| Perception is sensation with added complexity | | | | subjects with varying durations of yoga |
| due to factors such as memories and emotions. | | | | training. It was reported in a recent study |
| Yoga practice influences perception in three | | | | on Critical Flicker Fusion Frequency and |
| ways: (1) by increasing perceptual | | | | optical illusion on children who practiced |
| sensitivity, (2) by selectively `shutting | | | | yoga for a shorter duration of 10 days that |
| out' undesirable stimuli, and (3) by changing | | | | there was also a significant improvement |
| distorted perception, which occurs in | | | | following the practice of yoga (9). To |
| schizophrenia. Practicing yoga improved | | | | perceive an optical illusion with minimal |
| auditory and visual perception, by increasing | | | | error and for accurate depth perception the |
| sensitivity to various characteristics of the | | | | spatial component of visual perception is |
| stimuli (e.g., intensity, frequency). Also, | | | | necessary (10). The decrease in the degree of |
| electrophysiological studies using evoked | | | | optical illusion perceived over a short |
| potentials have shown that during yoga | | | | period would be mainly due to cognitive |
| practice the transmission of sensory | | | | judgmental factors, but not retinal or |
| information is facilitated. These studies | | | | cortical factors as generally understood |
| suggest several applications of yoga | | | | (11). The cognitive judgmental factors |
| practice, in activities ranging from aviation | | | | involve the way in which the subject |
| to art. Interestingly, other studies suggest | | | | interprets incoming visual information based |
| that yoga practice can also help to `shut | | | | on experience, hypothesis and strategies of |
| off' undesirable external stimuli, which is | | | | judgment. Hence the training through yoga to |
| possibly due to cortical feedback connections | | | | focus and defocus might have influenced the |
| to the sensory pathway. It is also possible | | | | cognitive judgmental factors of the subjects, |
| that through changes in cognitive factors | | | | to significantly reduce the degree of optical |
| yoga influences perception, so that even | | | | illusion perceived. Critical flicker fusion |
| though the stimulus is `sensed' it is not | | | | frequency (CFF), on the other hand, assesses |
| disturbing. This concept has been studied | | | | the temporal component of perception of a |
| using yoga to help persons with chronic pain | | | | visual stimulus (12). The increase in CFF |
| to willfully ignore it. Finally, preliminary | | | | following yoga could be attributed to the |
| studies have shown that yoga practice may | | | | effects of yoga reducing physiological signs |
| modify distorted perception in conditions | | | | of stress, as CFF was found to be lower |
| such as schizophrenia. Hence, there is | | | | during specific stressors, such as food and |
| sufficient research to support the idea that | | | | water deprivation (13). This showed that both |
| yoga practice influences perception in | | | | spatial and temporal components of visual |
| different ways, with varied applications. | | | | perception are modified following yoga |
| | | | practices. |
| Perception is the process of interpretation, | | | | |
| organization, and elaborating the `raw | | | | Hence the electrophysiological data as well |
| materials' of sensation (1). Sensation | | | | as the visual, neuropsychological studies |
| involves sensory receptors and pathways, | | | | cited above have shown that yoga practice |
| whereas perception is a cognitive process. | | | | improves diverse aspects of auditory and |
| The actual perception of a sensation depends | | | | visual stimuli in normal volunteers. |
| on factors such as what has been learned, | | | | |
| memories, and emotions. It is also important | | | | An interesting difference in auditory |
| to remember that while perception usually | | | | perception (based on AEP-MLRs) were also seen |
| refers to sensory stimuli, this definition | | | | in congenitally blind children (14) and |
| can be extended to include the perception of | | | | adults (15) compared to those with normal |
| situations. | | | | sight. The changes suggested improved |
| | | | auditory perception which could be a |
| Recordings of middle latency auditory evoked | | | | compensatory mechanism of auditory sensation |
| potentials (AEP-MLRs) have shown that the | | | | in the presence of poor vision. |
| practice of ujjayi pranayama modifies the | | | | |
| AEP-MLRs components in two ways. A specific | | | | The effect of yoga has been observed on the |
| component (the Na wave) has reduced latency | | | | perception of situations. Examples of a |
| and increased amplitude during pranayama | | | | change in the way persons perceive situations |
| practice (2). These results suggest that this | | | | was observed in two separate groups of |
| practice facilitates the processing of | | | | subjects. A study on 69 aged persons (above |
| auditory information at mesencephalic and | | | | 60 years of age), staying in an old age home, |
| diencephalic levels. A similar result was | | | | showed that after 6 months of yoga practice |
| also seen during the practice of meditation | | | | there was a reduction in their feelings of |
| on the syllable Om (3), where subjects who | | | | depression, based on the Geriatric Depression |
| had more than ten years of meditation | | | | Scale suggesting a favorable change in the wy |
| experience, showed an increase in the Na wave | | | | they perceived their circumstances (16). |
| amplitude and a decrease in its' latency | | | | Another study on ten patients with breast |
| while mentally repeating (Om). No such effect | | | | cancer (stage 2 and 3), showed reduction in |
| was seen when the same subjects mentally | | | | depression and anxiety (using Beck's |
| repeated `one', during a control session, for | | | | Depression Scale, Spielberger's State and |
| comparison. | | | | Trait Anxiety Inventory), after practicing |
| | | | yoga for 6 months. Hence yoga can probably |
| These electrophysiological data are | | | | have positive effects on both sensory |
| corroborated by neuropsychological studies. | | | | perception and on the way situations or |
| Previous studies on meditation have shown | | | | circumstances are perceived (17). |
| significant changes in perception, attention | | | | |
| and cognition (4). Brown and Engler in 1980 | | | | Finally, there may be more ways of perceiving |
| (5), reported that meditators were found to | | | | the world than we know about. As the renowned |
| be more sensitive to subtle aspects of color | | | | sensory neurophysiologist, Vernon B. |
| and shading of the Rorschach test inkblots, | | | | Mountacastle said: "Each of us lives |
| than they had been before meditation. Two | | | | within.....the prison of his own brain. |
| studies on the Critical Flicker Fusion | | | | Projecting from it are millions of fragile |
| Frequency have shown that perceptual | | | | sensory nerve fibers, in groups uniquely |
| sensitivity is not restricted to subtle | | | | adapted to sample the energetic states of the |
| aspects of the stimulus alone, as detection | | | | world around us: heat, light, force, and |
| of a high frequency flickering stimulus was | | | | chemical composition. That is all we ever |
| found to improve following yoga training | | | | know of it directly; all else is logical |
| (6,7). A study on the degree of a visual | | | | inference" (18). Yoga may allow an advanced |
| geometric illusion, based on Müller-Lyer | | | | practitioner to develop `siddhis' or special |
| lines showed that a combination of focusing | | | | powers, which may hence allow such a person |
| and defocusing yoga visual exercises reduces | | | | to have a different, possibly `expanded' |
| optical illusion more than focusing alone | | | | perception of the world. |
| (8). These studies were conducted on adult | | | | |