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