The Sense of Number in Fish, with Particular Reference to Its Neurobiological Bases
Centre for Mind/Brain Sciences, University of Trento, 38068 Rovereto, Italy
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
Received: 20 August 2021
Revised: 13 October 2021
Accepted: 22 October 2021
Published: 27 October 2021
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.