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Title: Geometric ratio perception and preference among objects in rats
Authors: Pessoa, J. A.
Winnie, J.
Ribeiro, S.
Vasconcelos, N.
Nascimento, G.
Lobão-Soares, B.
Keywords: Fibonacci;Golden ratio;Memory;Mice;Novel Object Preference Test
Issue Date: Aug-2011
Portuguese Abstract: Objectives: The novel object preference test (NOPT) has been, in the last years, standardized for tasks in rodents as a behavioral parameter for evaluation of memory consolidation and also for evaluation of exploration preference among different objects presented at the same time. The geometric patterns of this preference are poorly understood and vary considering different species. In humans, it is known that body proportions close to gold ratio (1.618) are considered “aesthetic”. Considering fMRI studies, it is possible to observe differential signal activation of limbic areas in the human insula when individuals have visual contact with body segments with golden ratio. Nevertheless, as far as we know, no other geometric object preference study was performed in other species. The aim of this work was to evaluate in rats a possible exploration preference considering tripartite objects made with discrete variations of its proportions, and if they could disclose preference for same material made, but unfamiliar (new) objects when presented 24 hours after the first exposition. Methods and Results: On the first day, five male Wistar adult rats were placed in an open field arena with three steel objects composed by three stacked balls whose diameter follows three different ratios (1.2; 1.618/gold ratio; 1.8), placed at equidistant points. Twenty four hours after, these animals were exposed to the same objects of the first task, together with three new steel cylindrical objects (same proportions, height and size of the ball objects). Images were processed with any-maze behavior analysis software and time of object exploration was counted within each animal. ANOVA with Tukey´s post hoc test was performed for preference and memory tests, and p set at 0.05. On the first day, we found a huge object preference (p= 0.01) related to the 1.8 proportion balls (140.5 SD 36.09), when compared to both 1.618 (21.44 SD 8.91) and 1.2 ball (30.9 SD 19.58) composed objects. Surprisingly, on the second day the exploration time was similar in both familiar and unfamiliar objects, revealing no novel object preference in this case. Also, in the second exposition, they did not disclose any preference by a specific proportion, as they did in the first day for 1.8 balls, considering both ball and cylindrical objects (all p values > 0.05). Conclusions: We might expect a possible existence of an innate and species-specific pattern of aesthetic preference in rodents considering geometric evaluation of different proportions. Also, that only variation of proportions (not material variation of objects) may be not sufficient for studying memory consolidation in the NOPT. Finally, that when exposed to many objects, these animals may lose the preference for some exploration pattern related to a specific geometric proportion.
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