An analysis of dimensional complexity of brain electrical activity during meditation

Meditation is considered to be an altered state of consciousness associated with heightened cognitive functions and transcendental experiences. The neural dynamics in meditative states needs to be explored and an objective analysis of such States is required. Here, the authors investigate the dimensional complexity of EEG signals of two subjects of yogic meditation from a renowned school of yoga. Four channels of EEG have been analysed in terms of compressed spectral array (CSA), running fractal dimension and running attractor dimension during the process of meditation. The CSA yields some interesting features. The running fractal plots show low average fractal dimension values during pre-meditative and post-meditative periods. During meditation there is an increase in the average fractal dimension value. The attractor dimension values also show changes. As the meditation progresses the average attractor dimension rises to a value which is more than that for the premeditative period. It shows a decline during some stages of meditation. The results indicate that the attractor dimension estimation is more effective in depicting the dynamics of the brain in a highly complex state. The attractor dimension analysis of meditative state is compared with that of fractal dimension and CSA. The investigation reveals that chaotic dynamics provides a mechanism for low dimensional control of neuronal oscillations in meditation.