Oscillations of electroencephalographic (EEG) signals represent the neural activity which reflecting a mental state or cognitive process that arise from the behavioral task and sensory representations across the mental state activity. Previous studies have shown the relation between event-related EEG and sensory-cognitive representation, and have revealed that categorization of presented objects can be successfully recognized using recorded EEG signals when subjects view objects. In this study, we utilized the recording of EEG signals in conjunction with a multivariate pattern recognition technique with the aim of identifying neural activity associated with conceptual representation based on the presentation of semantic categories of objects. Using multivariate stimulus decoding methods, surprisingly, they demonstrated that object discrimination activity is apparent from the phase pattern of EEG signals across the time in low frequency bands (1-4 Hz), but not by the power of oscillatory brain signals in the same frequency band. In contrast, discrimination accuracy from the power of EEG signals has significantly higher than the performance by the phase of EEG signal in the high frequency band (20-30 Hz). Moreover, our results indicate that how the accuracy of prediction changes between various areas of the brain continuously across the time. In particular, we found that, during the object categorization task, the inter-trial phase coherence (IPC) in low frequency bands is significantly higher than other frequencies in various regions of interests. This measure is associated with decoding pattern across the time. These results suggest that the mechanism underlying conceptual representation can be mediated by the phase of oscillatory neural activity.

Behroozi, M., Daliri, Mr., Shekarchi, B., EEG phase patterns reflect the representation of semantic categories of objects, Medical & Biological Engineering & Computing, 2015