ECoG history
Selected surface-recording milestones, with hardware and study results kept separate.
ECoG records electrical activity from the cortical surface. This timeline is a selection, not a complete history. It separates published hardware dimensions from what a study showed. An old paper does not establish that a technology failed or stopped developing.
A published cortical-recording milestone
Foerster and Altenburger published "Elektrobiologische Vorgänge an der menschlichen Hirnrinde" in February 1935. The accessible publisher page establishes the title, authors and date, not the electrode geometry. This is a dated publication milestone, not a claim to the first-ever cortical recording.
Active switching cuts the wire count
Viventi and colleagues described a flexible 360-channel array with 300 × 300 µm electrodes at 500 µm spacing, using 720 silicon nanomembrane transistors. The 25 µm array could be folded around a roughly 700 µm silicone insert. The paper reports visual-cortex recordings in ten cats, including placement in the interhemispheric fissure.
196 sites for auditory-cortex mapping
The active micro-ECoG array used 196 sites in a 14 × 14 matrix, 200 × 200 µm contacts and 250 µm center pitch. It needed 29 interface wires. Acute recordings in three rats mapped auditory responses; this was not a chronic clinical result.
Neuron-sized surface contacts
NeuroGrid used 10 × 10 µm sites with 30 µm inter-electrode spacing on a 4 µm film. The paper describes surface recordings of putative single neurons in rats and intraoperative human recordings. Chronic human implantation was not demonstrated.
Implanted surface recording for attempted speech
The speech neuroprosthesis study used a customized PMT array and Blackrock percutaneous connector: 128 electrodes in a 16 × 8 lattice, 4 mm center pitch, a 6.7 × 3.5 cm footprint and 0.51 mm thickness. The participant attempted words from a 50-word vocabulary; the system decoded words and sentences during research sessions, not independent daily use.
What remains outside this timeline
Earlier animal recording work, the full clinical epilepsy-surgery history, commercial grid development and newer arrays need their own source checks. The 1935 record is included without invented specs. No milestone here is labeled a dead end without evidence of that outcome.