DISCUSSION A month of yoga brought about maximum improvement in execution time. The planning time also
Table 1 Effect of yoga on Tower of London Test as compared to that of physical training
improved significantly but in this respect the physical training group was already better at day 1 than the yoga group. That limits the validity of the finding although the improvement in the yoga group is statistically significant. Finally, the number of moves made to complete the task remained essentially unchanged in both groups. If in spite of no appreciable effect on number of moves, the execution time improved dramatically after yoga, it means that yoga improved alertness, as a result of which a wrong move was quickly perceived to be so and a fresh move made without much delay. Early studies correlated poor performance in the Tower of London task with frontal lobe damage (2). More recently it has been shown, using single photon emission computerized tomography (SPECT) that the level of regional cerebral blood flow increased in the left pre-frontal cortex during the Tower of London task in normal persons (3). The improvement in the performance of the Tower of London task in the present study, following a month of yoga training suggests that yoga practice improves frontal lobe function. A positron emission tomography study of regional cerebral metabolic responses showed that ratios of frontal versus occipital responses were significantly higher during meditation in eight meditators (8). A functional magnetic resonance imaging study (9), also showed that the dorsolateral prefrontal cortex is among other regions which are activated during meditation. Hence meditation practice appears to involve the frontal regions. The present study suggests that practice of meditation and other components of yoga for a month improves planning, which is a frontal lobe function. This improvement may be related in some way to the fact that meditation increases frontal lobe activity evidenced by an increase in regional cerebral blood flow.