A new approach to detect and study spatial–temporal intracranial EEG frames

Studies on electroencephalography have revealed pointers for repetitive phase transitions in neocortex at frame rates in the theta and alpha bands. Phase transitions are the first step for frame emergence. Within the frame, brain activity is synchronized and amplitude and phase modulation pattern materialize. The phase patterns have radial symmetry resembling a cone. Cone fitting has been used to detect and study frames in different brain states, including task, awake, sleep and transition into epileptic seizure, revealing signs of disorganization before the seizure episode started. In this paper a new methodology to detect frames is presented. It is faster than the cone fitting previously used to study frames. The results are compared with frames obtained from cone fitting in awake, task, sleep and seizure states. The frames detected by cone fitting and the new method showed high levels of coincidence in time. The disorganization signs observed between pre-ictal period and normal brain state were also observed in the frames detected with the new method. Finally amplitude modulation patterns related to the different behavioral states were clearly distinguishable using the new method frames as time markers for pattern extraction.