Tunhe Zhou’s research while affiliated with Stockholm University and other places

Lately, there has been an emphasis on the importance of studying inter-individual variation in animal behaviour and cognition and understanding its underlying mechanisms. What was once considered mere noise around population mean can be explained by individual characteristics such as brain morphology and functionality. However, logistical limitations can be faced when studying the brain, especially for research involving wild animals, such as dealing with small sample sizes and time-consuming methods. Here, we combined an efficient and accurate method using X-ray micro-tomography and deep-learning (DL) segmentation to estimate the volume of six main brain areas of wild lizards, Podarcis bocagei: olfactory bulbs, telencephalon, diencephalon, midbrain, cerebellum and brain stem. Through quantitative comparison, we show that a sufficient deep-learning neural network can be trained with as few as five data sets. From this, we applied the trained deep-learning algorithm to obtain volume data of the six brain regions from 29 brains of Podarcis bocagei. We provide a detailed protocol for our methods, including sample preparation, X-ray tomography, and 3D volumetric segmentation. Our work is open-access and freely available, with the potential to benefit researchers in various fields, such as animal physiology, biomedical studies, and computer sciences.

Some cognitive abilities are suggested to be the result of a complex social life, allowing individuals to achieve higher fitness through advanced strategies. However, most evidence is correlative. Here, we provide an experimental investigation of how group size and composition affect brain and cognitive development in the guppy (Poecilia reticulata). For six months, we reared sexually mature females in one of three social treatments: a small conspecific group of three guppies, a large heterospecific group of three guppies and three splash tetras (Copella arnoldi)-a species that co-occurs with the guppy in the wild, and a large conspecific group of six guppies. We then tested the guppies' performance in self-control (inhibitory control), operant conditioning (associative learning) and cognitive flexibility (reversal learning) tasks. Using X-ray imaging, we measured their brain size and major brain regions. Larger groups of six individuals, both conspecific and heterospecific groups, showed better cognitive flexibility than smaller groups, but no difference in self-control and operant conditioning tests. Interestingly, while social manipulation had no significant effect on brain morphology, relatively larger telencephalons were associated with better cognitive flexibility. This suggests alternative mechanisms beyond brain region size enabled greater cognitive flexibility in individuals from larger groups. Although there is no clear evidence for the impact on brain morphology, our research shows that living in larger social groups can enhance cognitive flexibility. This indicates that the social environment plays a role in the cognitive development of guppies.

Complex cognitive performance is suggested to be the out-turn of complex social life, allowing individuals to achieve higher fitness through sophisticated "Machiavellian" strategies. Although there is ample support for this concept, especially when comparing species, most of the evidence is correlative. Here we provide an experimental investigation of how group size and composition may affect brain and cognitive development in the guppy (Poecilia reticulata). For six months, we reared sexually mature female guppies in one of three different social treatments: (i) three female guppies; (ii) three female guppies mixed with three female splash tetras (Copella arnoldi), a species that co-occurs with the guppy in the wild; and (iii) six female guppies. We then tested the guppies' performance in inhibitory control, associative learning and reversal learning tasks to evaluate their self-control, operant conditioning and cognitive flexibility capabilities. Afterwards, we estimated their brain size and the size of major brain regions using X-ray imaging technology. We found that individuals in larger groups of six individuals, in both same and mixed species treatments, outperformed individuals from the smaller groups of three guppies in reversal learning, with no apparent differences in the inhibitory control and associative learning tasks. This is rare evidence of how living in larger social groups improves cognitive flexibility, supporting that social pressures play an important role in shaping individual cognitive development. Interestingly, social manipulation had no apparent effect on brain morphology, but relatively larger telencephalons were associated with better individual performance in reversal learning. This suggests alternative mechanisms beyond brain region size enabled greater cognitive flexibility in individuals from larger groups.