Department of Psychology, University of Otago, Dunedin, New Zealand.
Department of Psychology, University of Otago, Dunedin, New Zealand.
Neurobiol Learn Mem. 2020 May;171:107214. doi: 10.1016/j.nlm.2020.107214. Epub 2020 Mar 20.
The avian Wulst is the pallial (analogous to mammalian cortex) termination point of the thalamofugal pathway, one of two main visual pathways in birds, and is considered to be equivalent to primate striate cortex. We recorded neuronal activity from the Wulst in pigeons during two versions of a delayed matching-to-sample procedure. Two birds were trained on a common outcomes (CO) procedure, in which correct responses following both the skateboarder and the flower stimuli were associated with reward. Two other birds were trained on a differential outcomes (DO) procedure in which correct responses following only the skateboarder stimulus were associated with reward, while correct responses following the flower stimulus were not rewarded. In line with previous studies, under CO conditions, and for both excitatory and inhibitory neurons, delay activity in the Wulst was significantly different from baseline activity following both sample stimuli, which may indicate that Wulst delay activity is a neural correlate of working memory for the sample stimulus. On the other hand, under DO conditions, Wulst delay activity appeared to be a neural correlate of the upcoming reward. We argue that Wulst neurons display flexibility in their encoding in that they can encode both sample and reward information, but may default to one type of coding over the other based on the demands of the task. The current study provides the first evidence that delay activity in the Wulst represents both a neural correlate for sample information as well as reward information.
禽类的脑顶是丘脑外通路的脑区终末点（类似于哺乳动物的皮质），它是鸟类的两个主要视觉通路之一，被认为相当于灵长类的纹状皮质。我们在两只鸽子的脑顶记录神经元活动，这两只鸽子在两种延迟匹配样本程序中接受了训练。两只鸟接受了常见结果（CO）程序的训练，在该程序中，滑板手和花刺激物的正确反应都与奖励相关联。另外两只鸟接受了不同结果（DO）程序的训练，在该程序中，只有在滑板手刺激物之后的正确反应才与奖励相关联，而在花刺激物之后的正确反应则没有奖励。与之前的研究一致，在 CO 条件下，无论是兴奋性神经元还是抑制性神经元，脑顶的延迟活动与两个样本刺激物后的基线活动都有显著差异，这可能表明脑顶的延迟活动是对样本刺激的工作记忆的神经相关物。另一方面，在 DO 条件下，脑顶的延迟活动似乎是即将到来的奖励的神经相关物。我们认为，脑顶神经元在编码方面具有灵活性，因为它们可以同时编码样本和奖励信息，但可能根据任务的要求，默认使用一种编码方式而不是另一种。本研究首次提供了证据表明，脑顶的延迟活动既代表了样本信息的神经相关物，也代表了奖励信息的神经相关物。
