![]() (2013) reported that cognitive data is associated with the degree of handedness (and not its direction) as inconsistent handedness seems to be related with better episodic memory and improved belief updating/cognitive flexibility. Indeed, a small advantage of right-handed people in spatial ability has been reported ( Somers et al., 2015) and pawedness/memory associations have been found in monkeys ( Hopkins and Washburn, 1994) and mice ( Wu et al., 2010). It has therefore been hypothesized that differences in this trait might be associated with other behavioral outcomes particularly cognition. Additionally, peripheral human ( Lengen et al., 2009) and central rodent ( Neveu, 1990 Shen et al., 2005) data have shown differences in the immunological system, while additional monoamines (norepinephrine Barnéoud et al., 1990) and enzymes (angiotensinases Wu et al., 2010) were also associated with rodent pawedness. Regarding morphology most studies have so far excluded any association ( Good et al., 2001 Narr et al., 2007 Guadalupe et al., 2014, 2016 Ocklenburg et al., 2016) however at cellular and molecular levels, contralateral parietal spine density has been linked to skilled reaching ( Ambeskovic et al., 2017) and dopaminergic system lateralization has been shown to be associated with hand/paw preference in humans ( de la Fuente-Fernández et al., 2000) as well as in rodents ( Uguru-Okorie and Arbuthnott, 1981 Schwarting et al., 1987 Barnéoud et al., 1990 Cabib et al., 1995 Nielsen et al., 1997 Budilin et al., 2008). Pawedness/handedness is thought to be associated with brain asymmetries, present both at morphological, cellular and molecular levels (see for reviews Galaburda et al., 1978 Toga and Thompson, 2003 Sun and Walsh, 2006 Rogers, 2009, 2014 Hugdahl, 2011). It corresponds, in general terms, to animals’ handedness. Pawedness reflects the preferential use and/or an increased capacity to perform tasks more efficiently with a specific paw. In conclusion, PaTRaT is able to reliably classify rats’ pawedness direction and degree. Additionally, these groups performed similarly in executive function and memory tasks. Left- and right-biased animals presented no differences in the ability to perform fine movements with any of the forelimbs (staircase) and general locomotor performance. Inter-rater consistency was very high between two experienced raters and substantial when two additional inexperienced raters were included. Individually, all animals presented marked side-preferences, >2 and <−2 for left- and right-sided bias, respectively, and this preference was stable across the three evaluations. At the population level 54% of the animals presented a rightward bias. To exclude potential bias, rats were also tested for paw fine movement and general locomotion in other behavioral paradigms as well as impulsivity (variable delay-to-signal, VDS), memory and cognitive flexibility (water maze). PaTRaT was repeated 4 and 8 weeks after the first evaluation. ![]() Animals were allowed to retrieve 10 rewards per session in a total of four sessions while their behavior was recorded. Due to its size, the reward could only cross the mesh if aligned with its diagonal, imposing additional coordination. Sprague-Dawley male rats were confined into a metal rectangular mesh cylinder, from which they can see, smell and reach sugared rewards with their paws. The PaTRaT consists in a classification system, ranging from +4 to −4 where increasingly positive and negative values reflect the bias for left or right paw use, respectively. We have therefore developed a semi-quantitative method-the pawdeness trait test (PaTRaT)-to evaluate paw preference degree in rats. However, paw preference and dexterity at population and individual levels are controversial as results are incongruent across paradigms. In rodents, dexterity is commonly analyzed in preference paradigms in which animals are given the chance to use either the left or the right front paws to manipulate food. 2ICVS/3B’s-PT Government Associate Laboratory, Braga, Portugal.1Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal.Guimarães 1,2 Nuno Sousa 1,2 Armando Almeida 1,2 Hugo Leite-Almeida 1,2* Cunha 1,2† Madalena Esteves 1,2† Sofia P.
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