Ultra high-density, 4096-channel intraoperative neurophysiological brain mapping for functional localization of the human central sulcus

Objective.Intraoperative localization of the central sulcus (CS) using somatosensory evoked-potential (SSEP) phase reversal (PR) is routinely performed with sparse subdural strip electrodes. We evaluated whether a multi-array, 4096-channel surface micro-electrocorticography (μECoG) configuration could provide dense two-dimensional sampling of stimulus-dependent sensorimotor responses within a standard neurosurgical workflow.Approach.Four Precision Neuroscience Layer 7μECoG arrays (1024 platinum electrodes per array on a flexible polyimide substrate, 400μm electrode pitch, ∼1.5 cm²active area per array) were deployed during resection of a right parafalcine meningioma in a 56-year-old male. Two arrays were placed horizontally on the exposed precentral gyrus; two were inserted under the intact dura overlying the postcentral gyrus, using a custom flexible stylet. Somatosensory evoked potentials (SSEPs) were recorded across five contralateral stimulation conditions (median nerve, ulnar nerve, index finger, middle finger, ring finger). Per-electrode SSEP responses were classified without anatomical labels, and spatial organization was quantified across stimulation conditions. Stimulus-locked high-gamma activity, digit-response maps, and signal quality across micro- and macroelectrodes were also evaluated.Main results.Aggregate channel yield was 91.3% (3739/4096) at a 2 MΩ impedance criterion (per-array range 86.7%-97.0%). Per-electrode amplitude maps resolved continuous phase-reversal contours with stimulus-specific spatial structure; reversal latencies were 19, 21, 25, 26, and 25 ms for median, ulnar, index, middle, and ring stimulation respectively. PR occurred within a single array in eight of ten sensory-array recordings, with the phase-reversal pattern varying across stimulation conditions. Digit responses showed measurable spatial differentiation within substantially overlapping response fields. Automated classification of the phase-reversal responses recovered the expected motor and sensory organization, consistent with the standard-of-care intraoperative localization performed in the same case.Significance.The deployment shows that a four-array Layer 7μECoG configuration can be used within a standard neurosurgical exposure and provides dense two-dimensional sampling of stimulus-dependent phase-reversal patterns across the peri-Rolandic recording field. The measured responses were correlated across approximately 3-4 mm of cortex, an order of magnitude coarser than the 400μm electrode pitch, so the contribution demonstrated here is dense spatial sampling rather than submillimeter physiological resolution. Dense sampling rendered the polarity transition as a continuous two-dimensional boundary across the recording field rather than as a reversal between two adjacent contacts. The platform supports future evaluation of high-density surfaceμECoG for intraoperative mapping and chronic brain-computer interface applications.