Format-dependent and format-independent representation of sequential and simultaneous numerosity in the crow endbrain

Helen M Ditz,Andreas Nieder

doi:10.1038/s41467-020-14519-2

Abstract

Humans’ symbolic counting skills are built on a primordial ability to approximately estimate the number of items, or numerosity. To date it is debated whether numerosities presented in categorically different formats, that is as temporal sequences versus spatial arrays, are represented abstractly in the brain. To address this issue, we identified the behavioral characteristics and neuronal codes for sequential and simultaneous number formats in crows. We find a format-dependent representation by distinct groups of selective neurons during the sensory encoding stage. However, an abstract and format-independent numerosity code emerges once the encoding phase is completed and numerosities needed to be memorized. These results suggest a successive two-stage code for categorically different number formats and help to reconcile conflicting findings observed in psychophysics and brain imaging.

Highlights

Humans’ symbolic counting skills are built on a primordial ability to approximately estimate the number of items, or numerosity
nidopallium caudolaterale (NCL) neurons respond to the number of items that are displayed in spatial arrays and can be perceived from this specific, simultaneous number format[31,32,33]
Behavioral experiments in humans and monkeys have demonstrated that numerosity judgment show identical characteristics for sequential and simultaneous presentation formats[34,35]. This was taken as evidence that judgments of numerosity are abstract and based on the same approximate number system

Summary

Introduction

Humans’ symbolic counting skills are built on a primordial ability to approximately estimate the number of items, or numerosity To date it is debated whether numerosities presented in categorically different formats, that is as temporal sequences versus spatial arrays, are represented abstractly in the brain. Numerosity as an abstract quantity must be represented when items are presented one-by-one in temporal succession, but its underlying neuronal substrate is unclear Both psychophysical[34,35,36,37] and brain imaging studies in humans[38] report conflicting results and, depending on the respective findings, argue that sequential and simultaneous number formats access the same approximate number system, or different systems, respectively.

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Conclusion