Experts believe eating like our ancestors could keep the brain healthy.
Scientists said mice fed powdered food had weaker jaws – and fewer neurons in the hippocampus, which is part of the brain which controls memory.
It suggested that maintaining or strengthening chewing would be effective in preventing dementia and memory and learning dysfunction.
The findings supports previous studies which revealed elderly people with fewer teeth are more likely to develop the neurological condition.
The researchers said recently, chewing frequency has dramatically decreased along with changes in dietary habits – because people are relying less on raw food.
Jaw stimulation – the act of chewing – boosts the development of the central nervous system and maxillofacial tissue – that covers the head, neck, face and jaws – in children.
Experts set out to discover the link between chewing and brain function.
They found the growth of jaw bone and muscle were suppressed in mice with that were fed powdered food, so they had to chew less.
Behavioural tests revealed this reduced chewing impaired memory and learning functions.
When put in a cage with a light or dark compartment, mice fed powdered chow rather than pellets were much less likely to recall 24 hours later that the latter exposed them to an electric shock.
This meant their long term memory had been affected by the diet.
Professor Takashi Ono, of Tokyo Medical and Dental University, said: “Mastication is an indispensable oral function related to physical, mental, and social health throughout life.
“The elderly tend to have a masticatory dysfunction due to tooth loss and fragility in the masticatory muscles with ageing, potentially resulting in impaired cognitive function.
“Masticatory stimulation has influence on the development of the central nervous system (CNS) as well as the growth of maxillofacial tissue in children.”
He said chewing and brain function is important during growth.
“Here, we show that the reduced mastication resulted in impaired spatial memory and learning function owing to the morphological change and decreased activity in the hippocampus,” he explained.
“We used a model for reduced masticatory stimuli, in which juvenile mice were fed with powder diet and found that masticatory stimulation during the growth period positively regulated long-term spatial memory to promote cognitive function.
The researchers said in the hippocampus, a major component responsible for memory, neural activity and synapse formation were reduced in these mice.
Experts said there should be further studies investigating the link between chewing and brain function.
The study was published in the Journal of Dental Research.