Representation of the Numerosity ‘zero’ in the Parietal Cortex of the Monkey

Abstract

Zero is a fundamental concept in mathematics and modern science. Empty sets are considered a precursor of the concept of numerosity zero and a part of numerical continuum. How is numerosity zero (the absence of visual items) represented in the primate cortex? To address this question, we trained monkeys to perform numerical operations including numerosity zero. Here we show a group of neurons in the posterior parietal cortex of the monkey activated in response to numerosity ‘zero’. ‘Zero’ neurons are classified into exclusive and continuous types; the exclusive type discretely encodes numerical absence and the continuous type encodes numerical absence as a part of a numerical continuum. “Numerosity-zero” neurons enhance behavioral discrimination of not only zero numerosity but also non-zero numerosities. Representation of numerosity zero in the parietal cortex may be a precursor of non-verbal concept of zero in primates.

Common and distinct brain regions in both parietal and frontal cortex support symbolic and nonsymbolic number processing in humans: A functional neuroimaging meta-analysis

“…Nieder and Miller, 2003;Tudusciuc and Nieder, 2007). Overwhelming evidence indicates that the primate brain place codes numerosity (Andreas Okuyama et al, 2015) even in monkeys that were never trained to discriminate numbers (Viswanathan and Nieder, 2013). Converging evidence from human fMRI adaptation studies revealed that tuned number neurons respond to dot arrays (Jacob & Nieder, 2009;Piazza et al, 2004).…”

“Zeroing” in on mathematics in the monkey brain

“…A fascinating new study by Okuyama, Kuki, and Mushiake (2015) specifically assessed the contributions of parietal lobe activation in monkeys for the concept of zero, and these results further demonstrated continuity in numerical cognition across species. The concept of zero exists even in human societies without formal number notation systems.…”

“…Okuyama et al (2015) extended the behavioral assessment of zero to ask whether parietal contributions of the processing of empty sets fit the broader model of numerical representation in monkeys’ brains, or somehow looked qualitatively different. They did this by analyzing activity in the ventral intraparietal (VIP) cortex, an area previously shown to have numerosity-specific neurons in single-neuron recording studies with monkeys (e.g., Nieder & Miller, 2004).…”

“…Okuyama et al (2015) recorded activity in 614 cells in the VIP and found 185 neurons that showed selective activations to the numerosities 0 to 4 in the target presentation phase and 101 that did so during the delay period before manipulating set size began. Many of these were selectively activated by target zero.…”

A Place for Zero in the Brain

“…Results of a prior study indicated that primate VIP neurons encode zero numerosity, although the lack of in vivo single-cell recordings from the PFC[ 2 _ T D $ D I F F ] -[ 3 _ T D $ D I F F ] a key brain structure for the encoding of abstract quantity[ 4 _ T D $ D I F F ] -[ 5 _ T D $ D I F F ] prevented the authors from observing any possible dissociations within the parietofrontal number network [10]. This is what the study by RamirezCardenas and colleagues directly investigated [9].…”