Interactions between thalamus and neocortex during TLS. (a). Non linear regression analysis is used to compute (A) the non-linear correlation coefficient h2 and (B) the time delay t from upper signal to lower and asymmetry information (difference between h2 coefficients), and time delays are jointly used to compute the direction index D that characterizes the direction of coupling (C). A large increase in correlation is observed in the first period and the direction index D indicates that the mesial structure (H) is leader. The second period (MS) is characterized by the maintenance of a significant correlation and the D index also indicates that H is leader. The last period is characterized by a re-increase of h2 values. D index values are now negative, indicating that the thalamus (TH) is now the leader structure. (b) Mean (and SD) values of h2 during three ictal periods in patients with TLE. Interactions are calculated between 10 brain regions during intracerebraly recoded seizures (seizure onset, SO; Middle of seizures, MS and end of seizures, ES). Variation of h2 values for all the averaged interactions showing an increase of values culminating at the end of seizuress. *Significant results relative to interictal period. (adapted from ).