New York, Aug 4 (IANS): Exercise causes the formation of new neurons in a critical brain region which does not erases old memories, according to a study conducted by an Indian-origin researchers.

Exercise causes neurogenesis in the hippocampus - key brain region for learning, memory and mood regulation. 

It was surprising when a previous study conducted on mice, revealed that presence of far more neurogenesis in brain seemed to erase memories that were formed before and on removal of extra neurons which enabled mice to remember old memories.

"The mice who exercised had a large number of new neurons but somehow that seemed to break down the old connections, making them forget what they knew," said Ashok K. Shetty, Professor, Texas A and M College of Medicine Department of Molecular and Cellular Medicine in the study, published in the Journal of Neuroscience.

The team decided to replicate the research using rats instead of mice. Rats are considered to be more like humans physiologically, with more-similar neuronal workings. 

The research on rats showed that these animal models reflected no degradation in memories.

The researchers trained the rats to complete a task over four days, followed by several days of memory consolidation by performing the task over and over again. Then, half the trained animal models were put into cages with running wheels for several weeks, while the control group remained sedentary.

The rats who ran further over the course of that time had much greater neurogenesis in their hippocampus and all rats who accessed a wheel had greater neurogenesis than the sedentary group. 

"This is a pretty clear evidence that exercise greatly increases neurogenesis in the hippocampus, which has functional implications. Neurogenesis is important for maintaining normal mood function, as well as for learning and creating new memories," said Maheedhar Kodali, Researcher, Texas A and M University.