Working memory capacity of crows and monkeys arises from similar neuronal computations

Complex cognition relies on flexible working memory, which is severely
limited in its capacity. The neuronal computations underlying these
capacity limits have been extensively studied in humans and in monkeys,
resulting in competing theoretical models. We probed the working memory
capacity of crows (Corvus corone) in a change detection task, developed
for monkeys (Macaca mulatta), while we performed extracellular recordings
of the prefrontal-like area nidopallium caudolaterale. We found that
neuronal encoding and maintenance of information were affected by item
load, in a way that is virtually identical to results obtained from monkey
prefrontal cortex. Contemporary neurophysiological models of working
memory employ divisive normalization as an important mechanism that may
result in the capacity limitation. As these models are usually
conceptualized and tested in an exclusively mammalian context, it remains
unclear if they fully capture a general concept of working memory or if
they are restricted to the mammalian neocortex. Here we report that
carrion crows and macaque monkeys share divisive normalization as a
neuronal computation that is in line with mammalian models. This indicates
that computational models of working memory developed in the mammalian
cortex can also apply to non-cortical associative brain regions of birds.