Hartmann Konstantin, Veit Lena, Nieder Andreas
Animal Physiology, Institute of Neurobiology, University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
Exp Brain Res. 2018 Jan;236(1):215-226. doi: 10.1007/s00221-017-5120-3. Epub 2017 Nov 11.
Adaptive sequential behaviors rely on the bridging and integration of temporally separate information for the realization of prospective goals. Corvids' remarkable behavioral flexibility is thought to depend on the workings of the nidopallium caudolaterale (NCL), a high-level avian associative forebrain area. We trained carrion crows to remember visual items for three alternating delay durations in a delayed match-to-sample task and recorded single-unit activity from the NCL. Sample-selective delay activity, a correlate of visual working memory, was maintained throughout different working memory durations. Delay responses remained selective for the same preferred sample item across blocks with different delay durations. However, selectivity strength decreased with increasing delay durations, mirroring worsened behavioral performance with longer memory delays. Behavioral relevance of delay activity was further evidenced by reduced encoding of the preferred sample item during error trials. In addition, NCL neurons adapted their time-dependent discharges to blocks of different memory durations, so that delay duration could be successfully classified based on population activity a few trials after the delay duration switched. Therefore, NCL neurons not only maintain information from individual trials, but also keep track of the duration for which this information is needed in the context of the task. These results strengthen the role of corvid NCL in maintaining working memory for flexible control of temporally extended goal-directed behavior.
适应性序列行为依赖于对时间上分离的信息进行衔接和整合，以实现预期目标。鸦科动物卓越的行为灵活性被认为取决于尾外侧巢皮质（NCL）的运作，这是一个高级鸟类联想前脑区域。我们训练食腐鸦在延迟匹配样本任务中记住视觉项目，延迟时间有三种交替时长，并记录了NCL的单神经元活动。样本选择性延迟活动是视觉工作记忆的一个相关指标，在不同的工作记忆时长中都得以维持。在不同延迟时长的组块中，延迟反应对相同的偏好样本项目仍保持选择性。然而，选择性强度随着延迟时长的增加而降低，这与记忆延迟越长行为表现越差的情况相呼应。在错误试验期间，对偏好样本项目的编码减少，进一步证明了延迟活动的行为相关性。此外，NCL神经元会根据不同记忆时长的组块调整其随时间变化的放电，因此在延迟时长切换后的几次试验中，就可以根据群体活动成功地对延迟时长进行分类。因此，NCL神经元不仅能保留每次试验的信息，还能在任务背景下跟踪该信息所需的时长。这些结果强化了鸦科动物NCL在维持工作记忆以灵活控制时间延长的目标导向行为中的作用。
