'Yoga's effect on brain circuit decoded'

Yoga enhances nerve connections in many of the same brain regions that benefit from aerobic exercise, according to a study reviewing 11 other previous research on Hatha yoga -- which includes body movements, meditation, and breathing.

The researchers, including those from the University of Illinois in the US, said five of the 11 studies engaged individuals with no background in yoga in one or more sessions per week over a period of 10-24 weeks.

In these studies, they said, the brain health of participants were compared at the beginning and at the end of the intervention.

The other six studies measured cognitive differences between individuals who regularly practised yoga and those who didn't, using brain-imaging techniques such as MRI, functional MRI, or single-photon emission computerized tomography, they said.

The current findings, published in the journal Brain Plasticity, revealed some of the brain regions that consistently come up in the eleven studies.

"For example, we see increases in the volume of the hippocampus with yoga practice," Neha Gothe, study co-author from the University of Illinois, said.

According to Gothe, earlier studies looking at the brain effects of aerobic exercise have shown a similar increase in hippocampus size over time.

She said the hippocampus is involved in memory processing and is known to shrink with age.

"It is also the structure that is first affected in dementia and Alzheimer's disease," Gothe added.

The current study also noted that the amygdala -- a brain structure that contributes to emotional regulation -- tends to be larger in yoga practitioners than in people who do not practice yoga.

Other brain regions like the prefrontal cortex, cingulate cortex are also larger, or more efficient in those who regularly practice yoga, the study said.

"The prefrontal cortex, a brain region just behind the forehead, is essential to planning, decision-making, multitasking, thinking about your options and picking the right option," explained study co-author Jessica Damoiseaux from Wayne State University in the US.

The researchers said since yoga is not aerobic in nature, there could be other mechanisms leading to these brain changes.

"So far, we don't have the evidence to identify what those mechanisms are," Gothe said.

She suspects that enhancing emotional regulation is a key to the positive effects yoga has on the brain.

According to Gothe, stress in humans and animals is linked to shrinkage of the hippocampus, and poorer performance on tests of memory.

The researchers believe there is a need for more rigorous, large intervention studies on yoga that engage participants for months, matching yoga groups with active control groups, and measure changes in their brain and performance on cognitive tests.