Brief history of electrical cortical stimulation: A journey in time from Volta to Penfield.

OBJECTIVE

To recount the evolution of Electrical Cortical Stimulation (ECS) in localizing brain functions with an emphasis on epilepsy, and a discussion of related instruments and personnel.

DESIGN/METHODS: Literature review through historical archives implementing chain-referral sampling.

RESULTS

There were important milestones leading to the incorporation of ECS into practice: 1. Aldini's (1802) first known stimulation of exposed brain to defend Galvani's views on excitability in the frog-leg experiment against Volta's, ironically by employing the 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 (1873) 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 conscious humans by Bartholow (1874) led to catastrophic outcomes. Horsley (1886) performed first intraoperative stimulation on Jackson's epileptic patient. 5. Advances accelerated in the first-half of the 20th century with Cushing (1909) performing first awake-craniotomy eliciting sensory responses to Penfield's work culminating in standardization of clinical use and generation of detailed maps including the famous sensory-motor homunculi. Parallel advances in instrumentation were made from the Leyden jar (1745) to present customizable current-controlled stimulators.

CONCLUSIONS

ECS is commonly used in neurosurgery for localization of brain functions and is the benchmark for research studies. 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.