HOME   |   OBJECTIVES   |   RESULTS     |   TEAM

   OBJECTIVES

The main goal of this proposal is to create the first atlas of brain networks associated with clinical effects evoked by HFS. We will accomplish this goal by using a modified stimulation protocol for electrical stimulation mapping of cortical functions in patients with drug-resistant epilepsy. The alternating polarity protocol will enable the use of a frequency-domain analysis that fully resolves the responses from the stimulation artifacts allowing the calculation of effective connectivity metrics for the brain networks responsible for the clinical effects. We broke down the main goal into three intermediate objectives that have scientific value on their own, and which contribute to the realization of the main goal:

Objective 1: Revealing brain networks associated with clinical symptoms in individual patients. This refers to using HFS to evoke the clinical effects without triggering a seizure while recording the stimulation-evoked responses on intracranial electrodes. The innovative element of this approach relates to the fact that the effective network evidenced by electrical stimulation is in this case unambiguously associated with a clinical effect.

Objective 2. Timeline of clinical symptoms. Habitual seizures often exhibit several clinical symptoms which occur in a well-defined sequence, suggesting that the abnormal discharges are recruiting additional brain networks. We will observe the sequence of clinical symptoms during habitual seizures recorded spontaneously during long-term SEEG monitoring, and we will study how the underlying brain networks responsible for each symptom (assessed during objective 1) are interconnected and clustered. We will use machine learning (Naive Bayes classifier) to compute the probability of a given brain structure to be part of the epileptic zone, based on the clinical symptoms observed during the seizure and the likelihood that the brain structure is part of the brain network responsible for that clinical effect. Previous studies have shown that certain brain structures are acting as inputs to the newly engaged brain networks 6, and we believe these inputs may be used as better targets for closed-loop stimulation by clinical implantable devices that use stimulation to disrupt seizures.

Objective 3. Atlas of clinical effects evoked by HFS mapped to brain networks. We will aggregate the patient-level results into an atlas of clinical effects mapped to brain networks http://epi.fizica.unibuc.ro/symnet/. For each brain structure, the atlas will contain likelihood that the structure contributes to the emergence of a certain clinical symptom. Such atlas currently does not exist and will be very helpful for neurologists and neurosurgeons that are planning trajectories for stereoelectroencephalographic (SEEG) explorations in patients with drug-resistant epilepsy.