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

Abstract

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.

Oscillations without cortex: Working memory modulates brainwaves in the endbrain of crows

“…For example, the capacity of WM, the number of individual items that can be maintained simultaneously, is comparable between crows and macaque monkeys (Balakhonov & Rose, 2017). Even single neuron correlates of WM in birds are virtually identical to those in mammals (Ditz & Nieder, 2016, 2020; Moll & Nieder, 2015; Rinnert et al, 2019; Rose & Colombo, 2005) and we recently found that this also extends to the neurophysiological limits of WM capacity (Buschman et al, 2011; Hahn et al, 2021).…”

“…4C) that simultaneously promotes selective neuronal activity without runaway excitation due to divisive normalization (Fries, 2015; Lundqvist et al, 2010). Together with analysis from single-neuron activity in crows (Hahn et al, 2021), it suggests that crow gamma could have a similar role in selection and normalization despite being implemented on a different neural substrate.…”

“…Our animals, experimental setup, behavioral protocol, recording setup, and surgical procedures were previously described in (Hahn et al, 2021).…”

“…The behavioral paradigm was executed by custom code written in Matlab using the Psychophysics (Brainard, 1997) and Biopsychology toolboxes (Rose et al, 2008). Further details about the experimental setup have been reported in (Hahn et al, 2021).…”

K-clique percolation in free association networks. The mechanism behind the 7 ± 2 law?

“…One could question why only the low size clique percolation in the human brain is possible although naively we could expect that the brain would prefer the higher working memory capacity. In particular a limit of the working memory capacity for human is higher then of other animals 35 and it is assumed that higher working memory corresponds to higher intellect. The answer certainly should involve some evolutionary arguments and at least two alternative scenario are possible.…”