Carlson Bruce A, Kawasaki Masashi
Department of Biology, University of Virginia, Charlottesville, Virginia 22904, USA.
J Neurosci. 2006 Sep 6;26(36):9173-83. doi: 10.1523/JNEUROSCI.1513-06.2006.
Accurate sensory perception often depends on the independent encoding and subsequent integration of multiple stimulus attributes. In the weakly electric fish Eigenmannia, P- and T-type primary afferent fibers are specialized for encoding the amplitude and phase, respectively, of electrosensory stimuli. We used a stimulus estimation technique to quantify the ability of P- and T-units to encode random modulations in amplitude and phase. As expected, P-units exhibited a clear preference for encoding amplitude modulations, whereas T-units exhibited a clear preference for encoding phase modulations. Surprisingly, both types of afferents also encoded their nonpreferred stimulus attribute when it was presented in isolation or when the preferred stimulus attribute was sufficiently weak. Because afferent activity can be affected by modulations in either amplitude or phase, it is not possible to unambiguously distinguish between these two stimulus attributes by observing the activity of a single afferent fiber. Simple model neurons with a preference for encoding either amplitude or phase also encoded their nonpreferred stimulus attribute when it was presented in isolation, suggesting that such ambiguity is unavoidable. Using the well known jamming avoidance response as a probe of electrosensory perception, we show that the ambiguity at the single-neuron level gives rise to a systematic misrepresentation of stimuli at the population level and a resulting misperception of the amplitude and phase of electrosensory stimuli.
准确的感官感知通常取决于多种刺激属性的独立编码及随后的整合。在弱电鱼裸背电鳗中，P型和T型初级传入纤维分别专门用于编码电感觉刺激的幅度和相位。我们使用一种刺激估计技术来量化P单元和T单元编码幅度和相位随机调制的能力。正如预期的那样，P单元在编码幅度调制方面表现出明显的偏好，而T单元在编码相位调制方面表现出明显的偏好。令人惊讶的是，当单独呈现非偏好刺激属性或偏好刺激属性足够弱时，这两种类型的传入纤维也会编码它们的非偏好刺激属性。由于传入活动会受到幅度或相位调制的影响，因此通过观察单个传入纤维的活动无法明确区分这两种刺激属性。对编码幅度或相位有偏好的简单模型神经元在单独呈现非偏好刺激属性时也会对其进行编码，这表明这种模糊性是不可避免的。我们使用众所周知的避干扰反应作为电感觉感知的探针，结果表明，单神经元水平的模糊性会导致群体水平上刺激的系统性错误表征，进而导致对电感觉刺激的幅度和相位产生错误感知。
