THE ROLE OF STRIATAL-NETWORK SYNCHRONY IN MOTOR SEMIOLOGY OF FOCAL EPILEPSY

We investigated how oscillatory synchrony between the sensorimotor striatum and distributed
cortico-subcortical networks supports the emergence of motor semiology and secondary
generalization in focal epilepsy. Seventeen patients with drug-resistant focal epilepsy and
intracerebral sampling of the putamen underwent SEEG during seizures expressing
elementary motor signs, automatisms, hyperkinetic behavior, and
evolutions to generalized tonic-clonic seizures. Using bipolar SEEG, functional and directed
connectivity were quantified in delta, theta, alpha, and beta bands between the striatum and
cortical-subcortical regions. Across semiologies, functional connectivity revealed a consistent
beta increase between the striatum and widespread fronto-insulo-temporo-parietal regions,
accompanied by semiology-dependent fluctuations in delta-theta-alpha bands. Directed
connectivity showed a systematic temporal reconfiguration of information flow. Before semiology
onset, the striatum tended to send slow-frequency output toward frontal and
temporal regions, or, in some semiologies, toward fronto-opercular and premotor regions, while
receiving less high-frequency input. After semiology emergence, the directionality shifted toward
enhanced alpha-beta inflow from insular, temporal, and opercular back to the striatum, with
semiology-specific combinations of sources and bands. This pattern suggests that striatal slow-
frequency outflow may facilitate pathological motor functioning, whereas subsequent fast-
frequency cortical feedback sustains and shapes the observed motor behavior. These results
provide intracerebral evidence that the striatum acts as a dynamic hub whose
oscillatory coupling with distributed cortical networks orchestrates the generation of distinct
motor semiologies and their progression to tonic-clonic generalization. The convergence of
beta-band enhancement and delta-theta-alpha reconfigurations across semiologies
supports a model in which pathological exaggeration of cortico-striatal rhythms locks the system
into dysfunctional motor states.