Abstracts

Rationale: To investigate the evolution of Electrical Cortical Stimulation (ECS) to localize brain functions and to discuss related instruments and personnel. ECS is commonly used in neurosurgery for localization of brain functions and is the benchmark for research studies. Early ECS experiments led to a breakthrough in the understanding of the brain after centuries of controversy over ‘animal-spirit’. Significant advances in electromagnetism were inspired by debates over brain and nerve conductivity in late 18th-century. Methods: Literature review through historical archives and book chapters.  Results: There were important milestones leading to the incorporation of ECS into practice: 1. Aldini’s (1802) first known stimulation of the exposed brain to defend Galvani’s views on excitability in the frog-leg experiment against Volta’s, ironically employing then-newly-invented Voltaic-pile 2. Animal experiments in the 19th-century to study the brain and to optimize the procedure: Rolando (1809) reported on motor induction, Fritsch and Hitzig (ca.1870) introduced the concepts of bipolar and threshold stimulation, and Ferrier (1886) generated reproducible homunculi in animals. 3. Parallel to 2, advances were made based on clinical observations by Bravais, Todd, Jackson, and Broca among others. 4. First, known stimulation in awake humans by Bartholow (1874) led to catastrophic outcomes. Horsley (1886) performed first intraoperative stimulation on Jackson’s epileptic patient. 5. Accelerated advances in the first-half of the 20th century with Cushing (1909) performing first awake-craniotomy eliciting sensory responses to Penfield’s magnificent work culminating in the standardization of the clinical use and generating detailed maps including the famous sensory-motor homunculi.ECS continued to evolve along with other functional methods of localization. Parallel advances in instrumentation were made from the Layden-Jar (1745) to the present customizable current-controlled stimulators. Conclusions: Significant leaps have been made since ECS first used in the 19th century. It evolved to remain the gold standard for localization of human brain functions in the 21st century. Funding: RA wishes to acknowledge research support by the Swebilius Trust, American Epilepsy Society (AES) 412064, the Epilepsy Foundation, CTSA Grant Number 1KL2TR001862-02 from the National Center for Advancing Translational Science (NCATS),