Reduced mastication stimulates impairment of spatial memory and degeneration of hippocampal neurons in aged SAMP8 mice

The involvement of reduced mastication in senile dementia was evaluated by examining the effect of cutting off the upper molars (molarless) on spatial memory and numbers of hippocampal neurons in aged SAMP8 mice. Molarless mi ce showed a decrease in both learning ability in a water maze and neuron de nsity in the hippocampal CA1 region compared with control mice. These chang es increased the longer the molarless condition persisted. The data suggest a possible link between reduced mastication and hippocampal neuron loss th at may be one risk factor for senile impairment of spatial memory. (C) 1999 Elsevier Science B.V. All rights reserved.