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Open Access Highly Accessed Research article

Enriched environment and masticatory activity rehabilitation recover spatial memory decline in aged mice

Fabíola de Carvalho Chaves de Siqueira Mendes1, Marina Negrão Frota de Almeida1, André Pinheiro Gurgel Felício1, Ana Carla Fadel1, Diego de Jesus Silva1, Thaíssa Gomes Borralho1, Rodrigo Perez da Silva1, João Bento-Torres1, Pedro Fernando da Costa Vasconcelos2, Victor Hugh Perry3, Edson Marcos Leal Soares Ramos4, Cristovam Wanderley Picanço-Diniz1 and Marcia Consentino Kronka Sosthenes1*

Author affiliations

1 Universidade Federal do Pará/UFPA, Instituto de Ciências Biológicas, Laboratório de Investigações em Neurodegeneração e Infecção, Hospital Universitário João de Barros Barreto, Rua dos Mundurucus, 4487 – Guamá Belém, Pará, Brasil

2 Instituto Evandro Chagas/ IEC, Departamento de Arbovirologia e Febres Hemorrágicas, Ananindeua, Pará, Brasil

3 Southampton Neuroscience Group, School of Biological Sciences, University of Southampton, Southhampton, UK

4 Universidade Federal do Pará/UFPA, Instituto de Ciências Exatas e Naturais, Laboratório de Sistema de Informação e Georrefrenciamento, Pará, Brasil

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Citation and License

BMC Neuroscience 2013, 14:63  doi:10.1186/1471-2202-14-63

Published: 28 June 2013

Abstract

Background

To measure the impact of masticatory reduction on learning and memory, previous studies have produced experimental masticatory reduction by modified diet or molar removal. Here we induced spatial learning impairment in mice by reducing masticatory activity and then tested the effect of a combination of environmental enrichment and masticatory rehabilitation in recovering spatial learning at adulthood and in later life. For 6 months (6M) or 18 months (18M), we fed three groups of mice from postnatal day 21 respectively with a hard diet (HD) of pellets; pellets followed by a powdered, soft diet (HD/SD, divided into equal periods); or pellets followed by powder, followed by pellets again (HD/SD/HD, divided into equal periods). To mimic sedentary or active lifestyles, half of the animals from each group were raised from weaning in standard cages (impoverished environment; IE) and the other half in enriched cages (enriched environment; EE). To evaluate spatial learning, we used the Morris water maze.

Results

IE6M-HD/SD mice showed lower learning rates compared with control (IE6M-HD) or masticatory rehabilitated (IE6MHD/SD/HD) animals. Similarly, EE-HD/SD mice independent of age showed lower performance than controls (EE-HD) or rehabilitated mice (EE-HD/SD/HD). However, combined rehabilitation and EE in aged mice improved learning rate up to control levels. Learning rates did not correlate with swim speed.

Conclusions

Reduction in masticatory activity imposed on mice previously fed a hard diet (HD/SD) impaired spatial learning in the Morris water maze. In adults, masticatory rehabilitation recovered spatial abilities in both sedentary and active mice, and rehabilitation of masticatory activity combined with EE recovered these losses in aged mice.

Keywords:
Mastication; Enriched environment; Masticatory rehabilitation; Spatial learning; Morris water maze