Example of the TAA pattern and the hypothesized mechanism.

(A) Recording of a seizure from a contact of an implanted depth electrode in monopolar representation. Blue background marks the limits of the details in panels B and C. (B) Detail of the TAA pattern at the seizure onset. (C) Time-frequency representation of the signal in panel B (log transformed). The signal is dominated by oscillations around 8 Hz and its higher harmonics. (D) Hypothesized mechanism of the emergence of TAA pattern. During a seizure, cortical sheet (1) is gradually recruited into seizure activity via slowly progressing seizure wavefront (2). Inside the recruited area the abnormal activity is organized by fast traveling waves (3). Implanted sensors record the local field potential generated by nearby located cortical tissue (4), and through this spatial averaging, the rapid onset at the source level is transformed into gradual onset on the sensor level (5).