors. Yet, this mechanism might subserve adaptive behavior by enhancing the overall multisensory efficiency of the whole system composed by diverse reliable sensory modalities.
视网膜是最著名的量子探测器之一，其杆状细胞能够可靠地对单个光子做出反应。然而，根据信号检测理论，在扣除视网膜损耗后，基于有意识感知的光子数量估计值系统地高于这些值。一种可能性是，在有限的生命系统运动资源和视觉光感受器的卓越可靠性之间存在权衡。根据这种观点，感觉阈值的限制不是由每个感觉模态内的单个感受器的可靠性（如通常假设的那样）设定的，而是由处理感官信息持续流入的有限的中央处理和运动资源设定的。为了研究这个问题，我们重现了 Hetch 进行的经典实验，旨在确定人类视觉的感觉阈值。我们将刺激参数的仔细物理控制与 EEG 信号的高时间/空间分辨率记录以及相对较大的受试者样本（12 个）的行为变量相结合。与视觉敏感性的限制完全由视网膜光感受器吸收光子的统计波动设定的观点相反，我们观察到，在任何光子撞击视网膜之前进行的正在进行的神经振荡状态有助于确定光感受器的反应是否能够进入中央意识处理。我们的结果表明，与孤立的视网膜光感受器的效率相比，动机和注意力的离视网膜机制在降低人类视觉系统的 QE 效率方面发挥了主要作用。然而，这种机制可能通过增强由各种可靠感觉模态组成的整个系统的整体多感官效率来促进适应性行为。
