| Objectives: We are surrounded by numbers.Numerical competence is an essential ability of everyday life.We use them for telling the time,counting items,calculating prices,solving equations,encoding credit cards,identifying flights,keeping score of sports games,choosing the shortest path to travel,estimating the shortest queue at the supermarket and so on.In the few decades,the study of numerical competence has become one of the focus issues in cognitive neuroscience.Numerical competence may be divided into four levels: relative numerousness judgments,number subitizing,number counting and number estimation.A large body of experimental evidence shows that non-human animals as diverse as mammals,birds,fishes,and honeybees have the capability to judge relative numerousness and subitize small numerousness.However,non-human animals having relative numerousness judgments and subitizing do not imply that they possess the ability to count.The counting ability of non-human animals has long been a source of fascination and contention to members of the academic and members of society alike,which is also a fundamental question in cognitive science.Unfortunately,there is no convincing evidence to support that non-human animals have the counting ability.Thus,firstly,we used eyeblink behaviour to establish an animal counting model and to explore whether the Sprague Dawley(SD)rats have the counting ability.Secondly,we used the optogenetic approach to explore the role of the ventrolateral orbital cortex(VLO)in the process of counting.Methods:(1)SD rats were trained with numerical cues consisted of n(n = 3–9)short tones(i.e.,Cues)with fixed intercue intervals to establish numerical discrimination eyeblink.(2)SD rats were trained with numerical cues consisted of n(n = 3–9)short tones(i.e.,Cues)with random intercue intervals to establish numerical discrimination eyeblink.(3)SD rats were trained with numerical cues consisted of n + 2(n = 3–5)short tones(i.e.,Cues)with random intercue intervals to establish counting eyeblink.(4)Investigating the effects of optogenetic inhibition of the bilateral VLO of learned rats on the counting eyeblink during the test session.Results:(1)88.89% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 3 short tones with fixed intercue intervals.(2)77.88% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 4 short tones with fixed intercue intervals.(3)77.88% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 5 short tones with fixed intercue intervals.(4)75.00% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 6 short tones with fixed intercue intervals.(5)60.00% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 7 short tones with fixed intercue intervals.(6)44.45% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 8 short tones with fixed intercue intervals.(7)33.33% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 9 short tones with fixed intercue intervals.(8)SD rats failed to learn the numerical discrimination eyeblink for numerical cues consisted of 4 short tones with fixed intercue intervals pseudopaired with periorbital electrical shock.(9)77.78% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 3 short tones with random intercue intervals.(10)88.89% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 4 short tones with random intercue intervals.(11)75.00% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 4 short tones with random intercue intervals.(12)63.64% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 5 short tones with random intercue intervals.(13)50.00% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 7 short tones with random intercue intervals.(14)30.00% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 8 short tones with random intercue intervals.(15)27.27% of SD rats learned the numerical discrimination eyeblink for numerical cues consisted of 9 short tones with random intercue intervals.(16)SD rats failed to learn the numerical discrimination eyeblink for numerical cues consisted of 4 short tones with random intercue intervals pseudopaired with periorbital electrical shock.(17)Analyzing each animals of the cue-alone unpaired training of the last 5 days during acquisition session,31.82% of SD rats learned the counting eyeblink for numerical cues consisted of 3 + 2 short tones with random intercue intervals.(18)Analyzing each animals of the cue-alone unpaired training of the last 5 days during acquisition session,8.70% of SD rats learned the counting eyeblink for numerical cues consisted of 4 + 2 short tones with random intercue intervals.(19)Analyzing each animals of the cue-alone unpaired training of the last 5 days during acquisition session,SD rats failed to learn the counting eyeblink for numerical cues consisted of 5 + 2 short tones with random intercue intervals.(20)Analying each animals of the cue-alone unpaired training of the last 5 days during acquisition session,SD rats failed to learn the counting eyeblink for numerical cues consisted of 4 + 2 500-ms short tones(increasing the length of each short tone)with random intercue intervals.(21)Optogenetic inhibition of the bilateral VLO of learned rats significantly impaired the counting eyeblink.Conclusion:SD rat possesses counting ability,and the VLO is involved in modulating the counting process.To our knowledge,this is the first study that shows the convincing evidence to support that non-human animals have the counting ability.Thus,the present study may provide an insight into understanding of the features and significances of the animal counting behaviour,the origin and evolution of the human numerical competence,and the neural mechanisms underlying counting process. |
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