Radboud University Nijmegen, Donders Institute for Brain, Cognition, and Behaviour, 6500 HB Nijmegen, The Netherlands.
J Neurosci. 2011 Apr 6;31(14):5365-77. doi: 10.1523/JNEUROSCI.6472-10.2011.
Most evidence that the brain uses Bayesian inference to integrate noisy sensory signals optimally has been obtained by showing that the noise levels in each modality separately can predict performance in combined conditions. Such a forward approach is difficult to implement when the various signals cannot be measured in isolation, as in spatial orientation, which involves the processing of visual, somatosensory, and vestibular cues. Instead, we applied an inverse probabilistic approach, based on optimal observer theory. Our goal was to investigate whether the perceptual differences found when probing two different states--body-in-space and head-in-space orientation--can be reconciled by a shared scheme using all available sensory signals. Using a psychometric approach, seven human subjects were tested on two orientation estimates at tilts < 120°: perception of body tilt [subjective body tilt (SBT)] and perception of visual vertical [subjective visual vertical (SVV)]. In all subjects, the SBT was more accurate than the SVV, which showed substantial systematic errors for tilt angles beyond 60°. Variability increased with tilt angle in both tasks, but was consistently lower in the SVV. The sensory integration model fitted both datasets very nicely. A further experiment, in which supine subjects judged their head orientation relative to the body, independently confirmed the predicted head-on-body noise by the model. Model predictions based on the derived noise properties from the various modalities were also consistent with previously published deficits in vestibular and somatosensory patients. We conclude that Bayesian computations can account for the typical differences in spatial orientation judgments associated with different task requirements.
大多数表明大脑使用贝叶斯推断来优化整合噪声感觉信号的证据都是通过显示每种模态中的噪声水平可以预测组合条件下的性能来获得的。当各种信号不能单独测量时，例如在空间定向中涉及视觉、躯体感觉和前庭线索的处理时，这种正向方法很难实施。相反，我们应用了基于最优观测器理论的逆概率方法。我们的目标是研究当探测两种不同状态（身体在空间中的状态和头部在空间中的状态）时，是否可以通过使用所有可用感觉信号的共享方案来协调发现的知觉差异。使用心理物理方法，七名人类受试者在 <120°的倾斜角度下测试了两个方向估计：身体倾斜的感知[主观身体倾斜 (SBT)]和视觉垂直的感知[主观视觉垂直 (SVV)]。在所有受试者中，SBT 比 SVV 更准确，SVV 在超过 60°的倾斜角度下显示出明显的系统误差。在两个任务中，变异性随倾斜角度的增加而增加，但在 SVV 中始终较低。感觉整合模型非常适合这两个数据集。在另一个实验中，仰卧的受试者相对于身体判断他们的头部方向，独立地证实了模型预测的头部与身体之间的噪声。基于各种模态得出的噪声特性的模型预测也与前庭和躯体感觉患者先前发表的缺陷一致。我们得出结论，贝叶斯计算可以解释与不同任务要求相关的典型空间定向判断差异。
