The changes in the peak latency and peak amplitude of P300 auditory event related potentials were studied before and after the practice of cyclic meditation
compared to a comparable period of supine rest in 42 volunteers, from Fz, Cz and Pz electrode sites referenced to linked earlobes. Cyclic meditation consists of alternating cycles of practicing yoga postures interspersed with periods of supine rest (Nagendra & Nagarathna, 1997). The basis for this practice is an idea drawn from the ancient texts (Chinmayananda, 1984). The underlying idea is that for most persons the mental state is routinely somewhere between the extremes of being “inactive” or of being “agitated” and hence to reach a balanced, relaxed state the most suitable technique would be one that combines “awakening” and “calming” practices. In cyclic meditation, the period of practicing yoga postures constitutes the “awakening” practices, whereas periods of supine rest comprise the “calming practices.” An essential part of the practice of cyclic meditation is being aware of sensations arising in the body (Nagendra & Nagarathna, 1997). In the present study, there was reduction in the peak latencies of P300 after cyclic meditation at Fz, Cz and Pz compared to the “pre” values. A similar trend of reduction in P300 peak latencies at Fz, Cz and Pz was also observed after supine rest, compared to the respective “pre” values, although the magnitude of change in each case was less after supine rest compared to after cyclic meditation.
The P300 peak amplitudes after CM were higher at Fz, Cz and Pz sites compared to the “pre” values. In contrast, no significant changes were observed
in the P300 peak amplitudes at Fz, Cz, and Pz after supine rest compared to the respective “pre” state. Previous studies have shown definite changes in the P300 evoked responses following Transcendental meditation (TM). The effect of TM practice on the P300 was studied using a passive auditory listening trial paradigm with variable interstimulus intervals (1–4 s) between identical tone stimuli (Cranson et al., 1990). The subjects were experienced TM meditators, novices, and nonmeditator controls with mean ages of 41, 28 and 20 years, respectively. The P300 latency was shorter for the two meditation groups, with the long-term meditators showing the shortest P300 latency regardless of their age. In another study an auditory oddball task was used with eyes-closed to assess experienced TM meditators at pretest baseline, after 10 min of rest, or after 10 min of TM practice with conditions counterbalanced across subjects (Travis & Miskov, 1994). The P300 latency decreased at Pz after TM practice relative to no change after the rest condition.

Sudarshan Kriya Yoga (SKY) is a meditation system that emphasizes breathing techniques. This technique was used as an intervention for persons with dysthymia compared with an unaffected control group. At three months, the P300 amplitude increased to the levels of the control group in the patient group (Naga Venkatesh Murthy et al., 1998). The P300 amplitude is thought to indicate the amount of brain activity related to incoming information processing and it is more sensitive to the amount of attentive resources engaged during the task (Polich, 2004). The P300 latency reflects the stimulus classification (cognitive) speed, is generally unrelated to the overt response, and is independent of behavioral reaction time. Because P300 latency is an index of stimulus processing rather than response generation, it is used as a motor-free measure of cognitive function. The P300 peak latency has been found to be negatively correlated with mental function in normal subjects: shorter latencies are associated with superior cognitive performance from neuropsychologic tests of attention and immediate
memory.

In the present study, both the peak amplitude and the peak latency of the P300 potentials were changed following cyclic meditation. The reduction in latency was also seen following supine rest, however the magnitude of change was smaller than that after cyclic meditation. These results suggest increased attentional resources, stimulus processing speed and efficiency after cyclic meditation compared to an equal duration of supine rest. Yoga practice has been understood to help in reducing anxiety based on a reduction in levels of psychophysiological arousal (Telles & Srinivas, 1998). In a previous study both cyclic meditation (CM) and supine rest (SR) practiced for the same duration as in the present study, resulted in decreased oxygen consumption, breath rate, and increased breath volume immediately after the practice (Telles et al., 2000). These changes suggested that both practices reduce physiological arousal. However, for all three variables the magnitude of change was greater following CM compared with following SR. This supported the idea that a combination of “stimulating” and “calming” techniques practiced with a background of relaxation and awareness (during CM) may reduce psychophysiological arousal more than SR. Hence, CM may be supposed to be able to reduce anxiety more than SR, which may explain the greater magnitude of change in the performance observed in the present study following CM.

The neuroelectric events that underlie the P300 generation stem from the interaction between the frontal lobe and hippocampal and temporoparietal function (Halgren et al., 1998). The primary neural generators for the P300 components are in the anterior cingulate when new stimuli are processed into working memory with subsequent activation of the hippocampal formation when frontal lobe mechanisms communicate with the temporal or parietal lobe connections (Polich, 1999). In the present study the P300 peak amplitude increased at Fz, Cz and Pz but the increase was maximum at Fz, which indicates greater involvement of frontal areas, which are required for sustained attention. Various neuroimaging studies on meditators have shown increased regional cerebral blood flow in the frontal and prefrontal areas during meditation (Herzog et al., 1990). Hence, the present findings may also support the idea of activation of frontal cortical areas during meditation. In summary, the present study supports the idea that meditation (in this case,“cyclic” meditation) enhances cognitive processes underlying the generation of the P300, though further research is required to understand mechanisms underlying the change.