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Review

The Sense of Number in Fish, with Particular Reference to Its Neurobiological Bases

1
Centre for Mind/Brain Sciences, University of Trento, 38068 Rovereto, Italy
2
Department of Psychology and Cognitive Science, University of Trento, 38068 Rovereto, Italy
*
Authors to whom correspondence should be addressed.
Academic Editors: Maria Elena Miletto Petrazzini and Vera Schluessel
Animals 2021, 11(11), 3072; https://doi.org/10.3390/ani11113072
Received: 20 August 2021 / Revised: 13 October 2021 / Accepted: 22 October 2021 / Published: 27 October 2021
(This article belongs to the Special Issue Current Progress in Fish Cognition and Behaviour)
The ability to deal with quantity, both discrete (numerosities) and continuous (spatial or temporal extent) developed from an evolutionarily conserved system for approximating numerical magnitude. Non-symbolic number cognition based on an approximate sense of magnitude has been documented in a variety of vertebrate species, including fish. Fish, in particular zebrafish, are widely used as models for the investigation of the genetics and molecular mechanisms of behavior, and thus may be instrumental to development of a neurobiology of number cognition. We review here the behavioural studies that have permitted to identify numerical abilities in fish, and the current status of the research related to the neurobiological bases of these abilities with special reference to zebrafish. Combining behavioural tasks with molecular genetics, molecular biology and confocal microscopy, a role of the retina and optic tectum in the encoding of continuous magnitude in larval zebrafish has been reported, while the thalamus and the dorso-central subdivision of pallium in the encoding of discrete magnitude (number) has been documented in adult zebrafish. Research in fish, in particular zebrafish, may reveal instrumental for identifying and characterizing the molecular signature of neurons involved in quantity discrimination processes of all vertebrates, including humans.
It is widely acknowledged that vertebrates can discriminate non-symbolic numerosity using an evolutionarily conserved system dubbed Approximate Number System (ANS). Two main approaches have been used to assess behaviourally numerosity in fish: spontaneous choice tests and operant training procedures. In the first, animals spontaneously choose between sets of biologically-relevant stimuli (e.g., conspecifics, food) differing in quantities (smaller or larger). In the second, animals are trained to associate a numerosity with a reward. Although the ability of fish to discriminate numerosity has been widely documented with these methods, the molecular bases of quantities estimation and ANS are largely unknown. Recently, we combined behavioral tasks with molecular biology assays (e.g c-fos and egr1 and other early genes expression) showing that the thalamus and the caudal region of dorso-central part of the telencephalon seem to be activated upon change in numerousness in visual stimuli. In contrast, the retina and the optic tectum mainly responded to changes in continuous magnitude such as stimulus size. We here provide a review and synthesis of these findings. View Full-Text
Keywords: fish cognition; numerosity cognition; quantity discrimination; approximate number system fish cognition; numerosity cognition; quantity discrimination; approximate number system
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MDPI and ACS Style

Messina, A.; Potrich, D.; Schiona, I.; Sovrano, V.A.; Vallortigara, G. The Sense of Number in Fish, with Particular Reference to Its Neurobiological Bases. Animals 2021, 11, 3072. https://doi.org/10.3390/ani11113072

AMA Style

Messina A, Potrich D, Schiona I, Sovrano VA, Vallortigara G. The Sense of Number in Fish, with Particular Reference to Its Neurobiological Bases. Animals. 2021; 11(11):3072. https://doi.org/10.3390/ani11113072

Chicago/Turabian Style

Messina, Andrea, Davide Potrich, Ilaria Schiona, Valeria A. Sovrano, and Giorgio Vallortigara. 2021. "The Sense of Number in Fish, with Particular Reference to Its Neurobiological Bases" Animals 11, no. 11: 3072. https://doi.org/10.3390/ani11113072

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