Study Tests Whether Lifting Weights Or Running Grows More New Brain Cells

I bet your doctor will NEVER tell you about this. Of course this is in rats so your doctor won't make the leap to thinking this might apply to humans. But then I doubt your doctor will even know about this research.
http://www.spring.org.uk/2016/02/study-tests-whether-lifting-weights-running-grows-new-brain-cells.php

The right type of exercise can triple the number of neurons in the brain’s memory zone.

Sustained aerobic exercise (running) grows new brain cell, but lifting weights does not, a new study concludes.

The research on rats compared three different groups:

• Sustained aerobic exercise
• High-intensity interval training
• Lifting weights

It found that rats who did sustained aerobic exercise for six weeks had developed new brain cells in their hippocampus — the area of the brain vital for memory.
Compared with a control group, they had 2-3 times as many neurons in the hippocampus.
Interval training only had a small effect and lifting weights had no effect on growing new brain cells.

Neurogenesis: How To Grow New Brain Cells

The study’s authors conclude:

“Our results suggest physical exercise promotes AHN [adult hippocampal neurogenesis] most if it is aerobic and sustained, and especially when accompanied by a heightened genetic predisposition for response to physical exercise.”

While this study was carried out in rats, there is plenty of evidence for the positive effects of exercise on neurogenesis (growing new brain cells).