Nieder Andreas, Miller Earl K
Massachusetts Institute of Technology, USA.
J Cogn Neurosci. 2004 Jun;16(5):889-901. doi: 10.1162/089892904970807.
Monkeys have been introduced as model organisms to study neural correlates of numerical competence, but many of the behavioral characteristics of numerical judgments remain speculative. Thus, we analyzed the behavioral performance of two rhesus monkeys judging the numerosities 1 to 7 during a delayed match-to-sample task. The monkeys showed similar discrimination performance irrespective of the exact physical appearance of the stimuli, confirming that performance was based on numerical information. Performance declined smoothly with larger numerosities, and reached discrimination threshold at numerosity "4." The nonverbal numerical representations in monkeys were based on analog magnitudes, object tracking process ("subitizing") could not account for the findings because the continuum of small and large numbers shows a clear Weber fraction signature. The lack of additional scanning eye movements with increasing set sizes, together with indistinguishable neuronal response latencies for neurons with different preferred numerosities, argues for parallel encoding of numerical information. The slight but significant increase in reaction time with increasing numerosities can be explained by task difficulty and consequently time-consuming decision processes. The behavioral results are compared to single-cell recordings from the prefrontal cortex in the same subjects. Models for numerosity discrimination that may account for these results are discussed.
猴子已被引入作为研究数字能力神经关联的模型生物，但数字判断的许多行为特征仍属推测。因此，我们分析了两只恒河猴在延迟样本匹配任务中判断1至7数量的行为表现。无论刺激的确切物理外观如何，猴子都表现出相似的辨别能力，这证实了其表现是基于数字信息的。随着数量的增加，表现平稳下降，并在数量“4”时达到辨别阈值。猴子的非语言数字表征基于模拟量，对象跟踪过程（“即时计数”）无法解释这些发现，因为小数字和大数字的连续体显示出明显的韦伯分数特征。随着集合大小增加，没有额外的扫视眼动，以及不同偏好数量的神经元具有无法区分的神经元反应潜伏期，这支持了数字信息的并行编码。随着数量增加，反应时间略有但显著增加，这可以用任务难度以及随之而来的耗时决策过程来解释。将行为结果与同一受试者前额叶皮层的单细胞记录进行了比较。讨论了可能解释这些结果的数字辨别模型。
