Human consciousness may be considered consequent to synchronous “humming” of multiple networks which are dynamic. Independent component analysis of resting fMRI is now thought to be an oversimplistic approach to understand consciousness as it time averages these dynamic networks. Using simultaneous fMRI-EEG we aimed at overcoming this limitation by evaluating meditation induced altered consciousness.20 Raja Yoga expert meditators (age: 35± 7.9years), with more than ten years of Raja yoga meditation practice were prospectively recruited for the study. Age, education matched twenty healthy controls were also recruited for the study. We recorded simultaneous EEG-fMRI once in healthy controls, twice in meditators serially (9.24 minute each)- one during resting wakefulness, and another during meditation. rsfMRI was acquired using a 3T scanner (Skyra, Siemens, Erlangen, Germany) using echo Echo-Planar Images (EPI) with following parameters: . 185 volumes, repetition time 3000ms, echo time 35ms, 36 slices, voxel size-3 x 3 x 4mm. We also acquired a T1 waited MPRAGE sequence for anatomical information (with the voxel size 1 x 1 x 1 mm, 192 x 192 x 256 matrix) for better registration and overlay of brain activity. EEG data were recorded using a 32-channel MR-compatible EEG system (Brain Products GmbH, Gilching, Germany). Data was sampled at 5000 Hz and the impedance was kept below 5 kΩ. Total time for each rest EEG recoding was same as rsfMRI recording (9.24 minute), and time locked to each other. We used EEG-Microstates derived from EEG and independent component of resting fMRI to measure resting state networks. We used these EEG microstates as described earlier [3] to analyze the resting state fMRI data at the single subject level. The microstate was considered as explanatory variables/ regressors in the General Linear Model (GLM) design for the analysis of fMRI data. We modeled the input function using the onset time, and the duration of each EEG microstate and convolved it with a gamma HRF. We correlated resting state functional magnetic resonance imaging (rs-fMRI) derived Default Mode Network (DMN) with electroencephalography(EEG) derived Microstates. The DMN correlated EEG-microstate (DMN microstate) was quantified for its duration and occurrence. In second level we used the statistical analysis to understand the group mean effect and between group difference in the form of duration and frequency of occurrence of microstate correlated RSN, activated cluster differences, z-score (correlation value) and T-value of activated clusters [1,2]. EEG derived DMN microstate was topographically similar to the resting state DMN. The average duration and frequency of occurrence of DMN-microstate significantly increased (P<0.001) during meditation induced alteration of consciousness (132.25±11.56ms, 4.02±0.41/s respectviely) compared to rest (118.1±12.35ms, 3.83±0.44/s respectively). These measures also positively correlated with years of meditative experience with DMN duration reflecting the trait effect and DMN occurrence reflecting the state effect of meditation.We investigated changes of default mode network over time using simultaneous EEG-fMRI with an aim to visualize and quantify meditation induced alteration of consciousness. DMN microstate could be accurately identified in all subjects. Topological analysis of DMN microstate could not detect any differences between meditation and rest. However quantitatively there was significant increase in the duration and occurrence of DMN microstate during meditation as compared to rest. DMN microstate duration at rest also correlated significantly with years of meditative practice with difference between rest and meditative state correlating negatively with years of experience, reflecting objectively the trait effect of meditation. In addition we also report for the first time the increasing occurrence of DMN microstate during meditation. This was specific to the meditative state and was independent of the years of experience thus reflecting the state effect unbiased by the trait. Increased duration of microstates during meditation has also been reported in EEG based studies in Chan-meditators and Ch'anMo'chao, or Vipassana meditators (5,6,7).Thus we conclude that fMRI-EEG derived DMN microstate could be a dynamic spatiotemporal correlate of human consciousness and could be used in future studies in understanding the alterations in consciousness induced by sleep, anesthesia and coma.